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+{"text": "Protagonists in the standard SCR reaction have been caught in the act by modulation excitation IR & XAFS spectroscopy. x) by ammonia (NH3). In this work, Cu-SSZ-13 has been studied at 250 \u00b0C under high conversion using a modulation excitation approach and analysed with phase sensitive detection (PSD). While the complementary X-ray absorption near edge structure (XANES) spectroscopy measurements showed that the experiments were performed under cyclic Cu+/Cu2+ redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu\u2013N scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 and Cu\u2013NO3 in the NH3-SCR deNOx mechanism and for the role of [Cu2+(OH\u2013)]+. These results therefore help in building towards a more comprehensive understanding of the reaction mechanism which to date has only been postulated in silico.The small pore zeolite Cu-SSZ-13 is an efficient material for the standard selective catalytic reduction of nitrogen oxides (NO ZSM-5 and beta).3-SCR is complicated and as of yet, not fully rationalised in terms of reaction kinetics, temperature regimes, and perhaps more relevant here, reaction intermediates. A number of plausible mechanisms have been proposed on the basis of spectroscopic and theoretical data ,x species to be converted to N2. Operando spectroscopic studies have proven to be successful at providing insight into both active sites and intermediate species for NH3-SCR.operando conditions with many of the pertinent results outlined in recent reviews.in situ NH3-SCR studies.3, NH4+, NO3\u2013) which renders the detection of short-lived, transient, species difficult. Similarly, for X-ray absorption near edge structure (XANES) spectroscopy, which provides a method to determine the oxidation and coordination state of copper within the sample (e.g. Cu2+/Cu+), it can be challenging to deconvolute signals relevant to the active site from those that originate from other sites in the catalyst that may not be pertinent to the reaction; the large majority of spectroscopic studies are equilibrium-based experiments and many phenomena such as adsorption of reactants, desorption of products and the formation of spectator species occur within similar time frames.3-SCR catalysts, as demonstrated for V-based and Cu-SSZ-13 catalysts using DRIFTS/UV-Vis and XANES, respectively.Ammonia selective catalytic reduction (NHConcentration modulation excitation (ME) represents an approach to enable the detection of dynamic species directly involved in a reaction,3-SCR reaction scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2) and copper bidentate nitrate species (Cu\u2013NO3), while highlighting the regeneration and importance of [Cu2+(OH\u2013)]+ sites in the catalytic process. Ancillary ME XANES experiments confirmed that the measurements were conducted in the presence of the Cu2+/+ redox behaviour in the cycle.Importantly the concentration modulation excitation DRIFTS data augmented with the application of Density Functional Theory (DFT) allowed us to observe the formation of key intermediates including a copper nitrosamine and was connected to heated stainless-steel gas supply lines. The outlet of the cell was connected to a FTIR spectrometer (Bruker Alpha equipped with a 70 mm path length gas cell heated to 150 \u00b0C). The sieved sample was placed in the sample cup of the cell . Prior to the experiments, the sample was dried in situ in 10 vol% O2/N2 (100 ml min\u20131) at 400 \u00b0C for 2 h. The overall flow was kept at 100 ml min\u20131 (100\u2009000 h\u20131) and the temperature at 250 \u00b0C. All DRIFT spectra were obtained by accumulating 10 interferograms at 4 cm\u20131 resolution and 80 kHz scanner velocity (0.9 s per spectrum). During a concentration modulation excitation experiment, solenoid valves were used to automatically switch between gases and were operated by the OPUS software (Bruker). The following pulse sequences were used; 20 cycles of 120 s with 60 s of 500 ppm NO flow on followed by 60 s of NO flow off, into a constant stream of 500 ppm NH3, 10\u2009000 ppm O2 make up N2 . The sets of time-resolved DRIFTS spectra obtained from the modulation experiments at equilibrium conditions spectra were measured using a Bruker Vertex 70 spectrometer equipped with a Praying Mantis mirror unit (Harrick) and a liquid-Nnditions were timnditions . A concem/z 2 (H2), 18 (H2O), 28 , 30 (NO), 32 (O2), 44 (N2O/CO2), and 46 (NO2). Prior to the operando experiments, the calcined catalysts were subjected to high temperature activation in an O2 atmosphere. Samples were heated to 400 \u00b0C at 10 \u00b0C min\u20131 and held at this temperature until no more changes were observed in the XAS spectra, the sample was then allowed to attain the desired temperature. During the ME experiments the zeolite catalysts were exposed to a similar pulse sequence at 250 \u00b0C as outlined above for the DRIFTS experiments, although 10 cycles of 40 s were used in which there was a 20 s NO on pulse followed by 20 s NO off. XANES data processing was performed using IFEFFIT with the Horae package (Athena).Cu K-edge XAS studies were performed at the Swiss Light Source (SLS) at the Paul Scherrer Institute, Switzerland, on the SuperXAS beamline.k-point at the gamma point.\u20131. The converged bulk energies are within 10\u20134 eV. The vibration frequencies were calculated using finite differences to determine the second derivatives. A cube of 8 unit cells of the CHA structure was constructed, which has dimensions of 18.69 \u00c5 \u00d7 18.69 \u00c5 \u00d7 18.69 \u00c5 containing 94 Si atoms, 2 Al atoms and 192 O atoms. The Cu is placed in the 8 ring as a Cu2+ with the framework acting as counter charge due to the acid site hydrogen atoms being removed. In calculations on structures where the Cu2+ has been reduced to Cu+, an additional NH4+ cation has been included to maintain charge neutrality for the model.The VASP code using the Perdew\u2013Burke\u2013Ernzerhof (PBE) functional was employed for the Density Functional Theory simulations. The projector augmented wave (PAW) method with a plane-wave cut-off of 450 eV was used with single 3 coordinated to Cu2+ ions (see 2+(OH\u2013)]+ centres, showing the formation of adsorbed complexes on these particular sites. The region below 2000 cm\u20131 is, in contrast, dominated by alternating positive\u2013negative signals, attributable to the interaction of NH3 molecules, rendering the identification of changes around other features challenging.The 2400 spectra collected during the ME DRIFTS experiments (2+(OH\u2013)]+ species is completely reversed. For clarity, the time-resolved response of several of the relevant features and regions of interest in the ME data have been expanded in 3 measured online to the DRIFTS cell confirms that the ME experiment was performed under actual SCR conditions (The corresponding phase-resolved spectra (nditions .\u20131) that appear in the time-resolved data, such as NH4+ ions formed on the Br\u00f8nsted acid sites and NH3 adsorbed on Cu2+. In addition, bands at 1812 and 2158 cm\u20131 are also observed that were previously attributed to Cu+-NO and NO+ (i.e. formed by either NO2 disproportionation or NO oxidation on Cu2+ sites), respectively. It is important to note, however, that the most intense feature in the phase-resolved spectra is that at 3655 cm\u20131, characteristic of [Cu2+(OH\u2013)]+ sites, presenting a larger variation than those corresponding to either silanol groups and bridging hydroxyls. This observation can be attributed to a response of this species to the variation of gas composition, pointing to an active role of this species in the catalytic mechanism, as is clearly illustrated in 2+(OH\u2013)]+ species to be affected during the entirety of the NO pulse, which is clear evidence for its consumption and subsequent regeneration under SCR conditions.\u20131, which on first sight appears to be due to NH4+ species . Upon closer inspection, this band is clearly red-shifted from the centre of the band due to adsorbed ammonia species, observed in the time-resolved spectra, by approximately 20 cm\u20131. There have been previous studies into the nature and evolution of the broad feature associated with the NH4+ species, notably by Giordanino et al. and Lezcano-Gonzalez et al.4+ ions (i.e. NH4+\u00b7nNH3 associations) and the two bending vibrations of NH4+ ions. Desorption of solvating NH3 molecules with increasing temperatures was seen to lead to a gradual intensity decrease and shift to lower wavenumbers of the component at 1463 cm\u20131, and eventually to the appearance of a single broad band at 1430 cm\u20131 due to un-solvated NH4+ ions attached to the zeolite framework. Lezcano-Gonzalez et al. showed that at 250 \u00b0C, these NH4+ ions slowly react under a flow of NO and O2, concluding that these species are not an intricate part of the NH3-SCR mechanism and more likely remain as a \u2018reservoir\u2019 of NH3.\u20131 band, it seems unlikely that this is due to the consumption and regeneration of NH4+ ions. Nevertheless, to further probe the origin of the band at 1436 cm\u20131, a series of additional time-resolved pulse experiments were conducted.A second interesting feature observed in the phase-resolved data concerns a band centred at 1436 cm\u20131 region the consequent desorption of NH3 . While the features at 1460 and 1436 cm\u20131 share the same response when NO is omitted from the catalyst bed scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2), with an N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching (with some Cu\u2013N component) frequency determined to 1431.2 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 species at 1258 cm\u20131. Upon (re)inspection of the PSD data there is a weak band in the spectra that evolves and is consumed at exactly the same time scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 is a key intermediate postulated in the recent works of Janssens et al. and Paolucci et al.,3-SCR reaction mechanism.To understand the possible origin of the 1436 cm1.2 cm\u20131 . In additime see and phas3 and NO+ (2160 cm\u20131).2+(OH\u2013)]+ or any feature close to the signal observed at 1436 cm\u20131 in the experiments described above, thereby supporting the proposal that Cu\u2013N scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 intermediate species is part of the SCR catalytic cycle. In addition, the results confirm that the various species observed in the NO pulse ME experiment are consumed and regenerated during the SCR reaction and that they are not spectator species or by-products caused by unselective NO oxidation.To validate further the findings of the ME DRIFTS experiment, additional modulation experiments were conducted in the absence of NHand NO+ 20 cm\u20131.16ca. 1606 cm\u20131. Although the exact origin of this band is unclear, its position falls in the range characteristic of nitrate/nitrite and Cu-amine species, also postulated as relevant intermediates in the SCR mechanism.17Another feature that shows a strong response to the ME concentration stimulation (NO) is a band centred at PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching frequencies ca. 1595 cm\u20131 (\u00b130 cm\u20131). Of the three structures, the bidentate Cu\u2013NO3 structure A scale\" fill=\"currentColor\" stroke=\"none\">O stretching frequency closest to that observed in the phase-resolved IR spectrum. The observation of only one IR active stretch mode (E mode) also implies that the D3h symmetry of the NO3\u2013 molecule is preserved on coordination with the Cu ion; the absence of two bands with similar stretching frequencies (\u03bdas/\u03bds modes) suggests the absence of a nitrate species of monodentate geometry (C2v symmetry). We note, however, that there have been many studies performed on Cu-containing zeolites and that a number of possible nitrates/nitrites have been proposed, including some similar to the structures shown here , further suggesting that the accurate assignment of nitrates/nitrites is not trivial.x\u2019 only occurs after the system has moved away from SCR conditions (i.e. after NH3 flow is switched off).i.e. different temperatures and conversion regimes, but also of their fraction being too short lived for XAS to be detected compared to all other species and thus of the different sensitivity of the two spectroscopic techniques. This observation allows us to conclude that there is probably a difference between the nitrates that play a role in the catalytic cycle as seen here, compared with those that form in the absence of NH3 (i.e. those that form slowly during NO oxidation).Examination of possible stable species predicted using DFT suggests a few candidate mono, bidentate nitrate and nitrite species with typical NA see ESI possesse\u20131, which can be assigned to the stretching modes of both NH4+ ions and adsorbed NH3 on Cu2+, respectively, together with a broad feature at 2156 cm\u20131 due to NO+.\u20131 are also seen to be present, which have previously been assigned to hydrogen-bonded coordination spheres around NH4+ (2800 cm\u20131) and H3O+ ions (3025 cm\u20131).3 before the SCR reaction begins with the loss of at least one NH3 ligand around the Cu ions necessary for the SCR reaction to take place. The absence of the more commonly observed, yet weaker NH3/NH4+ bending modes in the phase-resolved data suggests that these species undergo only minor modulation during the SCR reaction, which is largely due to their playing an indirect role in the reaction; solvating NH3 and NH4+ species are proposed to provide a reservoir of ammonia for the reaction although as has been shown previously for this catalyst, NH4+ ions are not particularly reactive.17Additional weak bands are seen in the phase-resolved data of et al. ]+ and is followed by the formation of Cu\u2013N scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2.3 followed by NO+ (2160 cm\u20131) from the disproportionation of NO2, is observed at its maximum intensity with roughly the same phase angle as those associated with Cu\u2013NH3 stretch (3182 cm\u20131) which suggests a complex is formed containing both Cu\u2013NH3 and NO2 towards the end of the cycle. Indeed, if we normalise the phase angle to the start of the catalytic cycle (i.e. presence of [Cu2+(OH\u2013)]+ as shown in The intermediate species seen in this study have previously been proposed as protagonists in the reaction mechanism proposed by Janssens al. see .10 Howev2+, followed by an evolving feature with time attributed to a 1s\u20134p dipole transition at 8982 eV due Cu+.2+ and Cu+ species in the time-resolved data much more clearly. Significantly, the maximum amplitude of the Cu+ feature correlates exactly with the minimum amplitude for the Cu2+ feature. This experimental observation is a clear indication of the accompanying Cu2+/Cu+ redox process occurring during the SCR catalytic cycle in these experiments ]+ is consumed/reduced to form the transient Cu\u2013N scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 species. We note that the NO stretch of this particular species is red-shifted by \u223c400 cm\u20131 with respect to where stretches are typically found for heteronuclear N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOx species and which, we argue, is caused by electron density removal from the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bond brought about by the formation of an L-type ligand interaction between Cu and N(O) leading to a distribution of 7 electrons over 4 bonds. It is interesting to note that we do not see the initial Cu\u2013NH3 or Cu\u2013NO(OH) interactions suggesting that although these must take place they are simply too fast to be observed in this experiment. Indeed, it is well known that Cu+/2+\u2013NH3 and Cu+\u2013NO interactions occur readily, which for NH3 even leads to reaction inhibition at low temperatures.\u20131, which could be tentatively attributed to nitrate-type species, and subsequently the appearance of NO+ (which has been proposed to be formed through the disproportionation of NO2) suggests an important role in the catalytic cycle also for nitrates and nitrites, particularly for completing the Cu redox cycle as has been previously postulated for both NH3-SCR in Cu zeolites and observed in hydrogen-promoted hydrocarbon SCR on silver\u2013alumina catalysts.operando DRIFTS experiments as the spectra are dominated by species originating from NH3. Interestingly the identification of these intermediates indicates a pathway through which gas phase NO2 can be produced in the cycle to circumvent the need to co-feed it to effect fast SCR as is typical in Fe-based systems.2+/Cu+ redox cycle operating at the same frequency as the concentration pulse. It is interesting to note that previous experiments under steady-state, high-temperature (i.e. >250 \u00b0C) operational conditions contain no evidence for Cu reduction although it is to be expected that this must occur.et al., although we do note that such species appear in a number of proposed cycles to date.The concentration ME experiments have provided key mechanistic details from both DRIFTS and XANES experiments. The DRIFTS data suggest that the catalytic cycle follows a reaction pathway whereby [Cu3-SCR process on copper containing zeolites. The ME DRIFTS and XANES data reveal the start of the reaction to involve [Cu2+(OH\u2013)]+, highlighting two key intermediates, Cu\u2013N scale\" fill=\"currentColor\" stroke=\"none\">O)\u2013NH2 and Cu\u2013NO3, that would be very difficult to observe using standard operando DRIFTS measurements. Using the mechanism in 2), and with the latter species, show how the Cu ion reoxidation occurs. Furthermore, within this mechanism, these species also help to rationalise how NO2 is produced circumventing the necessity to utilise additional NO2 for effective NH3-SCR behaviour. These results, moreover, are in line with predictions from theory, which helps benchmark the ME approach for obtaining potential mechanistic insight importantly obtained under more relevant conditions.10Cu-SSZ-13 has been studied by concentration ME using both DRIFTS and XANES. The data obtained have provided mechanistic insight into the NHi.e. Cu2+(NH3)3(NO3)).x applications, perhaps using cationic components that could be more active or at least more environmentally benign or at risk than copper.Despite the new insight obtained, we observe that the ME technique is not able to allow us to rationalise fully all the steps in the catalytic mechanism at this temperature or to discriminate definitively between active and spectator species that may evolve at the same rate as the dose response. It may be that better resolution regarding these steps could be realised by performing experiments at lower conversions and/or at lower temperatures. We note, furthermore, that the temperature employed for this study is also unable to discriminate between the low and high temperature mechanism because of the Cu loading, but as it was performed at 250 \u00b0C, these results are likely to be more pertinent to a high temperature mechanism; indeed some of the intermediates observed here are different from those recently reported at much lower temperatures (There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "A series of molybdenum pincer complexes has been shown for the first time to be active in the catalytic hydrogenation of amides. Mo-1a proved to be particularly well suited for the selective C\u2013N hydrogenolysis of N-methylated formanilides. Notably, high chemoselectivity was observed in the presence of certain reducible groups including even other amides. The general catalytic performance as well as selectivity issues could be rationalized taking an anionic Mo(0) as the active species. The interplay between the amide C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reduction and the catalyst poisoning by primary amides accounts for the selective hydrogenation of N-methylated formanilides. The catalyst resting state was found to be a Mo\u2013alkoxo complex formed by reaction with the alcohol product. This species plays two opposed roles \u2013 it facilitates the protolytic cleavage of the C\u2013N bond but it encumbers the activation of hydrogen.A series of molybdenum pincer complexes has been shown for the first time to be active in the catalytic hydrogenation of amides. Among the tested catalysts, This is in sharp contrast with the results obtained with Fe pincer complexes, in which formanilide derivatives give the highest conversion.6a) and simple benzanilide (7a) were employed and results comparable to formanilide (4a) were obtained. Likewise, only low conversions and yields were obtained in the case of N-iPr- (4b) and N-allylformanilide (4c), respectively. Surprisingly, when N-allylformanilide was tested as substrate, the formation of N-allylaniline was only observed in traces. The main product was identified to be aniline, thus hinting at a deallylation pathway that additionally takes place to the envisaged hydrogenolysis. In contrast, N,N-diphenylformanilide (4d) was reduced smoothly and N,N-diphenylamine was isolated in excellent yield. Next, the hydrogenation of N-methylacetanilide (5) and the more activated 2,2,2-N-methyl-trifluoroacetanilide (6b), respectively, were attempted. In either case, only poor conversions were determined demonstrating the high preference of this complex for specific formanilides. This was further supported by the low reactivity of N-methylbenzanilide (7b) and some aliphatic formamides with extremely high preference. Notably, the reaction still proceeded with 80% conversion with respect to N-methylformanilide (1a). To further highlight the scope of our system, we designed model substrate 9 combining two amide functionalities in one structure. After 24 h reaction, the intended hydrogenolysis of the formamide moiety in 9 had occurred smoothly and the target molecule 10 was isolated in a very high yield (92%). Notably, no cleavage of the benzamide was observed.Based on these observations, we were curious to demonstrate selective formamide reduction in the presence of other amide moieties. In a proof of concept experiment, the hydrogenation of the benchmark amide in the presence of benzamide We believe these results could pave the way towards new and selective deprotection strategies in organic synthesis mediated by this base metal PNP pincer complex.Mo-1a and its performance with different amides, DFT calculations and supporting experiments were conducted. Mo-1a with NaBHEt3 resulted in rapid hydrogen evolution. The nature of the gas was determined in a scale up experiment (100 \u03bcmol of Mo-1a) using GC-analysis. This observation prompted us to assume that the obtained reaction product was likely to be a pincer amido species such as Mo-3, in which Mo(i) has been reduced to Mo(0). This conclusion was further supported by HR-ESI mass spectrometry of the corresponding reaction mixture. When the distinct reactivity of the catalyst towards formanilide was studied, we isolated Mo-4 in form of colorless needles from the reaction mixture center. This is also consistent with the EPR-silent nature of the product formed in the activation of Mo-1a by NaBHEt3.Notably, the crystal structure of Mo-4 featuresMo-4 suggests that the Mo(0)-complexes Mo-3 and Mo-5, shown in Scheme 5, are presumably the main catalytic intermediates. Similar species have been proposed for the isoelectronic Fe(ii)-complexes Fe-2, Fe-3 and the Mn(i)-complex Mn-2 scale\" fill=\"currentColor\" stroke=\"none\">O reduction, C\u2013N bond protonolysis of the formed hemiaminal, and aldehyde C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reduction. These steps were computed for N-methylformanilide and the energy profiles for the preferred pathways are given in As represented in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO hydrogenation by Mo-5 consists of the hydride transfer from Mo to the amide carbonyl group (Mo-ts-6-7), followed by proton transfer from the ligand nitrogen to the amide oxygen (Mo-ts-7-8). This pathway was computed for formanilide . Interestingly, these energies are lower than those reported by us for the analogous Fe catalyst with formanilide . An increase of less than 1 kcal mol\u20131 is observed by changing the substrate to N-methylacetanilide (Me\u2013NMeMo-ts-C).The mechanism for the C\u2013N bond cleavage from the formed hemiaminal was alsots-CH\u2013NH .15 With N-methylformanilide vs. 20% Conv. in N-methylacetanilide). In addition, the lower energy barriers obtained with Mo compared to Fe are inconsistent with the higher H2 pressure and time required to accomplish amide hydrogenation with Mo-1a compared to Fe-3.14The similar energy barriers obtained with these substrates did not account for the large differences in yield observed experimentally (99% Conv. in Mo-3 with methanol leading to the Mo-methoxy intermediate Mo-9a (Mo-ts-3-9a), has a low energy barrier and is highly exergonic . The formation of related M-methoxy species have been observed for similar Fe, Ru, Os and Mn PNP-pincer complexes.N-protonation of the hemiaminal intermediate (Mo-ts-11-9a). The highest energy of this process is 10.8 kcal mol\u20131, which corresponds to the zwitterion hemiaminal intermediate interacting with the methoxide\u2013Mo complex (Mo-11). This energy is lower than the energy barrier for the hydride transfer , indicating that the C\u2013N bond cleavage is not the rate limiting step once MeOH is formed than with MeOH increasing the global energy barrier for the hydride transfer from 10.6 to 26.8 kcal mol\u20131 with formanilide. This energy may increase to 31.4 kcal mol\u20131 by reaction with BEt3 (Mo-4). In contrast, with N-methylformanilide, the only penalty to pay is the addition of MeOH. Therefore, the energy barrier for the hydride transfer increases from 13.1 to 22.9 kcal mol\u20131, which is lower than the barrier for formanilide, consistent with the larger conversion obtained with N-methylformanilide. In the case of N-methylacetanilide, the addition of ethanol instead of methanol is expected. The higher stability of the ethoxide complex Mo-9b compared to Mo-9a by ca. 2 kcal mol\u20131 by acting as a proton-shuttle with a global energy barrier of 23.0 kcal mol\u20131. Similar mechanisms have been proposed with Ru\u2013N and Fe\u2013N complexes scale\" fill=\"currentColor\" stroke=\"none\">O reduction (blue cycle). This reaction yields amine and formaldehyde, which is reduced to alcohol by the catalyst Mo-5 in a subsequent reaction (in red). In the presence of alcohol, a Mo-alkoxo intermediate is formed, Mo-9a. This species, which becomes the catalyst resting state, is involved in the hemiaminal C\u2013N bond cleavage. Finally, the catalyst recovery takes place by the displacement of alcohol by H2. The nature of the catalyst resting state may change with secondary amides, which reacts with the catalyst forming an adduct that hampers the reaction.The results from the computational study can be summarized in the catalytic cycle represented in 3, NaHBEt3, and KHBEt3. Carrying out the benchmark reaction at 80 \u00b0C, 5 mol% of the alkali metal hydrides were added to activate Mo-1a. It could be shown, that for NaBHEt3 and KBHEt3 similar conversions of N-methylformanilide (1a) and yields of 2a were obtained. However, when LiBHEt3 was used, only 10% conversion of 1a and 9% yield of N-methylaniline 2a was obtained. These results were in agreement with the trends on the energy barriers obtained for the amide C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reduction step, which are 22.9, 23.0 and 28.8 kcal mol\u20131 with Na+, K+ and Li+, respectively, taking Mo-9a as energy reference. The stronger electrostatic interaction of Li+ with the methoxide intermediate (LiMo-9a), accounts for the highest energy barrier predicted for this system active species, the role of the counter-cation in this reaction was explored computational and experimentally by using LiHBEtm see ESI.N-methylformanilide (1a) and 93% product yield were obtained. However, the addition of 200 mol% resulted in a sharp decrease in conversion and yield . Thus, it was concluded that ethanol has a detrimental effect on the performance of the catalytic system. Notably, these trends were reproduced with a microkinetic model based on the general mechanism represented in Next, the role of the alcohol was explored by adding different amounts of ethanol to the benchmark system. In the presence of 50 mol% of EtOH, 96% conversion of N-Alkylated and N-arylated formamides can be hydrogenated to the corresponding products in good to high yields. Applying complex Mo-1a high selectivity for the hydrogenation of formamides was observed in the presence of other reducible groups. These results pave the way for potential applications of this type of complexes in synthetic methodologies.Well-defined molybdenum\u2013PNP pincer complexes have been used for the first time in the hydrogenation of a range of amides to the corresponding alcohols and amines. Mo-5) reduces the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group of the amide through low-energy barriers, compared to Fe-based systems. However, the alcohol product and secondary amides react with the catalyst forming stable adducts encumbering catalyst recovery and increasing the overall barrier for the reduction of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group. These results suggest that further catalyst design should focus on preventing the formation of these adducts, while keeping the high hydricity of the complex.The DFT study shows that the active Mo(0) species (All hydrogenation reactions were set up under Ar in a 300 mL autoclave (PARR Instrument Company). In order to avoid unspecific reductions, all catalytic experiments were carried out in 4 mL glass vials, which were set up in an alloy plate and placed inside the autoclave.Mo-1a . Toluene (2 mL) was added and the corresponding brown suspension was treated with NaBHEt3 . The reaction mixture was stirred for 10 minutes and the corresponding substrate was subsequently added. Afterwards, the vial was capped and transferred into an autoclave. Once sealed, the autoclave was purged three times with 10 bar of hydrogen, then pressurized to the desired hydrogen pressure (50 bar), and placed into an aluminum block that was preheated to the desired temperature (100 \u00b0C). After 24 h, the autoclave was cooled in an ice bath and the remaining gas was released carefully. The solution was subsequently diluted with ethyl acetate and filtered through a small pad of Celite (1 cm in a Pasteur pipette). The Celite was washed with methanol (2 mL) and the combined filtrates were subsequently evaporated to dryness. The remaining residue was purified by column chromatography . In the case of substrate 7, the purified product was dissolved in 5 mL of Et2O and subsequently treated with 1 mL of HCl (2 M in Et2O). The reddish precipitate was filtered off, washed three times with 5 mL of Et2O and finally dried in vacuo. For the characterization of the products of the catalysis, see ESI.In a glove box, a 4 mL glass vial containing a stirring bar was charged with complex + cation was evaluated in some of the intermediates, and the preferred position is represented in figures and schemes of the manuscript (see ESIMo-1a and Mo-4 were consistent with a doublet and singlet ground state, respectively (see ESIp = 50 atm and T = 373.15 K. The energy of the optimized geometries was refined by single point calculations with triple-z quality basis sets, including the LANL2TZhttps://iochem-bd.bsc.es/browse/handle/100/193698.DFT calculations were carried out with Gaussian 09\u2009t see ESI. The geoy see ESI. VibratiThere are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Antibodies conjugated to a photoactive transition metal carbonyl complex afford antigen-directed delivery of cytotoxic carbon monoxide to ovarian cancer cells. in vitro. The results described here provide the first example of an \u201cimmunoCORM\u201d, a proof-of-the-concept antibody-drug conjugate that delivers a gaseous molecule as a warhead to ovarian cancer.Carbon monoxide (CO)-releasing antibody conjugates were synthesized utilizing a photoactivatable CO-releasing molecule (photoCORM) and mouse monoclonal antibodies linked by a biotin-streptavidin system. Different monoclonal antibodies raised against different surface-expressed antigens that are implicated in ovarian cancer afforded a family of antibody-photoCORM conjugates (Ab-photoCORMs). In an immunosorbent/cell viability assay, Ab-photoCORMs accumulated onto ovarian cancer cells expressing the target antigens, delivering cytotoxic doses of CO Carbon monoxide (CO), while long recognized as a toxic gas, is an endogenously produced gasotransmitter that regulates immune/inflammatory processes and vascular tone through reactions with heme-containing proteins.2The challenge of delivering efficacious concentrations of CO to a target tissue has been approached by our group and others by synthesizing CO-releasing molecules (CORMs) with properties necessary for a potential therapeutic, including water solubility,versus non-targeted tissues. With this in mind, we sought to conjugate a photoCORM to a monoclonal antibody with the goal of improving target specificity of CO-release. Antibody-drug conjugates (ADCs) are fast emerging as an effective strategy for anticancer therapies. In most cases small molecule drugs are combined with monoclonal antibodies to achieve high selectivity.i.e. the warhead) to monoclonal antibodies using a biotin-streptavidin linker is a novel, currently unexplored and potentially effective strategy that could be employed for the controlled delivery of CO to specific tissues.Although a number of CORMs and photoCORMs has been developed in recent years,Herein we report the successful conjugation of a biotinylated-photoCORM to streptavidin-conjugated mouse monoclonal immunoglobulin G (IgG) antibodies to isolate Ab-photoCORMs for the controlled delivery of CO to ovarian cancer cell cultures with high specificity. Utilizing different monoclonal antibodies, a family of Ab-photoCORMs was synthesized with the goal of localizing and delivering cytotoxic levels of CO to ovarian cancer cells expressing different tumor-specific surface antigens. To the best of our knowledge, this communication is the first report of an antibody-drug conjugate in which the drug is a gaseous molecule, namely CO.3(phen)(4-pyAl)](CF3SO3) as the photoactivatable CO donor. Biotinylation of this photoCORM (1) was achieved through reaction with biotin-hydrazide in trifluoroethanol at room temperature (Scheme S11 was confirmed by electrospray ionization Fourier Transform mass spectrometry (ESI FTMS); (M+) m/z = 666.13539 scale\" fill=\"currentColor\" stroke=\"none\">OC bands at 2039 and 1939 cm\u20131, characteristic of the manganese tricarbonyl moiety, and one \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC band at 1685 cm\u20131 derived from the biotin unit exhibited a broad absorbance band in the visible region between 320 and 450 nm , broadband, visible light Scheme S1. The com) Fig. S1, and 1H ctrum ESI. The inft Fig. S2. Electrom Fig. S3. Exposura Fig. S4 arising S Fig. S4. Complext Fig. S5. Furthery Fig. S6.1 upon illumination with visible light, significantly reduced cell viability in two ovarian cancer cell lines OVCAR-5 and SKOV-3 (ED50 = 48 and 25 \u00b5M respectively) assayed 24 h post-treatment and stability of the streptavidin-biotin interaction.2) for cellular studies.A streptavidin-biotin strategy was used to link Complex 2 with excess Complex 1 afforded the antibody-photoCORM conjugate (Ab-photoCORM) through a streptavidin-biotin interaction (1 by size-exclusion chromatography (Reaction of Complex eraction ESI\u2020). . 2 with tography .1 (M+) incorporated into the Ab-photoCORM was observed in the full MS scan was also synthesized for application in cell viability experiments in order to account for any non-CO-mediated effects of the antigen-specific Ab-photoCORMs.A family of Ab-photoCORM conjugates was synthesized using th\u20131 of Ab-photoCORMs for 60 min in the dark and then washed 3 times with 1x PBS to remove any non-specific association. Next fresh media was added to the cells and they were exposed to low-power visible light for 30 min for CO photorelease. After an incubation period of 24 h, cell viability was assessed by cellular reduction of MTT. The viability study clearly demonstrated that treatment of OVCAR-5 and SKOV-3 cells with Ab-photoCORM conjugates recognizing epitopes expressed in those ovarian cancer cell lines delivered cytotoxic levels of CO and dramatically decreased cell viability conjugated to an antibody also requires that drug release is not dependent on linker cleavage or through complete degradation of the antibody within the tumor cell. The cleavable linkers impart small molecule drug ADCs with poor pharmacokinetics and circulation instability.Conventional ADCs require a number of specific properties in order to exhibit sufficient potency and stability. As one of the main mechanisms of drug resistance is ADC eflux,The authors declare no conflict of interest.Supplementary informationClick here for additional data file."}
+{"text": "An Fe-based heterogeneous catalyst allows for the synthesis of cyclopropanes via a carbene transfer reaction, a transformation usually belonging to the homogeneous domain. in situ-generated iron/phenanthroline complexes in the presence of a carbonaceous material leads to specific supported nanosized iron particles, which are effective catalysts for carbene transfer reactions. Using olefins as substrates, cyclopropanes are obtained in high yields and moderate diastereoselectivities. The developed protocol is scalable and the activity of the recycled catalyst after deactivation can be effectively restored using an oxidative reactivation protocol under mild conditions.The first examples of heterogeneous Fe-catalysed cyclopropanation reactions are presented. Pyrolysis of Similarly, substrates with electron-donating groups (1f\u20131g) afforded the corresponding cyclopropanes in very high yields. Also halogen-containing substrates were well tolerated, maintaining intact the C\u2013X bond, which can allow further functionalization. To our surprise, pentafluoro styrene (1l) as an example of an electron-poor substrate afforded the corresponding product in a good yield. Notably, more challenging aliphatic substrates such as 1-octene (1t) and \u03b2-pinene (1v) gave the products in satisfactory yields. Using vinyl cyclohexene (1u) the cyclopropanation reaction occurred regioselectively on the terminal olefinic bond maintaining intact the internal one. The selectivity for the terminal double bond in 1u is explained by the lack of activity of the catalyst in the case of internal olefins .Under the optimized conditions, the scope of the diazo compound was also examined . Mono-suth run (D.1 in ca. 0.1%) loss of iron from the catalyst, so this cannot be the reason for deactivation.In order to demonstrate the practical utility of this protocol, the scalability and recyclability of the system were studied. The model reaction was successfully scaled-up to 15-fold without significant variations of yield and diasteroisomeric ratio compared to the small-scale run. Regarding the recyclability, a significant decrease of the activity was observed after the 42O2, the initial catalyst activity was restored (R.2 in e.g. fouling or poisoning).In order to make the whole process both efficient and effective, two routes of re-activation of the spent catalyst were explored. The material obtained after 5 runs (Fe/Phen@C-800_S) was thermally treated under an inert atmosphere R.1 in . Howeverd R.2 in ! The read R.2 in , cycle 7n+/H2O2 system (known as Fenton's reagent) is also effective in these processes thanks to the generated HO\u02d9 radicals.2O2 and related Fenton-like reactions are responsible for the removal of the oligomers/polymers from the spent catalyst.Note that most oxidative reactivation processes are based on the use of air at high temperatures, but such a treatment would result in the complete burning of the carbon support of our catalyst. Hydrogen peroxide has been reported as a milder alternative in a few cases.x centers, pyrrolic-N, and graphitic-N, respectively. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC/C\u2013H (284.8 eV), C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN or C\u2013O (approximately at 285 eV), and C\u2013N or C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (285\u2013291 eV) functionalities can be detected.3/2 region showed four pairs of peaks which can be attributed to various Fe states. Peaks at around 708 eV, 711 eV, and 714 eV in the region correspond to Fe(0), Fe(ii) and Fe(iii), respectively.x bonds which is in agreement with the previous results from N 1s spectra.43To further elucidate the reason for the declined activity, the fresh, spent and regenerated catalysts were characterized by X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). XPS N 1s analysis showed common peaks at around 399 eV, 400 eV, and 401 eV for all the materials in the material. The spent catalyst (Fe/Phen@C-800_S) showed similar structures: still defined Fe-based NPs enveloped in carbon shells and dispersed iron clusters can be clearly observed (Finally, the interpretation of the O 1s region is not trivial because of the large amount of oxygen functionalities both derived from oxygen groups present in the carbonaceous matrixobserved . Finallyobserved .2O2 treatment, rather than by a structural change of the catalyst itself.The general morphology and distribution of Fe, N, O and C remained similar between the three different states of the catalyst as shown by the STEM data. Combined with the small changes in the electronic structure revealed by XPS, the data are consistent with the deactivation of the catalyst being due to fouling, which is removed by the HIn conclusion, here we report the first iron-based heterogeneous catalyst for cyclopropanation reactions. While in the past, this class of non-noble metal catalysts was generally employed for reduction or oxidation reactions, they are indeed effective catalysts also for carbene transfer reactions. The developed protocol allows obtaining several cyclopropanes from aromatic and aliphatic olefins and different diazo compounds in a practical and efficient manner. The heterogeneous nature of the catalyst and its robustness make it also an ideal candidate for flow chemistry applications. The deactivation of the catalyst has also been studied and an oxidative regeneration protocol was effectively developed, which may be of more general use even for other reactions.There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The Canadian Assessment of Physical Literacy (CAPL) is the first comprehensive protocol designed to assess a child\u2019s level of physical literacy. Current approaches to analyzing CAPL-2 raw data are tedious, inefficient, and/or can lead to computation errors. In this paper we introduce the capl R package (open source), designed to compute and visualize CAPL-2 scores and interpretations from raw data. The capl package takes advantage of the R environment to provide users with a fast, efficient, and reliable approach to analyzing their CAPL-2 raw data and a \u201cquiet\u201d user experience, whereby \u201cnoisy\u201d error messages are suppressed via validation. We begin by discussing several preparatory steps that are required prior to using the capl package. These steps include preparing, formatting, and importing CAPL-2 raw data. We then use demo data to show that computing the CAPL-2 scores and interpretations is as simple as executing one line of code. This one line of code uses the main function in the capl package (get_capl) to compute 40 variables within a matter of seconds. Next, we showcase the helper functions that are called within the main function to compute individual variables and scores for each test element within the four domains as well as an overall physical literacy score. Finally, we show how to visualize CAPL-2 results using the ggplot2 R package. Physical literacy is defined as \u201cthe motivation, confidence, physical competence, knowledge, and understanding to value and take responsibility for engagement in physical activities for life\u201d . It has The Canadian Assessment of Physical Literacy (CAPL) was the first comprehensive protocol designed to assess a broad spectrum of skills and abilities that contribute to and characterize the physical literacy level of a participating child . The CAPbmcpublichealth.biomedcentral.com/articles/supplements/volume-18-supplement-2). Data in each paper included approximately 10,000 children aged 8 to 12 years, recruited from several provinces across Canada. The CAPL-2 manual and materials have been translated in five languages and have been used internationally \"age\"\u00a0\u00a0\u00a0\u00a0\"gender\"\u00a0\u00a0\u00a0\u00a0\"pacer_lap_distance\"#> [4] \"pacer_laps\"\u00a0\u00a0\u00a0\u00a0\"plank_time\"\u00a0\u00a0\u00a0\u00a0\"camsa_skill_score1\"#> [7] \"camsa_time1\"\u00a0\u00a0\u00a0\u00a0\"camsa_skill_score2\"\u00a0\u00a0\u00a0\u00a0\"camsa_time2\"#> [10] \"steps1\"\u00a0\u00a0\u00a0\u00a0\"time_on1\"\u00a0\u00a0\u00a0\u00a0\"time_off1\"#> [13] \"non_wear_time1\"\u00a0\u00a0\u00a0\u00a0\"steps2\"\u00a0\u00a0\u00a0\u00a0\"time_on2\"#> [16] \"time_off2\"\u00a0\u00a0\u00a0\u00a0\"non_wear_time2\"\u00a0\u00a0\u00a0\u00a0\"steps3\"#> [19] \"time_on3\"\u00a0\u00a0\u00a0\u00a0\"time_off3\"\u00a0\u00a0\u00a0\u00a0\"non_wear_time3\"#> [22] \"steps4\"\u00a0\u00a0\u00a0\u00a0\"time_on4\"\u00a0\u00a0\u00a0\u00a0\"time_off4\"#> [25] \"non_wear_time4\"\u00a0\u00a0\u00a0\u00a0\"steps5\"\u00a0\u00a0\u00a0\u00a0\"time_on5\"#> [28] \"time_off5\"\u00a0\u00a0\u00a0\u00a0\"non_wear_time5\"\u00a0\u00a0\u00a0\u00a0\"steps6\"#> [31] \"time_on6\"\u00a0\u00a0\u00a0\u00a0\"time_off6\"\u00a0\u00a0\u00a0\u00a0\"non_wear_time6\"#> [34] \"steps7\"\u00a0\u00a0\u00a0\u00a0\"time_on7\"\u00a0\u00a0\u00a0\u00a0\"time_off7\"#> [37] \"non_wear_time7\"\u00a0\u00a0\u00a0\u00a0\"self_report_pa\"\u00a0\u00a0\u00a0\u00a0\"csappa1\"#> [40] \"csappa2\"\u00a0\u00a0\u00a0\u00a0\"csappa3\"\u00a0\u00a0\u00a0\u00a0\"csappa4\"#> [43] \"csappa5\"\u00a0\u00a0\u00a0\u00a0\"csappa6\"\u00a0\u00a0\u00a0\u00a0\"why_active1\"#> [46] \"why_active2\"\u00a0\u00a0\u00a0\u00a0\"why_active3\"\u00a0\u00a0\u00a0\u00a0\"feelings_about_pa1\"#> [49] \"feelings_about_pa2\"\u00a0\u00a0\u00a0\u00a0\"feelings_about_pa3\"\u00a0\u00a0\u00a0\u00a0\"pa_guideline\"#> [52] \"crf_means\"\u00a0\u00a0\u00a0\u00a0\"ms_means\"\u00a0\u00a0\u00a0\u00a0\"sports_skill\"#> [55] \"pa_is\"\u00a0\u00a0\u00a0\u00a0\"pa_is_also\"\u00a0\u00a0\u00a0\u00a0\"improve\"#> [58] \"increase\"\u00a0\u00a0\u00a0\u00a0\"when_cooling_down\"\u00a0\u00a0\u00a0\u00a0\"heart_rate\"capl package is also equipped with the get_capl_demo_data function. This function allows users to randomly generate demo raw data and takes one parameter, n (set to 500 by default). This parameter is used to specify how many rows of demo raw data to generate and must, therefore, be an integer and greater than zero. Users, for example, can randomly generate demo raw data for 10,000 participants by executing a single line of code:The get_capl_demo_data(n = 10000)capl_demo_data2 <- R str function can be called to verify how many rows of data were created.The base str(capl_demo_data2)#> \u2019data.frame\u2019:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a010000 obs. of 60 variables:#> $ age:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 10 10 9 12 9 12 10 11 9 11 \u2026#> $ gender:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0chr \"f\" \"Boy\" \"g\" \"Female\" \u2026#> $ pacer_lap_distance:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0num 20 20 15 20 15 20 15 20 15 20 \u2026#> $ pacer_laps:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 75 93 102 131 96 151 129 150 127 10 \u2026#> $ plank_time:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 132 125 120 38 37 173 164 137 267 38 \u2026#> $ camsa_skill_score1:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 8 NA 7 5 6 6 10 4 10 7 \u2026#> $ camsa_time1:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 19 16 34 NA 32 16 19 20 25 25 \u2026#> $ camsa_skill_score2:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 7 10 9 6 10 8 6 6 7 11 \u2026#> $ camsa_time2:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 25 32 35 23 35 14 29 27 18 24 \u2026#> $ steps1:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int 19261 22363 1181 5950 7020 21141 22435 18804 16575 \u2026### For complete output, refer to the capl vignetteexport_capl_data function allows them to export data objects to Excel.If users prefer to examine the CAPL-2 demo raw data in a workbook, the export_capl_dataget_capl) in the capl package to compute CAPL-2 scores and interpretations, they must ensure their variable names match the names of the 60 required variables. Users can rename their variables by calling the rename_variable function to be renamed, and the replace parameter must be a character vector representing the new names for the variables specified in the search parameter. Below we show how to rename variables using a fake dataset called raw_data.If users import their own raw data and plan to use the main function to help provide a \u201cquiet\u201d user experience:There are eight validation functions included in the \u25cb validate_age\u25cb validate_character\u25cb validate_domain_score\u25cb validate_gender\u25cb validate_integer\u25cb validate_number\u25cb validate_scale\u25cb validate_stepsUsers can learn more about these functions by accessing the documentation within the R environment.?validate_age?validate_character?validate_domain_score?validate_gender?validate_integer?validate_number?validate_scale?validate_stepsSections 2.7.2 and 2.7.3 illustrate examples of validation.age variable to execute a computation , the age variable is validated via the validate_age function.The CAPL-2 is currently validated with 8- to 12-year-old children. However, when a function requires the validate_age)validated_age <- Notice the NA values in the results.validated_age#> [1] NA 8 9 10 11 12 NA NA NA 12 8The first element is NA because the original value is 7 and the next five elements are identical to their original values because they are integers between 8 and 12. Recall that the CAPL-2 is validated with children aged 8 to 12 years, hence why the first value is NA . The next two elements because the original values (\"\" and NA) are obviously invalid. The last element is 8, but notice that the original value is a decimal. Because 8.5 is between 8 and 12, it is considered valid but the floor of the value is returned since CAPL-2 performs age-specific computations based on integer age.gender variable to execute a computation, the gender variable is validated via the validate_gender function.The CAPL-2 is currently validated for children who identify as boys or girls. When a function requires the validate_gender)validated_gender <- validated_gender#> [1] \"girl\" \"girl\" \"girl\" \"girl\" \"girl\" \"girl\" \"girl\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"girl\"The validate_gender function behaves in a similar fashion for the male gender; it also accepts a number of case-insensitive options and returns a standardized \u201cboy\u201d value.Notice the results again. This function accepts a number of case-insensitive options for the female gender and returns a standardized \u201cgirl\u201d value. The two elements that are returned as NA have original values that are obviously invalid (\"\" and NA). validate_gender)validated_gender <- validated_gender#> [1] \"boy\" \"boy\" \"boy\" \"boy\" \"boy\" \"boy\" \"boy\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"boy\"www.capl-eclp.ca/capl-manual):The CAPL-2 scoring system is outlined in capl package is the get_capl function. This function takes two parameters, raw_data and sort. It computes the CAPL-2 scores in capl package. The raw_data parameter must be structured as a data frame and contain the raw data. The sort parameter is set to \u201casis\u201d by default. This means the new computed variables will be added to the data frame as they are computed. If sort is set to \u201cabc\u201d, all variables will be sorted alphabetically whereas if sort is set to \u201czyx\u201d, all variables will be sorted in reverse alphabetical order. Once the raw data has been imported, computing the CAPL-2 scores and interpretations is as simple as executing one line of code:The main function in the get_caplcapl_results <- str function , the physical competence score is computed by summing the plank, PACER and CAMSA scores:As illustrated in pacer_laps_20m function is used to convert PACER (Progressive Aerobic Cardiovascular Endurance Run) 15-metre shuttle run laps to 20-metre shuttle run laps. If laps are already 20-metre laps, the data are returned as is unless outside the valid range (1-229). This variable is used to compute the PACER score.The get_pacer_20m_lapscapl_demo_data$pacer_laps_20m#> [1] 18 31 169 38 63 12 25 110 33 NA 127 62 39 19 NA 84 145 166#> [19] 108 125 98 147 85 49 4 118 144 85 122 85 197 5 184 19 63 112#> [37] 89 46 178 35 69 122 54 79 120 85 1 187 59 178 47 55 89 98#> [55] 79 119 11 70 89 88 68 82 116 38 152 195 4 69 100 99 NA 88#> [73] 57 43 98 125 127 5 16 173 20 33 89 99 39 35 43 100 177 15#> [91] 141 141 39 NA 8 41 43 2 101 NA 54 78 90 176 40 2 122 58#> [109] 98 5 51 112 101 122 12 177 38 92 31 53 102 200 138 166 62 31#> [127] 86 75 87 56 147 140 45 51 136 74 148 194 67 142 172 121 NA 78#> [145] 40 18 59 190 78 69 33 78 78 58 84 122 27 199 147 75 180 84#> [163] 36 129 14 133 70 65 8 43 110 64 69 120 125 28 142 115 108 14### For complete output, refer to the capl vignetteget_pacer_score function computes a PACER score that ranges from zero to 10 based on the number of PACER laps run at a 20-metre distance. This score is used to compute the physical competence domain score variable.The get_pacer_score(capl_demo_data$pacer_laps_20m)capl_demo_data$pacer_score <- capl_demo_data$pacer_score#> [1] 3 6 10 7 10 2 5 10 6 NA 10 10 7 3 NA 10 10 10 10 10 10 10 10 9 0#> [26] 10 10 10 10 10 10 1 10 3 10 10 10 9 10 7 10 10 10 10 10 10 0 10 10 10#> [51] 9 10 10 10 10 10 2 10 10 10 10 10 10 7 10 10 0 10 10 10 NA 10 10 8 10#> [76] 10 10 1 3 10 4 6 10 10 7 7 8 10 10 3 10 10 7 NA 1 8 8 0 10 NA#> [101] 10 10 10 10 8 0 10 10 10 1 10 10 10 10 2 10 7 10 6 10 10 10 10 10 10#> [126] 6 10 10 10 10 10 10 9 10 10 10 10 10 10 10 10 10 NA 10 8 3 10 10 10 10#> [151] 6 10 10 10 10 10 5 10 10 10 10 10 7 10 2 10 10 10 1 8 10 10 10 10 10#> [176] 5 10 10 10 2 10 10 8 10 10 10 10 10 10 10 10 10 5 4 8 10 10 3 10 10#> [201] 3 5 10 10 10 10 10 3 NA 10 10 6 7 10 10 NA 5 9 10 10 7 9 NA 10 9#> [226] 10 10 9 10 10 NA 6 10 7 10 5 10 10 10 10 10 10 NA 10 10 10 1 10 NA 10### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$pacer_interpretation#> [1] \"beginning\" \"beginning\" \"progressing\" \"beginning\" \"beginning\"#> [6] \"beginning\" \"beginning\" \"progressing\" \"beginning\" NA#> [11] NA \"beginning\" NA NA NA#> [16] \"progressing\" \"beginning\" \"progressing\" \"beginning\" \"progressing\"#> [21] \"beginning\" \"beginning\" \"progressing\" NA NA#> [26] NA \"beginning\" NA \"beginning\" \"progressing\"#> [31] \"progressing\" \"beginning\" \"beginning\" NA \"beginning\"#> [36] NA NA \"beginning\" \"progressing\" \"beginning\"#> [41] \"beginning\" \"progressing\" \"progressing\" \"beginning\" \"beginning\"#> [46] \"progressing\" NA \"progressing\" NA NA### For complete output, refer to the capl vignetteget_plank_score function computes a plank score that ranges from zero to 10 based on the duration of time (in seconds) for which a plank is held. This score is used to compute the physical competence domain score.The get_plank_score(capl_demo_data$plank_time)capl_demo_data$plank_score <- capl_demo_data$plank_score#> [1] 10 10 0 10 10 9 1 10 0 3 10 10 10 10 10 10 10 10 0 10 10 5 3 10 9#> [26] 10 10 0 10 5 0 0 5 10 5 10 4 7 10 3 6 10 0 10 8 6 10 10 0 10#> [51] 5 9 10 10 10 10 10 10 10 10 10 8 0 10 4 10 2 9 0 6 10 10 7 10 4#> [76] 10 10 10 6 0 10 10 10 10 9 10 10 10 10 5 0 10 10 10 1 8 10 10 8 2#> [101] 4 10 0 10 2 10 9 10 3 10 10 5 10 8 4 10 10 10 10 0 10 10 0 10 10#> [126] 10 10 10 10 10 5 10 3 10 0 10 7 0 10 7 0 10 10 10 6 10 10 10 0 1#> [151] 5 10 10 5 2 10 4 10 10 10 10 1 10 0 8 10 10 0 7 7 10 10 1 10 10#> [176] 10 10 10 10 10 1 0 9 10 10 10 10 10 10 10 6 3 3 10 10 1 10 10 10 8#> [201] 0 0 10 4 10 3 10 10 3 0 10 3 10 10 10 7 10 0 10 10 10 1 10 10 0#> [226] 10 10 10 2 4 10 0 4 0 10 10 0 6 10 10 10 0 10 10 8 10 10 10 0 10### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$plank_interpretation#> [1] \"excelling\" \"excelling\" \"beginning\" \"excelling\" \"excelling\"#> [6] \"excelling\" \"beginning\" \"excelling\" \"beginning\" \"progressing\"#> [11] NA \"excelling\" NA NA \"excelling\"#> [16] \"excelling\" \"excelling\" \"excelling\" \"beginning\" \"excelling\"#> [21] \"excelling\" \"achieving\" \"progressing\" NA NA#> [26] NA \"excelling\" NA \"excelling\" \"progressing\"#> [31] \"beginning\" \"beginning\" \"progressing\" NA \"progressing\"#> [36] NA NA \"achieving\" \"excelling\" \"progressing\"#> [41] \"progressing\" \"excelling\" \"beginning\" \"excelling\" \"achieving\"#> [46] \"progressing\" \"excelling\" \"excelling\" NA NA### For complete output, refer to the capl vignetteget_camsa_time_score function computes the CAMSA (Canadian Agility and Movement Skill Assessment) time score that ranges from one to 14 based on the time taken (in seconds) to complete a trial capl_demo_data$camsa_score#> [1] 5.357143 3.571429 9.285714 5.000000 6.785714 NA NA#> [8] 7.857143 4.285714 8.571429 5.357143 8.571429 8.571429 9.285714#> [15] 6.428571 9.285714 NA 6.428571 3.214286 3.571429 6.428571#> [22] 5.714286 8.928571 7.500000 NA 8.571429 NA 8.214286#> [29] 10.000000 2.857143 NA 5.714286 NA 8.571429 10.000000#> [36] 7.500000 7.857143 6.428571 7.142857 6.428571 5.714286 NA#> [43] 6.071429 5.714286 9.642857 2.142857 7.500000 8.214286 8.571429#> [50] 7.857143 7.500000 10.000000 7.142857 7.142857 NA 4.285714#> [57] 6.785714 6.428571 7.857143 6.428571 3.928571 4.285714 10.000000#> [64] 5.714286 NA 7.500000 6.071429 NA 7.500000 NA### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain scoreThe get_capl_interpretationcapl_demo_data$camsa_interpretation#> [1] \"beginning\" \"beginning\" \"excelling\" \"beginning\" \"progressing\"#> [6] NA NA \"progressing\" \"beginning\" \"excelling\"#> [11] NA \"achieving\" NA NA \"progressing\"#> [16] \"excelling\" NA \"progressing\" \"beginning\" \"beginning\"#> [21] \"progressing\" \"beginning\" \"excelling\" NA NA#> [26] NA NA NA \"excelling\" \"beginning\"#> [31] NA \"beginning\" NA NA \"excelling\"#> [36] NA NA \"progressing\" \"progressing\" \"progressing\"#> [41] \"beginning\" NA \"progressing\" \"beginning\" \"excelling\"#> [46] \"beginning\" \"progressing\" \"achieving\" NA NA### For complete output, refer to the capl vignetteget_pc_score function computes a physical competence domain score that ranges from zero to 30 based on the PACER, plank and CAMSA scores. If one protocol score is missing or invalid, a weighted domain score is computed from the other two protocol scores. This score is used to compute the physical competence domain score.The get_pc_scorecapl_demo_data$pc_score#> [1] 19.5 24.0 15.0 22.0 30.0 16.5 9.0 30.0 9.0 NA 30.0 30.0 25.5 19.5 NA#> [16] 30.0 30.0 30.0 15.0 30.0 30.0 22.5 19.5 28.5 13.5 30.0 30.0 15.0 30.0 22.5#> [31] 15.0 1.5 22.5 19.5 25.0 30.0 21.0 24.0 30.0 15.0 24.0 30.0 15.0 30.0 27.0#> [46] 24.0 15.0 30.0 15.0 30.0 21.0 29.0 30.0 30.0 30.0 30.0 18.0 30.0 30.0 30.0#> [61] 30.0 27.0 20.0 25.5 21.0 30.0 3.0 28.5 15.0 24.0 NA 30.0 25.5 27.0 21.0#> [76] 30.0 30.0 16.5 13.5 15.0 21.0 24.0 30.0 25.0 24.0 25.5 27.0 30.0 30.0 12.0#> [91] 15.0 30.0 25.5 22.5 3.0 24.0 27.0 15.0 27.0 NA 21.0 30.0 15.0 30.0 15.0#> [106] 15.0 28.5 30.0 19.5 16.0 30.0 22.5 30.0 27.0 11.0 30.0 25.5 30.0 24.0 15.0#> [121] 30.0 30.0 15.0 30.0 30.0 24.0 30.0 30.0 30.0 30.0 22.5 30.0 18.0 30.0 15.0#> [136] 30.0 25.5 15.0 30.0 25.5 15.0 30.0 NA 30.0 21.0 19.5 30.0 30.0 15.0 16.5### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$pc_interpretation#> [1] \"achieving\" \"excelling\" \"progressing\" \"excelling\" \"excelling\"#> [6] \"progressing\" \"beginning\" \"excelling\" \"beginning\" NA#> [11] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA#> [16] \"excelling\" \"excelling\" \"excelling\" \"progressing\" \"excelling\"#> [21] \"excelling\" \"excelling\" \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA#> [26] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\" \"achieving\"#> [31] \"progressing\" \"beginning\" \"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\"#> [36] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \"excelling\" \"excelling\" \"progressing\"#> [41] \"excelling\" \"excelling\" \"progressing\" \"excelling\" \"excelling\"#> [46] \"excelling\" \"progressing\" \"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA### For complete output, refer to the capl vignetteget_capl_domain_status function computes the status of a CAPL domain.The get_capl_domain_statuscapl_demo_data$pc_status#> [1] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [4] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\"#> [7] \"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [10] \"incomplete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\"complete\"#> [13] \"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\u00a0\"incomplete\"#> [16] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [19] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [22] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"#> [25] \"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\"#> [28] \"missing interpretation\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"### For complete output, refer to the capl vignettewww.capl-eclp.ca/capl-manual), the formula for computing the daily behaviour score is:As illustrated in get_step_average function computes the daily arithmetic mean of a week of steps measured by pedometry. This variable is used to compute the step score.The get_step_average(step_df <- \u00a0\u00a0\u00a0\u00a0capl_demo_data)get_step_average function returns a data frame with nine columns: steps1 , steps2 , steps3 , steps4 , steps5 , steps6 , steps7 , valid_days and step_average capl_demo_data$step_score <- capl_demo_data$step_score#> [1] 25 25 19 21 23 22 23 15 22 23 25 12 19 20 9 24 24 22 24 21 21 25 23 22 23#> [26] 25 21 23 22 22 23 23 18 22 20 25 25 25 25 23 19 25 23 25 22 16 13 24 21 12#> [51] 25 25 24 20 23 25 14 23 25 20 25 20 13 25 21 22 5 21 25 18 24 14 25 19 20#> [76] 22 20 8 25 21 25 25 19 21 14 25 25 25 16 25 21 20 21 25 25 25 25 23 25 25#> [101] 24 22 23 25 23 13 11 25 NA 23 25 10 25 25 19 13 24 21 16 18 25 25 24 20 19#> [126] 22 11 23 14 15 17 24 24 14 23 25 21 20 22 13 18 25 20 18 19 12 14 25 23 25#> [151] 22 17 22 18 22 23 25 23 14 19 18 25 25 17 25 16 25 22 19 22 22 6 22 16 25#> [176] 24 22 23 22 24 15 21 25 25 22 25 24 25 22 22 23 14 22 14 22 22 24 19 23 16#> [201] 14 17 4 24 22 25 23 20 25 19 24 22 25 24 15 25 22 21 25 22 16 23 16 25 25#> [226] 25 19 13 20 25 20 25 21 25 25 22 21 18 18 24 21 15 23 18 21 25 24 25 25 25### For complete output, refer to the capl vignetteget_self_report_pa function computes a score that ranges from zero to five based on the response to \u201cDuring the past week (7 days), on how many days were you physically active for a total of at least 60 minutes per day? ?\u201d in the CAPL-2 Questionnaire (www.capl-eclp.ca/wp-content/uploads/2018/02/CAPL-2-questionnaire.pdf). This score is used to compute the daily behaviour domain score.The get_self_report_pa_score(capl_demo_data$self_report_pa)capl_demo_data$self_report_pa_score <- capl_demo_data$self_report_pa_score#> [1] NA 1 1 3 2 4 NA 5 5 5 NA 3 1 4 5 5 0 5 5 5 5 5 5 NA 5#> [26] 3 4 5 4 1 2 0 5 5 5 5 4 3 4 2 4 5 5 5 2 5 5 NA 5 5#> [51] 1 5 3 1 0 5 3 2 5 1 2 0 5 NA 3 5 4 0 3 NA 5 4 1 NA 0#> [76] 5 0 2 0 NA 5 5 1 1 3 3 5 2 5 4 5 5 4 3 1 4 2 1 5 5#> [101] 5 2 1 4 3 2 5 5 3 2 2 5 5 5 2 NA 5 1 5 5 NA 5 5 1 0#> [126] 4 5 4 0 0 5 4 5 0 5 5 5 5 2 5 5 5 2 5 1 3 5 5 NA 5#> [151] 5 0 2 1 0 5 3 3 2 0 5 1 5 4 0 3 5 5 3 5 5 5 0 5 4#> [176] NA 5 5 4 5 3 4 3 0 2 1 5 3 0 5 1 5 5 5 5 0 2 3 0 1#> [201] 0 1 5 5 5 2 5 3 4 2 5 5 5 5 2 5 5 1 0 1 5 4 1 5 3#> [226] 4 3 5 0 5 2 5 0 NA 5 3 3 NA 2 0 4 5 5 5 5 4 0 3 3 2### For complete output, refer to the capl vignetteget_db_score function computes a daily behaviour domain score that ranges from 0 to 30 based on the step and self-reported physical activity scores. This score is used to compute the overall physical literacy score.The get_db_scorecapl_demo_data$db_score#> [1] NA 26 20 24 25 26 NA 20 27 28 NA 15 20 24 14 29 24 27 29 26 26 30 28 NA 28#> [26] 28 25 28 26 23 25 23 23 27 25 30 29 28 29 25 23 30 28 30 24 21 18 NA 26 17#> [51] 26 30 27 21 23 30 17 25 30 21 27 20 18 NA 24 27 9 21 28 NA 29 18 26 NA 20#> [76] 27 20 10 25 NA 30 30 20 22 17 28 30 27 21 29 26 25 25 28 26 29 27 24 30 30#> [101] 29 24 24 29 26 15 16 30 NA 25 27 15 30 30 21 NA 29 22 21 23 NA 30 29 21 19#> [126] 26 16 27 14 15 22 28 29 14 28 30 26 25 24 18 23 30 22 23 20 15 19 30 NA 30#> [151] 27 17 24 19 22 28 28 26 16 19 23 26 30 21 25 19 30 27 22 27 27 11 22 21 29#> [176] NA 27 28 26 29 18 25 28 25 24 26 29 28 22 27 24 19 27 19 27 22 26 22 23 17#> [201] 14 18 9 29 27 27 28 23 29 21 29 27 30 29 17 30 27 22 25 23 21 27 17 30 28#> [226] 29 22 18 20 30 22 30 21 NA 30 25 24 NA 20 24 25 20 28 23 26 29 24 28 28 27### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$db_interpretation#> [1] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"achieving\" \"progressing\" \"achieving\" \"achieving\"#> [6] \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\"progressing\" \"excelling\" \"excelling\"#> [11] NA\u00a0\u00a0\u00a0\u00a0\"progressing\" NA\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\"progressing\"#> [16] \"excelling\" \"achieving\" \"excelling\" \"excelling\" \"excelling\"#> [21] \"achieving\" \"excelling\" \"excelling\" NA\u00a0\u00a0\u00a0\u00a0NA#> [26] NA\u00a0\u00a0\u00a0\u00a0\"excelling\" NA\u00a0\u00a0\u00a0\u00a0\"excelling\" \"achieving\"#> [31] \"achieving\" \"achieving\" \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\"excelling\"#> [36] NA\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\"excelling\" \"excelling\" \"achieving\"#> [41] \"achieving\" \"excelling\" \"excelling\" \"excelling\" \"achieving\"#> [46] \"progressing\" \"progressing\" NA\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0NA### For complete output, refer to the capl vignetteget_capl_domain_status function computes the status of a CAPL domain.The get_capl_domain_statuscapl_demo_data$db_status#> [1] \"incomplete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [4] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [7] \"incomplete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [10] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"incomplete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [13] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [16] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [19] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [22] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"incomplete\"#> [25] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [28] \"missing interpretation\" \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"### For complete output, refer to the capl vignettewww.capl-eclp.ca/capl-manual), the formula for computing the motivation and confidence score is:As illustrated in get_predilection_score function computes a predilection score that ranges from 1.8 to 7.5 based on responses to three items from the Children\u2019s Self-Perception of Adequacy in and Predilection for Physical Activity as they appear in the CAPL-2 Questionnaire (www.capl-eclp.ca/wp-content/uploads/2018/02/CAPL-2-questionnaire.pdf). This score is used to compute the motivation and confidence domain score.The get_predilection_scorecapl_demo_data$predilection_score#> [1] 3.6 4.9 5.5 3.0 NA 3.0 6.2 4.9 4.8 4.9 3.0 3.0 5.6 4.9 5.5 5.5 4.9 4.3#> [19] 5.6 3.6 4.2 3.6 6.1 3.6 4.3 4.8 5.6 3.0 4.3 4.3 6.1 4.9 6.2 3.6 6.8 5.5#> [37] 5.5 6.2 3.0 2.4 4.3 3.6 5.5 6.1 NA 4.3 2.4 4.9 4.9 NA 5.5 4.3 4.2 4.2#> [55] 4.9 6.2 4.3 5.5 1.8 3.7 4.9 3.7 6.8 4.8 6.2 4.2 3.7 1.8 5.5 3.0 5.5 4.2#> [73] 4.8 5.5 4.9 3.6 4.9 3.7 3.6 3.6 4.9 6.2 4.2 3.7 3.7 3.6 3.0 2.4 4.2 4.2#> [91] 3.0 5.4 5.5 6.2 4.3 3.6 5.6 6.1 4.9 NA 4.2 5.5 6.8 4.8 4.9 4.9 4.9 2.4#> [109] 4.8 3.0 3.6 3.6 4.9 3.6 4.3 3.7 2.4 3.0 3.6 4.2 4.3 4.3 6.8 5.6 4.9 6.2#> [127] 3.0 3.0 5.5 3.6 4.2 3.7 6.1 3.7 3.6 6.2 6.1 4.8 3.6 4.9 1.8 5.6 3.0 4.9#> [145] 4.9 4.8 3.0 4.8 4.2 4.9 2.4 5.5 3.7 4.3 3.6 3.0 4.8 5.5 7.5 4.9 4.8 4.2#> [163] 3.0 2.4 5.5 2.4 5.5 6.1 3.6 5.5 4.3 4.2 4.3 NA 6.1 3.6 4.9 5.6 3.7 2.4### For complete output, refer to the capl vignetteget_adequacy_score function computes an adequacy score that ranges from 1.8 to 7.5 based on responses to three items from the Children\u2019s Self-Perception of Adequacy in and Predilection for Physical Activity as they appear in the CAPL-2 Questionnaire (www.capl-eclp.ca/wp-content/uploads/2018/02/CAPL-2-questionnaire.pdf). This score is used to compute the motivation and confidence domain score.The get_adequacy_scorecapl_demo_data$adequacy_score#> [1] 2.4 5.5 7.5 4.3 5.5 5.5 4.2 4.3 3.6 4.3 6.2 4.9 4.9 4.2 4.3 5.6 4.2 4.8#> [19] 4.8 6.2 4.3 4.8 4.9 3.6 6.8 4.3 6.2 6.2 4.3 7.5 6.1 5.6 4.9 6.2 6.2 2.4#> [37] 4.2 5.6 5.6 4.2 5.5 4.9 5.5 4.9 4.2 6.2 5.6 6.2 4.9 4.2 3.6 3.7 3.6 6.8#> [55] 1.8 3.6 5.6 4.9 3.6 3.0 3.6 4.9 3.7 4.9 3.6 3.7 4.2 5.6 6.1 4.9 3.6 3.0#> [73] 2.4 4.3 6.1 3.0 3.0 3.7 4.9 4.3 5.4 5.5 3.0 2.4 6.1 5.6 5.5 3.7 4.2 2.4#> [91] 5.6 4.9 3.0 5.6 4.9 3.6 4.9 6.8 4.9 2.4 5.6 4.8 4.2 3.0 4.9 3.0 3.0 3.7#> [109] 4.9 3.7 6.2 4.9 5.5 5.6 5.6 4.8 3.7 6.2 3.0 5.4 4.9 3.6 5.4 3.0 4.8 3.6#> [127] 4.8 4.2 4.2 2.4 4.9 4.3 6.2 2.4 4.9 4.9 4.9 4.2 4.9 5.5 4.9 5.5 7.5 5.6#> [145] 5.5 3.0 4.9 6.1 4.9 5.5 3.0 5.6 6.2 4.9 4.3 4.9 5.6 4.2 2.4 5.5 4.9 3.7#> [163] 4.3 4.3 4.9 4.3 6.1 4.8 4.9 5.5 6.2 6.1 3.6 2.4 3.6 4.9 6.2 4.3 4.3 4.2### For complete output, refer to the capl vignetteget_intrinsic_motivation_score function computes an intrinsic motivation score that ranges from 1.5 to 7.5 based on responses to three items from the Behavioral Regulation in Exercise Questionnaire (BREQ) as they appear in the CAPL-2 Questionnaire (www.capl-eclp.ca/wp-content/uploads/2018/02/CAPL-2-questionnaire.pdf). This score is used to compute the motivation and confidence domain score.The get_intrinsic_motivation_scorecapl_demo_data$intrinsic_motivation_score#> [1] 6.0 4.5 5.0 4.5 4.0 5.5 6.5 NA 5.5 NA 6.5 5.0 4.0 3.5 NA 6.0 4.5 4.5#> [19] 5.0 3.0 2.0 2.5 3.5 NA 5.0 4.0 4.5 7.0 3.5 4.0 NA 6.0 5.0 3.5 NA 4.5#> [37] 4.5 NA 5.0 5.0 4.0 3.5 6.5 4.0 NA 4.5 3.0 NA 5.0 5.0 4.0 6.5 NA 4.0#> [55] 5.0 3.5 6.5 2.5 6.5 5.0 6.0 5.5 4.5 3.5 3.0 2.5 4.5 4.5 4.5 4.5 4.5 3.0#> [73] 4.5 4.5 5.0 5.0 2.5 6.5 5.5 4.5 6.0 2.5 4.0 7.0 4.5 NA 3.5 NA 3.5 3.0#> [91] 4.0 4.0 5.0 5.0 2.5 NA 3.5 6.0 1.5 6.5 5.5 5.5 5.5 4.0 4.0 4.0 NA 3.0#> [109] NA 4.0 5.0 5.5 3.5 4.0 3.0 4.0 6.5 3.5 6.0 3.0 4.5 6.0 NA 3.0 3.5 NA#> [127] 5.0 3.0 NA 5.5 5.5 6.5 4.0 NA 5.0 5.0 5.0 NA 3.0 2.5 NA 4.0 6.0 5.0#> [145] 5.0 3.5 4.5 5.0 NA 4.5 2.5 4.0 4.0 5.5 3.0 7.0 5.0 5.0 5.0 NA 5.5 7.5#> [163] 4.0 2.5 3.5 5.5 NA 4.5 6.0 5.0 5.0 5.5 2.5 4.5 5.5 2.0 5.0 7.0 NA 6.0### For complete output, refer to the capl vignetteget_pa_competence_score function computes a physical activity competence score that ranges from 1.5 to 7.5 based on responses to three items from the Behavioural Regulation in Exercise Questionnaire as they appear in the CAPL-2 Questionnaire (www.capl-eclp.ca/wp-content/uploads/2018/02/CAPL-2-questionnaire.pdf). This score is used to compute the motivation and confidence domain score.The get_pa_competence_scorecapl_demo_data$pa_competence_score#> [1] 5.5 5.0 3.0 5.0 4.0 2.5 4.5 4.5 4.5 6.0 4.5 4.0 3.5 4.0 4.0 3.5 5.0 3.5#> [19] 5.0 6.0 5.5 4.0 NA 4.5 5.5 NA 5.0 4.0 5.0 5.0 4.0 NA 3.0 NA 4.5 3.0#> [37] 6.0 NA 1.5 3.5 4.5 6.5 2.5 5.5 3.5 6.0 4.0 6.5 5.5 5.0 6.0 NA 3.0 5.5#> [55] 5.0 5.0 5.5 NA 5.0 5.0 5.0 NA 4.5 5.0 4.0 7.0 3.5 5.5 4.5 4.5 NA 2.5#> [73] 4.0 3.5 4.5 5.0 4.0 4.0 3.5 3.5 2.5 5.0 5.0 3.0 5.0 3.0 5.0 NA 3.0 3.5#> [91] 3.5 5.0 5.0 NA NA 5.0 3.5 5.0 5.0 4.0 NA 3.5 5.0 4.5 5.5 7.5 4.0 5.0#> [109] NA 4.0 6.0 NA 5.5 6.0 5.5 3.0 4.0 3.5 4.0 6.0 3.5 4.0 NA 5.0 6.0 7.0#> [127] 4.0 4.5 4.5 2.5 NA 2.5 7.5 4.5 4.0 4.0 NA 3.0 4.0 5.5 NA 4.0 3.5 4.5#> [145] 3.5 5.0 3.0 NA 5.5 4.5 5.5 3.5 6.0 5.0 6.5 6.0 4.0 2.0 4.0 NA 2.5 4.5#> [163] 4.5 5.0 6.0 5.5 2.0 7.0 NA 3.5 3.5 NA 5.0 NA 5.5 6.0 5.5 5.0 4.0 4.0### For complete output, refer to the capl vignetteget_mc_score function computes a motivation and confidence domain score that ranges from zero to 30 based on the predilection, adequacy, intrinsic motivation and physical activity competence scores. If one of the scores is missing or invalid, a weighted domain score is computed from the other three scores. This score is used to compute the overall physical literacy score.The get_mc_scorecapl_demo_data$mc_score#> [1] 15.333333 20.533333 21.333333 16.400000 NA 14.666667 19.866667#> [8] 18.266667 17.200000 20.266667 18.266667 15.866667 18.666667 17.466667#> [15] 18.400000 19.466667 18.800000 16.800000 20.533333 21.066667 18.666667#> [22] 16.533333 NA 15.600000 22.133333 NA 22.400000 17.600000#> [29] 18.133333 22.400000 21.600000 NA 18.800000 NA 23.333333#> [36] 14.533333 20.933333 NA 13.466667 13.466667 19.066667 20.000000#> [43] 18.000000 22.000000 NA 22.000000 16.000000 23.466667 20.400000#> [50] NA 20.133333 NA 14.400000 22.000000 15.600000 19.733333#> [57] 20.533333 NA 13.866667 15.600000 18.000000 NA 20.000000#> [64] 19.600000 18.400000 19.866667 15.200000 17.200000 21.466667 16.533333### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$mc_interpretation#> [1] \"beginning\" \"progressing\" \"progressing\" \"progressing\" NA#> [6] \"beginning\" \"progressing\" \"progressing\" \"progressing\" \"progressing\"#> [11] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"beginning\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\"#> [16] \"progressing\" \"progressing\" \"progressing\" \"progressing\" \"progressing\"#> [21] \"progressing\" \"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA#> [26] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\" \"progressing\"#> [31] \"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"achieving\"#> [36] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"beginning\" \"beginning\"#> [41] \"progressing\" \"progressing\" \"progressing\" \"progressing\" NA#> [46] \"progressing\" \"beginning\" \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA### For complete output, refer to the capl vignetteget_capl_domain_status function computes the status of a CAPL domain.The get_capl_domain_statuscapl_demo_data$mc_status#> [1] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [4] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0 \"complete\"#> [7] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0 \"complete\"#> [10] \"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\" \"complete\"#> [13] \"missing interpretation\" \"missing interpretation\" \"missing protocol\"#> [16] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [19] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [22] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing protocol\" \"missing interpretation\"#> [25] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [28] \"missing interpretation\" \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"### For complete output, refer to the capl vignettewww.capl-eclp.ca/capl-manual), the formula for computing the knowledge and understanding score is:As illustrated in get_binary function computes a binary score for a response to a questionnaire item based on the value(s) set as answer(s) to the item.The get_binary_score)capl_demo_data$pa_guideline_score <- capl_demo_data$pa_guideline_score#> [1] 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0#> [26] 1 1 0 0 0 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 1 0 0 1 0#> [51] 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 0 1 0 1#> [76] 0 0 0 1 1 1 0 0 1 0 0 1 0 0 1 0 1 0 0 1 1 0 0 0 1#> [101] 0 0 1 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0 1 1 1 1 0 1#> [126] 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 1 0 0 1 1 1 0 0 0 0#> [151] 0 0 0 0 0 0 1 1 0 0 0 1 0 1 0 0 0 0 0 1 0 1 0 0 0#> [176] 0 1 0 1 0 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1#> [201] 0 1 0 0 0 0 1 1 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0#> [226] 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 1 1 1 0 0 1 0### For complete output, refer to the capl vignetteget_binary function is also called to analyze responses for Q2, Q3, and Q4.The get_binary_score)capl_demo_data$crf_means_score <- capl_demo_data$crf_means_score#> [1] 0 0 0 1 1 0 1 0 0 0 1 1 0 0 0 1 0 0 0 0 0 1 0 0 0#> [26] 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0#> [51] 0 0 0 1 0 1 1 1 0 0 0 0 0 0 1 0 0 0 1 1 0 1 1 0 1#> [76] 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1#> [101] 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0#> [126] 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 0 1 1 0 0 0 0 1#> [151] 0 0 0 1 0 1 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0#> [176] 0 0 1 1 0 0 0 0 0 0 0 1 1 0 0 0 1 1 1 0 0 0 1 0 0#> [201] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0#> [226] 0 1 0 1 1 0 0 0 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1### For complete output, refer to the capl vignetteget_binary_score)capl_demo_data$ms_means_score <- capl_demo_data$ms_means_score#> [1] 0 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 0 0 0 0 0 0#> [26] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0#> [51] 0 1 1 0 1 0 1 1 0 1 0 0 0 0 1 1 1 1 0 1 1 1 0 1 0#> [76] 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 0 0 0#> [101] 1 0 0 0 0 0 0 0 0 0 1 0 0 1 0 1 1 0 0 0 1 1 1 0 0#> [126] 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0#> [151] 0 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 1 0 0 0 0 0 0 1 1#> [176] 1 0 0 0 0 1 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0#> [201] 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 NA 0 0 0 0 0 1 0 1 0#> [226] 0 0 1 0 0 1 0 1 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 0### For complete output, refer to the the capl vignetteget_binary_score)capl_demo_data$sports_skill_score <- capl_demo_data$sports_skill_score#> [1] 0 1 1 0 0 0 0 0 1 0 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 1 0 0#> [38] 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0#> [75] 1 0 0 1 0 1 0 0 0 1 0 0 1 1 0 0 0 0 1 1 0 0 0 1 0 1 0 0 1 1 0 0 1 0 0 1 0#> [112] 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0#> [149] 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0#> [186] 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 0 1 0 0 0 0 0#> [223] 0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1#> [260] 0 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0 1 1 1 1 0 0 0 0 0 1 1 0 0 0 0 0 1 0 0 0#> [297] 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 1 0 0 1#> [334] 0 0 0 1 0 0 0 1 1 0 0 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0### For complete output, refer to the capl vignetteget_fill_in_the_blanks_score function computes a score that ranges from zero to five for responses to the fill in the blanks question. This score is used to compute the knowledge and understanding domain score.The get_fill_in_the_blanks_scorecapl_demo_data$fill_in_the_blanks_score#> [1] 1 5 2 5 5 3 3 3 3 4 5 4 3 4 4 3 2 2 3 4 3 3 4 1 5 4 6 4 4 4 4 4 1 4 4 2 4#> [38] 4 3 5 4 3 4 3 5 5 4 5 2 3 4 4 2 3 6 3 3 5 5 2 6 2 2 4 2 4 3 3 6 2 3 5 5 3#> [75] 3 2 5 2 3 3 5 4 4 4 5 5 2 3 4 3 4 5 3 1 5 5 5 4 4 4 5 3 4 2 0 3 3 4 4 3 3#> [112] 5 3 4 4 2 2 3 6 4 3 5 5 2 3 3 5 5 3 6 4 3 2 3 3 0 3 4 3 3 3 3 4 3 3 2 5 5#> [149] 4 5 4 3 3 5 0 3 3 4 4 2 2 3 4 1 3 3 2 3 6 3 4 4 4 6 2 4 2 3 2 5 4 3 2 5 5#> [186] 5 3 2 5 3 3 3 3 5 6 2 4 4 3 4 4 2 5 2 4 3 4 4 1 4 3 5 4 3 3 4 3 2 0 5 4 4#> [223] 4 5 3 6 2 5 4 2 3 3 2 4 3 4 3 2 5 3 3 5 3 3 4 5 0 3 4 4 4 4 1 2 4 4 2 3 1#> [260] 3 5 2 3 5 4 1 3 3 3 4 3 3 3 4 3 4 5 0 5 3 3 3 3 5 6 5 3 4 3 3 6 6 2 1 2 2#> [297] 3 5 4 4 2 1 1 1 5 2 2 5 4 3 5 4 6 3 5 2 5 3 2 5 4 5 4 4 1 3 4 6 3 3 3 5 5#> [334] 2 3 4 3 5 5 4 4 0 4 3 4 3 3 3 4 2 3 2 3 6 5 3 5 2 4 4 5 3 2 4 3 2 3 3 5 2### For complete output, refer to the capl vignetteget_ku_score function computes a knowledge and understanding domain score that ranges from zero to 10 based on the physical activity guideline (Q1), cardiorespiratory fitness means (Q2), muscular strength and endurance means (Q3), sports skill (Q4) and fill in the blanks (Q5) scores. If one of the scores is missing or invalid, a weighted domain score is computed from the other four scores. This score is used to compute the overall physical literacy score.The get_ku_scorecapl_demo_data$ku_score#> [1] 1.000000 7.000000 4.000000 6.000000 6.000000 4.000000 6.000000 3.000000#> [9] 4.000000 4.000000 8.000000 6.000000 4.000000 4.000000 6.000000 4.000000#> [17] 2.000000 3.000000 4.000000 4.000000 3.000000 4.000000 4.000000 1.000000#> [25] 5.000000 5.000000 7.000000 5.000000 5.000000 5.000000 4.000000 5.000000#> [33] 1.000000 5.000000 6.000000 2.000000 4.000000 4.000000 3.000000 6.000000#> [41] 4.000000 3.000000 5.000000 4.000000 6.000000 7.000000 4.000000 7.000000#> [49] 3.000000 3.000000 4.000000 5.000000 3.000000 4.000000 7.000000 4.000000#> [57] 6.000000 7.000000 6.000000 4.000000 6.000000 2.000000 2.000000 4.000000#> [65] 4.000000 5.000000 5.000000 6.000000 8.000000 4.000000 4.000000 7.000000#> [73] 7.000000 4.000000 6.000000 2.000000 5.000000 3.000000 4.000000 5.000000### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$ku_interpretation#> [1] \"beginning\" \"achieving\" \"beginning\" \"progressing\" \"progressing\"#> [6] \"beginning\" \"progressing\" \"beginning\" \"beginning\" \"beginning\"#> [11] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\"#> [16] \"beginning\" \"beginning\" \"beginning\" \"beginning\" \"beginning\"#> [21] \"beginning\" \"beginning\" \"beginning\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA#> [26] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"beginning\" \"progressing\"#> [31] \"beginning\" \"beginning\" \"beginning\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\"#> [36] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"beginning\" \"beginning\" \"progressing\"#> [41] \"beginning\" \"beginning\" \"progressing\" \"beginning\" \"progressing\"#> [46] \"achieving\" \"beginning\" \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA### For complete output, refer to the capl vignetteget_capl_domain_status function computes the status of a CAPL domain.The get_capl_domain_statuscapl_demo_data$ku_status#> [1] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [4] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [7] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [10] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\" \"complete\"#> [13] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [16] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [19] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [22] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"#> [25] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [28] \"missing interpretation\" \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"### For complete output, refer to the capl vignetteget_capl_score function computes an overall physical literacy score that ranges from zero to 100 based on the physical competence, daily behaviour, motivation and confidence, and knowledge and understanding domain scores. If one of the scores is missing or invalid, a weighted score is computed from the other three scores.The get_capl_scorecapl_demo_data$capl_score#> [1] 54.28571 76.90000 60.00000 68.80000 79.00000 63.00000 52.00000 71.26667#> [9] 58.40000 74.66667 83.14286 67.90000 67.50000 65.10000 54.85714 83.60000#> [17] 74.60000 77.10000 68.40000 78.80000 75.00000 71.40000 70.83333 64.42857#> [25] 68.10000 80.46667 83.30000 68.20000 74.10000 71.30000 65.60000 51.50000#> [33] 65.60000 69.23333 79.33333 77.40000 74.20000 80.00000 77.10000 61.10000#> [41] 69.30000 81.50000 68.00000 84.50000 81.42857 73.00000 52.00000 86.38095#> [49] 64.30000 68.93333 70.10000 83.33333 74.40000 75.50000 79.86667 82.30000#> [57] 62.90000 79.20000 86.13333 71.70000 82.50000 67.80000 59.50000 68.14286#> [65] 65.80000 79.40000 32.90000 76.30000 71.60000 64.14286 73.04762 67.70000#> [73] 71.20000 69.71429 67.50000 75.60000 69.40000 47.40000 60.00000 51.28571### For complete output, refer to the capl vignetteget_capl_interpretation function computes an age- and gender-specific CAPL-2 interpretation for a given CAPL-2 protocol or domain score.The get_capl_interpretationcapl_demo_data$capl_interpretation#> [1] \"progressing\" \"excelling\" \"progressing\" \"achieving\" \"achieving\"#> [6] \"progressing\" \"beginning\" \"achieving\" \"progressing\" \"excelling\"#> [11] NA \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"progressing\"#> [16] \"excelling\" \"achieving\" \"excelling\" \"progressing\" \"excelling\"#> [21] \"achieving\" \"achieving\" \"achieving\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA#> [26] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"achieving\" \"achieving\"#> [31] \"progressing\" \"progressing\" \"progressing\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\"#> [36] NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"excelling\" \"excelling\" \"progressing\"#> [41] \"achieving\" \"excelling\" \"achieving\" \"excelling\" \"excelling\"#> [46] \"achieving\" \"progressing\" \"excelling\" NA\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0NA### For complete output, refer to the capl vignetteget_capl_domain_status function computes the status of a CAPL domain.The get_capl_domain_statuscapl_demo_data$capl_status#> [1] \"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [4] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [7] \"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [10] \"missing protocol\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\" \"complete\"#> [13] \"missing interpretation\" \"missing interpretation\" \"missing protocol\"#> [16] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [19] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"#> [22] \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"missing interpretation\"#> [25] \"missing interpretation\" \"missing interpretation\" \"complete\"#> [28] \"missing interpretation\" \"complete\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\"complete\"### For complete output, refer to the capl vignettecapl package makes use of the famous ggplo2 R package to create custom functions that render beautiful plots for visualizing CAPL-2 results.The get_capl_bar_plot function. The mean score for each interpretative category appears above each bar \")colors argument \",c\u00a0\u00a0\u00a0\u00a0colors = )export_capl_data function allows them to export their data to Excel or SPSS.If users want to export their data, the export_capl_dataexport_capl_datacapl package developed for use in the R environment. The primary motivation for developing the capl package was to offer interested users \u2013 most likely researchers \u2013 a fast, efficient, and reliable approach to analyzing CAPL-2 raw data. We begin this paper by discussing several preparatory steps that are required prior to using the capl package. These steps include preparing, formatting, and importing CAPL-2 raw data. We then use demo data to show that computing the CAPL-2 scores and interpretations is as a simple as executing one line of code. This one line of code uses the main (wrapper) function in the capl package (get_capl) to compute 40 variables. Next, we introduce each helper function that is called within the main function to explain how to compute individual variables and scores for each test element within the four domains as well as how to calculate an overall physical literacy score. Finally, we show how to visualize CAPL-2 results using the ggplot2 R package.In this paper we introduce the capl package is that it is specifically built for CAPL-2 raw data, and therefore not fully accessible to users with earlier versions of the CAPL. In the future, we intend to make the capl package available to users across all versions of the CAPL. The future version of the capl package will also include more data visualization features. We also plan to release an R Shiny application that runs locally in a web browser, providing users with a web-based interface for the capl package .One limitation of the current capl package, users are no longer required to perform a large number of computations nor are they burdened with the monotonous task of entering data individually for each participant via the CAPL-2 website. Furthermore, we carefully crafted the package to create a \u201cquiet\u201d user experience, whereby \u201cnoisy\u201d error messages are suppressed via validation. Instead of throwing noisy errors that halt code execution, the capl package returns missing or invalid values as NAs. The release of the capl package will contribute to the growing and popular topic of physical literacy, and will not only support current users of CAPL-2 but may also attract new users to this area of research.With the development of the"}
+{"text": "A covalent organic framework-based nanoplatform has been developed for cancer imaging, photodynamic therapy, and prognosis. In vitro and in vivo experiments revealed that the nanoplatform has a high specificity and inhibition effect toward cancer cells and solid tumors. Interestingly, prognostic evaluation was also realized with COF-survivin. This work will offer new insights into COF-based probes and inspire the development of more versatile tools for biomedical applications.Covalent organic frameworks (COFs) have emerged as a kind of promising material for analytical and biomedical purposes. However, simultaneous cancer diagnosis and therapy with COFs remain a challenge. We report here a COF-based theranostic nanoplatform by integrating a dye-labeled oligonucleotide onto porphyrin-based COF nanoparticles for highly efficient cancer diagnosis and therapy. The fluorescence of the dye was effectively quenched by the COF through fluorescence resonance energy transfer (FRET). In the presence of biomarker survivin mRNA, more stable duplexes were formed and separated from the COF NPs, enabling the recovery of the fluorescence signal and selective cancer imaging. Under NIR laser irradiation, COF NPs generated abundant reactive oxygen species (ROS) to induce cancer cell apoptosis owing to their crystalline reticular structure. Covalent organic frameworks (COFs), as a class of emerging crystalline porous polymeric materials, possess tremendous potential for application in a variety of fields owing to their facile design and well-defined structure.Photodynamic therapy (PDT), employing a specific laser to excite a photosensitizer (PS) to generate reactive oxygen species (ROS) and kill malignant cells, is highly spatiotemporally controlled and has been approved for clinical cancer treatment.Traditionally, cancer diagnosis and treatment are individual and separate processes.Herein, we developed a nanoscale COF-based theranostic nanoplatform. A nanoscale porphyrin-based COF was prepared and a TAMRA-labeled survivin antisense strand (TSAS) was integrated onto the COF NPs to give rise to the nanoplatform (termed COF-survivin). The crystalline reticular structure endowed the COF with better stability and higher ROS generation ability in aqueous solution than those of the porphyrin monomer, while the large planar structure composed of the strong \u03c0-electron system makes it easy to absorb DNA single strands and quench the fluorophore to form a stable nanoplatform. The TSAS could readily form a duplex structure with survivin mRNA , PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching band at 1660 nm is decreased, while a new peak at 1601 nm appeared corresponding to the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN stretching band, demonstrating the successful condensation between amino and aldehyde groups. Moreover, multiple intense peaks were observed in the PXRD pattern, indicating the successful preparation of crystal COF structures , one of the most toxic ROS,COF NPs were prepared based on a solvothermal strategy.s Fig. S1. The TEMs Fig. S1 and SEM s Fig. S1 results s Fig. S1 of COF Ns Fig. S1 of COF N1.000000,.000000 s\u20131 of different groups was determined. Prominent \u0394\u03a8m loss was detected in the therapy group as shown in Subsequently, the in vivo experiments were carried out. We first investigated whether the nanoplatform could differentiate tumor tissue from normal tissue. The result of in vivo fluorescence imaging by integrating a TAMRA-labeled survivin antisense oligonucleotide onto a nanoscale porphyrin-based COF. The crystalline structure characteristics of the COF endowed the nanoplatform with excellent stability and ROS generation capability. In the presence of cancer biomarker survivin mRNA, the readily formed duplex detached from the COF, which could restore the fluorescence by FRET prohibition and realize selective cancer imaging. Under NIR laser irradiation, the COF could generate abundant All the animal experiments were conducted and agreed with the Principles of Laboratory Animal Care (People's Republic of China) and the Guidelines of the Animal Investigation Committee, Biology Institute of Shandong Academy of Science, China.The authors declare no competing financial interest.Supplementary informationClick here for additional data file."}
+{"text": "Borata-alkenes can serve as anionic olefin equivalent ligands in transition metal chemistry. A chelate ligand of this type is described and used for metal coordination. 2P(CH2)2B(C6F5)2 frustrated Lewis pair in the \u03b1-CH[B] position gave the methylene-bridged phosphane/borata-alkene anion. It reacted with the [Rh(nbd)Cl] or [Rh(CO)2Cl] dimers to give the respective neutral chelate [Rh] complexes. The reaction of the \u2013 anion with [Ir(cod)Cl]2 proceeded similarly, only that the complex underwent a subsequent oxidative addition reaction at the mesityl substituent. Both the resulting Ir(iii)hydride complex 15 and the P/borata-alkene Rh system 12 were used as hydrogenation catalysts. The Rh(nbd) complex 12 served as a catalyst for arylacetylene polymerization.Borata-alkenes can serve as anionic olefin equivalent ligands in transition metal chemistry. A chelate ligand of this type is described and used for metal coordination. Deprotonation of the Mes PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB bond lengths around 1.45 \u00c5 were found in these systems. In addition, a variety of related boryl-carbanion \u2194 borata-alkene systems were in situ generated and employed as reagents e.g. in borata-Wittig olefination chemistry.3Carbanions in the \u03b1-position to boryl groups show a conjugative interaction with the adjacent Lewis acid. Such systems can be described as borata-alkenes. Borata-alkenes derived from some alkyldiarylboranes had previously been prepared.6F5)2 group resulted in a markedly increased \u03b1-CH acidity in the respective boranes. A DFT study had revealed that e.g. H3C\u2013B(C6F5)2 showed a pKa-value comparable to that of cyclopentadiene.3C\u2013B(C6F5)2 borane must be considered >10 pKa values more C\u2013H acidic than the related H3C-BMes2 borane. Consequently, R\u2013H2C\u2013B(C6F5)2 systems were easily deprotonated to give the corresponding \u2013 borata-alkene systems. Several of such systems were isolated as their Li+ salts. Some were used in borata-Wittig olefination reactions.It was recently shown that the presence of the strongly electron-withdrawing \u2013BC6F2 group r3-borata-allyl metal complexes and related systems known.et al. had prepared the borata-alkene tantalocene complex 4 scale\" fill=\"currentColor\" stroke=\"none\">B(C6F5)2]\u2013 ligand with the neutral \u03b72-olefin analogues. The Piers group developed some follow-up chemistry of complex 4.et al. have just recently described a conceptually related borata-phenanthrene gold complex.Neutral bora-alkene compounds had previously been used as ligandsomplex 4 9 and emp PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2\u2013 terminus by a Mes2P\u2013CH2-substituent now gave an anionic system that served as a chelate ligand in Rh and Ir coordination chemistry.Formal substitution of a hydrogen atom of the borata-alkene 7.2P-vinyl (5) with Piers' borane [HB(C6F5)2] (6)15We started our phosphane/borata-alkene chelate ligand synthesis from the ethylene-bridged frustrated P/B Lewis pair (FLP) 7 at the \u03b1-position to the boron atom by treatment with LDA . Compound 7 is \u03b1-CH acidic, but it is also an active boron Lewis acid that is able to abstract hydride from amines in the \u03b1-position to nitrogen with iminium salt formation.7 generated the respective imine. This is found as a component in the product 8 that we isolated from the reaction mixture as a white solid in 67% yield 2 backbone. The boron atom shows a pseudotetrahedral coordination geometry (\u03a3B1CCC 333.2\u00b0); it has hydride attached. The lithium cation shows contacts to the [B]-H moiety, the phosphorus atom and one ortho-C6F5 fluorine atom. The Li cation has the newly formed imine moiety N-coordinated. In solution compound 8 shows a 11B NMR [B]-H doublet at \u03b4 \u201318.4 with a 1JBH \u223c70 Hz coupling constant and a 7Li NMR (C6D6) signal at \u03b4 1.4. The \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCMe2 imine 13C NMR resonance occurs at \u03b4 173.5.We first attempted deprotonation of 7% yield . Compounanalysis . It show7 with the LiTMP reagent, a base that has no CH groups \u03b1 to nitrogen. The reaction was carried out with the in situ generated FLP 7. Treatment with LiTMP in pentane for 16 h at room temperature followed by workup gave the methylene-linked phosphane/borata-alkene product 9 \u00c5, which is much shorter than the adjacent boron-aryl bonds (B1\u2013C31: 1.607(3)\u00c5, B1\u2013C41: 1.602(3)\u00c5). The boron coordination geometry in compound 9 is trigonal-planar (\u03a3B1CCC 360.0\u00b0). The B1\u2013C2\u2013C1 angle amounts to 126.4(2)\u00b0. The lithium ion in 9 shows contacts to the borata-alkene unit as well as to the phosphorus atom and one ortho-C6F5 fluorine atom. The lithium atom Li+ also has the HTMP amine ligand bonded to it that had been formed in the deprotonation process (Compound process .8) compound 9 features a typical borata-alkene 11B NMR signal at \u03b4 18.6. The 31P NMR signal is at \u03b4 \u201320.6 and the \u2013CH2\u2013CH PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t backbone shows 1H NMR resonances at \u03b4 4.21 ) and \u03b4 3.36 . The 19F NMR spectrum of compound 9 shows two sets of o,p,m-resonances of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB(C6F5)2 moiety .In solution 2 reagent.10 (isolated as a yellow solid in 52% yield). It was characterized by C,H-elemental analysis, by spectroscopy and by its reaction with dihydrogen (see below). Compound 10 is a typical intramolecular FLP, showing a P\u2013B interaction with one boron atom and having the other one free. However, the temperature dependent 19F NMR spectrum showed exchange between the pair of B(C6F5)2 groups at e.g. 299 K. Only at low temperature (e.g. 203 K) we observed a set of three broad 19F NMR resonances of a free trigonal planar B(C6F5)2 unit and a set of ten separate signals of the rotationally hindered P\u00b7\u00b7\u00b7B(C6F5)2 group. The 31P NMR (299 K) signal of compound 10 is at \u03b4 16.3 and the \u2013CH2\u2013CH PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t backbone shows 1H NMR features at \u03b4 3.55 and \u03b4 4.30, respectively ).We briefly investigated the nucleophilic property of the borata-alkene unit in compound 10 reacted rapidly with dihydrogen under mild conditions to give the phosphonium/hydridoborate dihydrogen splitting product 11 (isolated as a solid in 71% yield). The X-ray crystal structure analysis (CCC 339.7\u00b0) and the newly formed hydride-bridged bis-borane moiety. In solution (CD2Cl2) the phosphonium [P]-H unit showed up at \u03b4 7.58 (1H NMR) and \u03b4 \u20133.7 , respectively. We recorded a broadened 11B NMR signal at \u03b4 \u201318.1 with a corresponding broad 1H NMR [B](\u03bc-H) feature at \u03b4 5.45. The 19F NMR spectrum of compound 11 shows two equal-intensity sets of o,p,m-C6F5 signals of the pair of B(C6F5)2 groups and we observed the 1H/13C NMR signals of the \u2013CH2\u2013CH backbone at \u03b4 2.84/27.8 (PCH2) and \u03b4 1.80/7.6(br)(BCH), respectively.Compound analysis showed t9 as a chelate ligand in Rh chemistry. For that purpose, we treated the (norbornadiene)RhCl dimer with the prefabricated borata-alkene reagent 9 for 18 h in toluene solution at room temperature. Workup then gave the respective neutral chelate phosphane/borata-alkene(norbornadiene)Rh complex 12 in >60% yield scale\" fill=\"currentColor\" stroke=\"none\">B system serves as a chelate ligand. It is unsymmetrically \u03b72-coordinated through both backbone atoms of the borata-alkene moiety and \u03baP-bonded to the attached phosphanyl group. As the P/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB ligand is mono-anionic, the resulting Rh complex is neutral. The C2\u2013B1 bond is only marginally elongated, it is still within the typical C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB distance of borata-alkene examples12 the phosphane donor exhibits a stronger structural trans-effectWe used the methylene-bridged phosphane/borata-alkene anion of the lithium salt 0% yield . Suitabl0% yield . Compoun12 shows a 31P NMR signal (CD2Cl2) at \u03b4 \u201389.0 with a 1JRhP \u223c 120 Hz coupling constant. This changed only marginally when the spectrum of 12 was recorded in d8-THF solution. Compound 12 shows a 11B NMR signal at \u03b4 24.3, a value that is similar to that of the uncomplexed borata-alkene anion 9 (see above).19F NMR spectrum of 12 shows two sets of o,p,m-C6F5 signals for the pair of pentafluorophenyl substituents at boron. We observed the 1H NMR signals of the chelate ligand backbone at \u03b4 4.14/3.90 (PCH2) and \u03b4 3.68 scale\" fill=\"currentColor\" stroke=\"none\">CH\u2013), respectively ), and there are the 1H/13C NMR signals of the coordinated norbornadiene ligand at rhodium Rh dimer was carried out at r.t . Workup involving extraction with pentane and crystallization gave the neutral chelate [P/borata-alkene]Rh(CO)2 complex 13 as a yellow crystalline solid in 46% yield. The X-ray crystal structure analysis scale\" fill=\"currentColor\" stroke=\"none\">B unit . Compound 13 shows strong IR CO bands at \u03bd = 2069 and 1997 cm\u20131.2Cl2 solution it shows a 11B NMR signal at \u03b4 27.3, i.e. in the typical borata-alkene range. The 31P NMR resonance was located at \u03b4 \u2013105.0 with a 1JRhP = 88.5 Hz coupling constant. The borata-alkene unit in complex 13 shows 19F NMR signals of a pair of inequivalent C6F5 substituents at boron.The reaction of the P/borata-alkene lithium salt analysis showed a9 and the iridium(cyclooctadiene)chloride dimer was carried out similarly . It gave a slightly different outcome. We assume that initially a Ir(cod) complex 14 was generated, analogous to the formation of the Rh system 12. However, it was apparently not persistent under the prevailing reaction conditions but underwent intramolecular C\u2013H bond activationortho-methyl group of a mesityl substituent at phosphorus to give the oxidative addition product 15 .The reaction between the borata-alkene reagent oduct 15 . It was 15 revealed that the iridium atom has undergone oxidative addition at a mesityl group at phosphorus, with formation of a new benzylic \u2013CH2\u2013Ir\u2013H moiety the iridium complex 15 shows four olefinic 1H NMR signals of the coordinated cyclooctadiene ligand. It also features four arene CH 1H NMR signals of the mesitylene and the CH-activated Mes substituents at phosphorus. Complex 15 shows a broadened 11B NMR resonance at \u03b4 \u201317.5. The 31P NMR signal is observed at \u03b4 \u2013104.0. It shows coupling to the Ir\u2013H moiety (2JPH \u223c 70 Hz).\u03b4 \u201310.4 with ca. 70 Hz coupling to phosphorus complex 15 was actually formed by an oxidative addition reaction at a mesityl methyl group at the stage of the analogous intermediate 14. We carried out some preliminary investigation toward the use of the new chelate phosphane/borata-alkene complexes in catalysis. For this reason, we performed two sets of catalytic reactions using either of the complexes 12 and 15. We first turned to alkene and alkyne hydrogenation catalysis.15 to dihydrogen revealed the stoichiometric formation of cyclooctane, the reduction product of the cod ligand of the Ir complex 15. Consequently, we employed compound 15 as a catalyst in our hydrogenation experiments. The hydrogenation of styrene is a typical example. With both 1 or 0.5 mol% of 15 quantitative hydrogenation to ethylbenzene was achieved analogue of the Rh complex 12 (see above).Our study has shown that the methylene linked phosphane/borata-alkene anion of the salt achieved ; with 0.15 derived catalyst system with 1 mol% of vinylcyclohexane or cyclohexene, as well. The more sterically encumbered 1-methylcyclohexene substrate gave only a 39% conversion under these conditions and phenylacetylene eventually furnished a ca. 3\u2009:\u20091 mixture of styrene and ethylbenzene with a combined conversion of 77% after 16 h.Quantitative alkene hydrogenation was found at the 12 under our standard conditions . The bulkier 1-methylcyclohexene was not hydrogenated at the Rh catalyst system 12 under our typical conditions.Styrene was quantitatively hydrogenated to ethylbenzene with 0.5 mol% of the Rh catalyst nditions . With 0.12 or 15, but we presently cannot rule out an alternative \u201cFLP-like\u201d metal/borane dihydrogen splitting reaction.24So far we assume a conventional pathway of dihydrogen activation at the metal centre in the complexes 12.12 was carried out in the non-polar solvent benzene or in ethereal solution (diethylether or tetrahydrofuran). We carried out the phenylacetylene polymerization at room temperature for a duration between 30 min (in ether) or 2 h (in benzene). With decreasing catalyst amounts an almost quantitative amount of polyphenylacetylene was isolated from the reaction in benzene. Even with 0.025 mol% as well as 0.01 mol% of the catalyst poly(phenylacetylene) was isolated, albeit in lower yields . The obtained polymer was similar in appearance (yellow to orange solids) as the poly(phenylacetylene) obtained by Noyori et al. at the remotely related neutral [(Ph3P)n(nbd)Rh-CCPh] (n: 1 or 2) derived catalysts, so we assume it has a similar structure.p-fluorophenylacetylene and p-methoxyphenylacetylene at the catalyst system 12 (0.1 mol%) and isolated the respective polyacetylenes in close to quantitative yields sample was characterized by MALDI-TOF mass spectrometry, which showed the regular sequence of signals separated by the mass of the respective monomer unit of 132 (depicted in the ESIp-anisylacetylene) sample obtained in ether with the Rh complex 12 derived catalyst we found a molecular weight of Mn \u2265 100000. The respective poly(phenylacetylene) sample had an about twice as high Mn, and the poly(p-fluorophenylacetylene) had the highest measured Mn in the series of >400000 scale\" fill=\"currentColor\" stroke=\"none\">B(C6F5)2\u2013 ligand was generated by a typical organometallic reaction pathway within the coordination sphere of the metal . Since we had found about the vastly increased \u03b1-CH acidity of the B(C6F5)2 boranes2C,B-borata-alkene complexes has become evident: deprotonation2\u2013CH2\u2013B(C6F5)2 borane gave the borata-alkene in an independent initial step. Our syntheses of the methylene-bridged chelate phosphane/borata-alkene Rh and Ir complexes serve as examples of this development. The complexes are readily prepared, although the Ir system undergoes a subsequent rearrangement reaction. This new approach will probably allow for some variation on the ligand side, and it may open pathways to choosing variations on the metal side. The P/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB ligands in the here reported complexes do not interfere with catalytic features in our examples. To us this indicates that the readily available borata-alkenes might see useful applications as polar alkene ligand analogues in organometallic and coordination chemistry as well as in catalysis.Our study has shown that the seminal study published by Piers There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The first broad spectrum dendralene synthesis permits the widest structural and substituent variation and promotes applications in step economic synthesis. E)/(Z)-stereoselective syntheses of dendralenes are reported (twenty-eight examples). The approach involves twofold Pd(0)-catalyzed Negishi couplings of 1,1-dibromoalkenes with alkenylzinc reagents, and exploits both substrate- and catalyst-controlled aspects of chemo-, regio- and stereoselectivity in the two C(sp2)\u2013C(sp2) bond forming steps. The value of the new hydrocarbons in rapid structural complexity generation is demonstrated through their deployment in unprecedented diene- and triene-transmissive pericyclic reaction sequences.The first general synthetic approach to substituted [3]- and higher dendralenes is reported. Fifty-one mono- through to penta-substituted dendralenes carrying alkyl-, cycloalkyl-, alkenyl-, alkynyl-, aryl- and heteroaryl-substitutents are accessed, and the first ( We provide solutions that are of broad scope, allowing selective access to both E- and Z-diastereomers of an internally-substituted dendralene from the same 1,1-dibromoalkene precursor.Building upon the foundations of previous, narrow-scope cross-coupling methods for dendralene synthesis, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. Thus, 1,1-dibromoalkenes 1 undergo twofold Negishi C(sp2)\u2013C(sp2) coupling2, where the two newly introduced alkenyl substituents are the same. 1 and four different alkenyl nucleophiles, to demonstrate the broad scope of this lynchpinThe first group of [3]dendralenes reported here lack stereogenicity about the central C2a\u2013w with substitution at all possible sites on the dendralene framework. Substituents incorporated at the central methylene position of the [3]dendralene (substituents colored blue in 2(dppf)] was superior for twofold cross-coupling.The twofold Negishi cross-coupling protocol works well with vinylzinc bromide and its alkyl and aryl-substituted congeners, to access mono- to penta-substituted [3]dendralenes 1 with different alkenylzinc reagents. It is well established that aldehyde-derived 1,1-dibromoalkenes undergo chemo- and regio-selective single cross-coupling with an alkenyl nucleophile to replace the bromine trans- to the carbon-based substituent (1 \u2192 3).18To achieve the first diastereoselective synthesis of dendralenes, we envisioned two successive cross-couplings of a 1,1-dibromoalkene stituent , 1 \u2192 3.13)4] was the most consistent performer in the trans-selective mono-coupling of 1,1-dibromoalkenes (1 \u2192 3). In all but one case examined, a clear preference for the mono-coupled product was observed and, in every case, only the (1Z)-2-bromo-1,3-butadiene diastereomer was detected.e.g. stoichiometry of coupling partners, temperature) for optimal results. In our hands, as catalyst. We are delighted to report that the same ligand also brings about Pd(0)-catalyzed stereo-retentive cross-couplings of (1Z)-2-bromo-1,3-dienes with alkenyl nucleophiles to permit the first stereoselective dendralene synthesis (3 \u2192 4).Negishi reported that cross-couplings of the resulting -2-bromo-1,3-butadienes. Inconsistent with Negishi's findings, however, are couplings of alkyl-substituted systems , which generally give mixtures of E and Z-diastereomers in the second cross-coupling (see ESI2(dppf)] as pre-catalyst, which proceed with stereochemical inversion3 \u2192 4).Consistent with the results of the Negishi group with non-olefinic nucleophiles,t-Bu3P-catalyzed stereo-retentive cross-coupling (2(dppf)] pre-catalyst in which the order of addition of the two non-equivalent alkenyl-zinc bromides is reversed. As shown in Overall, the sequence involving Pd(0)/coupling has broacatalyst . NineteeZ4e- and Z4l- sequences to form octalins. The present work significantly extends the scope of the DTDA process since, as we demonstrate here for the first time in Z4a- and E4a- reacts with the dienophile N-methylmaleimide with complete selectivity for the 1,3-butadiene site that lacks the inside-1,3-butadiene R substituent.Z4a- gives semicyclic diene 6, which reacts on, in situ, with a second NMM molecule to furnish 1-methyl-\u03941(9)-octalin 7 as the major product. The semicyclic diene 8 derived from diastereomeric dendralene E4a- undergoes a second NMM cycloaddition under high pressure conditions to form 10-methyl-\u03941(9)-octalin 9, possessing an angular methyl substituent. Octalin and decalin ring systems are extremely common structural motifs in natural products and medicinal agents.22Thus, each diastereomeric [3]dendralene Z10a-, by simply deploying 2-zinc bromide as a coupling partner scale\" fill=\"currentColor\" stroke=\"none\">C unit of [4]dendralene Z10a- is essential for the first twofold, triene transmissive 6\u03c0\u20136\u03c0 electrocyclization sequence (Z10a- \u2192 11 \u2192 12). The execution of a pair of electrocyclizations in this interconnected manner is without precedent. Several variations upon this original theme can be envisaged, which has potential for development into a broad scope, new method for step economic polycycle synthesis.The freshly minted PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC through-conjugation, as evidenced by the preparation of 23 new compounds containing this feature. We venture that the findings described herein, when combined with the strategies recently introduced for the preparation of the unsubstituted higher [n]dendralenes (n = 5\u201312),In conclusion, the first broad-spectrum synthesis of substituted dendralenes has been demonstrated, and unprecedented domino sequences for polycycle construction proven. [3]Dendralenes bearing from one to five alkyl, cycloalkyl, alkenyl, alkynyl, aryl and heteroaryl substituents have been prepared. Substitution at every conceivable position on the [3]dendralene framework has been realized. The previously unsolved problem of diastereoselective synthesis of internally-substituted systems has been solved. The method has been shown to work also with 4]dendralenes. Importantly, the approach represents the first general synthesis of dendralenic structures with extended CdendralenThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Tailoring the graphene-covered Fe with Cs modifies the surface electronic properties of the catalysts such that selective C\u2013O bond cleavage of phenol is achieved in liquid phase by inhibiting the facile tautomerization followed by ring saturation. i.e., selective removal of oxygen without aromatic ring saturation) under liquid-phase conditions is highly challenging. Here, we report an efficient approach to engineer earth-abundant Fe catalysts with a graphene overlayer and alkali metal , which produces arenes with 100% selectivity from liquid-phase hydrodeoxygenation (HDO) of phenolics with high durability. In particular, we report that a thin (a few layers) surface graphene overlayer can be engineered on metallic Fe particles (G@Fe) by a controlled surface reaction of a carbonaceous compound, which prevents the iron surface from oxidation by hydroxyls or water produced during HDO reaction. More importantly, further tailoring the surface electronic properties of G@Fe with the addition of cesium, creating a Cs-G@Fe composite catalyst in contrast to a deactivated Cs@Fe one, promotes the selective C\u2013O bond cleavage by inhibiting the tautomerization, a pathway that is very facile under liquid-phase conditions. The current study could open a general approach to rational design of highly efficient catalysts for HDO of phenolics.Development of inexpensive sulfur-free catalysts for selective hydrogenolysis of the C\u2013O bond in phenolics ( Since its discovery,5i.e., removing oxygen-containing functional groups from bio-oil. During the HDO of phenolics, selective removal of the oxygen without saturation of the aromatic ring not only minimizes the consumption of valuable hydrogen, but also produces a gasoline blending stock with high octane number, which is critical to the efficient upgrading of bio-oil.via tautomerization.17Hydrodeoxygenation (HDO) plays pivotal roles in biomass conversion, 2 (H2-TPSR), in situ X-ray photoelectron spectroscopy (XPS), and in situ attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) reveal that the thin graphene overlayer prevents the Fe surface from oxidation, making the graphene/Fe composite (G@Fe) a durable Fe-based catalyst resistant to oxidation in HDO of phenol. More importantly, upon modification of this graphene/Fe composite with an alkali metal , the graphene overlayers could also regulate the Fe\u2013alkali metal interactions. As such, rather than a poison of Fe surface on Cs@Fe, tailored surface electronic properties were observed on the Cs-G@Fe composite, leading to exclusive arene production in HDO of phenolics in liquid phase via inhibiting tautomerization and aromatic ring saturation of phenolics.Motivated by the protection of transition metals by graphene overlayerI2D/IG ratio and the width of 2D band2 bonding.2/N2. If the Fe surface is not fully covered by the graphene overlayers, oxidation of Fe by O2 would be inevitable. From 2-TPSR profiles of the Fe and G@Fe samples after oxygen exposure . For the Fe sample, formation of surface iron oxides after exposure to oxygen was confirmed by both Raman . In contrast, both Raman for the selective C\u2013O bond cleavage, as suggested by homogeneous catalysis for the selective hydrogenolysis of aromatic ethers,The G@Fe catalyst was synthesized with a chemical vapor deposition method reported elsewhere,n Fig. S4 and H2-Tn Fig. S4 and H2-TS42-TPSR charactein situ pretreatment with H2 at 300 \u00b0C (simulating the surface under HDO reaction). Over G@Fe, C 1s spectrum displays a peak at 284.8 eV dominate on these catalysts under the liquid-phase conditions. Herein, using phenol as a probe molecule, we evaluated the bare Fe (BET surface area: 9.2 m2 g\u20131), G@Fe (BET surface area: 4.5 m2 g\u20131) and Cs-G@Fe (BET surface area: 4.5 m2 g\u20131) in liquid-phase HDO. As shown in via a mediated Fe\u2013alkali metal interaction, the reason of which remains unclear and subjects to further studies. Regardless, we first applied a similar approach used in homogeneous catalysis to the heterogeneous analogues and achieved the selective C\u2013O bond cleavage of phenolics in HDO. It should be mentioned that the addition of alkali metal resulted in the decrease of apparent rate for benzene production as shown in st cycle, the catalyst remained relatively stable afterwards for 4 additional testing cycles. More importantly, the benzene selectivity remained at 100% in all the tested cycles. It should also be mentioned that, due to the magnetic nature of the catalyst, the catalysts can be readily separated from the liquid phase by applying a magnetic field as demonstrated in the cyclic stability tests of a reaction.Ea of the reactions on the G@Fe and Cs-G@Fe (Ea of HYD (89 kJ mol\u20131) is much lower than that of DDO (143 kJ mol\u20131). This is consistent with the higher bond dissociation energy of Caromatic\u2013Oi.e. Cs significantly increased Ea for ring saturation) and the apparent Ea of direct C\u2013O bond cleavage is 141 kJ mol\u20131 which is comparable with that of DDO on G@Fe (143 kJ mol\u20131). This implies that Cs may not be directly involved in C\u2013O bond cleavage, but instead, is primarily responsible for inhibition of the ring-saturation pathway.The binding energy of Fe is lowered by 0.6 eV after adding Cs, as shown in Cs-G@Fe . The rea Cs-G@Fe . Over G@Ea for DDO remains the same after Cs addition, it is hypothesized that the addition of Cs largely inhibits the tautomerization reaction pathway but has a minimal effect on the C\u2013O bond cleavage. To further verify this hypothesis, in situ ATR-FTIR was employed to investigate the phenol adsorption over G@Fe and Cs-G@Fe. As shown in \u20131 (stretching vibrations of the aromatic ring)\u20131 (stretching vibration of the C\u2013O bond),\u20131, which can be assigned to stretching vibration of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond,2 , and depositing Cs may selectively block the one for tautomerization with the other one being exposed to phenol for C\u2013O cleavage. To test this hypothesis, we further compared the performances of other alkali metal doped catalysts with same molar loading is well correlated with the capability of electron donation of alkali metali.e. graphene-covered Fe) may play pivotal roles to inhibit the functionality for catalyzing tautomerization of phenol. While allowing the electron tunneling, graphene overlayers may mediate the interaction between Fe and alkali metal/substrate oxygen to prevent Fe from deactivation.Previous resultsC bond,2 of surfa Fig. S12. Given ti.e., phenol). To our best knowledge, this is the first sulfur-free inexpensive catalyst reported for exclusive hydrogenolysis of the C\u2013O bond in phenolics under liquid-phase conditions. Moreover, the catalyst also offers other beneficial properties, i.e. magnetic material for a facile separation from reaction slurry, making it a promising catalyst for liquid-phase reactions. This work could also lead to a general methodology for rational design of heterogeneous catalysts for selective HDO of oxygenates.Our results present an approach to protect Fe with graphene and further tune the G@Fe catalyst with alkali metal for selective hydrogenolysis of C\u2013O bond in HDO of phenol. Graphene overlayers on Fe protect Fe from oxidation while, at the same time, maintaining the nature of Fe as confirmed by its catalytic activity resembling that of bare Fe. More importantly, analogous with homogeneous catalysis, alkali metals such as Cs could be added to tailor the surface electronic properties of G@Fe, leading to the selective inhibition of tautomerization and thus exclusive C\u2013O bond cleavage in the heterogeneously catalyzed HDO of phenolics (There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Unprecedented photoluminescence, AIE and heat-induced emission characteristics of non-conjugated thermoresponsive PNVCL were unveiled for the very first time which eventually empowered PNVCL to act as an intracellular thermometer. N-vinylcaprolactam) (PNVCL) devoid of any classical fluorophore entity. PNVCL underwent a coil to globular conformational transition in an aqueous medium and appeared to be fluorescent above its lower critical solution temperature (LCST) near body temperature (38 \u00b0C). Eventually, this intriguing aspect enabled higher cellular uptake of PNVCL at the LCST boundary. By virtue of the AIE effect, the thermo-induced aggregation phenomenon has been ingeniously utilized to apply PNVCL as a novel fluorescent thermometer for intracellular temperature determination.Since temperature is one of the most significant physiological parameters that dictate the cellular status of living organisms, accurate intracellular temperature measurement is crucial and a valuable biomarker for the diagnosis and treatment of diseases. Herein, we introduce the foremost example of a non-conjugated polymer as a next generation fluorescent thermometer which is capable of addressing the key shortcomings including toxicity and thermal-induced fluorescence quenching associated with \u03c0\u2013\u03c0 conjugated system-based thermometers developed so far. We revealed, for the first time, the unique photophysical and aggregation-induced emission (AIE) characteristics of well-known thermoresponsive poly( Temperature is an important physiological parameter that governs a broad range of biological activities, especially all biological reactions within living cells.In this context, an astonishing evolution of numerous fluorescent thermometers has been witnessed over the past few years.11The discovery of the aggregation-induced emission (AIE) phenomenon by Tang's group20 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN functionalities, have been reported to act as nonconventional luminophores upon aggregation or clustering.N-vinylcaprolactam) (PNVCL) is expected to exhibit interesting photophysical behavior. As anticipated, for the very first time, we have revealed the intrinsic photoluminescence characteristics of well-known thermo-responsive PNVCL and its AIE activity. The temperature-driven aggregation behavior and AIE characteristics have judiciously been exploited to use PNVCL as a potential fluorescent polymeric thermometer for intracellular temperature measurement. Overall, the present non-conjugated macromolecule has the ability to replace the current traditional-fluorophore functionalized fluorescent polymeric thermometer, because PNVCL has multiple fascinating features such as AIE, temperature-sensitive fluorescence enhancement, and excellent cytocompatibility, which are rare in a single polymeric system.Electron-rich heteroatoms, such as nitrogen, oxygen, phosphorous, sulfur, and/or unsaturated CN-vinylcaprolactam (1H NMR spectroscopy and size exclusion chromatography (SEC) were employed to characterize PNVCL. A typical 1H NMR spectrum shown in Fig. S1Mn,SEC) of 9500 g mol\u20131, with dispersity (\u00d0) = 1.95 , dioxane, methanol (MeOH), ethanol (EtOH), acetone, etc., except in hexane. Moreover, the polymer was soluble in aqueous media owing to the strong H-bonding between the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups of lactam and water molecules.Initially, PNVCL was synthesized in one step by conventional free radical polymerization (FRP) of commercially available rolactam . 1H NMR 5 Fig. S2. PNVCL w\u03bbex) of 339 nm in different solvents to understand their emission characteristics. As illustrated in Fig. S4,\u20131) exhibited stronger fluorescence in THF than in any other common organic/aqueous solvents. Thus, PNVCL possessed a higher quantum efficiency (\u03c6F at \u03bbex 350 nm) and average fluorescence lifetime ( 350 nm) and average fluorescence lifetime (\u3008\u03c4\u3009) in THF in THF than in water yielded a low photoluminescence (PL) signal with an almost flat line parallel to the abscissa and obviously no emission was observed upon irradiation to the good solvent (THF) containing the polymer, without increasing the polymer concentration Fig. S5. A dilutadiation . But wit mg mL\u20131 . A simil mg mL\u20131 , with a mg mL\u20131 . As the mg mL\u20131 . This contration . The higolutions .i.e. any sort of \u03c0-conjugated system, it produces bright blue emission in the concentrated or aggregated state. This fact can be attributed to the clustering-triggered emission (CTE) mechanism. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN, etc. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups with \u03c0-electrons/a lone pair of electrons and N atoms with a lone pair of electrons of one cyclic amide come in close proximity to another amide to form a cluster in the aggregated state. This clustering results in chromophores with effective through-space electronic communication giving rise to extended electron delocalization and simultaneous rigidified conformation. The rigidity of the molecular conformation restricts vibration and molecular rotation which efficiently suppresses the non-radiative relaxation.Although the present polymer lacks conventional chromophores, Notably, progressive enhanced absorption with red shifting of absorption maxima was observed as the polymer concentration increased , indicat\u03bbex values of 365 (UV), 460 (blue) and 530 nm (green) was consistent with the preceding observations , where there is more opportunity for the chromophores to approach closer and provide discernible emission. Surprisingly, direct observation of the PNVCL film under a fluorescence microscope showed tunable photoluminescence from blue and green to red upon altering the emission channels . Furtherinset of . Apart fvia UV-Vis spectroscopy.T) was observed until 35 \u00b0C; an abrupt decrease due to the LCST was observed at 37.5 \u00b0C scale\" fill=\"currentColor\" stroke=\"none\">O groups of lactam units and O\u2013H groups of water molecules at a higher temperature.Dh) of the polymer in response to heat were assessed by DLS measurements below and above the LCST. The Dh values in the temperature window 25\u201335 \u00b0C (below the LCST) were found to be 6\u20138 nm and increased up to 170\u20131000 nm above the LCST and normal lung epithelial cells (WI-38) by performing MTT assay in a dose-dependent manner Fig. S9. The celi.e. 38 \u00b0C . Cultured cells after treatment with PNVCL were incubated for 24 h at 25, 35, and 38 \u00b0C . The CLSe. 38 \u00b0C , when obe. 38 \u00b0C . Howevere. 38 \u00b0C .As shown in \u20131 for different incubation times followed by staining of nuclei using DAPI (blue emission). At 38 \u00b0C (above the LCST) and at a fixed polymer concentration (250 \u03bcg mL\u20131), with an increasing incubation time ranging from 4 to 24 h the average emission intensity obtained from MCF-7 cells observed under the green channel was found to increase , it exhibited significant emission upon increasing the concentration, and also in the solid and film state. This unprecedented light emission could be attributed to the AIE or CTE mechanism. Interestingly, the PNVCL film displayed distinct blue, green and red emission upon illumination with different excitation wavelengths, demonstrating the coexistence of multiple emissive species with different energy levels. Moreover, the PNVCL solution exhibited a bright blue emission upon heating above its LCST (37.5 \u00b0C), which was attributed to the heat-assisted aggregation-induced emission phenomenon. Capitalizing on the aforesaid aspects, a higher cellular internalization of PNVCL was attained at 38 \u00b0C (above the LCST) compared to 35 \u00b0C (below the LCST) with significant light-up fluorescence confirmed through CLSM images. We believe that the present findings disclosed the potentiality of the non-toxic biocompatible PNVCL to be a next generation fluorescent thermometer by detecting minor temperature changes, beneficial for the early detection of diseases and local hyperthermia treatment.40In summary, unique emission behaviour of non-conjugated PNVCL without traditional chromophores has been investigated. Although PNVCL is non-fluorescent in dilute solution (up to 0.1 mg mLThere are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Catalytic bicyclization of 1,5-enynes anchored by \u03b1,\u03b2-conjugates with arylsulfonyl radicals was established using TBAI and Cu(OAc)2 as co-catalysts. in situ from sulfonyl hydrazides has been established using TBAI (20 mol%) and Cu(OAc)2 (5 mol%) as co-catalysts under convenient conditions. In addition, the use of benzoyl peroxide (BPO) as the oxidant and pivalic acid (PivOH) as an additive was proven to be necessary for this reaction. The reactions occurred through 5-exo-dig/6-endo-trig bicyclizations and homolytic aromatic substitution (HAS) cascade mechanisms to give benzo[b]fluorens regioselectively. A similar catalytic process was developed for the synthesis of \u03b3-ketosulfones. These reactions feature readily accessible starting materials and simple one-pot operation.A catalytic bicyclization reaction of 1,5-enynes anchored by \u03b1,\u03b2-conjugates with arylsulfonyl radicals generated Herein,s (HASs) .p-tolyl)prop-2-en-1-one 1a was selected as a benchmark substrate to investigate the additions by sulfonyl radicals. With 20 mol% tetrabutylammoniumiodide (TBAI) as the catalyst, the reaction of substrate 1a with tosylhydrazide 2a was performed in CH3CN in the presence of benzoperoxide (BPO) (4.0 equiv.) as an oxidant at 70 \u00b0C under air conditions, affording the expected benzo[b]fluorens 3a, albeit with a low yield of 18% (3CN showing the best performance (entries 2\u20134). Raising the reaction temperature to 100 \u00b0C slightly ameliorates the yield of 3a (entry 5). A subsequent investigation of other catalysts was conducted in CH3CN. As illustrated in entries 6\u20138, different types of catalysts including I2, KI, and CuI were employed in the model reaction, and it turned out that I2 and KI hardly facilitate the reaction (entries 6 and 7), while CuI as a catalyst only led to a poor yield of 16%. Next, we turned our attention to evaluating different additives (entries 9\u201311). We found that the addition of PivOH (1.0 equiv.) delivered 3a in a 35% yield (entry 11). Notably, the reaction of 1a and 2a in the presence of 2.0 equiv. of PivOH gave 3a in a 71% yield using a co-catalyst of TBAI (20 mol%) and Cu(OAc)2 (5 mol%) with complete consumption of the starting material 1a (entry 15). Without PivOH, the yield of the expected product 3a decreased remarkably (entry 17). Further screening of other oxidants, such as TBHP (64% yield), DTBP (very poor yield) and H2O2 (no product) for this transformation showed that BPO was the best choice phenyl)-1- at the para position of the aromatic ring (Ar1) directly bound to the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond gave the corresponding sulfonated products 3e and f in 55% and 68% yields, respectively. Alternatively, a naphthalen-1-yl substituent linked to the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond was also well-tolerated, affording the product 3g in a 60% chemical yield. Similarly, either electron-donating (methyl) or electron-withdrawing (bromo) groups (R1) at the para position of the phenyl ring tethered to the enone unit were well-suited for these radical 1,5-enyne-bicyclizations (3a\u20133k). 1,5-Enynes 1 carrying electron-neutral groups were also smoothly converted into the corresponding sulfonated benzo[b]fluorens 3l\u20133n in 39\u201367% yields. Notably, 2-naphthalenylethanone-derived 1,5-enynes furnished the unprecedented pentacyclic indenophenanthren-7-ol 3n in a 67% chemical yield though sulfonyl radicals triggered the 1,5-enyne-bicyclization. Unfortunately, a bulky ortho-Br substituent and benzylsulfonyl hydrazide did not work at all (3o and 3p). Besides the NMR and HR-MS spectroscopic analysis for benzo[b]fluorens 3, the X-ray diffraction for product 3f has been performed as shown in With the optimized reaction conditions in hand, we examined the substrate scope of the sulfonyl hydrazides nynes 1a . As antib]fluorens 3, we reasoned that in the absence of alkyne moieties, chalcones 4 would be able to accept sulfonyl radicals via typical 1,4-additions, which would expand their utility for the synthesis of \u03b3-ketosulfones. We thus explored this possibility through a one-pot reaction of (4-chlorophenyl)-3-phenylprop-2-en-1-one (4a) with 2a under the conditions described above. The expected \u03b3-ketosulfone 5a was obtained but with a lower yield (15%) initially. After careful optimizations were performed, we found that although Cu(OAc)2 and PivOH did promote this catalytic process, the use of co-oxidants of BPO (2.0 equiv.) and TBHP in 20 mol% of TBAI proved to be suitable for the current hydrosulfonylation, furnishing product 5a in a 77% yield. Subsequently, we further studied the reaction scope by reacting arylsulfonyl hydrazides 2 with various chalcones 4 under these conditions was proven not to be an adaptable substrate for this reaction, which may be ascribed to the relative instability of the sulfonyl radicals generated in situ from aliphatic sulfonyl hydrazides. Joining previously reported work,In view of our success with the synthesis of functional benzofluoren product 6 (eqn (3)). These control experiments suggest that BPO is essential for the catalytic cycles and the in situ generated sulfonyl radical triggers a 5-exo-dig/6-endo-trig bicyclization cascade.To understand the mechanism, several control experiments were conducted. The treatment of 1,5-enyne A from the sulfonyl hydrazide using the benzoyloxy radical generated in situ from the I\u2013 anion-assisted decomposition of BPO. The intermolecular addition of the resulting sulfonyl radical A and the 1,5-conjugated enyne 1 followed by a 5-exo-dig cyclization gives intermediate B, in which the homolysis of carbon\u2013copper(iii) affords vinyl radical C. Intermediate C is converted into aryl radical Dvia a 6-endo-trig cyclization. Intermediate D undergoes SET (single electron transfer) oxidation and subsequent deprotonation to provide intermediate F. The tautomerization of F leads to the formation of benzo[b]fluorens 3. Although the generation of sulfonyl radicals triggered by various oxidants has been achieved well,via sulfonyl radical initiated bifunctionalization of enynes is very rare in organic chemistry as mentioned earlier.On the basis of the above observations and those reported in literature,in situ generated sulfonyl radicals across the activated double bond is able to trigger a cascade 5-exo-dig/6-endo-trig bicyclization and HAS sequence, delivering tetracyclic sulfonylated benzo[b]fluorens in a successive C\u2013S and C\u2013C bond-forming process. Using chalcones as replacements for 1,5-conjugated enynes, this reaction enables the hydrosulfonylation of alkenes to form \u03b3-ketosulfones with good to excellent yields. These two methods allow easy access to important functional sulfones for potential applications in organic and medicinal chemistry.In summary, we have discovered new 1,5-enyne-bicyclization and hydrosulfonylation reactions of \u03b1,\u03b2-conjugates under convenient co-catalytic conditions. The addition of Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Azulene is a convenient platform for accessing heterobimetallic complexes and self-assembled monolayers of a \u03c0-linker with asymmetric junctions. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) terminated conducting \u03c0-linkers are often employed in the ever-growing quest for organoelectronic materials. While such systems typically involve symmetric dimercapto or diisocyano anchoring of the organic bridge, this article introduces the chemistry of a linear azulenic \u03c0-linker equipped with one mercapto and one isocyano terminus. The 2-isocyano-6-mercaptoazulene platform was efficiently accessed from 2-amino-6-bromo-1,3-diethoxycarbonylazulene in four steps. The 2-N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC end of this 2,6-azulenic motif was anchrored to the [Cr(CO)5] fragment prior to formation of its 6-SH terminus. Metalation of the 6-SH end of [(OC)5Cr] (7) with Ph3PAuCl, under basic conditions, afforded X-ray structurally characterized heterobimetallic Cr0/AuI ensemble [(OC)5CrAuPPh3] (8). Analysis of the 13C NMR chemical shifts for the [(NC)Cr(CO)5] core in a series of the related complexes [(OC)5Cr] scale\" fill=\"currentColor\" stroke=\"none\">C, Br, H, SH, SCH2CH2CO2CH2CH3, SAuPPh3) unveiled remarkably consistent inverse-linear correlations \u03b4(13COtrans) vs. \u03b4(13CN) and \u03b4(13COcis) vs. \u03b4(13CN) that appear to hold well beyond the above 2-isocyanoazulenic series to include complexes [(OC)5Cr(CNR)] containing strongly electron-withdrawing substituents R, such as CF3, CFClCF2Cl, C2F3, and C6F5. In addition to functioning as a sensitive 13C NMR handle, the essentially C4v-symmetric [(\u2013NC)Cr(CO)5] moiety proved to be an informative, remote, \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCN/\u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC infrared reporter in probing chemisorption of 7 on the Au(111) surface.Mercapto (\u2013SH) and isocyano (\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) substituents are among particularly popular anchoring groups in coordination and surface chemistry as they are well-known to provide stable junctions at metal/organic interfaces. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC functionalities in the same molecule are not presently known and constitute a formidable synthetic challenge. Indeed, a mercapto group is incompatible with reaction conditions commonly employed to form an isocyano substituent, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC or the \u2013SH terminus of such a hypothetical linker prior to forming and tethering its other end. There is only one related example in the literature, albeit not involving a mercapto group per se but rather its disulfide surrogate.via the 4-isocyanophenylthiolate bridge, Kubiak and coworkers attached both \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC ends of otherwise non-isolable 1,2-bis(4-isocyanophenyl)disulfide to trinuclear nickel clusters in the \u03bc3,\u03b71 fashion.3(\u03bc3-I)(\u03bc2-dppm)3 scale\" fill=\"currentColor\" stroke=\"none\">NC6H4S\u2013)}2]2+(I\u2013)2 (dppm = bis(diphenylphosphino)methane), underwent homolysis of its S\u2013S moiety upon exposure to a gold surface to give rectifying, presumably ionic, monolayer films.26Mercapto (\u2013SH) and isocyano scale\" fill=\"currentColor\" stroke=\"none\">N) junctions for accommodating the asymmetric anchoring on the premises that the \u2013SH and \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN termini would facilitate alignments of a linker's HOMO and LUMO , respectively, through Fermi level pinning.2Earlier this year, Ratner and van Dyck proposed a new paradigm for the design of efficient molecular rectifiers that involved two \u03c0-conjugated units asymmetrically anchored to metallic electrodes and separated by a decoupling bridge.and isocyano anchoring groups. The linker's core is comprised of the non-alternant aromatic framework of azulene, a substitution-free molecular diode which has, among other unusual physico-chemical characteristics, complementary orbital density distributions within its Frontier molecular orbitals . As illustrated in 1 and 2: 2-isocyano-6-mercapto-1,3-diethoxycarbonylazulene (3a) and 2-mercapto-6-isocyano-1,3-diethoxycarbonylazulene (3b). Among these two hybrids, 3a is particularly interesting because each substituent in its structure reinforces the molecular dipole of the azulenic framework. In fact, our Density Functional Theory (DFT) calculations suggest that the dipole moment of the \u201cparent\u201d azulene molecule should increase nearly 10-fold upon incorporation of all substituents to form 3a disulphide (vide supra),255 is thermally and air-stable for practical purposes and can be stored under ambient conditions for at least a few weeks without spectroscopically detectable deterioration. Compound 5 reacted with Cr(CO)5(THF) via its 2-NC end to form orange Cr0 adduct 6. No product featuring the thioether S \u2192 Cr(CO)5 interaction5] moiety of 6 tolerated the basic environment and subsequent acidification of the reaction mixture used to convert 6 into auburn organometallic thiol 7, which constitutes 3a with its 2-NC terminus anchored to the 16-e\u2013 [Cr(CO)5] fragment. Metalation of the 6-SH end of 7 with PPh3AuCl under basic conditions yielded orange-red crystals of heterobimetallic Cr0/AuI complex 8 after a simple workup.Our synthetic approach to constructing and metalating 8\u00b7\u00beCH2Cl2 features two very similar but crystallographically independent molecules of 8 in the asymmetric unit that are linked together via a weak Au\u00b7\u00b7\u00b7Au interaction8 undergoes donor\u2013acceptor face-centred stacking3 ligand giving the intercentroid distances8 may be viewed as a hybrid of our X-ray structurally characterized mononuclear Cr0 and AuI adducts of 1 and 2, respectively, depicted in 9 ,ca. 166.5\u00b0) in 8 is undoubtedly a consequence of the Au\u00b7\u00b7\u00b7Au bonding reinforced further by the \u201caromatic donor-acceptor interactions\u201d.8 compared to that in 10, which are ca. 107.8\u00b0 105.0\u00b0, respectively. Notably, the solid state structure of 10 exhibits neither aurophilic nor aromatic stacking interactions akin to those observed for 8.29The solid-state structure of ted in 9 and 10 (in 9 (10 ). While 5] core in 8 are quite similar to those observed for 9 scale\" fill=\"currentColor\" stroke=\"none\">N bond distances8 and 9 scale\" fill=\"currentColor\" stroke=\"none\">C groups at position 6 of the azulenic scaffold. However, this suggestion should be taken cum grano salis as such subtle variations in d(Cr\u2013CN) and d scale\" fill=\"currentColor\" stroke=\"none\">N) are statistically ambiguous, especially under the 3\u03c3 criterion. More drastic changes in the electronic nature of the isocyanide ligand's substituent do lead to significant alterations in the Cr\u2013CN and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond lengths in (RNC)Cr(CO)5 as illustrated in tBu scale\" fill=\"currentColor\" stroke=\"none\">CF2.43The metric parameters for the octahedral core in 6, 7, 8, and 9, we noticed that they were predictably sensitive to the nature of the substituent at position 6 of the azulenic scaffold. To further validate this initial observation, we expanded the above family of four related complexes [(OC)5Cr] scale\" fill=\"currentColor\" stroke=\"none\">C) to include species with X = H (11) and Br (12). The top six rows in 13C NMR data pertaining to the [(NC)Cr(CO)5] moiety in this series of six 2-isocyanoazulenic adducts. All of these 13C NMR measurements were performed for samples dissolved in CDCl3.Whilst considering net electron-releasing ability of X decreases scale\" fill=\"currentColor\" stroke=\"none\">C), the \u03b4(13CN) value for the isocyano carbon resonance increases in the range spanning ca. 8 ppm, thereby signifying gradual drop in the \u03c3-donor/\u03c0-acceptor ratio of the 2-isocyano-6-X-azulene ligand. Concomitantly, both \u03b4(13COtrans) and \u03b4(13COcis) values decrease, albeit in tighter chemical shift ranges , indicating reduction in the electron richness of the Cr-centre. Even though the 13C chemical shifts of terminal CO and CNR ligands in low-valent complexes are influenced considerably by the paramagnetic shielding term, \u03c3para, which reflects the degree of \u03c0-backbonding,\u03b4(13CN) and \u0394\u03b4(13CO) as a combined \u03c3-donor/\u03c0-acceptor effect.From 13C NMR data in the top six rows of \u03b4(13COtrans) vs. \u03b4(13CN) and \u03b4(13COcis) vs. \u03b4(13CN), as illustrated in trans-CO ligand to a greater extent than the cis-CO's of the [(NC)Cr(CO)5] moiety. Would the trends depicted in 5 species containing strongly electron-withdrawing substituents R, for which 13C NMR data acquired in the same solvent (CDCl3) were available (bottom four rows in \u03b4(13COtrans) vs. \u03b4(13CN) and \u03b4(13COcis) vs. \u03b4(13CN) plots that, in addition to the 2-isocyanoazulenic complexes, include (OC)5Cr(CNR) with R = C6F5,2F3,2Cl,3 (\u03b4(13CN) and \u0394\u03b4(13CO) windows.Closer examination of the F3,2Cl,3 are show\u03b4(13CO)/\u03b4(13CN) NMR analysis serves as a convenient tool for quantifying even subtle electronic influence of a CNR ligand's substituent R. In this regard, it offers a simple alternative to the well-established method involving correlation the carbonyl 13C chemical shifts with the corresponding CO force constants (kCO) for complexes (RNC)Cr(CO)5.kCO due to mild electronic perturbations of the R group are often not clearly discernible.kCO's under the C4v symmetry for complexes (RNC)5Cr(CO)5 using the Cotton\u2013Kraihanzel (C\u2013K) approximation\u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC vibrational profile\u0393\u03bdCO = 2A1 + B1 + E, e.g., 5 species, the lower energy \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC(A1) band is often obscured by the intense \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC(E) band,\u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC(A1) value (vide infra).The above \u03b4(13CN) for the (RNC)Cr(CO)5 adducts in 13C NMR resonance for the terminal C-atom in the available uncoordinated 2-isocyanoazulenes moves upfield upon increasing electron-donating power of the substituent X at the azulenic 6-position scale\" fill=\"currentColor\" stroke=\"none\">C, Br, H, SCH2CH2CO2CH2CH3, respectively). Yet, the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCN stretching frequency for these free 2-isocyano-azulenes (2126 \u00b1 1 cm\u20131 in CH2Cl2) is insensitive to the nature of the group X. However, upon proceeding from 8 to to 12 to 9, the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCN band undergoes a small red shift scale\" fill=\"currentColor\" stroke=\"none\">CN bands at 2583 and 2140 cm\u20131, respectively, it features a typical pattern in the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC stretching region for a LM(CO)5 species.\u20131 corresponds to the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC mode A1(1) where all five CO ligands vibrate in-phase scale\" fill=\"currentColor\" stroke=\"none\">OC vibration of B1-symmetry, which is IR-forbidden under the strict C4v symmetry but gains slight intensity because of minor deviations of the structure from the idealized C4v geometry. The intense \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC band at 1958 cm\u20131 chiefly represents the doubly degenerate vibration of E-symmetry. This \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC(E) band obscures the remaining IR-active \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC mode A1(2). Interestingly, perturbations of the local C4v symmetry in 7 through crystal packing interactions in the solid state are sufficient to split the E-mode into two separate \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC peaks while unmasking the original A1(2) mode (phase cf.. The ver(2) mode .ca. 1 \u00d7 1 cm2 gold substrates to a 2 mM solution of 7 in CHCl3 without protection from air and ambient lighting reproducibly afforded self-assembled monolayer (SAM) films of 7 on the Au(111) surface. This chemisorption process is presumably accompanied by formation of the thiolate junction and the release of H2.7 on Au(111) is shown in \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCN absorption at 2135 cm\u20131, it features two \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC bands. The \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC region in this RAIR spectrum, however, is quite different from that in \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC band in the solution IR spectrum of 7, which is primarily attributed to the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC mode of E symmetry, practically vanishes upon the SAM formation, while simultaneously uncovering the hidden A1(2) band of much lower intensity. This observation implies approximately parallel orientation of the cis-CO ligands with respect to the gold surface. Indeed, surface IR selection rules7 is expected to be essentially linear, the appearance of the RAIR spectrum in i.e., straight C\u2013S\u2013Ausurface angle) of the molecules in the SAMs of 7.Exposing via S(3p)\u2013Au \u03c0-bonding.5] unit. The A1(1) and A1(2)\u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC bands at 2058 and 1995 cm\u20131 in the RAIR spectrum in \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC peaks in the solution FTIR spectrum of 7 mode, to be attributed solely to differences in intermolecular interactions within the SAM vs. solution of 7. The larger change in energy of the \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC A1(2) mode compared to that of the A1(1) mode upon chemisorption of 7 stems from the greater contribution of the trans-CO stretch to the former.62The \u201chollow-linear\u201d coordination of organic thiolates in their SAMs on Au(111), akin to that depicted in 7 provided consistent SAM thickness values that nicely corroborate the monolayer nature of these films and upright orientation of the molecules on the gold surface (7 and 9 on Au(111) differ only in the surface anchoring group (thiolate vs. isocyanide) and appear to exhibit essentially identical thicknesses.7 on Au(111) would be consistent with the \u201con-top-bent\u201d7 invoking a bent C\u2013S\u2013Ausurface geometry. The ellipsometric measurements on SAM films formed from our recently reportedThe tilt angle of the aromatic moiety in SAMs of benzenoid mercaptoarenes on Au(111) can be highly variable. surface . In term13C NMR signatures of the octahedral [(\u2013NC)Cr(CO)5] core in related complexes 6, 7, 8, 9, 11, and 12 provided a sensitive spectroscopic handle for tuning electron richness of the Cr0-centre through mediation by the 2,6-azulenic framework. Moreover, the remarkably consistent inverse-linear trends \u03b4(13COtrans)/\u03b4(13CN) and \u03b4(13COcis)/\u03b4(13CN) for a wide spectrum of complexes (RNC)Cr(CO)5 offer a simple and more accurate alternative to the \u03b4(13CO)/kCO strategy in quantifying electronic influence of the substituent R in isocyanide ligands. This 13C NMR approach utilizes feedback from the entire [(\u2013NC)Cr(CO)5] unit rather than focusing on the [Cr(CO)5] fragment in the \u03b4(13CO)/kCO method. In addition, the C4v-symmetric [(\u2013CN)Cr(CO)5] moiety served as a distinctly informative \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCN/\u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC infrared reporter for probing self-assembly of the 6-mercaptoazulenic motif on the Au(111) surface. We hope that the chemistry of the 2-isocyano-6-mercaptoazulenic platform introduced herein will facilitate further development and experimental validation of the emerging concept of asymmetric anchoring relevant to the design of organic electronics materials. Efforts to access and isolate completely free 3a are currently in progress.The asymmetric nonbenzenoid aromatic framework of azulene proved to be a convenient platform for accessing the first \u03c0-linker terminated with both mercapto and isocyano junction moieties. Anchoring the 2-isocyano end of this linker was an important prerequisite to successfully installing its 6-mercapto terminus. The Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Background: A recent bioinformatics technique involves changing\u00a0nucleotide sequences into 2D speckles. This\u00a0technique produces\u00a0speckles\u00a0called\u00a0GB-speckles (Gene Based speckles). All classical strategies of speckle-optics, namely speckle-interferometry, subtraction of speckle-images as well as speckle-correlometry\u00a0have been inferred for processing of GB-speckles. This indicates the considerable improvement in the present\u00a0tools of bioinformatics.\u00a0\u00a0Methods: Colour\u00a0s-LASCA\u00a0imaging of virtual laser GB-speckles, a new method of high discrimination and typing of pathogenic viruses, has been developed. This method has been adapted to the detecting of natural mutations in nucleotide sequences, related to the\u00a0spike\u00a0glycoprotein\u00a0(coding the gene \u00abS\u00bb) of SARS\u2013CoV-2 gene as the molecular target.\u00a0\u00a0\u00a0Results: The rate of the\u00a0colouring\u00a0images of virtual laser GB-speckles generated by\u00a0s-LASCA\u00a0can be described by the specific value of\u00a0R. If the nucleotide sequences compared utilizing this approach the relevant images are completely identical, then the three components of the resulting\u00a0colour\u00a0image will be identical, and therefore the value of\u00a0R\u00a0will be equal to zero. However, if there are at least minimal differences in the matched nucleotide sequences, then the\u00a0value\u00a0of\u00a0R\u00a0will\u00a0be\u00a0positive.\u00a0\u00a0\u00a0Conclusion: The high effectiveness of an application\u00a0of the\u00a0colour\u00a0images of GB-speckles that were generated by\u00a0s-LASCA- has been demonstrated for discrimination between different variants of the SARS\u2013CoV-2\u00a0spike\u00a0glycoprotein\u00a0gene. Recently, the possibility of transforming a nucleotide sequence into a pattern of 2D speckles had been demonstrated. This new type of speckle pattern has been called \u201cGB-speckles\u201d (gene-based speckles). Changes within in the structure of the GB-speckles can reflect even negligible changes in the nucleotide sequence, caused by inartificial mutations. This allows detection of single-nucleotide polymorphisms (SNP) using virtual GB-speckles with outstanding precision. In addition, it offers unlimited potential of improving the diagnosis\u2019 accuracy by increasing the Fourier transform area.As it is well known, if laser light diffracts on random objects, then laser speckles are formed. implementation of speckle-optics methods, like speckle-interferometry and subtraction of speckle-images as well as speckle-correlometry for processing of GB-speckles, provides considerable progress in the current bioinformatics toolbox. This can become crucial to significantly improve existing routine methods of laboratory diagnostics of infectious diseases. GB-speckles as a technique opens the door to the new horizons in digital biology.Essential advancement in the area of GB-speckles has been reported in previous years. According to previously published reports,omp1 genes for two different ofChlamydia spp., such asChlamydia trachomatis andChlamydia psittaci of at least six genovars have been composed. Probability density functions and correlation properties of spatial intensity fluctuations for the relevant GB-speckle patterns have been studied. As it has been shown in previous studies, the presence of inartificial mutations in analysed strains, including single SNP cases, can be easily defined using methods of speckle-optics. More recently, the encoding algorithm\u2019s optimization for nucleotide sequences ofC. trachomatis into two-dimensional GB-speckle pattern had been carried out; and speckle-interferometric technique may give rise the ultra-fast optical processors of DNA sequences. This is ensured by the development of the exclusive system of interferential fringes which are generated by the model interference pattern led by the existence of any type of mutations. Additionally, the method of virtual phase-shifting speckle-interferometry was reported to be efficacious to investigate of polymorphism of theC. trachomatis omp1 gene. This approach allowed the detection of theC. trachomatis omp1 gene with SNPs, including both a single SNP and a combination of several SNPs in the bacterial strains with genetic mutations had been developed.Recently, model GB-speckle patterns of nucleotide sequences of theEnterobacteriaceae. These proteins have been found on the surface of several bacterial agents causing different enteric infections, such as salmonellosis, shigelosis, yersiniosis, and escherichiosis. Further, the phase and the relevant two-dimensional distributions of the intensity of GB-speckles in various strains of viral pathogens, namely of lumpy skin disease virus of cattle, LSDV, and also for sheep-pox virus, SPPV have been obtained. Additionally, interference patterns for generated the specific superposition in the relevant fields of GB-speckle and the certain difference in their images have been successfully investigated to reveal a minimal discrimination between the initial viral nucleotide sequences.The format of GB-speckles had been successfully applied to transform the nucleotide sequences of the genes expressing the serine proteases, the well-known Omptin family proteins within the GB-speckles processing via ans-LASCA technique application. As it had been demonstrated, it is possible to extend affectability of the proposed approach comparing to current bioinformatics strategies usings-LASCA imaging in the GB-speckles\u2019 processing. It had been shown in Ref.s-LASCA imaging method are very effective to analyze nucleotide polymorphism in several genes ofC. trachomatis.A new bioinformatics approach has been proposed very recently:s-LASCA imaging of GB-speckles. Such a technique is an improved version of previously suggested \u201cgreyscale\u201ds-LASCA imaging that was recently developed especially for GB-speckles. Nucleotide sequences for some target genes SARS\u2013CoV-2 have been successfully processed using coloureds-LASCA-imaging. Natural mutations in the comparing genes have been reliably and accurately detected.This paper is devoted to development of advantageously new technique: the colouredSeven nucleotide sequences of spike glycoprotein of SARS-CoV-2, namely:the gene#1. hCoV-19/cat/USA/TX-TAMU-078/2020 (Accession ID: EPI ISL 699509),the gene#2. hCoV-19/cat/Russia/RII-LEN-22246S/2021 (Accession ID: EPI ISL 811147),the gene#3. hCoV-19/cat/Greece/2K/2020 (Accession ID: EPI ISL 717979),the gene#4. hCoV-19/Wuhan/WIV04/2019 (Accession ID: EPI ISL 402124),the gene#5. hCoV-19/England/QEUH-B11766/2020 (Accession ID: EPI ISL 642476),the gene#6. hCoV19/South Africa/KRISP-EC-K005299/2020 (Accession ID: EPI ISL 678597),the gene#7. hCoV-19/Russia/MOS-CRIE-13604226/2020 (Accession ID: EPI ISL 754198).GISAID database.have been compared on the base of analysis of GB-speckles. The official reference sequences were taken from thes-LASCA imaging techniqueAlgorithm for the total conversion of a nucleotide sequence to a colour GB speckle structure, processed byFirst, the sequence of the letters derived from the original one-dimensional nucleotide sequence was converted into the sequence of numbers in accordance with the following rule: thus, other rules could have been applied to the encoding, for instance:It is critical to emphasize that the specific relationship between the letters and numbers in this case is not critical as used earlier;Next, all possible triad combination are generated. As a result, a complete set of all triads is formed:The number of all possible combinations of four numbers combined in triads is 64. This algorithm was implemented in Matlab R2015a (RRID:SCR_001622); an open access alternative isJulia. The value of h is a positive integer, varying in the range from 1 to 64. In this case, each triad from the original nucleotide sequence is associated with only one h value. So, for example, the combination (1 1 1) conforms to the value h = 1, (1 1 2) corresponds to h = 2, (1 1 3) conforms to h = 3, (1 1 4) conforms to h = 4, (1 2 1) conforms to h = 5, (1 2 2) conforms to h = 6, and so on. Finally, the latest combination (4 4 4) conforms to the value h = 64. Finally, a square matrix Hn,m was formed by a one-dimensional array h. The physical significance of the shaped matrix Hn,m is that each of its elements represents the local height of some virtual rough surface corresponding to the local content of the analyzed genetic construction. The resulting virtual rough surfaces could be used to model original speckle structures corresponding to diverse particular nucleotide sequences.Then, a discrete magnitude, h, is allotted to each triad in accordance with the simple algorithm described previously.n,m. At each point of the virtual diffuser (in the beam scattering plane), some phase modulation Un,m = exp is introduced (j is an imaginary unit). The surface is illuminated at the normal incidence of the beam; the phase in the illuminating beam was a constant value.The two-dimensional speckle patterns that corresponded to each specific sequence was generated with the use the diffraction of a coherent beam with a square cross-section profile on a virtual scattering surface with a microrelief described by the matrix HXo andYo are the coordinates in the observation plane,z is the distance between the scattering plane and the observation plane,\u03bb is the wavelength. The illuminating radiation is completely monochromatic, thus,\u03bb = const. In this situation, the structure of speckles does not depend on the wavelength andz. Only the sizes of GB-speckles depend on these values, the average size of which is determined by the ratio:a is the size of the illuminated fragment of virtual surface. It is important to emphasize that the ratio\u03bb/a characterizes the diffraction angular divergence of a laser beam in the far field, and the product of this divergence angle by the light traveled distancez is equal to the lateral size of the beam. Thus, it can be seen that the diameter of the undisturbed laser beam is shown below.The original nucleotide sequence is as follows:ATGTTTGTTTTTCTTGTTTTATTGCCACTAGTCTCTAGTCAGTGTGTTAATCTTACAACCAGAACTCAATTACCCCCTGCATACACTAATTCTTTCACACGTGGTGTTTATTACCCTGACAAAGTTTTCAGATCCTCAGTTTTACATTCAACTCAGGACTTGTTCTTACCTTTCTTTTCCAATGTTACTTGGTTCCATGCTATACATGTCTCTGGGACCAATGGTACTAAGAGGTTTGATAACCCTGTCCTACCATTTAATGATGGTGTTTATTTTGCTTCCACTGAGAAGTCTAACATAATAAGAGGCTGGATTTTTGGTACTACTTTAGATTCGAAGACCCAGTCCCTACTTATTGTTAATAACGCTACTAATGTTGTTATTAAAGTCTGTGAATTTCAATTTTGTAATGATCCATTTTTGGGTGTTTATTACCACAAAAACAACAAAAGTTGGATGGAAAGTGAGTTCAGAGTTTATTCTAGTGCGAATAATTGCACTTTTGAATATGTCTCTCAGCCTTTTCTTATGGACCTTGAAGGAAAACAGGGTAATTTCAAAAATCTTAGGGAATTTGTGTTTAAGAATATTGATGGTTATTTTAAAATATATTCTAAGCACACGCCTATTAATTTAGTGCGTGATCTCCCTCAGGGTTTTTCGGCTTTAGAACCATTGGTAGATTTGCCAATAGGTATTAACATCACTAGGTTTCAAACTTTACTTGCTTTACATAGAAGTTATTTGACTCCTGGTGATTCTTCTTCAGGTTGGACAGCTGGTGCTGCAGCTTATTATGTGGGTTATCTTCAACCTAGGACTTTTCTATTAAAATATAATGAAAATGGAACCATTACAGATGCTGTAGACTGTGCACTTGACCCTCTCTCAGAAGCAAAGTGTACGTTGAAATCCTTCACTGTAGAAAAAGGAATCTATCAAACTTCTAACTTTAGAGTCCAACCAACAGAATCTATTGTTAGATTTCCTAATATTACAAACTTGTGCCCTTTTGGTGAAGTTTTTAACGCCACCAGATTTGCATCTGTTTATGCTTGGAACAGGAAGAGAATCAGCAACTGTGTTGCTGATTATTCTGTCCTATATAATTCCGCATCATTTTCCACTTTTAAGTGTTATGGAGTGTCTCCTACTAAATTAAATGATCTCTGCTTTACTAATGTCTATGCAGATTCATTTGTAATTAGAGGTGATGAAGTCAGACAAATCGCTCCAGGGCAAACTGGAAAGATTGCTGATTATAATTATAAATTACCAGATGATTTTACAGGCTGCGTTATAGCTTGGAATTCTAACAATCTTGATTCTAAGGTTGGTGGTAATTATAATTACCTGTATAGATTGTTTAGGAAGTCTAATCTCAAACCTTTTGAGAGAGATATTTCAACTGAAATCTATCAGGCCGGTAGCACACCTTGTAATGGTGTTGAAGGTTTTAATTGTTACTTTCCTTTACAATCATATGGTTTCCAACCCACTAATGGTGTTGGTTACCAACCATACAGAGTAGTAGTACTTTCTTTTGAACTTCTACATGCACCAGCAACTGTTTGTGGACCTAAAAAGTCTACTAATTTGGTTAAAAACAAATGTGTCAATTTCAACTTCAATGGTTTAACAGGCACAGGTGTTCTTACTGAGTCTAACAAAAAGTTTCTGCCTTTCCAACAATTTGGCAGAGACATTGCTGACACTACTGATGCTGTCCGTGATCCACAGACACTTGAGATTCTTGACATTACACCATGTTCTTTTGGTGGTGTCAGTGTTATAACACCAGGAACAAATACTTCTAACCAGGTTGCTGTTCTTTATCAGGGTGTTAACTGCACAGAAGTCCCTGTTGCTATTCATGCAGATCAACTTACTCCTACTTGGCGTGTTTATTCTACAGGTTCTAATGTTTTTCAAACACGTGCAGGCTGTTTAATAGGGGCTGAACATGTCAACAACTCATATGAGTGTGACATACCCATTGGTGCAGGTATATGCGCTAGTTATCAGACTCAGACTAATTCTCCTCGGCGGGCACGTAGTGTAGCTAGTCAATCCATCATTGCCTACACTATGTCACTTGGTGCAGAAAATTCAGTTGCTTACTCTAATAACTCTATTGCCATACCCACAAATTTTACTATTAGTGTTACCACAGAAATTCTACCAGTGTCTATGACCAAGACATCAGTAGATTGTACAATGTACATTTGTGGTGATTCAACTGAATGCAGCAATCTTTTGTTGCAATATGGCAGTTTTTGTACACAATTAAACCGTGCTTTAACTGGAATAGCTGTTGAACAAGACAAAAACACCCAAGAAGTTTTTGCACAAGTCAAACAAATTTACAAAACACCACCAATTAAAGATTTTGGTGGTTTTAATTTTTCACAAATATTACCAGATCCATCAAAACCAAGCAAGAGGTCATTTATTGAAGATCTACTTTTCAACAAAGTGACACTTGCAGATGCTGGCTTCATCAAACAATATGGTGATTGCCTTGGTGATATTGCTGCTAGAGACCTCATTTGTGCACAAAAGTTTAACGGCCTTACTGTTTTGCCACCTTTGCTCACAGATGAAATGATTGCTCAATACACTTCTGCACTGTTAGCGGGTACAATCACTTCTGGTTGGACCTTTGGTGCAGGTGCTGCATTACAAATACCATTTGCTATGCAAATGGCTTATAGGTTTAATGGTATTGGAGTTACACAGAATGTTCTCTATGAGAACCAAAAATTGATTGCCAACCAATTTAATAGTGCTATTGGCAAAATTCAAGACTCACTTTCTTCCACAGCAAGTGCACTTGGAAAACTTCAAGATGTGGTCAACCAAAATGCACAAGCTTTAAACACGCTTGTTAAACAACTTAGCTCCAATTTTGGTGCAATTTCAAGTGTTTTAAATGATATCCTTTCACGTCTTGACAAAGTTGAGGCTGAAGTGCAAATTGATAGGTTGATCACAGGCAGACTTCAAAGTTTGCAGACATATGTGACTCAACAATTAATTAGAGCTGCAGAAATCAGAGCTTCTGCTAATCTTGCTGCTACTAAAATGTCAGAGTGTGTACTTGGACAATCAAAAAGAGTTGATTTTTGTGGAAAGGGCTATCATCTTATGTCCTTCCCTCAGTCAGCACCTCATGGTGTAGTCTTCTTGCATGTGACTTATGTCCCTGCACAAGAAAAGAACTTCACAACTGCTCCTGCCATTTGTCATGATGGAAAAGCACACTTTCCTCGTGAAGGTGTCTTTGTTTCAAATGGCACACACTGGTTTGTAACACAAAGGAATTTTTATGAACCACAAATCATTACTACAGACAACACATTTGTGTCTGGTAACTGTGATGTTGTAATAGGAATTGTCAACAACACAGTTTATGATCCTTTGCAACCTGAATTAGACTCATTCAAGGAGGAGTTAGATAAATATTTTAAGAATCATACATCACCAGATGTTGATTTAGGTGACATCTCTGGCATTAATGCTTCAGTTGTAAACATTCAAAAAGAAATTGACCGCCTCAATGAGGTTGCCAAGAATTTAAATGAATCTCTCATCGATCTCCAAGAACTTGGAAAGTATGAGCAGTATATAAAATGGCCATGGTACATTTGGCTAGGTTTTATAGCTGGCTTGATTGCCATAGTAATGGTGACAATTATGCTTTGCTGTATGACCAGTTGCTGTAGTTGTCTCAAGGGCTGTTGTTCTTGTGGATCCTGCTGCAAATTTGATGAAGACGACTCTGAGCCAGTGCTCAAAGGAGTCAAATTACATTACACATAA (7)After converting a sequence of letters into a sequence of numbers in accordance with the algorithm described by rule (1) described previously, the nucleotide sequence takes the following form:143444344444244344441443221241342424134213434344114244121122131124211441222224321412124114424442121234334344414412224312111344442131422421344441214421124213312443442441224442444422114344124433442214324141214342424333122114334124113133444314112224342241221444114314334344414444324422124313113424112141141131332433144444334124124441314423113122213422241244144344114112324124114344344144111342434311444211444434114314221444443334344414412212111112112111134433143311134313442131344414424134323114114432124444311414342424213224444244143312244311331111213334114442111114244133311444343444113114144314334414444111141414424113212123224144114441343234314242224213334444423324441311221443341314443221141334144112142124133444211124441244324441214131134414443124224334314424424421334433121324334324321324414414343334414244211224133124444241441111414114311114331122144121314324341312434321244312224242421311321113434123443111422442124341311111331142414211124424112444131342211221121311424144344131444224114144121112443432224444334311344444112322122131444321424344414324433112133113131142132112434344324314414424342241414114422321421444422124444113434414331343424224124111441114314242432444124114342414321314421444341144131334314311342131211142324221333211124331113144324314414114414111441221314314444121332432344141324433114424112114244314424113344334334114414114412243414131443444133113424114242111224444313131314144421124311142414213322334132121224434114334344311334444114434412444224441211421414334442211222124114334344334412211221412131341341341244424444311244241214321221321124344434331224111113424124114443344111112111434342114442112442114334441121332121334344244124313424112111113444243224442211211444332131312144324312124124314324342234314221213121244313144244312144121221434424444334334342134344141121221331121114124424112213344324344244414213334344112432121311342224344324144214321314211244124224124433234344414424121334424114344444211121234321332434441141333324311214342112112421414313434312141222144334321334141432324134414213124213124114424224233233321234134341324134211422142144322412124143421244334321311114421344324412424114112424144322141222121114444124144134344122121311144241221343424143122113121421341314434121143412144434334314421124311432132114244443443211414332134444434121211441112234324441124331141324344311211312111112122211311344444321211342111211144412111121221221144111314444334334444114444421211141441221314221421111221132113133421444144311314241244442112111343121244321314324332442142111211414334314432244334314144324324131312242144434321211113444112332244124344443221224443242121314311143144324211412124424321243441323334121142124424334433122444334321334324321441211141221444324143211143324414133444114334144331344121213114344242414313112211111443144322112211444114134324144332111144211312421244424422121321134321244331111244211314343342112211114321211324441112123244344111211244132422114444334321144421134344441114314142244421234244312111344313324311343211144314133443142121332131244211134443213121414343124211211441144131324321311142131324424324114244324324124111143421313434341244331211421111131344314444434331113332414214244143422442224213421321224214334341342442443214343124414342224321211311113112442121124324224322144434214314331111321212444224234311334342444344421114332121212433444341121211133114444414311221211142144124121312112121444343424334112434314344341141331144342112112121344414314224443211224311441312421442113313313441314111414444113114214121421221314344314441334312142424332144114324421344341112144211111311144312232242114313344322113114441114311424242142314242211311244331113414313213414141111433221433412144433241334444141324332443144322141341143343121144143244432434143122134432434134434242113332434434424434331422432432111444314311312312424313221343242111331342111441214412121411 (8)As a result of diffraction of coherent beam on the phase screen ) with a square cross-section is formed GB-speckle-structure of two-dimensional intensity distribution, seeImportant to emphasize, that experimental studies were not carried out in this work, only computer modeling. The scheme for calculating GB-speckles during radiation diffraction on a virtual scattering surface is described in detail in the work.s-LASCA strategy has been connected for handling of GB-speckles. The strategy ofs-LASCA is based on the examination of an individual realization of static speckles., In this case, the whole realization of the speckle field is divided into square zones; typically, each counting 5\u00d75 or 7\u00d77 pixels.For each zone, the contrast of GB-speckles was calculated using the simplest formula:I was the varying intensity of GB-speckles, changing from point to point;I\u03c3 was the standard deviation of the intensity of fluctuations. After the contrastC is calculated in each point,LASCA image is developed. Here, the size of subarea for the local contrast calculating was 2\u00d72 pixels. As it has been demonstrated this size of subarea is close to optimal.whereTo generate three two-dimensional implementations of GB speckles built for different genetic sequences, it is necessary to construct a colour image, where each colour component has its own GB speckle structure. When all three speckle structures were totally indistinguishable, the colour images look grey-scale. If the colour components differ from each other, then, as a result, colouring will appear in the image.InInIt is quite obvious that in the case under consideration, there is a pronounced colouring over the whole image for the field of GB-speckle.Thus, the obtained colour image for the intensity and phase of GB speckles is a reliable diagnostic sign of the presence of polymorphism.s-LASCA image is obtained for each of the three components of the matched genetic sequence, the final colour image can be constructed. An example of such an image is shown inOnce anIt is obvious that the image shown inwherei is the pixel number,M andN are the number of rows and columns of the analyzed image,N \u00d7M is the total number of pixels in the image.is the average intensity value in each pixel,s-LASCA imaging of GB-speckles are completely identical, then the three components of the resulting colour image will be identical, and therefore the value ofR will be equal to zero. However, if there are at least minimal differences in the compared nucleotide sequences, then the value ofR will take a positive value. Thus, the value ofR calculated for theObviously, if the nucleotide sequences compared usingR calculated forInR is that this parameter characterizes the degree of coloring of the picture (GB-speckle- pattern). The bioinformatic (molecular biology) value ofR is that it takes positive values, even in the case of the appearance of a one SNP in the analyzed nucleotide sequences. Thus, the minimum natural mutations of the virus can be determined using the parameterR.The physical meaning of the introduced parameterR equals to 0.596 for this case.Finally, three SARS\u2013CoV-2 genes are reflected inR calculated forR at least in two times higher for GB speckles, processed bys-LASCA imaging technique.It is important to note that the value ofR is positive for all images inR is an important diagnostic feature when detecting the presence of SNPs in SARS\u2013CoV-2 genes. This is the main result of this paper.Evidently,s-LASCA \u2018imaging technique\u2019 generating original GB-speckles. It is established that even one SNP can be reliably detected. It has been demonstrated that suggested technique is very effective tool for discrimination between different variants of the SARS\u2013CoV-2 spike glycoprotein gene.A fundamentally new bioinformatics technique for reliable detection of single SNPs is proposed. The new method is based on the applying of theGISAID Gene: hCoV-19/cat/USA/TX-TAMU-078/2020. Accession number EPI ISL 699509;GISAID Gene: hCoV-19/cat/Russia/RII-LEN-22246S/2021. Accession number EPI ISL 811147;GISAID Gene: hCoV-19/cat/Greece/2K/2020. Accession number EPI ISL 717979;GISAID Gene: hCoV-19/Wuhan/WIV04/2019. Accession number EPI ISL 402124;GISAID Gene: hCoV-19/England/QEUH-B11766/2020. Accession number EPI ISL 642476;GISAID Gene: hCoV19/South Africa/KRISP-EC-K005299/2020. Accession number EPI ISL 678597;GISAID Gene: hCoV-19/Russia/MOS-CRIE-13604226/2020. Accession number EPI ISL 754198.GISAID public database.Sequences are available after registration at the I am very grateful for the chance to take part in the review of the article for your respected journal. The current manuscript is devoted to demonstrating the application of the s-LASKA method for discrimination of different variants of the SARS\u2013CoV-2\u00a0spike\u00a0gene. Fortunately, the authors consider this approach as very attractive and available for precise diagnostics of the infection with the use of a new generation of medical devices. In fact, this can be recognized as the new direction for bioscience.via ans-LASCA technique\u2026\u2019 \u2013 via should not be italic;p. 3: \u2018A new bioinformatics approach has been proposed very recently: 14 GB-speckles processingp. 7-8: the legends for Figures 1-2 contain no indication for which genes the GB-speckles were generated, as well as it is pointed in the legends for Figures 3a, 3b, and 3c. It is critical for the extended auditorium of readers to clearly understand what is demonstrated in Figures 1-2. These points need a correction. I have no additional proposals for edits. The revised version of the article can be recommended for indexing with no further reviewing. In my point of view, this is very interesting and important research that contains several new findings. The article is clearly written, conclusions correspond to data obtained, and statistical treatment is appropriate. However, the paper needs minor revision before it can be indexed. The following are my concerns about the article:Is the work clearly and accurately presented and does it cite the current literature?YesIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?YesIs the study design appropriate and is the work technically sound?YesAre the conclusions drawn adequately supported by the results?YesAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:laser physics, biomedical scienceI confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. Dear Prof\u00a0Dmitry A. Zimnyakov, we highly appreciate your review for our manuscript. All your recommendations were accepted. All necessary corrections have been done in the text of the paper. Thank you very much once more. The authors. The paper can de accepted for indexing in the present new form.Is the work clearly and accurately presented and does it cite the current literature?PartlyIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?YesIs the study design appropriate and is the work technically sound?YesAre the conclusions drawn adequately supported by the results?PartlyAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:Singular and Correlation OpticsWe confirm that we have read this submission and believe that we have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. The article is devoted to an extremely relevant and very\u00a0 interesting topic \u2013 an application of GB- speckles, in particular, processed by the s-LASCA imaging method, in relation to the discrimination of SARS\u2013CoV-2 strains. GB-speckle is a new word in the field of bioinformatics. In the future, these optical virtual speckle structures can be effectively used as an alternative to classical bioinformatics methods. The usage of GB-speckles can be considered as a replacement for traditional computer methods of sequencing of any nucleotide sequences. As it follows from the analysis of the literature, the authors of this article have successfully used these methods, based on the processing of virtual speckles, to the analysis of natural mutations in the comparing genes.s-LASCA\u00a0\u2018imaging technique\u2019 generating original GB-speckles. The article demonstrates that colored s-LASCA-imaging can be successfully used for the diagnosis and differentiation of various strains of SARS-CoV-2. Also, this article presents a fundamentally new method, based on the using of colored GB-speckles, processed by s-LASCA-imaging technique. The new method is based on the applying of the\u00a0The authors need to check carefully the reference(s) and link(s) for the bioinformatic tools used.After the providing of clear the answer to this question, the reviewed article can be accepted for indexing without any additional changes and without the additional cycles of reviewing. The utilization of GB-speckles in diagnostics is an absolutely new direction, which has been developed and is being successfully promoted by the authors of this article. I have no questions about the application of speckle interferometry methods in molecular biology, reflected in this work. I only have some minor criticisms, regarding bioinformatics:Is the work clearly and accurately presented and does it cite the current literature?PartlyIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?YesIs the study design appropriate and is the work technically sound?YesAre the conclusions drawn adequately supported by the results?YesAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:NAI confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. The authors are extremely grateful to the respected reviewer Alexey Bashkatov for a detailed analysis of our article. In accordance with the recommendations of the reviewer, all references and links are checked, thank you. Any optical speckle is the result of the interference of waves scattered by inhomogeneities, and to obtain a speckle pattern, the wavelength is decisive. Thus, the question arises about the concrete wavelengths used in the study and their relationships with pseudo inhomogeneities. It would be interesting to know about the coherence of the sources used the modelling.\u00a0Please present an experiment setup, and the results of experimental modelling.It would be interesting to conduct a complete analysis of the entered parameter R, to represent its physical, biochemical meaning. The virus is constantly mutating, how is it possible to estimate the degree of virus mutation using this parameter. The paper can be indexed after reworking.The paper is devoted to the investigations of virtual Gene Based speckles for the determination the difference between SARS-Cov-2 spike glycoprotein genes. As it was noted by the authors the given method can use the classical approaches of speckle-optics. But there are some questions:\u00a0Is the work clearly and accurately presented and does it cite the current literature?PartlyIf applicable, is the statistical analysis and its interpretation appropriate?YesAre all the source data underlying the results available to ensure full reproducibility?YesIs the study design appropriate and is the work technically sound?YesAre the conclusions drawn adequately supported by the results?PartlyAre sufficient details of methods and analysis provided to allow replication by others?YesReviewer Expertise:Singular and Correlation OpticsI confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Any optical speckle is the result of the interference of waves scattered by inhomogeneities, and to obtain a speckle pattern, the wavelength is decisive. Thus, the question arises about the concrete wavelengths used in the study and their relationships with pseudo inhomogeneities. It would be interesting to know about the coherence of the sources used the modelling.\u00a0Response: This is really reasonable and very important question.\u00a0Fragment below is added to the new version of the text: It is assumed that speckles are formed in the far diffraction zone and described in the Fraunhofer approximation. In this case, the expression for the amplitude of the scattered field is the Fourier transform of the field in the diffraction plane, evaluated at frequencies spaces\u00a0Reply to the comments of reviewer Prof. Oleg\u00a0Angelsky: Fx=Xo/( z* \u03bb),\u00a0\u00a0\u00a0Fy=Yo/( z* \u03bb),\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0(*)\u00a0 where Xo and Yo are the coordinates in the observation plane, z is the distance between the scattering plane and the observation plane,\u00a0\u03bb\u00a0is the wavelength. The illuminating radiation is completely monochromatic, thus,\u00a0\u03bb\u00a0=const.\u00a0McGraw Hill Companies, New York\u00a0(1988).\u00a0 Reference to Goodman, J. W. Introduction to fourier optics.\u00a0 In this situation, the structure of speckles does not depend on the wavelength and z. Only the sizes of GB-speckles depend on these values, the average size of which is determined by the ratio:\u00a0 d~3*z* \u03bb /a\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0(**)\u00a0 where a is the size of the illuminated fragment of virtual surface. It is important to emphasize that the ratio\u00a0\u03bb/a characterizes the diffraction angular divergence of a laser beam in the far field, and the product of this divergence angle by the light traveled distance z is equal to the lateral size of the beam.\u00a0 New reference: M. Francon. La granularite laser (speckle) et ses applications en optique. Masson, Paris, New York, Barcelone, Milan 1978.\u00a0 Thus, it can be seen that the diameter of the undisturbed laser beam ) and the average speckle size are approximately equal to each other in any observation plane.\u00a0 In other words, when the parameters z and\u00a0\u03bb\u00a0change, a proportional change in the size of all speckles occurs synchronously. At the same time, the structure of speckle-patterns in all observation planes are completely similar, only their scale changes from plane to plane, but not the shape of the speckles or their location in the speckle pattern.\u00a0Please present an experiment setup, and the results of experimental modelling.\u00a0Response:\u00a0Experimental studies were not carried out in this work, only computer modeling. The scheme for calculating GB speckles during radiation diffraction on a virtual scattering surface is described in detail in the work:\u00a0 Ulianova OV, et al.: Speckle-interferometry and speckle-correlometry of GB-speckles. Frontiers in Bioscience-Landmark 2019; 24, 700-711.\u00a0This fact is mentioned in the new version of this article.\u00a0It would be interesting to conduct a complete analysis of the entered parameter R, to represent its physical, biochemical meaning. The virus is constantly mutating, how is it possible to estimate the degree of virus mutation using this parameter.\u00a0\u00a0Response: The physical meaning of the introduced parameter R is that this parameter characterizes the degree of coloring of the picture (GB-speckle- pattern). The bioinformatic (molecular biology) value of R is that it takes positive values, even in the case of the appearance of a one SNP in the analyzed nucleotide sequences. Thus, the minimum natural mutations of the virus can be determined using the parameter R.\u00a0This circumstance is also noted in the Conclusions of new version of this article.\u00a0 \u200b\u200b\u200b\u200b\u200bThe authors are extremely grateful to the respected reviewer, whose critical comments have significantly improved the quality of this article."}
+{"text": "A carbon catalyst prepared by air oxidation of woody biomass hydrolyses woody biomass, and the reaction residue is transformed back to the catalyst by the same air oxidation method. Eucalyptus) provides a carbonaceous material bearing an aromatic skeleton with carboxylic groups (2.1 mmol g\u20131) and aliphatic moieties. This catalyst hydrolyses woody biomass to sugars in high yields within 1 h in trace HCl aq. Furthermore, after the reaction, the solid residue composed of the catalyst and insoluble ingredients of woody biomass is easily transformed back to fresh catalyst by the same air oxidation method. This is a self-contained system using woody biomass as both the catalyst source and substrate for realising facile catalyst preparation and recycling.Biomass is the sole carbon-based renewable resource for sustaining the chemical and fuel demands of our future. Lignocellulose, the primary constituent of terrestrial plants, is the most abundant non-food biomass, and its utilisation is a grand challenge in biorefineries. Here we report the first reusable and cost-effective heterogeneous catalyst for the depolymerisation of lignocellulose. Air oxidation of woody biomass ( Production of biofuels and bio-chemicals from lignocellulose, the most abundant non-food biomass, is a grand challenge in biorefineries.The use of heterogeneous catalysts is desired for the efficient depolymerisation of lignocellulose as they are non-corrosive and can be separated from product solution.Regardless of the preferable characteristics of heterogeneous catalysts, the contamination of the catalyst with solid lignin after the reaction prevents their application in the depolymerisation of real lignocellulose. Removal of lignin from solid catalysts is often challenging, essentially rendering the catalyst useless after the first reaction. Hence, the lignin fraction must be removed by pretreatment such as the kraft process before applying lignocellulose to the hydrolysis reaction.via oxidation. Thus, we can expect that the carbon material prepared by air oxidation hydrolyses lignocellulose. In this way, the catalyst is readily prepared, and more importantly the used catalyst and residual lignin can be together transformed into fresh catalyst by the same air oxidation method.Our idea for resolving the issues of conventional heterogeneous catalysts is to produce a weakly acidic carbon catalyst through simple air oxidation of lignocellulose and lignin residue. Organic materials thermally decompose to form carbonaceous material at an elevated temperatureEucalyptus by air oxidation, which is necessary only once. The second part (Part 2) is a cyclic process consisting of milling pretreatment, hydrolysis of Eucalyptus to glucose and xylose in trace HCl, and transformation of the solid residue to fresh catalyst by the same air oxidation. We used Eucalyptus as both a catalyst source and biomass substrate to make this a self-contained system. Eucalyptus is a fast-growing and inexpensive plant [<0.1 pounds (GBP) kg\u20131] that has been cultured as a major feedstock for pulping.Eucalyptus to produce a catalyst. Eucalyptus powder was first washed with boiling water and dried , xylan hemicellulose (10 wt%) and lignin (32 wt%). Ash was present in a small amount (0.12 wt%) and mainly composed of Ca salts was used to clarify the structural change of Eucalyptus by air oxidation gave major peaks at 110\u201350 ppm, mainly ascribed to cellulose and hemicellulose.Caromatic\u2013O at 160\u2013140 ppm, Caromatic\u2013C and Caromatic\u2013H at 140\u2013110 ppm).CO2R (170 ppm), Caromatic\u2013O (150 ppm) and sp3 carbons (<100 ppm).E-Carbon in a transmission mode scale\" fill=\"currentColor\" stroke=\"none\">O) (1770\u20131720 cm\u20131), \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C, aromatic) (1610 cm\u20131), \u03b4(C\u2013H) (1470\u20131370 cm\u20131) and a mixture of various vibrations such as \u03bd(C\u2013O) (1350\u20131000 cm\u20131),2R at 288.6 eV (13 \u00b1 1%), C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO at 287.2 eV (3 \u00b1 2%), C\u2013O at 286.2 eV (20 \u00b1 5%), and C\u2013C and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC at 284.6 eV (65 \u00b1 5%) . It was confirmed that the aromatics and acidic sites were not only derived from lignin but also from cellulose fractions; air oxidation of cellulose gave a similar carbon material 1470\u201310 cm\u20131 an) Fig. S3.38 The ce Fig. S5. This reEucalyptus under N2 at 573 K as a control. This material had significantly weaker aromatic peaks in the NMR gives aromatic precursors at 473\u2013573 K for the manufacture of carbon fibres.2-treated Eucalyptus, only weak C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO peaks were observed in the IR spectrum ] were milled together, named mix-milling,E-Carbon (50 mg) and Eucalyptus (324 mg) was subjected to a hydrolysis reaction in a 120 ppm HCl aqueous solution (pH 2.5) at 488 K .The mix-milled solid containing at 488 K . This recalyptus , entry 4Eucalyptus, we assume that E-Carbon and the mild acidic solvent (pH 2.5) synergistically accelerate the formation of monomeric sugars. It has been reported that trace HCl hydrolyses cellulose to produce soluble oligosaccharides, which enables the subsequent hydrolysis of oligosaccharides by solid acid catalysts.Eucalyptus, reactions in the absence of HCl or carbon catalyst provide unpractical yields of monomeric sugars (entries 1\u20133). HCl can be neutralised after the reaction with very low economic impact, as the acid concentration is less than 1/50 of conventional mineral acid processes.In the hydrolysis of entries \u20133. HCl cE-Carbon. Since a reaction in aq. HCl without E-Carbon afforded glucose in 32% yield and xylose in 26% yield (entry 3), E-Carbon increases the yield of glucose by 46% and yield of xylose by 68% (subtraction of yields in entry 3 from those in entry 4). The increase corresponds to a turnover number of carboxylic acid of 5.6. The result indicates that E-Carbon acts as a catalyst for the hydrolysis of cellulose and hemicellulose in Eucalyptus. We also found that the air-oxidised carbon prepared from cellulose worked in this reaction similarly to E-Carbon as shown in entry 7 . This shows that a cellulose-derived part also constitutes the active catalytic domain in E-Carbon. Contrastingly, the Eucalyptus-based catalyst prepared by N2 treatment was inactive . Therefore, it is concluded that the air oxidation of woody biomass provides active catalysts for the hydrolysis of lignocellulose.Controlled experiments were performed to reveal the important parameters influencing the catalytic activity of E-Carbon can be converted to a fresh catalyst again by air oxidation as shown in Eucalyptus (mainly lignin) and 0.51 g of E-Carbon, obtained in a large-scale experiment] to a black powder of 1.14 g. Accordingly, the catalyst weight increased from 0.51 to 1.14 g after one cycle in this system. The surplus residue can be used as fuel to power the process, since the solid is derived only from woody biomass and air. The 13C CP/MAS NMR spectrum of the regenerated catalyst contained a strong aromatic carbon peak with small fractions of \u2013CO2R, Caromatic\u2013O and aliphatic groups for the preparation of catalyst, which is in sharp contrast to conventional catalytic processes that require removal of the contaminant.The solid residue recovered after the reaction with 9% yield , entry 5 Table S4. It is tE-Carbon with reported catalysts, the active site is slightly similar to those of enzymes (cellulase).E-Carbon can work under harsher conditions, which enables the rapid hydrolysis of lignocellulose in trace HCl aq. at high temperature. Moreover, our catalyst is reusable and the price (ca. 0.1 GBP kg\u20131) is two-orders lower than that of cellulase (6.5\u201326 GBP kg\u20131).Comparing ce ca. 0. GBP kg\u20131Eucalyptus, produces a carbon-based catalyst overcoming the limitations of conventional catalysts used for the hydrolysis of woody biomass. The catalyst quickly converts lignin-containing Eucalyptus to glucose and xylose in high yields. Lignin remains as a solid together with the catalyst after the reaction; however, this solid mixture is a source for fresh catalyst and fuel. Therefore, the E-Carbon system drastically reduces the preparation and post-treatment costs of the catalyst. In general, the deactivation or spoiling of catalyst by contaminant is often a major issue in catalytic reactions. Hence, our idea that converts contaminant to a catalyst can be a useful strategy for improving the efficiency of catalytic processes.The air oxidation of biomass feedstock, Eucalyptus powder was washed with boiling water prior to use for all purposes in this study. 4.00 g of dried Eucalyptus powder was spread with a thickness of 3 mm on a Pyrex dish (\u00f8130) to uniformly prepare the catalyst and avoid hot spots. The sample was calcined under air at atmospheric pressure in an electric furnace with the following program: 298 to 573 K by 5 K min\u20131 and 573 K for 1 h. In the case of reaction residue, the residue of 1.63 g was calcined under the same conditions. The temperature inside the sample was monitored using a thermocouple (\u00f80.5) equipped with a quartz tube (ca. \u00f81).Eucalyptus (5.0 g) and catalyst (0.77 g) were milled together in an Al2O3 pot (250 mL) with Al2O3 balls using a Fritsch P-6 planetary ball mill. Milling conditions were 500 rpm for 2 h with a 10 min interval after every 10 min of milling.Eucalyptus was performed in a hastelloy C-22 high-pressure reactor equipped with an agitator operating at 600 rpm and a thermocouple. Mix-milled sample (374 mg) and 40 mL of 120 ppm HCl aq. were added into the reactor. The temperature of the reaction mixture was elevated from 298 K to 488 K in ca. 17 min and then quickly lowered to 298 K. Soluble products were analysed by high-performance liquid chromatography (Shodex SUGAR SH1011 and Phenomenex Rezex RPM-Monosaccharide Pb++ columns with refractive index detectors).The hydrolysis of"}
+{"text": "The correct list of authors\u2019 names is provided and replaced online which is mentioned as under:Consuelo Sanavia1#*Marco Tatullo2#Jessica Bassignani1Silvia Cotellessa1Giulia Fantozzi1Giovanna Acito1Alessia Iommiello1Lorella Chiavistelli1Silvia Sabatini1Gianna Maria Nardi13The published list of authors was: Consuelo Sanavia1,\u00a0#,\u00a0*,\u00a0Marco Tatullo2,\u00a0#,\u00a0Jessica Bassignani1,\u00a0Silvia Cotellessa1,\u00a0Giulia Fantozzi1,\u00a0Giovanna Acito1,\u00a0Alessia Iommiello1\u00a0Lorella Chiavistelli1\u00a0Alessia Iommiello1\u00a0Silvia Sabatini1\u00a0Gianna Maria Nardi1\u00a03"}
+{"text": "Targeted C(sp3)\u2013H activation or nucleophilic substitution reactions have been achieved through the interaction of a diborane dianion with haloalkanes. 1H2 and its B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB-bonded formal deprotonation product Li2[1] can activate the particularly inert C(sp3)\u2013H bonds of added H3CLi and H3CCl, respectively. The first case involves the attack of [H3C]\u2013 on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB double bond on H3CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, \u03b1,\u03c9-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H3CLi/1H2 and H3CCl/Li2[1], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C\u2013H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) As prominent examples, 9,10-dihydro-9,10-diboraanthracenes (DBAs) catalyze inverse electron-demand Diels\u2013Alder reactions of 1,2-diazines1H2/Li[1H]/Li2[1] together with a dianionic species ([1]2\u2013). As a decisive difference, however, the boron atoms in [DBA]2\u2013 are linked by two o-phenylene rings, whereas in [1]2\u2013 they are directly connected by a double bond. Both systems thus possess different frontier orbitals and should exhibit different reactivities.With the triad ]/Li2[1] , we rece1H]\u2013 and [1]2\u2013 are accessible in good yields via alkali-metal reduction of 1H2.1]2\u2013 back to [1H]\u2013 and finally 1H2.1H2 to afford [1H]\u2013 is also quantitative, provided that the sterically demanding bases (Me3Si)2NLi and (Me3Si)3CLi are used. In case of the smaller nBuLi, the deprotonation reaction (20%) is accompanied by the formation of an anionic diborylmethane featuring a boron-bridging hydrogen atom .1H2 activate C(sp3)\u2013H bonds of added alkyllithium reagents RCH2Li? (ii) Will [1]2\u2013 show nucleophilic behavior also toward electrophiles other than the proton ?The anions /Li2[1] as a perfect platform for further studies into boron-promoted C\u2013H-activation processes and boron-centered nucleophiles. Herein we present evidence that the reactions of 1H2 with RCH2Li indeed proceed through C(sp3)\u2013H-cleavage steps and that the boron-bridging H atoms in the diborylmethane products stem from the organolithium reagents and are not remains of 1H2 (cf.3H7). We also show that the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB double bond of the dianion [1]2\u2013 behaves as a closed-shell nucleophile toward organohalides and that specifically H3CCl/Li2[1] and H3CLi/1H2 funnel into the same reaction channel. When H3CCl is replaced by an excess of H3C\u2013I, C\u2013H-activation is completely suppressed by a second nucleophilic substitution reaction to afford 2 equiv. of 9-methyl-9-borafluorene (3C). Employing \u03b1,\u03c9-dihaloalkanes X(CH2)nX and Li2[1], we gained further insight into the competition between the nucleophilic substitution and C\u2013H-activation scenarios as well as the cooperativity of the two adjacent boron centers .Before the background provided by the literature and our own previous results, we regarded the triad fluorene ; R = H3C1H2 with nBuLi furnish not only the deprotonation product Li[1H], but also the diborylmethane-hydride adduct shown in 3H7)?We started our study by addressing the question: why and how does the reaction of 3CLi in place of nBuLi maintains the same general reactivity . The 1H NMR spectroscopic monitoring of the reaction in a sealed NMR tube showed no free H2 (\u03b4 4.55 ppm),1H2 and H3CLi contain a sum of five BHB/H3CLi protons, of which only three remain in the product Li[2].First, we confirmed that a simplified system using Hactivity . From eq3CLi/1H2 or H3CLi/1D2 combinations furnished isotopically pure Li[2-d3] or Li[2], respectively (\u03b4(1H) 0.49 ppm, d), but also the boron-bridging hydrogen atom (\u03b4(1H) 1.94 ppm, br) in Li[2] originate from the organolithium reagent. None of the two BHB atoms of 1H2 is still present in the product Li[2-d3] (see the ESI1H] nor Li[2] (or their partly deuterated counterparts) and are consequently accountable for the missing 50% product yield (see below).Deuterium-labeling experiments with Dectively . Thus, n1H2 with H3CLi will be described the fate of the boron-bonded hydrogen atoms of 1H2, and (iii) the combined yield of only 50% for Li[1H] and Li[2]: similar to the case (Me3Si)3CLi/1H2, the reaction H3CLi/1H2 starts with the deprotonation of 1H2 to afford Li[1H]. The byproduct CH4 was detected by 1H and 13C{1H} NMR spectroscopy; when D3CLi was employed as the Br\u00f8nsted base, we instead observed the formation of D3CH 3CLi/1H2, the reaction involving H3CLi does not necessarily stop at the stage of Li[1H], because the small [H3C]\u2013 ion also has the potential to act as a Lewis base. Nucleophilic attack of H3CLi on a boron atom of Li[1H] establishes a B\u2013CH3 bond and shifts the boron-bridging hydrogen atom to a terminal position. The structural motif of the resulting intermediate [3]2\u2013 has precedence in the crystallographically characterized dianion [8]2\u2013,2[3] rearranges to Li2[4] through a 1,2-phenyl shift, accompanied by a 1,2-hydride shift. Again, a comparable hydrogen-containing species Li2[9] exists (2[9] can isomerize to Li2[FluB(H)\u2013(H)BFlu] (BFlu = 9-borafluorenyl),2[3] to Li2[4]. The latter reaction continues with an LiH-elimination step to generate Li[5], which possesses a three-coordinate boron atom with a vacant pz orbital and therefore easily undergoes a 1,2-phenyl shift to produce Li[6]. The anion [6]\u2013 can be viewed as the [H3C]\u2013 adduct of a diborane(4) containing two 9-borafluorene units that are linked by a B\u2013B single bond. Only the sp3-hybridized boron atom has acquired an electron octet, however, also the B(sp2) center might gain some electron density from an agostic interaction with the methyl group and thereby reduce its strong Lewis acidity.2]. It is well known that B(sp2)\u2013B(sp3) diboranes readily undergo B\u2013B-bond heterolysis and thereby act as mild sources of nucleophilic boron.2]\u2013 and [6]\u2013 are isoelectronic with protonated cyclopropane [C3H7]+. This cation has been thoroughly investigated by experimental6]\u2013 rearranging to [2]\u2013. At this stage, the dynamic behavior comes to an end, because, contrary to the case of [C3H7]+, the three corners of [2]\u2013 are not equivalent and the BHB bridge should be thermodynamically favored over alternative BHC bridges.Contrary to the case 4][2]; tBu substituents. The computed parent systems will be denoted with a superscript \u2018c\u2019 . The 1,2-phenyl shift in [5c]\u2013 proceeds viaTS1 with an activation barrier of \u0394G\u2021 = 9.9 kcal mol\u20131 and is endoergic by \u0394GR = 5.9 kcal mol\u20131. The resulting open-chain rearrangement product [6c-open]\u2013 features a large B\u2013B\u2013CH3 bond angle of 121\u00b0 and the vacant pz orbital of the B(sp2) atom is oriented almost orthogonal to the B\u2013CH3-bond vector, which precludes an agostic interaction in this isomer. To establish the B\u2013H\u2013C bridge proposed above, the tricoordinate borafluorene fragment must be rotated by approximately 70\u00b0 and the B\u2013B\u2013CH3 bond angle contracted \u2013 ultimately to a value of 68\u00b0 in the local-minimum structure [6c]\u2013. The conversion of [6c-open]\u2013 to the cyclic isomer [6c]\u2013viaTS2 is associated with a moderate energy penalty of \u0394GR = 4.6 kcal mol\u20131. The actual C\u2013H-activation process involves the transition state TS3 in which the B\u2013B bond and one C\u2013H bond are concertedly cleaved and a new B\u2013C bond is formed .In addition to the qualitative comparison with the all-carbon model system [Culations . Apart f2c-open]\u2013 is thermodynamically favored by \u201314.1 kcal mol\u20131 and \u20133.6 kcal mol\u20131 compared to [6c]\u2013 and [5c]\u2013, respectively. A further stabilization is achievable through rotation about a B\u2013C bond and placement of the hydrogen atom into a boron-bridging position to obtain the final product [2c]\u2013 . In summary, the reaction cascade from [5c]\u2013 to [2c]\u2013 possesses an overall activation barrier of \u0394G\u2021 = 14.9 kcal mol\u20131, which is easily surmountable at room temperature. An appreciable thermodynamic driving force is provided by the exergonicity of the [2c]\u2013 formation .The primary, open-chain activation product [1H] as the first intermediate along the pathway from 1H2 to Li[2], we treated an isolated sample of Li[1H] with 1 equiv. of H3CLi in THF. Even though the reaction started as expected, it stopped at the stage of Li2[4] (which enabled us to record a 1H NMR spectrum of this compound). The elimination of LiH from Li2[4] is thus not a spontaneous process, but apparently requires a hydride-trapping reagent. Compound 1H2 constitutes an ideal candidate for this purpose and, indeed, after the addition of 1 equiv. of 1H2, Li2[4] quantitatively vanished and Li[2] formed instead. Moreover, we found two sets of proton resonances that are assignable to two isomeric hydride-trapping products of 1H2 in 5] should be more facile on a B(sp2)\u2013B(sp3) rather than a B(sp3)\u2013B(sp3) scaffold .2] possesses an average C2v symmetry in solution, whereas a pending C3H7 substituent reduces the symmetry to Cs. Consequently, the 1H NMR spectrum of Li[2] contains only one set of signals for all four tBu-C6H3 rings. The corresponding spectrum of its Cs-symmetric congener features two sets of resonances,2] and thus likely assignable to those halves of the 9-borafluorene subunits, which point into the same direction as the proton residing on the methylene bridge. A similar interpretation is valid for the 13C{1H} NMR spectrum of Li[2]. Single crystals of [Li(thf)4][2] suitable for X-ray analysis were grown from THF-hexane .angement . For com10] readily isomerizes to the secondary hydride-trapping product Li[7], which we have isolated and characterized by NMR spectroscopy as well as X-ray crystallography. The anion of [Li(thf)3(Et2O)][7] consists of one 9-borafluorenyl and one BH2 fragment that are linked by a \u03bc-H atom and a 2,2\u2032-biphenylylene bridge .At room temperature, Li\u2013 and the known anion [9]2\u2013 are essentially superimposable, apart from the fact that the latter features a covalent B\u2013B bond (1.810(5) \u00c5) instead of the \u03bc-H atom , whereas the third set consists of very broad signals, each of them integrating 2H (thf)][Li(thf)2][11]; 11]2\u2013.Turning our attention from the products of the reaction CH2[11] are reasonably close to those of Li2[4] (cf. the ESI1H NMR spectra). Remarkably, Li2[11] is also accessible via a different approach, starting from the doubly boron-doped dibenzochrysene Li2[1] and tBuCCH, the conjugate weak acid of [tBuCC]\u2013 scale\" fill=\"currentColor\" stroke=\"none\">B double-bonded species. As mentioned above, the intermediate Li[6] of the reaction H3CLi/1H2 can be regarded as the [H3C]\u2013 adduct of a diborane(4). Conceptually, it should be possible to arrive at the same molecule by formally transferring two electrons from the carbon nucleophile to the redox-active organoborane and thus starting from methylium-ion sources and the anion [1]2\u2013 (39The facile protonationon [1]2\u2013 .392[1] is stirred at room temperature under a blanket of H3CCl gas (1 atm), a quantitative conversion to Li[2] occurs scale\" fill=\"currentColor\" stroke=\"none\">B fragment of Li2[1] likely acts as a nucleophile toward H3CCl to form [12]\u2013, which carries a boron-bonded methyl substituent and contains a central B\u2013B single bond. The B(sp2)\u2013B(sp3) species Li[12] then undergoes a 1,2-phenyl shift to afford Li[5] and thereby funnels into the reaction cascade outlined above for the formation of Li[2] from H3CLi/1H2 , the outcome is a mixture of Li[2], 9-methyl-9-borafluorene (13), and residual Li2[1] and (H3C)BFlu .When Hl Li2[1] . After iBFlu 13; . [BFlu]\u20133C\u2013I/Li2[1], the methyl group initially gets attached to only one of the symmetry-related boron centers, but the other is equally important for the subsequent C\u2013H-activation and nucleophilic substitution steps. The degree of B\u2013B cooperativity in Li2[1] as well as the insertion vs. nucleophilic behavior of [BFlu]\u2013 thus deserve a detailed assessment. To this end, we conducted a systematic study using 1\u2009:\u20091 mixtures of Li2[1] and \u03b1,\u03c9-dihaloalkanes X(CH2)nX with chain lengths in the range of n = 2\u20136 and leaving groups of different qualities . In these experiments, smaller alkylidene linkers are supposed to mimic higher local concentrations of the electrophile. As summarized in n = 2 and 3, cf.14C2 and 14C3; 1,3-dichloropropane leads to a complex mixture of products). Clean C\u2013H-activation reactions occur with the long-chain substrates (n = 5 and 6) to afford the haloalkyl species Li/Li and Li/Li. The medium-chain substrates (n = 4) mark the switching point between both scenarios: with the worse chloride leaving group, C\u2013H-activation is preferred over the twofold substitution. The reverse is true in the case of the better bromide leaving group. The solid-state structures of 14C2\u00b7thf, 14C3 2] 4], and [Li(thf)4] are supported by X-ray diffraction studies, however, due to disordered haloalkyl chains, tBu groups, and THF molecules, the quality of these three structures prevents their inclusion into this publication.41In case of the system Hhf, 14C3 , 14C4, a15C5,Cl] were chaThe observed chain-length dependence of the product distribution suggests that the carbene-type insertion and the second nucleophilic substitution both follow an intramolecular pathway involving two cooperating boron atoms.2X center and the BCH2 group are similarly close to the B\u2013B bond, the nucleophilic process occurs at a higher rate than the carbene-type C\u2013H-activation. As the alkylidene spacer grows, the second electrophilic functionality moves further apart whereas the reactive \u03b1-CH2 unit stays in place such that the C\u2013H-activation becomes more and more relevant until it finally takes over.If the remaining CH2[1] and, e.g., H3C\u2013I can convincingly be rationalized by assuming a nucleophilic pathway, the possible operation of a radical mechanism remains to be ruled out. We first note in this context that 1,2-dihaloethane in the presence of Li2[1] did not undergo reductive dehalogenation with ethene formation. Yamashita, Nozaki et al. have treated their boryllithium compound with methyl trifluoromethanesulfonate (H3COTf)2[1] (3COTf showed the same reactivity as described above for H3C\u2013I (cf. Li[2] and 13); BnBr (as well as BnCl) gave the C\u2013H-activation product Li[16] rather than any haloboranes, as confirmed by NMR spectroscopy and X-ray crystallography on [Li(thf)4][16].Although the reaction between LiOTf)2[1] , middle:2[1] to 1 equiv. of (bromomethyl)cyclopropane, a well-established radical clock . The absence of the ring-opened olefin derivative Li[18] in the reaction mixture strongly supports the proposal of a closed-shell scenario in contrast to an open-shell process.As the ultimate test, we added Lial clock , bottom. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB double bonds, but open new access routes to ditopic boranes of high Lewis acidity. Molecules containing two or more potentially cooperating boron sites are of great current interest, inter alia, as organocatalysts14nC already constitute free Lewis acids, but do not contain functional groups amenable to further derivatization.The results collected thus far are not only fundamentally interesting with respect to the reactivities of electron-rich B15n,XC]. Here, the terminal halogen atoms provide ample opportunities, e.g., for grafting the organoboron units onto polymers, dendrimers, or surfaces, but the Lewis acids need to be activated through LiH elimination prior to use.The opposite is true for the salts Li to its conjugate acid 14C1 to the tricoordinate spectral region (14C1: \u03b4 45 ppm).While the bulky hydride scavenger \u2013H activation and nucleophilic substitution reactions have been performed on the same redox-active diborane platform. We propose that the doubly 2,2\u2032-biphenylylene-bridged diborane(6) 1H2 reacts with H3CLi to furnish the rearranged B(sp2)\u2013B(sp3) intermediate Li[FluB\u2013BFlu(CH3)] . Li[6] also forms via an umpolung approach starting from H3CX and the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB bonded, nucleophilic Li2[1], a compound which can be regarded as the product of a double deprotonation of 1H2 . Li[6] readily undergoes B\u2013B-bond heterolysis to formally give the [BFlu]\u2013 anion and (H3C)BFlu (13). The final product distribution depends on the relative amount of H3CX and the leaving-group qualities of X, because [BFlu]\u2013 can either insert into a C(sp3)\u2013H bond of 13 or replace the halogen atom of a second equivalent of H3CX. The product of the carbene-type C\u2013H insertion is Li[FluB(\u03bc-CH2)(\u03bc-H)BFlu] (Li[2]) while the nucleophilic substitution on C\u2013X generates 2 equiv. of 13. Further insight into the competition between the two scenarios was gained with the help of \u03b1,\u03c9-dihaloalkanes X(CH2)nX . In the resulting intermediates Li[FluB\u2013BFlu((CH2)nX)], both possible follow-up reactions should be intramolecular processes. A longer alkylidene chain corresponds to a lower local concentration of the electrophile, while the BCH2 groups are always similarly close to the reactive B\u2013B bond. Consequently, short chains result in double substitution products FluB(CH2)nBFlu and long chains in C\u2013H-activation products Li[FluB(\u03bc-C(H)(CH2)n\u20131X)(\u03bc-H)BFlu]. In the case of the intermediate chain length n = 4, a mixture of both compounds is obtained: the worse leaving group X = Cl leads to a higher proportion of the C\u2013H-activated species, the better leaving group X = Br furnishes more FluB(CH2)4BFlu. We finally note that the B\u2013B-bond heterolysis of Li[6] with concomitant transfer of a reactive [BFlu]\u2013 moiety is reminiscent of the reactivity patterns of the widely used alkoxy-diborane(4) adducts [pinB\u2013Bpin(OR)]\u2013.\u2013 appears to be considerably more reactive than in situ-generated [Bpin]\u2013, because C\u2013H-insertion reactions of the latter are so far unknown.In summary, C(spThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The novel rectification\u2013insertion mechanism for the polymerization of polar norbornenes: making alternating copolymers from a single monomer. endo position. We have examined the polymerization mechanism of NBEs bearing one or two CO2Me groups either in exo or endo position catalyzed by the so-called naked allyl Pd+ SbF6\u2013 catalyst (1). Although endo dimethyl ester of 5-norbornene-2,3-dicarboxylic acid (NBE(CO2Me)2) is polymerized by 1, two endo units are never inserted consecutively along the polymer chain. Indeed, 1 is a tandem catalyst which not only catalyzes the insertion of the monomer but also the isomerization of endo and exo isomers. Thus, the polymerization of endo monomers proceeds via a novel mechanism, coined rectification\u2013insertion mechanism, whereby half of the endo monomers are rectified into exo ones prior insertion, leading to the formation of an alternating endo\u2013exo copolymer using an endo only feedstock. With this mechanism, the lack of reactivity of endo norbornenes is bypassed, and the polymerization of predominantly endo polar NBEs bearing a variety of functionalities such as esters, imides, acids, aldehydes, alcohols, anhydrides, or alkyl bromides proceeds with catalyst loadings as low as 0.002 mol%.The catalytic 1,2-insertion polymerization of polar norbornenes (NBEs) leads to the formation of functional rigid macromolecules with exceptional thermal, optical and mechanical properties. However, this remarkable reaction is plagued by the low reactivity of the polar monomers, and most notably of those bearing a functional group in Furthermore, Lewis acids such as alkyl aluminums, methylalumoxane or fluorinated boranes which are cocatalysts of early transition metal catalysts for NBE polymerization usually react with polar monomers.et al. demonstrated that [Pd(CH3CN)4][BF4]2 promoted the living polymerization of a series of esters of bicyclo[2.2.1]hept-5-ene-2-exo-methanol.3-allyl)palladium compounds with BF4\u2013 or SbF6\u2013 counter ions were able to catalyze the polymerization of bicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester (NBECO2Me).2H) was also reported. In 1995, Novak et al. reported that neutral Pd(ii) complexes bearing an hexafluoroacetyl acetonate and a \u03c3\u2013\u03c0 bicyclic alkyl ligands catalyze the living polymerization of NBE and a substituted oxanorbornene.2Me but a cationic analog was found to be active for the polymerization of NBECO2Me and the copolymerization of NBECO2H with NBE in a non-living manner, with either BF4\u2013,6\u2013 (i.e. diluted) with NBE or with ethyleneendo isomer is practically non-reactive and it deactivates the catalyst. The lack of reactivity of the endo substituted polar NBEsvia the exo face,endo face of the monomer, as shown by Sen et al. through the X-ray structure of an homologous Pt complex.et al. has ruled out the formation of chelate for naked cationic Pd complexes stabilized by the tBu3P phosphine and found that endo isomers are as reactive as exo ones.Functional macromolecules are essential components for the formation of complex nanostructures with defined shape and functionality with applications in optical and electronic materials, catalysis, recognition/separation technologies and drug delivery. BF4\u2013,6\u2013 or MAO30endo isomer is due to a series of factors . Furthermore, the catalyst promotes the rectification of the monomer . Numerous functional PNBEs 4\u2013, SbF6\u2013) have been investigated in the past for the polymerization of NBE, and we have selected SbF6\u2013 as it is more bulky than BF4\u2013 and PF6\u2013, and therefore putatively less coordinating, but it does not require handling pyrophoric MAO and B(C6F5)3.Our initial work on the polymerization of polar norbornenes was inspired by the discovery that cationic \u2018naked\u2019 Pd and Ni catalysts1, [PdS2]+SbF6\u2013 (S = solvent).2Me) (73% endo) occurs in low to moderate yield (0\u201356%) at high catalyst loadings (\u22650.2 mol%) in the majority of solvents becomes feasible even with a catalyst loading as low as 0.003 mol% which contrasts with past results reported in literature whereby catalyst loadings are typically comprised between 0.5 and 1%. In this study, all mechanistic studies have been performed in nitromethane as it keeps the polymer in solution without coordinating too strongly catalyst 1.When the polymerization is performed neat , the yield is limited to 65% . This limitation is purely physical in nature, and corresponds to a vitrification phenomenon: a mixture of 65% of polymer and 35% of monomer is so viscous that the monomer cannot diffuse to reach the active site. Thus, the yield of the neat polymerization modestly decreases when the catalyst loading is lowered, so that the homopolymerization of NBE(COcis-NBE(CO2Me)2 (abbreviated NBE(CO2Me)2) and trans-NBE(CO2Me)2 (one endo and one exo CO2Me group) are illustrated in endo content, the kinetics of trans isomer being comprised between the one of 35% endo and of 75% endo, and therefore being comparable to 50% endo. When the endo content in the monomer is greater than 25%, the polymerization is zero order in monomer, as shown by a linear evolution of the conversion vs. time, a behavior which is also observed for the polymerization of other monomers with 1 2]/[1] = 10 2 were inserted in 1, leading to the formation of catalysts 2, 3 and 4 respectively and by X-ray crystallography 2 is rapid, i.e. it is quantitative in less than a minute at room temperature 2 occurs in a cis fashion on the exo face, as shown in X-ray structures. The 3J coupling value between protons H2 and H3 is comprised between 6 and 8 Hz which is characteristic of a cis coupling are consistent with an exo placement of the Pd atom, ruling out the presence of a directing effect. Addition of NBE(CO2Me)2 (trans) to 1 results in the formation of two products (4X and 4N) in 50\u2009:\u200950 mol% ratio, as shown by 1H NMR product, the Pd atom is on the same side of the bridge as the exo (resp endo) CO2Me. The fact that 4X and 4N are in equal proportion is another indication that the endo ester does not act as a directing group for catalyst addition. In solution, the ester groups of the inserted NBE(CO2Me)2 are not coordinated, as shown by 13C NMR chemical shifts comprised between 173.2 and 175.5 ppm for C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO of complexes 2, 3, 4N and 4X, which correspond to the usual chemical shifts of CO2Me esters. For the sake of comparison, in a norbornane ring bearing two CO2Me groups in exo (resp trans), the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO resonates at 173.1 ppm (2Me either on these naked Pd complexes (see below) or on cationic Pd diimine complexes are found at lower field (177\u2013195 ppm).52In order to clarify the mechanism of polymerization, ectively , which wlography . The rea Fig. S11. In the 73.1 ppm . Structure 2s is a tetrameric macrocycle whereas 3s and 4Ns are polymeric (2O2-H and 3-THF) are obtained. The tetrameric solid 2s is soluble in non-coordinating solvents such as dichloromethane, chlorobenzene and tetrachloroethane however, polymeric 3s and 4Ns are insoluble in such solvents. Therefore, when the polymerization is performed in a non-coordinating solvent, the insertion of endo and the trans monomer leads to the formation of an insoluble active species (3s and 4s). Thus, the lack of reactivity of endo isomers in chlorinated solvents is in part explainable by the loss of Pd-containing species by precipitation. Interestingly, characteristic bond lengths and bond angles of complexes 2s, 3s, 4Ns, 2O2-H and 3-THF 2 at room temperature result in the immediate formation of 5 and 6 . In these complexes, endo-NBE(CO2Me)2 is chelated via its endo face to the Pd complex, as deduced by an unexpected downfield resonance for the HC13 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC14H moiety . The 13C carbonyl resonances are also shifted downfield (177.5 and 177.1 respectively for 5 and 6vs. 172.7 ppm for the uncoordinated monomer). This chelate is labile and rapidly exchanging within NMR timescale. For example, from 7.05 ppm in 5, the H13/14 resonance is displaced to 6.83 ppm for a 1\u2009:\u20091 mixture of 5 and endo-NBE(CO2Me)2, and to 6.48 ppm for a 1\u2009:\u200910 mixture of 5 and endo-NBE(CO2Me)2. Such exchange phenomenon is not observed when an excess of exo monomer is added to 5 or 6 as shown by separate resonances for the chelated endo monomer and free exo-NBE(CO2Me)2 2, polymerization is quantitative within 9 hours, as shown by the decrease of the olefin resonances in 1H NMR at 6.35 ppm. To our surprise, although no endo monomer was added to this reaction, the presence of the chelated complex 5 is also clearly detected in the reaction mixture, as shown by the presence of (1) a new downfield olefin resonance (6.8\u20137.0 ppm) characteristic of the endo chelated double bond, (2) a OCH3 resonance at 3.81 ppm which is neither observed in 2 (3.74 ppm) nor in the exo growing polymer chain (3.74 ppm) and (3) a characteristic H17 bridge proton for the chelated endo monomer at 1.71 ppm which could account for a maximum of 20% of the chelated Pd complexes . However, as much as 70% of the Pd atoms are found to be chelated. Therefore, the endo isomer must be generated during the polymerization reaction. Lewis acids are known to catalyze direct and retro Diels\u2013Alder reactions,exo monomer in endo monomer. Although is it well known that the exo monomer (thermodynamic product) is more stable than the endo monomer (kinetic product), DFT calculations indicate that the gain of stability is only 2.7 kJ mol\u20131. Therefore, the equilibrium constant between both isomers is 3, and the exo\u2013endo monomer distribution at equilibrium is 75\u2009:\u200925. Thus, even when starting from 100% exo monomer, endo isomer is generated during the polymerization. It will be seen below that the reverse situation is also true, that is to say that when starting from pure endo monomer, exo monomer is generated during the reaction.When Fig. S26. The exoexo monomer is polymerized by 2, the Lewis-acid catalyzed formation of the endo isomer leads to the generation of chelated 5 which is significantly less active for polymerization. Thus, only a fraction of the catalyst is 'naked' and active, resulting in the formation of polymers with molecular weights which are higher than expected (2. The initiation of the polymerization of exo-NBE(CO2Me)2 by 2 (rate constant ki) is slow relative to subsequent insertions (kp) as the Pd\u2013C2\u2013C3\u2013C10\u2013C11\u2013C12 6-member chelate must be broken during the first insertion. When polymerizing endo-NBE(CO2Me)2, the propagation rate (kp) is greatly decreased, thus the discrepancy between kp and ki is less noticeable. As the result, experimental and theoretical molecular weights are in good agreement for endo monomers (in situ formation of chelated 5 during the polymerization of exo-NBE(CO2Me)2 explains the deviation from linearity observed in the polymerization kinetics at high conversion 2 or mixtures of endo and exo NBE(CO2Me)2, as the catalyst is then entirely chelated from the onset of the polymerization.When the exo-NBE(CO2Me)2. However, it is desirable to polymerize monomers directly obtained by Diels\u2013Alder reaction, that is to say rich in endo isomer in order to avoid a painstaking separation step between endo and exo isomers. In this case, due to the presence of excess endo isomer, the catalyst is entirely chelated. Therefore, we will now concentrate on the reactivity of catalysts 5 and 6. Using 1H NMR, one can assess the regiochemistry of the last inserted monomer unit. Indeed, the methine proton in \u03b1 of Pd 2 2 (experiment B), insertion of a first exo monomer occurs within minutes , whereas the addition of two consecutive endo units is very slow (experiment A). Using the usual denomination for copolymerization rate constants, kendo,exo \u226b kendo,endo. The value of kendo,exo is too high to be measured precisely via1H NMR, but a lower limit for kendo,exo could be determined on the account that the insertion of one exo monomer by 6 proceeds in less than 10 minutes 2 in endo-NBE(CO2Me)2 is clearly observed in experiment B , but soon after, 1.6 equivalents of endo monomer are present , or that the insertion of endo monomer is immediately followed by the insertion of an exo monomer, due to the high value of kendo,exo. To lift this ambiguity, we have examined the reaction of 5 with 10 equivalents of endo-NBE(CO2Me)2 2 is inserted, as shown by the apparition over a few hours of a characteristic doublet at 4.3 ppm corresponding to H2 in an endo unit. Thus, the endo monomer is reactive and kexo,endo is non null. The low stability of catalyst 5 in solution is another indication that the endo isomer can be inserted after an exo unit. Indeed, when a solution of 5 in CD3NO2 ([5] = 0.032 mol L\u20131) is left for 7 hours, 30% of the chelated endo monomer is inserted 2, Fig. S33kexo,endo, obtained from the slope of the kinetic profiles, are respectively 3.6 \u00d7 10\u20132, 4.1 \u00d7 10\u20132 and 4.9 \u00d7 10\u20132 h\u20131, which yield an average value of kexo,endo of 4.2 \u00d7 10\u20132 h\u20131 , solutions of 6 are stable indefinitely 2 into exo-NBE(CO2Me)2 before polymerization can proceed. The value of kexo,exo was measured in two separate kinetic experiments , the insertion of two exo monomers consecutively is highly unlikely due to the low concentration of exo monomer in solution. Thus, the polymerization of the endo monomer leads to the formation of an alternating endo\u2013exo copolymer. The catalyst has rectified 50% of the less reactive endo monomers into more reactive exo monomers. We have coined such mechanism rectification\u2013insertion.Contrasting with the lack of stability of Fig. S31, indicaty ratios , it is cxo chain . When an1H NMR or 13C NMR has been hampered by the broadness of the peaks caused by the rigidity of polynorbornenes in solution 2, the 13C spectrum is constituted of very broad resonances, with a single peak observed at 173.1 ppm for C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO scale\" fill=\"currentColor\" stroke=\"none\">O and two resonances for exo C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO scale\" fill=\"currentColor\" stroke=\"none\">O are upfield relative to exo ones in 2, 3, 5 and 6). The presence of two exo C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO peaks in same proportion could arise from two different tacticities arising from the placement of consecutive NBEs.Microstructural analysis of these polymers, either by Fig. S39 could coendo isomer must be interconverted into exo. It is also well established that Lewis acids (such as 1) catalyze the Diels\u2013Alder and retro Diels\u2013Alder reaction.1 . Interestingly, freshly cracked cyclopentadiene can also be polymerized with 1, leading to a polymer which is not entirely similar to polydicyclopentadiene by 1H NMR . Second, kendo,endo must be significantly lower than the other propagation rate constants. Preliminary theoretical calculations indicate that kendo,endo is very low because of the large steric hindrance between the endo substituents of the penultimate inserted unit and the active site when two endo monomers are inserted in a row. Several elements point toward the fact the rectification\u2013insertion mechanism is not only prevailing with NBE(CO2Me)2 but also with other functionalized norbornenes. Induction periods are observed for the polymerization of predominantly endo monomers 2, NBE(imide), and NBE(CHO)). As a proof of the unique versatility of this reaction, the polymerization of aldehyde containing monomer NBE(CHO) was found to proceed in high yield which contrasts with radical, cationic and anionic polymerizations which are usually not efficient to prepare linear polymers containing pendant aldehyde groups.2H)2.Thanks to this mechanism, catalyst monomers , 2 and 4exo content (PNBE(imide) 5% endo, PCA, PNBE(CO2H)2) lead to polymers with a molecular weight higher than expected. As shown above, this behavior is a consequence of the rectification\u2013insertion mechanism: even when starting from pure exo monomer, endo chelated species can be formed, and only the remaining (unchelated) fraction is rapidly polymerizing. When the monomer contains high amount of endo isomer, experimental molecular weights are commensurate with theoretical values, which is again indicative of a high degree of control for the polymerization. All these polymers exhibit Tg which are higher than 300 \u00b0C with virtually identical yields to those obtained under inert atmosphere. For example, the polymerization of NBE(CO2H) occurs in 40% and 42% yield when performed respectively under inert atmosphere and in air.When the polymerization is performed in the absence of solvent, very low amounts of catalyst can be used (as low as 0.002 mol%), which is indicative of the exceptional robustness of the active species. The polymerization is then controlled by the drastic increase of viscosity associated with the formation of high Tg polymers, a physical limitation which could for example be mitigated by the use of heterophase processes. The polymers have in general low polydispersity indices (1.1 \u2264 PDI \u2264 1.6), indicating some degree of livingness for this type of polymerization (a feature which will be further explored in a subsequent report). Monomers with high Fig. S48, which iendo-rich monomers directly obtained via Diels\u2013Alder reaction with no need for cumbersome and time-consuming separation of both isomers. Furthermore, catalyst loadings as low as 0.002 mol% can be used, and both the monomer preparation and the polymerization can be performed in the absence of any solvent. Thus, the preparation of these rigid macromolecules is an archetypal example of green chemical process. This study has also aimed at clarifying the mechanism of polymerization of substituted NBEs. The endo isomers deactivate the catalyst because the endo active species are less soluble than the exo ones and the endo monomer forms a chelate with the naked catalyst. However, these limitations can be counteracted by the judicious choice of polymerization conditions, and, most importantly, by the action of the rectification\u2013insertion mechanism. Thus, the naked Pd complex has a tandem role of polymerization catalyst and of endo/exo isomerization catalyst. As two endo units cannot be inserted consecutively, it is possible to prepare alternating endo\u2013exo copolymers when starting from an endo monomer only. We envision that this novel mechanism could be easily exploited further, for example by adding a separate Lewis acid which could catalyze the retro/direct Diels\u2013Alder reaction, which should putatively lead to a rate acceleration and the disappearance of the induction period. Furthermore, due to high degree of control of these polymerization, we believe that this mechanism open the way to the formation of a wealth of hierarchical nanostructures generated upon self-assembly of rigid functional amphiphilic block PNBEs.The novel rectification\u2013insertion polymerization mechanism is a powerful mechanism for the preparation of rigid macromolecules obtained from polar NBEs, yielding functional polymers bearing highly valuable functional groups such as aldehydes, anhydrides, alcohols, alkyl halogens and carboxylic acids. Thus, this method offers the same level of versatility and practicality as highly popular chain-growth polymerizations such as ROMP or radical polymerizations. The reaction readily proceeds with Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Half-sandwich RhIII anticancer complexes with activated Cp* rings not only undergo sequential CH3 H\u2013D exchange, but also react with biological dienes, generating RhI Diels\u2013Alder adducts in aqueous media at ambient temperature. x C\u2013H protons in certain organometallic RhIII half-sandwich anticancer complexes [(\u03b75-Cpx)RhCl]+, where Cpx = Cp*, phenyl or biphenyl-Me4Cp, and N,N\u2032 = bipyridine, dimethylbipyridine, or phenanthroline, can undergo rapid sequential deuteration of all 15 Cp* methyl protons in aqueous media at ambient temperature. DFT calculations suggest a mechanism involving abstraction of a Cp* proton by the Rh\u2013hydroxido complex, followed by sequential H/D exchange, with the Cp* rings behaving like dynamic molecular \u2018twisters\u2019. The calculations reveal the crucial role of p\u03c0 orbitals of N,N\u2032-chelated ligands in stabilizing deprotonated Cpx ligands, and also the accessibility of RhI\u2013fulvene intermediates. They also provide insight into why biologically-inactive complexes such as [(Cp*)RhIII(en)Cl]+ and [(Cp*)IrIII(bpy)Cl]+ do not have activated Cp* rings. The thiol tripeptide glutathione and the activated dienophile N-methylmaleimide, (NMM) did not undergo addition reactions with the proposed RhI\u2013fulvene, although they were able to control the extent of Cp* deuteration. We readily trapped and characterized RhI\u2013fulvene intermediates by Diels\u2013Alder [4+2] cyclo-addition reactions with the natural biological dienes isoprene and conjugated -linoleic acid in aqueous media, including cell culture medium, the first report of a Diels\u2013Alder reaction of a metal-bound fulvene in aqueous solution. These findings will introduce new concepts into the design of organometallic Cp* anticancer complexes with novel mechanisms of action.The Cp These were sensitive to traces of water.et al. have shown that deuteration of the Cp* in [(Cp*)RhD2(BPin)] (BPin = bis(pinacolato)diboron) occurs readily in MeOD-d4 and synthesized the deuterated compound [(D15Cp*)RhD2(BPin)], under reflux in D2O/OD\u2013 for 3 days.et al. showed that deuteration of [(Cp*)RhCl(PTA)2]+ is assisted by the basic centers in the PTA ligand,I\u2013fulvene species, but no experimental evidence for the fulvene complex was obtained.In an early example, Kang and Maitlis deuterated the methyl groups in the dinuclear Rhet al.et al.I catalyst [(Cp*)Rh(bpy)] can lead to formation of H2 in dry acetonitrile. In the latter case, [(Cp*H)Rh(bpy)Cl], generated by reduction of the RhIII complex [(Cp*)Rh(bpy)Cl]+ followed by acidification in ether, was isolated, and shown to reduce NAD+ to NADH. The Cp* methyl protons underwent exchange with deuterium. Peng et al. have recently characterized the RhI phenanthroline analogue containing protonated Cp*, [(Cp*H)Rh(phen)Cl].et al.4-pentamethylcyclopentadiene\u2013RhI intermediates under protic conditions.Quintana 1H NMR peaks of some [(Cp*)RhClCl]+ complexes which we had synthesized as potential anticancer agents and transfer hydrogenation catalysts, rapidly lost intensity, suggesting activation towards H/D exchange under mild conditions. We have investigated the conditions under which this occurs, including the influence of solvent, aquation, and pH, and monitored the reactions by both 1H NMR spectroscopy and high resolution FT ICR MS spectrometry. We have also investigated the influence of substituents on the Cp* ligand (Cp* versus CpxPh and CpxPhPh), influence of the N,N\u2032-chelating ligand versus aromatic diamines bipyridyl (bpy), 4,4\u2032-dimethyl-2,2\u2032-bpyridine (mbpy), and phenanthroline (phen)), as well as the metal ion (RhIIIversus IrIII). The X-ray crystal structures of 8 new complexes are reported.Our own investigations began with observations that in aqueous solutions at ambient temperature, methyl x C\u2013H activation reactions. Importantly the DFT calculations led to the prediction of accessible RhI\u2013fulvene states and so we investigated the trapping of such intermediates by addition reactions with thiols (glutathione), dienes and dienophiles, l-Glu-l-Cys-Gly) is present in cells at millimolar concentrations, and might be expected to undergo addition reactions with double bonds such as those in a fulvene, as might NMM which contains an activated double bond. Fulvene is known to undergo Diels\u2013Alder reactions with both dienes and dienophiles.Z,11E)-linoleic acid -Linoleic acid is a common dietary conjugated fatty acid, of particular interest for its potential role in the prevention and treatment of a variety of diseases,We have used density functional theory (DFT) calculations to elucidate the mechanism of these Cpeic acid . IsoprenI\u2013fulvene trapping reactions under mild conditions of biological relevance is likely to open up new avenues of investigation into reactions of this class of half-sandwich organometallic complexes and influence their design as biologically-active agents. Our discovery of Diels\u2013Alder reactions of a metal-bound fulvene under mild conditions in aqueous solutions, appears to be unprecedented.The surprising success of these RhIII complexes 1 and 3\u201312 , and a monodentate chloride ligand were synthesized by the reaction of the appropriate chloride-bridged dimer and chelating ligand, except complex 12 which was prepared by substitution of chloride in complex 1 by pyridine. They were fully characterized by 1H NMR spectroscopy, ESI-mass spectrometry, and elemental analysis Rh(phen)Cl]SO3CF3,1, 3 and 4 are similar to those reported for [(Cp*)Rh(bpy)Cl]SO3CF3.12, the Rh\u2013N(pyridine) bond (2.127(4) \u00c5) is longer than other two Rh\u2013N (bipyridine) bonds (ca. 2.105 \u00c5).Organo\u2013Rhand 3\u201312 and IrII1 and 3\u201311 in 20% methanol-d4/80% D2O was confirmed by comparing 1H NMR spectra before and after removal of the chloride ligand by reaction with AgNO3. Complexes 1, 3\u201311 show fast hydrolysis at 310 K, reaching equilibrium in <10 min. Complete conversion of chloride complex 11 to the aqua adduct was observed, whereas 1, and 3\u201310 reached equilibrium with 30\u201360% formation of the aqua species , but resonances corresponding to the methyl protons in the Cp*, CpxPh and CpxPhPh ligands were not observed as the expected sharp singlets, but as broad signals, difficult to distinguish from the baseline Rh(bpy)(py)](PF6)2 (12). The X-ray crystal structure . Quantitative full deuteration was achieved at ambient temperature by the time the first 1H NMR spectrum was recorded (ca. 12 min). In contrast, when the sample of 1 was made acidic with DNO3, no deuteration was observed after 12 h. These results are compatible with Rh-OD acting as a base for proton abstraction and subsequent deuteration of the Cp*.Since deprotonation of Rh\u2013OHd Fig. S8. Complex15\u03b75-Cp*)Rh(bpy)Cl]PF6 (1D15) and used 2H NMR to show that, as expected, back D/H exchange was slow (ca. 50%) after 3 days in 60% MeOH/40% H2O involving the Cp* protonation.4Cp PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2]2\u2013 which could then rapidly gain a deuteron from solvent to generate a \u2013CH2D substituent. Rapid methyl and ring rotation can lead to the sequential deuteration of all 15 methyl protons. We modeled the hydroxido adducts using the CAM-B3LYP functional with a CEP-31G basis set. In the cases of both RhIII and IrIII bpyridine complexes [M(Cp*\u2013)(bpy)OH]+, the optimized structures show a relatively close M\u2013O(H)\u00b7\u00b7\u00b7HCH2 contact between the bound hydroxide and a Cp* ring methyl (11), the hydroxide is oriented so as to optimize H-bonding with an en NH2 proton, Rh\u2013O(H)\u00b7\u00b7\u00b7HNH(en) 2.053 \u00c5, These were performed to gain insight into the mechanism of deuteration and the difference in behavior between the bpy and phen complexes, and inactive Rhg methyl , being sg methyl . In cont4Cp PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2]2\u2013 and H2O ligands, \u20131 higher in energy than the original R\u2013OH/Cp*-state scale\" fill=\"currentColor\" stroke=\"none\">CH2]2\u2013/H2O-coordinated chelates lay 28 kJ mol\u20131 for Rh and 62 kJ mol\u20131 for Ir above Cp*/M\u2013OH. In the aqua adduct of the en Rh-complex, the H2O ligand is effectively outside the first coordination sphere , which together with rapid methyl rotation, would allow sequential deprotonation and deuteration of each of the ring methyl protons.Next we determined the energies of the structures after transfer of a proton from a Cp* methyl group to coordinated hydroxide, giving coordinated dianionic [Me Table S5. The com3 character of the CH2 carbon (H2O) scale\" fill=\"currentColor\" stroke=\"none\">CH2)]+. Thus, deprotonation of Cp* might introduce new pathways of activity including addition reactions of a bound fulvene, and redox reactions of rhodium.Remarkably, the comparison of the geometries of (a) free deprotonated Cp* ligand (optimized with CAM-B3LYP/CEP-31G), (b) deprotonated Cp* in the optimized structures of the complex, and (c) that of the neutral fulvene Cp* derivative (optimized with CAM-B3LYP/CEP-31G) suggest that the latter two are close in energy to each other, while the former reveals an spN,N\u2032-chelated ligand plays an important role in stabilizing the aqua/dianionic 2\u2013 intermediate in which H/D exchange can readily occur. Within the series of chelates of varying \u03c0-character of the N,N\u2032 ligands, the stability of the intermediates increases with increasing \u03c0-acceptor character of the ligand. When we increased the \u03c0-acceptor strength by adding strongly electron-withdrawing groups as in 1,2-diimino-4,5-dicyanobenzene, the energy difference decreased to only 13 kJ mol\u20131 above the OH adduct (Table S5).\u20131 higher in energy than that for the corresponding Rh complexes (Table S5I/IrI fulvene complex) is related to delocalization of the negative charge onto the N,N\u2032-chelated ligand via the d-orbitals of the metal. This is facilitated by the \u03c0-acceptor character of the N,N\u2032 ligand and is less effective for Ir than for Rh. Alternatively, the enhanced \u03c0-acceptor character of the N,N\u2032-chelate stabilizes the lower RhI oxidation state.Our calculations suggest that the \u03c0-acceptor strength of the Table S5. Thus, Dl-Glu-l-Cys-Gly) is prevalent in cells at millimolar concentrations, reactions of GSH were studied with 1 under conditions in which activation of Cp* ring methyls was expected. A solution of 1 and excess GSH at pH 7 gave rise only to MS peaks assignable to [(\u03b75-Cp*)Rh(bpy)(SG)]. Interestingly, the presence of GSH restricted, but did not prevent, ring methyl deuteration [(Cp*)Rh(bpy)(OH)]+/GSH, (c) [Rh scale\" fill=\"currentColor\" stroke=\"none\">CH2)(bpy)(OH2)]+/GSH, and (d) [Rh scale\" fill=\"currentColor\" stroke=\"none\">CH2)(bpy)]+/GSH/H2O, revealed [Rh(bpy)Cp*(SG)] as the most stable complex .Since ene\u2013thiol reactions are well known, and glutathione Rh(bpy)Cl]PF6, since with 2 mol equiv. of N-methylmaleimide present in 60% MeOD-d4/40% D2O, complete deuteration was not observed even after 7 days, rather MS peaks for all D1 to D15 sequential steps scale\" fill=\"currentColor\" stroke=\"none\">O\u00b7\u00b7\u00b7H\u2013OH bond of 1.68 \u00c5 rather than attacking the fulvene double bonds -linoleic acid, were used in attempts to trap the possible fulvene intermediate as [4+2] cyclo-addition Diels\u2013Alder adducts. These are both biologically-important, natural dienes. Isoprene is the most abundant hydrocarbon in human breath, with an estimated human production of 17 mg per day.Z,11E)-Linoleic acid is a common dietary conjugated fatty acid of much interest because of its potential health effects.[4+2] Diels\u2013Alder reactions with the exocyclic double bond of fulvene as dienophile have been reported in the literature.1 in 60% MeOD-d4/40% D2O at 310 K and isoprene was studied, since isoprene was expected to offer minimal steric hindrance for the reaction with the proposed exocyclicfulvene C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2. The ESI-MS spectra clearly indicated formation of a [4+2] cyclo-addition adduct, with the peaks at m/z = 497.1225 assignable to the RhI complex (13+H)+ in a RhI\u2013(Cp*H) complex.I system compared to RhIII, making a square-planar RhI (4d8) adduct accessible + . HR-MS d Fig. S17.m/z of 461.16 assignable to [13-Cl]+, as was also observed by ESI-MS.Adduct formation was also evident from LC-MS data Fig. S18, showing1H NMR studies. Time-dependent 600 MHz 1H NMR spectra of the reaction mixture of complex 1 and isoprene (10 mol equiv.) in 60% MeOD-d4/40% D2O showed a decrease in the intensity of the isoprene peaks with time, Fig. S19,13). The new peaks due to formation of the [4+2] cyclo-addition adduct are assigned in 1H COSY and NOESY data in RPMI-1640 cell culture medium supplemented with 10% fetal calf serum, a typical medium used for culture of cancer cells Rh(bpy)OH]+. The formation of the Diels\u2013Alder adduct from the fulvene species [ scale\" fill=\"currentColor\" stroke=\"none\">CH2)RhI(bpy)OH2]+ is energetically very favourable (106 kJ mol\u20131), while the corresponding end product [(adduct)RhI(bpy)]+ is presumably driven by entropic effects, with a calculated energy difference between it and the [(adduct)RhIII(bpy)](OH2) of only 3 kJ mol\u20131. The change of the oxidation state is suggested by the calculated Rh\u2013N bond lengths of 2.141 and 2.192 \u00c5 for the species with coordinated water, and 2.106 and 2.102 \u00c5 for the final product.The reaction of [(Cp*)Rh(bpy)Cl]ulations . The res1 with the conjugated fatty acid, -linoleic acid, under similar experimental conditions in water, and in RPMI-1640 cell culture medium supplemented with 10% of fetal calf serum, were studied. The HRMS and MS-MS data again clearly indicated the formation of the fulvene-diene cyclo-addition adduct scale\" fill=\"currentColor\" stroke=\"none\">CH2, or with the dienophile N-methylmaleimide, although they can control the extent of ring deuteration -linoleic acid formed readily in aqueous solution. They might easily form in cells, and influence the redox state of cells and biological activity of this class of organo\u2013rhodium anticancer complexes. The Diels\u2013Alder adducts formed readily in biological media, e.g. cell culture medium (Fig. S22 and S23x rings (Table S3Adducts with isoprene, an abundant diene in human breath, and with the common dietary diene conjugated (9 Table S3. The posThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Using the \u201ccrystal sponge\u201d approach, weak organic electron donor molecules were impregnated and evenly distributed in a crystal of a metal\u2013organic framework (MOF), with the self-assembly of the donor\u2013acceptor pairs with electron acceptor ligands. The nanopores of the MOF confined them and induced a charge transfer phenomenon, which would not occur between donor and acceptor molecules in a bulk scale. N,N,N\u2032,N\u2032-tetramethyl-1,3-propanediamine (TMPDA), was realized in a structurally flexible metal\u2013organic framework, {Mn76(DMA)6}\u221e , with electron-accepting anthraquinone groups, generating two MOF guest charge transfer complexes: {Mn76(DMA)6(TTF)5} and {Mn76(DMA)4(H2O)2(TMPDA)7}. Using a mild impregnation procedure, single crystals of the target complexes were obtained via a crystal-to-crystal conversion, and the crystals were suitable for structural analysis. Single crystal X-ray analysis demonstrated the different arrangements of these intercalated donor molecules: some donor molecules interacted with the anthraquinone groups and formed infinite D\u2013A\u2013A\u2013D stacks, some appeared beside the anthraquinone groups but only formed donor\u2013acceptor pairs, and the remainder of the molecules simply filled the space. The charge transfer between the guests and the framework was spectroscopically confirmed, and the radical densities on the organic species were estimated using magnetic susceptibility measurements. Compared with a solid-state mixture of anthraquinone and donor molecules, the evenly distributed donor molecules in the micropores of the MOF resulted in a \u201csolid solution\u201d state and significantly promoted the degree of charge transfer between donors and acceptors. Such an encapsulation process may be adopted as a new strategy for post-modification of the electronic and magnetic properties of MOFs, as well as for generating new semiconducting charge-transfer complexes.A spontaneous entrapment of electron-donating small guest molecules, including tetrathiafulvalene (TTF) and A few elegant examples have been reported on this topic: Allendorf et al. reported the synthesis of TCNQ@HKUST-1 2}), and the conductivity of HKUST-1 was improved by six orders of magnitude with the infiltration of TCNQ.et al. illustrated VOC (volatile organic compound) detection with thin-film devices made of two-dimensional conductive MOFs.et al. demonstrated the iodine oxidation of TTF -based MOFs, and found that the oxidation modulated the spin-crossover property of the MOF.Metal\u2013Organic Frameworks (MOFs) are a series of polymeric coordination compounds with intrinsic porosity and crystallinity.To understand how guest molecules have tuned the electron transfer ability of MOFs, an important lesson should be learned from the studies of charge transfer molecular conductors such as TTF\u2013TCNQet al. have provided a straightforward yet universal strategy for this goal\u2014namely, the \u201ccrystal sponge\u201d strategy.via this mild guest inhalation process. Such a gentle self-assembly process may not only lead to the impregnation of structurally resolvable guest molecules in a confined space, but may also provide an environment for maximizing the interaction between donor\u2013acceptor pairs and optimizing their packing motifs 6(DMA)6} (Mn-MOF), that was previously reported by our group,76(DMA)6(TTF)5} and {Mn76(DMA)4(H2O)2(TMPDA)7} . They were composed of organic donor guests and an Mn-MOF with electron-accepting anthraquinone (AQ) groups. The crystal structures were successfully acquired through a spontaneous crystal-to-crystal transformation using the \u201ccrystal sponge\u201d method, and the charge transfer between the MOF scaffold and organic guest donor molecules was evidenced by a series of physical property measurements.Fujita g motifs . Herein,The preparation of a Mn-MOF was first described by our group.1 and 2. Single crystal XRD data collection was first carried out on these crystals using a Rigaku RA-micro7 Mercury CCD diffractometer equipped with a Mo K\u03b1 light source (\u03bb = 0.71073 \u00c5) at \u2013150 \u00b0C. Two hemispheres were scanned for each crystal. The frames were integrated with Rigaku Crystal Clear 2.0, and the solving and refinement of structures were completed with Rigaku Crystal Structure 2.0. Based on the crystallographic results from single crystal XRD, we concluded that the data quality of 2 was not adequate for scientific publication. To overcome this problem, synchrotron radiation diffraction was also performed on a crystal of 2 at the Aichi Synchrotron Radiation Center, with beamline BL2S1 (\u03bb = 0.75000 \u00c5). The instrument conditions of the beamline were formerly reported,2. The powder X-ray diffraction patterns were collected on a Rigaku MultiFlex X-ray diffractometer, and the crystals of the as-prepared Mn-MOF guest complexes were roughly ground by sandwiching them between two glass slides to create a crystalline powder. A simulated powder diffraction pattern was generated from the crystal structure using Diamond 3.0 crystallographic imaging software for comparison.X-ray diffraction analysis (XRD) was performed on the single crystals of 4 powder with a weight ratio of 1\u2009:\u200910. The spectrum was taken within a wavelength range of 200\u20131400 nm. To verify the effect of micropores on the charge transfer degree between the donor molecules and functional groups on the MOF, we also performed a reaction between the donor molecules and anthraquinone-containing ligands by dissolving them in hot DMF with a 1\u2009:\u20091 molar ratio. The DMF solution was kept at 120 \u00b0C for 1 hour and the solid-state products were collected by evacuating all the DMF solvent. These products were also examined by solid-state UV-vis diffuse reflectance spectroscopy under the same conditions.A series of physical properties were characterized to investigate the existence of charge transfer phenomena between the host scaffold and the encapsulated guest molecules. The as-prepared Mn-MOF, organic donor molecules, and Mn-MOF guest crystals were analysed by solid-state UV-vis-NIR diffuse reflectance spectroscopy using a JASCO V-570 UV-Vis-NIR spectrophotometer. Due to the limited amount of Mn-MOF guest crystals, the diffuse reflectance measurements were performed by mixing the crystals with BaSO\u03c7\u2013T plot data sets were fitted using the Curie\u2013Weiss law, and the Curie constants were used to calculate the magnetic contribution of the organic radicals. To confirm the presence of organic radicals and exclude the contribution of paramagnetic impurities, temperature variable electron paramagnetic resonance (EPR) measurements were also performed on Mn-MOF and Mn-MOF guest crystals. A JEOL JES-FA200 continuous wave X-band EPR instrument was used to complete this task.The charge transfer degree between the donor molecules and anthraquinone groups was evaluated by temperature variable magnetization measurements, which were performed with a superconducting quantum interference device (SQUID) Quantum Design MPMS system. DC measurement was performed with a magnetic field of 1000 Oe, and the temperature range was 2\u2013300 K. The 2Cl2 solution of these donors and evaporating the solvent. This procedure yielded MOF guest complexes. Fortunately, high quality single crystals could be obtained for both charge transfer complexes, which makes it easy to inspect the structural features of the donor\u2013acceptor pairs in the Mn-MOF guest crystals. After the insertion of the donor molecules, the skeleton of Mn-MOF was not significantly perturbed; however, astonishingly complicated arrangements of organic donor molecules were observed in the structures of both 1 and 2 scale\" fill=\"currentColor\" stroke=\"none\">C double bond are still coplanar, while the five-membered rings are bent along the dithiole line with a torsion angle of \u223c30\u00b0. Such distortion should be a result of weak attractive intermolecular S\u00b7\u00b7\u00b7S interactions, as the S\u00b7\u00b7\u00b7S distance between the adjacent TTF molecules is 3.916 \u00c5. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds of TTF molecules were also examined, since these bond lengths are benchmarks for predicting the oxidation states of TTF species. Interestingly, abnormalities were observed in various types of TTF molecule in the structure. Because they are adjacent to an AQ group, the Type I and Type III TTF molecules were expected to possess a positive charge, and the central C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond was expected to be elongated by the single bond component from the resonance structure compared to that in the neutral, space-filling Type II TTF molecules. In reality, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond lengths of Type I and Type III TTF were 1.334 \u00c5 and 1.335 \u00c5, respectively, and Type II TTF had a central C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond length of 1.383 \u00c5. As a reference, this bond length was 1.337 \u00c5 in neutral TTF and 1.369 \u00c5 in TTF\u2013TCNQ (\u03b4TTF = +0.59).1, it is inappropriate to simply predict the charge transfer degree with bond lengths, and the bond lengths of impregnated TTF are determined by not only the oxidation states, but also the steric effects arising from the limited space in the nanopores in the MOF structure.As shown in 2 .1 and 2 showed a self-arranged placement of donor molecules in these MOF\u2013guest complexes. With the \u201ccrystal sponge\u201d approach, donor molecules will automatically find acceptors, forming columns that are potentially capable of electron transfer.A few of the aforementioned structural features were also observed in compound 2 . For inse Fig. S4. This fi1 and 2 have provided quite a few hints of charge transfer taking place between AQ groups and donor molecules, evidence from physical measurements is still essential to prove the existence of organic radical species. We therefore conducted solid-state diffusive reflectance UV-vis spectroscopy measurements on the original MOF, donor molecules and MOF\u2013guest complexes. By overlaying the absorbance spectrum of the complexes with those of the donor molecules and Mn-MOF, broad new bands were observed for both 1 and 2 at 740 nm and 790 nm, respectively cations. This small Curie constant could be simply explained by the antiferromagnetic (AF) exchange coupling between the Mn(ii) cations within one secondary building unit (SBU). To simplify the analysis, we decided to use the giant spin approximationS = 13/2, g = 2.04 and zJ = \u20130.177 cm\u20131 0.15+ Mn-MOF0.15\u2013 and (TMPDA7)7+ Mn-MOF7\u2013. Although this estimation ignored the potential AF interactions between AQ\u02d9\u2013 and the donor\u02d9+, as well as the AF interactions between metal clusters and organic radicals, it was still qualitatively shown that the impregnated TTF molecules were almost neutral, and the main character of the TMPDA-AQ charge transfer pairs was ionic.Although the crystal structures of ectively . These br Fig. S9. For the1 and 2 were fitted to be \u201315.0 K, \u201315.5 K and \u201321.4 K, respectively. For Mn-MOF and 1, it was suggested that there were antiferromagnetic interactions between the SBUs. Since the skeleton of the framework in all three compounds is nearly identical, a slightly increased critical temperature of 2 might be a sign of the additional antiferromagnetic interactions between the SBUs and organic radicals. We confirmed this assumption with temperature variable EPR measurements , the line width was notably broadened, suggesting that an increased population of excited states was generated by the interaction between the SBUs. A similar feature was also noticed for 1, since the TTF species were almost neutral and contributed no perturbation to the spin states of the Mn7 cluster. In contrast, although the g value was not changed, the line width of 2 was slightly narrower at high temperature, and only slightly broadened when the temperature was lower than the Tc and organic radicals (S = 1/2). Hence, the number of microstates generated by the interactions was dramatically reduced and the 1st oxidation potential of TTF and TMPDA (E1/2 = 0.45 V and 0.37 V vs. EAg/AgCl), the potential differences between the donor and acceptors were larger than 1.0 V in both cases. According to empirical rules, the combination of these donor molecules and AQDC molecules will not lead to a spontaneous formation of charge transfer salts but rather neutral complexes.The cyclic voltammetry experiments of the AQDC ligand, TTF and TMPDA Fig. S2 uneartheBy post-synthetically inserting donor molecules into a flexible MOF with electron-accepting groups, we successfully achieved two MOF guest charge transfer complexes, and the structures of these complexes could be fully resolved using the \u201ccrystal sponge\u201d approach. The nanopores or nanochannels in this MOF played a critical role in this process. The confinement of functional species in a limited space facilitated the guest-to-host electron transfer and yielded ionic charge transfer complexes, even when the redox potential gap between the donor and acceptor species was vast. Meanwhile, an even distribution of the donor molecules in the MOF structure maximized the contact between the donor and acceptor species, which also boosted the degree of charge transfer. The even distribution and confinement could be synergistically achieved in one MOF material, and this synergic effect can be summarized as \u201cMOF-induced charge transfer\u201d (see computational discussion in Section S11, ESIThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Intramolecular N-to-S or N-to-O acyl shifts in peptides are of fundamental and practical importance, as they constitute the first step in protein splicing and can be used for the synthesis of thioester-modified peptides required for native chemical ligation. anti to the carbonyl oxygen, as in a cis amide. Despite the importance of such reactions, an understanding of this geometric restriction remains obscure. Here we argue that the empirical requirement for positioning the nucleophile is a stereoelectronic effect arising from the ease of approach of the nucleophile to a carbonyl group, not ground-state destabilization. DFT calculations on model amides support our explanation and indicate a significant decrease in both the transition-state energy and the activation energy for a cis amide. However, the approach of the nucleophile must be anti not only to the carbonyl oxygen but also to the nitrogen. The direction of approach is expressed by a new, modified B\u00fcrgi\u2013Dunitz angle. Our data shed light on the mechanisms of acyl shifts in peptides, and they explain why a cis peptide might be required for protein splicing. The further implications for acyl shits in homoserine and homocysteine peptides and for aldol condensations are also considered.Intramolecular N-to-S or N-to-O acyl shifts in peptides are of fundamental and practical importance, as they constitute the first step in protein splicing and can be used for the synthesis of thioester-modified peptides required for native chemical ligation. It has been stated that the nucleophile must be positioned N-terminal residue),8Protein splicing is the posttranslational excision of an internal polypeptide sequence, the intein, followed by ligation of the C-terminal and N-terminal segments, thereby generating the spliced extein.anti to the carbonyl oxygen for the N-to-S or N-to-O acyl shift to take place.cis (E) amide, even though the product ester is the same from either . PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO. The difference between cis and trans must be sought elsewhere.These acyl shifts are classified as allowed 5-trans amide reacts more slowly because its geometry restricts the nucleophilic O or S from approaching the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO from the preferred direction. To test this proposal, we have calculated structures and energies for the intramolecular reactions of cis and trans acetamides 1 with O, S, and Se anions , via transition states 2, leading to tetrahedral intermediates 3 /6-311++G calculations were performed with Gaussian 09 software Revision C.01.26\u03c6BD, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO directions scale\" fill=\"currentColor\" stroke=\"none\">O direction and the projection of the C\u2013Nu direction onto the plane containing the C and the two attached groups , which we designate as \u03c6\u2032BD.However, these angles are not appropriate for specifying the preferred direction of approach to an amide. Whereas the nucleophile approaches \u03c6\u2032BD was calculated as follows: first Xnormal, the normal to the OCN plane containing C, O, and N, was calculated as (XO \u2013 XC) \u00d7 (XN \u2013 XC), the cross product between the C\u2013O and C\u2013N vectors. Next PNu, the projection of XNu onto the NCO plane, was calculated as XNu + Xnormal/Xnormal \u00d7 Xnormal. Finally, cos(180\u00b0 \u2013 \u03c6\u2032BD) was evaluated as the normalized dot product (XNu \u2013 XC)(PNu \u2013 XC)/|XNu \u2013 XC||PNu \u2013 XC|.The modified B\u00fcrgi\u2013Dunitz angle cis and trans stereoisomers of extended-chain amide 1, tetrahedral intermediate 3, and transition state 2 connecting them, for X = O, S, and Se, along with the activation energies Ea = E(2) \u2013 E(1). For X = S and Se either HF or HCl, respectively, was coordinated to the carbonyl oxygen in order to converge addition to the amide, which otherwise is thermodynamically unfavorable because RS\u2013 and RSe\u2013 are such stable anions and because C\u2013S and C\u2013Se bonds are weak. Besides, the coordinated acid can mimic the \u201coxyanion hole\u201d, which stabilizes the tetrahedral intermediate in some enzyme-catalyzed reactions.trans amides are a reasonable 2 kcal mol\u20131 more stable than the cis, and the open-chain amides 1 are calculated to be more stable than the high-energy tetrahedral intermediates 3. Moreover, nearly the same results for X = O are obtained with the M06-2X method, which accounts for dispersion,Because the coordination to HF or to HCl, the use of anionic nucleophiles, and the use of PCM are all devices to facilitate the calculations, the absolute energies in cis transition state for both X = O (without HF) and X = S (with HF), by \u223c2.5 kcal mol\u20131. The differences in activation energies are slightly larger, 4\u20135 kcal mol\u20131. These differences thus reproduce the faster cyclization seen for cis amides. However, the faster cyclization is not merely because of the destabilization of a cis amide, but because of the lower energy of the cis transition state, consistent with the Curtin\u2013Hammett Principle. The case of X = Se, omitted from 3. The lengthening is greater for 2trans, especially for X = O or N-methylacetamide HCl. The smaller angles in the cyclic transition states and especially in the trans transition states represent a greater displacement of the nucleophile from the \u03c0* MO of the amide group is due to the greater proportion of a stereoisomer that cyclizes more rapidly, the reason for the faster cyclization is the ease of nucleophilic approach. Moreover, the approach is not simply anti to the carbonyl oxygen, but anti to both O and N.The data in trans amide is a consequence of a greater restriction on the ability of the nucleophile to reach the carbonyl carbon, as manifested by \u03c6\u2032BD < optimum. This is a constraint of the five-membered ring being formed. It is an unusual example of angle strain that differs between cis and trans, even though they are both 5-exo-trig.Approach control has previously been recognized as arising from steric repulsions in the transition state, as in hydride reduction of cyclohexanones.This difference in angle strain is recognizable even with a simple molecular-model kit. Therefore we expect that the order of relative energies in trans is substantially higher than that for the cis. This is simply because of the ground-state steric destabilization of the cis, as originally proposed to explain its greater reactivity. However, the data also show that the transition-state energies for cis and trans differ by less than 1 kcal mol\u20131, much less than the 4\u20135 kcal mol\u20131 for N-to-O and N-to-S shifts. Those shifts of a trans amide are retarded by the inability of the nucleophile to reach the carbonyl carbon. However, because the C\u2013Se bond is longer, the nucleophilic selenium has less difficulty in reaching the carbonyl carbon. However, according to the values in \u03c6\u2032BD is again significantly smaller in the trans transition state, just as for X = O or S, so that this parameter does not reflect the slight difference in transition-state energies. This may be a consequence of C\u2013Se\u2013C angles in both transition states that are constrained near 80\u00b0, thereby distorting the five-membered ring.The N-to-Se acyl shift in a selenocysteine residue provides an instructive contrast. According to the calculated energies in trans mono(selenylethyl) peptide might suffice, although it would be retarded by the lack of the ground-state steric destabilization of the cis isomer.As a corollary, there may be no strong constraint on the approach of the selenium to the carbonyl carbon. Although a bis(selenylethyl) peptide readily undergoes a N-to-Se acyl shift,4 (X = O) or 4 HF (X = S) are nearly equal for cis and trans amides \u03c6FL is calculated to be 55\u00b0 for cis and 50\u00b0 for trans, not far from the 52\u00b0 for OH\u2013 addition to N-methylacetamide. With a six-membered ring there is little restriction on the ability of the nucleophile to reach the carbonyl carbon. Indeed, the N-to-S acyl shift in a homocysteine residue is facile, without any necessity for N-alkylation or population of the cis amide.36In further contrast, according to the data in 7 and its derivatives to the corresponding 8 are known,9 to the corresponding 10. This could be due simply to a lack of demand for 10, but it can also be explained by the difficulty for the enolate carbon of 9 to reach the carbonyl carbon, whereas 7 can twist to allow its enolate carbon to achieve the preferred approach to the carbonyl, as described by the B\u00fcrgi\u2013Dunitz and Flippin\u2013Lodge angles.These results also have implications for aldol condensation . Althougcis acylcysteine or acylserine toward N-to-S or N-to-O acyl shift. The reactivity difference between cis and trans can be attributed to the ease of approach to the carbonyl carbon by the nucleophile, not to ground-state destabilization. This represents an extension of Baldwin's rules to two distinguishable cases of 5-exo-trig ring closures. Moreover, there is no large reactivity difference in an N-to-Se acyl shift or in 6-exo-trig ring closures. We thus have provided a better understanding of the geometric constraints required for the N-to-S or N-to-O acyl shift in cysteine and serine peptides. We expect that this information will enable better design of peptides, especially ones containing homocysteine, that generate thioesters useful for chemical ligation techniques.DFT calculations can reproduce the greater reactivity of a There are no conflicts of interest to declare.Supplementary informationClick here for additional data file."}
+{"text": "Sham electroacupuncture (EA) control is commonly used to evaluate the specific effects of EA in randomized-controlled trials (RCTs). However, establishing an inert and concealable sham EA control remains methodologically challenging. Here, we aimed to systematically investigate the sham EA methods. Eight electronic databases were searched from their inception to April 2015. Ten out of the 17 sham EA methods were identified from 94 RCTs involving 6134 participants according to three aspects: needle location, depth of needle insertion and electrical stimulation. The top three most frequently used types were sham EA type A, type L and type O ordinally. Only 24 out of the 94 trials reported credibility tests in six types of sham EA methods and the results were mainly as follows: sham EA type A (10/24), type B (5/24) and type Q (5/24). Compared with sham EA controls, EA therapy in 56.2% trials reported the specific effects, of which the highest positive rate was observed in type N (3/4), type F (5/7), type D (4/6) and type M (2/3). In conclusion, several sham EA types were identified as a promising candidate for further application in RCTs. Nonetheless, more evidence for inert and concealable sham EA control methods is needed. A randomized controlled trial (RCT) has been the cornerstone of medical clinical research since the first RCT paper entitled \u201cStreptomycin treatment of pulmonary tuberculosis: a Medical Research Council investigation\u201d was published in 1948RCTs for acupuncture appeared in 1970s89Electroacupuncture (EA) is an extension technique based on traditional acupuncture combined with modern electrotherapy1113Eight electronic databases, including Cochrane Controlled Trials Register, PubMed, EMBASE, AMED, China National Knowledge Infrastructure (CNKI), VIP Journals Database, Wanfang database, and Chinese Biomedical Database (CBM) were searched from their inceptions to April 2015. The search terms were confined to \u201cElectroacupuncture\u201d AND \u201csham acupuncture OR placebo acupuncture\u201d AND \u201crandomized controlled trial (RCT)\u201d. All searches were limited to studies on human.RCTs concerning the effects of EA on any kind of diseases with at least one control group receiving sham EA were included, regardless of publication status and languages. Quasi-RCTs and non-RCTs were excluded.The studies were eligible if EA therapy alone or adjunct therapy were given in treatment group and secondly, if sham EA or any type of faked manipulation mimicking real EA in aspects of acupoint, penetration and electro-stimulation were given in control group. There were no restrictions on needle parameters or intensity, frequency and mode of stimulation. Studies that compared EA with transcutaneous nerve electrical stimulation (TNES), another acupuncture plus sham EA or placebo medications were excluded. If three or more groups were designed in one study, only real EA versus sham EA groups were included.Two authors reviewed the titles and abstracts of the potential references independently. All the potentially relevant studies were marked and their full articles were retrieved. Further examinations were carried out to make a final selection decision. The same two authors performed the data extraction independently for the predefined items: author, year, country, EA indications, sample size, the characteristics of interventions, outcome measures, results and dropouts. The disagreements were resolved through consulting a third part (GQZ).Two authors (ZXC and YL) performed the methodological quality assessment of each included trial independently based on the Cochrane Collaboration\u2019s tool for assessing risk of biaset al.The sham EA methods used in each control group were examined and the details were extracted according to three respects: needle location, depth of needle insertion and electrical stimulation. Partially based on the previous sham acupuncture type I~V classification published by Dincer Considering wildly varying outcome measures across different disease conditions, treatment efficacy was evaluated for each study according to the modified method based on a previous publicationThe credibility test was formally performed in validation studies to assess the blinding effect of sham acupuncture based on credibility questionnaire and statistical analysis1516A total of 679 potentially relevant articles were identified. By reviewing titles and abstracts, 374 papers were excluded for at least one of following reasons: (1) not clinical trials; (2) case report, comment, review, letter, news or editorial; (3) not in contrast with sham EA; (4) lack of EA intervention. After examining the full content of the remaining 305 articles, we removed 211 records, of which 127 articles were due to lack of sham EA controls, including electro-acupuncture (14 studies), manual acupuncture (13 studies), TNES (7 studies), other treatment 69 studies) or no treatment 24 studies); 49 articles removed for lack of real EA groups, with their target intervention designed as manual acupuncture (10 studies), TNES 38 studies) or periosteal stimulation therapy (PST) (1 study); 10 articles were not RCTs; 13 articles were double publications; 12 articles were cross-over design. Ultimately, 94 studies181920212223 studies;25262728293031323334353637 studies 394041424344454647484950515253545556575859606162636465666768 studies 707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110The 94 included articles were published from 1992 to 2015. Among them, 5 studies29549095222425273031384547525356575867687172737477788183849293971041051061101819202123262832333435363739404142434446484950515559606162636465666970757679808285868788899194969899100101102103108181921242627313336374042454751525660666772768284889092969710311046507374868994252829346210523535965683249546198996495223938356379834377deqi\u201d sensation was required in 65 real EA groups18192021222324252629303133343536394041434447485051565758596061626364666769717577787980818283858687909193989910010110210410510610961782021235260636719202122262728313233343537394042434446475051586061626465667071777879838589921001041052429545659808286879095989910210710833373839464750515272737782848688899495969710010110227467276777989909727467276778997EA treatment alone was adopted in 55 trials1920212223242526282930313435363738394243535558606166686971727577787980838485868788899091959899100101103104107108110244754384361639899254666899010510610826495476959697Ten different types of sham EA methods used in the trials were identified as follows: (1) sham EA type A were used in twenty-six control groups1819202122313337406066677374768194969710210310410610810923245965848828444749517529436264723861717898992627394346485053546177798589989942686383903032354145565758708086879125343638525563100107For the needle location, 48 sham EA groups252627303234353638394142434546485052535455565758616368697077798083858687899091929598991001011073861717898992627283839424344464748495051535461686971757778798285899899293032354143455657586263647072808386879091929321232531365559636566243719204060671822333876737494961021041051061071081091108423242627383943464850535459616365717778798384858889909598991011819202122252829303132333435363738404142434445474951525556575860626364666768697072737475768081828687919293949697100102103104106107108109110The number of items complied with the criteria varied from 3/8 to 7/8 with the average of 5.2. All 94 studies declared randomization and 63 studies reported the details. Among them, 49 studies18192223242527293536373842434445474951555960616263646566677071728188909192939697989910210610710810911032404150525769737485838718192023252930353637434445555758606163646566676971727679818486889091939899105106107109110222325343645525759606365728188971021031051061071082530456065697980919293979899103105106181920212224252627282930313233343536373839404143444647495051525354555657585960616263646566676870717273747576777879818283848586878889909192949596971001011021031041051081091102342454869809398991063639414244596364757980869193981819202122232425262728293031323334353637383940414243444546474849505152535455566061626364656667687072737475767980838485868788899192939495969799101103104105109575859697881829098102106107108Only 24 out of the 94 studies reported the credibility of blinding in participants by conducting the creditability test in six types of sham EA methods. Twenty-three studies222325343645525759606365728188971021031051061071082260668197102103106108235965882534365245All 94 studies involving 105 comparisons of real and sham EA groups provided the information for between-groups analyses. Among them, 59 real EA groups18192122242830333435373840414243444849515354575960616263646569707172737577787983848687889091929495979910010450Compared with sham EA controls, EA therapy in about 56.2% (59/105 comparisons) of comparisons reported the specific effect. Correspondingly, the real EA was superior to sham EA for type N , type F , type D and type M . The lowest percentage of positive efficacy result was 44.4% (8/18 comparisons) in sham EA type L. The positive rate of efficacy for the three most often used sham EA methods were 50% (13/26 comparisons) for sham EA type A, 44.4% (8/18 comparisons) for sham EA type L and 64.3% (9/14 comparisons) for sham EA type O.The type of sham EA methods varied across different EA indications. The sham EA type A was most commonly used in RCTs for pain, anesthesia and osteoarthritis. The sham EA type D and sham EA type Q were applied mainly in stroke studies. The sham EA type B was commonly applied to RCTs on depression. The sham EA type L and sham EA type O were commonly performed in trials on obesity. The sham EA type F and sham EA type L were commonly used in studies on primary dysmenorrhea.To our knowledge, this is the first systematic analysis to address sham EA methods in RCTs. The numbers of publications and sham EA methods have been increasing every decade. We summarized seventeen kinds of sham EA methods according to three aspects as needle location, depth of needle insertion and electrical stimulation, whereas only ten types of sham EA methods were identified from 94 included RCTs involving 6134 participants. The three predominant types of sham EA methods used were sham EA type A, type L and type O ordinally. Only 24 out of 94 trials reported credibility test with the results of 23 success and 1 failure using six types of sham EA methods mainly as follows: sham EA type A (10/24 with 1 failure), type B (5/24) and type Q (5/24). The remaining 3 sham EA methods were only tested in 4 trials. About 56.2% of comparisons provided the evidence of specific effect of EA therapy, and the four types of Sham EA controls with highest positive rate of efficacy result were type N , type F , type D and type M ordinally. However, all types of Sham EA controls were used in a small number of trials. Thus, the evidence was insufficient to recommend any type of sham EA control despite of the high positive rate. The sham EA control was frequently used in RCTs for pain, anesthesia, stroke, depression, obesity and primary dysmenorrheal/menstrual pain, suggesting that these diseases are particularly worthy of further EA RCTs.et al.et al.The ideal design of sham acupuncture method remains methodologically challenging2627The main purpose of RCTs on EA is to evaluate its specific effect. An optimal sham acupuncture technique must be biologically inactive and psychologically credible181921202123526063671822et al.The top three types of sham EA methods used were sham EA type A, type L and type O. The most frequently applied sham EA method was type A, accounting for a popular belief in its inertness based on its absence of key EA components as needle stimulation and electrical stimulation as well as its indistinguishable manipulation on same therapeutic acupoints. In the present study, the validation of credible participant blinding of this sham EA type was reported by most credibility tests. The debate emerged over the past decades over the inertness of non-penetrating procedure since the slight acupressure effects and physiological activity might be evoked by the tactile stimulation from blunt needle tips even without skin penetration112Sham EA type Q is deemed to be the most inert type of sham EA control because it avoids all therapeutic components, which also probably makes this sham method perceptually and operationally distinguishable from real EA intervention and to some extent results in problematic credibility of blinding in participant. In the present study, the credibility of participant blinding of this sham EA type was endorsed by five studies with credibility test25343652et al.et al.et al.et al.et al.et al.The second commonly used sham EA method was type L. It was found that the differential effects of real EA and sham EA, which were attributed to point location, was not consistent across studies and conditions within this sham EA type, suggesting that EA on non-acupoints might be efficacious as EA on therapeutic acupoints. Furthermore, the improvements from baseline were also observed by Sahin et al.et al.et al.The third commonly used sham EA was type O. During the procedure, the shallow insertion was applied to simulate deep skin penetration and to ensure the blinding of participant. In the present study, the validation of participant blinding of this sham EA type was endorsed by two studies4532465657et al.123124In the present study, six types of sham EA method were reported as successful in blinding. However, further investigations are needed for confirmation, since half of the tested types of sham EA controls were reported in a small number of trials. It should be noted that studies included did not provide sufficient evidence of blinding in acupuncturist. Vase RCTs are generally recognized as the gold standard for the efficacy of clinical interventions by excluding the non-specific effect via a placebo controlIn the present study, 43/105 comparisons reported that EA has no specific effects compared with sham EA controls202324252627293132363943444546475255565863666768768081828589939698101102103105106107109127There are several weaknesses in the present study. Firstly, the search and screen procedure were limited to randomized, parallel-controlled trials published in English. Thus, those trials with cross-over design or published in other than English language were omitted. Secondly, with the aim of evaluating the sham method in RCTs on EA, a generous criterion was established to select eligible studies. Therefore, it was not easy to examine the specific effect of EA by data synthesis from different outcomes and indications because of the heterogeneity of trials. Finally, the reported credibility test addressed blinding effects in participant rather than in both participant and acupuncturist. The credibility tests were not reported in all studies and the number of studies using sham EA types was small, and therefore the conclusion should be interpreted with cautions.Ten types of sham EA methods were identified based on our scheme classification. Generally, sham EA type A, type L and type O were frequently used. Yet, further clinical trials are recommended to maintain standard methodology of concealable and inert placebo EA techniques. Only 24 out of 94 trials were reported as positive credibility test in six types of sham EA methods, where sham EA type A, type B and type Q were highly practiced. It is worthy to study further about the importance of concealable sham EA types. EA therapy in approximately, 56.2% of comparisons provided the specific effects. The four types of sham EA represented the highest positive rate of efficacy results. However, progressive evidences on specific effects are mandatory. The sham EA control was observed frequently in pain, anesthesia, stroke, depression, obesity and primary dysmenorrhea RCTs. Also, broader studies in these predominant diseases are advised.How to cite this article: Chen, Z. et al. Sham Electroacupuncture Methods in Randomized Controlled Trials. Sci. Rep.7, 40837; doi: 10.1038/srep40837 (2017).Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations."}
+{"text": "FeIV=O and/or FeV=O intermediates are suggested to be involved in water oxidation with [NH4]2[CeIV(NO3)6], NaIO4, or Oxone catalyzed by [FeIII(L1)Cl2]+ (1) on the basis of spectroscopic measurements and DFT calculations. III(L1)Cl2]+ pyridinophane) complex is an active catalyst for the oxidation of water to oxygen using [NH4]2[CeIV(NO3)6] (CAN), NaIO4, or Oxone as the oxidant. The mechanism of 1-catalysed water oxidation was examined by spectroscopic methods and by 18O-labelling experiments, revealing that FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and/or FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species are likely to be involved in the reaction. The redox behaviour of 1 and these high-valent Fe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species of L1 has been examined by both cyclic voltammetry and density functional theory (DFT) calculations. In aqueous solutions, the cyclic voltammograms of 1 at different pH show a pH-dependent reversible couple (E1/2 = +0.46 V vs. SCE at pH 1) and an irreversible anodic wave (Epa = +1.18 V vs. SCE at pH 1) assigned to the FeIII/FeII couple and the FeIII to FeIV oxidation, respectively. DFT calculations showed that the E value of the half reaction involving [FeV(L1)(O)(OH)]2+/[FeIV(L1)(O)(OH2)]2+ is +1.42 V vs. SCE at pH 1. Using CAN as the oxidant at pH 1, the formation of an FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reaction intermediate was suggested by ESI-MS and UV-vis absorption spectroscopic measurements, and the rate of oxygen evolution was linearly dependent on the concentrations of both 1 and CAN. Using NaIO4 or Oxone as the oxidant at pH 1, the rate of oxygen evolution was linearly dependent on the concentration of 1, and a reactive FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species with formula [FeV(L1)(O)2]+ generated by oxidation with NaIO4 or Oxone was suggested by ESI-MS measurements. DFT calculations revealed that [FeV(L1)(O)2]+ is capable of oxidizing water to oxygen with a reaction barrier of 15.7 kcal mol\u20131.The macrocyclic [Fe E = +1.23 V vs. NHE at pH 0) involving the simultaneous removal of four electrons and four protons from two water molecules to give one oxygen molecule.Water oxidation is an energetically uphill reaction (ii) and organometallic iridium(iii) complexes, and also complexes of 1st-row transition metals such as manganese, iron and cobalt bearing chelating N and/or O ligands, have been reported for water oxidation.3In the literature, many examples of molecular catalysts, particularly polypyridyl ruthenium(4]2[CeIV(NO3)6]) or NaIO4,4,Because of the high earth abundance of iron and the recent impressive advances made in the isolation and characterization of non-heme iron\u2013oxo complexes, notably by Nam, Que, and co-workers,5 ligands,Me2Pytacn, tpa, and bqen (cis labile sites (the abovementioned 14-TMC ligand forms trans complexes such as trans-[Fe(14-TMC)(OTf)2] which was found to be unreactive for catalytic water oxidation with CAN or NaIO4 (II(mcp)(OTf)2] + NaIO4\u2019 system reported by Costas, Lloret-Fillol, and co-workers formed oxygen with a turnover number (TON) of up to >1000 at pH 2.iv) scale\" fill=\"currentColor\" stroke=\"none\">O) intermediates supported by Me2PytacnIV(bqen)(O)(OH2)]2+ may be involved in O\u2013O bond formation,II\u2013Me2Pytacn system favoured FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reactive intermediates. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV\u2013O\u2013CeIV species in the water oxidation with CAN catalysed by [FeII(mcp)(OTf)2].v) scale\" fill=\"currentColor\" stroke=\"none\">O) species are proposed to be the active intermediates directly responsible for O\u2013O bond formation in water oxidation reactions,III\u2013TAML,II\u2013Me2Pytacn,II\u2013mepV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species, which were generated by oxidation with peracids, H2O2 or tBuOOH in organic solvents, have been reported in the literature.V(TAML)(O)]\u2013,V(Me2Pytacn)(O)(OH)]2+,V(L)(O)(S)]3+ .V(TAML)(O)]\u2013 (H2O)]\u2013 with \u2018[RuII(bipy)3]2+ + Na2S2O8\u2019 in 50% MeCN\u2013borate buffer mixture, was reported to be an active intermediate in the [FeIII(TAML)(H2O)]\u2013-catalysed photochemical water oxidation.V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO intermediates with neutral chelating N ligands and bqen , which aor NaIO4 b). Notab(O)]\u2013 I, generateands II, remain eN,N\u2032-Dimethyl-2,11-diazapyridinophane Cl2]+ (1).III(L1)Cl2][FeCl4] (1\u00b7FeCl4) is an efficient catalyst for the cis-dihydroxylation of alkenes using Oxone as the oxidant, and the generation of an [FeV(L1)(O)2]+ intermediate in the reaction was inferred from high resolution ESI-MS analysis and DFT calculations.1 toward water oxidation. It is noted that ligand L1 has also been employed for developing the oxidation chemistry of other transition metal complexes, including [OsIII(L1)(OH)(OH2)]2+, which can catalyse the cis-dihydroxylation of alkenes by H2O2via a reactive [OsV(L1)(O)(OH)]2+ intermediate,II(L1)(Me)2], which reacts with oxygen to generate [PdIII(L1)(Me)2(OO\u02d9)] followed by protonation to give [PdIV(L1)(Me)2(OOH)]+.2O)2]2+ and electrochemical oxidation of water catalysed by [Mn(L1\u2032)(H2O)2]2+ (L1\u2032 = the N-tBu counterpart of L1) have been reported as well.17hane L1, ,15a a neIII(L1)Cl2]+ (1) for water oxidation with Oxone, as well as CAN and NaIO4, under mild conditions, together with mechanistic studies by means of high-resolution ESI-MS, UV-vis absorption spectroscopy, 18O-labelling experiments, kinetic studies, cyclic voltammetry, EPR analysis, and DFT calculations. During the course of this study, Sun and co-workers communicated their findings on water oxidation with CAN catalysed by [FeII(L1)(MeCN)2]2+.V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species responsible for O\u2013O bond formation in water oxidation catalysed by Fe\u2013L1 systems.In the present work, we report the use of [FeCl4] (1\u00b7FeCl4) exhibited the best performance, affording oxygen with TONs of up to 41 and 32 in 0.1 M HNO3 and in pure water, respectively, after 30 minutes with CAN (840 equiv.) as oxidant .At the outset, a series of iron complexes bearing N1-catalysed water oxidation was investigated by using a mixture of H216O and H218O as the medium and by analysing the gaseous product(s) using GC-MS. With CAN as oxidant, the gaseous products obtained in the first 5 minutes were a mixture of 16O2/16O18O/18O2 with a ratio of 30.0\u2009:\u200949.6\u2009:\u200920.4, which is close to the theoretical value of 26.5\u2009:\u200950.0\u2009:\u200923.5 \u2009:\u2009(7.6\u201339)\u2009:\u2009(0.51\u201312) reported for water oxidation with Oxone catalysed by a MnIII(O)2MnIV complex.19The origin of the oxygen gas produced from the reaction mixture of 0\u2009:\u200923.5 b expecte1-catalysed water oxidation with CAN in 0.1 M HNO3 using different concentrations of CAN (12.5\u2013125 mM) and 1 (6.25\u201325 \u03bcM) were examined; the plots of oxygen evolution (measured by GC) over time are depicted in Fig. S1 and S2 in the ESI.1 was observed, as depicted in The time courses of 1-catalysed water oxidation with NaIO4, the time course (0\u201360 min) plots of oxygen evolution at different concentrations of NaIO4 (12.5\u2013125 mM) and 1 (6.25\u201325 \u03bcM) in 0.1 M HNO3 are shown in Fig. S3 and S4,1 but not on the concentration of NaIO4 in 0.1 M HNO3 catalysed by n Fig. S8, which i2]+ and Oxone (8 equiv.) in MeCN\u2013H2O (5\u2009:\u20091 v/v) by high-resolution ESI-MS revealed a cluster peak at m/z 356.0981, attributed to [FeV(L1)(O)2]+.1 with CAN and NaIO4 in aqueous solution, we performed ESI-MS measurements on the corresponding reaction mixtures.In our previous work, analysis of a reaction mixture of + based on the isotopic distribution, collision-induced dissociation, and 18O-labelling for 30 seconds; the spectrum showed three new cluster peaks at m/z 357.0992, 402.0854 and 448.0815 (O)(OH)]+, [FeIV(L1)(O)(NO3)]+, and [FeIII(L1)(NO3)2]+, respectively. The ESI-MS spectrum for the reaction in 0.1 M HNO3 was conducted in H218O (instead of H216O); the corresponding isotopic patterns and collision-induced dissociation spectrum obtained in the 18O-labelling study are shown in Fig. S17\u2013S19.Before examination of the reaction intermediates in Fig. S13B, assignaFig. S13C resemble1 and NaIO4 (800 equiv.) in 0.1 M HNO3 during the first 30 seconds of the reaction revealed new species at m/z 356.0944 (V(L1)(O)2]+ and [FeIII(L1)(OO\u02d9)(OH)]+. Collision-induced dissociation spectra of the two species are depicted in Fig. S21 and S22.1 with NaIO4 (800 equiv.) was conducted in H2O under similar conditions, a new peak at m/z 356.0937 assignable to [FeV(L1)(O)2]+ was formed within 10 seconds with 5 equiv. of CAN in 0.1 M HNO3 at room temperature was monitored by UV-vis absorption spectroscopy. This reaction immediately (within 10 seconds) generated a new species with \u03bbmax 830 nm and a shoulder near 540 nm with 5 equiv. of NaIO4 or Oxone in 0.1 M HNO3, UV-vis measurements revealed different phenomena from that observed for the \u20181 + CAN\u2019 system. Upon treatment of 1 with NaIO4, a new species with \u03bbmax 830 nm and a shoulder near 540 nm was gradually formed over 10 minutes in 0.1 M HNO3 at room temperature followed by immediate cooling to 6 K is depicted in gavg = 5.54 and the other with g \u2248 2.EPR spectroscopy was employed to examine the reaction mixture of 4\u2013 anion in 1\u00b7FeCl4, we used the ClO4\u2013 salt of 1 and examined its electrochemical properties in 0.1 M HNO3 at pH 1 and in buffered solutions at various pH by means of cyclic voltammetry and rotating disk voltammetry using glassy carbon as the working electrode. The cyclic voltammograms of 1\u00b7ClO4 at pH 1\u20136 are depicted in E1/2 +0.46 V (pH 1) to +0.12 V (pH 6) vs. SCE, a small irreversible oxidation wave II at Epa +1.18 V (pH 1) to +0.86 V (pH 6) vs. SCE, and the onset of a catalytic oxidation wave at +1.4 V (pH 1) to ca. +1.1 V (pH 6) vs. SCE. Both E1/2 of the reversible couple I and Epa of the irreversible wave II shift cathodically by \u223c67 mV per pH unit upon increasing the pH of the redox process corresponding to the reversible couple I increased linearly with the square root of the rotation rate (\u03c91/2). A plot of iL against \u03c91/2 (Levich plot) shows a straight line with R2 = 0.999 in different oxidation states, together with that of the FeIII/FeII couple of 1, were estimated using DFT calculations. To avoid direct calculation of the proton free energy and systematic errors, we computed the redox potentials through isodesmic reactions using the electrochemical proton-coupled electron transfer (PECT) reactions of the cis-(dioxo)ruthenium(vi) complex [RuVI(L2)(O)2]2+ V/FeIVvs. RuV/RuIV, FeIV/FeIIIvs. RuIV/RuIII, and FeIII/FeIIvs. RuIII/RuII) are comparable and can be cancelled out in the calculations of \u0394\u0394G1, \u0394\u0394G2, and \u0394\u0394G3 depicted in reactions (1a)\u2013(3a) and (1b)\u2013(3b).The electrochemical potentials of iron\u2013oxo complexes [Fe(L1)(O)(X)]V/RuIV, RuIV/RuIII and RuIII/RuII couples,V/FeIV, FeIV/FeIII and FeIII/FeII couples can be calculated as:E(FeV/FeIV) = E(RuV/RuIV) + \u0394\u0394G1E(FeIV/FeIII) = E(RuIV/RuIII) + \u0394\u0394G2E(FeIII/FeII) = E(RuIII/RuII) + \u0394\u0394G3where E(RuV/RuIV) = +0.72 V, E(RuIV/RuIII) = +0.63 V, and E(RuIII/RuII) = +0.26 V at pH 1 according to the experimental findings.20From the DFT computed \u0394\u0394G1, \u0394\u0394G2 and \u0394\u0394G3 values, and the experimental redox potentials of the RuIII/FeII and FeIV/FeIII redox potentials at different pH by using three commonly used density functionals (DFs): BPW91 (pure-GGA), B3LYP (hybrid-GGA), and M06L (meta-GGA). A correlation between the experimental redox potentials of FeIII/FeII and FeIV/FeIII and those calculated using these DFs is depicted in note of caution: calculated redox potentials are thermodynamic values). It is evident that BPW91 and B3LYP led to marked-to-severe (up to ca. +0.57 V) overestimation of the E1/2 of FeIII/FeII, although B3LYP showed good performance in the prediction of the electrochemical potential of FeIV/FeIII. Only M06L gave good estimations of the electrochemical potentials of both FeIII/FeII and FeIV/FeIII at different pH with a linear fit (E(M06L) = E(expt) + 0.06, R = 0.998, SD = 0.03) between the calculated redox potentials and the experimental data. Hence, M06L was chosen for the subsequent DFT calculations in this work. In the literature, the M06L functional has been reported to show good performance in modelling water oxidation by rutheniumWe calculated the FeKa values, as an example, the pKa of [FeV(L1)(O)(OH)]2+ was calculated based on the following pair of isodesmic reactions (reactions (4a) and (4b)).Ka([FeV(L1)(O)(OH)]2+) = pKa([RuV(L2)(O)(OH)]2+) \u2013 \u0394\u0394G4/2.303RTwhere pKa([RuV(L2)(O)(OH)]2+) = 1.8 according to the experimental study.20For the calculation of the pV/FeIV, FeIV/FeIII and FeIII/FeII couples, including those of [Fe(L1)(O)(X)]n+ , along with the calculated pKa values, are depicted in Ka of the [FeV(L1)(O)(OH)]2+/[FeV(L1)(O)2]+ equilibrium is 3.0; (2) the calculated E1/2 of [FeV(L1)(O)(OH)]2+/[FeIV(L1)(O)(OH2)]2+ (+1.42 V vs. SCE at pH 1) is comparable to the E1/2 of CeIV/CeIII (+1.38 V vs. SCE) and close to the calculated E1/2 values of [FeV(L)(O)(OH)]2+/[FeIV(L)(O)(OH2)]2+ with L = Me2Pytacn or mep ; (3) the calculated E1/2 of [FeIV(L1)(O)(OH2)]2+/[FeIII(L1)(OH)(OH2)]2+ (+1.25 V vs. SCE at pH 1) matches the experimental Epa value of FeIV/FeIII ; (4) the calculated E1/2 of the FeIII/FeII couple is +0.49 V at pH 1, which matches the experimental E1/2 value for FeIII/FeII well; (5) the calculated E1/2 of the FeV/FeIII couple (E1/2 = +1.34 V vs. SCE at pH 1) coincides with the catalytic oxidation wave at +1.4 V observed in the cyclic voltammogram of 1 at pH 1. It is noted that there is just 170 mV difference in the calculated E1/2 values of [FeV(L1)(O)(OH)]2+/[FeIV(L1)(O)(OH2)]2+ and [FeIV(L1)(O)(OH2)]2+/[FeIII(L1)(OH)(OH2)]2+ at pH 1.The calculated redox potentials for various FeV(L1)(O)2]+ is a quartet state with three unpaired electrons; the lowest-lying excited state is a sextet state which is 2.8 kcal mol\u20131 higher in energy than the ground state. A quartet ground state for an FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species has previously been predicted by DFT calculations for [FeV(Me2Pytacn)(O)(OH)]2+. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO distance in [FeV(L1)(O)2]+ in the quartet state (4FeV) is 1.614 \u00c5, which is shorter than that in the sextet state due to the antibonding character of the d1 and d2 orbitals scale\" fill=\"currentColor\" stroke=\"none\">O distances were reported for [FeV(L1)(O)2]+ (1.613\u20131.638 \u00c5), computed at the B3LYP/6-31(G) (lanl2dz) level in our previous work, and for [FeV(Me2Pytacn)(O)(OH)]2+ (1.63 \u00c5)V(TAML)(O)]\u2013 (1.60 \u00c5).V(L1)(O)2]+ calculated in this work is shown in V(L1)(O)2]+ (3 configuration in accordance with the assignment of the Fe(v) oxidation state.The ground state of + , right rIV(L1)(O)(OH)]+ is a quintet state with four unpaired electrons, and the triplet state is 16.0 kcal mol\u20131 higher in energy. The computed Fe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO distance of [FeIV(L1)(O)(OH)]+ (5FeIV) in the ground state is 1.632 \u00c5, very close to the experimental Fe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO distance in [FeIV(N4Py)(O)]2+ (1.639(5) \u00c5).5IV(L1)(O)(OH)]+. Fe has the largest spin density of 3.1; the oxo and hydroxyl groups have spin densities of 0.59 and 0.18, respectively. The MO diagram of [FeIV(L1)(O)(OH)]+ oxidation state.The ground state of [FeO)(OH)]+ , right rS = 3/2, 4FeV) and sextet states of [FeV(L1)(O)2]+ were considered in the mechanism studies. The doublet state (S = 1/2) of [FeV(L1)(O)2]+ was found to be the most energetically unfavourable and was not considered in this work. 4RC1/6RC1, formed between 4FeV/6FeV and the substrate (water molecule), which proceeds to the transition state 4TS1/6TS1 in which an O\u00b7\u00b7\u00b7O bond and an O\u00b7\u00b7\u00b7H bond are formed. The ground state is 4RC1, which is 2.8 kcal mol\u20131 lower in energy than 6RC1. The free energy barrier (\u0394G\u2021) for the quartet state is 15.7 kcal mol\u20131, lower than that for the sextet state . Both activation barriers are comparable to those for the similar oxidation of water by [FeV(TAML)(O)]\u2013 V(Me2Pytacn)(O)(OH)]2+ .6INT1 being 6.4 kcal mol\u20131 more stable than the quartet state 4INT1. The location of the minimum energy crossing point (MECP) between the sextet and quartet states was found using the code developed by Harvey and co-workers.\u20131 higher than that of 4INT1, suggesting that spin state reversion can easily occur, leading to the more stable complex 6INT1.Both the quartet (6INT1 complex can subsequently be oxidized by [FeV(L1)(O)2]+ (4FeV) to give the superoxo complex [FeIII(L1)(OO\u02d9)(OH)]+ (7INT2/5INT2). Meanwhile, 4FeV is reduced to [FeIV(L1)(O)(OH)]+ (5FeIV). The subsequent reaction steps include exchange of an oxygen molecule by a water molecule and the release of 3O2/1O2 (reaction (5)). The search for the transition state has not been successful. A barrier of 8.8 kcal mol\u20131 for the release of O2 from [TAML\u2013FeIV\u2013OO\u02d9]\u2013 was reported by Crammer and co-workers.2, complex [FeII(L1)(OH2)(OH)]+ (5FeII) with a quintet state ground state is formed; this complex can further comproportionate with [FeIV(L1)(O)(OH)]+ (5FeIV) to regenerate two [FeIII(L1)(OH)2]+ (6FeIII) molecules.The cis non-planar coordination geometry. The macrocyclic N4 ligand L1 scale\" fill=\"currentColor\" stroke=\"none\">O species of L1, including [FeV(L1)(O)2]+, in the cis-dihydroxylation of alkenes with Oxone catalysed by [FeIII(L1)Cl2]+ (1),V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species were proposed to be the reactive intermediates in iron-catalysed water oxidation reactions reported in the literature.The main objective of this work is to gain insight into the mechanism of water oxidation by iron complexes of tetradentate macrocyclic ligands with a 4 or Oxone was used as oxidant.During optimization of the reaction conditions, it was noted that although the turnover number of oxygen increased with oxidant concentration, the oxidant efficiency (defined in note c of 2] + CAN\u2019 system (which can oxidize water to O2 in non-buffered aqueous solution but not in 0.1 M HNO3 solution),1 + CAN\u2019 system produced oxygen with comparable TONs in water and in 0.1 M HNO3 (OTf)2]II(L1)(MeCN)2]2+ following the order Oxone > CAN > NaIO4 obtained in the 18O-labelling studies, the oxygen evolved in the \u20181 + Oxone\u2019 system originated not only from Oxone but also from water (OTf)eCN)2]2+ g used asII(mcp)(OTf)2] for water oxidation, as reported by Costas, Lloret-Fillol and co-workers,II(mcp)Cl2]III(L1)Cl2]+ (1) for water oxidation. Under our reaction conditions with catalyst/oxidant = 1\u2009:\u2009840, the amounts of oxygen formed in [FeII(mcp)Cl2]-catalysed water oxidation in 0.1 M HNO3 with CAN and NaIO4 as oxidants were approximately 1.4 times (TON = 56) and 2.9 times (TON = 35) the amounts formed in the 1-catalysed reactions, respectively. Changing the catalyst/oxidant ratio from 1\u2009:\u2009840 to 1\u2009:\u200910\u2009000 led to an increase in the TON for oxygen formation from 41 to 93 for \u20181 + CAN\u2019, from 56 to 177 for \u2018[FeII(mcp)Cl2] + CAN\u2019, from 12 to 44 for \u20181 + NaIO4\u2019, and from 35 to 114 for \u2018[FeII(mcp)Cl2] + NaIO4\u2019. These results showed that [FeII(mcp)Cl2] is more active than 1 in catalysing water oxidation.Considering the excellent catalytic ability of 2+/[FeII(L1)(OH2)2]2+ redox couple and the assignment of wave II to the oxidation of [FeIII(L1)(OH)(OH2)]2+ to [FeIV(L1)(O)(OH2)]2+. Despite the low scan rate of 5 mV s\u20131 for the rotating disk voltammetry, the magnitude of the current recorded for the [FeIV(L1)(O)(OH2)]2+/[FeIII(L1)(OH)(OH2)]2+ oxidation wave is not the same as that recorded for the [FeIII(L1)(OH)(OH2)]2+/[FeII(L1)(OH2)2]2+ redox process. As the oxidation of FeIII\u2013OH to an FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species involves the deprotonation of an Fe\u2013OH unit, the electrochemical oxidation would be kinetically slow and highly sensitive to the electrode surface. Indeed, the electrochemical oxidation of Ru\u2013OH2/Ru\u2013OH to a Ru PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species is well documented to be significantly affected by the nature/surface of the working electrode.IV/FeIII) and couple I (FeIII/FeII) is about 700 mV. For a ruthenium complex supported by the mcp ligand,IV(mcp)(O)(OH2)]2+/[RuIII(mcp)(OH)(OH2)]2+ and [RuIII(mcp)(OH)(OH2)]2+/[RuII(mcp)(OH2)2]2+ couples is 550 mV, which is 150 mV smaller than that between the iron analogues and can be attributed to the stronger \u03c0-bond formed in the RuIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO moiety. There is a previous report on the observation of a pH-dependent reversible couple assigned as a proton-coupled electron transfer FeIV/FeIII couple for [FeIV(N4Py)(O)]2+ -bis(2-pyridyl)methylamine) in buffered aqueous solution (pH 1.5\u20134) with an E1/2 value of +0.41 V vs. SCE at pH 4 .III/FeII couple was not reported for [FeIV(N4py)(O)]2+. The E1/2 value of +0.41 V for the [FeIV(N4py)(O)]2+/[FeIII(N4py)(OH)]2+ couple in aqueous solution at pH 4 is unexpectedly low. Should this be the case, the corresponding FeIII/FeII couple would have to occur at a potential less than 0.0 V vs. SCE based on the DFT calculations in this work. Our DFT calculations using the M06L functional gave redox potentials of +1.21 V vs. SCE for the [FeIV(N4py)(O)]2+/[FeIII(N4py)(OH)]2+ couple and +0.3 V vs. SCE for the [FeIII(N4py)(OH)]2+/[FeII(N4py)(OH2)]2+ couple at pH 1. The observation of a catalytic wave for 1 (IV/FeIII) at, for example, Epa +1.18 V vs. SCE (pH 1), which is comparable to the DFT-calculated potential of +1.25 V vs. SCE (pH 1) for the [FeIV(L1)(O)(OH2)]2+/[FeIII(L1)(OH)(OH2)]2+ couple, corroborates the finding that 1 can catalyse water oxidation through iron\u2013oxo species at oxidation states beyond FeIV.The cyclic voltammetric and rotating disk voltammetric measurements of ve for 1 and S27\u20201 in water (OH)2]+, suggests rapid exchange of the Cl\u2013 ligands of 1 with solvent. The new signals, generated upon addition of CAN, at m/z 357.0992, 402.0854, and 448.0815 can be attributed to [FeIV(L1)(O)(OH)]+ (O)(NO3)]+ (NO3)2]+ (18O)(18OH)]+ (18O)(N16O3)]+ (18O)(16OH)]+ and [FeIV(L1)(16O)(18OH)]+ were not detected in the experiment, indicating that the oxygen atoms of the hydroxide and oxo ligands in [FeIV(L1)(O)(OH)]+ come from water and not from CAN.ESI-MS analysis of a solution of 1 with CAN scale\" fill=\"currentColor\" stroke=\"none\">O species of L1, with reference to the characteristic bands of FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species (ranging from 700\u2013850 nm) reported in the literature.IV(L1)(O)(OH)]+ and [FeIV(L1)(O)(NO3)]+ by ESI-MS. We further examined the intensity of the cluster peak at m/z 357.0992, attributed to [FeIV(L1)(O)(OH)]+, at different reaction times. The ion count of this signal decreased with reaction time, as depicted in Fig. S32,\u03bbmax 830 nm assigned to the FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species in the UV-vis spectra shown in IV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species of chelating N-donor ligands have been reported to be reasonably stable, with half-lives generally ranging from 2 to 60 hours.IV(mcp)(O)(H2O)]2+ species (generated in situ from [FeII(mcp)(OTf)2] and CAN in aqueous solution), which could persist under catalytic conditions with a half-life of 2.4 hours,IV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species of L1 decayed with a half-life of 107 seconds under these conditions scale\" fill=\"currentColor\" stroke=\"none\">O species upon oxidation of 1 with CAN in aqueous solution, as supported by ESI-MS and UV-vis analysis, together with the absence of an induction period for oxygen evolution, an FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species is suggested to be involved in water oxidation by the \u20181 + CAN\u2019 system. Kinetic studies revealed a linear dependence of the initial rate of oxygen evolution on the concentrations of both CAN and 1 (IV(L1)(O)(OH)]+, and one equivalent of CAN. One of the possibilities is the oxidation of [FeIV(L1)(O)(OH)]+ by CAN to give FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species, such as [FeV(L1)(O)(OH)]2+ or [FeV(L1)(O)2]+, and another possibility is the reaction of [FeIV(L1)(O)(OH)]+ with CAN to form an O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV\u2013O\u2013CeIV species similar to that recently reported for the \u2018[FeII(mcp)(OTf)2] + CAN\u2019 system,V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV\u2013O\u2013CeIV species have not been clearly detected in ESI-MS analysis of the reaction mixture of 1 with CAN in H2O.Given the instant generation of an FeAN and 1 , which s1 + NaIO4\u2019 system, the new signals at m/z 356.0944 (major) and 373.0940 (minor), revealed by ESI-MS analysis of a mixture of 1 and NaIO4 in 0.1 M HNO3 (V(L1)(O)2]+ and [FeIII(L1)(OO\u02d9)(OH)]+ , respectively. The assignment of [FeV(L1)(O)2]+ is supported by 18O-labelling studies, revealing a shift of the signal at m/z 356.0944 to m/z 360.1042 attributable to [FeV(L1)(18O)2]+ upon changing the reaction medium to H218O (18O)2]+ could come from H218O directly and/or from 18O-incorporated IO4\u2013. Changing the reaction medium from 0.1 M HNO3 to pure water reduced the intensity of the signal assigned to [FeV(L1)(O)2]+; this observation is in line with the smaller TON of oxygen produced in pure water than in 0.1 M HNO3 (O)2]+ in this work and on [FeV(Me2Pytacn)(O)(OH)]2+ in the literatureV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species supported by these neutral chelating N ligands all adopt a quartet ground state (S = 3/2), different from the doublet ground state (S = 1/2) of [FeV(TAML)(O)]\u2013 complexes, which bear tetraanionic tetraamide ligands and have been detected by EPR spectroscopy.V(TAML)(O)]\u2013 using the M06L functional, which revealed a doublet ground state for this species, consistent with previous DFT calculations reported in the literature.V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species with S = 3/2 ground state has been characterized by EPR spectroscopy. The X-band EPR spectrum of the reaction mixture of 1 with NaIO4 in 0.1 M HNO3 species whereas the latter probably arose from decomposed NaIO4, as a similar S = 1/2 signal was observed in the X-band EPR spectrum of a solution of NaIO4 in 0.1 M HNO3 recorded at 7 K (O)2]+ species by EPR since the signal of this S = 3/2 FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species, which is likely to have a low concentration, could easily be masked by the S = 5/2 signal.The DFT calculations on [Fe1 M HNO3 is domin Fig. S33. EPR sigV(L1)(O)2]+ from the oxidation of 1 with NaIO4 resembles the generation of [FeV(L1)(O)2]+ from Oxone;4 and Oxone are typically two-electron oxidants and can directly oxidize Fe(iii) to Fe(v). UV-vis spectroscopy revealed that the reaction of 1 with NaIO4 or Oxone is different from the reaction of 1 with CAN, as exemplified by the immediate formation of a new band at \u03bbmax 830 nm attributable to an FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species in the \u20181 + CAN\u2019 system scale\" fill=\"currentColor\" stroke=\"none\">O species.Generation of + and [FeV(L1)(O)2]+ based on ESI-MS analysis; their protonated forms [FeIV(L1)(O)(OH2)]2+ and [FeV(L1)(O)(OH)]2+ could be involved as well (O)2]+, [FeV(L1)(O)(OH)]2+ also adopts a quartet ground state, with the doublet state being \u223c15 kcal mol\u20131 higher in energy, according to DFT calculations. The possible involvement of the FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO reactive species in the reaction is supported by the reasonably low reaction barrier for the oxidation of water by [FeV(L1)(O)2]+ of 15.7 kcal mol\u20131 obtained by the DFT calculations (V(L1)(O)(OH)]2+, the reaction barrier for O\u2013O bond formation with water was calculated to be 21.0 kcal mol\u20131 (O)2]+. The FeV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO species is suggested to be attacked by water molecules, assisted by hydrogen-bond interactions, leading to the formation of an O\u2013O bond, analogous to the O\u2013O bond formation in water oxidation by MnV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO,IV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV\u2013O\u2013CeIV speciesIV(L1)(O)(OH2)]2+/[FeIII(L1)(OH)(OH2)]2+ and +1.42 V for [FeV(L1)(O)(OH)]2+/[FeIV(L1)(O)(OH2)]2+ at pH 1. The resulting iron(iii)\u2013peroxo intermediate in 4, or Oxone) to give [FeIII(L1)(OO\u02d9)(OH)]+ (OO\u02d9)(OH)]+/[FeIII(L1)(OOH)(OH)]+: +0.64 V vs. SCE), the presence of which is supported by ESI-MS analysis (OO\u02d9)(OH)]+ with water; the resulting [FeII(L1)(OH)(OH2)]+ is oxidized by the sacrificial oxidant to regenerate the catalyst [FeIII(L1)(OH)2]+ (OH)2]+/[FeII(L1)(OH)(OH2)]+: +0.26 V vs. SCE).On the basis of the above findings, a mechanism involving Feulations . For + and/or iron(v)\u2013oxo species such as [FeV(L1)(O)2]+, or their protonated forms [FeIV(L1)(O)(OH2)]2+ and/or [FeV(L1)(O)(OH)]2+, in the 1-catalysed water oxidation reactions.A mononuclear iron(Supplementary informationClick here for additional data file."}
+{"text": "The ambient temperature hydrometallations of a variety of unactivated alkene and alkyne substrates using two-coordinate hydrido-tetrylenes, :E(H)(L\u2020) , are reported. \u2020) (SiPri3); Ar\u2020 = C6H2{C(H)Ph2}2Pri-2,6,4), with a variety of unactivated cyclic and acyclic alkenes, and one internal alkyne, lead to the rapid and regiospecific hydrometallation of the unsaturated substrate at ambient temperature. The products of the reactions, [L\u2020E(C2H4R)] , [L\u2020E{CH(CH2)3(CH2)n}] and , include the first structurally characterised examples of two-coordinate amido/alkyl germylenes and stannylenes. The cycloalkene hydrometallation reactions are cleanly reversible under ambient conditions, a process which computational and experimental van't Hoff analyses suggest proceeds via \u03b2-hydride elimination from the metal coordinated cycloalkyl ligand. Similarly, the reactions of :Ge(H)(L\u2020) with 1,5-cyclooctadiene and 2-methyl-2-butene, both likely proceed via \u03b2-hydride elimination processes, leading to the clean isomerisation of the alkene involved, and its subsequent hydrogermylation, to give [L\u2020Ge(2-cyclooctenyl)] and [L\u2020Ge{C2H4C(H)Me2}], respectively. Reactions of [L\u2020GeEt] and [L\u2020Ge(C5H9)] with the protic reagents, HCl, NH3 and EtOH, lead to oxidative addition to the germanium(ii) centre, and formation of the stable chiral germanium(iv) complexes, [L\u2020Ge(C5H9)(H)Cl] and [L\u2020Ge(Et)(H)R] (R = NH2 or OEt). In contrast, related reactions between [L\u2020SnEt] and ButOH or TEMPOH proceed via ethane elimination, affording the tin(ii) products, [L\u2020SnR] (R = OBut or OTEMP). In addition, the oxidation of [L\u2020Ge(C6H11)] and [L\u2020Sn(C2H4But)] with O2 yields the oxo-bridged metal(iv) dimers, [{L\u2020(C6H11)Ge(\u03bc-O)}2] and [{L\u2020(ButC2H4)Sn(\u03bc-O)}2], respectively.Reactions of the solution stable, two-coordinate hydrido-tetrylenes, :E(H)(L While much less studied than boranes, a variety of electron deficient, polar hydride complexes of aluminium, the heavier group 13 metals,The 1,2-addition of element-hydrogen bonds across the carbon\u2013carbon unsaturations of alkenes and alkynes is of immense importance to organic synthesis. In this respect, and since Brown's seminal work on the hydroboration of alkenes in the 1950's,iv) hydrides do not possess any vacant valence orbitals, it is not surprising that they are poorly effective for the hydroelementation of alkenes and alkynes, at least in their own right. However, reactions of this type (particularly hydrosilylations) are of considerable synthetic importance, and can proceed, for example, in the presence of transition metal catalysts or radical initiators; and/or when subjected to UV irradiation or elevated temperatures.Considering that neutral group 14 element(ii) hydride complexes, a small number of which hydride, I, has been shown to hydrosilylate cyclopentene and a series of terminal olefins at elevated temperatures (70\u2013120 \u00b0C) and in the presence of large excesses of the alkene substrate.anti-Markovnikov product predominates. In one case, i.e. the reaction with trimethylsilylethylene, the reaction proceeds via an isolated [2 + 1] cycloadduct, viz. the silirane , which exists in equilibrium with I and free H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC(H)(SiMe3) at ambient temperature. With respect to hydrogermylation and hydrostannylation reactions, the three-coordinate species, II and III, have been shown to cleanly hydrometallate activated (ester substituted) terminal and internal alkynes at ambient temperature.ii) hydride complexes, IV and V, react with tert-butylethylene at ambient temperature over 48 hours to give the alkyl/aryl substituted ditetrelenes [{Ar\u2032E(CH2CH2But)}2] 2-2,6; E = Ge or Sn). Contrastingly, after 48 hours, the reaction of IV with excess cyclopentene at ambient temperature yielded only a mono-hydrogermylation product, viz. the hydrido-digermene, (Cp = cyclopentyl).IV to the two-coordinate hydrido-germylene, Ge(H)Ar\u2032, in solution is minimal.It would be a significant advantage if the addition of group 14 element-hydrogen bonds to unsaturated hydrocarbons could be effected in the absence of catalysts or initiators, and in a facile manner under ambient conditions. The first hints that this might be possible came with the kinetic stabilisation of group 14 elementGe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe(H)L\u2020] 1 (L\u2020 = \u2013N(Ar\u2020) (SiPri3); Ar\u2020 = C6H2{C(H)Ph2}2Pri-2,6,4),e.g. [L\u2020Sn(\u03bc-H)2SnL\u2020] 2.\u2020) (E = Ge 3 or Sn 4), in hydrocarbon solutions. Subsequently, two-coordinate hydrido-germylenes, bearing even bulkier amide ligands, e.g. [:Ge(H)(LOBut)] (LOBut = \u2013N(Ar\u2020){Si(OBut)3}) were isolated in the solid state.3 and 4 possess empty p-orbitals at their metal centres (cf. boranes) it was proposed that they would act as effective reagents for the hydrometallation of unsaturated substrates. This was shown to be the case for aldehydes and ketones, and, indeed, 3 and 4 were also shown to be highly efficient catalysts for the hydroboration of the same substrates.Recently, we have utilised extremely bulky amide ligands, developed in our group,(i)3 (as an equilibrium mixture with 1) with 1\u20131.5 equivalents of a range of unactivated terminal or cyclic alkenes, or 1 atm. of ethylene, led to almost instantaneous changes in the colour of the reaction solutions from orange to yellow at ambient temperature. This indicated that the hydrometallation reactions were complete in well under 1 minute. 1H NMR spectroscopic analyses of the reaction mixtures after ca. 10 min confirmed that the hydrometallation reactions were essentially quantitative after that time, affording the amido/alkyl germylenes, 5\u201310 (ii) hydride 4 (as an equilibrium mixture with 2) were carried out at low temperature (\u201380 \u00b0C) due to the mild thermal instability of 4 at room temperature . It is also of note that the hydrometallations of all of the terminal alkenes regiospecifically yielded the anti-Markovnikov product, as is typically the case with alkene hydroborations.The facility of these uncatalysed olefin hydrogermylation and hydrostannylation reactions is unprecedented, and is likely a result of them preferentially involving the monomeric hydridoterylenes, 5\u201313 are thermally stable in the solid state. The solution state NMR spectroscopic data for the compounds are fully consistent with their proposed monomeric structures, and do not warrant further comment here. X-ray crystallographic studies were used to confirm the monomeric nature of all compounds, which represent the first structurally characterised examples of two-coordinate amido/alkyl germylenes and stannylenes. Illustrative examples of the molecular structures of the compounds are depicted in 8, 10, 11 and 13), while selected geometrical parameters are collected in 7 and 12 confirmed the molecular connectivity of the compounds, they are not of a quality suitable for publication, and their geometrical parameters will not be discussed here.5\u201310 . The clC (3.87 \u00c5), which 3 and 4 as reagents for the hydrometallation of alkenes, it seemed likely that they would also be very reactive toward unactivated alkynes. To assess this, and to investigate if the metal hydrides could doubly hydrometallate alkynes, 1-phenyl-1-propyne was treated with two equivalents of either 3 or 4. Analysis of the reaction mixtures indicated that only one hydrometallation event occurred in both cases, and within several minutes at ambient temperature. These reactions afforded compounds 14 and 15 respectively, in close to quantitative NMR spectroscopic yields, and moderate isolated yields. The reactions proceeded with complete regiospecificity, giving the cis-isomer with the L\u2020E fragment bonded to the phenyl substituted alkenenic carbon which reveal both to be monomeric in the solid state with the alkeneic phenyl and methyl substituents cis- to one another. Their C(45)\u2013C(46) distances reflect localised double bonds, while the geometries about the metal centres are similar to those in 5\u201313. That is, the CNSi and NEC fragments are close to co-planar with one another, which allows for the possibility of N \u2192 E \u03c0-bonding in the compounds. In contrast, their C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC units are close to orthogonal to the NEC fragments, which discounts the possibility of any \u03c0-delocalisation over those fragments.Both (ii)9 and 10, it was noticed that 1H NMR spectra (C6D6) of pure samples of the compounds reproducibly exhibited signals due to the presence of small amounts of the germanium hydride equilibrium mixture, 1 and 3, and the free cycloalkene. In addition, recrystallisation of the compounds, and 8, repeatedly led to co-crystallisation with small amounts of 1. Moreover, C6D6 solutions of the tin cyclopentyl compound, 13, decomposed over several days at ambient temperature , yet were stable for extended periods, even at 80 \u00b0C, in the presence of excess cyclopentene. All of these observations point to the hydrometallation products from the reactions of 3 and 4 with cycloalkenes being in equilibria with significant amounts of those reactants at room temperature (see 3 and 9). The net decomposition of 13 can be explained by the mild instability of the tin hydride 4 at ambient temperature, which upon decomposition, inextricably leads to loss of 13 from the equilibrium mixture in that case.During characterisation of the cycloalkene hydrogermylation products 9 was explored by a VT 1H NMR spectroscopic study of a sample of the compound which was prepared by reaction of CyMgBr (Cy = cyclohexyl) with L\u2020GeCl. This ensured the absence of any 1 in the purified sample of 9 used for the experiment. Despite this, dissolution of the compound in C6D6 again revealed the presence of a small amount (ca. 5% as determined by 1H NMR spectroscopy) of the 1/3 equilibrium mixture, and cyclohexene, as determined by a 1H NMR spectrum acquired at 20 \u00b0C. Heating the solution to 60 \u00b0C led to an increase in the quantities of these starting materials, which decreased when the solution was again cooled back to 20 \u00b0C. A van't Hoff analysis of this reversible process over the temperature range 304\u2013314 K (see H\u00b0 = \u2013172 kJ mol\u20131) with a relatively large entropic factor (\u0394S\u00b0 = 395 J mol\u20131). Accordingly, the Gibb's free energy for the exergonic hydrogermylation reaction at 298 K is fairly small (\u0394G = \u201354 kJ mol\u20131), and therefore the weakly endergonic reverse reaction might be expected to be become more pronounced at elevated temperatures.The reversibility of the reaction that gave 14 K see revealed8\u201310 and 13. Indeed, inspection of the crystal structures of the compounds revealed, in each case, that the distance between the metal centre and the closest cycloalkyl \u03b2-hydrogen atom (range: 2.62\u20132.99 \u00c5) is significantly less than the sum of the van der Waal's radii for E and H scale\" fill=\"currentColor\" stroke=\"none\">CBut, by a three-coordinate germanium(ii) hydride, [(MesNacnac)GeH] (MesNacnac = [(MesNCMe)2CH]\u2013, Mes = mesityl), which reversibly affords the phosphaalkenyl complex, .MesNacnac)GeC(But) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPH].It is possible that the observed reverse reactions are due to \u03b2-hydride elimination processes, which are enabled by the coordinatively unsaturated nature of the two-coordinate metal centres in n 3.28 \u00c5 ). As far8\u201310, DFT calculations were carried out at several levels of theory on the hydrogermylation reaction that gave 9 (see ESIG = \u201342.3 kJ mol\u20131 at M06-2X+D3/def2-TZVPP//TPSS+D3/def2-TZVPP) that is small, and not dissimilar to that found from the experimental van't Hoff analysis of the reaction. Importantly, the reverse reaction was, indeed, found to proceed via a \u03b2-hydride elimination process, involving a transition state with a four-membered GeC2H ring (see \u2021G = 76.6 kJ mol\u20131), is fully consistent with the experimentally observed equilibrium for the reaction that gave 9.To explore the possibility of facile \u03b2-hydrogen elimination processes being the origin of the reversibility of the reactions that gave ring see and ESI\u2020via \u03b2-hydrogen elimination processes, comes from the reactions of 3 with 1,5-cyclooctadiene and 2-methyl-2-butene scale\" fill=\"currentColor\" stroke=\"none\">CR2 (R = Me or Ph). These observations presumably result from the considerable steric bulk of the monomeric hydridogermylene, 3.Further evidence that the reversibility of the cyclic alkene hydrogermylation reactions proceed 2-butene . In both16 proceeds via the expected hydrogermylation product, 18, as an intermediate. This then undergoes a \u03b2-hydrogen elimination to give 3 and 1,4-cyclooctadiene . Hydrogermylation of this by 3, and another \u03b2-hydrogen elimination event, yields 3 and 1,3-cyclooctadiene , the latter of which is then hydrogermylated to give the observed product, 16. Similarly, hydrogermylation of 2-methyl-2-butene affords the initially expected product, 19, which \u03b2-hydride eliminates to give 3 and 3-methyl-1-butene. Hydrogermylation of this olefin then leads to the observed product, 17. The facility of these reactions highlights the potential that 3, and related reagents, have for the selective stoichiometric isomerisation of alkenes. While such isomerisations are common for transition metal systems,It is possible that the formation of 16 and 17 were crystallographically characterised, and their molecular structures are depicted in 5\u201310, reported here. In the case of 16, the presence and location of the residual double bond of its cyclooctenyl moiety is confirmed by the shortness of the C(51)\u2013C(52) linkage (1.372(6) \u00c5).Both (iii)2 and hydridic reagents 3SiH and DIBAL) to 5\u201313 was explored, but in no case was a reaction observed under ambient conditions. Attention then turned to the reaction of stoichiometric amounts of protic reagents with 5, 8 and 11. In the case of the germylenes, the oxidative addition of HCl, NH3 or EtOH to the Ge centres of 5 or 8 occurred, to give a few crystals of 20 , and good isolated yields of 21 and 22, respectively (21 and 22 are resistant to reductive elimination (RE) of ethane or cyclopentane, even when heated to 50 \u00b0C for one hour. It is noteworthy that the reactions that gave 20\u201322 are comparable to related oxidative additions of HF,3Preliminary further reactivity studies were carried out on examples of the amido/alkyl germylene and stannylene complexes prepared here, with a view to utilising these compounds in catalytic synthetic protocols. Initially, the oxidative addition (OA) of Hectively . Solutio11 with protic reagents. These were not clean, and typically generated product mixtures that contained significant amounts of the secondary amine, L\u2020H. The two exceptions here were the reactions with stoichiometric amounts of the bulkier reagents TEMPOH and ButOH. These afforded moderate to good isolated yields of the piperidinyl N-oxide product, 23, and the known tin tert-butoxide, 24,1H NMR spectroscopy, the generation of significant amounts of ethane was observed. It cannot be sure if these reactions proceed via initial oxidative additions of the O\u2013H bond of the reagents to the SnII center of 11, prior to reductive elimination of ethane, but given the formation of the stable germanium(iv) ethoxide, 22, this is certainly a possibility (cf. related \u201cOA/RE\u201d reactions of H2 and NH3 with Ar\u20322Sn: (Different outcomes resulted from the reactions of the stannylene Ar\u20322Sn: ).2Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO),2Sn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO), toluene solutions of the germylene, 9, and stannylene, 12, were reacted with excess O2. Instead of yielding monomeric products, the dimeric oxo-bridged species, 25 and 26, were obtained in moderate isolated yields 2}2Sn(OTEMP)2],25 and 26 was confirmed by X-ray crystallographic studies (see 26), which also showed their oxide ligands to essentially symmetrically bridge two distorted tetrahedral metal centres.No spectroscopic data could be obtained for the HCl oxidative addition product, via \u03b2-hydride elimination from the cycloalkyl ligand, regenerating the cycloalkene and hydrido-tetrylene starting materials. Further evidence for this proposal comes from the reactions of a hydrido-germylene with 1,5-cyclooctadiene and 2-methyl-2-butene, both of which seemingly proceed via intermediate \u03b2-hydride elimination processes, and the clean isomerisation of the alkene involved, prior to its ultimate hydrogermylation. In addition, the element-hydrogen bonds of several protic compounds have been shown to oxidatively add to the germanium(ii) centre of two of the amido/alkyl germylenes prepared in this study, while similar reactions with an equivalent stannylene proceed via alkane elimination, and generation of tin(ii) products. Oxidations of two amido/alkyl tetrylenes with O2 have been shown to give four-coordinate, oxo-bridged metal(iv) dimers. We continue to explore the stabilisation and synthetic utility of low oxidation state group 14 element compounds.In summary, reactions of solution stable two-coordinate hydrido-tetrylenes with a variety of unactivated cyclic and acyclic alkenes, and one internal alkyne, lead to the unprecedentedly rapid and regioselective hydrometallation of the unsaturated substrate at ambient temperature. The products of the alkene hydrometallations represent the first structurally characterised examples of two-coordinate amido/alkyl germylenes and stannylenes. In the cases of the cycloalkene hydrometallations, the reactions were shown to be cleanly reversible under ambient conditions. The results of computational and experimental van't Hoff analyses of one such reaction, strongly suggest that its reversal proceeds Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "PIP\u2013TPE\u2019s fluorescence turns on blue due to the large viscosity of lysosomes which restricts intramolecular motions but it red-shifts in the bulk. Lysosomes are involved in a multitude of cellular processes and their dysfunction is associated with various diseases. They are the most acidic organelles with the highest viscosity (47\u2013190 cP at 25 \u00b0C) in the cell. Because of their acidity, pH dependent non-AIE active fluorescent lysosomal probes have been developed that rely on protonation inhibited photoinduced electron transfer (PET). In this work, an acidic pH independent lysosome targetable piperazine\u2013TPE (PIP\u2013TPE) AIEgen has been designed with unique photophysical properties making it a suitable probe for quantifying viscosity. In a non-aggregated state PIP\u2013TPE shows deep-blue emission as opposed to its yellowish-green emission in the bulk. It possesses high specificity for lysosomes with negligible cytotoxicity and good tracing ability due to its better photostability compared to LysoTracker Red. In contrast to most known lysosome probes that rely solely on PET, restriction of intramolecular motion (RIM) due to the larger viscosity inside the lysosomes is the mechanism responsible for PIP\u2013TPE\u2019s fluorescence. PIP\u2013TPE\u2019s high selectivity is attributed to its unique molecular design that features piperazine fragments providing a perfect balance between lipophilicity and polarity. Thus, the working concentration of LysoTracker Red is usually low. Furthermore, it is not photostable due to its BODIPY-based structure, which makes it unsuitable for long-term lysosome trace tracing. Moreover, the LysoTracker probes also have small Stokes shifts (less than 20 nm) which is highly disadvantageous for bioimaging applications. On the contrary, the development of AIEgens (aggregation-induced emission luminogens) allows a higher working concentration to be used with good photostability. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC twisting in MeOH with different fractions of glycerol increase as the content of glycerol increases Fig. S4, its PL = 509 nm . Similars Fig. S5. Thus, t\u03bbem = 420 nm) is not sensitive to pHs below 7 (\u03bbem = 509 nm) and turns on when its fluorescence quantum yield is above 1.8% in the aqueous buffer solution of pH 7.13, and the quantum yield maximum value reaches 12.7% with a large extent of increased fluorescence intensity in the basic aqueous solution of pH 13.03 in vitro. Since protonated PIP\u2013TPE molecules would naturally display a lower propensity to form large aggregates in acidic media (vide supra), we assume that in lysosomes they will primarily exist in the form of individual protonated molecules and/or nano-scale aggregates with the upper size limit determined by the size of the lysosomes (100 nm to 1.2 \u03bcm).e.g., outside lysosomes vide supra). However, PIP\u2013TPE\u2019s fluorescence does turn on in lysosomes due to its large viscosity.e.g. PET).It is difficult to precisely replicate intralysosomal conditions -2,5-diphenyltetrazolium bromide) assay. The result Fig. S9 shows thThe commercial lysosome probe LysoTracker Red cannot be used to trace the migration of lysosomes due to its serious photobleaching after a second time of excitation.In an attempt to gain more insight and explore possible fluorescence mechanisms operative in PIP\u2013TPE in lysosomes and in the bulk, DFT/TD-DFT calculations were performed using the B3LYP functional47Ka values of the structurally very similar dimethylpiperazine (pKa = 8.3) and diethylamine (pKa = 6.6) in water reported elsewhere,+ would be the actual predominant photoactive species that is observed in lysosomes. We thus decided to use it in our computational studies, and will henceforth refer to it in short as PIP\u2013TPEH+(soln). On the other hand, for the calculations of PIP\u2013TPE in the bulk, we took crystal clusters to consist exclusively of neutral PIP\u2013TPE molecules, and assumed a neutral PIP\u2013TPE molecule imbedded in such a cluster to be the photoactive species. We will thus use PIP\u2013TPE(bulk) to refer to the QM PIP\u2013TPE molecule in such a cluster in all further discussions of our computational results.Given the lysosomes\u2019 acidic milieu, in lysosomes PIP\u2013TPE will exist for the most part in its protonated form. Based on the p+(soln) in the ground state and then geometry optimization of PIP\u2013TPEH+(soln) in the first excited state, and studied any major changes in certain relevant metric parameters of these molecules yields a structure that displays no pronounced changes in the metrics in comparison to the original PIP\u2013TPE (see \u03c4 (C9\u2013C10\u2013N1\u2013C19)). However, expectedly marked changes in bond lengths, angles and dihedral angles of the TPE-fragment and protonated piperazine moiety in PIP\u2013TPEH+(soln) upon photoexcitation are predicted (\u03c4 (C2\u2013C3\u2013C6\u2013C7) from 23.44\u00b0 in the ground state to 82.41\u00b0 in the first excited state is anticipated, indicating that in the excited state the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond of the TPE-fragment is significantly more twisted. Furthermore, in the excited state this C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond is also significantly elongated and loses its \u201cdouble bond\u201d character upon excitation. Based on these predictions, one might speculate that this twisting around the C3 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC6 double bond in the excited state of PIP\u2013TPEH+(soln) as well as the rotation of the phenyl groups and piperazine moieties are all possible relaxation channels that are responsible for the radiationless decay in non-viscous media but get blocked in the more viscous lysosomal environment causing the fluorescence to turn on (i.e. to be visible to the naked eye).49The optimized ground state geometry of PIP\u2013TPE obtained at the DFT level of theory reproduces its single crystal X-ray structure well. Ground state geometry optimization of PIP\u2013TPEH\u2013TPE see except fredicted . Distincredicted as well redicted . Also, a1) of PIP\u2013TPEH+(soln) show that it is dominated by a single excitation from the HOMO to the LUMO in this molecule. Both the HOMO and the LUMO in PIP\u2013TPEH+(soln) are located mainly on the carbon atoms of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond contributing the most with an additional less substantial contribution from the four phenyl rings of the TPE-moiety (see +(soln) are an integral part of the HOMO but not the LUMO. We further note that the same holds true for the HOMO and LUMO distributions of PIP\u2013TPE and PIP\u2013TPE(bulk) is caused by a twisted intramolecular charge transfer (TICT) process.(bulk), an assumption that is substantiated by the results of the calculations showing that the optimized ground state (S0) and first excited state (S1) geometries of PIP\u2013TPE(bulk) both have a dihedral angle \u03c4 (C2\u2013C3\u2013C6\u2013C7) similar to the one calculated for PIP\u2013TPE (0) and first excited state (S1) geometries of PIP\u2013TPE(bulk) reveals only negligible differences in the metrics of these structures observed for PIP\u2013TPEH+(soln) in polar milieu can be attributed to the higher twisting degree of the molecule in the excited state that would automatically result in less efficient conjugation, while the red-shifted yellowish-green emission of PIP\u2013TPE(bulk) could be attributed to the higher degree of conjugation preserved in the excited state of the molecule upon excitation.(bulk) result in a \u03bbPL,max = 471 nm that is in good agreement with experiment and appears to confirm the proposed model.The results of the TD-DFT calculations for the first excited state , Dulbecco\u2019s modified Eagle\u2019s medium (DMEM), phosphate buffered saline (PBS), fetal bovine serum (FBS), penicillin and streptomycin, LysoTracker\u00ae Red DND-99, and -2,5-diphenyltetrazolium bromide) were purchased from Invitrogen. Buffer solutions (pH = 1\u201313) were purchased from Fisher Scientific. Chloroquine was purchased from Bide Pharmatech Ltd. Milli-Q water was supplied by Milli-Q Plus System .1H and 13C NMR spectra were measured on a Bruker ARX 400 NMR spectrometer using CDCl3 as the solvent and tetramethylsilane (TMS: \u03b4 = 0 ppm) as an internal standard. High-resolution mass spectra (HRMS) were recorded on a Finnigan MAT TSQ 7000 Mass Spectrometer System operating in MALDI-TOF mode. Suitable single crystals of PIP\u2013TPE were selected under oil under ambient conditions. Single crystal X-ray diffraction intensity data were collected in a stream of cold nitrogen at 100 K on a SuperNova, Dual, Mo at zero, Atlas diffractometer. Using Olex2,The et al.tert-butylphosphonium tetrafluoroborate (P(tBu)3HBF4), 3.600 g (11.00 mmol) cesium carbonate (Cs2CO3), and 20 mL dry and degassed toluene were added and stirred for 1 h at r.t. under nitrogen. Then 0.097 g (0.43 mmol) Pd(OAc)2 was added. The reaction mixture was stirred for another 0.5 h under N2. Upon the formation of an orange suspension, 1.000 g (2.04 mmol) 1,1\u2032-bis(4-bromo)-benzene and 0.5 mL (4.51 mmol) of 1-methylpiperazine were added, and a yellowish green suspension formed immediately. The reaction mixture was allowed to reflux under N2 for 2 days. After the reaction was cooled down to r.t., the toluene was removed; 50 mL EtOH and 10 mL acetone were added to dissolve the crude product. The suspension was filtered, concentrated under reduced pressure and purified via silica gel flash chromatography (chloroform/MeOH = 40\u2009:\u20091). 0.162 g of yellow powder of PIP\u2013TPE was obtained. Yield: 15%. Pale yellow block crystals were grown from acetone/hexane via solvent diffusion. 1H NMR , \u03b4H : 7.12\u20136.99 , 6.94\u20136.87 , 6.67\u20136.59 , 3.25\u20133.04 , 2.59\u20132.42 , 2.32 . 13C NMR , \u03b4C : 149.27, 144.72, 140.51, 138.28, 135.08, 132.40, 131.46, 127.63, 125.83, 114.58, 55.15, 48.60, 46.22, 11.20. MALDI-TOF-MS: m/z calcd for [C36H40N4]: 528.33; found 528.3274.The starting material 1,1\u2032-bis(4-bromo)-benzene was synthesized according to the procedure published by Li 1H NMR , \u03b4H : 12.99 , 7.15\u20137.05 , 7.04\u20136.96 , 6.96\u20136.82 , 6.81\u20136.53 , 3.91\u20133.28 , 3.26\u20132.97 , 2.86 . MALDI-TOF-MS: m/z calcd for [C36H40N4H+]: 529.33; found 529.3319.In a 4 mL screw top vial, PIP\u2013TPE was dissolved in dichloromethane (2 mL) to form a yellow solution. Hydrochloric acid was added and a white suspension formed immediately. After stirring for a few seconds, the suspension dissolved and the color of the solution changed to pale yellow. The vial was capped and the reaction mixture was stirred overnight. The next day, the layer of dichloromethane solution was pipetted out and the remaining aqueous layer was extracted with dichloromethane (10 times with 2 mL). Then, all dichloromethane layers were combined and after rotoevaporation, a pale yellow powder of the protonated PIP\u2013TPE was obtained (10.0 mg). Yield: 89%. ca. 1 mL of each sample. The viscosity was measured as a function of shear rate in the range from 100.0 to 0.01 s\u20131. In The viscosities of the aqueous buffer\u2013glycerol mixtures were measured using a TA ARES-G2 rotational rheometer at a temperature of 25 \u00b1 0.5 \u00b0C. Each measurement used \u20131 streptomycin, in a humidity incubator with 5% CO2 at 37 \u00b0C. Before experiment, the cells were pre-cultured until confluence was reached.HeLa cells were cultured in MEM and DMEM, respectively. All the cells were cultured in media supplemented with 10% heat-inactivated FBS, 100 units per mL penicillin and 100 \u03bcg mLAll the cells were grown overnight on a 35 mm Petri dish with a cover slip or a plasma-treated 25 mm round cover slip mounted to the bottom of a 35 mm Petri dish with an observation window. The live cells were incubated with 1 \u03bcM PIP\u2013TPE (2 \u03bcL of a 1 mM stock solution of PIP\u2013TPE in DMSO was diluted to 2 mL culture medium) for 15 min, and then were imaged under fluorescence microscopy. For co-staining experiments, the cells were co-stained with PIP\u2013TPE (1 \u03bcM) and a commercial biomarker (LysoTracker Red DND-99) for 15 min. The cells were then imaged using a laser-scanning confocal microscope (LSM7 DUO) using a 405 nm and 561 nm laser as the excitation light. The spectral collection region was 425\u2013545 nm and 575\u2013625 nm, respectively.\u20131 in phosphate buffer solution) was added into each well. After incubation for 4 h at 37 \u00b0C, the remaining medium in each well was totally removed and then replaced by 50 \u03bcM DMSO. With mixing for 15 min, the absorbance of each well at 595 nm was recorded by the plate reader (Thermo Scientific\u2122 Varioskan\u2122 LUX multimode microplate reader). Each experiment was performed at least 6 times as parallel tests.The HeLa cells were seeded in 96-well plates at a density of 5000 cells per well. After overnight culture, the medium in each well was replaced by fresh medium containing different concentrations (0.1/0.2/0.5/1/2/5 \u03bcM) of PIP\u2013TPE. After 24 h of treatment, 10 \u03bcL MTT solution scale\" fill=\"currentColor\" stroke=\"none\">C twisting of its protonated species in the excited state upon excitation. Based on the aforementioned facts, this molecular design can be used as a guide to develop new promising lysosomal pH stable fluorescent AIE probes, which would allow monitoring of some important fundamental microenvironmental parameters with no or little influence from pH.In conclusion, we have developed an acidic pH independent lysosome targetable AIEgen, PIP\u2013TPE, which displays fluorescence emission of different colors depending on its aggregation state: deep-blue for non-aggregates and yellowish-green for the bulk solid. Experiments suggest that protonation of PIP\u2013TPE has no significant influence on its photophysical properties but does affect its scale of aggregation. PIP\u2013TPE has proved to have high specificity to lysosomes with a good signal-to-noise ratio and negligible cytotoxicity. PIP\u2013TPE\u2019s good selectivity towards lysosomes can be attributed to the piperazine functional groups and higher viscosity of the intralysosomal milieu and renders it a good lysosomal tracing agent with better photostability than the commercial alternatives such as LysoTracker Red. PIP\u2013TPE\u2019s turn-on fluorescence in lysosomes can be attributed to the viscosity restricting intramolecular motion (RIM). PIP\u2013TPE\u2019s blue emission in lysosomes can be attributed to the high degree of CThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "C\u2013H activation of methane followed by dehydrocoupling at room temperature led ultimately to the formation of the olefin H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu via the addition of redox-active ligands (L) such as thioxanthone or 2,2\u2032-bipyridine (bipy) to (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH3) (1). 2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu via the addition of redox-active ligands (L) such as thioxanthone or 2,2\u2032-bipyridine (bipy) to (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH3) (1). Using both of these exogenous ligand systems, we could trap the titanium fragment via an insertion reaction with these two substrates to afford species of the type (PNP)Ti(L)(LH). A combination of computational and isotopic labeling studies reveals that the L ligand promotes the C\u2013C bond forming step by migration of the methyl moiety in 1 to the \u03b1-alkylidene carbon by producing a Ti(iii) species (PNP)Ti{CH(CH3)tBu}(L). In the case of L = thioxanthone, \u03b2-hydrogen abstraction gives an olefin, whereas with 2,2\u2032-bipyridine \u03b2-hydride elimination and migratory insertion lead to (PNP)Ti(L)(LH). These redox-active ligands play two important roles: (i) they accept an electron from the Ti-alkylidene fragment to allow the methyl to approach the alkylidene and (ii) they serve as traps of a hydrogen atom resulting from olefin elimination. These systems represent the first homogeneous models that can activate methane and selectively dehydrocouple it with a carbene to produce an olefin at room temperature.C\u2013H activation of methane followed by dehydrocoupling at room temperature led ultimately to the formation of the olefin H PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds at the expense of breaking the stronger C\u2013H bonds of methane or another alkane. Surface supported organometallic reagents and heterogeneous catalysts with a sulfur-based hydrogen acceptor were reported previously, but they require high temperatures with concurrent release of toxic H2S.2Sc(CH3)3)(\u03b73-CH2CHCMe2).2Sc(CH3) at room temperature.4 + H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHCH3 \u2192 H3CCH(CH3)2. More recently, Legzdins and co-workers found that addition of CO under high pressure to Cp*W(NO)(CH3)(\u03b73-CH2CHCMe2), a species derived from methane activation, could result in insertion into the methyl ligand ultimately leading to extrusion of a mixture of \u03b2,\u03b3-unsaturated ketones.9The non-oxidative conversion of methane to an olefin is fundamentally an endergonic process, and hence only a handful examples exist, where this remarkable reaction was seen. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH2tBu) can eliminate H3CtBu to form transient (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCtBu (A), which then activates CH4via 1,2-CH bond addition to form the neopentylidene\u2013methyl (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH3) (1) .1 can also extrude CH4 to reform A, this process was found to be much slower with an associated \u0394G\u2021 of 28.1 kcal mol\u20131 .1 tautomerizes to the methylidene (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2(CH2tBu) (B), but does so also very slowly with a \u0394G\u2021 > 28.1 kcal mol\u20131 .4 can take place competitively. More evidence for B being the more reactive tautomeric form, was derived from an independent synthesis involving \u201cCH2\u201d group transfer from a phosphorus ylide to the titanium olefin complexes of the type (PNP)Ti(CH2tBu)(\u03b72-olefin).2\u201d, B is not observed, but instead tautomerizes quickly to 1 corroborating our claim that B lies 7.8 kcal mol\u20131 higher in energy to 1 .We previously reported how complex (PNP)TiCH3) (1) .10,11 ThB since it contains the dehydrocoupled form of methane and may allow for accessing olefins via reductive coupling.iv) center without promoting \u03b1-hydrogen abstraction to form A by losing CH4. Unfortunately, complexes 1 and intermediates A and B pose some challenges since they contain reactive and nucleophilic alkylidyne and alkylidene moieties that may engage in Wittig-like chemistry.1, albeit slowly to carry out the expected Wittig-like chemistry and produce tBuHC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC13H8O as shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO(CH3)] could not be detected and instead, a mixture of metal-based products was observed by 31P NMR spectroscopy. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO(CH3) was not unexpected since the close analogue, (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO(CH2tBu), is known to decompose rather quickly in solution. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC12H8S) is used instead, we observed some Wittig-like reactivity along with an additional olefin, which was identified to be H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu on the basis of 1H NMR spectroscopy and GC-MS scale\" fill=\"currentColor\" stroke=\"none\">CHtBu was unambiguously confirmed when compared to an independently prepared sample. Since the reaction mixture contained some unreacted 1, performing the same transformation using a 2 equiv. of thioxanthone produced higher yields of tBuHC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC13H8S and H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu in approximately 1\u2009:\u20099 based on the 1H NMR spectrum. Under these conditions, we were also able to isolate the titanium complex (PNP)Ti scale\" fill=\"currentColor\" stroke=\"none\">CC12H8S)(OCHC12H8S) (2) in 52% yield and carbon Ti\u2013OCH at 83.8 (13C NMR) ppm. The most notable features in the solid-state structure of 2 are the presence of a \u03b72- bound thioxanthone in addition to a coordinated thioxanthoxide resulting from a hydrogen adding to the ketone carbon of the formal thioxanthone scale\" fill=\"currentColor\" stroke=\"none\">CHtBu indicated that both methyl and neopentylidene ligands have undergone dehydrocoupling in 1. To circumvent the Wittig-like reaction observed between 1 and thioxanthone, we resorted to a ligand that lacked the ketone unit but which could be resistant to alkyl and alkylidene units. Treatment of 1 with two equiv. of 2,2\u2032-bipyridine (bipy) in benzene over 24 hours resulted in the formation of H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu along with the titanium complex (PNP)Ti(bipy)(bipyH) (3), that was isolated in 33% yield , which we propose contributes to the violet color.3 having a Ti(iii) radical antiferromagnetically coupled to a bipy\u02d9\u2013.Complex xanthone , left. T3% yield . Akin toly bipyH , right. 2 and 3, as well as propose the most likely pathway to C\u2013C bond formation, we conducted isotopic labelling studies using the 13C and 2H isotopomers (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(13CH3) (1-13C) and (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CD3) (1-D3), respectively, with 2 equiv. of bipy and thioxanthone.1-13C irrefutably revealed the formation of H213C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu and 3 scale\" fill=\"currentColor\" stroke=\"none\">CHtBu (3-D1) based on a combination of 1H, 13C, and 2H NMR spectra.2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu and that methyl migration to the neopentylidene most likely occurs by Path 1, as opposed to the less plausible Path 2 scenario involving tautomerization to B followed by neopentyl migration ; 1H NMR spectrum when 1-13C is used in the presence of bipy and thioxanthone (b); 1H NMR spectrum when 1-D3 is used in the presence of bipy and thioxanthone (c); and 2H NMR spectrum when 1-D3 is used in the presence of bipy and thioxanthone (d).To establish the origin of the inserted hydrogen in both Bu and 3 whereas >CHtBu and to afford the intermediates B1 and T1 at 18.7 and 5.3 kcal mol\u20131, respectively. These six-coordinate complexes containing a methylidene-alkyl or a methyl-alkylidene moieties may then undergo the reductive C\u2013C coupling reaction traversing the triplet transition states 3B1-TS and 3T1-TS associated with reaction barriers of 30.8 and 14.1 kcal mol\u20131, respectively. These calculations suggest that the reductive C\u2013C coupling is most easily initiated from complex 1, rather than its tautomer B consistent with the isotopic labeling studies (vide supra).To better understand the mechanism, quantum chemical calculations based on density functional theory (DFT) were carried out. The free energy profiles for the two possible pathways of reductive migration of the methyl moiety are illustrated in A at room temperature was investigated previously1. As shown in T1, which undergoes irreversible reductive methyl migration to form 3T2. Interestingly, we found that the reduction of the metal is accompanied by a singlet to triplet spin-crossover, as the newly formed Ti(ii)-d2 center adopts a high-spin triplet configuration. In good agreement with experimental results, the barrier of this key step associated with 3T1-TS is only 14.1 kcal mol\u20131, suggesting that the methyl migration will be much faster than \u03b1-hydrogen abstraction to produce CH4 and A, which typically requires much higher activation energies in excess of \u223c30 kcal mol\u20131. Such a low barrier for a C\u2013C forming reaction is rareThe activation of methane by T1, the T-ligand is weakly bound with a Ti\u2013O distance of 2.61 \u00c5 and is arranged in trans disposition to the alkylidene fragment. As the reductive C\u2013C coupling traverses through the transition state 3T1-TS, significant structural and electronic rearrangements take place. First and foremost, the T-ligand binds much more tightly displaying a Ti\u2013O distance of 1.90 \u00c5, whereas the double-bond between Ti and the alkylidene-carbon is notably lengthened from 1.85 to 1.99 \u00c5. The T-ligand exerts a strong trans-effect by removing electron-density from the Ti-alkylidene bond into a stronger Ti\u2013O \u03c3-bond and allowing for an easier activation of the Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond.3 bond is formally cleaved to transiently give a methyl-anion, which may attack the Ti-alkylidene double-bond. As shown in 1T1-TS. The two main orbital interactions are drawn as MO-A, the in-phase combination of the methyl lone-pair orbital with the \u03c0-orbital of the Ti-alkylidene moiety, and as MO-A*, the corresponding antibonding combination. Both orbitals are of course occupied, since these are interactions of two filled fragment orbitals. We were unable to locate this putative transition state, because the \u03c0*-orbital of the thioxanthone ligand T\u2013\u03c0* is the lowest unoccupied molecular orbital (LUMO) of the T1 complex and will also be low enough in energy in the putative 1T1-TS which will be lower than MO-A*. Consequently, calculations naturally converge to a state where an intramolecular electron-transfer from the highly unfavorable MO-A* orbital to the low-lying T\u2013\u03c0* orbital will afford a much more favorable electronic structure. As the T\u2013\u03c0* orbital places the electron far away from the metal center, the metal-containing frontier orbitals will move to lower energies, giving the final orbital energy ordering found in 3T1-TS. What was labeled as MO-A is found in 3T1-TS as HOMO\u20133 at \u20136.62 eV and the corresponding antibonding combination, conceptually labeled MO-A*, is found as SOMO1 at \u20134.29 eV (The electronic distortion accompanying the spin-crossover is illustrated in \u20134.29 eV . Interesiii)-complex formally. In order to test the mechanistic role of the thioxanthone ligand identified in our calculations, we carried out a series of experiments. First, phosphine (PMe3) and pyridine ligands were used as exogenous ligands with the expectation that they will be unable to function in a similar manner as an electron acceptor if the computational results are correct. And, indeed, when complex 1 is treated with either ligand only gave activation of solvent is observed via \u03b1-hydrogen abstraction to form CH4 and alkylidyne A.\u20131 and 35.0 kcal mol\u20131, respectively, emphasizing the magnitude of the impact that the electronic reorganization has on the transition state energy. Details are given in the ESI.This conceptual MO-analysis is helpful, because it provides a compelling and simple explanation for why the computed barrier for the reductive C\u2013C coupling is so low. The thioxanthone ligand acts as a temporary electron storage unit where one of the electrons can be placed during the C\u2013C coupling reaction. Once the insertion completes and the C\u2013C bond is formed, the SOMO1 becomes a classical Ti-centered frontier orbital to afford the one-electron reduced Ti(L)M scale\" fill=\"currentColor\" stroke=\"none\">CH2)(CH3)]+ can engage in methyl migration to form a C\u2013C bond and proposed that a subsequent \u03b2-hydride elimination may generate H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 and [M\u2013H].3T2 and found the transition state 3T2-TS to have a barrier of 29.3 kcal mol\u20131. In search of an alternative, lower energy transition state, we considered the singlet spin state analogue T3, which was found 1.2 kcal mol\u20131 lower in energy. And, indeed, we were able to locate the transition state T3-TS that gives a barrier of 25.0 kcal mol\u20131 for the dehydrogenation of the methyl group on the singlet potential energy surface. Interestingly, this transition state does not lead to the anticipated \u03b2-hydride elimination to give a metal-hydride. Instead, the hydride is transferred concertedly to the carbonyl-carbon of the thioxanthone functionality, as illustrated in T4 is formed. Our calculations suggest that this step is most difficult energetically with a barrier of 25 kcal mol\u20131, which is in good agreement with the experimental observation that this reaction does occur at room temperature. The final steps of the reaction involve product release and addition of another equivalent of the thioxanthone substrate, where either the singlet or triplet spin configurations are adopted to lower the total energy.As illustrated in d that , which is expected to quickly decompose in solution. Mechanistically, the Wittig reaction will likely invoke a [2 + 2] cycloaddition between the alkylidene and the ketone, which may subsequently undergo bond metathesis, as illustrated in \u20131, as the transition state 3T1-TS is lower in energy than W2-TS. Curiously, the calculated energy ordering of the two analogous transition states are reversed when X is used and the Wittig-like reaction pathway is predicted to be favored by \u223c2 kcal mol\u20131, as shown in As mentioned above, the Ti-alkylidene intermediate T1 \u2192 3T1-TS and X1 \u2192 3X1-TS. With T, this transformation is 6.9 kcal mol\u20131 uphill, whereas 9.4 kcal mol\u20131 is found for X. The presence of the sulfur atom in T makes the C\u2013C coupling transition state 2.5 kcal mol\u20131 lower electronically when compared to that of xanthone. This energy difference can be broken down into chemically meaningful components, as shown in T1 and X1, we calculated the \u201csnap dissociation energy\u201d where the (thio)xanthone and the titanaalkylidene fragments are dissociated without each of the fragments being allowed to change their structure, which were 18.3 and 19.7 kcal mol\u20131, respectively. Next, we evaluated the energy required to change the geometry of the Ti-alkylidene fragment to that found in the transition state and they were 46.5 and 46.6 kcal mol\u20131, respectively, marked as [Ti] \u2192 [Ti]* in \u20131, respectively. Lastly, the structural distortion of the T or X ligands was found to by uphill by 8.9 and 8.0 kcal mol\u20131, respectively. Taken together, these energy components add to afford 177.2 and 176.5 kcal mol\u20131, respectively, and represent the energy that must be invested to take the intermediates T1 and X1 to the C\u2013C coupling transition states. It is interesting that all the slight differences cancel and the energetic costs are essentially identical with the numerical difference being only 0.6 kcal mol\u20131.In order to better understand the origin of the computed energy differences, we first examined the different components of the solution phase free energies and found that the entropy and solvation energy components do not give any meaningful difference. Next, we analyzed the electronic energy differences by deconstructing the total energies into chemically meaningful energy components, as illustrated in \u20131 for thioxanthone and xanthone, respectively. The interaction energy between the two molecular fragments are computed to be \u2013148.1 and \u2013147.4 kcal mol\u20131, respectively. Obviously, the most important difference in energy stems from the reduction of the T and X substrates, which act as redox-active ligands and temporarily accommodate one electron, as explained above. In ii)-center becomes formally a Ti(iii)-center with one electron moved to the ligand-based SOMO. Comparing T to X, it is easy to understand the energetic difference discussed above. The contribution of the 3px orbital of sulfur is 6.0%, whereas 2px of oxygen contributes only 3.1%. This result of course reflects on the fact that sulfur is much more polarizable than oxygen and, thus, better in accommodating the excess charge than oxygen would. And whereas this difference is small, it is responsible for lowering the transition state by \u223c2.6 kcal mol\u20131 when T is employed compared to when X is used. This energy difference is enough to invert the energetic ordering of the transition states of the olefination and Wittig-like reaction, as illustrated in As represented in \u2013, but participates actively in the C\u2013C coupling by acting as a reservoir of the excess electron density at the transition state. The structurally related X substrate is incapable of promoting the C\u2013C coupling, because the lack of the sulfur heteroatom reduces its ability to accommodate the excess electron thus resulting in a higher transition state of \u223c2.6 kcal mol\u20131. The carbonyl functionality present in the substrate gives rise to a competing reaction channel, where a [2 + 2] cycloaddition may afford a Wittig-like product. Our calculations show that the barriers of this reaction are very similar to those of the C\u2013C coupling reactions, especially in the case of T. Such an additional redox stabilization of the T ligand can push the reaction to be more selective for C\u2013C coupling, whereas in X only the [2 + 2] cycloaddition product is observed.In conclusion, our computational studies highlight how spin-crossover at the metal site and the redox-activity of the substrate work in concert to couple a methyl group to an metalla-alkylidene with a very low barrier. This process leads ultimately to the olefination of methane, and requires the removal of two electrons and two protons overall. We found that T is capable of acting not only as the sacrificial oxidant that becomes reduced during the process to form TH1 to form Y1, where one phosphine arm of PNP ligand must dissociate to accommodate the chelating nature of the bipy ligand. In the C\u2013C coupling transition state 3Y2-TS the bipy functionality acts as an electron-reservoir and becomes formally reduced, confirming our expectation that bipy is a competent redox-active ligand. Unlike what was observed previously, the C\u2013H activation is accomplished via a classical \u03b2-hydride elimination mechanism when the transition state 3Y2-TS is traversed with a calculated barrier of 26.8 kcal mol\u20131, which produces the olefin product H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu. This barrier is slightly higher than the \u223c25 kcal mol\u20131 observed for T and is in good agreement with the observation that with bipy, the reaction is slower. Once 3Y3 is formed, it may bind another equivalent of bipy to afford 3Y4. Finally, the hydride migrates to the newly added bipy functionality traversing the transition state 3Y4-TS, and a spin-crossover to the singlet surface affords the diamagnetic final product complex Y6. Thus, the bipy substrate behaves as expected based on the general mechanistic understanding and is capable of promoting the methane olefination reaction, albeit with a slightly higher barrier and with minimally different mechanistic features that were easy to be anticipated.Given the detailed insights about the mechanism summarized above for T and X, bipy substrate offers several interesting features that will enhance our understanding of the mechanism. First, the lack of the carbonyl functionality prevents Wittig-like chemistry. Second, the bipy ligand is widely known to be redox active and we anticipate the that it too may act as an electron reservoir just like thioxanthone and, third, we expect that the lack of flexibility in structure and binding geometry will limit the possible spin-crossover scenarios. Thus, we examined the mechanism of methane olefination using bipy in detail and the computed reaction energy profile is shown in 4 can be activated by (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH2tBu) via transient titanium alkylidyne intermediate at room temperature to generate (PNP)Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu(CH3) and how methyl migration can be promoted with exogenous redox-active ligands to ultimately yield the dehydrocoupled product H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu. In addition, whereas thioxanthone resulted in the formation of H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu via reductive C\u2013C coupling, the xanthone ligand only produced the olefin from a Wittig-like reaction. By combining computational and experimental methods of mechanistic inquiry, we revealed a complete pathway that unifies experimental observations and computational results. We found that the critical role of thioxanthone and bipyridine is to become redox active during the course of the reaction and accommodate an electron to enable reductive methyl migration to form a C\u2013C bond and ultimately H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu. The methane olefination is therefore facilitated by the redox-active ligand which acts as an electron reservoir to avoid a filled\u2013filled interaction between the two Lewis basic fragments in the putative singlet transition state. As the C\u2013C coupling takes place, one electron from the Ti-alkylidene \u03c0-orbital is removed and placed in the \u03c0*-orbital of the redox-active ligand. Experimentally observed chemoselectivity between thioxanthone and xanthone was also scrutinized and explained using fragment analysis. The resulting C\u2013C coupled product then forms the olefin H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHtBu by hydride elimination. In the case of thioxanthone, \u03b2-hydrogen abstraction promotes olefin formation whereas for bipy, the more classical \u03b2-hydride elimination ensues. Several spin-crossover events are proposed along the reaction trajectory that helps to lower the energies of intermediates and transition states. Our strategy therefore provides a mild route to make C\u2013C bonds with methane using an electropositive base metal that generally do not engage in two-electron redox processes.We have shown how CHThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Theory meets experiment for the simplest model of alcohol\u2013alkene hydrogen bonding and both support a close to harmonic description. \u20131), the small change in diagonal anharmonicity (\u20133 cm\u20131) and the overtone intensity attenuation (2 \u00d7 102-fold) together with theoretical predictions for the preferred structural arrangement and the zero-point-corrected dissociation energy (8 kJ mol\u20131) may thus be regarded as definitive reference values for related systems and for more approximate computational methods. In particular, MP2 calculations are shown to fail for this kind of weak intermolecular interaction.An FTIR spectroscopic study of the elusive hydrogen-bonded methanol\u2013ethene complex, the most elementary example for weak intermolecular alcohol hydrogen bonding to a \u03c0 cloud, is presented. By isolating the complex in a supersonic jet, the rigorous comparability to high-level quantum chemical calculations is ensured. In stark contrast to classical hydrogen bonds, experimental overtone analysis reveals the harmonic oscillator approximation for the OH red shift to be accurate. Harmonic calculations up to explicitly correlated local coupled-cluster level are thus found to agree very well with experiment. The experimental OH values for the red shift (45 cm This holds not only for strong hydrogen bonds to heteroatoms, but also for weak OH\u00b7\u00b7\u00b7\u03c0 interactions which have been associated with olfactory processes.via overtone bands\u20131 red shift in the prototypical methanol dimer into its harmonic and anharmonic contributions, and high-level quantum chemical calculations have shown that many popular theoretical methods are inadequate for a quantitative description of the harmonic component.Quantum chemical calculations are customarily used to suggest structural motifs, dissociation energies and assignments to observed spectral features. Direct comparison between theory and experiment is typically hampered by the fact that anharmonic vibrational treatments are challenging except for small systems and rather simple methods. In addition, an experimental determination of anharmonicity PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond is perpendicular to the mirror plane of the methanol molecule through which a stream of helium is directed, and by admixture of ethene in helium stored in a gas cylinder at 50 bar.The jet-FTIR experiments were carried out using the \u201cfilet\u201d jet, which has been described in detail elsewhere.2.2Quantum chemical calculations were carried out using the MOLPRO 2012.1 and GAUSGAUSSIAN09 was used for canonical MP2 and B2PLYP-D3BJ calculations cc-pVnZ,nZ\u201d. For the explicitly correlated calculations, the VDZ-F12 basis set was used.nZ/JKFITnZ/MP2FIT38Most In the current study, we refer to the LCCSD(T*)-F12a(int)/VDZ-F12 method as our benchmark level of theory, as it has been found to be essentially converged to the basis set limit in the methanol dimer33.1PS = 0.75 bar. Lower stagnation pressures down to 0.40 bar were also used to decrease the amount of larger aggregates. We identify the mixed ME dimer band at 3641 cm\u20131 .20One further analysis involves the observed intensities of the fundamental and overtone bands, with the fund\u2009:\u2009ot ratio predicted to increase with stronger hydrogen bonds . While this is qualitatively expected for a weak OH\u00b7\u00b7\u00b7\u03c0 bond, it represents an interesting case where the observable red shift can be explained to a good approximation by harmonic effects alone, given that diagonal and off-diagonal anharmonic contributions are small and mutually canceling. Together with the sensitive ethene torsion preference, the ME dimer thus provides a nice accuracy test for quantum chemical methods without the need to evaluate anharmonic effects.One important contribution to the overall experimental OH red shift in the methanol homodimer is the anharmonic cross-term that couples the stretching motion and the hindered rotation (libration) in the dimer. Since the latter motion tends to weaken the hydrogen bond, xOH,i of the donor OH stretching vibrations in MM and ME are given in Perturbational anharmonic treatments are available in the GAUSSIAN program package\u03bd\u0303OH = 3564 cm\u20131. Closer inspection reveals that this is in part due to the difficult ethene torsion which is predicted at a harmonic wavenumber of \u03c9tors \u2248 1 cm\u20131. While the corresponding stretching-ethene torsion coupling term xOH,E-tors amounts to about 0.5 and \u20130.03 cm\u20131 in the robust B2PLYP-D3BJ/VTZ and MP2/VTZ calculations, respectively, it is \u201398 cm\u20131 at this faulty level of theory. We attribute this to a BSSE effect caused by diffuse functions on the hydrogen atoms. When neglecting this error, the overall MP2/aVTZ anharmonic correction is about \u2013177 cm\u20131, in agreement with the robust calculations ,Q in the methanol monomer and the two dimers. We fit a modified Morse potential of the formC and b1 through b5 left free in the fit. We refrain from denoting the prefactor as a dissociation energy, since the resulting potential is not strictly dissociative anymore. Solutions to the vibrational Schr\u00f6dinger equation were found by numerical variational calculations with a basis set of Gaussian functions distributed along the coordinate Q, using the reduced masses from the respective normal modes. The results are displayed in \u20132 cm\u20131 with respect to changes in number, spacing and width of the basis functions. Harmonic wavenumbers at the equilibrium position provide a consistency check with the normal-mode calculations, showing deviations up to 3 cm\u20131. We attribute these to fitting errors and assume the same variations for the calculated energy levels. Among our three test cases, the most interesting system is the methanol monomer, since the torsional perturbations of the OH oscillator \u2013 which cannot be captured with a 1-D model \u2013 are smallest there. The experimental wavenumbers are reproduced well by the benchmark method; conversely, the MM wavenumbers are underestimated due to the lack of this specific coupling. Still, the results are compatible with the blue-shifting xOH,lib \u2248 60 cm\u20131 coupling suggested by the VPT2 calculations. Overall, the diagonal anharmonicities of the OH stretching oscillator from variational and VPT2 calculations show a satisfying agreement with the experiment across our methods even when the corresponding harmonic results are unreliable.Estimating anharmonicity constants with our explicitly/locally correlated benchmark method is difficult due to the lack of a comparable implementation in the MOLPRO program package. We thus calculated potential energy curves along the (donor) O\u2013H stretching normal modes De = 11.4 kJ mol\u20131. This corresponds to a variation of only 0.5 kJ mol\u20131 when compared to the double-zeta result. It shows the good convergence of the value relative to the basis set. Given that these are all coupled cluster values, the error bar for De should be around 1 kJ mol\u20131. This is a rather conservative estimate. Adding the harmonic zero-point energy corrections, we obtain a value of Dh0 = 8.2 kJ mol\u20131. In order to obtain a more reliable estimate of the spectroscopic dissociation energy, accurate anharmonic calculations for the zero-point energy would be required. However, these are extremely challenging given the large amplitude motions present in the system.As previously noted, the computed dissociation energies for the methanol\u2013ethene system can be found in 4\u03bd\u0303OH = 45 cm\u20131 from the monomer reference is reduced by about 60% from that of the homodimer. The weakness of this prototypical OH\u00b7\u00b7\u00b7\u03c0 contact is further attested by the minute change in diagonal anharmonicity of \u0394xOH,OH \u2248 \u20133 cm\u20131 and moderate 170(70)-fold intensity attenuation of the overtone with respect to the fundamental.We have recorded FTIR spectra of methanol\u2009:\u2009ethene mixtures in supersonic expansions, assigning the fundamental and overtone transitions of the mixed dimer. The observed OH stretching red shift \u2013\u0394\u03c9OH = 45 cm\u20131 which coincides with the experimental anharmonic value. Assuming the chosen method to be robust, the observed wavenumber shift is thus mostly a harmonic effect, indicating that diagonal and off-diagonal anharmonic corrections closely cancel each other. As in the methanol homodimer,\u20131, providing another measure for the weakly perturbing character of the intermolecular interaction. Likewise, the harmonic zero-point dissociation energy at our best level of theory is Dh0 = 8.2 kJ mol\u20131, 55% less than in the methanol dimer (Dh0 = 18.3 kJ mol\u20131).\u20131 for the spectroscopic dissociation energy of ME appears justified. Microwave verification of the subtle structural preference of the methanol\u2013ethene complex for a perpendicular arrangement of the C\u2013O and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axes would be welcome.High-level quantum chemical calculations with local and explicit electron correlation treatment predict a harmonic red shift of \u2013\u0394We reiterate our previous findings that the MP2 method is inadequate for harmonic wavenumber predictions in alcoholic hydrogen bonds, significantly overestimating the red shift in canonical and local correlation treatments. However, SCS-LMP2 fares well in this regard both for the weak OH\u00b7\u00b7\u00b7\u03c0 methanol\u2013ethene and stronger OH\u00b7\u00b7\u00b7O methanol\u2013methanol contacts, at the well-known45"}
+{"text": "A Ru/La0.5Ce0.5O1.75 catalyst pre-reduced at an unusually high temperature (650 \u00b0C) catalyses ammonia synthesis at a high rate under mild conditions. 0.5Ce0.5O1.75 pre-reduced at an unusually high temperature (650 \u00b0C) catalysed ammonia synthesis at extremely high rates under mild conditions; specifically, at a reaction temperature of 350 \u00b0C, the rates were 13.4, 31.3, and 44.4 mmol g\u20131 h\u20131 at 0.1, 1.0, and 3.0 MPa, respectively. Kinetic analysis revealed that this catalyst is free of hydrogen poisoning under the conditions tested. Electron energy loss spectroscopy combined with O2 absorption capacity measurements revealed that the reduced catalyst consisted of fine Ru particles (mean diameter < 2.0 nm) that were partially covered with partially reduced La0.5Ce0.5O1.75 and were dispersed on a thermostable support. Furthermore, Fourier transform infrared spectra measured after N2 addition to the catalyst revealed that N2 adsorption on Ru atoms that interacted directly with the reduced La0.5Ce0.5O1.75 weakened the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond and thus promoted its cleavage, which is the rate-determining step for ammonia synthesis. Our results indicate that high-temperature pre-reduction of this catalyst, which consists of Ru supported on a thermostable composite oxide with a cubic fluorite structure and containing reducible cerium, resulted in the formation of many sites that were highly active for N2 reduction by hydrogen.Ammonia is an important feedstock for producing fertiliser and is also a potential energy carrier. However, the process currently used for ammonia synthesis, the Haber\u2013Bosch process, consumes a huge amount of energy; therefore the development of new catalysts for synthesising ammonia at a high rate under mild conditions (low temperature and low pressure) is necessary. Here, we show that Ru/La Approximately 60% of the energy consumed by the process is recovered and stored as enthalpy in the ammonia molecule; but the remaining energy is lost, mostly during hydrogen production from natural gas, ammonia synthesis, and gas separation. The development of methods for reduction of the energy used by this process has been the goal of a considerable amount of research. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond of N2 (945 kJ mol\u20131).2, which weakens the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond and promotes its cleavage.2O.+, Ru, and MgO possesses high ammonia-synthesis activity2+, Ru, and activated carbon has been used in industrial-scale commercial processes.24Al28O64]4+(e\u2013)4 (Ru/C12A7:e\u2013) and Ru/Ca(NH2)2, also show high ammonia-synthesis activity.2)2 is higher than the activities of any previously reported Ru catalysts, as well as the activities of 3d transition metal\u2013LiH composites, which are a new class of non-Ru ammonia-synthesis catalysts.Ammonia has been synthesised under ambient conditions with organometallic catalysts, but strong reducing agents and proton sources are generally needed, and the ammonia production rate is too low for practical applications.et al. found that rare earth oxides, such as CeO2 and La2O3, are effective supports for Ru catalysts.2O3 exhibits high ammonia-synthesis activity.et al. reported that the rate of ammonia synthesis over Ru/CeO2 is high when the catalyst has been pre-reduced at 500 \u00b0C.4+ is reduced to Ce3+, and thus an electron is transferred to Ru and then to adsorbed N2 molecules. However, the ammonia synthesis rate is slower over a catalyst that has been pre-reduced at a temperature higher than 500 \u00b0C, owing to structural changes associated with sintering of the support. To increase the specific surface area of the catalysts, as well as the reducibility of the Ce4+, various investigators have used composite-oxide supports, such as CeO2\u2013La2O3,2,2,2\u2013ZrO2,2O3\u2013CeO2,et al., the pre-reduction temperature for these catalysts is kept below 500 \u00b0C to minimize aggregation of the Ru particles.26In the 1990s, Aika 0.5Ce0.5O1.75, a catalyst consisting of Ru supported on a La0.5Ce0.5O1.75 solid solution, which is a composite oxide of CeO2 and La2O3. After pre-reduction at the unusually high temperature of 650 \u00b0C, the catalyst exhibited high ammonia-synthesis activity at reaction temperatures from 300 to 400 \u00b0C; the activity was the highest among oxide supported Ru catalysts and comparable to that of the most active Ru catalysts reported to date. The thermostable oxide support, which had an average composition of La0.5Ce0.5O1.64 after pre-reduction at 650 \u00b0C, consisted of fine Ru particles strongly anchored to the reduced support and had numerous active Ru sites. The dependence of the catalyst structure and state on the reduction temperature was elucidated by means of various characterisation techniques, including energy electron loss spectroscopy (EELS) and scanning transmission electron microscopy (STEM). This catalyst has the advantages of being easy to prepare and stable in the atmosphere, which makes it easy to load into a reactor.Herein, we report the ammonia-synthesis activity of Ru/La0.5Ce0.5O1.75 was measured at 1.0 MPa after pre-reduction of the catalyst at 450, 500, 650, or 800 \u00b0C. Under the reaction conditions, the equilibrium ammonia-synthesis rate and the ammonia yield at 400 \u00b0C are 127 mmol g\u20131 h\u20131 and 7.91%, respectively. At all reaction temperatures, the ammonia-synthesis rate was markedly higher over the catalyst pre-reduced at 650 \u00b0C than over the catalysts pre-reduced at 450 \u00b0C reached 31.3 mmol g\u20131 h\u20131 and was much higher than the rates over the other tested catalysts, such as Ru/CeO2_650red (17.2 mmol g\u20131 h\u20131) and Ru/La2O3_500red (10.8 mmol g\u20131 h\u20131), whose supports each contain one of the rare earth elements in La0.5Ce0.5O1.75, and Ru/Pr2O3_500red (15.7 mmol g\u20131 h\u20131),0.5Ce0.5O1.75_650red was approximately 7.6 times that over Cs+/Ru/MgO_500red (4.1 mmol g\u20131 h\u20131), a well-known catalyst that is often used as a benchmark and that is more active than Ba2+/Ru/activated carbon0.5Ce0.5O1.75_650red was comparable to that over 10 wt% Ru/Ca(NH2)2 .24We also compared the ammonia-synthesis rates over various other supported 5 wt% Ru catalysts at 350 \u00b0C and 1.0 MPa . Each of0.5Ce0.5O1.75_650red and Cs+/Ru/MgO_500red with the use of the rates at 300, 325, 350, and 375 \u00b0C (Ea) calculated for Ru/La0.5Ce0.5O1.75_650red (64 kJ mol\u20131) was much lower than that for Cs+/Ru/MgO_500red (100 kJ mol\u20131), and was comparable to that reported for 10 wt% Ru/Ca(NH2)2 (59 kJ mol\u20131).0.5Ce0.5O1.75_650red was responsible for the high ammonia-synthesis rate.We prepared Arrhenius plots for ammonia-synthesis reactions catalysed by Ru/Lad 375 \u00b0C . To avoi+/Ru/MgO_500red.2 molecules (a phenomenon referred to as hydrogen poisoning), which is a typical drawback of conventional Ru catalysts.0.5Ce0.5O1.75_650red was 13.4 mmol g\u20131 h\u20131, which is the highest value reported for Ru catalysts to date; and the rate increased to 31.3 and 44.4 mmol g\u20131 h\u20131 when the pressure was increased to 1.0 and 3.0 MPa, respectively. Hence, we assumed that hydrogen poisoning did not occur over Ru/La0.5Ce0.5O1.75_650red at the tested temperature. To confirm this assumption, we performed kinetic analysis at 350 \u00b0C and 0.1 MPa. For that purpose, reaction orders for N2, H2, and NH3 were determined with the assumption of the rate expression (1) scale\" fill=\"currentColor\" stroke=\"none\">N bond cleavage, which is the rate-determining step for ammonia synthesis, is relatively promoted over Ru/La0.5Ce0.5O1.75_650red. Moreover, stability of Ru/La0.5Ce0.5O1.75_650red at 350 \u00b0C under 3.0 MPa was examined. When an inline gas purifier was installed for cleaning the H2/N2 mixture , and the elemental distributions and valence states of the Ce ions were evaluated by means of STEM spectrum imaging of simultaneous energy dispersive X-ray (EDX) mapping and EELS. Because the elemental states and the structure of the catalyst might be changed by exposure to air, we carried out these analyses in the absence of air using a special holder with a gas cell to transfer the sample from an inert gas environment to the inside of the TEM column. Comparison of the high-angle annular dark-field (HAADF) STEM images and 901.8 eV and at 885.6 and 903.5 eV, respectively.4+ predominated in the centre region (green square) of the thick catalyst particle, whereas Ce3+ predominated at the edge (blue square) of the thick catalyst particle, and the proportion of Ce3+ was highest at the centre (red square) of the thin catalyst particle. EELS maps of Ce in the thick and thin particles clearly showed the same tendency; that is, Ce3+ was enriched near the surface of the catalyst particles pattern of Ru/La2O3, many peaks assignable to LaOOH and La(OH)3 were observed, in addition to small peaks assigned to La2O3 molar ratios for fresh Ru/LayCey1\u2013Oy2\u20130.5 (0 \u2264 y \u2264 0.5) was linear after pre-reduction at 500 \u00b0C were finer than those that formed on La2O3 (mean diameter = 7.8 nm) and on CeO2 (mean diameter = 2.4 nm) see . In addi5_500red was 3.5 Table S2. These r0.5Ce0.5O1.75 and decreased the specific surface area of the catalyst from 42 to 21 m2 g\u20131. On the other hand, the H/Ru ratio decreased gradually as the pre-reduction temperature was increased from 500 to 800 \u00b0C. Note that when the reduction temperature was increased from 500 to 650 \u00b0C, the H/Ru ratio decreased from 0.46 to 0.35, but the mean diameter of the Ru particles remained unchanged. These results indicate that the surface Ru atoms were partially covered with partially reduced support material, at least after reduction at 650 \u00b0C, owing to the SMSI phenomenon, which is consistent with the EDX and EEL spectra , and to the formation of oxygen vacancies. Specifically, the lattice parameter of the cubic fluorite structure of La0.5Ce0.5O1.75, as measured by in situ XRD analysis, increased from 0.5577 nm at room temperature to 0.5596 and 0.5603 nm after treatment with H2 at 500 and 650 \u00b0C, respectively and in the mean diameter of the Ru particles (to 2.7 nm) . PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond cleavage, which is the rate-determining step for ammonia synthesis over Ru/La0.5Ce0.5O1.75, we determined the state of the adsorbed N2 molecules by means of Fourier transform infrared (IR) spectroscopy. The IR spectra measured after addition of 14N2 or 15N2 to Ru/La0.5Ce0.5O1.75_500red and Ru/La0.5Ce0.5O1.75_650red at room temperature are shown in \u20131 and a broader peak at around 1700\u20131900 cm\u20131. Note that the wavenumber of the broader peak decreased from 1883 to 1844 cm\u20131 when the pre-reduction temperature was increased from 500 to 650 \u00b0C. In the spectra measured after 15N2 adsorption, the two peaks were observed at lower wavenumbers (2091 and 1819 cm\u20131) relative to those for the 14N2 spectra, and the wavenumbers were in good agreement with those estimated by consideration of the isotope effect:\u20131 \u00d7 (14/15)1/2 = 2091 cm\u20131 and 1883 cm\u20131 \u00d7 (14/15)1/2 = 1819 cm\u20131. Similar peak shifts ascribable to the isotope effect were observed in the spectrum after adsorption of 15N2 on Ru/La0.5Ce0.5O1.75_650red. Therefore, all of the peaks were assignable to the stretching vibration mode of N2 adsorbed in an end-on orientation on the Ru particles. The peak at 2164 cm\u20131, the location of which was independent of reduction temperature, was assigned to N2 adsorbed on Ru atoms that interacted only weakly with the reduced support scale\" fill=\"currentColor\" stroke=\"none\">N bond of N2 was weakened by the contribution of SMSI even after reduction at 500 \u00b0C, and when the reduction temperature was increased to 650 \u00b0C, the contribution of SMSI was greater. That is, the partially reduced support, which is enriched in electrons owing to the reduction of Ce4+ to Ce3+ and to the formation of oxygen vacancies, partially covered the Ru particles. As a result, electron transfer from the reduced support to the Ru metal was greatly enhanced, and the electrons were transferred to the antibonding \u03c0-orbitals of N2; thus, the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds of N2 adsorbed on Ru atoms that interacted directly with the reduced support were further weakened. The ratio of the peak area of the higher-wavenumber peak to that of the lower-wavenumber peak decreased when the pre-reduction temperature was increased from 500 to 650 \u00b0C, which is consistent with an increase in the contribution of the SMSI.Our results indicate that the N\u20131) were abundant (H/Ru = 0.35) after pre-reduction at 650 \u00b0C explains the high ammonia-synthesis rate (31.3 mmol g\u20131 h\u20131) over Ru/La0.5Ce0.5O1.75_650red. In contrast, after pre-reduction at 800 \u00b0C, the Ru sites were very active (TOF = 0.108 s\u20131), but the number of active Ru sites was small (H/Ru = 0.11); thus the ammonia-synthesis rate over Ru/La0.5Ce0.5O1.75_800red (20.6 mmol g\u20131 h\u20131) was lower than that over Ru/La0.5Ce0.5O1.75_650red. Note that the specific surface area of Ru/CeO2_650red was only 20 m2 g\u20131, the mean diameter of the Ru particles was 3.1 nm, and H/Ru was 0.17, which indicates that sintering of the Ru particles and La0.5Ce0.5O1.75 was retarded in the case of Ru/La0.5Ce0.5O1.75_650red, and thus the H/Ru ratio for this catalyst remained high.These results demonstrate that pre-reduction at high temperature induced SMSI and enhanced the turnover frequency (TOF) but decreased the number of Ru active sites because the Ru particles became partially covered by partially reduced support. The fact that active Ru sites (TOF = 0.051 s2O and CO2) on the surface of the fresh catalyst are removed. However, pre-reduction at an excessively high temperature results in sintering, which decreases the number of active sites. Here, we found that 400\u2013450 \u00b0C was usually sufficient to reduce Ru3+. However, pre-reduction of Ru/La0.5Ce0.5O1.75 at the unusually high temperature of 650 \u00b0C produced a catalyst that showed a high ammonia-synthesis rate under mild reaction conditions . This catalyst consisted of fine Ru particles anchored on a heat-tolerant complex-oxidic support. During pre-reduction, the particle size of the Ru particles remained unchanged, but the particles became partially covered with partially reduced La0.5Ce0.5O1.75. A strong interaction between the Ru active sites and the reduced support accelerated the rate-determining step of ammonia synthesis, that is, N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond cleavage. We suggest that this simple strategy for the design of Ru catalysts\u2014that is, using a thermostable composite oxide containing a redox-active rare earth element in a cubic fluorite structure as a support, and pre-reducing the supported catalyst at high temperature\u2014will lead to the development of a more energy efficient ammonia-synthesis process, thus reducing global energy consumption and facilitating the eventual use of ammonia as an energy carrier.Pre-reduction of conventional supported-metal catalysts is crucial for their activation, because active metal sites are formed on the surface by reduction of metal oxides, and because adsorbates (such as HThere are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "A chiral Lewis acid-promoted cyclopropanation using a phenyliodonium ylide as the carbene precursor was developed. An EPR spectroscopy study supported a stepwise biradical mechanism. A chiral Lewis acid-promoted enantioselective cyclopropanation using phenyliodonium ylide as the carbene precursor was developed. A variety of spirocyclopropane-oxindoles with contiguous tertiary and all carbon quaternary centers were obtained in excellent outcomes . EPR spectroscopy study supported a stepwise biradical mechanism. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond provides efficient access to optically active cyclopropane derivatives that are essential motifs in natural productsi)-, Rh(ii)-, Ru(ii)-, and Co(ii)-complexes with diazo compounds, permits such cylcopropanations in high yields and selectivities.2{(S)-nttl}4]i)-bis(oxazoline) complexes.via enantiocontrol of an olefin substrate in the carbene transfer step, but the difficulty of gaining high stereoselectivity and yield lies in the background reaction and the readiness of carbene dimer formation.The catalytic asymmetric cyclopropanation of a Cvia the carbene transfer could also give access to these targets.N,N\u2032-dioxide complexesN,N\u2032-dioxide could bind 3-alkenyl-oxindoles into a perfect chiral environment, benefiting the cyclopropanation of a free carbene generated from spontaneous decomposition of phenyliodonium ylide malonate 2 complex catalyzed asymmetric cyclopropanation of 3-alkenyl-oxindoles with phenyliodonium ylide. Excellent diastereo and enantioselectivity were achieved for a variety of substituted spirocyclopropane-oxindoles under mild reaction conditions. Free carbene species formation was confirmed from EPR and HRMS analysis of the reaction system.Spirocyclopropane-oxindoles are versatile building blocks for the synthesis of natural products and pharmaceuticals.malonate . Herein,E)-N-Boc-3-alkenyl-oxindole 1a as the model substrate with phenyliodonium ylide malonate 2 in CH2Cl2 at 25 \u00b0C. The known enantioselective activation of the substrate 1a by metal complexes of chiral N,N\u2032-dioxide 2L-PiPr inspired us to examine it as the supporting ligand.2 obtained a trace amount of the desired spirocyclopropane-oxindole 3a (2 and Zn(OTf)2 enabled access to the product 3a in moderate yields and enantioselectivities yet high diastereoselectivities . The results were appealingly consistent with our Lewis acid-activation pathway. The following survey of the ligands coordinated with Ni(OTf)2 showed that other N,N\u2032-dioxides, including L-PiPh, 2L-PrPr and 2L-RaPr, were less competent than 2L-PiPr in terms of the reactivities and enantioselectivities (entry 4 vs. entries 5\u20137). The reaction was further optimized through systematic study of several parameters. An improved enantioselectivity and moderate yield was observed in toluene (entry 8). An encouraging 85% yield with 98% ee of the product was given in Et2O (entries 9 and 10). It was suspected that Et2O may effectively prevent dimerization of the phenyliodonium ylide, but the poor solubility of the catalyst in Et2O led to the low performance of this catalytic system. Considering this question, a mixed solvent system was tested to improve the situation. A mixed solvent of CH2Cl2/Et2O (v/v = 1\u2009:\u20094) was selected, and the asymmetric cyclopropanation gave a substantial improvement in catalytic yield with excellent diastereo and enantioselectivity .Our investigation commenced with the cyclopropanation of (E)-3-ester-substituted methyleneindolinone derivatives was next surveyed under the optimized reaction conditions . The electron-donating substituents at the C5-position of the oxindole ring were well-tolerated, giving slightly higher enantioselectivities than the electron-withdrawing ones . A 6-bromo-substituent resulted in a good yield . 3-Acyl substituted methyleneindolinone derivatives produced the corresponding spirocyclopropane products 3m\u2013p in excellent yields and enantioselectivities at lower reaction temperature. The alkyl-substituted alkenes, such as propyl, cyclohexyl and cyano, could also undergo this reaction smoothly, affording the desired adducts in moderate yields and good enantioselectivities . However, the reaction between (E)-1-Boc-3-tert-butylideneindolinone and phenyliodonium ylide 2 remained challenging due to the steric hindrance (4a\u2032\u2032).The generality of the catalytic cyclopropanation with a range of . It is noteworthy that no diastereomers were detected in most cases (>19\u2009:\u20091 d.r.), except for benzo[d]dioxole substituted 4o and 2-naphthyl substituted 4p. The sense of diastereoselectivity in the latter two cases was appreciably decreased, and a trace amount of the diastereomer was confirmed by 1H NMR spectroscopy (19\u2009:\u20091 d.r.), whereas the enantioselectivity was unaffected. As a representative substituted, 3-benzylidene-indolinone underwent efficient cyclopropanation, giving 4q in excellent yields. The absolute configuration of the product 3k and 4b was determined to be by X-ray analysis.4r\u20134s). Benzofuran-2(3H)-one enabled access to the desired product with an excellent yield; however, the outcome of enantiocontrol was disappointing (4t). Compared with the N-Boc oxindoles, the loss of the necessary bidentate manner of two carbonyl groups might have led to poor chiral induction.However, the deprotection of the Boc-group of the 3-aryl-substituted methyleneindolinone derivatives occurred, which prevented the cyclopropanation process. Changing the ratio of the substrates stigated . The rea1a with phenyliodonium ylide malonate 2 was carried out on a gram scale. The desired product 3a was generated in 99% yield, >19\u2009:\u20091 d.r. and 99% ee through a Lewis acid catalyzed nucleophilic ring-opening reaction using aniline as the nucleophile -N-Boc-3-alkenyl-oxindole 1a and phenyliodonium ylide malonate 2 proceeded smoothly in the absence of the catalyst, giving the desired product in 40% yield; neither the N,N\u2032-dioxide nor Ni(OTf)2 could substantially enhance the reaction. The outcomes of the reaction were unaffected when carried out in the dark. Clearly, the catalytic system of N,N\u2032-dioxide\u2013Ni(OTf)2 is a ligand-accelerated process in view of the excellent yields previously discussed. The Ni(ii)-complex of 2L-PiPr has been confirmed by X-ray analysis in our early study.1a or phenyl substituted 3-alkenyl-oxindole 1b\u2032 to the metal cation of the chiral catalyst was detected from ESI-MS spectra. Peaks at m/z 1200.4629 and 1176.4937 were assigned to [Ni2+ + 2L-PiPr + 1a + TfO\u2013]+ and [Ni2+ + 2L-PiPr + 1b\u2032 + TfO\u2013]+, respectively 2 showed no signals, indicating that there is no unpaired electron on the nickel(ii) center due to the strong coordination of the supporting ligands. Interestingly, the EPR spectrum of the mixture of oxindole 1a and phenyliodonium ylide 2 with or without the catalyst exhibits a similar rhombic band and is centered around g = 2.003 2 initially. The cyclopropanation was slower than intersystem crossing to the more stable triplet carbene 3:C(CO2Me)2, which exhibits two unpaired electrons. In this circumstance, the cyclopropanation occurs through a stepwise mechanism involving an analogous biradical intermediate. The unresolved hyperfine structure implied the interaction of 3:C(CO2Me)2 with the substrate.To determine the carbene intermediate, the reaction system was further characterized by EPR spectroscopy. The EPR X-band spectrum of = 2.003 . The int = 2.003 vs.1b. Tvia a free carbene intermediate center in a bidentate manner with two carbonyl groups. The facial-control of the carbene addition was directed by the blocking of the amide unit underneath the ligand. Initially, the decomposition of the phenyliodonium ylide generated a more stable triplet carbene. It would prefer electronic addition to the outer C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond because of the low steric hindrance and the stability of the triplet biradical intermediate. Due to the steric hindrance of the substituents on the biradical intermediates, the C\u2013C bond rotation is slower than spin flip of the intermediate. Therefore, high diastereo and enantioselectivity of the products were given.Therefore, in view of the aforementioned consequences as well as the structures of the catalystrmediate . SubstraN,N\u2032-dioxide/Ni(OTf)2 complex exhibited excellent performance in the reaction of 3-alkenyl-oxindoles with phenyliodonium ylide malonate under mild reaction conditions. The desired spirocyclopropane-oxindoles with contiguous tertiary and all carbon quaternary centers were attained in high yields and stereoselectivities . At the same time, when the catalytic system was applied to other non-oxindolic olefins, coumarins were also able to provide the bridge ring derivatives with good yields and enantioselectivities. A stepwise biradical process is suggested based on EPR spectroscopy. Further application of iodonium ylides and chiral N,N\u2032-dioxide\u2013metal complexes in asymmetric transformations are underway.In conclusion, we have developed a new asymmetric catalytic strategy for cyclopropanation of olefins. The chiral Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A complex with single, double and triple bonds between nitrogen and the same metal center has been synthesized, [NCr(NPh)(NPri2)2]\u2013. The complex shows differential activity, with some electrophiles attacking the imido and others the nitrido. t)(CHBut)(CH2But)(dmpe), has been prepared. The new complex is the nitrido, imido, amido anion [NCr(NPh)(NPri2)2]\u2013, which was structurally characterized with the [K(crypt-2.2.2)]+ counterion. The \u201cCr\u2013N 1-2-3\u201d complex was prepared from NCr(NHPh)(NPri2)2, which exists as this nitrido\u2013amido tautomer, rather than the bis(imido) Cr(NH)(NPh)(NPri2)2. By selection of electrophile, the nitrido\u2013imido salt K[NCr(NPh)(NPri2)2] can undergo reaction at either the imido or the nitrido to form unusual examples of nitrido or bis(imido) complexes.A nitrogen-based analogue of the Schrock and Clark \u201cyl-ene-yne\u201d complex, W(CBu The structure is shown schematically in 3Nitrogen-based complexes containing a variety of multiple bond types in the same complex are less explored. For example, while complexes with multiple imido groups are numerous, there are few examples of terminal nitrido\u2013imido complexes in the Cambridge Structural Database. One example of such a complex is the fascinating manganese-based nitrido complex [Li(OEti2)2] ] (2) in 76% yield as a dark red complex (1 with KH and 1 equiv. of (2.2.2)-cryptand in THF sequesters the potassium cation and liberates the anion for structural study. The amber product, [K(crypt-2.2.2)][NCr(NPh)(NPri2)2] (CrN123), was structurally characterized, and the anion is shown in Treatment of complex . The comCrN123, the average Cr\u2013NPri2 distance increased significantly over the value in 1 to 1.871(3) \u00c5, consistent with the stronger donor ability of imide relative to phenylamide. The Cr\u2013N(nitrido) distance, however, is the same as 1 within error. The N\u2013Cr\u2013N angles in CrN123 are all close to the tetrahedral angle and range from 106.0\u00b0 to 110.8\u00b0.In the solid-state structure of CrN123 exhibits fast diisopropylamide rotation consistent with imide being an extremely good donor as would be expected. Using 14N NMR spectroscopy one can easily distinguish the three different nitrogens in the complex along with the nitrogen in the cryptand at 560 ppm.In solution, cryptand at \u223c40 pt)(CHBut)(CH2But)(dmpe) and the anion of CrN123. The calculated W\u2013C bond orders for the neopentylidyne, neopentylidene and neopentyl groups were 2.65, 1.68 and 0.67, respectively. In the CrN123 anion, the Cr\u2013N bond orders to the nitrido, imido and amido were calculated as 2.84, 1.73, and 0.78, respectively, and are remarkably similar to the W\u2013C bond orders in the Schrock complex (CHBut)(CH2But)(dmpe) and the anion of CrN123 were examined by local Natural Resonance Theory (NRT) using NBO6, which are also shown parenthetically in trans-influencing alkylidene ligand having a lower order bond.In addition, Schrock's W equilibrium above. The preferred site of attack is the imide Ph](NPri2)2.The reactions of potassium salt he imide when mete.g., enolate attack by simple electrophiles generally occurs at oxygen.2 gave back 1 in 80% yield 2 (3).\u00b6The product from acyl chloride reaction was the same spectroscopically, but the product was not as clean as with acetic anhydride. That the electrophilic attack occurs at the imide rather than the nitride was definitively assigned by 14N NMR; 3 shows a distinct nitride resonance at 1011 ppm along with amidinate and diisopropylamide resonances at 402 and 203 ppm COMe bond of 1.971(2) \u00c5 relative to the diisopropylamide bonds of 1.823(2) \u00c5 due to the strongly electron-withdrawing group on the former. That the acyl group strongly interacts with the amido nitrogen can be seen in the short N\u2013C(acyl) bond distance of 1.348(3) \u00c5. There seems to be a weak Cr\u2013O(acyl) interaction as well with a distance of 2.753 \u00c5 pseudo-trans to the nitride with an N(nitrido)\u2013Cr\u2013O angle of 152\u00b0.Acyl-containing 3 gave a value of 15.09 kcal mol\u20131 for the N(Ph)C(O)Me amidinate fragment. This LDP value, for reference, is similar to chloride , but there may be steric influences in the LDP value resulting from the bidentate nature of the ligand, which would raise the LDP over its electronic value.An LDP measurement on a crude solution 2 with pivaloyl chloride leads to reaction at the nitrido nitrogen and formation of the green bis(imide) Cr[NC(O)But](NPh)(NPri2)2 (4), as shown in 14N NMR spectrum is definitive for this structure, with two imido resonances at 522 and 493 ppm Me and ClC(O)Bu4 is a rare, structurally characterized example of a transition metal imido complex bearing a carboxyl group on the nitrogen, and the first structurally characterized example of such a complex with chromium PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNC(O)But unit is slightly but significantly longer than in the Cr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNPh moiety at 1.688(3) and 1.646(3) \u00c5, respectively. The average Cr\u2013NPri2 distance in 4 is similar to 1 at 1.838(3) \u00c5. The N\u2013Cr\u2013N angles are fairly close to tetrahedral and range from 111.6(1)\u00b0 to 106.3(1)\u00b0.Complex CrN123. As is often the case, exploration of the syntheses required for the production of the complex led to unusual intermediates as well, and, once formed, the nitrido\u2013imido\u2013amido complex exhibits interesting reactivity commensurate with its unusual structure.Here, we have described the first example of a complex with nitrogen triple, double and single bonds to the same metal center, Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Quinoidal-vs.-aromatic synergy: Cyclopentadithiophene-vinylene oligomers with different sizes, in different oxidation states and as pro-aromatic quinoidals are studied considering balanced contributions of aromatic and quinoidal forms. H-cyclopentadithiophene vinylene repeating unit has been prepared and characterized by X-ray, electrochemical, spectroscopic and density functional theory methods. The oligomers in their neutral, oxidized and reduced forms have been investigated. The neutral compounds show a longer mean conjugation length than oligothiophenes and oligothiophene-vinylenes and display very rich redox chemistry with the stabilization of polycationic states of which the radical cations and dications are strong NIR absorbers, the latter displaying singlet diradicaloid character. An interesting complementarity between the sequence of aromatic-quinoidal structural segments in the radical cations and dications has been described and interpreted. Two derivatives with the 4,4 dihexyl-4H-cyclopentadithiophene vinylene unit, disubstituted either with electron donor, bis(triaryl amino) groups, or acceptors bis(dicyano-methylene) caps enforcing a quinoidal structure in the dithiophene-vinylene bridge, have been also synthesized and characterized. The radical cation of the triarylamine compound and the radical anion of the tetracyano compound similarly display hole and electron charge localization, or confinement, in the nitrogen and dicyano surrounding parts, or class II mixed valence systems, while their dication and dianion species, conversely, are open-shell diradical and closed-shell , respectively. The preparation of these new \u03c0-conjugated oligomers gives way to the realization of compounds with new electronic properties and unique structures potentially exploitable in organic electronics.A new series of \u03c0-conjugated oligomers based on the 4,4 dihexyl-4 Therefore, it is important to investigate the optoelectronic and structural properties of new oligomers as a function of oligomer length, ,CPDT unit alternating with double bonds to create a new oligomeric series from a dimer to a hexamer except for compound 5. In this case the synthesis was performed in 72% yield by using n-BuLi and DMF . This longest wavelength absorption band is due to a one-electron excitation from the HOMO to the LUMO (\u03bbmax for 6CPDTV.the LUMO . Whereas2CPDTV has been carried out by measuring the fluorescence spectra in solution at room temperature and at liquid nitrogen temperature (0 \u2192 S1 excitation (S1 \u2192 S0 emission). The small Stokes shift is an indication of the small conformational reorganization upon excitation, as it is expected for a molecule with only two degrees of dihedral rotation. At 77 K, the vibronic structure is better resolved and the Stokes shift has almost vanished due to minimization of motion around the vinylene bridge. In this context, the X-ray structure of 2CPDTV-Br has been resolved and is shown in 2\u2013Csp2 bond lengths (1.328(5)\u20131.455(5) \u00c5) consistent with a high degree of \u03c0-conjugation. In addition, nearly orthogonal orientations of the hexyl side chains effectively prevent \u03c0-stacking in the solid-state.An emission study of perature . The emi\u20131 and another one around 1400 cm\u20131. The 1600 cm\u20131 band is associated with the stretching vibration of the central C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, or \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C), which displays a progressive frequency downshift of 12 cm\u20131 from 2CPDTV \u2192 6CPDTV (8 cm\u20131 on 2CPDTV \u2192 3CPDTV) due to a progressive enlargement of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC vinylene bonds upon increasing the chain length. This is a clear fingerprint of the increasing of \u03c0-electron conjugation. The most intense Raman band of the spectra appears around 1400 cm\u20131 and correspond to a \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) of the thiophene rings of the CPDT unit. This band also experiences a frequency downshift with increasing oligomer size and this trend is consistent with other \u03c0-conjugated systems fibers on mica. This self-assembly is driven by \u03c0\u2013\u03c0 intermolecular interactions and by the interplay with the HOPG. In this case the nearly co-planar structure of the \u03c0-conjugated core offers a large available \u03c0-surface which promotes the formation of these long fibers.For most of the nCPDTVs . The \u03bbmax of these absorptions are represented in n where both bands fit linearly, indicating that their spectral properties are the result of the effective extension of the \u03c0-electron structure in the radical cation state along the increasing molecular platforms (not the whole structure) when enlarging the molecular size.The oxidation processes have been analyzed by nCPDTV\u02d9+ are shown in \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) band, appearing by nearly 30 cm\u20131 lower than in the neutral case. This is a clear indication that the first one-electron oxidation greatly affects the central vinylene, due to the partial C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC \u2192 C\u2013C transformation, or weakening, of the double bond. Changes in the frequencies of the thiophene bands are much smaller than those in the vinylene stretching band. Nonetheless, by progressing to the radical cations of the longer oligomers, the frequency of the vinylene Raman band upshifts from 1564 to 1568 cm\u20131 on +3CPDTV\u02d9 \u2192 +4CPDTV\u02d9 due to the further dissemination of the polaronic structural defect in a larger \u03c0-conjugated system. This effect reaches a plateau on +5CPDTV\u02d9/+6CPDTV\u02d9 for which the deformation is almost constant.The Raman spectra of the \u03bbmaxversus 1/n scale\" fill=\"currentColor\" stroke=\"none\">C\u2013C \u2192 C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC evolution.Additional one-electron oxidation of the radical cation produces the progressive disappearance of the pair of radical cation bands and the continuous rise of a strong absorption at wavelengths in between the two of the radical cations. The wavelength position of the rsus 1/n also fol2+6CPDTV where, as well as the strongest band at 2121 nm, another medium intensity band at 1178 nm is detected. This double-band pattern in the dications of oligothiophenes has been associated with the presence of polaron-pair defects, where the dication, instead of being embedded in one single structural bipolaron deformation, prefers to generate two radical cation structural defects by putting away the two charges.2+6CPDTV, thanks to its size and structure, is a candidate to stabilize the dicationic structure in a polaron-pair format rather than in a bipolaron, which is preferentially the case of the smaller oligomers, such as 2+3CPDTV.In addition, a new band appears at higher energies together with the strongest one just described. This is clearly seen in the case of nCPDTV2+ series (n = 4\u20136) are displayed in \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) band appears at 1568 cm\u20131 in 2+4CPDTV and displays the same frequency than the radical cation (+4CPDTV\u02d9 at 1568 cm\u20131) suggesting that the perturbation of the central vinylene is similar in the dication than in the cation. This is in consonance with the repulsion effect between the charges, which pushes these towards the terminal rings. In the two longer dications, 2+5CPDTV and 2+6CPDTV, the vinylene \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) bands are at almost the same values than in 2+4CPDTV (1567 cm\u20131 in both cases). The invariance of these Raman frequencies, among dications and also from the radical cations to dications of the longer oligomers, indicates that in the monovalent species, the structural alteration affects the central part of the molecule while in the divalent species these structural modifications do not happen in the center but are placed at the terminal rings leaving the middle site with a partial affectation . This spectroscopic-structural interpretation is in agreement with the formation of a polaron-pair structure in longer dications. In short, since the polaron-pair is composed of two separated radical cations, it is expected that these show similarities with the radical cations per se.11The Raman spectra of the EOC, are represented in 2+2CPDTV and 2+3CPDTV, \u0394EOC = 0 kcal mol\u20131, indicating that the stable form is the closed-shell configuration, or bipolaron structure. From 2+4CPDTV, \u0394EOC starts to be negative suggesting the preference for the open-shell form or polaron-pair \u2013 a preference that is more accentuated in the longer compounds.A polaron-pair charge defect can be described as an open-shell diradical dication and can be compared, by quantum chemistry, to the bipolaron charge defect, which corresponds only to one structural deformation and therefore it is a closed-shell system. Thus, we have calculated at the DFT/(U)B3LYP/6-31G** level the energy difference between the closed- and open-shell structures, both as singlet states, as a function of the oligomer size for the dications and these differences, \u0394EOC, the triplet state is progressively getting closer to the singlet ground electronic state due to the transformation of this into an open-shell diradical. The nature and consequences on the closed-shell to open-shell transition from the data provided by quantum chemical calculations in correlation with the experimental spectroscopic data in the case of 2+6CPDTV is now discussed in more detail.For these dications, we have also calculated the difference between the singlet ground electronic state and the first energy lying triplet. Following the tendency of \u0394+6CPDTV\u02d9 and of 2+6CPDTV from the B3LYP/6-31G** optimized structures) are represented which respectively depict a full quinoidal structure in the middle thiophenes for the radical cation and a pseudo-aromatic form for these also in the middle for the dication. In the dication, a full quinoidal structure can be formulated for the thiophene ring (closed-shell structure). However, this is unstable at the UB3LYP/6-31G** level and evolves by the rupture of one bond of this quinoidal structure giving way to the diradical species stabilized by the aromaticity recovery in the central thiophenes .6CPDTV (summarized in In DA(2CPDTV), disubstituted with triphenylamine groups at the terminal positions of the cyclopentadithiophenes to study the role of the nCPDTV bridge upon charge transfer from the donor amine groups. Compound 9 was prepared in 75% yield by the Horner\u2013Wadsworth\u2013Emmons reaction between 7 and 8.9 and 10 afforded DA(2CPDTV) in 66% yield (see Section 2 of ESI file for further detailsDA(2CPDTV) yields the radical cation, +DA(2CPDTV)\u02d9, which is characterized by the appearance of two very intense bands at the expense of the bands of the neutral at 514 nm (+2CPDTV\u02d9 and +3CPDTV\u02d9 and very close to those of +4CPDTV\u02d9 indicating the role of the triphenylamines in extending \u03c0-conjugation.One-electron oxidation of t 514 nm . These t+DA(2CPDTV)\u02d9 at 1879 nm emerging from a HOMO \u2192 SOMO excitation where the HOMO is mainly placed at the terminal phenyl amino rings, whereas the SOMO shifts the electron density mostly on the center of the dithiophene-vinylene core. The large red-shift on +2CPDTV\u02d9 \u2192 +DA(2CPDTV)\u02d9 is caused by the charge resonance of the positive charge of the radical cation between the two nitrogens of the triphenyl amines through the 2CPDTV bridge during the photoinduced absorption. However, in +2CPDTV\u02d9 the charge and its corresponding excitations are placed in the center of the molecule. This band is the so-called intramolecular charge transfer band or ICT band. From its spectrum, one can infer about the type of mixed valence system involved, either class II or class III. For class III, the band might show a vibronic component and a cut-off on the low-energy side, while class II systems exhibit Gaussian-shape bands without fine structure.+DA(2CPDTV)\u02d9 could be described as a class II mixed valence compound where the positive charge in the ground electronic state is mainly residing in one nitrogen partially stabilized towards the bridge.The lowest-energy lying band at 1848 nm is predicted by TDDFT/(U)B3LP/6-31G* in +DA(2CPDTV)\u02d9 yields the dication species, 2+DA(2CPDTV), whose electronic absorption spectrum in 2+6CPDTV, due to an open-shell polaron-pair dication. In this case, the great resonance stabilization of one charge in each nitrogen atom, together with the aromatization of the central dithiophenes, might justify the formation of this diradical species in this rather small compoundPost-oxidation of nCPDTV, Q(2CPDTV), together with its synthesis was accomplished using the well-established procedure: (i) Pd-catalyzed Takahashi couplingQ(2CPDTV) in good yield.Oligomers of this type are of interest as tetracyanoquinodimethanes oligothiophenes are being extensively exploited in the field of organic conjugated molecules.Q(2CPDTV) in the neutral state; the absorption spectra of the two relevant reduced states by spectroelectrochemistry are shown in Q(2CPDTV), in contrast with 2CPDTV, shows a two-electron reduction at \u20130.12 V and two one-electron oxidations displaced at higher anodic potential in comparison to the aromatic analogues, at 1.10 and 1.38 V. Neutral Q(2CPDTV) shows one very strong absorption band at 744 nm with a vibronic satellite at 679 nm (nCPDTV which exhibit the same pattern of bands (for instance in 2+3CPDTVhas a strong peak at 1157 nm and a satellite at 1012 nm) although in the case of the charged species the absorptions are displaced at longer wavelengths indicative of the smaller HOMO\u2013LUMO gaps. This is in accordance with a well defined closed-shell thienoquinoidal structure for Q(2CPDTV) whereas the dications display a transition between closed to open-shell structure such as discussed before.t 679 nm as a function of the temperature in solution are shown in Q(2CPDTV).nCPDTV and has been also described in other quinoidal oligothiophenes resulting from J-aggregates.The absorption spectra of Q(2CPDTV) have been carried out at reducing potentials. One-electron reduction gives rise to the progressive disappearance of the neutral band and the emergence of two new weak features at 1001 and 1889 nm (vibronic shoulder at 1585 nm). TDDFT/(U)B3LP/6-31G* of \u2013Q(2CPDTV)\u02d9 . Furthermore, this band is predicted to have a very low oscillator strength which is consistent with its weak absorbance in the experiment. The lowest-energy absorption band of \u2013Q(2CPDTV)\u02d9 resembles very much the ICT band of +DA(2CPDTV)\u02d9 either in their wavelength positions (1848 and 1889 nm respectively) or in their shapes (both are Gaussian type bands), indicating that the radical anion is also a class II mixed valence compound in which the additional negative charge resides in the dicyano-methylene partially invading the bridge (see +DA(2CPDTV)\u02d9, the HOMO \u2192 SOMO excitation represents an electron density displacement from the external sites to the internal core, producing a large variation of the dipolar momentum (and of the transition momentum). In \u2013Q(2CPDTV)\u02d9, the same excitation invokes a reorganization of the electron density in the whole molecule with a much smaller impact in the variation of the dipolar momentum of the transition (see \u2013Q(2CPDTV)\u02d9 gives rise to the dianion species which is characterized by a band at 586 nm and is typical of those of the aromatic nCPDTV revealing the full aromatization of the bithiophene moieties upon double charging \u02d9\u2013 allows tidge see . Both bacharging .Q(2CPDTV) in \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) band at 1543 cm\u20131, largely downshifted relative to the values in nCPDTV at 1590 cm\u20131, as a result of the weakening of the vinylene bond upon tetracyano substitution scale\" fill=\"currentColor\" stroke=\"none\">C) frequency at 1602 cm\u20131 in neutral 2CPDTV and at 1543 cm\u20131 in Q(2CPDTV) might represent the limits of a thienoquinoidization scale of the CPDTV \u03c0-conjugated structure, the former being the frequency of the full aromatic structure scale\" fill=\"currentColor\" stroke=\"none\">C) bands at 1564 cm\u20131 for +3CPDTV\u02d9 yields a quinoidization extension of 64% in line with the aromatic \u2192 quinoidal transitional character of the radical cations. For the dications, the quinoidal percentage is almost identical although the structure is not the same since the structural alteration is distributed in a polaron-pair form. \u03bd scale\" fill=\"currentColor\" stroke=\"none\">C) frequency values positions regarding the values in neutral Q(CPDTV2) and 2CPDTV. These observations show how the radical cations and dications both occupy a middle region between the full aromatic and full quinoidal points revealing the transitional character of their structures. Nevertheless, the neutral oligomers logically reside in a part of the quinoidal scale, closer to the aromatic fingerprint.The Raman spectrum of Fig. S69. TherefoH-cyclopentadithiophene vinylene repeating units has been prepared and characterized by spectroscopic and modelling methods. The neutral compounds display sizeable \u03c0-conjugation with increasing molecular size and a longer mean conjugation length than their oligothiophene and oligothiophene vinylenes homologues. Consequently the new compounds show rich redox chemistry with the stabilization of polycationic states of which the radical cations and dications are strong NIR absorbers \u2013 the latter displaying singlet diradicaloid states due to the gaining or recovery of aromaticity in the thiophene rings from the unstable quinoidal bipolaronic structures. Radical cations are described as having a quinoidal structure placed in the molecular center and flanked by two aromatic structures in the terminal parts. Conversely, the dications, as a result of their diradical character, display the reversed trend with aromatic segments in the molecular center surrounded by two quinoidal external moieties.A new series of \u03c0-conjugated oligomers based on the 4,4\u2032 dihexyl-4i.e., hole) or negative transport, two more derivatives were prepared. The CPDTV cores were substituted, either with electron donor triphenyl amino groups or with bis(dicyano-methylene) caps, enforcing a quinoidal structure in the dithiophene-vinylene bridge. The positive charge of the radical cation of the triarylamine compound is localized in the amine groups, and behave as class II mixed valence systems. The radical anion of the tetracyano compound, meanwhile has the same confinement effect of the charge in the environment of the electron accepting groups. The dication and dianion of these two compounds are open-shell biradical or polaron pair and closed-shell or bipolaronic structures respectively.To better investigate the potential charge transport properties as channels for either positive (The rich redox chemistry using these bridging groups, together with the adequate substitution of these cores, produce \u03c0-conjugated compounds with a variety of structures and properties. They can be exploited to function as materials for organic electronics but these materials are also of importance to gain insights into the intricate electronic structure of highly \u03c0-electron conjugated molecules.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Aerobic, site-selective C(sp3)\u2013H oxygenation using a novel N-oxyl radical directing activator is described. 3)\u2013H functionalization. The use of a radical N-oxyl directing activator promoted the aerobic oxygenation of benzylic, propargylic, tertiary, and unactivated acyclic methylene C(sp3)\u2013H bonds in aliphatic alcohols with \u03b3- (or \u03b4-) selectivity under mild conditions (room temperature to 50 \u00b0C). The reaction was unaffected by the presence of various oxidation-sensitive functional groups, which proved to be problematic in previously reported studies on the oxidation of C(sp3)\u2013H bonds. Structural modifications on the directing activator altered the regioselectivity, and thus provided an ultra-remote aerobic C(sp3)\u2013H oxygenation. The observed reactivity and regioselectivity could be rationalized in terms of the intramolecular conformational accessibility of the N-oxyl radical and the electronic characteristics of C(sp3)\u2013H bonds.Chemically reactive directing groups (directing activators) represent a promising strategy for mild and regioselective C(sp Especially for the streamlined synthesis of complex drug lead molecules, containing a multitude of Csp\u2013H bonds,3)\u2013H bonds located remotely from the hydroxy group,2) as the oxidant.3)\u2013H bonds;3)\u2013H bonds at a specific position, while simultaneously overriding the innately higher reactivity of the C\u2013H bonds at \u03b1-position with respect to the oxygen atom;2 in initiation of the oxygenation reaction.We were thus interested in a site-selective oxygenation of alcohols that is able to target C(sp3)\u2013H bonds \u2013H bonds .11N-hydroxyphthalimide (NHPI) chemistry \u2013H bonds homolytically to produce a carbon radical. By covalently attaching the DA to the hydroxy group of substrate alcohols, this C(sp3)\u2013H activation step should become an intramolecular process. Thus, it should be possible to selectively cleave specific C(sp3)\u2013H bonds that can engage in suitable spatial contact with the in situ-generated N-oxyl radical of the DA.2 to produce the corresponding oxygenated alcohols or ketones.14We devised a novel DA inspired by Ishii's hemistry ,12 whichN-hydroxyisoindolinone structure. As the reactivity of N-oxyl radicals towards C\u2013H cleavage follows their electron-deficiency,1 = CF3) was effective. Then we screened suitable metal catalysts that could promote N-oxyl radical formation from the N-hydroxy group as the solvent (2 (entry 6) and Mn(OAc)3\u00b72H2O (entry 8) were effective. Although the \u03b1-C(sp3)\u2013H bond adjacent to the ether oxygen atom is the innately more reactive site,3) atom that was predominantly oxygenated. Metal salts bearing counterions other than acetate showed very low reactivity.2 and Mn(OAc)3\u00b72H2O, and the desired C\u2013H oxygenation product 2a was obtained in 67% NMR yield (entry 10). The catalyst loading could be reduced to 5 mol% of each metal without loss of efficiency (entry 11). A DA with a simple alkyl substitution (R1 = Et), instead of a CF3 group, did not show satisfactory performance (entry 12). Introduction of another CF3 moiety on the aromatic ring of the DA did not improve the result (entry 13). Other types of DA modification resulted in production of complex reaction mixtures.16Based on this reaction design, we began our investigation of aerobic C\u2013H oxygenation by modifying the DA structure and performing a screening of oxygenation conditions using DA-bound alcohol substrates . In orderoup see using 1-2O entry were effN-hydroxy-3-trifluoromethylisoindolinone moiety and reaction conditions using Co(OAc)2 (5 mol%), Mn(OAc)3\u00b72H2O (5 mol%), and O2 (1 atm) in TFE (0.1 M) at 40 \u00b0C represent optimal conditions (condition A). The use of a fluoroalcohol solvent was crucial for high reactivity, as fluoroalcohols are able to stabilize radicals, dissolve molecular oxygen, and are resistant to oxidation.17On the basis of this study, we established that a DA containing an 3)\u2013H bonds, however, resulted in the formation of complex product mixtures. For example, exposing 1i to condition A afforded 2i and C\u2013C bond-cleaved products , Me2S (1.2 equiv.), and O2 (1 atm) in TFE (0.1 M) at 40 \u00b0C (condition B) as the best set of conditions for the oxygenation of tertiary C(sp3)\u2013H bonds.Applying the cobalt-catalyzed conditions to the oxygenation of tertiary C(spproducts .18 As th3)\u2013H bonds of aliphatic alcohols (1a\u20131g) regioselectively into the corresponding C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds (2a\u20132g). Using condition B, the oxygenation of tertiary C(sp3)\u2013H bonds proceeded generally in higher yield (2h\u20132r). The condition B was applicable to a gram-scale reaction of 1h without significant loss of efficiency.3)\u2013H bonds, which proceeded rapidly, even at lower temperature (2s\u20132ae).20Using these conditions allowed the oxygenation of a broad variety of DA-bound alcohols as shown in N-oxyl radical moiety in DA. For example, the very challenging substrate 1d possesses a flexible alkyl chain, but was converted into a 1.2\u2009:\u20091 mixture of \u03b3-oxo (2d) and \u03b4-oxo (2d\u2032) products. Conversely, the corresponding \u03b1-, \u03b2-, and \u03b5-oxo products were not detected or detected only in trace amounts. Oxygenation of substrates 1e\u20131g, containing an ester or a phthalimide moiety, occurred exclusively at the \u03b3-position.2ivs.2j; 1j was unreactive in 24 h at 40 \u00b0C). Benzylic C\u2013H oxygenations also showed a similar reactivity tendency.R)-1k, 1l, 1z, 1aa, and 1ac afforded products that were selectively oxygenated at the \u03b3-position. For DA-bound (+)-menthol, i.e. a diastereoisomer mixture of (R)-1k and (S)-1k, containing three tertiary C(sp3)\u2013H bonds, only one specific C\u2013H bond of (R)-1k was converted into a C\u2013OH bond. The corresponding product (R)-2k exhibited a partial isopulegol hydrate structure and was obtained within 2 h in almost quantitative yield. However, diastereomer (S)-1k was completely unreactive. The contrasting reactivity between these two diastereomers is probably due to the accessibility of the C\u2013H bond to the intramolecular N-oxyl radical moiety, as suggested by the X-ray structure of O-(4-nitrobenzyl)-(R)-1k and molecular modeling.N-oxyl radical: in case of 1o, oxygenation was selective towards a \u03b3-tertiary C\u2013H bond rather than towards a propargyl C\u2013H bond, whereas oxygenation of 1ac was selective towards a propargyl C\u2013H bond rather than towards a tertiary C\u2013H bond.Our approach, based on using a radical DA and molecular oxygen, thus provided access to previously unattained C\u2013H oxidation protocols. Especially the following three points should be worth noting: firstly, the C\u2013H oxygenation proceeded only at specific and predictable positions depending on the accessibility of the 2u, 2ad and 2ae), haloarenes (2v and 2x), a silyl arene (2y), aryl and alkyl boronates (2q and 2w), a terminal hydroxy group (2m), an acetal (2n), ethers , a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond (2p), and a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond (2o and 2aa\u20132ac).Secondly, various oxidation-sensitive functional groups were tolerated, due to the mild reaction conditions employed that avoid the use of reactive oxidants. Thus, C\u2013H oxygenation could be conducted in the presence of electron-rich (hetero)aromatic rings (R)-1k differed from that in the previously reported Fe- or Ru-catalyzed C(sp3)\u2013H hydroxylation of O-acylmenthol.1m, 1n, 1o, and 1p, even though those compounds contain more reactive \u03b1-hydroxy (1m), acetal methylene (1n), propargylic (1o), and allylic (1p) C\u2013H bonds.Thirdly, the DA approach was able to override the innate reactivity difference between C\u2013H bonds. The observed regioselectivity in the reaction of (via the linker structure. As shown in 3), thus demonstrating complementary regioselectivity to the oxygenation of 1z (with use of molecular oxygen has not yet been reported in the literature. This result thus provides an opportunity for a controlled switching of the oxygenation site by designing a suitable linker between the target C(sp3)\u2013H bond and the reactive N-oxyl radical moiety.20The regioselectivity can be changed on of 1z . The DA-3)\u2013H oxygenation, we conducted several control experiments -3) promoted by an equimolar amount of DA-bound methanol (1af) or acetophenone (1ag) produced a significantly different profile compared to oxygenation, shown in O-Me-1a in the presence of 1af resulted in complete recovery of unchanged O-Me-1a after 20 h at 80 \u00b0C -3 with 1ag required a raised temperature (50 \u00b0C), and the position selectivity was moderate species, which are generated through the reaction between Co(ii) and O2.N-oxyl radical 5 abstracts a hydrogen atom of a C\u2013H bond at a proximate position, generating carbon radical species 6. Trapping 6 with molecular oxygen, the resulting alkyl peroxy radical 7 is quenched by a hydroperoxy radical generated in the initiation step to produce alkyl peroxide 8, or through intramolecular hydrogen abstraction from DA, generating 9. In the case of tertiary C\u2013H oxygenation, undesired decomposition pathway from 8 \u2013H oxygenation of aliphatic alcohols, using an N-oxyl radical group as a directing activator. Benzylic, propargylic, tertiary, and even the very challenging acyclic methylene C(sp3)\u2013H bonds were thus converted to C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO or C\u2013OH bonds under mild conditions (room temperature to 50 \u00b0C), while high functional group tolerance was maintained. Molecular oxygen was used as the stoichiometric oxidant, and the reactions proceeded regioselectively at the \u03b3 (and \u03b4) position(s), whereas the \u03b1, \u03b2, and other positions beyond the \u03b4 position remained intact. This regioselectivity can be explained in terms of the intramolecular accessibility of the reactive N-oxyl radical site, despite the low regioselectivity between \u03b3 and \u03b4 positions in electronically non-biased substrates is a current limitation that must be solved in future works. Preliminary structural tuning of the DA led to an alteration of the regioselectivity, providing a selective ultra-remote aerobic C\u2013H oxygenation. Although laborious synthesis of DA-bound substrates has remained problematic at this stage, devising catalytic applications of DAs will overcome this limitation. Efforts in such a direction are currently ongoing in our laboratory.In conclusion, we have developed a method for the regioselective C(spSupplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Simple acid\u2013base properties explain the differences in amide and imide dimerisation, and represent an alternative to the secondary interactions hypothesis. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOS) and H-bonded scale\" fill=\"currentColor\" stroke=\"none\">OHB) carbonyl groups in imides. Notwithstanding the considerable body of experimental and theoretical evidence supporting the JSIH, there are some computational studies which suggest that there might be other relevant intermolecular interactions than those considered in this model. We conjectured that the spectator carbonyl moieties could disrupt the resonance-assisted hydrogen bonds in imide dimers, but our results showed that this was not the case. Intrigued by this phenomenon, we studied the self-association of a set of amides and imides via1H-NMR, 1H-DOSY experiments, DFT calculations, QTAIM topological analyses of the electron density and IQA partitions of the electronic energy. These analyses revealed that there are indeed repulsions of the type OS\u00b7\u00b7\u00b7OHB in accordance with the JSIH but our data also indicate that the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOS group has an overall attraction with the interacting molecule. Instead, we found correlations between self-association strength and simple Br\u00f8nsted\u2013Lowry acid/base properties, namely, N\u2013H acidities and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO basicities. The results in CDCl3 and CCl4 indicate that imides dimerise less strongly than structurally related amides because of the lower basicity of their carbonyl fragments, a frequently overlooked aspect in the study of H-bonding. Overall, the model proposed herein could provide important insights in diverse areas of supramolecular chemistry such as the study of multiple hydrogen-bonded adducts which involve amide or imide functional groups.Amides dimerise more strongly than imides despite their lower acidity. Such an unexpected result has been rationalised in terms of the Jorgensen Secondary Interactions Hypothesis (JSIH) that involves the spectator (C Hydrogen bonds (HBs) in amides and imides are ubiquitous directional forces in nature. HBs in these functional groups are responsible for the secondary interactions, along with other interactions of the tertiary and quaternary structures of proteins.The formation of amide and imide dimers is frequently studied by NMR or IR spectroscopy to determine self-association constants in solution.(i)Kdimer of amides as compared to imides in spite of their lower acidic character.HB\u00b7\u00b7\u00b7H contacts as shown in HB\u00b7\u00b7\u00b7OHB) and hydrogens (H\u00b7\u00b7\u00b7H) involved in HBs between the monomers (black double arrows in the above-mentioned figure). Nevertheless, the imide dimers present two additional repulsive interactions OHB\u00b7\u00b7\u00b7OS (green arrows), wherein OS denotes the oxygen atom in a spectator carbonyl group. The repulsions OHB\u00b7\u00b7\u00b7OS are also consistent with the notion of two nearly parallel repulsive C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO electric dipoles in the imide dimers (purple arrows). There is a considerable body of theoretical and experimental work which is concordant with the JSIH. For example, crystallographic data of some imides such as maleimide, trans-3,4-diphenylsuccinimide, and 1-methyl-hydantoin show that the separation between OS and OHB is very long (>4 \u00c5)The Jorgensen Secondary Interactions Hypothesis (JSIH),1.000000,.000000 s(ii)As schematised by the black arrows in (iii)An analysis of the inductive and resonance effects in these compounds suggests not only a higher acidity of the protons in imides but also a smaller basicity of their oxygens, because of the distribution of the negative charge of the zwitterionic structure across two carbonyl groups as illustrated in 1H-NMR titrations, 1H-DOSY experiments, electronic structure calculations as well as quantum chemical topology tools, namely, the Quantum Theory of Atoms in Molecules (QTAIM)HB and OS, but these interactions are more than compensated by other intermolecular attractions. Moreover, we found that criterion (iii) is the most suitable to explain the experimental tendencies of the self-association of imides and amides through an interplay of the respective basicity and acidity of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and N\u2013H groups. In other words, a weak HB acceptor carbonyl (as it is the case in many of the examined imides) can significantly weaken the investigated self-association processes despite a strong acidity of the imidic hydrogen and vice versa. Our results not only explain the studied phenomenon but also provide a model which could be exploited in diverse areas of supramolecular chemistry, such as the study of multiple hydrogen-bonding complexes which entail the amide and imide functional groups.Given this background, we performed a combined experimental and theoretical study to elucidate the factors governing the self-association of amides and imides. We analysed hypotheses (i)\u2013(iii) through A1), an archetype for the study of the self-association of the functional groups concerned in this investigation,d, acetonitrile-d3 and DMSO-d6, and also considered the reported value in CCl4 in order to select the most suitable solvent for this research. Another feature of 2-pyrrolidone which makes it particularly suitable for this purpose is the fact that it is liquid at room temperature and thereby its self-association is easier to study in deuterated solvents which cover a broad range of polarity. As expected, Kdimer diminishes with the polarity of the medium of the studied amide and imide dimers as reported in rcalc). As expected, structurally similar compounds have close values for rH and rcalc, e.g., the radii of amides A1, A2 and imide I4 are alike because all of them are unsubstituted five-membered rings. A4, A5 and I1 are likewise six-membered heterocycles with closely related structures as reflected in their values of rcalc and rH. Nevertheless, the cyclic chains in the uracil derivatives I5 and I8 and the benzo-derivatives A6, A7 and I3 introduce discrepancies between rH and rcalc. This condition occurs because the spherical particle model employed in the estimation of rH does not represent the oblate spheroid character of these dimers. Despite these differences, the experimental rH values are always smaller than the computed rcalc data . These results indicate that the investigated amides and imides do not form trimers or larger clusters to an appreciable extent.Next, we employed e.g., A5vs.I1, A1vs.I2, A6vs.I3 and A4vs.I6\u2013I13. These results point out that an increase in acidity does not necessarily lead to a stronger self-association. For example, the decreasing orders of acidity of the structurally related imides (I7\u2013I11) are I7 \u2248 I10 > I11 > I8 > I9, while those of dimerisation are backwards. We found, however, also exceptions to this behaviour, for instance A5vs.A4 and I5vs.I8 in which acidity and self-association increase in the same direction. Based on the above experimental results, now we proceed to examine the three considered hypotheses concerning the comparison of the self-association between amides and imides.Once we chose a suitable solvent and verified that the dimeric species are indeed predominantly formed in solution, we consider now the compounds shown in (i)A5 and the imide I1 dimers are only HBs. QTAIM shows no repulsion of either kind OHB\u00b7\u00b7\u00b7OHB, H\u00b7\u00b7\u00b7H or OHB\u00b7\u00b7\u00b7OS. In particular, we did not detect either attractive or repulsive interactions involving the spectator carbonyl moieties in the analysed imide dimers (Table S1 in the ESII1 molecule displayed in green) with the atoms of another I1 monomer (shown in orange). We note that the interaction between OHB and OS is indeed strongly repulsive . After considering all the atoms of the neighbouring molecule, the atom OS has an overall repulsion with the interacting monomer . The nearly parallel C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOHB and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOS dipoles also present a slight repulsive interaction between them .We test here the hypothesis that repulsions involving the spectator carbonyl groups are responsible for the smaller degree of dimerisation of imides as compared with that of amides. For this purpose, we used electron density topology analyses in accordance with the QTAIM theory and the IQA approach. The results shown in \u20131 + 10.7 kcal mol\u20131 = \u20131.8 kcal mol\u20131). We computed the same value for the other spectator carbonyl group. This attraction between the spectator carbonyl moiety and the whole interacting molecule evidences the numerous relevant intermolecular atomic pairwise interactions in the system.The same analysis can also be carried out for every atom in one monomer which included up to terms which depend on R\u20136 (e.g. dipole\u2013hexadecapole and quadrupole\u2013octupole interactions), R being the distance between two multipoles. One of the main conclusions of this study concerns the difficulty to explain the relative stability of H-bonded clusters by only considering a subset of atomic pairs located in the boundaries between the interacting monomers as opposed to taking into account the whole set of intermolecular pairs of atoms in the system.The importance of the intermolecular interactions not considered by the JSIH in hydrogen-bonded dimers had already been pointed out by Popelier and Joubert.(ii) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds as schematised in VXC| of these bonds. The results shown in the bottom of VXC| values and the \u0394DIs for the C\u2013N and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOs bonds are barely affected. Moreover, in most cases the \u0394DI of the spectator C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and the absolute value of VXC increase slightly because of the formation of the RAHB in imide dimers as opposed to the flux of electrons suggested at the top of QTAIM analyses allowed us to consider the potential disruption of the resonance-assisted hydrogen bonds in imide dimers by virtue of their spectator carbonyl groups top of . The eve PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOs interactions. These data point out that the disruption of the RAHB in imides is not the factor which explains the larger self-association of amides with respect to imides, a condition consistent with the observation that electron delocalisation is not the most stabilizing effect in resonance-assisted hydrogen bonds.44Additionally, the changes in the DIs and distances of the bonds involved in this RAHB are substantially larger than those of the neighbouring C\u2013N and C(iii)E(A), and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO protonation, E(B), as shown in E(A)| while a high value of |E(B)| indicates a strong basicity of the oxygen in the carbonyl group. The deprotonation energies for a wide variety of species which include imides, amides, (thio)ureas,Ka values, ditto for |E(B)| and pKBH+, which indicates the pKa of the conjugate acid of the species under consideration | and |E(B)| for compounds A1\u2013A7 and I1\u2013I13 | and |E(B)| whose distribution of points adjusts to a first-degree polynomial model. The species A2 was not contemplated in the correlation because it is a cyclic carbamate that can form bifurcated hydrogen bonds with CHCl3 as indicated by DFT geometry optimisations and schematised in Fig. S31 in the ESI.A2 in comparison with the rest of the studied compounds. Indeed, the exclusion of A2 improved the value of r2 in E(B)| and |E(A)| (CE(B)|| and CE(A)||) are positive and negative respectively. These conditions support the model that self-association increases with the acidity of the N\u2013H moiety and the basicity of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group. Besides, |CE(B)||| > |CE(A)|||, and hence the dimerisation processes of the examined compounds are more sensitive to changes in the basicity of the carbonyl group than to modifications of the acidity of the amidic or imidic hydrogen. In general, this model points out that a high acidity or basicity by itself does not ensure a large association constant since there must be a balance between these properties to observe a substantial value of Kdimer. In other words, very poor acceptor or donor features of a system can substantially hinder its self-association process as it is the case for imides and basic amides A3 and A5 respectively. This analysis indicates that the low basicity of the carbonyl groups in imides allows us to explain why these compounds dimerise less strongly than amides notwithstanding their larger acidic character. The model in 3. For example, the lowest value of the dimerisation constant corresponds to maleimide I4, a compound with high acidity but the one with the smallest basicity among the analysed systems. On the other hand, A4 undergoes the strongest self-association among the molecules of interest. It has the highest basicity and an acidic character similar to the examined imides. These results point out that the occurrence of an aromatic sextet scale\" fill=\"currentColor\" stroke=\"none\">O fragments in the self-association of amides and imides is also observed for the uracil analogues I6\u2013I13. These imides are more basic than other compounds with the same functional group and hence dimerise more strongly. Furthermore, the consideration of the basicity of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups is also useful to rationalise which fragments are involved in the dimerisation. For example, it is well known that uracil derivatives form hydrogen bonds with the oxygen at C-4 rather than the one at C-2.via a C-5, C-6 double bond. When this is no longer the case, e.g.I5 and I11, the most basic carbonyl is the one at C-2 as illustrated in the middle and bottom of I5 scale\" fill=\"currentColor\" stroke=\"none\">O basicities. In addition, there is a good correlation between the experimental values of ln\u2009Kdimer with those predicted in the model of Following the same arguments concerning the relative importance of basicity and acidity of the examined compounds, we can explain why among the studied five-membered heterocycles, amide 4 as well.3 ln\u2009Kdimer and (ii) the basicity of the carbonyl group together with the acidity of the N\u2013H moiety as shown in CE(B)|| > 0, CE(A)|| < 0 and |CE(B)||| > |CE(A)|||. The last-mentioned condition indicates once again that the dimerisation constant of amides and imides is more sensitive to the basicity of the carbonyl group than to the acidity of the N\u2013H moiety, hence the larger association of amides in comparison to imides.We considered amide and imide dimerisation constants reported in CCls well.3 Fig. 8)4 as wellKheter indicates that hetero-association between A5 and I1 is stronger than in each homodimer as illustrated in 1H-NMR spectroscopy results. The change in the N\u2013H chemical shift due to complexation, \u0394\u03b4N\u2013H, is reported to increase with the strength of the association.A5\u2013I1 adduct involved in the heterodimer is smaller than the corresponding value for the HB in the imide homodimer. Fig. S15A1 and I2 heterodimers. The measurement of Kheter was performed with a constant total amount of amide A1 while imide I2 was added to the system. The value of \u03b4N\u2013H diminished through the titration, a condition indicative of a weakening of the HB entailing the amidic hydrogen. In the opposite experiment the value of \u03b4N\u2013H for the imidic proton increased more than in the corresponding homodimers, evidencing the strengthening of the hydrogen bond of the heterodimer which involves this proton. The last-mentioned effect is also observed in the A5\u2013I1 molecular cluster.The examination of heterodimers gives further insights about the dimerisation of amides and imides. The determination of HB-1 in is largeA5\u2013I1 and A1\u2013I2 heterodimers, the strongest HB-1 is formed between the most acidic proton (the one in the imide) and the most basic carbonyl (found within the amide). On the other hand, the weakest HB takes place in the interaction of the less acidic proton, i.e. N\u2013H of amides A5 and the less basic carbonyl (the one in the imide). The strengths of the HBs in the amide and imide homodimers are between these two extremes. These results along with those of DFT geometry optimisations of the A5\u2013I1 heterodimer show the following trend of descending HB strength:Concerning the A5 homodimer > HB in I1 homodimer > HB-2HB-1 > HB in A5 as opposed to HB-2 which does not present this effect. Despite the aforementioned agreement of the JSIH with structural data, this hypothesis is not completely consistent with the H-bond strength and distance patterns found in the heterodimers. In contrast, the consideration of the acidity and the basicity of the N\u2013H and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO fragments explains the observed association constants, hydrogen bond distances and chemical shift patterns in these systems. The QTAIM and IQA analysis of the intermolecular interactions within the heterodimers A5\u2013I1 scale\" fill=\"currentColor\" stroke=\"none\">O in the imide presents a strong repulsion with the oxygen of the neighbouring carbonyl involved in the HB and with the rest of the molecules of the amide. These repulsions are even stronger than in the case of the I1 homodimer. Still, the hydrogen bond closest to the OS atom in the A5\u2013I1 heterodimer is the strongest of the system. The relative strength of these HBs is revealed by their lengths as previously discussed and other indices used in the study of hydrogen bonds which include (i) Espinosa's empirical formula PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group has an overall attractive interaction with the neighbouring imide or amide in a similar fashion to the corresponding homodimers. These IQA homo- and heterodimer results point out that the OHB\u00b7\u00b7\u00b7OS repulsions or those between the corresponding dipole carbonyls are not the decisive factor for the energetics of the amide and imide dimerisation.This order is similar to that found by Jorgensenrs A5\u2013I1 and A1\u2013IKdimer for these systems. The interplay of acidity and basicity allows us to explain other baffling results e.g. the fact that 2-ethyl-2-methylsuccinimide self-associates much more strongly (by a factor of 15) than tetrafluorosuccinimide.Kdimer. Likewise and according to the JSIH, the fluorinated compound should dimerise to a larger extent because the charges in the carbonyl oxygens are less negative than those in the alkylated succinimide. The alternative explanation that we offer is that the fluorine atoms reduce substantially the basicity of the carbonyls, thereby impairing the self-association of this compound.Our investigation provides an alternative model to the JSIH to rationalise experimental observations concerning the homo- and heterodimerisation of amides and imides, for example, the hydrogen bond distance pattern in amide/imide heterodimers and the relative magnitude of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO moiety than it is to the acidity of the N\u2013H group. Hence, the modification of the basicity of this carbonyl represents a good opportunity in the modulation of the strength of the non-covalent interactions established by these groups. For example, the change of a carbonyl in a crucial amide for a more basic imino fragment in vancomycin enhances the association properties with the cell wall of bacteria immune to this antibiotic.Additionally, our results can be useful in understanding why amides are much more used in many technologies such as crystal engineering, development of materials and pharmaceuticals than imides.Finally, the results of our investigation suggest a different approach for the analysis of the stability of multiple hydrogen-bonded systems such as uracil\u2013diamino purine, cytosine\u2013guanine and ADA\u2013DAD systems.General experimental and computational details are given in the ESI. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group, the acidity of the N\u2013H moiety and Kdimer resulted in a first-degree model suggesting that the proton acceptor capacity of the carbonyl group is more important than the acidity of the amidic or imidic hydrogens for the self-association of the investigated compounds. This model also indicates that there must be a balance between the respective acidity and basicity of the N\u2013H and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO fragments to observe a substantial self-association of these systems. Particularly, amides exhibit larger self-association constants because of their higher basicities in comparison with imides. Similar conclusions were drawn from systems investigated in CCl4. Our results also explain the hydrogen bond distance patterns found in amide and imide homo- and heterodimers. The acidity/basicity balance in the dimerisation of amides and imides is an alternative approach to the JSIH in order to explain this phenomenon. Overall, we expect that the application of the insights presented herein will prove valuable to understand and modulate hydrogen bonds between the investigated functional groups which are present in a wide variety of supramolecular systems throughout biology and chemistry.We investigated the reasons underlying the stronger self-association of amides as compared to imides. Our results indicate that the spectator carbonyl presents indeed repulsions with the oxygens involved in the HB but these repulsive interactions are not the key factor in the energetics of the H-bonded systems examined herein. This statement is based on the relevance of the pairwise interactions which are not accounted for by the JSIH and the experimental and theoretical examination of amide\u2013imide homo- and heterodimers. Our results also reveal that the spectator carbonyl groups in imides do not interfere with the resonance-assisted hydrogen bonds in the dimers of these species. Then, we consider the Br\u00f8nsted\u2013Lowry acid/base properties of the HB donors and acceptors involved in the interaction within these molecular aggregates. The examination of the basicity of the CThere are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Diastereoselective aerobic dehydrogenative cyclization of hydrazones is described via a copper-catalyzed sp3 C\u2013H functionalization process. 3\u2013H bond of amines. Among this reaction category, copper-catalyzed selective C\u2013C bond formation under atmospheric O2 is of considerable research interest and significant progress has been achieved in recent years. In comparison, development of the intramolecular version of this transformation is still in its infancy. Furthermore, diastereoselective cyclization with this transformation has not been achieved. Here, we describe the highly diastereoselective intramolecular dehydrogenative cyclization of N,N-disubstituted hydrazones by a copper-catalyzed sp3 C\u2013H bond functionalization process. The reaction protocol utilizes O2 as the oxidant and shows great functional group compatibility. Computational studies suggest that a 5-center/6-electron disrotatory cyclization mechanism is probably involved in the process for controlling the diastereoselectivity. This work represents the first example of a copper-catalyzed, direct intramolecular diastereoselective coupling reaction via an iminium ion intermediate. Additionally, it provides an environmentally friendly and atom efficient approach to access substituted pyrazolines, an important structural unit in many biologically active compounds.Transition metal-catalyzed cross dehydrogenative coupling is an important tool for functionalization of the \u03b1 Csp Representative examples, which have expanded product diversity, include oxidative dimerization of phenols, naphthols and electron-deficient arenes, cross coupling of terminal alkynes with electron-deficient arenes, and intramolecular dehydrogenative cyclization of anilides.via an sp3 C\u2013H bond functionalization process has also been established on tertiary amines by Miura, Li, and others.via oxidation of the corresponding amine. This intermediate then serves as an active electrophile for the subsequent nucleophilic addition reaction.N,N-dimethylaniline derivatives have been reported as suitable substrates. Furthermore, this transformation is limited to the intermolecular version, in part due to the non-selective oxidation of the amine over the internal nucleophile.8The oxidative dimerization of terminal alkynes, the Glaser reaction reported in 1869, is the first example of copper-catalyzed aerobic dehydrogenative coupling.We envisaged that the use of an enamine-type motif as an internal nucleophile could potentially overcome this drawback and extend the reaction scope to intramolecular cyclizations.123 C\u2013H functionalization strategy was thoroughly examined and further explored to expand its scope of synthetic utility. To provide important mechanistic insights into various factors that control the product distribution, density functional theory (DFT) calculations were further conducted to rationalize the diastereoselectivity observed. The combined work of chemical synthesis, NMR, and computation revealed how the interplay of molecular configurations, steric effects, and the symmetry requirement of electronic structure reactivity, can be utilized to precisely control the diastereoselectivity in the products, thereby providing a valuable guidance to rational designs of the related synthetic routes.Here we report detailed studies in which the copper-catalyzed sp1a) under atmospheric O2 2 and stoichiometric KI, KOAc, and DBU in NMP with O2 as the external oxidant (entry 5). Interestingly, this reaction showed high diastereoselectivity, with the anti isomer as the major product. Further optimization showed that this reaction was improved by using NMP and tAmOH as co-solvent (entry 8). It was then noticed that the reaction yield was significantly increased by extending the reaction time to 12 h from 4 h (entry 9). In addition, the replacement of DBU with DBN significantly increased the reaction rate, and the desired product was obtained in 86% yield within 4 h (entry 10). Moreover, the cyclization could also be effectively catalyzed by other CuI or CuII sources under the above modified conditions (entries 13\u201317).Our study commenced with copper-catalyzed dehydrogenative cyclization of 1,1-dibenzyl-2-(1-phenylpropylidene)hydrazine (heric O2 . After a2a\u2013h). Interestingly, the reaction showed a substrate-dependent diastereoselectivity pattern, and the anti-isomers of 2a and 2b were obtained as the major products while the syn-isomers of 2c\u2013g were the major forms. It is noteworthy that the current methods for the synthesis of syn-4,5-pyrazolines rely primarily on the [3 + 2]-cyclization of a diazo compound and an olefin, which often suffers from poor regioselectivity.N-benzyl group could also be replaced with another alkyl group (2i\u2013n), in which the aromatic hydrazones favored the anti-isomers, and the aliphatic substrates favored the syn-isomers. Additionally, an N-phenyl substituted hydrazone yielded exclusively the syn-isomer 2o, providing an important and tunable strategy to selectively access either anti or syn pyrazolines. Moreover, 1,2,3,4-tetrahydroquinoline is also an effective substrate (2p).With the optimized conditions in hand, the scope of hydrazone substrates was studied . As expeN-cyclohexylidene-3,4-dihydroisoquinolin-2(1H)-amine (via an oxidative sp3 C\u2013H activation process: mercuric oxide-mediated dimerization and Rh(iii)-catalyzed cycloaddition.In our previous study of dehydrogenative cyclization/aromatization of 1-benzyl-1-isopropyl-2-(1-phenylethylidene)hydrazine, it has been demonstrated that both electron-donating and electron-withdrawing groups on the phenyl rings were compatible.H)-amine . For eacsyn diastereoisomers as the major products (5b\u2013o). Generally, electron-withdrawing group-substituted substrates provided better yields compared with electron-donating substituents in the same position. Considering that an iminium ion intermediate is formed prior to cyclization, these results are not surprising since an electron-withdrawing group increases the electrophilicity of the iminium ion and thus facilitates the cyclization. Additionally, an electron-withdrawing group may retard the further oxidation of pyrazolines and thus minimize formation of the by-product pyrazoles. Furthermore, a steric effect was observed for this reaction: C8-substituted hydrazones gave lower yields of desired products compared with the C5-, C6-, or C7-substituted substrates. Finally, halogens are also well tolerated, which provides the opportunity for further product manipulation.As shown in 1 of 5a and H12a, H12b were observed. Additionally, there was no observable NOE between H1 and H13, or H14 and H12a or H12b. These results indicate that H13 and H14 have the syn relationship.NOESY analysis was carried out to confirm the relative configuration of the product . NOEs be5q and 5r). The 5-membered ring substrate also provided a good yield of product 5p under the modified reaction conditions. Furthermore, \u03b1,\u03b2-unsaturated hydrazones are also compatible (5u and 5v), which allows for further transformation of the initial products. As expected, good to high yields of products were obtained on substrates with substituted cyclohexylidenehydrazine moieties . In addition, good to excellent diastereoselectivity was observed with \u03b1-substituted cyclohexylidenehydrazine, favoring the anti-products (5w\u2013y). In comparison, \u03b3-substituents on the cyclohexylidenehydrazine moiety did not significantly affect the relative diastereoselectivity (5z and 5aa). Additionally, linear hydrazones are also compatible with the oxidative conditions, favoring the formation of the syn-isomers. However, in this case, the ratio of diastereoselectivity was dramatically decreased. Considering that there are two possible conformers present in the iminium ion intermediate oxidized either from 5z or 5aa, the above result is not surprising.Next, an imine substrate scope study was carried out . The rea1 generates the radical cation Avia an SET process. The radical cation A is then converted into the iminium ion intermediates B1 and B2via either an oxidation/deprotonation or a homolytic cleavage process. Tautomerization of the imine moiety on B1 and B2 to enamine-type diastereoisomers C1, C2, C3 and C4, followed by subsequent nucleophilic addition provides the intermediate D1 and D2, which then give pyrazoline 2 upon deprotonation. The rationale of high syn over anti diastereoselectivity is also proposed based on the previous reports by Hoffmann and List.C will behave as an sp2 hybridized atom. Therefore, the lone-pair of electrons on the nitrogen will participate in the \u03c0-conjugation together with the four \u03c0 electrons in the double bonds, resulting in a 5-center/6-electron system, similar to the situation found in a pentadienyl anion. For such homoconjugated systems, the HOMO is actually a \u201csymmetric\u201d nonbonding orbital, which is 1,5-bonding with the preferred U planar configuration. For thermally induced electrocyclic ring closures, the symmetric HOMO requires a disrotatory mechanism, which results in the corresponding product 2. It should be mentioned that \u03b1-alkyl Cu species could potentially be formed from deprotonation of the intermediates B1/B2 under basic conditions. Intramolecular nucleophilic addition of these Cu species could also provide the desired products.On the basis of the above results and our previous report,2a, 2f, 2p, 5a, and 5ab).Toward molecular-level understanding of diastereoselective 5-center/6-electron cyclization mechanism displayed in these copper-based C\u2013H functionalization reactions, we performed density functional theory (DFT) investigations on five representative systems related to diastereoselective cyclization in TS) from C \u2192 D, which seems to be the most relevant step in determining the diastereoselectivity of the products, were especially emphasized, and the transition states from B \u2192 C are outside the scope of this work and thus were excluded. The influence of the solvent environment on the reaction was evaluated by using the polarizable continuum models (PCM) methodN-methylpyrrolidone (\u03b5 = 32.2) and 2-methyl-2-butanol (\u03b5 = 5.78) are not available in Gaussian 09, we chose ethanol as the solvent (\u03b5 = 24.55). Frequency analysis was carried out to verify the optimized geometry as minima or transition state, and to obtain free energy of each species. The intrinsic reaction coordinate (IRC)All the calculations were carried out for the five systems by using Gaussian 09 program suites.1), the iminium ion (B), the enamine-type intermediate (C) and the charged pyrazoline product (D). For 2f, 2p, 5a, and 5ab, C1/C2 represents the enamine-type intermediates with trans/cis conformation for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond; D1/D2 represent the syn/anti charged pyrazoline intermediates. For 2a, B1/B2 is the iminium ion with trans/cis conformation for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ double bond; D1/D2 are the anti/syn charged pyrazoline intermediates. Given the conformational combinations of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds, four enamine-type intermediates are considered for this system, which are referred to as C1 , C2 , C3 and C4 , respectively. The transition state of a disrotatory/conrotatory reaction is specified by \u201ca\u201d/\u201cb\u201d, for example, TS2a/TS2b is the transition state of the disrotatory/conrotatory reaction of C2. The proposed mechanism, optimized geometries, some free energy profiles, and original data are shown in ESI.In all systems, the symbols used to represent the related species are: hydrazine scale\" fill=\"currentColor\" stroke=\"none\">N+ bond is \u20130.769e in C1, \u20130.609e in TS1a, and \u20130.466e in TS1b, respectively. The charge of the terminal carbon atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond is 0.916e in C1, 0.679e in TS1a, and 0.729e in TS1b, respectively. As shown in Fig. S1,D scale\" fill=\"currentColor\" stroke=\"none\">N+\u2013N\u2013C) and D scale\" fill=\"currentColor\" stroke=\"none\">C) of the pyrazoline ring in TS1a are 22.1\u00b0 and \u201319.6\u00b0, respectively. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds form a pseudo-plane with the dihedral angle D scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) to be 3.1\u00b0, and the neutral nitrogen atom is a little out of that plane. For TS1b, the values of D scale\" fill=\"currentColor\" stroke=\"none\">N+\u2013N\u2013C), D scale\" fill=\"currentColor\" stroke=\"none\">C) and D scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) are 35.0\u00b0, 7.5\u00b0, and 40.2\u00b0, respectively, implying that the pyrazoline ring in TS1b is twisted and it looks like a helical folding conformation. Clearly, compared with the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC in TS1b, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC in TS1a is closer to a coplanar conformation. The distance R scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) between the two terminal carbon atoms of the pyrazoline ring is 2.25 \u00c5 in TS1a and 2.15 \u00c5 in TS1b. These show that the C \u2192 D reaction is a 5-center/6-electron cyclization constituted by C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, although this system does not completely satisfy the H\u00fcckel rule .Based on the complexity of these systems, the computational results of C is less stable than its tautomer B by 10.9 kcal mol\u20131. The reaction is endothermic by 1.9 kcal mol\u20131 for C \u2192 D1 process, and exothermic by 4.3 kcal mol\u20131 for C \u2192 D2 process. Even though the conformation of the cyclohexane is chair in D1 and twist boat in D2, D2 (anti) shows more stability than D1 (syn). The reason may be that the two bulky substituents are on the same side of the pyrazoline ring in D1, while the two substituents are on the different side of the pyrazoline ring in D2, causing the steric repulsion being stronger in D1 than in D2. However, the active free energy generating D1 is 1.6 kcal mol\u20131 lower than that generating D2, indicating that C prefers to undergo disrotatory process (TS1a) to form D1, rather than conrotatory process (TS1b) to afford D2. This may be because the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC (5-center/6-electron) in TS1a is more coplanar and more satisfies the H\u00fcckel rule compared with that in TS1b. These are in good agreement with the diastereoselectivity observed in the copper-based C\u2013H functionalization reactions (syn-D1 is major product).In the free energy profiles , C is leTS1a and TS1b were compared. As shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ bond overlaps with the under lobe of the orbital of the terminal C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH constitutes a delocalized system in TS1a. In TS1b, the under lobe of the orbital of the C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ bond overlaps with the upper lobe of the orbital of the terminal C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. However, the delocalized orbitals of the N\u2013NH bond do not overlap with the C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ bond, generating an orbital nodal surface between the C atom and the N atoms. These demonstrate that TS1b is less stable and more difficult to cross than TS1a, supporting that the intermediate C tends to undergo a disrotatory process to form D1, rather than a conrotatory process to afford D2.To better understand this point, HOMOs of C \u2192 D1/D2 processes are exothermic and the active free energy barriers are easier to overcome, shown in parentheses in The presence of a solvent can obviously improve the reaction process scale\" fill=\"currentColor\" stroke=\"none\">N+ bond is \u20130.464e in C1, \u20130.321e in C2, \u20130.313e in C3, \u20130.579e in C4, \u20131.407e in TS1a, \u20130.388e in TS1b, \u20130.983e in TS2a and \u20130.656e in TS2b, respectively. The charge of the terminal carbon atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond is separately 0.139, 0.337, 0.641, \u20130.077, 0.131, 0.297, 0.042 and \u20130.161e for the corresponding species. Seen from Fig. S2,D scale\" fill=\"currentColor\" stroke=\"none\">N+\u2013N\u2013C) and D scale\" fill=\"currentColor\" stroke=\"none\">C) of the pyrazoline ring in TS1a are 30.0\u00b0 and \u201333.8\u00b0, respectively. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds form a pseudo-plane with the dihedral angle D scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) of \u20132.4\u00b0, and the neutral nitrogen atom is a little out of that plane. The corresponding values are separately \u201344.1\u00b0, 4.3\u00b0 and \u201337.7\u00b0 in TS1b, also suggesting that the pyrazoline ring in TS1b is a pseudo-plane. However, this pyrazoline ring in TS1b is slightly apart from the coplanar conformation compared with that in TS1a. In TS2a, the values of D scale\" fill=\"currentColor\" stroke=\"none\">N+\u2013N\u2013C), D scale\" fill=\"currentColor\" stroke=\"none\">C) and D scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) are separately 37.6\u00b0, 23.3\u00b0 and 56.5\u00b0, implying that the pyrazoline ring is twisted and it looks like a helical folding conformation. The corresponding values are separately \u201329.2, \u201318.9\u00b0 and \u201343.7\u00b0 in TS2b, showing that the pyrazoline ring in TS2b is twisted with the opposite direction, but the twist with the opposite direction would increase the steric hindrance between the methyl group and the benzyl group. The distance R scale\" fill=\"currentColor\" stroke=\"none\">N+\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC) between the two terminal carbon atoms of the pyrazoline ring is 2.36 \u00c5 in TS1a, 2.32 \u00c5 in TS1b, 2.34 \u00c5 in TS2a, and 2.34 \u00c5 in TS2b. These also demonstrate that the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC constitutes a 5-center/6-electron system, but not a typical H\u00fcckel system (not completely coplanar).The charge of the carbon atom in the CC1 and C2 are more stable than C3 and C4, supporting that C1 and C2 are major intermediate compared with C3 and C4. The anti product D1 is more stable than the syn product D2 in the gas phase, which is also attributed to the steric repulsion between the two bulky substituents on the same side of the pyrazoline ring in D2 compared with D1. TS1a is \u20133.3 kcal mol\u20131 relative to TS1b, and TS2a is \u20133.1 kcal mol\u20131 relative to TS2b, showing that C tends to undergo a disrotatory (TS1a/TS2a) process to give the product, rather than a conrotatory process (TS1b/TS2b) to afford the product. The reason may be that the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC in TS1a is closer to the H\u00fcckel system compared with that in TS1b (5-center/6-electron and coplanar conformation), and the steric hindrance between the methyl group and the benzyl group in TS2a is smaller than that in TS2b. Compared with C3 and C4, C1 and C2 overcome less of a free energy barrier, determining the diastereoselectivity of this reaction. Similar to 5a, the presence of a solvent can obviously improve the reaction process (the C \u2192 D1/D2 processes are exothermic and the active energy barriers become easier to overcome), but the overall diastereoselective trend is the same as that captured from gas-phase calculations. The main reason for such a huge improvement of the reaction is also the solvation of ions.As shown in TS1a, TS1b, TS2a and TS2b were compared. Seen from PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ bond overlaps with the under lobe of the orbital of the terminal C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and phenyl group constitute a delocalized system in TS1a. In TS1b the under lobe of orbital of C atom in C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+ bond overlaps with the under lobe of the orbital of the terminal C atom in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, but the delocalized system only consists of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH and phenyl groups. The delocalized system in TS1b is smaller than TS1a, suggesting that TS1b is less stable and more difficult to overcome than TS1a. Compared with the orbital in TS2a, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN+\u2013NH\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC in TS2b does not constitute a complete delocalized orbital, and two orbital nodal surfaces are found between the C and N+\u2013NH, and N+\u2013NH and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds, also suggesting that TS2b is less stable and more difficult to cross than TS2a. Therefore, C1 (C2) goes through a disrotatory process to form D1 (D2), instead of a conrotatory process to afford D2 (D1).To better understand this point, HOMOs of 2f, two enamine-type iminium ion intermediates are formed in the cyclization process, resulting in two different diastereoisomers. Based on the calculation (see ESIE)-isomer is more stable, resulting in syn-2f as the major product via a 5-center/6-electron disrotatory cyclization process. In the case of 2p, the intermediate with the methyl and phenyl groups on the opposite side is the major isomer, and thus the anti-isomer becomes the major product. For 5ab, the intermediate with two alkyl groups on the same side becomes the major isomers, and thus the syn-5ab is the major product. Compared with 5ab, the diastereoselectivity in 5ac is lower because the ratio of the major isomer is decreased due to the stronger steric effect by the isopropyl group. The combined results from experimental and computational studies suggest that the diastereoselectivity of products is possibly determined by the relative stability of the enamine-type iminium ion intermediates via a 5-center/6-electron disrotatory cyclization process.Furthermore, computational studies of three more representative substrates were also carried out to account for the diastereoselective outcome . For 2f,n see ESI, the (E)N,N-disubstituted hydrazones with good functional group tolerance was developed using a copper-catalyzed double sp3 C\u2013H bond functionalization process. The observed diastereoselectivity was rationalized by a 5-center/6-electron disrotatory cyclization mechanism, which was supported by computational studies. As the first example of the copper-catalyzed aerobic diastereoselective intramolecular cyclization of amines via an iminium ion intermediate, this transformation provides a straightforward, environmentally friendly and atom efficient access to pyrazolines with up to five fused-ring systems. The enantioselective version of this transformation is currently under study in our laboratory.In summary, a highly diastereoselective aerobic intramolecular dehydrogenative cyclization of CCR2CC chemokine receptor 2CCL2CC chemokine ligand 2CCR5CC chemokine receptor 5TLCThin layer chromatographySupplementary informationClick here for additional data file."}
+{"text": "Assembly of bimetallic complexes on boron clusters by coordination of coinage metalcations to Ru\u2013B single bonds. i)cations insert into B\u2013Ru bonds of the (BB)\u2013carborynecomplex of ruthenium with the formation of four-membered B\u2013M\u2013Ru\u2013Bmetalacycles. Results of theoretical calculations suggest that bonding within thesemetalacycles can be best described as unusual three-center-two-electron B\u2013M\u00b7\u00b7\u00b7Ruinteractions that are isolobal to B\u2013H\u00b7\u00b7\u00b7Ru borane coordination for M = Cu and Ag, orthe pairs of two-center-two electron B\u2013Au and Au\u2013Ru interactions for M = Au.These transformations comprise the first synthetic route to exohedral coinage metal borylcomplexes of icosahedral closo-{C2B10} clusters,which feature short Cu\u2013B (2.029(2) \u00c5) and Ag\u2013B (2.182(3) \u00c5) bondsand the shortest Au\u2013B bond (2.027(2) \u00c5) reported to date. The reportedheterometallic complexes contain Cu(i) and Au(i) centers inuncharacteristic square-planar coordination environments. These findings pave the way torational construction of a broader class of multimetallic architectures featuringM\u2013B bonds.In this work, we introduce a novel approach for the selective assembly of heterometalliccomplexes by unprecedented coordination of coinage metal cations to strained singleruthenium\u2013boron bonds on a surface of icosahedral boron clusters. M( Synthesis and reactivity of bimetallic complexes containing late transition metals andcoinage metals have attracted considerable attention due to the discovered cooperativereactivity in cross-coupling reactions, transmetallation processes, and the relevance toheterogeneous catalysis.20closo-C2B10H12.Transition metal boryl complexes have been extensively studied because of both fundamentaland applied reactivity potential. Success in metal-catalyzed borylation of a variety oforganic substrates led to the enormous growth in studies of structure, bonding, andreactivity of complexes, containing metal\u2013boron bonds. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1100000000000000000000000000000000 1111110000000000000000000000000000 0011111111000000000000000000000000 0000001111111100000000000000000000 0000000000111111110000000000000000 0000000000000011111111000000000000 0000000000000000001111111100000000 0000000000000000000000111111110000 0000000000000000000000000011111111 0000000000000000000000000000001111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000001111 0000000000000000000000000011111111 0000000000000000000000111111110000 0000000000000000001111111100000000 0000000000000011111111000000000000 0000000000111111110000000000000000 0000001111111100000000000000000000 0011111111000000000000000000000000 1111110000000000000000000000000000 1100000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tRu metalacycle can be described as a metalacycloboropropane with two highlystrained 2c-2e B\u2013Ru \u03c3 bonds. The significant distortion of the exohedral bonds ofthe carborane cage resulted in enhanced reactivity associated with these bent B\u2013Rubonds, which themselves served as nucleophilic reaction centers with organic substrates,exhibiting metal\u2013ligand cooperative activity. We conjectured that the bonding pair ofthe distorted electron-rich B\u2013Ru bond in the BB-carboryne metallacycle could beaccessible for interaction with inorganic electrophiles such as coinage metal cations.The exohedral metal center on a carborane cage can be simultaneously connected to twovertices giving rise to carborynes, which are inorganic analogs of benzynes.i),Ag(i), and Au(i) to a single Ru\u2013B metal\u2013boryl bond and theformation of the heterobimetallic complexes featuring unique B\u2013M\u2013Ru\u2013Bbridging interactions 2-m-2,6-dehydrocarborane)3, and Au(SMe2)Cl in1\u2009:\u20091 ratio led to the selective formation and isolation of complexes2-Cu, 2-Ag, and 2-Au, respectively. The31P and 11B NMR spectra of crude reaction mixtures reflected cleantransformation of 1 to new products, which possessed lower symmetry of aboron cage according to 11B NMR spectra, consistent with interaction of coinagemetal cations with one of the B\u2013Ru bonds of the parent carboryne 1. The11B and 11B{1H} spectra of products contained pairs ofsignals corresponding to two different metalated boron atoms of the icosahedral cage,indicating the persistence of such interactions in solution. The complexes2-Cu, 2-Ag, and 2-Au were isolated in70\u201380% yields and were found to be moderately stable in air in the solid state inthe absence of light. The single crystal X-ray diffraction study revealed the molecularstructures of 2-Cu, 2-Ag, and 2-Au (Reaction of the (POBBOP)Ru(CO)and 2-Au . In all 2-Cu crystallized as a chloride-bridged dimer from anacetonitrile/hexanes mixture \u00c5, which is only slightly longer than 2c-2e Cu\u2013B bonds in therecently reported Cu(i) boryl complexes (1.980(2)\u20132.002(3) \u00c5).2-Cu is 2.630(1) \u00c5, which is longer thanCu\u2013Ru bonds in bimetallic complexes (2.439(1)\u20132.552(7) \u00c5)The complex mixture . The copi). The distortion from the planarityfor the Cu(Cl)2(B)(Ru) unit is remarkably small with the\u03c44 value of 0.17 . To the best of our knowledge, this is one of the lowest values ofthe \u03c44 parameter for Cu(i) complexes reported todate.Two bridging chloride ligands (Cu\u2013Cl distances are 2.321(1) \u00c5 and 2.329(1)\u00c5) complete the coordination sphere of the copper center to four-coordinate planargeometry, which is uncharacteristic for Cu cation inserted into one of the B\u2013Ru bonds of thecarboryne complex. The Au1\u2013B2 bond length is 2.027(2) \u00c5, which is the shortestAu\u2013B distance reported to date, as it is slightly shorter than 2c-2egold\u2013boron bonds in the previously disclosed gold boryl complexes(2.069(3)\u20132.144(4) \u00c5).2-Cu, the relativelylong Ru1\u2013B2 distance of 2.723(3) \u00c5 implies no significant bonding while theRu1\u2013B1 bond length (2.133(2) \u00c5) is within the typical range for rutheniumboryls. to 2-Cu . The Au2(B)(Ru) moiety in 2-Au exhibits four-coordinate planarconfiguration that is unusual for Au(i)\u03c44 = 0.11) as indicated by nearly linearRu1\u2013Au1\u2013Cl1A and B2\u2013Au1\u2013Cl1 angles (167.5(1)\u00b0 and177.5(1)\u00b0, respectively).Similarly to the copper coordination environment in 2-Ag, crystallized from anacetonitrile/hexanes mixture as a monomeric acetonitrile adduct (i) cation inserted into one of the B\u2013Rubonds of the carboryne complex. The Ag1\u2013B1 bond length is 2.182(3) \u00c5, whichis, to the best of our knowledge, the third example of the silver\u2013boryl bond andthis distance is comparable to those in two previously reported silver boryl complexes(2.118(2) \u00c5 and 2.122(4) \u00c5).61The light-sensitive silver insertion product, e adduct . The Ag(+ acrossthe ruthenium\u2013silicon double bond is 2.681(1) \u00c5.2-Cu.The Ru1\u2013Ag1 distance is 2.750(1) \u00c5, which is longer than the previouslyreported distances in unsupported bimetallic complexes (2.608(1)\u20132.709(1)\u00c5)1 to 2-M complexes. The values of \u03bd(CO) =2010 and 1958 cm\u20131 (\u03bd(CO)average = 1984cm\u20131) for the BB-carboryne complex 1 can be compared tothe corresponding parameters in coinage metal insertion products (see ESI\u03bd(CO)average values for these complexes are 1995cm\u20131 for 2-Cu, 2002 cm\u20131 for2-Au, and 2017 cm\u20131 for 2-Ag. Thus, in allthree cases, the \u03bd(CO)average increased reflectingcoordination of Lewis acidic cations to one of Ru\u2013B bonds in 1.Trends in values of stretching frequencies of carbonyl ligands of the ruthenium centercan provide an insight into changes of its electronic structure upon conversion of11B NMR spectra of 1 and 2-M inC6D6 showed changes of chemical shifts of metalated boron atomsupon coordination of coinage metals. The starting complex 1 exhibited asignal for the (BB) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1100000000000000000000000000000000 1111110000000000000000000000000000 0011111111000000000000000000000000 0000001111111100000000000000000000 0000000000111111110000000000000000 0000000000000011111111000000000000 0000000000000000001111111100000000 0000000000000000000000111111110000 0000000000000000000000000011111111 0000000000000000000000000000001111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000001111 0000000000000000000000000011111111 0000000000000000000000111111110000 0000000000000000001111111100000000 0000000000000011111111000000000000 0000000000111111110000000000000000 0000001111111100000000000000000000 0011111111000000000000000000000000 1111110000000000000000000000000000 1100000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tRu metallacycle at \u20132.8 ppm while the corresponding signals for theboron atom of the B\u2013Ru bond are at \u20131.5 ppm for 2-Cu, +2.1 ppmfor 2-Au, and \u20132.7 ppm for 2-Ag. The signals of boronatoms of B\u2013M bonds are at \u201310.3 ppm for 2-Cu, \u20139.7 ppm for2-Au, and \u201311.9 for 2-Ag. The 31P spectra of2-M complexes are similar with a signal in the 204\u2013205 ppm range .The comparison of ii) center making it heptacoordinate. Inthe structure C, coinage metal forms the 2c-2e electron bond to one of the boron atom ofthe cage, while the structure D features coordination of the B\u2013M bond to theruthenium center. The structure E is derived from the structure C by addition of thedative M\u2013Ru interaction.Several resonance structures can be considered to describe bonding inB\u2013Ru\u2013M\u2013B metallacycles in these complexes . The strThe presence of unique B\u2013M\u2013Ru\u2013B metallacycles in the reported newcomplexes prompted us to examine the bonding situation in more detail using the analysisof the electron density in the framework of the quantum theory of atoms-in-molecules(QTAIM)2-Cu, 0.74 for 2-Ag, and 0.75 for2-Au. These values are also close to DI values corresponding to 2c-2emetalboron bonds in the starting carboryne complex 1 (DI = 0.69).Topological analysis revealed the presence of the Ru\u2013B1 bond path in all complexes.The bonding between ruthenium and the boron atom B1 exhibits concentration of the electrondensity (blue contours) that is bent outward the Ru\u2013B1 bond path, indicating thestrain of this metal\u2013boron bond. The Ru\u2013B1 bonding in all three structures canbe considered a 2c-2e bond with delocalization indices of 0.73 for 2-Cu and2-Ag as demonstrated by DI values of 0.31 (2-Cu) and 0.33(2-Ag). The ruthenium\u2013coinage metal interactions in these complexesdo not have bond paths for 2-Cu and 2-Ag. The DI values of theseinteractions are 0.42 for 2-Cu, 0.40 for 2-Ag. Such an extensive\u201csharing\u201d of electrons between Ru, B2, and Cu or Ag is indicative of3-center-2-electron bonding . Note that the depletion ofthe electron density on B2 also results in the weakening of the B1\u2013B2 bonding.The Ru\u2013Au\u2013B2 bonding situation is noticeably different. First, the QTAIManalysis revealed the presence of the Ru\u2013Au bond path with a DI value of 0.58. TheDI value of Au\u2013B2 bond is 0.81, which is also higher than that for Cu\u2013B2 andAg\u2013B2 bonds. At the same time, the Ru\u2013B2 delocalization index in\u03b7a; the maximum ELF values for each basin) and basinpopulations for selected valence basins ofinterest. For 2-Cu and 2-Ag, the ELF analysis revealed thepresence of one disynaptic valence basin V (which is similar to that in thestarting complex 1) and one trisynaptic V or V basin,respectively. Attractors of trisynaptic V and V basins are located closeto the centers of Ru\u2013M\u2013B2 triangles (but somewhat displaced closer to B2).Populations of these basins are 2.6 e in 2-Cu and 2.0e in 2-Ag.Electron localization function (ELF) is visualized by 3D representations , and its2-Au reveals a substantial change in the bondingsituation. The trisynaptic basin observed in 2-Cu and 2-Ag issplit into two independent disynaptic basins V and V. The population value\u03a9 for the V interaction is 1.9 e, which is similar to that ofthe V basin and corresponds to the localized 2c-2e bonding. The V basin hasthe smaller \u03a9 value of 0.7 e indicating a weaker 2-center bondinginteraction.The ELF analysis of 2-Cu complex. The transition ofthe trisynaptic basin in 2-Cu and 2-Ag complexes indicative of2c-3e bonding to two disynaptic basins in 2-Au as found in the ELF analysisagrees with the results of the QTAIM analysis discussed above. As there is no directRu\u2013B2 bonding, the value of the delocalization index of Ru\u00b7\u00b7\u00b7B2 interaction can beused as an indicator of the 3-center boding. In 2-Cu and 2-Agthis DI value is rather large, 0.31 and 0.33, respectively, whereas in 2-Auit is reduced to 0.10. In parallel, DI/DI values are increased from0.40\u20130.42/0.66\u20130.63 in 2-Cu and 2-Ag to 0.58/0.81 in2-Au. Thus, both QTAIM and ELF analyses show a transition from the lesslocalized three-center B\u2013M\u00b7\u00b7\u00b7Ru bonding in 2-Cu and 2-Agto the more localized distinct two-center Ru\u2013Au and Au\u2013B2 interactions in2-Au.Notably, the sum of the V and V basin populations is close to theV basin population in the analogous 2-Cu and 2-Ag complexes is the 3c-2e B\u2013M\u00b7\u00b7\u00b7Ru interactiondescription that is often used for bridging B\u2013H\u00b7\u00b7\u00b7M interactions in boranes and boronclusters while bonding in 2-Au is closer to the localized 2c-2e Au\u2013Bbond. These findings are consistent with the Au\u2013B bond length in 2-Aubeing the shortest reported to date. The bonding of Cu and Ag to boron atoms in2-Cu and 2-Ag is also unusually strong with B\u2013M distancescomparable to the recently reported isolated 2c-2e bonds of coinage metals with nucleophilicboryls. Importantly, the formation of these complexes represents a unique synthetic strategyfor generation of the first examples of the exohedral coinage metal\u2013boryl bonds in{C2B10} carborane clusters as the direct activation of theirB\u2013H bonds by Group 11 metals remains unknown.The results reported herein uncover unusual reactivity of the ruthenium BB-carboryne withinorganic electrophiles and introduce a new approach for the rational construction ofmultimetallic complexes supported on the surface of polyhedral boron cages.+, Ag+, and Au+ into strained Ru\u2013Bsingle bonds in 1 is unprecedented. Notably, coordination of coinage metalcations to alkylidenes, silylenes, and borylenes/boryls has been reported.+ to a platinum\u2013aryl bond has beendisclosed.1 has not been reported. It also remains to be seen if similartransformations can be observed in the case of other metal boryls or in the case of otherstrong inorganic Lewis acids thus providing an alternative synthetic access to novelmultimetallic architectures featuring M\u2013B bonds.Insertion of CuThere are no conflicts to declare.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Synthesis and transformations of AgNO3 complexes of trans-cycloheptene (TCH) and trans-1-sila-4-cycloheptene (Si-TCH) derivatives are described. 3 complexes of trans-cycloheptene (TCH) and trans-1-sila-4-cycloheptene (Si-TCH) derivatives is described. A low temperature flow photoreactor was designed to enable the synthesis of carbocyclic TCH derivatives due to their thermal sensitivity in the absence of metal coordination. Unlike the free carbocycles, TCH\u00b7AgNO3 complexes can be handled at rt and stored for weeks in the freezer (\u201318 \u00b0C). Si-TCH\u00b7AgNO3 complexes are especially robust, and are bench stable for days at rt, and for months in the freezer. X-ray crystallography was used to characterize a Si-TCH\u00b7AgNO3 complex for the first time. With decomplexation of AgNO3in situ, metal-free TCO and Si-TCH derivatives can engage in a range of cycloaddition reactions as well as dihydroxylation reactions. Computation was used to predict that Si-TCH would engage in bioorthogonal reactions that are more rapid than the most reactive trans-cyclooctenes. Metal-free Si-TCH derivatives were shown to display good stability in solution, and to engage in the fastest bioorthogonal reaction reported to date (k2 1.14 \u00d7 107 M\u20131 s\u20131 in 9\u2009:\u20091 H2O\u2009:\u2009MeOH). Utility in bioorthogonal protein labeling in live cells is described, including labeling of GFP with an unnatural tetrazine-containing amino acid. The reactivity and specificity of the Si-TCH reagents with tetrazines in live mammalian cells was also evaluated using the HaloTag platform. The cell labeling experiments show that Si-TCH derivatives are best suited as probe molecules in the cellular environment.A photochemical synthesis of AgNO The unique reactivity of trans-cycloalkenes has produced an impressive collection of applications in synthesis, including reactions with dienes,trans-cycloalkenes can serve as excellent ligands for transition metals. In the field of bioorthogonal chemistry,trans-cycloalkenes hold special significance due to their particularly fast kinetics in cycloaddition reactions.trans-cyclooctene, the chemistry of the homolog trans-cycloheptene is less explored. trans-Cycloheptene was first trapped with diphenylisobenzofuran by Corey and Winter from trans-1,2-cycloheptenethionocarbonate through treatment with P(OMe)3.cis/trans equilibria could be driven by selective addition reactions of trans-cycloalkenes.For nearly seventy years,trans-Cycloheptene was first spectroscopically characterized by Inoue via singlet sensitized photoisomerization of cis-cycloheptene at \u201335 \u00b0C.trans-cyclooctene, which is stable at room temperature, trans-cycloheptene undergoes rapid isomerization under ambient conditions via a proposed \u2018interrupted dimerization\u2019 mechanism.30trans-Cycloheptene has also been prepared via ligand exchange from a trans-cycloheptene\u00b7CuOTf complex.trans-cycloheptene and trans-cycloheptenone derivatives are also known to be thermally unstable at ambient temperature, but can be trapped in situ.trans-cycloheptene is thermally labile, it has been demonstrated in several studies that metal complexes can be isolated. CuOTf has been proposed to catalyze photodimerization reactions of cyclic olefins via photoinduced cis\u2013trans isomerization,trans-cycloheptene\u00b7CuOTf complex has been prepared through irradiation of cis-cycloheptene\u00b7CuOTf, but a yield for the process was not reported.2 complex of trans-cycloheptene has been prepared by irradiation of the corresponding ethylene complex in the presence of cis-cycloheptene under singlet sensitized conditions.4 complexes of 3-methoxy-trans-cycloheptene and 6-methoxy-(Z),4(E)-cycloheptadiene.4\u00b73-methoxy-trans-cycloheptene complex was combined with a number of dienes to give the products of metal decomplexation and [4 + 2] cycloaddition.While the parent trans-cycloalkenes.E)-1,1,3,3,6,6-hexamethyl-1-sila-4-cycloheptene was synthesized, resolved, and characterized crystallographically.trans-alkene. Recent studies by Woerpeltrans-cycloalkene derivatives in synthesis. Woerpel has elegantly developed a general method for the preparation of trans-oxasilacycloheptenes\u2014seven membered rings that contain trans-alkenes and siloxy bonds in the backbone.Because C\u2013Si bonds are long, the inclusion of silicon into the cyclic backbone can alleviate olefinic strain and impart stability to trans-cycloheptene derivatives. In 1980, Jendralla showed that silver complexes of 3-methoxy-trans-cycloheptene are isolable, and can reversibly dissociate and in unspecified yields undergo cycloaddition reactions.trans-oxasilacycloheptenes, and recently has reported the Diels\u2013Alder reactions of trans-oxasilacycloheptenes with furan and tetrazine derivatives.trans-cyclooctene (\u2018s-TCO\u2019) derivative.s-tetrazine in benzene at rt in less than 10 min and in 90% NMR yield.48There has been little investigation into the reaction chemistry of trans-cyclooctene derivatives, whereby selective complexation with AgNO3 is used to drive the formation of trans-isomer from cis-cyclooctene.trans-cycloheptene (TCH) and trans-1-sila-4-cycloheptene (Si-TCH) derivatives via flow photochemical synthesis. The derivatives described are especially stable as their AgNO3 metal complexes, which can be stored neat or in solution for long periods. With decomplexation of AgNO3in situ, metal-free TCH and Si-TCH derivatives can engage in a range of cycloaddition reactions as well as dihydroxylation reactions. Unlike the carbocycles, Si-TCH derivatives display good stability in solution and are shown to engage in the fastest bioorthogonal reaction reported to date. Decomplexation of AgNO3 can be carried out in situ directly in cell media for bioorthogonal protein labeling in live cells.Our group has described a closed-loop flow reactor for the synthesis of trans-cyclooctene derivatives, the trans-cycloalkene is first scavenged on AgNO3/SiO2 and then liberated through treatment with aqueous or methanolic ammonia.cis-isomers.trans-cyclooctenes could be enhanced by storing the cycloalkenes as their AgNO3 complexes, and that the free alkenes could be liberated in situ through treatment with NaCl in aqueous solution or cell media.For the photochemical synthesis of 3 derivatives were carried out at rt using the previously described flow-photoisomerization apparatus,3 complexes were directly isolated from SiO2 without Ag-decomplexation. The metal complexes that were obtained were stable in neat form for >1 month in the freezer. However, it was necessary to alter our reactor design for the synthesis of carbocyclic trans-cycloheptenes due to their thermal lability was positioned before the photowell, and the photoisomerization was conducted in a coil of optically transparent FEP tubing.3/SiO2. In our standard setup, an inline thermometer was included to measure the temperature for the flowing mixture either before or just after the UV lamp. The temperature was measured as 0 \u00b0C before entering the Rayonet photoreactor, and as 20 \u00b0C after exiting the photoreactor. With this apparatus, TCH\u00b7AgNO3 complexes were eluted from the column, and isolated as semisolids that are moderately stable at rt but stable for weeks in the freezer.Photoisomerizations to form Si-TCH\u00b7AgNOlability . As withtrans-cycloheptene (1a) and trans-5-hydroxymethylcycloheptene (1b) were prepared in 53% and 64% yields, respectively. These TCH\u00b7AgNO3 complexes are stable enough to handle on the bench for modest periods (hours), and to longer-term storage in the freezer (\u201318 \u00b0C). NMR monitoring showed 90% fidelity for a CD3OD solution of 1a after 10 days storage in freezer (\u201318 \u00b0C), and 92% fidelity for a CD3OD solution of 1a after 10 hours at rt on the bench.The scope of TCH and Si-TCH synthesis is shown in 3OD solution of 2a after 8 days at rt, and 96% fidelity for 2a after storage for 1 month in the freezer . The photoisomerization method could be used to produce diphenyl (2a) or dialkyl (2b\u2013g) substituted silacycles. Cyano (2b) and hydroxyl (2c\u2013e) groups were tolerated, as were NHS ester (2f) and chloroalkane (2g) groups that could be used to enable conjugation to fluorophores and HaloTag3 and Si-TCH\u00b7AgNO3 complexes were isolated as semisolids that contained 20\u201330% free AgNO3. The isolated yields were corrected by measuring the 1H NMR against an internal standard.The silver complexes of Si-TCH are much more stable. NMR monitoring showed 93% fidelity for a CDtrans-cyclooctene coordinates with AgNO3 as a 1\u2009:\u20091 complex.2a were grown from ethyl acetate/methanol. Selected bond lengths and angles are displayed in i) nitrate complex of the equatorial diastereomer of 5-hydroxy-trans-cyclooctene 3 scale\" fill=\"currentColor\" stroke=\"none\">C\u2013C dihedral angle for 3 (136.7\u00b0) is smaller than metal-free TCO 4 (139.1\u00b0). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C dihedral angle for 2a (126.3\u00b0) was smaller than that of metal free Si-trans-cycloheptene 5 (130.9\u00b0),6 (126.1 \u00b0C)i) alkene complexes, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond length for the Ag(i) complexes was very similar to that of the metal-free complexes 4\u20136 (1.331\u20131.335 \u00c5).Previously, a crystal structure showed that octene 3 . Here, t4OH or aq. NaCl, followed by extraction with organic solvent. For example, silver complex 2a upon treatment with aq. NH4OH was extracted with C6D6 to give a solution of Si-TCH 7a (98% trans isomer). Consistent with previous reports on a biomolecular mechanism for TCH isomerization,cis-isomer of 7a was observed when 7a was concentrated to dryness on the rotovap. However, 7a displayed high stability when maintained in solution, with only 8% isomerization observed for a 100 mM solution of 7a that was stored for 24 hours at room temperature, and <5% isomerization for a similar solution that was stored for 24 hours in a freezer (\u201320 \u00b0C).Silver-free Si-TCH compounds could be prepared by treating their corresponding silver nitrate complexes with an excess of aq. NHi)-complex 2d could also be freed of metal to give alkene 7d as a mixture of diastereomers scale\" fill=\"currentColor\" stroke=\"none\">C double bond stretch of 7d at 1624 cm\u20131 is shifted to 1559 cm\u20131 for the Ag(i) complex 2d. This 65 cm\u20131 shift is consistent both in magnitude and direction for a Ag(i) alkene complex.i)-complexation leads to signature shifts of alkene resonances in both the 1H and 13C NMR spectra with dichloroketene, benzylazide or diazomethane only returned unreacted starting material. An X-ray structure was obtained for the dichloroketene adduct 13 . As discussed below, this fluorophore conjugate finds utility for bioorthogonal labeling in live cells. We also demonstrated that the equatorial allylic alcohol 17(eq), derived from Ag-complex 2e, could be elaborated to the carbamate 18 through treatment with benzylisocyanate level, and compared to previous calculations on trans-cyclooctene and s-TCO 20. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C dihedral angle for 19 (128.8\u00b0) is smaller than that for trans-cyclooctene (137.7\u00b0) or 20 (131.9\u00b0). M06L/6-311+G calculations were also carried out to compare the Diels\u2013Alder reactivity of Si-TCH 19 to trans-cyclooctene and s-TCO 20 9.91 kcal mol\u20131 and \u0394H\u2021 8.87 kcal mol\u20131. The barrier is significantly lower than that of trans-cyclooctene with 3,6-diphenyl-s-tetrazine \u20133.99 kcal mol\u20131, \u0394\u0394H\u2021 4.06 kcal mol\u20131). The barrier is also lower than that calculated for s-TCO 20 \u20130.59 kcal mol\u20131, \u0394\u0394H\u2021 \u20130.72 kcal mol\u20131). The computations prompted us to conduct experimental investigations into the utilization of Si-TCH complexes for applications in bioorthogonal chemistry.Anticipating that Si-TCH compounds may be useful in bioorthogonal chemistry, computation was used to study the structure and Diels\u2013Alder reactivity of Si-TCH 19 . We comps-TCO 20 . These cs-tetrazine in MeOH at 25 \u00b0C with s-TCO,trans-cyclooctene,\u20131 s\u20131, respectively. Si-TCH 7c was liberated from AgNO3, and in agreement with computational prediction, was found to react with diphenyl-s-tetrazine with a rate constant of 4360 (+/\u2013430) M\u20131 s\u20131\u20141.4 times faster than sTCO, 8.4 times faster than dTCO, and 228 times faster than trans-cyclooctene itself M\u20131 s\u20131. This is the fastest rate constant reported to date for a bioorthogonal reaction.Under aqueous conditions, tetrazine ligations are accelerated due to the hydrophobic effect. We previously had studied the reactions of s-TCO, d-TCO and in vitro and in vivo cycloaddition of SiTCH and a green fluorescent protein with an unnatural tetrazine-containing amino acid , encoded via the procedure of Mehl and coworkers.s-tetrazin-3-yl)phenylalanine was site-specifically introduced into a C-terminally hexahistidine-tagged GFP (sfGFP-150TAG-His6) via orthogonal translation using the evolved aminoacyl-tRNA synthetase MjRS/tRNACUA pair. Co-expression of these components in E. coli resulted in the amino acid-dependent synthesis of full-length recombinant GFP-Tet of E. coli overexpressing GFP-Tet by measuring the increase in whole-cell fluorescence upon addition of 7c. At room temperature, a second-order rate constant of 155\u2009000 \u00b1 20\u2009000 M\u20131 s\u20131 was measured for the in vivo reaction, which is 62% as rapid as the in vitro ligation. The modest reduction in rate is in line with previous observations with TCO-based dienophiles.7c is capable of crossing the bacterial cell membrane and engaging in rapid, high yielding conjugation inside a living cell.Although BS at rt . The reaBS at rt , and is trans-cycloalkene\u2013AgNO3-complexes liberate AgNO3 immediately in cell media due to the high NaCl content, and perform identically to their metal-free analogs in cell labeling experiments.AgSiTCH-Halo) and methyl-tetrazine and used these clickable HaloTag ligands to covalently label HaloTag protein expressed in HEK293T cells with the clickable tag. In a competitive pulse-chase experiment, it was shown that 10 \u03bcM of these HaloTag ligands completely blocked incorporation of BODIPY-Halo substrate for different times (2\u201390 min) . The rea\u201390 min) , and in-SiTCH-Halo with MeTz-BODIPY was complete within 15 minutes completely isomerizes in 2 h at 22 \u00b0C in CD3OD with mercaptoethanol (30 mM), whereas as control sample without thiol was >98% stable under these conditions. At \u201317 \u00b0C, 7b isomerizes more slowly in the presence of 30 mM mercaptoethanol, with 47% isomerization after 24 h. By comparison, the trans-cyclooctenes d-TCO, s-TCO, and oxo-TCO are much more stable toward thiol promoted isomerization. In CD3OD with mercaptoethanol (30 mM) at room temperature, s-TCO (30 mM) isomerized only after an 8 hour induction period, with complete conversion to the cis-isomer after 4 additional hours.3OD over a 22 hour period at room temperature.72Compared to the periods . By contprotocol .56 SpeciTogether, the labeling experiments in bacteria and HEK293T cells show that SiTCH derivatives can serve as useful probe molecules in the cellular environment, as the unprecedented speed of the bioorthogonal reactions of SiTCH are much more rapid than competing deactivation pathways. However, the utility of SiTCH derivatives as protein tagging molecules, where extended incubation in the cellular environment takes place prior to bioorthogonal reactivity, appears much more limited in utility plausibly due to alkene isomerization in the cellular environment.3 complexes of trans-cycloheptene and trans-1-sila-4-cycloheptene derivatives have been prepared via a flow photochemical synthesis, using a new low temperature flow photoreactor to enable the synthesis of carbocyclic TCH derivatives. TCH\u00b7AgNO3 complexes can be handled for brief periods at rt and stored for weeks in the freezer (\u201318 \u00b0C). Si-TCH\u00b7AgNO3 complexes are especially stable, and can be stored on the bench stable for >1 week at rt, and for months in the freezer. X-ray crystallography was used to characterize a Si-TCH\u00b7AgNO3 complex for the first time. With decomplexation of AgNO3in situ, metal-free TCO and Si-TCH derivatives can engage in a range of cycloaddition reactions as well as dihydroxylation reactions. Computation predicted that Si-TCH would display faster bioorthogonal reactions toward tetrazines than even the most reactive trans-cyclooctenes. Metal-free Si-TCH derivatives were shown to display good stability in solution, and to engage in the fastest bioorthogonal reaction reported to date (k2 1.14 \u00d7 107 M\u20131 s\u20131 in 9\u2009:\u20091 H2O\u2009:\u2009MeOH). Utility in bioorthogonal protein labeling in live cells is described, including labeling of GFP with an unnatrual tetrazine-containing amino acid. The reactivity and specificity of the Si-TCH reagents with tetrazines in live mammalian cells was also evaluated using the HaloTag platform. The cell labeling experiments show that Si-TCH derivatives are suitable as highly reactive probe molecules in the cellular environment.In conclusion, AgNOThere are no conflicts to declare.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Formal addition of diazomethane's terminal nitrogen atom to the 9,10-positions of anthracene yields H2CN2A . 2CN2A . The synthesis of this hydrazone is reported from Carpino's hydrazine H2N2A through treatment with paraformaldehyde. Compound 1 has been found to be an easy-to-handle solid that does not exhibit dangerous heat or shock sensitivity. Effective umpolung of the diazomethane unit imbues 1 with electrophilicity at the methylene carbon center. Its reactivity with nucleophiles such as H2CPPh3 and N-heterocyclic carbenes is exploited for C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond formation with elimination of dinitrogen and anthracene. Similarly, 1 is demonstrated to deliver methylene to a nucleophilic singlet d2 transition metal center, W(ODipp)4 (2), to generate the robust methylidene complex . This behavior is contrasted with that of the Wittig reagent H2CPPh3, a more traditional and Br\u00f8nsted basic methylene source that upon exposure to 2 contrastingly forms the methylidyne salt [MePPh3].Formal addition of diazomethane's terminal nitrogen atom to the 9,10-positions of anthracene yields H An initial survey of the reactivity patterns of 1 has revealed it not to be a simple substitute for diazomethane, instead characterizing it as a unique electrophilic methylene source. Its electrophilicity differentiates 1 from common metal-free methylene transfer reagents such as diazomethane and methylene triphenylphosphorane.Diazomethane is infamous for the dangers associated with its use.1 proceeded from Carpino's hydrazine H2N2A upon paraformaldehyde treatment in a biphasic diethyl ether\u2013water mixture,11Synthesis of hydrazone 1 was found to be an air-stable and crystalline solid, easily manipulable and displaying no propensity for detonation upon heating or shock. The solid was found to be volatile by thermogravimetric analysis (TGA), which showed gradual sample evaporation up to 120 \u00b0C without any discrete mass-loss events that would be expected from its fragmentation into diazomethane and anthracene. Within a sealed capillary, 1 melted without explosion (116\u2013119 \u00b0C). After heating the melt to 140 \u00b0C, NMR spectroscopic analysis of the resolidified solid showed 74% recovery of 1 with 26% anthracene production. Its behavior in solution was similar, evincing only slow fragmentation into anthracene at temperatures greater than 120 \u00b0C. The volatility of this compound foiled attempts at analysis of its thermal behavior by molecular beam mass spectrometry (MBMS), limiting our ability to comment on the fragments directly produced by its thermal fragmentation.Hydrazone 1 to pose a low explosion risk, we were encouraged to proceed to test its reactivity as a methylene synthon. Our initial investigations rapidly uncovered contrasting reactivity patterns vis-\u00e0-vis those characteristic of diazomethane. For example, methylation of carboxylic acids, a hallmark of diazomethane reactivity,1.Having established 1 did not demonstrate nucleophilicity. Such behavior is not unexpected, as the \u03c0CN is known to be polarized away from the carbon center, although less so than an imine \u03c0CN or a ketone \u03c0CO bond.1 should be expected to exhibit moderate electrophilicity at its methylene carbon. This would effectively induce umpolung of the diazomethane unit as diazomethane generally reacts as a carbon nucleophile.15Hydrazones are known to be carbon ambiphiles;1 and H2CPPh3. Combination of these two reagents in benzene-d6 yielded ethylene in 21% yield over 12 h in concert with anthracene, triphenylphosphine, and, presumably, dinitrogen. The reaction was found to produce several unidentified byproducts by NMR spectroscopy, explaining the low yield of ethylene; however, isotopic labelling of the ylide led to H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t13CH2 from 1 and H213CPPh3, and H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCD2 from 1 and D2CPPh3, confirming ethylene formation through the unification of the electro- and nucleophilic methylene units. Although the yield was low, this mode of reactivity was instructive for our further studies.The predicted reversal of philicity was initially confirmed by successful methylene transfer in the reaction between 1 lent itself well to the synthesis of N-heterocyclic olefins from N-heterocyclic carbenes (NHCs).6 solution, 1 reacted with nucleophilic IPr imidazol-2-ylidene) to yield the corresponding olefin in 70% yield after 13 h at 80 \u00b0C.N,N\u2032-diamidocarbene (\u201cDAC\u201d) was found to react in essentially quantitative yield to form a new C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond over 24 h at 22 \u00b0C. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC moiety.1 with triphenylphosphine or tricyclohexylphosphine has not yielded the analogous yieldes, suggesting a modest Lewis acidity at the carbon center of 1.The electrophilicity of 1 and diazomethane thus encouraged us to attempt the use of 1 in methylidene complex synthesis to see if engagement of the terminal nitrogen in bonding to anthracene subdues deleterious alternate reaction pathways.It is rare for diazomethane to be used in transition metal chemistry for the synthesis of a stable methylidene complex.4] 2 transition metal complex well poised to behave as a methylene acceptor.2 is synthetically easy to access, and its square-planar geometry features a nucleophilic lone pair of electrons housed in a metal-centered dz2-like orbital, analogously to related tantalum and molybdenum singlet d2 species.2 with excess 1 gave facile formation of the anticipated methylidene complex after mild heating in benzene to 55 \u00b0C for 35 h for 35 h . Charact2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2] (\u03c4 = 0.48), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bondvi) methylidenes.2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2] was not found to react productively with ethylene or 1-hexene upon heating to 70 \u00b0C in benzene-d6 for 18 h, confirmed by a lack of isotopic migration from to the olefins.2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2] also did not react with mesitaldehyde or 4,4\u2032-dimethylbenzophenone to form and the corresponding olefins. Despite this, is notable as an example of a methylidene complex with aryloxides as the exclusive supporting ligands. As such, it is an interesting structural model for methylidene complexes supported by silica or alumina surfaces implicated in alkane or olefin metathesis.Crystallization from pentane at \u201335 \u00b0C overnight enabled an X-ray diffraction study of [g>CH2] , left th1 was particularly satisfying after discovery of the contrasting behavior of H2CPPh3, a known reagent for CH2 delivery to transition metal centers.2 with H2CPPh3 (1 equiv.) in THF at 25 \u00b0C rapidly consumed 50% of 2 and formed the methylidyne salt [MePPh3]. Doubling the amount of H2CPPh3 gave total consumption of 2 and provided [MePPh3] in 49% isolated yield scale\" fill=\"currentColor\" stroke=\"none\">CH2] formation, indicating competitive deprotonation of intermediate by Br\u00f8nsted basic H2CPPh3. Such acid-base chemistry is postulated to play a critical role in the formation of surface-bound alkylidenes and alkylidynes for alkane and olefin metathesis,2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2] serves also as an interesting reactivity model for alkylidyne synthesis mediated through proton transfer. This was corroborated by independent deprotonation of with H2CPPh3, and highlights the utility of 1 as a weakly Br\u00f8nsted basic source of methylene. Protonation of [MePPh3] using lutidinium triflate presents a complementary route to .The reactivity of ed yield . Variati3] revealed a W\u00b7\u00b7\u00b7C interatomic distance of 1.749(1) \u00c5 and a square pyramidal (\u03c4 = 0.21) coordination geometry about tungsten. A search of the CSD revealed this to be the first catalogued example of a structurally characterized metal methylidyne in an all-oxygen ligand environment, and the first catalogued example of a tungsten(vi) methylidyne complex.An X-ray crystallographic study of [MePPh1 can be further exploited in their syntheses. Compound 1 has also shown promise in formation of new C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds with H2CPPh3 and NHCs, and may find use in construction of terminal olefins.As interest in metal methylidene species is rapidly growing both in homogeneous and heterogeneous catalysis,There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We herein present a simple methodology to systematically expand the scope of maleimide-based dyes and also provide an insight into the relationship between substitution pattern and optical properties. A series of maleimide derivatives were systematically designed and synthesized with tunable fluorescent properties. The facile modifications herein provide a simple methodology to expand the scope of maleimide-based dyes and also provide insight into the relationship between substitution pattern and optical properties. The development of novel organic fluorophores is of great interest in the areas of biological labels and probes,DTM)ABM),2 or N2.33Unsubstituted maleimides have been extensively reported as effective fluorescence quenchers through direct conjugation to fluorophores.Despite the recent advances in this field, there has been little work on varying the maleimide structures and studying the subsequent impact on their fluorescence. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups and the group on the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC moiety act as the electron acceptor and donor respectively. Our initial strategy began with reacting three different pro-fluorescent precursors: dibromo (DBM), dichloro (DCM) and diiodo (DIM) maleimide to aminobromomaleimide (ABM), through single substitution, with an amine, has been previously reported by our group.21The design concept relies on the typical electron donor and acceptor mechanism in maleimide-based fluorophores where the Cde 1a\u2013c, . The conDCMs and DIMs). The reaction resulted in the formation of a singly substituted product for all precursors. The optical properties of these three different amino substituted halogeno maleimides (2a\u2013c) were investigated. In diethyl ether, the three compounds (2a\u2013c) exhibited two similar absorption peaks around 238 nm and 370 nm assigned to an n\u2013\u03c0* and a \u03c0\u2013\u03c0* transition, respectively and aminobromomaleimide showed similar green emission ca. 475 nm while the aminoiodomaleimide produced a slightly red shifted emission (ca. 487 nm). The fluorescence quantum yields (\u03a6f) of these products were measured using quinine sulfate as a reference, to establish any effect of the halogen.\u03a6f decreased from Cl through Br to I in diethyl ether and compared this to the analagous chloro derivative (2d).\u03a6f of 2d was 42% in diethyl ether and 65% in cyclohexane, which is the highest \u03a6f of all reported amino halogeno maleimides.Based on this method, we expanded the scope by reacting the amine with other halogeno maleimides exhibited a similar change in fluorescent emission across the solvent series and the emission wavelengths were shifted to higher wavelengths. This is consistent with previous work which shows that the hydrogen bonding between protic solvents and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group in maleimides causes quenching effects through electron driven proton transfer from the solvent to the fluorophore.\u03a6f was observed, likely as a consequence of the suppression of twisted intramolecular changer transfer (TICT) in the maleimide rings.9The solvatofluorochromic properties were further investigated in solvents across a wide polarity range. All compounds . Following the route of Booker-Milburn et al., sodium alkoxide was used to catalyze a substitution reaction with DCM and DBM and a series of alcohols.in situ formation of the products, 3a\u2013f, proceeded successfully for both aryl and alkyl alcohols at room temperature.Looking at these results it was clear that the optical properties are closely related to the electronegativity of the halogen substituents, with increased electronegativity correlating with increased 3a\u2013d, the typical \u03c0\u2013\u03c0* transition peak shifted from ca. 360 nm to ca. 335 nm, while also reducing in intensity (2b) to an ethoxy (3b) group also lead to a dramatic decrease in \u03a6f from 30% to 10% (in diethyl ether). This indicates that a strong electron donating group on the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond is critical in obtaining a high fluorescence intensity. Looking at the series in more detail, both the OCM and OBM substituted ethoxy (3a\u2013b) and benzyloxy (3c\u2013d) maleimides showed similar emission wavelengths, whereas no emission was observed for the phenoxy (3e\u2013f) derivatives . As the optical properties are closely related to modifications made to this series of singly substituted maleimides, it was hypothesized that more remarkable changes may be realized by exploring disubstituted maleimides. Previously, it has been demonstrated that DBMs were capable of undergoing an efficient addition-elimination reaction with thiols resulting in a disubstituted product using thiol groups.ABM scaffold using microwave irradiation at 50 \u00b0C.ABMs altered the electronic nature of the neighbouring site, such that a second amine addition does not occur at room temperature. Conversely, we were inspired by the fast and efficient double addition elimination reaction with thiols and hence attempted to introduce a second thiol group on an ABM. A similar compound has been reported to date, by Naka et al., where thiophenol was able to undergo reaction with an aniline substituted maleimide. However, due to the aromatic nature of the aniline, almost no fluorescence was observed in solution.ATM) were synthesized and their optical properties explored. ATMs were generally synthesized from ABMs through the addition of 1 equivalent of thiol and sodium hydroxide at 80 \u00b0C in DMF. Following the successful synthesis of a series of ten ATMs (4a\u2013j), the optical properties were characterized. The excitation wavelength of the ATM compounds remained in the 360\u2013380 nm range (in diethyl ether) similar to ABMs, while the emission shifted to higher wavelengths compared with previous substituted maleimides, which could make them useful in F\u00f6rster Resonance Energy Transfer (FRET) based applications. The solvafluorochromic properties of ATM (4h) was compared with ABM (2e) in eight common solvents , the emissions of ATM (4h) were higher in wavelength (green to yellow range). Similar with ABMs, fluorescence quenching of ATM was observed in protic solvents which is attributed to hydrogen bonding between the protic solvent and the carbonyl.In the absorbance spectra of ntensity . MeanwhiATMs with varying thiol substituents (4a\u2013d) were compared. The emission of two alkyl thiol substituted compounds (4a and 4b) showed a relatively high emission wavelength (ca. 560 nm) which approached the red region of the spectrum , the emission maxima blue-shifted with an unexpected increase in quantum yield. Furthermore, strong emission was also observed in the solid state of thiophenol functionalized ATM (4h) compared to their analogous ABM (2e). Comparing the absolute \u03a6f in solid states, 4h processes a higher \u03a6f (4h 8% versus2e 1%) and longer fluorescence lifetime and dichloromethane (good solvent). The fluorescence of 4h gradually increased with the addition of non-solvent while aminomaleimide 2e did not present the same trend showed an increased \u03a6f compared with compounds with methyl at R1 (4a\u2013g). As expected, the direct conjugation of an aniline group at the R2 position (4g) also caused dramatic quenching of the fluorescence (\u03a6f < 0.1%), consistent with previous reported aminobromomaleimides.ATMs originates from the aminomaleimide moiety analogous to ABMs, in which the amino group on C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond acts as the donor moiety in a donor\u2013acceptor skeleton.Following the study on the effect of thiol groups in the R3 position, substituents on the R1 and R2 positions were also found to affect the optical properties significantly /6-311G level using time-dependent density functional theory scale\" fill=\"currentColor\" stroke=\"none\">C bond positively affect fluorescence. Building upon this work and further exploring the relationship between the structure of maleimides and their optical properties is essential for full understanding of the fluorescence mechanism. This, in turn, will aid the design of future maleimide fluorophores with small size, multi-functionalization and high fluorescence efficiency for biological and chemical sensing applications.In conclusion, we successfully synthesized a library of maleimide fluorophores with remarkable fluorescent properties such as tunable emissions among the visible colour range (blue to yellow), high fluorescence quantum yields (up to 64%) and solvafluorochromism. Significantly, we investigated the effect on optical properties when altering the halogen group and the donor groups . The fluorescence results provide evidence of the previously hypothesized push\u2013pull model and computational results further confirmed that smaller charge differences on the CThe authors thank the University of Warwick, the ERC (grant no. 615142), Ministerio de Econom\u00eda y Competitividad (MINECO) of Spain (project CTQ2016-80375-P) and EPSRC for financial support. The authors acknowledge the computational resources and technical and human support provided by DIPC.There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Molecular cage-bridged gold nanoclusters with well-defined hotspots were demonstrated as novel plasmon-assisted nanoreactors. Creating well-defined plasmonic hotspots with enormous field enhancements as well as the capability of selectively trapping targeted molecules into hotspots is of critical importance and a prerequisite for numerous plasmon-assisted applications, but it represents a great challenge. In this work, a robust molecular cage decorated with thioether moieties at the periphery was designed and synthesized. By using the synthesized cage as a linker, a series of molecular cage-bridged plasmonic structures with well-defined nanogaps (hotspots) were fabricated in an efficient and controllable fashion. It was found both experimentally and theoretically that the nanogaps of about 1.2 nm created by the molecular cage in the resultant plasmonic structures led to a strong plasmon coupling, thus inducing great field enhancement inside the nanogaps. More importantly, the embedded molecular cages endowed the formed hotspots with the capability of selectively trapping targeted molecules, offering huge opportunities for many emergent applications. As a demonstration, the hotspots constructed were used as a unique nanoreactor, and under mild conditions two types of plasmon-driven chemical transformation were successfully performed. All the results clearly indicate that the integration of the host\u2013guest chemistry of the molecular cage with the plasmon-coupling effect of metal particles afforded a new class of plasmonic structures, showing great potential for facilitating a broad variety of plasmon-based applications. In recent years, it was elucidated that the enormous field enhancement could also lead to the efficient generation of hot charge carriers,Noble metal nanoparticles (NPs) support unique localized surface plasmon resonances (LSPRs) through coherent oscillations of free electrons in metallic nanostructures under light illumination, and a strong electromagnetic field is induced in the close vicinity of the metal surface.et al., organic thiol-linkers were used to direct the organization of NPs.et al. have prepared well-organized NP ensembles with complex and hierarchical nanostructures via DNA.5Generally, top-down and bottom-up strategies are employed for creating or engineering hotspot nanostructures.2L4 metal\u2013organic molecular cage decorated with thioether moieties at the periphery under mild conditions as well as the cycloaddition from 4-ethynylphenol (4-EP) and 4-azido-phenol (4-AP) without catalysts were successfully realized. All the results indicate that the molecular cage-bridged plasmonic clusters described are new plasmonic nanostructures with advanced functionalities.In this work, we describe a new Meriphery . We founL was synthesized from 2,6-dibromoisonicotinic acid (Scheme S1L (2 equiv.) and [Pd(CH3CN)4](X)2 (1 equiv.) at room temperature (X= BF4\u2013 or OTf\u2013), the colorless cage single crystal was achieved after three days with good yields of 79\u201393% than the free ligand L (D = 1.9 \u00d7 10\u20139 m2 s\u20131), which is indicative of the formation of larger chemical species n)(4\u2013]n+ (n = 2\u20134) platinum(ii) (DCTP) and 1,4-phenyldiamine hydrochloride (PDA) using 1H NMR, UV-Vis and ESI-MS of the suspension of CP in the CD3CN solution of the cage. As shown in Fig. S3,\u03b4 = 0.06 ppm) and a broadening of the internal proton Ha of the cage were detected in the NMR spectrum of the mixed solution, indicating that the guest CP was trapped in the molecular cage. Indeed, the ESI-MS result 2]4+ complex with an intense peak at m/z = 544.28, confirming that two cisplatin molecules were trapped in the cage. In fact, the same encapsulation behavior of the CP was also observed in a similar molecular cage only without the thioether moieties at the periphery.8The host\u2013guest behavior of the synthesized molecular cage was studied using five guest molecules with different size, shape and charge, including CP, 4-NP, HQ, t Fig. S4 shows th2L4 cage was examined using 1H NMR, ESI-MS and UV-Vis methods. Due to the formation of hydrogen bonding between the guest and the pyridine moieties of the cage, the protons (Ha and Hb) of the cage were most shifted upon HQ and 4-NP encapsulation @(4-NP)2]3+ with the peak at m/z = 648.8 in the ESI-MS spectrum was also detected for the case of 4-NP n@guest]n)+(4\u2013 (n = 1\u20133) peaks along with the peaks due to fragmentation of the cage under a certain spray voltage. In fact, a similar phenomenon was also observed in the literature.For the case of guest HQ and 4-NP, the trapping ability of the PdQ Fig. S8. Similar Fig. S14. In our 2L4(BF4)n) absorption at 525 nm. As shown in The assembly of Au NPs with the aid of the Pdca. 1.2 nm scale\" fill=\"currentColor\" stroke=\"none\">C, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bands or NaOH solution (pH = 10), the fabricated substrate structure gradually diminished, which was indicative of the instability of the embedded cages in acidic and alkaline solutions for a given time (2 h), and after being thoroughly washed with DMSO and ethanol the substrates were checked using the SERS technique. \u20131 (asymmetric and symmetric stretching doublet vibrations \u03bdPt-NH3) appeared in the SERS spectrum . 4-NP was firstly chosen as a substrate to be converted into the product dihydroxylazobenzene (DHAB), as shown in \u20131 (\u2013NO2 \u03b3 stretching) was detected. After the irradiation of plasmonic clusters under laser irradiation (1 mW) at 633 nm for a given time, three bands associated with DHAB at \u03bd1 = 1481 cm\u20131, \u03bd2 = 1509 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">N\u2013stretching) and \u03bd3 = 1652 cm\u20131 (\u03bdCC stretching) appeared,\u03bd1 = 1400 cm\u20131 and \u03bd2 = 1453 cm\u20131 were detected,2 stretching remain unchanged and no bands associated with \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN stretching appeared over time, indicating that no reaction occurred in the molecular cages in the absence of gold nanoparticles under identical conditions. Similar results were also observed for the case of the cycloaddition reaction separation, but can also simultaneously impart the capability of trapping low affinity guests in the created hotspots, which could greatly expand the applications of plasmon-assisted chemistry. Ideally, the blank experiment of reactions will need to be performed with gold nanoparticles and cages that are not linked. In our system, however, due to the presence of thioether moieties at the periphery of the used cage, it is impossible or difficult to create an ideal system consisting of gold nanoparticles and cages that are not linked to perform the desired control experiments. Thus, in the future, we will perform a systematic study to address this issue through the synthesis of the same molecular cage without thioether or thiol groups.The unique capacity of plasmonic nanostructures to trap molecules that have a low affinity for metal surfaces and to selectively place the target molecules into hotspots could offer tremendous opportunities for numerous plasmon-assisted applications. Fig. S35. These rCreating well-defined plasmonic hotspots with enormous field enhancement as well as the capability of selectively trapping targeted molecules into hotspots is critical for numerous plasmon-assisted applications, but represents a great challenge. In this work, based on the assembly of Au NPs using a metal\u2013organic molecular cage as a linker, a series of cage-bridged plasmonic nanostructures were developed. It was found that the integration of host\u2013guest chemistry of the molecular cage with the plasmon coupling of Au NPs enables the formed plasmonic structures to address the mentioned challenges in terms of the formation of well-defined hotspots, the capture of molecules with lower affinities to the metal surface, the favourable molecule-accessibility, and the selective placement of target molecules in hotspots. The chosen applications above clearly highlight the significant value and tremendous potential of the cage-bridged plasmonic structures. Although one molecular cage was demonstrated in our case, the strategy described is generally applicable to other molecular cages for creating desired plasmonic nanostructures. As the described molecular cage is constructed through the coordination of organic linkers and metal ions, a careful selection of ligands and metal ions permits control of the geometric and host\u2013guest characteristics of the formed cages in a broader range. Such attractive attributes imply that the precise design and tuning of hotspots in plasmonic structures and their molecule-trapping properties are possible. Thus, our work opens a new avenue for engineering plasmonic architectures and affords a new class of plasmonic nanostructure, which could offer huge opportunities for numerous plasmon-based applications.C. W. planned and performed the experiments, analysed the data and wrote the paper. L. T., N. G. and K. Z. assisted in the experimental work. S. W. assisted in the theoretical simulation. W. Z., X. Y., and W. Z. discussed the results. G. L. guided the project and wrote the paper.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A \u03b2-diketiminato n-butylmagnesium complex is presented as a selective precatalyst for the reductive hydroboration of organic nitriles with pinacolborane (HBpin). n-butylmagnesium complex is presented as a selective precatalyst for the reductive hydroboration of organic nitriles with pinacolborane (HBpin). Stoichiometric reactivity studies indicate that catalytic turnover ensues through the generation of magnesium aldimido, aldimidoborate and borylamido intermediates, which are formed in a sequence of intramolecular nitrile insertion and inter- and intramolecular B\u2013H metathesis events. Kinetic studies highlight variations in mechanism for the catalytic dihydroboration of alkyl nitriles, aryl nitriles bearing electron withdrawing (Ar(EWG)CN) and aryl nitriles bearing electron donating (Ar(EDG)CN) substitution patterns. Kinetic isotope effects (KIEs) for catalysis performed with DBpin indicate that B\u2013H bond breaking and C\u2013H bond forming reactions are involved in the rate determining processes during the dihydroboration of alkyl nitriles and Ar(EDG)CN substrates, which display divergent first and second order rate dependences on [HBpin] respectively. In contrast, the hydroboration of Ar(EWG)CN substrates provides no KIE and HBpin is not implicated in the rate determining process during catalysis. Irrespective of these differences, a common mechanism is proposed in which the rate determining steps are deduced to vary through the establishment of several pre-equilibria, the relative positions of which are determined by the respective stabilities of the dimeric and monomeric magnesium aldimide and magnesium aldimidoborate intermediates as a result of adjustments to the basicity of the nitrile substrate. More generally, these observations indicate that homogeneous processes performed under heavier alkaline earth catalysis are likely to demonstrate previously unappreciated mechanistic diversity.A \u03b2-diketiminato Ca < Sr < Ba) whereas our own studies of the homoleptic bis(trimethylsilyl)amides [Ae{N(SiMe3)2}2]2 have evidenced more subtle kinetic dependences upon the identity and characteristics of the Ae2+ cation.Our own research has focussed on the development of a homogeneous catalytic chemistry for complexes, LAeX , derived from the heavier alkaline-earth elements.V) for the hydroboration of aldehydes and ketones,2 aminopyridines.F) requires the consumption of two molecules of HBpin and the intermediacy of an initial magnesium-bound imide (A), a borylated imine (B) as the product of initial B\u2013H/Mg\u2013N metathesis and an amide species (D) formed by formal Mg\u2013H insertion of the borylimine (B). The additional complexity introduced by the requirement for two-fold nitrogen functionalisation, thus, raises a number of issues regarding validity of such a stepwise process and the identity of other potential intermediates such as the borate species shown as C and E shown in vide infra).We have previously reported the use of the magnesium alkyl precatalyst , which is stable to both Schlenk-type redistribution equilibria and to chemical degradation under conditions of the catalysis, allows for an assessment of the effects of gradual substrate adjustment which suggests that every reaction must be treated on its merits.With these broader considerations in mind we now describe a magnesium-centred protocol for the hydroboration of organic nitriles with the unactivated borane reagent pinacolborane (HBpin). Our selection of a single \u03b2-diketiminato magnesium precatalyst amine product within 30 minutes. The clean formation of this new species was clearly apparent through the emergence of a (2H) triplet methylene resonance in the 1H NMR spectrum at \u03b4 3.42 ppm synchronous with a new singlet signal in the 11B NMR spectrum at \u03b4 29.5 ppm. In contrast an analogous reaction performed without the addition of V evidenced less than 5% consumption of the propionitrile substrate when heated at 60 \u00b0C for 16 hours. Encouraged by this result the conditions of the catalytic study were extended to the successful di-hydroboration of the range of alkyl and aryl nitriles summarised in An initial catalytic reaction using 10 mol% of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC-bound carbon centre of aliphatic nitriles wherein a 10-fold increase in reaction time is observed across the transition from propionitrile (entry 1) to iso-propylnitrile (entry 2) to tert-butylnitrile (entry 3). Aryl nitriles (entries 5\u201315) also provided clean reactions with no side products, but with markedly longer reaction times. Notably varied reaction times were also required with changing aryl substituent patterns. Although in the case of o-tolunitrile (entry 6) the slower reaction may again be attributed to an increase in substituent steric hindrance proximal to the reaction centre, any minor variability across the range of meta-and para-substituted arylnitriles is more realistically attributed to electronic adjustments across the pi-conjugated substrate or intermediate structure (vide infra). The identities of the products from this catalysis were confirmed by 1H, 11B and 13C NMR spectroscopy and a single crystal X-ray diffraction analysis performed upon the product (compound 1) isolated from the catalytic dihydroboration of propionitrile. The outcome of this latter experiment is shown in 3 hybridisation at the C1 carbon atom.In common with our earlier reports of the magnesium-catalysed hydroboration of aldehydes, ketones, imines and isonitriles,A\u2013E in t-BuCN was particularly informative due to the ready discrimination of the diagnostic singlet tert-butyl resonances in the 1H NMR spectra. We have earlier reported that V and HBpin react to form a magnesium hydride/borohydride species along with BuBpin within minutes at room temperature.t-BuCN provided complete C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN insertion into the magnesium hydride bond, which was clearly apparent after heating for 12 hours at 60 \u00b0C through the formation of a single new compound designated as an aldimide derivative analogous to the species A depicted in \u03b4 7.84 ppm assigned as the aldimide methine signal and a set of resonances associated with a single new \u03b2-diketiminate ligand environment in the 1H NMR spectrum (see Scheme S1m- and p-MeOC6H4CN. While both of the resultant compounds (2 and 3) again displayed characteristic 1H aldimide methine singlet resonances in their respective 1H NMR spectra, in these latter cases crystallisation from benzene solutions also provided samples of both compounds suitable for single crystal X-ray diffraction analysis. The results of these analyses are presented in 2 and 3 are the first magnesium aldimide complexes to be characterised in the solid state, their structures are otherwise analogous to a previously described calcium benzaldimide derivative supported by the identical \u03b2-diketiminate ligand.2 and 3 are dimeric with bridging Mg\u2013N\u2013Mg interactions provided by the aldimide ligands. Whereas the asymmetric unit of compound 2 comprises half of a dimer which straddles a crystallographic inversion centre, each half of the dimeric unit of compound 3 is unique. The gross features of both structures are, however, very similar wherein the magnesium centres are bridged by unsymmetrical Mg\u2013N\u2013Mg interactions. The magnesium to aldimide nitrogen bond lengths in 2 and 3 are shorter than the magnesium to amide contacts observed within topologically related dimeric magnesium benzylamide and pyrollidide derivatives [2.1251(16) and 2.117(2) \u00c5 respectively], both of which contain four-coordinate magnesium centres supported by the identical \u03b2-diketiminate ligand.3 to sp2 hybridisation at the bridging nitrogen centres in comparison to these previously described compounds is also reflected by the more obtuse Mg\u2013N\u2013Mg bond angles within compounds 2 and 3. As previously highlighted in Harder and co-workers' discussion of their calcium benzaldimide species,2 and 3 are virtually co-planar with the planes formed by the magnesium and the aldimide nitrogen and sp2 carbon centres. A similar in-plane conformation is also a common feature of dimeric diorganoaluminum benzaldimide species, 2, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2]2, to lie some 17 kcal mol\u20131 lower in energy than the alternative conformation in which the methylene unit is perpendicular to the Li2N2 plane.2 and 3 indicate that this stabilisation is further enhanced by delocalisation across the aryl substituents. Although such data should be treated with caution due to the possibility of solid-state crystal packing and dispersion effects, we ascribe the greater co-planarity of 2 in comparison to 3 to the mesomeric influence of the respectively stabilizing 3-methoxy- and destabilising 4-methoxyphenyl substituents. While only providing a minor solid-state effect, we suggest that modulation of aldimide resonance stabilisation is a significant factor during the magnesium-catalysed hydroboration of the range of aryl nitriles listed in vide infra).To provide further insight into the course of these successful catalytic reactions and the viability of intermediate species such as those shown as t-BuCN did not provide any initial evidence of B\u2013H/Mg\u2013N metathesis and production of a borylated imine derivative and more typical of four-coordinate boron.vide infra) allowed the isolation of the aldimidoborohydride derivative, compound 4, which was fully characterised by multinuclear NMR spectroscopy and a further single crystal X-ray experiment. The results of this latter analysis are presented in 4 provides the first crystallographic evidence for the intermediacy of borohydride intermediates during any magnesium-mediated hydroboration catalysis. The C(3)\u2013N(3) distance (1.226(2) \u00c5) of the formal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN double bond, although shorter than the aldimide C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN distances, comprising 2-coordinate nitrogen, within compounds 2 and 3 (2: 1.263(2); 3: 1.262(2), 1.271(2) \u00c5), is closely comparable to previously reported, albeit exclusively transition metal-coordinated, imine-derived borate anions.25Counter to the expectation illustrated in t 1JBH = 5 Hz and 4 in C6D6 were observed to undergo continued reaction on standing at room temperature over a period of 12 hours; clearly observed by monitoring of the time-resolved 1H NMR spectra through the disappearance of the downfield 1H aldimido proton signal and the simultaneous appearance of a new singlet resonance at \u03b4 3.35 ppm with an ultimate 2H intensity by integration. The corresponding 11B NMR spectra over this period evidenced a small downfield shift to \u03b4 6.3 ppm with loss of the doublet signal multiplicity. We suggest that these observations are a consequence of an intramolecular hydride shift resulting in reduction of the aldimide residue and production of a magnesium borylamide derivative directly analogous to species D shown in F in E in Samples of compound 2 and 3 provided no evidence for similar borate formation and provided resonances consistent with the persistence of the unreacted starting compounds. DOSY NMR analysis of these reactions also evidenced no change in the solution diffusion coefficient attributed to the dimeric species even with increasing temperature and the addition of further equivalents of HBpin. We attribute this observation to the additional conjugative stability provided to the dimeric unit by the co-planarity of the 3- and 4-methoxyphenyl substituents with the C\u2013N\u2013Mg linkage.Notably, analogous addition of one equivalent of HBpin to solutions of compounds 2\u20134 could themselves be utilised as precatalysts for the hydroboration of m- and p-MeOC6H4CN and t-BuCN respectively. These reactions provided conversions and reaction times that were broadly commensurate with the reactions initiated by V were isolated from the unstirred reaction mixture. Although this new species was insufficiently soluble to allow characterisation by solution-state NMR spectroscopy, a single crystal X-ray diffraction analysis revealed compound 5 as the unusual dinuclear magnesium complex shown in 5 are connected through bridging interactions provided by both oxygen atoms of a [H2Bpin]\u2013 anion, in a manner reminiscent of that observed in both a previously reported trimeric calcium species, [LCa(H2Bpin)]3 (where L is as defined in R1 = 10.31%) X-ray diffraction analysis.pseudo-tetrahedral N3O-coordination sphere, with ligation provided by the bridging borate and a single \u03b2-diketiminate anion, the nature of the fourth nitrogen-centred ligand differs across the two Mg centres of the molecule. Whereas Mg(1) is coordinated by a molecule of diphenylacetonitrile, the coordination sphere of Mg(2) is completed by a diphenylketeniminate anion, generated by deprotonation of the nitrile starting material. Magnesium and barium derivatives of the identical diphenylketeniminate anion are precedented by complexes in which the alkaline earth centres were further coordinated by sterically demanding bis(imino)acenaphthene (Dipp-BIAN) radical anions, in which case the magnesium complex was prepared by deprotonation of diphenylacetonitrile by [(Dipp-BIAN)MgMe].5 is formed in a similar manner, in a process which is detrimentally competitive with the desired hydroboration reactivity under catalytic conditions , using the standard catalytic reaction of 10 mol% of the precatalyst V in conjunction with a 1\u2009:\u20092.1 ratio of propionitrile (0.40 M) to HBpin (0.82 M). While the reactions displayed apparent pseudo-zero order kinetic behaviour signified a first order dependence on [HBpin] of 2.79. Although relatively small, this value would constitute a very large secondary effect and is significantly in excess of comparable results (kH/kD = 1.62) reported by Hartwig et al. during studies of catecholborane metathesis at ruthenium(ii) alkyl centres, in which B\u2013H bond breaking processes are integral to the progress of the reaction.4 do not persist under catalytic conditions but are consumed by intramolecular hydride transfer from HBpin to the metal-bound aldimide fragment.We interpret the suppression of reaction rate at high substrate concentrations on the ability of both reagents to coordinate to the metal centre, either as a neutral nitrile donor or through the likely formation of borohydride species. We suggest that this deduction is further supported by the first order dependence of the reaction rate on [HBpin] in the presence of excess EtCN wherein increasing concentration will favour the displacement of the neutral nitrile from the magnesium coordination sphere allowing the onward formation of intermediate aldimidoborohydride species akin to compound pseudo-zero order kinetics displayed during the hydroboration of propionitrile, experiments performed to interrogate the rates of reactions displayed by the array of aryl nitriles employed in the study = \u20131.46; \u03c1(EWG) = +0.68] are relatively small and must be interpreted with caution,In contrast to the he study evidencehe study , the obsp-MeOC6H4CN) and electron withdrawing (m-MeOC6H4CN) aryl substitution. For the hydroboration of p-MeOC6H4CN a first order dependence on the concentration of [catalyst] .This apparent change in mechanism was interrogated through kinetic studies of the hydroboration of nitrile substrates bearing representative electron donating into a hydride intermediate (G) through metathesis of the magnesium\u2013butyl bond with HBpin (designated as the circled reaction 1 in H and I) exemplified by the isolation of compounds 2 and 3 appears facile, irrespective of nitrile substrate identity (reaction 2). Whilst the activation of organonitriles toward different nucleophiles \u2013(c) may be discriminated.H (i.e. k\u20133 \u226b k3). The assembly of aldimidohydridoborate anions (J) such as that confirmed by the crystallographic characterisation of compound 4 requires the displacement of pre-coordinated nitrile by the HBpin substrate amine product (M) via the assembly of a further borate intermediate (L) J K\u20131 mol\u20131) of the free energy of activation for the alkyl nitrile hydroboration catalysis.The more basic character of alkyl nitriles ensures that the monomer/dimer equilibrium depicted as reaction 3 in k5 > k\u20134 yieldingH to J and its subsequent consumption through B\u2013H transfer to the coordinated aldimide fragment. The observed rate of catalysis for alkyl nitrile hydroboration is, thus, dictated by not only the ability of HBpin to replace nitrile in the magnesium coordination sphere but also the consequent ease of intramolecular C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN hydride reduction.The catalytic hydroboration of alkyl nitriles is consequently determined by the pre-equilibration of 2 and 3, magnesium aldimide derivatives bearing N-aryl substitution will benefit from considerably enhanced conjugative stability in comparison to those bearing alkyl residues of comparable steric demands. We suggest, therefore, that the kinetic profile observed for the hydroboration of p-MeOC6H4CN reflects the resistance to intramolecular hydride transfer of aldimidoborate species analogous to compound 4 scale\" fill=\"currentColor\" stroke=\"none\">N reduction suggests that the sequence of reactions 5\u20137 in J with a further molecule of HBpin (shown as reaction 8 in S\u2260 = \u2013174.8 (\u00b118.2) J K\u20131 mol\u20131) is also congruent with pre-equilibration of Ar(EDG)CN and HBpin and the onward reaction with a second molecule of HBpin. Consideration of the entire process illustrated by As highlighted by the isolation of compounds I) with a solution structure similar to that depicted for 2 in H* (vide infra). Use of the steady state approximation allows the derivation of a rate law that is dependent on [I] and may be identified as the rate determining process in a hydroboration catalysis in which k3 \u226b k\u20133 \u226a k4.For 3-methoxybenzonitrile, Mg\u2013H insertion will provide a dimeric aldimide (H*). Under this regime the role of the nitrile substrate is encapsulated by the experimentally deduced second order dependence on initial precatalyst concentration, [V], and is simply reflective of the involvement of two magnesium centres in the formation of H*.We suggest that this process, therefore, occurs with only partial rupture of the dimeric unit as illustrated in V has been demonstrated as an active precatalyst for the HBpin-derived hydroboration of a range of alkyl and aryl nitriles to form bis(boryl)amines. Catalysis proceeds under mild conditions, with reasonable catalyst loadings and is proposed to occur through a sequence of magnesium-mediated B\u2013H insertion and metathesis steps that are crucially dependent on a variety of pre-equilibration steps that are dictated by minor variations in substrate basicity and the stability of mono- and dimeric intermediates. These observations indicate that, somewhat counter to historical prejudice, there is likely to be considerable variation across even superficially identical reactions when catalysed by alkaline earth reagents.In conclusion, the \u03b2-diketiminato magnesium species Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The first reactivity of the hydroborylene ligand is described, giving access to a remarkable range of unprecedented boron-centered species. II complex [{cat(TMSL)Si}(Cl)Ni\u2190:BH(NHC)2] 1 (Dipp); Dipp = 2,6-Pri2C6H3; NHC = :C[(Pri)NC(Me)]2) to form the hydride-bridged hydroborylene-NiII complexes 2. The reaction of 1 with isoelectronic CO, however, is reversible and furnishes the related unprecedented hydride- and CO-bridged hydroborylene NiII complex 2-CO, which undergoes isomerisation through silyl/NHC exchange at ambient temperature to afford the corresponding hydro(silyl)boryl NiII complex 3. Markedly, 2 readily and quantitatively react with one further molar equiv. of isocyanide to give, under borylene liberation and H/Cl ligand exchange, boraketiminium species, which represent cationic BI complexes. These latter compounds are highly reactive in solution, and can undergo quantitative transformation into previously unknown cyanoborenium cations.For the first time, the reactivity of the metal- and N-heterocyclic carbene-supported monovalent hydroborylene is reported. Isocyanides react with the hydroborylene Ni C. Brown in the synthesis and reactivity of hydroboranes,I centre .16 Thus,1 contains a three-coordinate, 16-electron NiII centre,1 at \u201378 \u00b0C resulted in an immediate color change to deep orange. A single-crystal X-ray diffraction analysis of deep orange-yellow crystals grown from this reaction mixture revealed that 2-Cy (11B NMR spectrum of 2-Cy (\u03b4 = \u201343.0 ppm) clearly correlates to a signal in its 1H NMR spectrum as shown through 1H,11B HMQC NMR analysis = 2.230(2) \u00c5, MBOB\u2013Ni = 0.48; For 1: d(B1\u2013Ni1) = 2.015(2), MBOB\u2013Ni = 0.76). This results in a tetrahedral BI centre whose lone-pair of electrons is directed towards the \u03c0*-orbital of the CNCy ligand (d(B1\u2013C44) = 1.637(3) \u00c5, MBOB\u2013C = 0.75), resulting in considerable C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond weakening in this fragment. The calculated HOMO for 2-Cy comprises largely of this bonding interaction, as well as bonding contributions from Ni scale\" fill=\"currentColor\" stroke=\"none\">NC = 1626 cm\u20131) when compared with related reported species (viz. [CpMn(CO)2-\u03b72(CNR)-B(But)(NHC\u2032)], \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNC = 1856\u20131930 cm\u20131; R = Me, Cy; NHC\u2032 = C[(Me)NC(Me)]2).14 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNC = 1655 cm\u20131, in 2-Cy is in line with that observed experimentally.\u00a7The calculated value, \u03bd The low Mayer bond order (MBO) for the B\u2013C(NCy) bond suggests little degree of CyNC:\u2192B donation. Conversely, some back-bonding from the NiII centre to the CyNC ligand in 2-Cy is observed (d(Ni1\u2013C44) = 1.820(2) \u00c5, MBOC\u2013Ni = 1.12), further evidenced by the relatively linear Ni1\u2013C44\u2013N6 angle (\u2220NiCN = 153.0(1) \u00b0) when compared to the B1\u2013C44\u2013N1 angle of 126.3\u00b0. Thus, the bonding model outlined in 2-Cy.Compound hat 2-Cy , Fig. 2 i.e. CNR with R = 2,6-Xyl, Bz) to THF solutions of 1 resulted in the formation of essentially isostructural \u03bc-hydride, \u03bc-CNR hydroborylene NiII complexes, 2-Xyl and 2-Bz, respectively scale\" fill=\"currentColor\" stroke=\"none\">NC = 1634 cm\u20131; 2-Bz: \u03bd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNC = 1627 cm\u20131). Their 11B NMR spectra are also very similar to that for 2-Cy, each showing a single broad resonance. Complexes 2 are poorly soluble in common organic solvents, and decompose to a complex mixture over the course of one day, but are stable in the solid state for an indefinite period of time. Important geometrical and spectroscopic parameters are summarised in 1H,11B HMQC NMR analyses (see above).\u00b6B\u2013H stretching vibrational bands were not observed for these species, presumably as they were too weak. The presence of the B\u2013H fragments was confirmed with Addition of related ligands . The stretching vibrational frequency for the CO ligand in 2-CO indicates significant lowering of the CO bond order (\u03bdCO = 1694 cm\u20131) relative to free CO. Despite this, the reaction of 1 with CO is reversible, with storage of suspensions of 2-CO in THF yielding small amounts of crystalline 1 after one day. Observation of the frontier orbitals of 2-CO reveals that both the HOMO and HOMO-5 involve considerable donation to the \u03c0* orbital of the CO ligand , leading to the four-coordinate NiII complex IM1 . Subsequent coordination of the BI centre to the CO ligand leads to weakening of the B\u2013Ni bond and B\u2013C bond formation, generating 2-CO . The negligible thermodynamic barriers and minimal energy gain upon binding CO, then, explain the reversibility of this reaction. Whilst some degree of B\u2013Ni bonding is present in 2-CO, calculated bond orders for this interaction (Wiberg Bond Index (WBI)B\u2013Ni = 0.17; MBOB\u2013Ni = 0.30) are considerably lower than those for both the B\u2013C and Ni\u2013C bonds . Notably, these calculated MBO values for the Ni\u2013C and B\u2013C bonds in 2-CO are somewhat lower than those for the closely related bonding interactions in 2-Cy, again yielding an explanation for the reversibility of the reaction of 1 with CO.In contrast to reactions with isocyanides, uct 2-CO as an eqO ligand , in a si with CO indicate2-CO is stable in the solid state for weeks. However, upon warming THF solutions of in situ generated 2-CO to ambient temperature, a new compound is formed as a mixture with 1 after 2 h. Repeated re-crystallisations of this reaction mixture led to crystalline samples of the new product contaminated with small amounts of 1 , considerably more shielded than that for 2-CO most likely due to a greater charge density residing on the formally anionic boron centre in 3. The CO stretching vibrational band in the IR spectrum of 3 is higher relative to that in 2-CO indicative of reduced back-bonding from boron to CO in transitioning from a borylene to a boryl ligand. The greater stability of 3 over 2-CO may be owed to the NHC ligand now on NiII, whose Pri groups allow for an octahedral geometry at nickel through anagostic interactions with two flanking CH3 groups.19s formed , Fig. 4.1 leads to the formation of dark precipitates and silent 11B NMR spectra. Conversely, addition of two molar equiv. of CNR to 1 gives rise to complete borylene liberation as well as an unexpected H/Cl ligand exchange, giving facile and quantitative access to extraordinary three-coordinate boraketiminium complexes, [{(NHC)2BCNR}+Cl\u2013] , which can also be described as three-coordinate BI cations.SiLNiH] complex fragment = 1.467(4); t4-Bu: d(B1\u2013C23) = 1.433(2) \u00c5) and C\u2013N (4-Cy: d(C23\u2013N5) = 1.221(4); t4-Bu: d(C23\u2013N5) = 1.220(2) \u00c5) bonds are also in keeping with this, supported by a DFT analysis of the frontier orbitals in 4-Cy, which are indicative of \u03c0-bonding between these centres boraketiminium form is more prominent (45.3%), corroborating that 4-Cy indeed has a degree of BI character. The striking further reactivity of t4-Bu, which is reminiscent of low-valent boron and group 14 chemistry,1H NMR spectrum of CD2Cl2 solutions of t4-Bu indicates the loss of isobutene, and the clean formation of a single species containing a B\u2013H fragment , giving strong evidence for the formation of the cyanoborenium cation, [{(NHC)2B(H)(CN)}+Cl\u2013] 5-H. Remarkably, addition of two equiv. of CNBz to 1 directly leads to the benzyl derivative of 5-H, [{(NHC)2B(Bz)(CN)}+Cl\u2013] 5-Bz, via C\u2013N bond cleavage of the boraketiminium/borylene cation intermediate. The molecular structure of 5-Bz confirms the formation of a terminal cyanoborenium complex (d = 1.142(7) \u00c5) when compared with the terminal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond in t4-Bu (d(C23\u2013N5) = 1.220(2) \u00c5). The formation of these complexes represents a new entry into NHC-cyanoborane chemistry, species which are typically extremely challenging to access.1.Braunschweig and co-workers have previously reported that addition of multiple equivalents of CNR or CO to borylene TM complexes can affect complete borylene-TM bond cleavage.fragment undergoe centres . Surprisnds.4-Cy suggests complex , with a Cy: dB1\u2013C = 1.467(II complex 1 with one molar equiv. of isocyanides or CO has given access to a new hydride-bridged isomeric form in hydroborylene transition-metal chemistry in complexes 2, as well as the hydride- and CO-bridged hydroboryl complex 3. In addition, the unprecedented boraketiminium and cyanoborenium salts 4 and 5, respectively, resulted from reaction of 1 with two molar equiv. of isocyanides in good yields. As such, this chemistry demonstrates the potential utility of the hydroborylene ligand in HB:\u2192TM complexes for the realisation of new functional groups in boron chemistry.In summary, the striking reactivity of the hydroborylene ligand in the HB:\u2192NiThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Room-temperature metal-free hydrogenation catalysis. tBu)HB(C6F5)22 prompts intramolecular C\u2013H bond activation to give (CHN)2(tBu) (CMe2CH2)CB(C6F5)23, defining an upper limit of Lewis acidity for FLP hydrogenation catalysis. A series of seven N-heterocyclic carbene\u2013borane (NHC\u2013borane) adducts ((R\u2032CNR)2C)(HBC8H14) and ((HC)2(NMe)(NR)C)(HBC8H14) are prepared and converted to corresponding borenium salts. These species are evaluated as catalysts for metal-free imine hydrogenation at room temperature. Systematic tuning of the carbene donor for the hydrogenation of archetypal substrate N-benzylidene-tert-butylamine achieves the highest reported turn-over frequencies for FLP-catalyzed hydrogenation at amongst the lowest reported catalyst loadings. The most active NHC\u2013borenium catalyst of this series, derived from 10a, is readily isolable, crystallographically characterized and shown to be effective in the hydrogenation catalysis of functional group-containing imines and N-heterocycles.This manuscript probes the steric and electronic attributes that lead to \u201cfrustrated Lewis pair\u201d (FLP)-type catalysis of imine hydrogenation by borenium ions. Hydride abstraction from (I The hydrogenation of unsaturated bonds is one such chemical transformation that is employed on a terrific industrial scale.8H14] [B(C6F5)4] can be used as a catalyst for the metal-free hydrogenation of imines and enamines.2. This affords an NHC\u2013borane that delivers hydride to a transient iminium ion with HB(C6F5)2 led to the formation of NHC\u2013borane adduct (ItBu)HB(C6F5)22 (NHC\u2013B bond length of 1.645(4) \u00c5 and an average B\u2013C6F5C bond length of 1.639(4) \u00c5 22 , which w639(4) \u00c5 . The exp2via treatment with the hydride abstraction reagents [Ph3C][B(C6F5)4], Me3SiOTf or HOTf showed no reaction. This stands in contrast to the facile hydride donation typically demonstrated by NHC\u2013boranes.2 with HNTf2 in toluene to >100 \u00b0C for four days the clean conversion to a new product was evident from the appearance of the 11B resonance at \u201314.8 ppm. 1H NMR spectroscopy showed sharp singlet resonances at 0.86 ppm and 1.04 ppm and a broad singlet resonance at 1.80 ppm integrating in a 9\u2009:\u20096\u2009:\u20092 ratio. These combined NMR data suggest the new species (CHN)2(tBu) (CMe2CH2)CB(C6F5)23 is derived from C\u2013H activation of a tert-butyl substituent (3 confirmed its bicyclic nature (2(tBu)(CMe2CH2)CBBr2\u20092(tBu)(CMe2CH2) CB(tBu)Cl3 is thought to proceed via transient generation of a cation and subsequent C\u2013H activation imidazol-2-ylidene (Idipp) at 60 \u00b0C for one hour to afford Idipp\u2013borane adduct 4a in 79% yield 4] at 45 \u00b0C overnight results in the generation of Ph3CH and the quantitative conversion of the NHC\u2013borane to a new species as evidenced by 11B NMR signals at 82.6 ppm and \u201316.6 ppm. These are consistent with the formation the borenium\u2013borate salt [(Idipp)BC8H14][B(C6F5)4] 4b. Alternatively, treatment of 4a with tBuN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHPh and the addition of a stoichiometric equivalent of [tBu3PH]][B(C6F5)4] results in generation of 4b with concurrent reduction of the imine as evidenced by 1H NMR spectroscopy. This observation prompted efforts to employ 4b in an FLP hydrogenation of tBuN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHPh. However combination of excess tBuN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHPh and 4b under 102 atm H2(g) showed no evidence of reduction of the imine 2]. This latter one-pot approach is similar to that described by Brahmi et al. to prepare a series of NHC\u2013BH3 compounds.2C)HBC8H14 and ((HC)2(NMe)(NR)C)HBC8H14 were prepared 4] to give the corresponding borenium salts [((R\u2032CNR)2C)BC8H14] [B(C6F5)4] and [((HC)2(NMe)(NR)C)BC8H14] [B(C6F5)4] concomitant with the generation of a stoichiometric amount of Ph3CH (11B resonance in the range of 81\u201388 ppm attributable to a three-coordinate B center. The expected resonances for the [B(C6F5)4]\u2013 anion were seen at \u201316.7 ppm. The species 10b was isolated as colorless crystals in 72% yield via recrystallization from CH2Cl2/pentane at \u201335 \u00b0C. Crystallographic data (NHC bond length of 1.5768(3) \u00c5 similar to that observed for 1b (1.580(3) \u00c5).67Each of these adducts reacts with [Phof Ph3CH . The moshic data revealed3P)(HBC8H14) (11) was also synthesized and isolated as colorless crystals in 82% yield. The 11B NMR signal was observed at \u201314.9 ppm and exhibited both B\u2013H coupling of 88 Hz and B\u2013P coupling of 48 Hz. The 31P{1H} resonance for 11 is at \u201313.0 ppm and possesses similar B\u2013P coupling. Single crystal X-ray diffraction confirmed the formulation (see ESI11 with stoichiometric [Ph3C][B(C6F5)4] gave a complex mixture of products as evidenced by 31P{1H} and 11B NMR-spectroscopy.For comparative purposes the phosphine\u2013borane adduct scale\" fill=\"currentColor\" stroke=\"none\">CHPh as a comparative screen. A solution of each was generated in situ, added to the imine substrate and pressurized with 102 atm H2(g) for 30 minutes. After the reaction, the extent of conversion to amine was assessed by 1H NMR spectroscopy. These data reveal an inverse correlation between the steric demands of the NHC and the hydrogenation activity of the borenium catalyst of 940 h\u20131. A slight increase of catalyst loading to 0.15 mol% and an extension of the reaction time to 2 h at room temperature under 102 atm H2(g) led to complete conversion to tBuNHCH2Ph and the product could be isolated in 83% yield scale\" fill=\"currentColor\" stroke=\"none\">NtBu, is readily reduced (p-(MeO2C)C6H4CH PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNtBu (6F5)3.6H5CH PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNCHPh2 slow imine reduction scale\" fill=\"currentColor\" stroke=\"none\">NPh and p-EtOC6H4(Me)C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNPh are readily hydrogenated to corresponding amines scale\" fill=\"currentColor\" stroke=\"none\">NCH2Ph was observed (1b,6710b smoothly catalyzes the hydrogenation of 8-methylquinoline to 1,2,3,4-tetrahydro-8-methylquinoline (Comparison of the isosteric catalysts d yields . In thes reduced , entry 1g>NtBu , entry 2eduction , entry 3observed , entry 6observed , entry 7observed , entry 8uinoline , entry 9via an FLP mechanism, perturbations that enhance the Lewis acidity at B or the steric demands of the NHC ligand can serve to deactivate the catalyst. At the same time, sterically unencumbered NHCs bearing electron withdrawing substituents enhance catalyst activity. Crudden and co-workers10b is an effective catalyst for imine and N-heterocycle reduction at low catalyst loadings and it affords the highest TOF yet reported for metal-free hydrogenation catalysis. Efforts are continuing to systematically develop borenium-based metal-free hydrogenation catalysts and to further broaden their applications.In this manuscript we have probed the electronic and steric parameters that impact on the ability of ligand stabilized borenium cations to act as metal-free hydrogenation catalysts. Although this catalysis proceeds Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Photocyclized intermediate formation and quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC twisting are the dominant processes behind the AIE. i.e. formation of intermediate or rotation around the elongated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, is responsible for the AIE effect, which is strongly structure-dependent but not related to structural rigidity.Aggregation-induced emission (AIE) is the long-sought solution to the problem of aggregation-caused quenching that has hampered efficient application of fluorescent organic materials. An important goal on the way to fully understand the working mechanism of the AIE process was, for more than a decade, and still remains obtaining more comprehensive insights into the correlation between the ultrafast excited-state dynamics in tetraphenylethylene (TPE)-based molecules and the AIE effect in them. Here we report a number of TPE-based derivatives with varying structural rigidities and AIE properties. Using a combination of ultrafast time-resolved spectroscopy and computational studies, we observe a direct correlation between the state-dependent coupling motions and inhibited fluorescence, and prove the existence of photocyclized intermediates in them. We demonstrate that the dominant non-radiative relaxation dynamics, E\u2013Z isomerizationIn less than two decades, the seminal discovery of aggregation-induced emission (AIE) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC twisting35The excited-state dynamics in TPE and TPE derivatives, including the role of phenyl rotation,1\u20136 scale\" fill=\"currentColor\" stroke=\"none\">C twisting) in 1\u20136, with the formation of a photocyclized intermediate in all compounds on different timescales, and the dominant relaxation channels responsible for the AIE effect (or its absence) in every particular case being strongly structure-dependent. The implications of these observations for the working mechanism of AIE are fully explained.In our work to restrict certain relaxation channels in the excited state and investigate their role in the AIE effect, we synthesized a set of TPE-based derivatives, 1\u20136 , with va1\u20136 with increased structural rigidity and their corresponding photocyclized phenanthrene derivatives 1-PC\u20136-PC were synthesized according to the synthetic routes shown in 1H-NMR, 13C-NMR and high resolution mass spectrometry. The structures were determined by single-crystal X-ray diffraction between geminal phenyl groups display only one type of phenyl orientation , giving rise to what we will refer to from now on as a quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. In contrast, the bonds connecting the peripheral phenyl groups with the C1\u2013C2 bond shorten (e.g. d2\u2013C15C) to fall into the bond length range that is between that of a typical single C\u2013C bond and a normal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond. The twisting of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond and torsion of the phenyl rings in 1\u20136 are analyzed metrically in terms of the dihedral angles \u03c421\u2013C1\u2013C2\u2013C15C and \u03c41\u2013C2\u2013C15\u2013C20C, respectively. For 1\u20136 in solution, each molecule has its unique set of restricted degrees of freedom with varying degrees of rigidity. The absolute change of the dihedral angle around the C1\u2013C2 bond (|\u0394\u03c421\u2013C1\u2013C2\u2013C15C|) in TPE derivatives in solution upon excitation decreases in the order 1\u20133 and 5\u20136 do effectively restrict the motion of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. We note that this trend persists for the changes of the dihedral angles of the phenyl torsion (|\u0394\u03c41\u2013C2\u2013C15\u2013C20C|) in 1\u20133 after photoexcitation. Two ethylene tethers in geminally locked structure 5 and vicinally locked structure 6 have similar restriction effects on the phenyl torsion with the smallest change of the dihedral angles (ca. 20\u00b0). Fig. S26. To expl and 5\u20136 , which i1\u20136, compounds 1 and 2 are archetypal TPE-based AIEgens showing intense turn-on fluorescence upon aggregation (see the fluorescence quantum yields (QY) in 3 shows unexpectedly highly fluorescence in solution, and becomes even more fluorescent upon aggregation making it AEE (aggregation-enhanced emission)-active. Contrary to our expectations, the significantly more rigid structures 4\u20136 have low fluorescence quantum yields in solutions, among which 5 is an AIEgen, while 4 and 6 are not AIE-active. These findings clearly demonstrate that structural rigidity is not directly correlated with the AIE properties and the RIM paradigm needs to be revisited.The RIM mechanism dictates a reciprocal correlation between the rigidification of the structure and possible AIE properties. For molecules 1\u20136 in dilute solutions and film are shown in 1\u20133 in solution display similar UV absorption peaks at around 310 nm, the UV absorption maxima of 4 and 5 are markedly blue shifted (<270 nm), and the absorption maximum of 6 is notably red shifted (368 nm). All compounds 1\u20136 in dilute solutions undergo photocyclization upon UV excitation derivatives.3 undergoes photocyclization, as evidenced by the emergence of similar new emission peaks at 361, 378 and 400 nm scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting, phenyl torsion and photocyclization) in 1\u20136 upon excitation, and to determine their contribution to the photophysics of the AIE mechanism, probing the molecular dynamics in the excited state is necessary. Prior to this, developing a quantitative understanding of the coupling relationship between the relaxation channels directly related to the molecular motions is imperative. To that end, we have constructed the 3D potential energy surface (PES) of 1 in solution as a function of the aforementioned modes using DFT calculations ) has a molecular geometry corresponding to ca. 8\u00b0 twisting angle along the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting mode, ca. 50\u00b0 torsion along the phenyl torsional coordinate, and potential energy whose value is set to 0 kcal mol\u20131. The coupling between the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting and phenyl torsion along the minimum energy path (MEP) of 1 on the ground state PES scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting (<9\u00b0) and potential energy , indicating that under standard conditions the torsion of the phenyl rings dominates the ground state dynamics in 1. This is further corroborated by the thorough analysis of the intrinsic reaction coordinate (IRC) calculations scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting mode in 1 in the ground state from one minimum energy geometry through the highly twisted transition state to the other minimum energy geometry scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting is associated with significant changes in the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond length (\u223c0.07 \u00c5), and a marked increase in potential energy . In the excited state, the elongation (\u223c0.12 \u00c5) and partial loss of the double bond character of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond in 1 triggers the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting as the dominant motion which is coupled with the phenyl torsion scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting mode in 1 on the first excited state PES reveals that on the way from the Frank\u2013Condon (FC*) geometry to the minimum energy geometry , the quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twists ca. 50\u00b0, which is accompanied by the phenyl torsion with an amplitude of less than 25\u00b0. Although their coupling relationship in the excited state is well fitted by the quadratic function \u0394 twisting = 0.0671 (\u0394 torsion)2 \u2013 3.9048 \u0394 torsion \u2013 2.7952, the PES around the S1,min is rather shallow and simple harmonic oscillations PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting may easily take place with the damping process, resulting in the relaxation to the S1 min spectrum corresponds to the statistically most probable geometry of the molecules on a specific timescale in the excited state. Thus, the photoinduced excited state structural dynamics associated with molecular motions is reflected in the evolution of TA spectra.1\u20136 flows mainly from the central C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond to the adjacent C\u2013C (Ph) bonds scale\" fill=\"currentColor\" stroke=\"none\">C bond and shortening of peripheral bonds, which is accompanied by C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting coupled with phenyl torsion. This process in 1 is reflected in the excited state absorption spectra shown in 1 transitions from Sn to the emissive state S1 due to the weak stimulated emission as evidenced by the band at 500 nm with a negative amplitude at 1.3 ps. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond elongation PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting. On the picosecond timescale between 1.3 ps and 3.79 ps scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond took place. After 3.79 ps scale\" fill=\"currentColor\" stroke=\"none\">C bond elongation (\u03c41), the sequential dominant motion of the quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting (\u03c42), and the last motion dominated by the phenyl torsion (\u03c43), respectively. It should be noted that both processes corresponding to \u03c41 and \u03c42 are coupled with phenyl torsion, as proved by the band at 430 nm and predicted by the calculation (1-IM (\u03c44) having a new bond connecting atoms C20 and C22 directly scale\" fill=\"currentColor\" stroke=\"none\">C bond elongation corresponding to the population of transients in the emissive state . In contrast to 1\u20132, the decay of the band at 610 nm with growing intensity of the band at 430 nm accompanied by a blue shift scale\" fill=\"currentColor\" stroke=\"none\">C bond slows down. This is probably due to the steric hindrance from the ortho-position substituents in 3. The depopulation of the band at 428 nm scale\" fill=\"currentColor\" stroke=\"none\">C elongation and quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting) of 4 upon excitation have similar dynamics and time constants to those of 1\u20132 scale\" fill=\"currentColor\" stroke=\"none\">C bond elongation in 5 upon excitation in solution is reflected by the population of the 628 nm band with its red shift before 1.03 ps scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting and phenyl torsion take place at the same time. Concomitantly, the intensified red-shifted band at 330 nm indicates that a new species is formed, which is further proved by the emergence of a band at 438 nm scale\" fill=\"currentColor\" stroke=\"none\">C elongation in 6 upon excitation was not observed in the fs-TA spectra because of its negligible increase of only 0.03 \u00c5 (6 upon excitation has a short d20\u2013C22C distance (1.70 \u00c5). This means that the vicinally bi-locked structure of 6 restricts the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC elongation and the freedom of torsion for all phenyl rings with short distances, which facilitates the ultrafast formation of the photocyclized intermediate on the subpicosecond timescale, and thus 6 barely fluoresces in solution. After 4.68 ps, the photocyclized intermediate of 6 undergoes structural relaxation scale\" fill=\"currentColor\" stroke=\"none\">C bond elongation with a time constant of \u03c41 < 0.4 ps scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting with a time constant of 1\u20132 ps , or (b) the ultrafast formation of the photocyclized intermediate (IM) on the sub-picosecond timescale , or they do fluoresce (c) due to the structural stability of the emissive state of the molecule on a relatively longer timescale (3). Thus, the dynamics of the quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting (\u03c42) with the possibility of intermediate formation in S* is the key factor that determines the fluorescence properties of TPE derivatives in solution. When the non-radiative relaxation pathways for TPE derivatives in solution are blocked in the solid state via two different routes: relaxation to the original ground state structure and formation of a singlet ground state IM with a long-lived lifetime (\u03c44) that either (1) reverts back to the original compound or (2) is oxidized to form the corresponding photocyclized product (PC) scale\" fill=\"currentColor\" stroke=\"none\">C bond twisting, the potential energy hypersurface, the Gibbs free energy, the geometry optimization of TPE derivatives in solution and in the solid state (both in the ground state (S0) and excited state (S1)), and the UV/vis and Raman spectra of photocyclized intermediates 1-IM\u20136-IM, were performed at the DFT level of theory using the M062X functionalDetailed information on the synthesis and characterization of 2) and time-resolved resonance Raman (ns-TR3) experiments were carried out using the same experimental setups and methods as described previously.3 measurements was 266 nm. Two probe wavelengths (355 nm and 309.1 nm) were used for the ns-TR3 experiment. The ns-TR2 data were obtained by using the difference between the Raman spectra obtained at different power values of the 266 nm pump laser. Compounds 1\u20136 in MeCN solution were studied in a flow-through 2 mm path-length cuvette with an absorbance of 0.5 at 267 nm throughout the data acquisition. More details are available in ESIFemtosecond transient absorption (fs-TA), nanosecond transient absorption (ns-TA), femtosecond time-resolved fluorescence (fs-TRF), nanosecond transient resonance Raman scale\" fill=\"currentColor\" stroke=\"none\">C bond elongation, quasi C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond twisting, phenyl torsion and photocyclization are the sequentially dominant processes in TPE derivatives upon photoexcitation in solution. Their state-dependent coupling motions derived from ultrafast time-resolved spectroscopy show that (a) the lifetime of the species with electronic configuration conducive to fluorescence is the determining factor for the observed fluorescence quantum yields, (b) in less rigid structures, the rotation of the elongated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond is the dominant motion that eventually leads to the non-radiative decay (e.g. AIE-active TPE), and (c) in the more rigid structures, the torsion of phenyl rings will dominate the relaxation dynamics and, if possible, lead to the formation of singlet ground state photocyclized intermediates (e.g. AIE-active or AIE-inactive bi-locked TPE derivatives). Thus, while the dominant intramolecular motion that serves as a non-radiative relaxation channel being restricted upon aggregation in every particular case is strongly structure-dependent, counter-intuitively, the AIE effect (or absence thereof) is not directly related to rigidity as seemingly implied by the RIM paradigm.TPE-based derivatives There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Bisdititanium Ti22 trimerises carbon suboxide scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) to form [{Ti22}{\u03bc-C9O6}], which contains a 4-pyrone core, via the monoadduct [Ti22 (\u03b72-C3O2)]. syn-bimetallic bisdititanium complex Ti22 2) 1 with carbon suboxide scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, C3O2) results in trimerisation of the latter and formation of the structurally characterised complex [{Ti22}{\u03bc-C9O6}]. The trimeric bridging C9O6 unit in the latter contains a 4-pyrone core, a key feature of both the hexamer and octamer of carbon suboxide which are formed in the body from trace amounts of C3O2 and are, for example, potent inhibitors of Na+/K+-ATP-ase. The mechanism of this reaction has been studied in detail by DFT computational studies, which also suggest that the reaction proceeds via the initial formation of a mono-adduct of 1 with C3O2. Indeed, the carefully controlled reaction of 1 with C3O2 affords [Ti22 (\u03b72-C3O2)], as the first structurally authenticated complex of carbon suboxide.The reaction of the CO and CO2) promoted by well-defined molecular complexes,3O2 is the first in the series of the synthetically available carbon sub-oxides featuring an odd number of carbonse.g. ylides3O2 (hereafter referred to as carbon suboxide) is relatively unstable (it auto-polymerises above 0 \u00b0C but can be stored indefinitely below \u201335 \u00b0C), it is moderately straightforward to prepare via the dehydration of malonic estersUnlike the plethora of catalytic and stoichiometric transformations of carbon's most common oxides . It is then rapidly oligomerised into macrocyclic structures, predominantly cyclic hexamers and octamers .Carbon suboxide is also formed in small quantities octamers , which c3C3O2 to produce C3O2 involved a coordination complex of Ag,3O2 towards Pt(0), Pt(ii) and Rh(i) complexes by Pandolfo et al. proposed the formation of C3O2 complexes but lack of structural data plagued these early investigations.3O2 with organometallic fragments by isolating, for example, the products of its insertion into M\u2013H bonds. A main problem of these early studies was the propensity of C3O2 to act as a source of ketene scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) and CO. Thus, in the presence of phosphorous containing ligands in the coordination sphere of the metal centre, this led to the formation of the corresponding phosphorous-ylides, as shown by Hillhouse et al. by the reaction of C3O2 with WCl2(PMePh2)4 furnishing WCl2(CO)(PMePh2)2{C,C\u2032:\u03b72-C(O)CPMePh2}.3O2 can displace COD in (PPh3)2Ni(COD) to yield (PPh3)2Ni{C,C\u2032:\u03b72-C3O2} where the C3O2 ligand coordinates via the central and one of the terminal carbons,3O2 to late transition metal centres have also been reported, but, and to the best of our knowledge, there have been no other reports investigating the interaction of C3O2 with organometallic or other coordination compounds. Undoubtedly one of the reasons is its capricious nature, which has favored in silico studies of its reactivity especially towards transition metals.3O2 is one of the least explored \u2018small molecules\u2019 from a synthetic chemist's point of view, a fact underlined by only two short reviews in the current literature.In terms of coordination chemistry, it was proposed that the thermal decomposition of Agsyn-bimetallic complex [Ti22] (Pn\u2020 = C8H4(SiiPr3)2) (1) towards CO, CO2, and heteroallenes and therefore envisioned that (1) might be a good candidate for the binding and activation of C3O2. Herein we present the unprecedented trimerization of C3O2 promoted by (1), We have previously reported on the synthesis,1) to C3O2 at \u201378 \u00b0C, instantly produced a homogeneous brown solution which, upon warming to \u201335 \u00b0C and then slowly to room temperature, deposited some C3O2 polymer, together with a brown supernatant. Filtration of the reaction mixture and work up of the filtrate afforded a brown-green solid, which was isolated in moderate to good yields , and proved to be a diamagnetic, spectroscopically pure new compound (2). The 1H-NMR spectrum of (2) consisted of 16 doublets in the aromatic region signifying the formation of a dimer exhibiting four inequivalent pentalene environments; this was further substantiated by the observation of eight peaks in the 29Si{1H}-NMR spectrum of (2).Exposure of a crimson-red toluene solution of (ctrum of (2) cons13C{1H}-NMR spectrum of (2) displayed 41 resonance in the region between 389\u201396 ppm, 32 of which were assigned to the four inequivalent pentalene environments and Th(iv) featuring dihaptoacyl ligands with substantial oxy-carbene character.2) showed a strong absorption at 2061 cm\u20131 characteristic of a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO moiety along with bands at 1658, 1591 and 1532 cm\u20131 characteristic of carbonyl functionalities, but also in agreement with haptoacyl ligands with a strong oxo-carbene character.2) (3O2 (9O6] core between the two [Ti2Pn\u20202] moieties found in (2) (The 145 ppm ), with tacter.2) , which i.2) (3O2 . At thisd in (2) and 5, wd in (2) , all of 2) (2.4648(14) and 2.4834(16) \u00c5) are retained but have been slightly elongated in comparison to that in (1) (2.399(2) \u00c5).2 fashion. This bonding mode is best described as an haptoacyl with a considerable carbenoid contribution to the resonance structure. We base this on the observed metrics of the corresponding bond lengths and angles (Ti2\u2013C1: 2.17(3) \u00c5, Ti2\u2013O: 2.13(3) \u00c5, Ti3\u2013C7: 2.316(17) \u00c5 Ti3\u2013O: 2.133(19) \u00c5, C1-01/C7\u2013O5: 1.30(3)/1.28(3) \u00c5; C7\u2013Ti3\u2013O: 33.1(7)\u00b0, C1\u2013Ti2\u2013O: 35.3(8)\u00b0 C7\u2013O\u2013Ti3: 81.3(12)\u00b0 Ti2\u2013O\u2013C1: 74.1(16)\u00b0) which compare well with those crystallographically determined for [(\u03b75-C5H5)2Ti(\u03b72-COMe)Cl] (Ti\u2013C: 2.07(2) \u00c5, Ti\u2013O: 2.194(14) \u00c5, C\u2013O: 1.18(2) \u00c5; C\u2013Ti\u2013O: 32.0(4)\u00b0, Ti\u2013O\u2013C: 68.3(7)\u00b0, Ti\u2013C\u2013O: 79.7(6)\u00b0),13C{1H}-NMR spectroscopic data discussed above. Furthermore, the bonding of these haptoacyl moieties to the pyrone heterocycle of the [C9O6] core (i.e. C2\u2013C1 and C5\u2013C7. 1.38(3) \u00c5 and 1.46(3) \u00c5 respectively) are in good agreement with the CO\u2013CH3 groups found in [(\u03b75-C5H5)2Ti(\u03b72-COMe)Cl] (C\u2013C: 1.47(3) \u00c5).9O6] core in (2) is that the pyrone 6-membered ring is not planar scale\" fill=\"currentColor\" stroke=\"none\">O bond distances (i.e. C6\u2013O4: 1.207(18) \u00c5 vs. 1.253(12) \u00c5 in 4-pyrone) are similar within esd's. Unfortunately, due to the mixed occupancy of the CCO moiety and O6 over the two sides of the [C9O6] core in (2) and the resulting crystallographic restraints used to model this disorder, we cannot talk with certainty about the bond lengths and angles of these two ligating moieties to this 6-member ring. Nevertheless, upon inspection of the corresponding bond lengths of these two atoms to the Ti centres, we can deduce that the bonding situation is far from straightforward. For instance, the Ti1\u2013C\u2032 bond resembles the ones found in Ti\u2013NHC complexes, although closer to the high end of the spectrum (2.2\u20132.35 \u00c5),3O2\u20093O2) while the C\u2013O bond remains unchanged (1.442(13) \u00c5 in free C3O2). The same trend (i.e. C\u2013C elongation) applies when compared with the corresponding bond lengths found in ketene scale\" fill=\"currentColor\" stroke=\"none\">C: 1.314 \u00c5, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO: 1.162 \u00c5). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u2013Ti dative interaction, e.g. in [cis-Ti(OEt2)22].2) is diamagnetic and the elongation of the Ti\u2013Ti bonds might suggest an increase of the formal oxidation state of each Ti centre by one (i.e. Ti(ii) in (1) to Ti(iii) in (2)). However, the oxy-carbene character of the C7\u2013O5 and C1\u2013O1 units as well as the non-aromatic 6 membered heterocycle of the [C9O6] core suggest that complicated resonance structures are in play, and assignment of formal oxidation state and Ti\u2013Ti bond order in (2) is therefore problematic.The Ti\u2013Ti bonds in (2), the reaction was probed computationally. Density functional calculations using the ADF program suite (BP86/TZP) were carried out on model systems in which the SiiPr3 groups on the pentalene ligands were replaced by H atoms to increase computational efficiency. The computational analogues of experimental structures are denoted by italics; calculations on the analogue of the starting material 1, Ti2(C8H6)21, have been described previously.3O2 to 1, Ti2(C8H6)2(C3O2), led to two local minima, 3 and 3\u2032 . The alternative structure, 3\u2032, could possibly be formed as a kinetic product. The structure of 3 clearly suggests that formation of 2, with two C atoms and one O atom bound to the two Ti atoms, proceeds by the left hand side of the molecule depicted in Isomer 3O2 proposed here differs from some others calculated which indicate bonding primarily to the central carbon. In the cases of metal carbonyls2Pn2 has very high energy electrons and acts as a electron pair donor through its Ti\u2013Ti bond.3O2 has electron density on the central C can be found in that described for the adduct of (1) with CO2 [Ti22(\u03bc-CO2)] (6) which has been studied computationally due to the instability of (6) in solution .3O2 in (3) reveals a similar picture to the one found in (6). The Ti\u2013O distance in 3 (2.19 \u00c5) is shorter than that of 6 (2.27) indicating increased donation to O. This analogy between (3) and (6) is further reflected by the short Ti\u2013Ti bond distances that are characteristic of both these computational models. It should be noted that the HOMO-3 retains Ti\u2013Ti bonding character hence there is only a slight lengthening of Ti\u2013Ti distance from 1 to 3 (2.37 \u00c5 to 2.41 \u00c5). A CBC3 has an arrow going from the Ti PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tTi double bond to C3O2 acting as a Z ligand, in the same way as CO2 behaves in [Ti22(\u03bc-CO2)].3O2 in this model are in good agreement with the ones determined crystallographically vide infra.The HOMO of orbital . The HOM orbital is respo2, and to investigate possible intermediates in the reaction, the geometries of Ti2(C8H6)2(C3O2)2, 4, Ti2(C8H6)2(C3O2)3, 5, and 2 were optimised (In order to examine the energetics for the formation of ptimised . Key bonptimised .3O2 and to 5 reacting with 1 appear to be purely entropic.The free energies for possible reaction pathways are shown in 2): (a) the formation of the intermediate [Ti22] (3) (i.e. the adduct between (1) and C3O2 that would arise from the addition of 1 eq. of the latter to the former) and (b) the termination of the consecutive two additions of C3O2 to (3) by the capping of (5) by (1) or alternatively (c) the reaction of (4) with (3). The barriers for the two pathways, (b) and (c), are too similar to distinguish between them energetically. In all possible pathways leading to (2), the formation of adduct (3) is the common denominator. The high activation energy calculated for the reaction of (3) with a further molecule of C3O2 to form (4) indicates that (3) should be isolable at low temperature. Indeed, repeating the reaction in the same manner as for the synthesis of (2), but removing volatiles at ca. 0 \u00b0C, resulted in the formation of no carbon sub-oxide polymer and 1H-NMR analysis showed the formation of an extra species along with (2), exhibiting two inequivalent pentalene ligand scaffolds (i.e. 8 doublets in the aromatic region). Encouraged by this observation, the reaction between (1) and C3O2 was repeated under higher dilution conditions to prevent the last step of the formation of (2) and the reaction mixture was kept below \u201310 \u00b0C throughout. Upon removing volatiles at low temperature (ca. \u201325 \u00b0C), and lyophilising the residue with benzene (below \u201310 \u00b0C), this new species was isolated in almost quantitative yields and with spectroscopic purity of >98%. More conclusive evidence that (3) is indeed that predicted by calculations was provided by 13C{1H}-NMR spectroscopy. The most salient features of this spectrum are three resonances located at 159.8, 260.4 and 7.03 ppm which all correspond to quaternary carbons and which we assign to coordinated C3O2 : 129.74 (OCCCO) and \u201314.62 (OCCCO)et al. and Pandolfo et al. using 13C-CP/MAS NMR spectroscopy, while the latter is significantly shifted downfield in comparison with these two literature examples -C3O2)(PPh3)2] with M = Ni, Pt respectively).3O2 in (3) is found at much lower field (7.03 ppm) compared with the ones assigned to the terminal carbons (see above) and follows the trend observed in previous studies -C3O2)(PPh3)2] with M = Ni, Pt respectively); it has to be noted though that is shifted downfield compared to these reported values. These discrepancies are expected as the documented examples concern electron rich monometallic metal fragments of d10 transition metals, unlike the present case where a syn-bimetallic Ti\u2013Ti core is involved. The coordination of C3O2 was further corroborated by IR spectroscopy (thin film) that showed characteristic bands for CCO (2060 cm\u20131) and CO functionalities (for free C3O2 2280 cm\u20131) which are in good agreement with values reported for the complexes [M-C3O2)(PPh3)2] .3) even in the solid state. Nevertheless, based on the spectroscopic data discussed above, (3) was assigned as the adduct of C3O2 with (1), i.e. the first intermediate towards the formation of (2). This was unequivocally established by a single crystal XRD study and \u03b71via that same carbon to the other one (Ti1). The latter also coordinates to the central carbon (C2) of the C3O2 ligand. The molecular structure of (3) represents the first example of a crystallographically authenticated example of C3O2 coordination and confirms the coordination modes of C3O2 predicted by Pandolfo and Hillhouse based on spectroscopic evidence.3)2C3O2 (2.4293(14) \u00c5) is similar to the one found in parent (1) (2.399(2) \u00c5) within esd's; a similar invariance in the Ti\u2013Ti bond length has been observed in the adducts of (1) with CO 2] dTi\u2013Ti = 2.4047(5) \u00c5; [Ti22(CO)2] dTi\u2013Ti = 2.4250(10) \u00c5).3O2 has a profound effect on its bond angles, with the most prominent changes being the significant deviation of the O1\u2013C1\u2013C2 and C1\u2013C2\u2013C3 angles from linearity (179.93(11)\u00b0 and 178.32(12)\u00b0 respectively in free C3O2\u2009vs. 179.57(12)\u00b0 in free C3O2\u20093O2 are similar within esd's to the ones found in free C3O2 (C1\u2013O1: 1.372(12)/1.1479(12) \u00c5; C1\u2013C2: 1.291(13)/1.2564(15) \u00c5; C2\u2013C3: 1.300(13)/1.2475(15) \u00c5; C3\u2013O2: 1.175(9)/1.1442(13) \u00c5) with the exception of the C1\u2013O1 bond distance which is elongated (1.372(12) \u00c5 in (3) vs. 1.1479(12) \u00c5 in free C3O2\u20092) (i.e. C2\u2013C3) is shorter (1.300(15) \u00c5 vs. 1.40(3) \u00c5 in (2)) while the C\u2013O bond lengths are the same within esd's. In the case of the corresponding angles, the CCO angle in both (2) and (3) are identical (172.4(16) \u00c5 and 172.0(10) \u00c5 respectively) (As can be seen from .3)2C3O2 is closey (179.93\u00b0 and 178y (179.93\u00b0 and 178y (179.93\u00b0 and 178 C3O2\u20092) , the corctively) .3O2 promoted by a well-defined molecular complex leading to the formation of (2). The core structure between the two [Ti2Pn\u20202] moieties is reminiscent of biologically relevant compounds responsible for the regulation of ion concentrations in cells. This transformation was studied computationally revealing that the first step is the formation of (3), which was confirmed experimentally by its isolation and structural characterization.In conclusion, we report the first example of the trimerisation of CThere are no conflicts of interest to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We definitively show that the CO stretching response to metal coordination is driven exclusively by \u03c0 polarization, which quantitatively correlates with \u03c0 back-donation and changes in CO bond length and frequency. nM(CO)]m complexes (L is an auxiliary ligand) is investigated in relation to the \u03c3 donation and \u03c0 back-donation components of the M\u2013CO bond and to the electrostatic effect exerted by the ligand\u2013metal fragment. Our analysis encompasses over 30 carbonyls, in which the relative importance of donation, back-donation and electrostatics are varied either through the ligand in a series of [(L)Au(CO)]0/+ gold(i) complexes, or through the metal in a series of anionic, neutral and cationic homoleptic carbonyls. Charge-displacement analysis is used to obtain well-defined, consistent measures of \u03c3 donation and \u03c0 back-donation charges, as well as to quantify the \u03c3 and \u03c0 components of CO polarization. It is found that all complexes feature a comparable charge flow of \u03c3 symmetry (both in the M\u2013CO bonding region and in the CO fragment itself), which is therefore largely uncorrelated to CO response. By contrast, \u03c0 back-donation is exceptionally variable and is found to correlate tightly with the change in CO bond distance, with the shift in CO stretching frequency, and with the extent and direction (C \u2192 O or C \u2190 O) of the CO \u03c0 polarization. As a result, we conclusively show that \u03c0 back-donation can be an important bond component also in non-classical carbonyls and we provide the framework in which the spectroscopic data on coordinated CO can be used to extract quantitative information on the \u03c0 donor properties of metal\u2013ligand moieties.The CO stretching response upon coordination to a metal M to form [(L) In most metal\u2013carbonyl complexes the CO bond appears weakened, i.e., the stretching frequency decreases (\u0394\u03bdCO = \u03bdCO \u2013 \u03bdfree-CO < 0) and the bond distance increases (\u0394rCO = rCO \u2013 rfree-CO > 0), but in a minority of complexes, which are sometimes termed \u201cnon-classical\u201d,\u03bdCO > 0 and \u0394rCO < 0). These differences in the CO stretching response to the M\u2013CO bond formation in metal carbonyl complexes are commonly explained in terms of the relative importance of the DCD constituents of the M\u2013CO bond. In particular, M \u2192 CO \u03c0 back-donation is represented as exerting a bond-weakening effect on CO, while M \u2190 CO \u03c3 donation is thought to act in the opposite way.On the experimental side, discussions on the nature of the M\u2013CO bond are mostly based on the analysis of the variation in the CO stretching frequency nM(CO)]m complex, three VB structures differing for the extent of \u03c0 back-donation can be written:(a) \u2013M\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO+ \u2194 (b) M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 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replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO \u2194 (c) +M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013O\u2013One way to schematically depict M(CO) bonding resorts to a simple Valence Bond (VB) picture. Focusing on the M(CO) moiety of a generic [(L)nM]m fragment. At the same time, the electronic structure of CO is also affected by the electric field generated by this fragment, especially in those cases when m \u2260 0. For CO in the presence of an electric field generated, for instance, by a positively charged metal fragment (exemplified here with the symbol \u2295), three analogue VB structures can be written:(d) \u2295 \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO+ \u2194 (e) \u2295 C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO \u2194 (f) \u2295 +C\u2013O\u2013In going from structure (a) to structure (b) and (c), where one has zero, one and two \u03c0* orbitals of CO engaged in back-bonding, the CO bond multiplicity goes from three to two to one. The relative weight of each structure will of course depend on the \u03c0 donor properties of the specific + 2Pz)3]\u2013,3C6H2, SIdipp for 1,3-bisimidazolin-2-ylidene, Idipp for 1,3-bisimidazol-2-ylidene and [HB2Pz)3]\u2013 is a fluorinated tris(pyrazol)borate ligand. They all exhibit blue shift of the CO frequency and therefore are classified as non classical. This has been taken by some authors as proof that the gold fragment gives poor or no back-donation.i) complex showing \u0394\u03bdCO < 0 has been fully characterized,o-carborane diphosphine (DPCb) as an ancillary ligand. Such an \u201cexception\u201d, which is even more singular when considering that the formal positive charge should strengthen the CO bond, made the authors speak of \u201cenhanced \u03c0 back-donation\u201d from the [(DPCb)Au]+ fragment. For the reader's convenience, an overview of the experimentally characterized systems, with the reported \u0394\u03bdCO values and reference to the original papers, is displayed in i) system, [{MeB[3-(Mes)Pz]3}Au(CO)], has been preliminarily reported as red-shifted in Still, however, carbonyl complexes showing blue shifted (\u0394via charge-displacement (CD) analysis,The relationship of the DCD constituents of coordination bonds, determined unambiguously \u03bdCO and \u0394rCO and the charge displacements of \u03c3 and \u03c0 symmetry along the M\u2013C\u2013O axis in response to the M\u2013CO bond formation in metal carbonyl complexes. We carry out our analysis first on an exhaustive series of 23 gold(i) carbonyls of formula [(L)Au(CO)]0/+, where L is a varying auxiliary ligand (including none), which includes 8 of the experimentally characterized complexes and which is evenly partitioned between charged and neutral complexes, as well as between classical (CO bond elongated and frequency red-shifted) and non-classical (CO bond shortened and frequency blue-shifted). The choice of binary gold complexes seems to be particularly simple and useful, as it permits to isolate and study systematically the effect of the trans ligand across a wide variety of metal binding properties and electronic effects. We begin our analysis (Section 3.1) by studying in greater detail the two extreme cases of \u201cnaked\u201d Au+, [Au(CO)]+, which displays the experimentally largest blue-shift, and of [(DPCb)Au(CO)]+, which is the only known case of a positively charged but significantly red-shifted gold(i) complex. Having thus highlighted the main findings, we then thoroughly confirm them by extending the study to the whole series of complexes (Section 3.2). To complete the work we then also investigate the role of the metal itself in driving CO response to coordination, by studying a series of homoleptic [(CO)nM(CO)]m complexes, with M including Hg, Ir, Ni, Fe, Cr, Mo, Co, Ru (Section 3.3). Finally, an ad hoc study of CO in a uniform axial electric field (Section 3.4) concludes the work, in order to isolate the impact of CO polarization and of its \u03c3 and \u03c0 components on CO stretching response.We thus investigate the relation between \u03942\u03c1 between the electron density of the adduct AB and that of the two non-interacting fragments A and B frozen at their in-adduct geometries. A partial progressive integration of \u0394\u03c1 along a suitably chosen bond axis z yields the so called charge-displacement function (CDF)42In the charge-displacement (CD) analysis framework, a chemical bond A\u2013B is analyzed in terms of the difference \u0394z, the exact amount of electron charge displaced from right to left (the direction of decreasing z) upon bond formation through a plane perpendicular to the z axis through the point z . If both the adduct and its constituting fragments have proper symmetry, \u0394\u03c1 can be decomposed into additive components of \u03c3 and \u03c0 symmetry with respect to the bond axis z ]m. Since the M\u2013CO bond is under investigation, the appropriate fragments are the ligand\u2013metal moiety [(L)nM]m and carbon monoxide CO, and the z reference axis joins the M and C centres. For the purpose of separating the \u03c3 and \u03c0 components of \u0394\u03c1, we group the orbitals of adduct and fragments according to the irreducible representations of the complex (and fragments) symmetry groups, which in the present cases are either the C2v group or the C3v group . No CO orbital is of A2 symmetry, therefore this representation is not relevant for the DCD analysis of the M\u2013CO bond and is found to represent only a (minor) rearrangement internal to the ligand\u2013metal fragment. Among the gold(i) complexes considered, [(PF3)Au(CO)]+, [(PH3)Au(CO)]+, [(P(CH3)3)Au(CO)]+, [(CF3)Au(CO)] and [(CH3)Au(CO)] belong to the C3v point group. All others have C2v symmetry. The symmetry point groups of the homoleptic complexes considered in Section 3.3 are listed in C2v and C3v have been used to separate the \u03c3 and \u03c0 components of the electron density difference also for these complexes.All of the complexes studied in this work have general formula + (Section 3.1). We then extend the analysis to a whole series of 21 [(L)Au(CO)]0/+ complexes (Section 3.2) and, finally, to a series of nine homoleptic complexes of general formula [(CO)nM(CO)]m (Section 3.3). The full list of complexes considered is in As mentioned in the Introduction, we first describe here a detailed investigation of the M\u2013CO bond in [Au(CO)]3)2Pz)3]\u2013 and Mes3P do not satisfy the symmetry requirements discussed in Section 2. [(DPCb)Au(CO)]+, however, is only slightly asymmetric in its minimum configuration and has been here constrained to C2v symmetry . The other two have been excluded from our analysis because they are much more asymmetric and to constrain them to C3v symmetry would probably alter their properties significantly.Three of the experimentally characterized gold complexes, with ligands DPCb, [HBAu(CO)], [(Cl)Au(CO)] and [(Br)Au(CO)] (the first of which is measured in the solid state and the others in solution) is actually blue-shifted rather than red-shifted as the calculations consistently suggest for all the neutral systems (the computed vfree-CO is 2143 cm\u20131). Regarding this apparent inconsistency, Frenking et al. recently found that the experimental blue shift is actually due to the presence of intermolecular interactions and not to the properties of the single molecule.3)Au(CO)] and of [(Cl)Au(CO)] and finding that the frequency increases from smaller to larger values than that of free CO. Indeed, Au\u2013Au interactions have been experimentally observed for these two complexes in the solid state\u03bdCO and \u0394rCO (computed rfree-CO = 1.137 \u00c5). In fact, we shall most often refer to the latter parameter only, because the non-uniform influence of vibrational mode coupling, and the more complicated CO vibration modes in the homoleptic carbonyls, make \u0394\u03bdCO a less reliable parameter than \u0394rCO for a quantitative analysis of its relation with the M\u2013CO bond characteristics.As 3.1+ and [(DPCb)Au(CO)]+. As mentioned in the Introduction, among the experimentally characterized gold carbonyl complexes, these two systems display the most different spectroscopic properties. [Au(CO)]+ (observed in neon matrix\u03bdCO = 94 cm\u20131) while [(DPCb)Au(CO)]+ (\u03bdCO = \u201330 cm\u20131). The computed values ]Au(CO)]+ represen+, showing in z, a positive CDF value corresponds to a charge flow from right to left while a negative value corresponds to a charge flow in the opposite (Au+ \u2192 CO) direction. The total CDF is positive over both the Au\u2013C and C\u2013O bond regions and also at the oxygen far side of CO, indicating a continuous flow of electrons in the direction from CO towards gold. The negative values of the curve on the left side of Au+ indicate a rearrangement in the opposite direction, which was shown in 1 component which is large and positive in the Au\u2013carbon region (identifying \u03c3 donation) and a B1 + B2 component which is negative in the same zone (identifying \u03c0 back-donation) plus a negligible A2 component. These components are easily recognized in the isodensity plots of the respective density difference shown at the top of the figure.We focus first on [Au(CO)]net from CO to Au+ amounts to 0.16e resulting from a donation component CT\u03c3don of 0.34e and a back-donation component CT\u03c0back of 0.18e. The first important comment here is that, in a system like this showing a large blue-shift of the CO stretching frequency, back-donation is actually a significant component of the interaction, estimated to be more than half as large as the donation.The net charge transfer CTEorb was found to be surprisingly large . The authors were cautious, however, in attributing such contribution exclusively to \u03c0 back-donation, as \u0394Eorb not only accounts for genuine inter-fragment orbital interactions but also for the polarization of the orbitals within each fragment.An analogous significant contribution from the electron charge rearrangement of \u03c0 symmetry was also recently highlighted in rCO/2 = 0.16e, resulting from a \u03c3 contribution of 0.07e and a \u03c0 contribution of 0.09.This uncertainty may be dissolved here, because, as discussed in Section 2, the interfragment charge transfer and its components are automatically separated from the corresponding components of CO polarization in the CDF picture. Inspection of +, with its CDFs reported in 1 (dashed blue line) and B2 (dotted-dashed line) components are not identical and are shown separately in the plot. We notice an immediate striking contrast with the previous [Au(CO)]+ case, in that the back-donation components globally dominate over \u03c3 donation in the coordination bond region, so that the total CDF is negative everywhere, indicating a continuous, though modest, flow of electrons from [(DPCb)Au]+ to CO. This confirms the already cited findings of 2 component. The net charge transfer at the inter-fragment boundary is \u20130.06e, resulting from a \u03c3 donation component of 0.26e (A1) and a \u03c0 back-donation component of \u20130.32e (\u20130.07 due to the B1 component and \u20130.25 due to the B2 component).We now turn to [(DPCb)Au(CO)]+. In analogy with [Au(CO)]+, the \u03c3 CDF remains positive in the CO region and the B1 component turns positive at the C site, reflecting the polarization of the CO bonding orbitals due to the electrostatic effect of the metal fragment. However, by contrast, the B2 component maintains its negative sign also in the CO region, i.e. the back-donation it represents is so pronounced that it penetrates the CO region and extends even beyond the oxygen. As a consequence, the CO bond is on the whole slightly polarized in the C \u2190 O direction (CTrCO/2 = 0.03e), resulting from a \u03c3 polarization in the same direction and a \u03c0 polarization in the opposite C \u2192 O direction .The polarization of the electron cloud in the carbonyl region also differs remarkably from that in [Au(CO)]+ behaves non-classically (blue-shifted \u0394\u03bdCO), while [(DPCb)Au(CO)]+ behaves classically (red-shifted \u0394\u03bdCO). The CD analysis reveals that the \u03c3 donation component of the metal\u2013CO bond is roughly comparable in the two cases (CT\u03c3don 0.34 vs. 0.26e), while \u03c0 back-donation is almost twice as large in [(DPCb)Au(CO)]+ (CT\u03c0back 0.32 vs. 0.18e) and its extent substantially reduces the C \u2190 O polarization of the CO bond. The polarization of the CO \u03c3 bonding orbitals is comparable in the two complexes ( 0.07 vs. 0.05e), but that of the \u03c0 bonding orbitals is not ( 0.09 vs. \u20130.02e). These findings suggest that \u03c0 electron displacement upon coordination is the main factor driving CO bond response. In particular, if the presence of the metal fragment, especially if positively charged, is capable of polarizing the \u03c0 CO bonding orbitals, even in the presence of a significant back-donation, the CO bond is strengthened; if, on the other hand, \u03c0 back-donation is strong and extended enough to contrast CO polarization, even in the presence of an equally cationic metal fragment, the CO bond is weakened.It is worth deepening the comparison between the two complexes examined so far. In both, the metallic fragment bears a formal positive charge. However, [Au(CO)]3.20/+ complexes listed in \u03bdCO and \u0394rCO as well as the various computed CT figures. The complexes are listed in order of increasing \u0394rCO and the experimentally characterized compounds are those shown in boldface. As briefly discussed at the beginning of Section 3, it is seen that, according to our computed shifts, the neutral complexes plus [(DPCb)Au(CO)]+ behave classically, while the remaining cationic complexes behave non-classically. The \u03c3 donation and \u03c0 back-donation CDFs for these complexes are collected, respectively, in the top and bottom panel of \u03bdCO, blue lines are for those showing blue shift.We now need to verify if the above preliminary surmise stands the test of a wider series of carbonyl compounds. To this end, we have extended the analysis to all 23 [(L)Au(CO)]+, of the inert ligands Ne and Xe, and of the anomalous [(DPCb)Au(CO)]+, even the net ligand-to-metal \u03c3 donation, CT\u03c3don, varies by only 0.05e across the whole series of ligands. On the contrary, the \u03c0 CDF all invariably exhibit a flow of \u03c0 electrons in the C \u2190 O direction , due to the positively charged metallic fragment, while the complexes showing red-shifted \u03bdCO (red lines) exhibit a negative , i.e., charge flows in the opposite C \u2192 O direction .Two eye-catching features emerge upon inspection of i) carbonyls: (i) \u03c3 donation is much less tunable than \u03c0 back-donation, being very little dependent on the nature and the charge of the ligand; (ii) whereas the net CO bond polarization turns out to be invariably oriented in the C \u2190 O direction (CTrCO/2 > 0), the direction of its \u03c0 density component can vary and appears to be tightly connected with the direction of the CO stretching shift and bond-length change. These findings are given a definitive illustration in rCO with CTnet, CT\u03c3don, CT\u03c0back, CTrCO/2, and is reported. In both figures, black triangles are used for the overall CT, red squares for its \u03c3 component and blue circles for its \u03c0 component. Empty symbols are for the neutral species, filled ones are for the cationic species.It thus appears quite clearly that in the series of gold can be seen between \u0394rCO and CT\u03c0back, a trace of which remains in the plot of \u0394rCOvs. CTnet. The same bond weakening effect of \u03c0 back-donation is also evident in the plot of \u0394\u03bdCOvs. CT\u03c0back (see ESIR2 = 0.849). rCO with CTrCO/2 and its components and . Not surprisingly, as these quantities are all directly related to the charge rearrangement of the CO bond itself, correlations are here quantitatively better (R2 is 0.970 for that with ). Obviously, as \u0394rCO correlates well with both \u03c0 back-donation and CO \u03c0 electron polarization, the latter two quantities are also in mutual correlation.Focusing first on k see ESI, though 3.3i) complexes where the donor/acceptor properties of the M\u2013CO bond were varied through the ligand L. We now extend the analysis to a series of homoleptic carbonyls of formula [(CO)nM(CO)]m, where the relative extent of the DCD constituents of the M\u2013CO bond and CO polarization are varied essentially by changing the metal. The full list of the considered homoleptic complexes is in rCO. We omit for brevity a presentation of the complete CDFs. The computed structures for these systems are in agreement with experimental X-ray data where available.22+ and Ir(CO)63+, both cationic, behave non classically, with experimental blue-shifted \u03bdCO at 2279.5 cm\u20131 for the former and at 2254, 2276 and 2298 cm\u20131 for the latter.42\u2013 at 1730 cm\u20131 5 ,4 and Cr(CO)6. The complexes present therefore a wide range of \u03bdCO variation but \u0394\u03bdCO turns out not to be a good parameter for analyzing correlations with the CD data because normal-mode coupling varies significantly with the different structure of the complexes. We therefore base our discussion, as already done for the gold(i) complexes, on the computed \u0394rCO. This varies in a range of 0.087 \u00c5 over the series, from \u20130.018 to 0.069 \u00c5 (In the previous sections we considered a series of gold( 0.069 \u00c5 .e) is much larger than that of \u03c3 donation (0.15e). In particular, almost no back-donation is found for Hg(CO)22+ while CT\u03c0back for [Fe(CO)4]2\u2013 is as high as 0.71e. This picture is consistent with the simple VB view discussed in the Introduction, in that we go from a purely \u03c3 M\u2013CO bond (structure a) for Hg(CO)22+ to a situation in which all \u03c0* CO orbitals are engaged in back-bonding (structure c) for [Fe(CO)4]2\u2013. Also the charge rearrangement (polarization) in the carbonyl region is seen to follow a similar trend, with a much narrower range of values (between 0.02 and 0.10e) than that of (from 0.21 to \u20130.30e). As before, no clear correlation can be discerned between \u0394rCO and the \u03c3 CT data, while CT\u03c0back and values are seen to decrease almost monotonically as \u0394rCO increases.The table shows that also in this series of compounds the range of variation in \u03c0 back-donation series, appears in fact to suggest, because the range of variation is now significantly enlarged, that a quadratic fit, rather than a linear one, may better represent the actual correlation , i.e. the cationic Hg(CO)22+ and Ir(CO)63+, show a flow of \u03c0 electrons in the C \u2190 O direction. All other complexes, where the CO bond weakens (red-shifted \u0394\u03bdCO and positive \u0394rCO) show opposite-direction flows.Once again, in the homoleptic series, the carbonyl complexes featuring CO bond strengthening C \u2192 O (negative) polarization, C\u2013O bond length increases quadratically and \u03c0 polarization is seen to increase much more rapidly than \u03c3 polarization. Conversely, as the field increases on the right, inducing C \u2190 O polarization, the C\u2013O bond shortens (much less rapidly).Let us focus first on the stretching response to the electric field. When the field is absent, the system corresponds to free CO and \u0394rCO and the \u03c3 and \u03c0 components of CO polarization induced by metal coordination, rather than by an applied field (disconnected circles in the figure), we notice immediately that the \u03c0 circles follow quite closely the correlation between field-induced polarization and stretching, while, in striking contrast, the \u03c3 circles deviate from the field-induced line and, moreover, span a very narrow range of (positive) polarization, essentially without any correlation with the widely varying \u0394rCO. This is indeed a very strong confirmation that the CO stretching response to any solicitation causing electron charge rearrangement, be it the formation of a M\u2013CO coordination bond or the effect of an external electric field, is driven essentially exclusively by the charge rearrangement of \u03c0 symmetry: whether induced by an external electric field or by metal coordination, C \u2192 O (C \u2190 O) polarization of the \u03c0 bond orbitals invariably and tightly correlates with bond lengthening (shortening).When we now compare these curves with the relation observed between \u03944nM(CO)]m metal carbonyl complexes, with the aim of elucidating on quantitative grounds the \u03c3 donation and \u03c0 back-donation effects on the CO stretching response, in particular the change in bond length \u0394rCO, to the M\u2013CO bond formation. The analysis was carried out for a large variety of carbonyls, in which the relative extent of the DCD constituents were varied both through L in a series of [(L)Au(CO)]0/+ gold(i) carbonyl complexes and through M in a series of anionic, neutral and cationic [(CO)nM(CO)]m homoleptic carbonyls. Crucially, for the purpose of this investigation, reliable and consistent measures, not only of \u03c3 donation and \u03c0 back-donation charges but also of the \u03c3 and \u03c0 components of CO polarization were obtained by the well-established charge-displacement analysis of electron-density differences, as resulting from accurate DFT calculations. The nature of the M\u2013CO bond in the considered complexes was found to range smoothly between the two extreme cases of an almost purely \u03c3 bonded complex (Hg(CO)22+, CT\u03c0back = 0.02e) and of a strongly back-bonded complex ([Fe(CO)4]2\u2013, CT\u03c0back = 0.71e). Conversely, all complexes were found to feature a narrowly comparable \u03c3 donation component, with CT\u03c3don values ranging from 0.14 to 0.34e. The same picture holds accurately for the electron cloud rearrangement over the carbonyl region: all considered complexes feature a comparable \u03c3 polarization of CO and a much more variable \u03c0 polarization. Quite remarkably, no correlation is found between \u0394rCO and the \u03c3 displacements, while \u0394rCO, \u03c0 back-donation and CO \u03c0 polarization all correlate tightly with one another.In this work we have carried out an in-depth analysis of the M\u2013CO bond in [(L)+ complex, where \u03c0 back-donation is so strong as to invert the polarization of the \u03c0 CO bonding orbitals in the C \u2192 O direction despite the formal positive charge on the ligand\u2013metal fragment, making it the only example of a cationic gold(i) carbonyl complex with classical behavior (\u0394rCO > 0). An ad hoc study of CO in a uniform axial electric field demonstrates that it is indeed the polarization of the \u03c0 CO bonding orbitals, no matter how induced (whether by the coordination bond to M or by an electric field), that drives direction and magnitude of the CO stretching response to the M\u2013CO bond formation.These results show that the driving force of the CO stretching response to the M\u2013CO bond formation is provided exclusively by the changes taking place in the \u03c0 electron density. In the complexes studied, such \u03c0 charge rearrangement is found to result from the interplay between \u03c0 back-donation (structures a\u2013c of the Introduction) and the electrostatic effect (structures d\u2013f) exerted by the metal\u2013ligand fragment. In particular, cationic metal\u2013ligand fragments polarize the \u03c0 CO bonding orbitals in the C \u2190 O direction, thus shortening the bond and enhancing the covalency, as highlighted in rCO in metal carbonyl complexes, we conclude that the value of \u0394rCO quantifies to an excellent extent the \u03c0 back-donation component of the M\u2013CO bond, since such component directly correlates with the \u03c0 polarization. In particular, where changes its sign , CT\u03c0back is approximately as high as the average extent of \u03c3 donation among the complexes herein considered. This indicates that \u03c0 back-donation is an important component also in the class of non-classical complexes, as those of gold(i) considered in this work.Regarding the fundamental question of what can be inferred on the nature of the M\u2013CO bond from the analysis of \u0394Supplementary informationClick here for additional data file."}
+{"text": "Water-enhanced oxidation of graphite via a modified Hummers method can produce graphene oxide with controlled species of oxygenated groups. Graphene oxide (GO) sheets with controlled species of oxygen-containing groups are important for fabricating graphene materials with desired structures and properties. Here we report a water-addition modified Hummers method to prepare GO sheets with tunable amounts of hydroxyl and epoxide groups without destroying their structural integrity. This method is simple, effective, and efficient. It can be applied to the mass-production of GO with controlled amounts and species of oxygenated groups, and improve the yields of synthesizing high-quality GO at low temperatures. However, the use of NaNO3 leads to the formation of NO2/N2O4 toxic gases, and introduces Na+ and NO3\u2013 ions to the waste water. Recently, Tour et al. improved the Hummers method by excluding NaNO3, increasing the amount of KMnO4, and performing the reaction in a 9\u2009:\u20091 H2SO4/H3PO4 mixture for a prolonged time.3 from the chemical recipe of the Hummers method did not affect the yield and oxidation degree of GO.GO can be prepared by oxidation and exfoliation of graphite. The Hummers method is the most widely employed technique for this purpose.On the other hand, GO with a high degree of oxidation usually has a high content of permanent defects.vii) compound (3 that is generated by the oxidation of water with Mn(vii) compound in the H2SO4 solution of KMnO4.In this paper, we report that heavily oxidized GO with good structural integrity can be produced in a high yield by adding a certain amount of water to the reaction system of our modified Hummers method.compound . This mevia a modified Hummers method4 (3.0 g) in 46 mL concentrated H2SO4 containing n mL water at 40 \u00b0C for 2 h, and the resulting GO is nominated as GO-n and the corresponding reduced GO is named rGO-n. A control GO sample, GO-0-95, was synthesized in the system without the initial addition of water. However, after the oxidation process, 100 mL water was slowly added into the reaction system, and kept at 95 \u00b0C for 15 min. The corresponding reduced GO is called rGO-0-95.GO samples were prepared All of these GO samples were carefully purified for characterization scale\" fill=\"currentColor\" stroke=\"none\">C (284.6 eV), C\u2013O (286.6 eV), C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (287.8 eV), and O\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (289.0 eV).IOC/ICC) of oxygenated carbon atoms scale\" fill=\"currentColor\" stroke=\"none\">O, and O\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) and intact carbon scale\" fill=\"currentColor\" stroke=\"none\">C) reflects the oxidation degree of GO,IOC/ICC becomes less pronounced as the water volume > 10 mL. The \u2018water-enhanced oxidation\u2019 was also confirmed by the magic-angle spinning 13C solid-state nuclear magnetic resonance (ssNMR) spectra of the as-prepared GO samples. The 13C ssNMR spectrum of GO mainly has the following signals: epoxide , hydroxyl , graphitic sp2 carbon scale\" fill=\"currentColor\" stroke=\"none\">C, \u223c133 ppm), carboxylic acid carbonyl scale\" fill=\"currentColor\" stroke=\"none\">O, \u223c167 ppm), and ketone carbonyl scale\" fill=\"currentColor\" stroke=\"none\">O, \u223c191 ppm).2 carbon at 133 ppm scale\" fill=\"currentColor\" stroke=\"none\">O and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO are mainly located at the edges of basal-plane vacancies or at the periphery of the GO sheets; PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups, reflecting a better structural integrity. According to PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (\u223c169 ppm) in its ssNMR spectrum.The delocalized \u03c0-conjugated structure of a graphene sheet is gradually fragmented to smaller domains upon functionalization, weakening its absorption of visible light. Thus, the color difference between GO samples can be used to qualitatively compare their functionalization degree. 133 ppm . Among t PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (1740\u20131720 cm\u20131)/H2O (\u223c1620 cm\u20131) peaks remains nearly unchanged in the spectra of GO-0 to GO-12, while this ratio for the spectrum of GO-0-95 is much higher, indicating the last sample has the highest content of carbonyl groups. However, the other oxygenated groups exhibited comparable intensities in all of the IR spectra.\u03b8 = 10.65\u00b0, and their d-spacings were calculated to be around 8.30 \u00c5. This value is much larger than that of natural graphite (3.35 \u00c5), indicating the successful functionalization of graphene by oxygenated groups.14The modulation of the oxidation degree and functional groups of GO by adding water has also been confirmed by ATR-FTIR spectral studies . The int\u20131) is associated with the defect-activated breathing modes of six-membered carbon rings, and the G-band (1580\u20131600 cm\u20131) is assigned to the E2g phonons at the Brillouin zone center.ID/IG, reflects the average distance between defects (LD) in graphene. For graphene and its derivatives, the value of ID/IG initially increases with increasing LD , followed by a decrease .LD derived from ID/IG. However, the relative amounts of these two types of defects in GO have to be evaluated by combining the ssNMR and XPS spectra of GO and the Raman spectrum of the corresponding rGO (indicative of the permanent defects).Raman spectroscopy is a powerful tool for studying the structures of CMGs. The typical Raman spectrum of CMG sheets consists of the D-, G-, and 2D-bands of carbon. The D-band , while its LD (1.26 nm) is the smallest among these GO samples. This result indicates that the \u2018defects\u2019 of GO-0-95 are mainly originated from permanent vacancies, implying that the reaction at 95 \u00b0C severely destroyed the graphitic domains of the GO sheets. This conclusion was also supported by its relatively higher content of carboxyl groups that usually locate at the permanent defects (vacancies and edges).In ondingly . Considen were measured to be 19.6, 18.0, 16.5, and 16.2 \u03bcm, respectively. The gradual decrease of size was caused by the unavoidable cutting of GO sheets upon water-enhanced oxidation.vii) species and/or decomposition at an elevated temperature of 95 \u00b0C.The severe structural damage of the GO-0-95 sheets was also indicated by the sheer decrease in their lateral dimensions. The sizes of the GO-0 to GO-12 sheets have a wide distribution from <5 up to over 50 \u03bcm, mainly (>90%) in the range 5\u201340 \u03bcm . The aveTd) of a GO sample increased with its oxidation degree. This trend agrees well with that of partially reduced GO samples.2, and H2O.Td of GO increase with its oxidation degree. The Td of GO-0-95 was measured to be 208.5 \u00b0C or GO-0-95, indicating that water in the reaction system significantly promoted the hydrolysis of organosulfate.Interestingly, thermogravimetric analysis TGA, demonstrC Fig. S5, between\u03b8 = 23.8\u201324.0\u00b0, d-spaces = 3.71\u20133.74 \u00c5). However, the XRD peak of rGO-0-95 is much broader (FWHM = 4.0\u00b0) than those of rGO-n (FWHM = 1.7\u20132.3\u00b0), also reflecting its higher content of residual oxygenated groups. The typical Raman spectra of all the rGO papers led to forming relatively more permanent defects to decrease the LD of rGO. The structural difference between the rGO papers is also reflected by their conductivities (\u20131) > rGO-4 (595 \u00b1 18 S cm\u20131) > rGO-8 (554 \u00b1 13 S cm\u20131) > rGO-12 (510 \u00b1 11 S cm\u20131). Accordingly, a small amount of water addition (\u22644 mL) during oxidation has negligible effect on the structural integrity of GO and the corresponding rGO, while a large amount of water (\u22656 mL) led to a slight decrease of their quality because of excess oxidation. Notably, rGO-0-95 exhibited a much lower conductivity (257 \u00b1 8 S cm\u20131), only about 40% of that of the rGO-0 papers. This is mainly due to the smaller sizes and much higher content of the permanent defects of rGO-0-95.rGO papers were prepared by reducing GO papers with HI dissolved in a water/ethanol mixed solvent (v/v = 1\u2009:\u20091). XPS C 1s analysis indicates that most of the oxygenated groups of GO have been removed upon reduction . The speO papers and S8\u2020 tivities and S9\u2020.2SO4 with water, lowering the intercalation efficiency of H2SO4/KMnO4 between the graphene layers of graphite.2SO4 has alternate graphene and H2SO4 layers; it is an intermediate of converting graphite to GO.2SO4 is usually formed by electrochemically or chemically increasing the electrochemical potential of graphite. The potential of stage I GIC increases, while the oxidizing potential of KMnO4 decreases upon reducing the concentration of H2SO4 (C2SO4H). Hence, stage I GIC could not be formed by oxidation with KMnO4 as C2SO4H < 14.4 M , because EGIC-I < E4KMnO.The yields of different GO samples have a large difference. The yield increased from 69 \u00b1 2% for GO-0 to 131 \u00b1 4% for GO-4, followed by a gradual decrease to 67 \u00b1 2% for GO-14 . This trOn the other hand, the relatively high yield of GO-0-95 is attributed to the in-plane vacancies and holes formed during the destructive oxidizing of GrO at 95 \u00b0C, facilitating the osmotic swelling and exfoliation of GrO to individual GO sheets.2-carbon content,The \u2018water-enhanced oxidation\u2019 of graphite to GO in our systems is an unusual phenomenon, because water is an ineffective oxidant for graphite. Moreover, it was reported that \u2018pristine GO\u2019 reacted with water to form conventional GO with an increase of spn and GrO-0-95) showed large variations (n (n = 4 to 14) were measured to be 50\u2013150 mL, much larger than those of GrO-0, GrO-2, and GrO-0-95 (42\u201344 mL). These volumes were also much larger than that of graphite powder , O3 was generated via oxidizing water by multi-nuclear Mn(vii) clusters as reported in literature.3 gas can also account for the larger volume expansions of GrO-n (n = 4\u201314) than those of the other GrO pastes.In fact, GO samples were formed by the exfoliation of their GrO precursors was also evidenced by monitoring the corresponding ultraviolet-visible (UV-Vis) spectra. The UV-Vis spectrum of a fresh concentrated H2SO4 solution of KMnO4 (3 g KMnO4 in 46 mL H2SO4) did not show a O3 band centered at 255 nm with peaks at 300 and 460 nmvii) by water, although the dilution of the solutions by adding water also had some contributions (only a maximum decrease of 16.3% by diluting with 12 mL water). The volume of the O3 gas formed in the solution also increased with its content of water, indicated by the numbers of gas bubbles generated in the solution filled in a capillary tube (inset of vii) (mainly from MnO3+). However, the solutions with water addition contain brown particles of MnO2 formed by reducing Mn(vii) with water.40The formation of O for 2 h , possiblinset of . The sol3 is a well-known strong oxidant with a standard oxidizing potential (2.08 V) higher than that of MnO4\u2013 (1.68 V).2 formed by reducing Mn(vii) with water is an effective catalyst for decomposing O3 to atomic oxygen.O3 can be enhanced by both water and newly-formed MnO2 .3 (vii) and H2SO4 .3 , atomic nd H2SO4 . The oxy2O2 (30%) was added to convert the remaining Mn species completely to soluble Mn(ii) ions in the system of preparing GO-0. However, in the system of preparing GO-0-95, only about 0.5 mL of H2O2 was consumed. Consequently, GrO-0-95 was further destructively oxidized by the residual Mn(vii) compound at an elevated temperature of 95 \u00b0C in a diluted H2SO4 solution (about 6.0 M). This destructive oxidation led to the formation of more permanent defects capped by carboxyl groups.On the other hand, the mechanism for the destructive oxidation process at 95 \u00b0C is elucidated as follows. Experimentally, 2.2\u20132.4 mL Hn. The electrical conductivity of rGO-4-0-48 h (894 \u00b1 26 S cm\u20131) is much higher than that of rGO-0 (605 \u00b1 20 S cm\u20131). Therefore, water addition is also an effective method to increase the oxidation degree of GO at low temperatures for producing high-quality GO in a much higher yield.The \u2018water-enhanced oxidation\u2019 was observed to be more pronounced by lowering the temperature of the oxidizing graphite ESI. For exavia a modified Hummers method can increase the oxidation degree of GO sheets. This approach can also modulate the content of hydroxyl and epoxide groups on GO sheets without sacrificing their structural integrity, and greatly increase the yield of high-quality GO prepared at a low temperature of 0 \u00b0C. The selective formation of carboxyl groups on GO sheets has been realized by the destructive oxidizing of GO at a high temperature of 95 \u00b0C. This work provided a simple and scalable technique for producing GO with controlled species of functional groups.The addition of a certain amount of water into the system of synthesizing GO Supplementary informationClick here for additional data file."}
+{"text": "Accessing highly electron deficient partially alkylated tungsten hydrides on silica via controlled hydrogenolysis of surface organometallic complex scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)W(Me)5. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013O\u2013)W(Me)5], 1, is an excellent precatalyst for alkane metathesis. The unique structure of 1 allows the synthesis of unprecedented tungsten hydrido methyl surface complexes via a controlled hydrogenolysis. Specifically, in the presence of molecular hydrogen, 1 is quickly transformed at \u201378 \u00b0C into a partially alkylated tungsten hydride, 4, as characterized by 1H solid-state NMR and IR spectroscopies. Species 4, upon warming to 150 \u00b0C, displays the highest catalytic activity for propane metathesis yet reported. DFT calculations using model systems support the formation of [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3(Me)2], as the predominant species at \u201378 \u00b0C following several elementary steps of hydrogen addition (by \u03c3-bond metathesis or \u03b1-hydrogen transfer). Rearrangement of 4 occuring between \u201378 \u00b0C and room temperature leads to the formation of an unique methylidene tungsten hydride [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3 scale\" fill=\"currentColor\" stroke=\"none\">CH2)], as determined by solid-state 1H and 13C NMR spectroscopies and supported by DFT. Thus for the first time, a coordination sphere that incorporates both carbene and hydride functionalities has been observed.The well-defined single-site silica-supported tungsten complex [( In this regard, the immobilized tungsten hydrides serve as multifunctional precatalysts that engage in separate, successive elementary steps. These involve propagative species that are proposed to display both hydridic (for the C\u2013H bond activation and olefin hydrogenation) and carbene functionalities (for the olefin metathesis steps). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013O\u2013)W(Me)5] (1) (Me = CH3) is a precatalyst for the metathesis of propane.1 should take place more readily than for the analogous Schrock species,2 surface.We recently demonstrated that the silica-supported tungsten pentamethyl .Because tungsten hydrides are expected to be highly fluxional on the NMR time scale, and are known to be found within a wide inset of reveals i.e., relativistic) effects, with variation in the other magnetic shielding mechanisms being on the order of a few tenths of one ppm. This aspect is discussed more fully in the ESI, Section 6.1H signals at 11.6 and 18.8 ppm are assigned to surface WHx, consistent with the results of the DFT calculations. This is also in agreement with the presence of multiple IR bands of 2 assigned for \u03bd(W\u2013H) in the range 1993\u20131905 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013H and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013CH3 moieties observed respectively by FT-IR and 1H solid-state NMR demonstrate that hydrogenolysis at 150 \u00b0C leads to the formation of a variety of species with little control on structure and identity of the ensuing surface complexes.Intriguingly, the variation in these chemical shifts appears to be nearly fully attributable to spin\u2013orbit (905 cm\u20131 . The pre13C cross-polarization (CP)/MAS NMR spectrum of 2 scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013H moieties of 2. Furthermore, the solid-state 13C CP/MAS NMR spectrum of 3 shows signals at 42 and 47 ppm which are left as a consequence of the partial hydrogenolysis of 1.The rum of 2 , preparem Fig. S6 attribut4 was prepared at low temperature, we recorded the solid-state 1H NMR spectrum using a low-temperature probe, at 100 K. The spectrum displays multiple signals in the low-frequency range of 0\u20132 ppm, and at high frequency, weak signals, at 8.7 and 16.3 ppm. Assignments of these signals are presented after discussion of the various hydrogenolysis pathways starting with 1.Because species PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013O\u2013)W(Me)5], 1, takes place, we proceeded with a DFT approach using a cluster model of the silica support. To ensure that our relatively small cluster model could be used to simulate the reactions on the silica surface, we validated it against periodic DFT and using slab silica models scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)W(Me)5] precursor 1 depicted as I in \u03b72\u2013H2) heptacoordinated tungsten species, with predicted W\u2013H distances of 1.84 \u00c5, and the H\u2013H bond elongated to 0.86 \u00c5 from 0.741 \u00c5 in gaseous H2.2 coordination is endergonic by 14.8 kcal mol\u20131. The hydrogenolysis of I occurs via transition state (TS) [I\u2013IV]\u2021 and requires an activation energy of 15.9 kcal mol\u20131, making this process possible at room temperature. This step corresponds to a \u03c3-bond metathesis event with the release of a CH4 molecule and formation of the tungsten monohydride [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH(Me)4], IV, which is 18.2 kcal mol\u20131 lower in free energy than I.Starting from the silica-supported [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH2(Me)3], VIII, is more stable than IV by 18.0 kcal mol\u20131. Similar to the previous findings for I, the formation of a methylidene species (VI) or an ethyl hydride (VII) requires too high of an activation energy and these processes can thus be excluded from further consideration. However, in contrast to I, IV can undergo reductive elimination to form a triplet W(iv) species [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)W(Me)3], V, with the release of one methane molecule. This process is favoured thermodynamically, with a free energy change of \u201323.1 kcal mol\u20131. The associated energy barrier estimated at the minimum energy crossing point (MECP) along the CH3\u2013H(W) bond stretching mode turned out to be only 14.8 kcal mol\u20131. However, because direct hydrogen addition occurs via a free energy barrier lower by \u223c3.0 kcal mol\u20131, the conversion of IV to VIII is the most likely route for further hydrogenolysis. The addition of the third, fourth, and fifth hydrogen atoms occurs via direct successive hydrogen additions. All other competing reactions again were found to require higher activation energies than the hydrogenation steps. Even reductive elimination, with formation of a W(iv) complex , requires 33.3, 38.4, and 26.3 kcal mol\u20131 for complexes VIII, XII, and XVI, respectively. Eventually, the final step is the formation of a silica-supported tungsten pentahydride [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH5], XVIII, which was found to be the most stable species of all those considered, with a Gibbs free energy of \u201377.9 kcal mol\u20131 relative to I.The subsequent transformation of I to XVIII suggests that hydrogenolysis of I is an exergonic process , leading to the formation of silica-supported tungsten pentahydride as the thermodynamic product. The proposed mechanism is a cascade or sequence of hydrogen addition reactions forming the series of supported metallo hydrides scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WHx(Me)y], x = 1\u20135, y = 4\u20130) along with the elimination of free methane molecules. The lowest barrier corresponds to the reaction with the second H2 molecule. The highest barrier was calculated for the addition of the fourth hydrogen molecule (during transformation of XII to XVI) and amounts to more than 20 kcal mol\u20131, suggesting that this step might be rate determining. On the basis of these calculations it is possible to suggest that the silica-supported [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3(Me)2] (XII) might represent the predominant surface species if 1 is hydrogenolysed to afford 4 at \u201378 \u00b0C. Other mechanistic pathways involving the reduction of W(vi) species have been found to be characterized by higher activation barriers.The above characterization of transformations from 2\u20134, i.e., 104) was obtained with 2 (prepared at 150 \u00b0C) (entry 1) compared with the tungsten hydrides prepared from a grafted neopentyl organometallic precursor.3 (prepared at 25 \u00b0C), a further increase in activity for propane metathesis was observed . This result could be attributed to a higher number of active tungsten hydride sites at this treatment temperature (25 \u00b0C), inasmuch as no apparent hydride transfer to the silica surface was observed by solid-state 1H NMR and IR spectroscopy , gave the best activity for this transformation . Significantly, the catalytic activity of species 4, when it was allowed to warm to room temperature scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013CH3 scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013CH3 or of a different kind of methyl group functionalities implies that the initial monopodal species 4 might have partially rearranged into a bipodal species under the experimental conditions by the transfer of a methyl group to the silica support. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013O\u2013)W(Me)5] (vide infra). Allowing the rotor sample to warm to room temperature for 10 min (outside the NMR probe) and then reintroducing it into the cold NMR probe led to the complete disappearance of the 1H chemical shift at 0.8 ppm and to the increase of the signal at 0.4 ppm ).13Second, this process was monitored by solid-state at 100 K . In the evident . The 1H Si\u2013CH3 and to t 0.4 ppm . Additio 0.4 ppm . All theperature and withs Fig. S7 as we fi1H NMR spectrum in 1H\u201313C HETCOR moieties, and a distinct signal at 231 ppm. The 1H peak at 7.3 ppm correlates only with the carbon resonance at 231 ppm in the 2D 1H\u201313C HETCOR NMR spectrum scale\" fill=\"currentColor\" stroke=\"none\">CH2) moiety.13C solid-state NMR spectrum of species 3 generated directly at room temperature scale\" fill=\"currentColor\" stroke=\"none\">CH2 and W\u2013H signals, the formation of a methylidene hydride from partially alkylated W-hydrides is supported by DFT calculations (vide infra). The W-alkylidene species formed was found by 1H NMR spectroscopy to be stable at temperatures up to 150 \u00b0C, but it decomposed readily upon introduction of D2 gas at 80 \u00b0C. Moreover, at room temperature we observed a proton chemical shift at 0.0 ppm corresponding to PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013CH3 moieties. This result is supported by the appearance of a peak at \u201312 ppm scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013CH3) in the 29Si CP/MAS NMR spectrum of 4 recorded at room temperature scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3(Me)2] is in agreement with the inferred structure as a main surface component. Considering the low hydrogenolysis temperature of \u201378 \u00b0C, the structural proposal is also in agreement with the DFT calculations that show a relatively high energy barrier of 20.3 kcal mol\u20131 for the reaction of [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3(Me)2] with the fourth molecule of hydrogen , are depicted with the selected characteristic NMR signals assigned 2] ; whereasH3(Me)2] and by sH3(Me)2] and 6a, assigned .4 when it is allowed to warm to room temperature. To provide further evidence for this chemical transformation, the evolution of 1 as a model compound was monitored by X-ray absorption spectroscopy (XAS) at room temperature with the sample in a stream of dry helium. As reported previously, microelemental analyses of 1 indicate that the tungsten pentamethyl moiety is anchored via only one isolated silanol group of the surface, maintaining its hexacoordination around the W center.The transformation of the well-defined monopodal species into a bipodal surface complex, accompanied by the transfer of methyl groups to the silicon atoms of the support, is invoked in the text as a major decomposition pathway for III-edge EXAFS scan of 1 in flowing helium strongly support the inference of two absorber\u2013backscatterer pairs, W\u2013C and W\u2013O, with internuclear distances consistent with typical sigma bonds. The W\u2013C and W\u2013O coordination numbers were found to be 4.9 and 1.0, respectively. Within the expected error (\u00b120%), these values are consistent with the initial supported species 1 being monopodal on the surface. Furthermore, there was no detectable W\u2013W contribution in the fit, indicating that, within error, the tungsten species remained mononuclear.The structural parameters determined by the best fit of the data of the first W L1 was present in the flow-through cell in the presence of helium (flow rate: 1.0 mL min\u20131), with continuous exposure to the X-ray beam, changes in the X-ray absorption near edge structure (XANES) region of the X-ray absorption spectrum show that the supported tungsten species was transformed.When The XANES region shows thE0 value determined in the best fit of the W\u2013C shell of species 1 after 45 min in contact with flowing helium , but the associated activation barrier for the direct conversion via transition state [XII\u2013XIV] is quite high to be accessible under the reaction conditions used. In contrast, the conversion of XVI to XIV is exergonic by only 2.3 kcal mol\u20131, and the associated free energy barrier for the direct conversion via transition state [XVI\u2013XIV] and the release of a H2 molecule amounts to just 22.3 kcal mol\u20131. This barrier can be overcome at room temperature, suggesting that the dominant route for the formation of XIV starts from XVI.Motivated by the structural rearrangements in the structure of XII is the predominant species at low temperatures according to our spectroscopic investigation and DFT calculations, species XVI can be formed by a less than stoichiometric conversion in the hydrogenolysis of XII to XVI, which we calculated scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)W(Me)5] (1) has been investigated at various temperatures. The hydride products have been characterized by means of elemental microanalysis, IR and solid-state NMR spectroscopies revealing that hydrogenolysis is temperature dependent and leads to different structural features. The results demonstrate that the hydrogenolysis of [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)W(Me)5] at \u201378 \u00b0C leads to an unprecedented silica-supported partially methylated tungsten hydride species. On the basis of DFT calculations, we propose that [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)WH3(Me)2] is the predominant surface species at this temperature. The thus-synthesized tungsten hydride represents the precursor of the most active catalyst for propane metathesis yet reported. The thermal rearrangement of this partially methylated species, when allowed to warm to room temperature, has been observed to proceed via divergent pathways. This change involves methyl transfer to the silica surface, evidenced by the presence of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013CH3 species indicated by solid-state NMR spectroscopy, transforming the initial monopodal surface complex 4 into a bipodal species. Such a change in podality was indicated by EXAFS spectra determined with 1 as a model substrate. Furthermore, the formation of a tungsten alkylidene (methylidene) hydride intermediate, which has always been considered in alkane metathesis but never been observed, has been proposed on the basis of solid-state NMR spectroscopy and DFT calculations.The controlled hydrogenolysis of silica-supported tungsten pentamethyl [(Supplementary informationClick here for additional data file."}
+{"text": "A porous aromatic framework with mesopores was used as a platform for an immobilized Pd catalyst with superb catalytic activity and size selectivity for the Suzuki\u2013Miyaura coupling reaction. 2PAF70-NH) to immobilize a palladium (Pd)-based molecular catalyst has been developed. The resulting immobilized catalyst PAF70-Pd, in which the framework is entirely constructed by phenyl rings linked with stable carbon\u2013carbon bonds, has high structural rigidity and stability. Compared with the known porous organic material immobilized Pd-based catalysts, PAF70-Pd has the highest Pd content so far. Moreover, PAF70-Pd has extremely high catalytic activity with good size selectivity and very easy recyclability in catalyzing the Suzuki\u2013Miyaura coupling reaction. In the current system, the catalyst loading could be as low as 0.001 mol% and the TOF value could go up to 28\u2009800 h\u20131 which is far higher than those of the known porous organic material immobilized Pd-based catalysts. In order to elucidate the particularly high catalytic efficiency of PAF70-Pd, we prepared PAF1-Pd from 2PAF1-NH for comparison. PAF1-Pd has a higher Pd content than PAF70-Pd. However, due to the absence of large enough mesopores in 2PAF1-NH, PAF1-Pd has almost no catalytic activity under the same conditions, which definitely demonstrated that the intrinsic mesoporosity of 2PAF70-NH plays a crucial role in the superb catalytic efficiency of PAF70-Pd. This strategy to immobilize Pd-based molecular catalysts has very good expansibility to be applied in the immobilization of different organometallic catalysts into the pores of PAFs, which also has very high potential in the chemical and pharmaceutical industry.A strategy using a mesoporous amine-tagged porous aromatic framework ( The excellent catalytic activity of the organometallic catalysts has attracted intensive interest from chemists in diverse research fields. Thereinto, palladium (Pd)-based organometallic catalysts are versatile tools that can catalyze various organic reactions such as the Suzuki\u2013Miyaura coupling reaction and Heck reaction.etc. Owing to their robust structure together with high stability in most organic solvents, PAFs are extremely suitable platforms for the catalysis of organic reactions. It\u2019s worth noting that, due to the presence of the Pd center and organic ligand, Pd-based organometallic catalysts usually have relatively large sizes. Hence, immobilization of Pd-based molecular catalysts into the porous materials often needs a large enough pore size. Most of the reported porous organic material immobilized Pd-based catalysts always suffer from low Pd utilization efficiency which might be due to that the pore space after introduction of the Pd-based catalyst is too small to accommodate the catalytic reaction. Apparently, for application of PAFs as the platforms for Pd-based organometallic catalysts, PAFs with large enough mesopores are needed. However, the synthesis of narrowly distributed mesoporous PAFs is still a challenge because of the interpenetration while using large-size monomers. Thus using PAFs as the platforms for covalent anchoring of organometallic catalysts into the pores still remains rare up to now. In this paper, we will make an attempt in this area.Using porous materials such as metal\u2013organic frameworks (MOFs), covalent organic frameworks (COFs) or porous organic polymers (POPs) as supported materials began to appear in the last few decades, which is a good idea because of their porosity and high surface area.2PAF70-NH, an amine-tagged PAF with narrowly distributed mesopores which was recently reported by our group,2PAF70-NH was used for the synthesis of our desired material, and the catalytic performance of the desired material (PAF70-Pd) was systematically studied. In order to further demonstrate the importance of the mesopores in 2PAF70-NH, another amine-tagged PAF (2PAF1-NH) without mesopores was also used as a platform to immobilize the same Pd-based molecular catalyst, affording PAF1-Pd for comparison with PAF70-Pd.Considering the need for large enough pore space for accommodating Pd-based molecular catalysts and the subsequent catalysis, in this paper, 2.2.1via the pre-modification procedure used in our previous literature report,2PAF70-NH, which contains mesopores with 3.8 nm diameter and amine anchors in the pores. Then, via the amine anchors using a condensation reaction with picolinaldehyde, the chelating ligand unit for Pd was introduced into the material, yielding the PAF which was named PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N. After a second post-treatment of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N with palladium acetate, the PAF material containing the Pd-based molecular catalyst was obtained, which was named PAF70-Pd. It\u2019s worth noting that the N,N-bidentate ligand is one of the most versatile coordination systems in organometallic catalysis, which can coordinate with various metal ions and has been widely used in homogeneous catalysis. In addition, the post-synthesis modification was very facile and efficient. The above features of our synthetic method could expand the application value of the PAF material. In addition, for the purpose of comparison, we prepared 2PAF1-NH according to the literature report,PAF1-Pd (the counterpart of PAF70-Pd) was prepared and the appearance of the characteristic peaks of the Schiff base (the new peaks at around 1600 cm\u20131) in the FT-IR spectrum of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N indicated the formation of an imine bond and thus the successful construction of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N. In comparison with PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N, in the FT-IR spectrum scale\" fill=\"currentColor\" stroke=\"none\">O stretching vibration and the new peaks at 1321 cm\u20131 could be attributed to the C\u2013O stretching vibration, which obviously indicated that PAF70-Pd was successfully obtained through our strategy. In addition, the successful synthesis of PAF1-Pd was also confirmed through a similar analysis of the FT-IR spectra scale\" fill=\"currentColor\" stroke=\"none\">CPyPAF70-N and PAF70-Pd all showed sharp uptakes, indicating the existence of micropores in the materials. It\u2019s worth noting that, in the desorption branch of 2PAF70-NH, a relatively sharp hysteresis demonstrated the presence of narrowly distributed mesopores. Compared with 2PAF70-NH, the corresponding hysteresis disappeared in the desorption branches of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N and PAF70-Pd, which indicated the disappearance of the mesopores after post-modification of 2PAF70-NH. The apparent surface area calculated from the Brunauer\u2013Emmett\u2013Teller (BET) model was 599 m2 g\u20131 for 2PAF70-NH, 263 m2 g\u20131 for PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N, and 172 m2 g\u20131 for PAF70-Pd. Through the change of pore size distributions calculated by non-local density functional theory (NLDFT), it was clear that the mesopores with a pore width of 3.8 nm of 2PAF70-NH disappeared in PAF70-Pd and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N (red curve) showed similar TGA curves. There is almost no weight loss before 300\u00b0C, which suggested the high thermal stability of 2PAF70-NH and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N. At about 400\u00b0C, the framework decomposition started and when the temperature was above 500\u00b0C the decomposition became obvious. The 3.96 wt% residue for 2PAF70-NH and 2.15 wt% residue for PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N at 800\u00b0C could be ascribed to some palladium oxide residue which originated from the Pd catalysts in the preparation process of 2PAF70-NH. As shown in PAF70-Pd (blue curve) had a 56% weight loss at 277\u2013320\u00b0C. This weight loss could be attributed to the decomposition of both N,N-bidentate ligand and AcO\u2013 species which were directly connected to the Pd center. Compared with PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N, PAF70-Pd showed lower stability, which might be due to that the Pd species could catalyze the cleavage of carbon\u2013carbon bonds around the Pd centers in the PAF material.etc. The high thermal stability and chemical stability made PAF70-Pd fully satisfy the demands of catalysis. The TGA analysis of PAF1-Pd can be found in the ESI was performed to test the thermal stabilities of the above PAF materials. As shown in Fig. S17. The Pd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF1-N, X-ray photoelectron spectroscopy (XPS) was performed. As shown in 5/2 orbital, indicated that the Pd species in PAF70-Pd and PAF1-Pd are present in the +2 state. Compared with the BE of 338.55 eV for free Pd(OAc)2, the BE for Pd species in PAF70-Pd and PAF1-Pd negatively shifted by 0.75 eV. This negative shift indicated that Pd(OAc)2 has strong coordination with the N,N-bidentate ligand in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF1-N.In order to further investigate the incorporation of palladium within PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N, some evenly distributed black dots with a mean diameter of about 1 nm emerged in the TEM images of PAF70-Pd, indicating that the Pd species are uniformly dispersed in the frameworks of the PAF material, which was in accordance with the above analysis of the TGA curve of PAF70-Pd. Similarly, compared with PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF1-N images obviously showed the successful introduction of Pd species into the PAF materials. As shown in vg>CPy , the TEM, EtOH gave the best results in terms of the reaction rate and yield of the current catalytic Suzuki\u2013Miyaura coupling reaction. Increasing the reaction temperature from 25\u00b0C to 80\u00b0C improved the reaction rate significantly scale\" fill=\"currentColor\" stroke=\"none\">CPyPAF70-N or the substituted aryl bromides with either an electron-withdrawing group or an electron-donating-group CHCH3, entries 6\u20138) afforded the cross-coupling products in excellent yields (up to >99%) with high turnover frequency (TOF) values , demonstrating the wide generality and functional tolerance of the current system.The catalytic performance of PAF70-Pd, some contrast tests were performed as shown in entries 9\u201311 of 9a, which could smoothly transform to 9b completely . These indicated that there is very low metal leaching during the reaction process. The results demonstrated that PAF70-Pd could undergo at least 3 cycles of the reaction without obvious loss of catalytic activity.For heterogeneous catalysts, recyclability is an important factor. Hence the recyclability of 2.4PAF70-Pd, PAF1-Pd and previously reported porous organic material immobilized Pd catalysts are given in PAF70-Pd and PAF1-Pd have the highest Pd contents, which might be due to the high effective surface areas of our materials. Moreover, PAF70-Pd showed far higher TOF values than other catalysts in PAF70-Pd gave a rare example of a catalytic system with size selectivity in this field , by a post-synthesis method, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPyPAF70-N with an N,N-bidentate ligand was successfully obtained. After a second post-treatment with palladium acetate, the PAF material containing the Pd-based molecular catalyst, named PAF70-Pd, was prepared. Because the narrowly distributed mesopores (3.8 nm) in 2PAF70-NH endow sufficient pore space for immobilizing the Pd-based molecular catalyst with a relatively large size, the resulting immobilized catalyst PAF70-Pd has evenly distributed Pd species and high Pd content (23.0 wt%). Furthermore, PAF70-Pd showed superb catalytic activity for catalyzing the Suzuki\u2013Miyaura coupling reaction with good size selectivity and very easy recyclability. Compared with the reported porous organic material immobilized Pd catalysts, PAF70-Pd has the highest Pd content and exhibits a far higher TOF value when catalyzing the same Suzuki\u2013Miyaura coupling reaction. By comparison with PAF1-Pd, it was clearly demonstrated that the mesopores in 2PAF70-NH are very important for the high activity of PAF70-Pd. After the introduction of Pd species with a relatively large size, PAF70-Pd still has large enough pore space to accommodate the catalyzed reaction. This could significantly enhance the utilization efficiency of the Pd catalyst in the material. Our strategy supplied a versatile method for the immobilization of different organometallic catalysts into the pores of PAFs, which will promote the development of PAF-based organometallic catalysts.Based on the mesoporous PAF (There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Strongly phosphorescent hetero-metallic [2]catenanes, including bimetallic scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6M6 (M = Ag or Cu), scale\" fill=\"currentColor\" stroke=\"none\">C)12Au10Ag2 and trimetallic scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6CunAgn6\u2013, were obtained. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligand; Dtbp = 3,5-di-tert-butylphenyl), Au\u2013Ag scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 ligand), and Au\u2013Cu, Au\u2013Ag scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 ligand; C6-Fluo = 9,9-dihexyl-9H-fluoren-2-yl) complexes as well as a trimetallic Au\u2013Ag\u2013Cu scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 ligand) complex, which feature [2]catenane structures. The formation of the [2]catenane structure is significantly affected by the coinage metal ion(s) and change of the structure of the alkynyl ligand. These hetero-metallic [2]catenane structures are strongly luminescent with tunable emission \u03bbmax from 503 to 595 nm and \u03a6 values up to 0.83.Homo-metallic metal alkynyl complexes exhibit interesting catenane structures, but their hetero-metallic catenane counterparts are under-developed. In this work, we report rare examples of bimetallic Au\u2013Cu (DtbpC Various strategies, including \u03c0\u2013\u03c0 stacking, hydrogen bonding, metal templating, and hydrophobic interactions, have been developed to direct the assembly of interpenetrated structures.n n = 10,) which fI-alkynyl catenanes is the presence of two linear RC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013Au\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCR units in the locking center. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013M\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCR species commonly seen in the literature,I\u2013alkynyl system, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 , 9,9-dihexyl-9H-fluoren-2-yl (C6-Fluo), or tBu) to construct novel assemblies of hetero-metallic alkynyl complexes. Herein, we described the formation of five hetero-metallic alkynyl [2]catenanes molar ratio, and the trimetallic complexes 3 and 6 were prepared by mixing the homoleptic gold, silver and copper alkynyl complexes in a 2\u2009:\u20091\u2009:\u20091 molar ratio or by mixing the hetero-metallic Au\u2013Cu and Au\u2013Ag alkynyl complexes in a 1\u2009:\u20091 molar ratio. Complexes 1\u20133 were also accessible from the reactions of alkynes with Au(SMe2)Cl, AgOTf and/or [Cu(MeCN)4]PF6 (2\u2009:\u20091\u2009:\u20091 for 1 and 2 and 3\u2009:\u20091\u2009:\u20091\u2009:\u20091 for 3) in the presence of Et3N (yields: 27\u201378%). X-ray diffraction-quality crystals of 1\u20137 were obtained by the slow evaporation of the CH2Cl2/MeCN, chlorobenzene or toluene/MeCN solutions and their structures were determined by X-ray crystallography scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Cu6, has a crystallographic D2 symmetry and features two twisted scale\" fill=\"currentColor\" stroke=\"none\">C)6Au3Cu3 rings that are interlocked to form a [2]catenane structure scale\" fill=\"currentColor\" stroke=\"none\">C\u2013Au\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCDtbp units and three Cu ions with relatively weak Au\u2013Cu (2.9632(10) \u00c5) and Au\u2013Au (2.9625(3)\u20133.1497(8) \u00c5) interactions .1- and \u03b72-modes, respectively. The M\u2013C distances (Au\u2013C 1.979(7)\u20132.009(6) \u00c5 and Cu\u2013C 2.018(7)\u20132.285(14) \u00c5) are comparable to those in the homo-metallic [2]catenane [ scale\" fill=\"currentColor\" stroke=\"none\">CAu)6]2 (Au\u2013C 1.85(4)\u20132.26(3) \u00c5)1 as a hetero-metallic [2]catenane. In contrast, the PhC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 counterpart of 1, scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Cu6, adopts a non-catenane structure in which the six AuI ions are co-planar and the six CuI ions form a trigonal prism with the PhC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligands situated on the two opposite sides, rendering the Ph groups (for each side) rather close to each other1 in the assembly/stabilization of the [2]catenane structure of the Au6Cu6 alkynyl complex. It is probable that the non-catenane structure of scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Cu6, upon changing its alkynyl ligands to the bulkier and more basic DtbpC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligands, is destabilized owing to the increased steric hindrance [resulting from the bulkiness of the electron-donating tBu substituents and stronger metal-alkynyl binding (cf. Au\u2013C 2.004(6)\u20132.045(5) \u00c5 in scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Cu6 (vs. 1.979(7)\u20132.009(6) \u00c5 in 1)], and as such the steric hindrance is minimized in the [2]catenane structure of the Au\u2013Cu complex 1.The Au\u2013Cu complex tructure . Each riu 2.88 \u00c5 ), which u (2.9632 \u00c5) and A12Au6Cu6 i vs. 1.9 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligand unchanged, a non-catenane complex scale\" fill=\"currentColor\" stroke=\"none\">C)16Cu8Ag8 (2) was obtained. Complex 2 has a structure with an approximate S4 symmetry scale\" fill=\"currentColor\" stroke=\"none\">C)16Au8Ag8, also with a non-catenane structure.3, its structure scale\" fill=\"currentColor\" stroke=\"none\">C)16Au8Ag8 molecule PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC)16Au8Ag8, 3 features central Au\u2013Au distance (Au2\u2013Au5 2.9591(9)vs. Au3\u2013Au7 3.1825(4) \u00c5) and substantially larger C\u2013M\u2013C angles (139.4(5)\u2013142.6(4)\u00b0 11vs. 172.4(3)\u2013177.0(4)\u00b0).By changing Au\u2013Cu to Cu\u2013Ag, but with the same DtbpCtructure features PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 from Dtbp to the bulkier C6-Fluo resulted in the formation of bimetallic scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Cu6 (4) and scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Ag6 (5) and trimetallic scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6CunAgn6\u2013 (6), and all of the three complexes adopt a [2]catenane structure scale\" fill=\"currentColor\" stroke=\"none\">C\u2013Au\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCCR units in 4\u20136 is similar to that in 1; the connection of the C6-FluoC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013Au\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC6-Fluo units by \u03c0-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013Cu/Ag coordination forms the [2]catenane structures. The Cu and Ag atoms in 6 are in substitutional disorder scale\" fill=\"currentColor\" stroke=\"none\">C\u2013M is partially occupied by Cu and Ag atoms, the occupancy of the Ag atom of the outlier positions 1 and 2 is slightly higher (4 and 5 used in the preparation of 6. The average Cu/Ag\u2013C(\u03b1) distance in 6 is 0.14 \u00c5 longer than the average Cu\u2013C(\u03b1) distance in 4 and 0.12 \u00c5 shorter than the average Ag\u2013C(\u03b1) distance in 5, while the difference of the average Au\u2013C(\u03b1) distances between 4\u20136 is <0.03 \u00c5.Changing the R group of RCtructure . The arrdisorder : each \u03c0-y higher , and the6 can be formed by mixing the [2]catenanes 4 and 5 in solution, we also mixed the previously reported [2]catenane [ scale\" fill=\"currentColor\" stroke=\"none\">CAu)6]2 scale\" fill=\"currentColor\" stroke=\"none\">CAg]n (molar ratio 5\u2009:\u20091), and obtained 7, adopting a [2]catenane structure similar to that of [ scale\" fill=\"currentColor\" stroke=\"none\">CAu)6]2 except for the replacement of one bis scale\" fill=\"currentColor\" stroke=\"none\">C) coordinated Au ion in each ring by one Ag ion (As [2]catenane CAu)6]2 with + scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 signals were observed at room temperature , which were broadened into one set upon increasing the temperature to 353 K and were then recovered by cooling back to room temperature scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 belong to a single complex (diffusion constant D = 8.32 \u00d7 10\u201310 m2 s\u20131), thus providing additional evidence for the purity of 1 in solution.We examined the solution behavior of the hetero-metallic [2]catenanes \u223c10\u20132 M, , three s1 as an example. The DFT-optimized geometry of 1 is comparable to that determined by X-ray crystal analysis. For example, the computed structure of 1 features average values of Au\u2013C 1.997 \u00c5, C\u2013Au\u2013C 176.2\u00b0, and Cu\u2013C 2.053 \u00c5; these values compare well with the corresponding ones in the crystal structure of 1 \u00c5, C\u2013Au\u2013C 176.9(8)\u00b0 and Cu\u2013C 2.097(7) \u00c5). To gain insight into why the [2]catenane of scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6M6 was obtained for M = Cu (1) but not for M = Ag, we attempted to perform DFT optimization of scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6Ag6 with a hypothetical similar [2]catenane structure, which did not converge. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of 1 are depicted in z2 orbitals of the two Au atoms in the locking center of the [2]catenane structure, while the LUMO is distributed on the empty 6p orbitals of the same two Au atoms.DFT calculations were performed to examine the electronic details of the hetero-metallic [2]catenanes using 1\u20137 are emissive in the solid state (1 and 4\u20136 exhibit moderate yellow to strong orange emissions in the solid state (\u03a6 = 0.37\u20130.83). Changing the ligand from DtbpC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 to C6-FluoC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 resulted in a bathochromic shift in emission energy and a significant improvement in the quantum yield. Notably, the emission energy and efficiency show only minor variation with the metal compositions of 4\u20136 . The comparison of the emission spectra of scale\" fill=\"currentColor\" stroke=\"none\">C)12Au8Ag8 . The excitation of 7 in the solid state gave a strong green emission at \u03bbmax 503 nm with a tail up to 710 nm (\u03a6 = 0.82). The wide span in emission energy (\u03bbmax from 503 to 595 nm) and high solid state emission quantum yields highlight the prospect of hetero-metallic [2]catenanes based on a coinage metal alkynyl system as useful photo-functional molecular materials.Complexes id state . In view= 489 nm b) and 3 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligand to result in the assembly of hetero-bimetallic and hetero-trimetallic [2]catenanes scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6M6 (M = Cu 4 and Ag 5) and scale\" fill=\"currentColor\" stroke=\"none\">C)12Au6CunAgn6\u2013 (6) is remarkable. As 4\u20136 are nearly isostructural, it appears that their C6-FluoC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligands dominate the intermolecular interactions, with the effect of the Ag and Cu ions being minor in these cases. As revealed by the crystal structures of 4 and 5, replacing the Cu ions with Ag ions slightly expands the metallacycle core owing to the longer Ag\u2013C than Cu\u2013C distances scale\" fill=\"currentColor\" stroke=\"none\">C\u2013 ligand with flexible C6-alkyl chains is likely to restrict such tendency. For the complexes of the DtbpC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligand, which is sterically less demanding and relatively rigid, the replacement of the Cu ions by Ag ions leads to a core enlargement from M12 (1) to M16 (3). On the other hand, an Ag ion, compared with a Cu ion, is a stronger Lewis acid and is inclined to form weak interactions with more alkynyl ligands scale\" fill=\"currentColor\" stroke=\"none\">C\u2013Ag interactions may distort the ring unit and then break the [2]catenane structure. Moreover, the preference of AuI for a linear two-coordinate configuration should also play an important role in the assembly of the hetero-metallic [2]catenanes in view of the core enlargement from M12 (1) to M16 (2), upon replacing the Au ions with Ag ions, and the presence of linear RC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013AuI\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCR units in all of the [2]catenanes 1, 4\u20136, and 7.The use of the C6-FluoC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013, C6-FluoC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013, and tBuC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013 ligands. The structure of the trimetallic [2]catenane 6 is analogous to its corresponding Au\u2013Ag bimetallic [2]catenanes with some of the Ag atoms replaced by Cu atoms; mixing the Au\u2013Cu and Au\u2013Ag complexes is a feasible and efficient method to prepare the trimetallic complex. The formation of [2]catenanes relies upon a delicate balance between various intermolecular interactions. The structural characterization of 1\u20137 provides useful insight into a better understanding of hetero-metallic coinage metal alkynyl complexes.We have prepared and structurally characterized five hetero-metallic [2]catenanes based on coinage metal alkynyl complexes, including bimetallic Au\u2013Cu and Au\u2013Ag complexes and a trimetallic Au\u2013Cu\u2013Ag complex, by employing bulky DtbpCThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The metal centre remains a spectator through the peripheral mechanism investigated by a combined spectroscopic, crystallographic, and computational analysis. ii) catalyst through oxidative addition of a hydrosilane. Neither the hydrogen atom nor the silicon atom bound to the iron(ii) centre are subsequently transferred onto the carbonyl acceptor, instead remaining at the sterically inaccessible iron(ii) atom throughout the catalytic cycle. A series of labelling, crossover and competition experiments as well as the use of a silicon-stereogenic hydrosilane as a stereochemical probe suggest that the iron(ii) site is not directly involved in the hydrosilylation. Strikingly, it is the silyl ligand attached to the iron(ii) atom that acts as a Lewis acid for carbonyl activation in this catalysis. The whole catalytic process occurs on the periphery of the transition metal. Computation of the new peripheral as well as plausible alternative inner and outer sphere mechanisms support the experimental findings.Combined experimental and theoretical analysis of the carbonyl hydrosilylation catalysed by an iron(0) pincer complex reveals an unprecedented mechanism of action. The iron(0) complex is in fact a precatalyst that is converted into an iron( Iron-catalysed carbonyl hydrosilylation can be traced back to seminal reports by Brunnerinner sphereouter sphereinner sphere mechanisms with \u03c3-bond-metathesis-type Si\u2013H bond cleavage at an iron\u2013oxygen bondouter sphere mechanisms with iron acting as a Lewis acid,Mechanisms of transition-metal-catalysed hydrosilylations exhibit a wide variety of modes of activation.1 and 2 (ii) hydride in 1 was postulated to be relevant in the catalytic cycle.2 was, in turn, believed to be a precatalystinner nor outer sphere but on the periphery of the metal centre without its direct involvement.Driess and co-workers recently introduced silylenes as \u03c3-donor ligands in iron-based catalysis, and iron(0) complexes 1 and 2 were app2 (2.5 mol%) was found to catalyse the hydrosilylation of various acetophenones 3a\u20133i with silane 4a at elevated temperatures2N group in the para position (entry 2). The reaction was, however, sensitive toward steric hindrance. Substituents in the ortho position significantly lowered the yield (entries 7\u20139), and a 2,6-disubstituted substrate did not react . Benzophenone reacted readily while propiophenone and isobutyrophenone afforded 18 and 16% yield, respectively. Hydrosilylation of cyclopropyl substituted ketone proceeded efficientlyThe SiNSi pincer complex 2 and hydrosilanes 4a\u2013c suitable for X-ray diffraction analysis, and that confirmed the molecular structure deduced from the NMR analysis. The structure shows a distorted octahedral iron(ii) coordination environment. The hydride was located tilted toward one of the silylene donor arms deviated from the trans coordination to the Me3P ligand (P\u2013Fe\u2013H1 170.20(5)\u00b0), a situation similar to that of known iron(ii) hydride pincer complexes.t-Bu groups encage the iron hydride with a Si1\u2013Fe\u2013Si2 angle far from the linearity, 144.54(3)\u00b0.To gain insight into the mechanism, we investigated the reaction between iron(0) complex ii) complex 7 is the active catalyst, we measured the kinetic profiles for the hydrosilylation of 3a with hydrosilane 4a catalysed by 2 or 7a complex 7 as the active catalyst.To validate whether the thus formed iron( 2 or 7a . Conversii) hydrides 7 in hand, we had a closer look at the hydride transfer. Maintaining 7b and deuterium-labelled hydrosilane 4b-d1 in THF at 70 \u00b0C resulted in slow H/D exchange, visible both at the silicon and iron atoms (ii) hydride 7b, hydrosilane 4b-d1 (>95% deuteration grade), and ketone 3e was puzzling though yielded 8eb with little deuterium incorporation at 19% conversion (H/D = 90\u2009:\u200910). That ratio subsequently decreases to 78\u2009:\u200922 to reach equilibrium after 24 hours. These results reveal that even though the hydride at the silicon atom in 4 is exchanging with the iron-bound hydride in 7, hydride transfer to the carbonyl carbon atom of 3 most likely occurs from the hydrosilane 4 and not from complex 7.vide infra).With the iron hydride 7b indeed led to H/D scrambling. Conversely, no erosion of the enantiomeric purity was seen when subjecting enantiopure silyl ether (S)-8eb to the typical protocol -8eb suggests that the hydride transfer itself is irreversible, and a concerted mechanism involving frontside attack at the asymmetrically substituted carbon atom is needed to explain the hydrogen atom exchange between the catalyst and the product.The possible H/D exchange at the methine position of silyl ether g 8eb-d1 , top. Trvia a silylene-assisted concerted mechanism are energetically accessible under the reaction conditions.After the transition state, the silylene-bound hydrogen atom migrates back to the silicon and carbon atom, respectively. The activation barriers of the scrambling reactions 3P (6-d9) was observed did not lead to the formation of the silyl ether 8eb is significantly slower in the presence of ketone 3e. The formation 11 was also investigated computationally POCOP-pincer complex is thwarted by additional Me3P (6), indicating dissociation of one of the phosphine ligands as part of the catalytic cycle.3P to the reaction mixture, the reaction was unaffected catalyses the hydrosilylation of 3e with MePh2SiH (4c) with hardly any incorporation of the Me2PhSi moiety into the product; silyl ether 8ec rather than 8eb is formed almost exclusively (ii) complexes 7 are the actual catalysts, originating from oxidative addition of hydrosilanes 3 to the iron(0) complex 2; 2 is a precatalyst. During the crossover experiment no changes in the characteristic signals of complex 7b in the 1H and 31P NMR spectra were detected. However, when the assumed inability of 7b and 4c to exchange their silyl groups was examined with another control experiment were observed, indicating that the exchange (7b to 7c) is in fact a side product of the decomposition rather than simple scrambling of the silyl groups.As is to be expected from the above observations, the hydride complex lusively , right. 7b promoted the reaction between highly enantioenriched hydrosilane (SiS)-4d (e.r. > 95\u2009:\u20095) and ketone 3e but conversion was slow as expected from the data obtained with achiral triorganosilane 4b -8ed in 31% yield; diastereoselection was poor. The enantiomeric ratio of unreacted (SiS)-4d was found to be unaffected. Subsequent reductive cleavage of the Si\u2013O bond in (SiR)-8ed (known to proceed with stereoretention at silicon atomSiS)-4d with overall retention of the stereochemistry at the silicon atom (e.r. > 95\u2009:\u20095). Hence, the hydrosilylation step involves frontside attack at the silicon atom, and that makes a mechanism involving Lewis-acid activation of the hydrosilane unlikely.18With sufficient knowledge of the active catalyst, we decided to analyse the stereochemical course at the silicon atom of the reacting hydrosilane .18 Catalii) catalyst 7 is generated from the iron(0) precatalyst 2 by oxidative addition of hydrosilane 4 to the zero-valent iron atom (ii) centre in 7a (grey box), we did not locate any structure resulting from direct insertion of the ketone C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group into the iron hydride 7a or the silylene ligands (not shown). Instead, we were able to find a minimum structure for the phosphine-dissociated complex cis-14a . The intermediate cis-14a readily coordinates THF forming the adduct 17a. This intermediate is however a resting state if not a \u201cmechanistic dead-end\u201d. Ketone coordination to the iron centre of cis-14a gives intermediate 19oa with activated carbonyl group. The catalytic cycle is closed by an outer sphere concerted hydrosilane addition \u202120oa to the ketone with an activation barrier of 33.7 kcal mol\u20131.Based on the combined findings, we propose that the active iron to afford the iron alkoxide 25oa. The silylated alcohol is released by an inner sphere silylation through \u202126oa with an energy barrier of 34.9 kcal mol\u20131. An alternative inner sphere mechanism could be a reductive elimination from the intermediate 25oa. However, the energy barrier for the transition state \u202127oa was found to be high, and the resulting iron(0) complex 28 is energetically disfavoured. Recoordination of phosphine 6 gives iron(0) complex 29 which oxidatively adds to a silane 4a to form 7a.Isomerisation of ficantly , right. outer nor inner sphere mechanisms give satisfactory fits to the experimental evidence. Hence, we looked for an adduct of 7a and 3o wherein the silyl group would act as a Lewis acid led to intermediate 31oa with a pentacoordinate silicon atom, and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bond being significantly elongated compared to its equilibrium distance from 1.211 to 1.251 \u00c5, indicating activation.4a to the carbonyl group in 31oa, and the hydrosilylation event releases 8oa through transition state \u202132oa with retention at the silicon atom. In accordance with our labelling experiments (cf.\u20131). To further validate this, we conducted a competition experiment between electron-rich 3a and electron-deficient 3f is more positively polarised accelerating the hydride transfer, than that of donor-substituted 3a (X = OMe). The reactivity is also in agreement with the proposed KIE based on the control reactions with deuterated silane 4b-d1 (In addition to the high energy barriers, neither wis acid .8,18,20 ments cf., this iscient 3f . The parne 4b-d1 .i.e., on the periphery of the transition metal. Coincidentally, the mechanism becomes outer sphere at silicon.inner or outer sphere mechanisms do not apply to this unique catalyst.The value of the present study is that it demonstrates, to our knowledge for the first time, an unusual case where the transition metal of a catalyst complex is not directly involved in the catalytic process. Activation of both substrate and reagent as well as the bond-forming and -breaking events happen in the ligand sphere, Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO\u2013 and GSH (GSH-PF3). \u2013 and GSH (GSH-PF3). The GSH-PF3 probe was synthesised over three steps starting from commercially available fluorescein. The probe was constructed by attaching the GSH reactive motif, 2,4-dinitrobenzenesulfonyl, to the previously reported boronate fluorescence based probe, PF3. GSH-PF3 produced only a small fluorescence response towards the addition of GSH or ONOO\u2013 separately. However, when the probe was exposed to both analytes, there was a significant (40-fold) fluorescence enhancement. GSH-PF3 demonstrated an excellent selectivity towards both GSH and ONOO\u2013. In cellular imaging experiments the probe was shown to be cell permeable with no \u2018turn-on\u2019 response observed for the addition of either GSH or ONOO\u2013 separately. However, in the presence of both analytes, a clear fluorescence response was observed in live cells. GSH-PF3 was further able to monitor the co-existence of metabolically produced ONOO\u2013 and GSH by exogenous stimulation.We have developed a novel AND logic based fluorescence probe for the simultaneous detection of ONOO GSH is the predominant form, existing at millimolar concentrations in most cells.\u2013 therefore acting as a cellular defence by serving as an ONOO\u2013 scavenger. Elevated levels of GSH are common in cells under oxidative stress and the susceptibility of a cell towards ONOO\u2013 largely depends on the concentration of intracellular GSH.Peroxynitrite and reduced by GSH (turn \u201coff\u201d). The fluorescence of the CyPSe probe is initially quenched by a photoinduced electron transfer (PET) process. The presence of ONOO\u2013 results in the oxidation of selenium to CyPSe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO causing the fluorescence emission to be \u201cturned on\u201d. Then in the presence of biological thiols such as cysteine and GSH, the CyPSe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO probe is reduced back to its non-fluorescent selenide form. A similar reversible NIR Tellurium-based fluorescence probe was later developed for monitoring the redox cycles between ONOO\u2013 and GSH. This probe was successfully applied for the visualisation of the redox cycles of ONOO\u2013 and GSH in live cells and animals.et al. are turn \u201con\u201d with ONOO\u2013 and \u201coff\u201d with GSH. As far as we are aware, there are currently no AND logic based fluorescence probes for GSH \u201cand\u201d ONOO\u2013.Currently, only a few reversible fluorescence based probes for the detection of ONOO\u2013 logic based fluorescence probe and H2O2.PF3 would produce a selective GSH-ONOO\u2013 AND logic based fluorescence probe, GSH-PF3 (GSH-PF3 was readily synthesised in three steps. Fluorescein was triflated using N-phenyl bis(trifluoromethanesulfonamide) to afford fluorescein mono-triflate in good yield. Suzuki\u2013Miyaura conditions were then carried out to provide fluorescein mono-boronate, PF3. The 2,4-dinitrobenzenesulfonyl unit was then attached to PF3 using 2,4-dinitrobenzenesulfonyl chloride, CH2Cl2 and NEt3 at 0 \u00b0C. Using these conditions GSH-PF3 was prepared in a reasonable yield of 52%.With this research, we aimed to develop a GSH \u201cand\u201d ONOOce probe . We iden GSH-PF3 . GSH-PF3GSH-PF3 in hand, fluorescence experiments for the detection of GSH and ONOO\u2013 were performed. As shown in GSH-PF3 was initially non-fluorescent and with the addition of ONOO\u2013 (10 \u03bcM), a small fluorescence increase was observed. However, incremental additions of GSH resulted in a much larger increase in fluorescence intensity was added to GSH-PF3, and the probe was incubated for 10 min. Remarkably, this only led to a small increase in fluorescence intensity and the subsequent additions of ONOO\u2013 resulted in a large fluorescence increase \u2013 see ESI Fig. S3.GSH-PF3 displayed an excellent selectivity against other amino acids including serine, methionine and lysine. The probe demonstrated excellent selectivity for ONOO\u2013 over many other ROS including H2O2 \u2013 or by addition of exogenous GSH. As shown below in \u2013 led to a small fluorescence response in cells. This observation is believed to be due to the presence of a low levels of endogenous biological thiols in the cells, resulting in the activation of the probe's fluorescence. As predicted, treatment of cells with both GSH and SIN-1 led to a clear fluorescence increase in RAW264.7 cells with GSH-PF3, in clear agreement with the analytical data obtained on the fluorimeter.The macrophage cell line \u2013 RAW264.7 \u2013 was used for cell imaging experiments. The cells were incubated with GSH-PF3 for monitoring the co-existence of metabolically produced ONOO\u2013 by lipopolysaccharide (LPS) simulation\u2013 in macrophage, which is a signature of inflammation, whereas caffeic acid (CA) is commonly used to treat inflammation through the augmentation of intracellular GSH. Consequently, treatment with LPS, followed by the addition of increasing CA (0\u2013100 \u03bcM) led to a gradual enhancement in the fluorescence intensity of GSH-PF3 led to the suppression of probe's fluorescence, which is believed to be due to the production of an excess of GSH, resulting in quenching of the ONOO\u2013 , since it is known that high levels of ONOOGSH-PF3 is an easy-to-prepare fluorescence based probe providing a platform for the development of other novel AND logic based fluorescence imaging probes for use in medical diagnostics. We are currently exploring the use of 6-amino/carboxyfluorescein, which we believe could provide the opportunity to attach additional fluorophores in order to develop ratiometric fluorescence sensorsIn summary, No conflicts of interest.Supplementary informationClick here for additional data file."}
+{"text": "Thioamide substitution into macrocyclic peptides increases the conformational rigidity of the backbone resulting in enhanced biological activity and metabolic stability. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS group and the surrounding atoms are the major driving force in inducing the conformational restriction, resulting in well-defined structures of these cyclic peptides with static 3-D presentation of the pharmacophores. Utilizing this property of thioamides, we report the development of a superactive antagonist of pro-angiogenic \u03b1v\u03b23, \u03b1v\u03b25 and \u03b15\u03b21 integrins, which are responsible for cancer cell proliferation and survival. Using simple thio-scanning and spatial screening of a non-efficacious and conformationally flexible cyclic peptide, we could achieve a more than 105 fold enhancement in its efficacy in cellulo via a single O to S substitution. The developed peptide shows better efficacy in inhibiting the pro-angiogenic integrins than the drug candidate cilengitide, with a significantly enhanced serum half-life of 36 h compared to that of cilengitide (12 h). The long shelf-life, absence of non-specific toxicity and resistance to degradation of the thioamidated macrocyclic peptides in human serum suggest the promise of thioamides in markedly improving the affinity, efficacy and pharmacology of peptide macrocycles.We show that substituting a single atom, O to S (amide to thioamide), in a peptide bond results in global restriction of the conformational flexibility in peptide macrocycles with minimal perturbation of the parent conformation. The van der Waals interactions between the C The high-resolution structures of the thionated cyclic pentapeptides indicated the coexistence of \u03b2II\u2032-type and \u03b3-type turns. The \u03b3-type turn is in equilibrium between an open (indicated by the NOE between the Ala4HN\u2013Ala5HN protons) and a closed form with similar global conformations but different \u03c6 and \u03c8 values (ESId-Ala1\u2013Ala2 and the \u03b3-turn is centered about Ala4.3 resulted in a conformation with the \u03b2II\u2032-type turn centered about Ala2\u2013Ala3 and the \u03b3-turn centered about Ala5 (3).To initially determine the conformational impact of thioamide substitution in peptide macrocycles, we synthesized a regioisomeric library of monothionated analogs of the parent cyclic peptide cyclo(\u2013ype turn .14 The 1ation ESI. Utiliziation ESI. The int bonding ) as demo1.000000,.000000 salues ESI, where t1.000000,.000000 s PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups in the cyclic pentapeptide are at d-Ala1, Ala2 and Ala4, and upon thionation did not perturb the conformation of the parent peptide. However, thionation at the internally oriented C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups, in the case of Ala3 (3), completely changes the conformation of the peptide; this is also observed for Ala5 (5), albeit to a lesser extent. These results indicate that thioamide substitution at a site where the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group does not engage in intramolecular hydrogen bonding can retain the conformation of the parent macrocyclic peptide. Thus, we note that thioamides can be valuable probes for identifying the hydrogen bond involved in stabilizing the conformation of a macrocycle.3 and wondered whether this was a result of the enhanced hydrogen bond (H-bond) donating properties of the thioamide, as noted by Kessler et al.1H chemical shifts. The upfield shift of the amide resonances in Ala3HN and Ala5HN indicate their involvement in intramolecular hydrogen bonding, as opposed to d-Ala1HN, Ala2HN, and Ala4HN in all the peptides except 3 Cept 3 ESI.2HN being involved in a \u03b3-turn with Ala5CO in 1,2 and 4 did not indicate a significant increase in the thioamide H-bond donation. This suggests that the increased thioamide H-bond donor propensity3 and 5, instead, the van der Waals interactions between S scale\" fill=\"currentColor\" stroke=\"none\">S bond) and the surrounding atoms are crucial in dictating the conformation of the peptide, as predicted from the computational studies of thioamides containing dipeptides by Lipton et al.3CO completely flips outward on thio substitution in 3, presumably due to the 1,2 and 1,3-diaxial strain between S and the flanking Ala3 and Ala4C\u03b2. However, owing to the flanking heterochiral residues, thio substitution of Ala5CO allows for a partial flip of the thioamide bond.It was interesting to note that despite the possibility of Ala13C spin-lattice relaxation time (T1) of the backbone C\u03b1 in these cyclic peptides, which provides qualitative information on the segmental motion of amino acids in peptides.i + 1 residue in the \u03b2-turn displayed the lowest T1 compared to the other residues in the same macrocycle indicating its segmental rigidity (T1 is not feasible due to differences in the concentration and viscosity of the samples).T1 of the i + 1 residue with the T1 of the alanine about which the flexible \u03b3-turn is centered structural rigidity in cyclic peptides.To understand whether the thioamide substitution results in reduced flexibility of the cyclic peptide backbone, we determined the rigidity (compari6),d-Phe\u2013Val and a \u03b3-turn about Gly as observed in 1. Interestingly, we noted that 6 displays two conformations in the ratio 1\u2009:\u20092 on the NMR time scale .t) (8) underwent spontaneous acid catalyzed degradation.t), c(KGDfVt) and c(NleGDfVt) (Nle: norleucine). It was surprising to note that all of these protected cyclic peptides underwent spontaneous acid catalyzed degradation as observed in 8 (ESI1\u20135) did not show any trace of thio to oxo conversion even after 24 months at 25 \u00b0C in DMSO solution, indicating the stability of the thiopeptides in an oxidizing environment.To validate our observation of enhanced structural rigidity in peptide macrocycles through thionation in aqueous solution , we resorted to a moderate affinity cyclic peptide integrin antagonist cyclo(RGDfV) scale\" fill=\"currentColor\" stroke=\"none\">S group and not the improved thioamide H-bonding ability.9, its temperature coefficient is \u20136.8 ppb K\u20131, indicating the absence of intramolecular hydrogen bonds, as opposed to d-PheHN (\u20132.4 ppb K\u20131) and ArgHN (\u20131.6 ppb K\u20131), which are involved in \u03b3-turns (11 (d-PheHN) is also solvent exposed (\u20135.0 ppb K\u20131) and was not involved in stabilizing the \u03b3-turn about Asp with GlyCO.To demonstrate the uniform behavior of the thioamides in dictating the conformation of the cyclic peptide, we analyzed the solution conformations of 7\u201311 . It was \u03b3-turns . LikewisN-methylation, which introduces severe conformational heterogeneity into macrocyclic peptides via cis\u2013trans isomerism ,cis\u2013trans rotational barrier of the thioamide bond.3 and 9), the structural rearrangement results in a parent-like conformation, but with an altered side chain identity. These two observations suggested that (i) thioamides are valuable tools to reduce the conformational entropy in peptide macrocycles and (ii) thioamide substitution is an ideal modification for spatial screeningWe were quite excited to observe that unlike N-methylated cyclic peptide, cilengitide (Cilen), unfortunately failed in phase III clinical trials against glioblastoma.24To validate our hypothesis and demonstrate the potential of thioamides in delivering selective and high-affinity ligands, we chose to target the cell-adhesion receptors, integrins.in vitro competitive solid phase binding assay.6, showed a moderate affinity towards the pro-angiogenic integrins due to the conformational flexibility, which does not allow the static presentation of the pharmacophores responsible for tight binding. On the contrary, the conformationally rigid thio analogs yielded very interesting results. 7, which can be directly compared with Cilen, where an N-methylated amide bond is substituted with a thioamide bond, displayed a higher IC50 than 6 against \u03b1v\u03b23. However, remarkably it showed a better IC50 than Cilen against \u03b1v\u03b25 and \u03b15\u03b21 in the in vitro assays with purified integrins.The inhibitory potency of the peptides to block the association between the extracellular matrix and the integrins overexpressed on cell-surfaces was determined using an in vitro data and determine the efficacy of the peptides against the pro-angiogenic integrins in a complex cellular milieu, we subjected the peptides to a competitive cell-adhesion assay . This suggests the high specificity and selectivity of the thioamidated analogs towards the pro-angiogenic integrins in the presence of complex cellular components, which can otherwise sequester the peptides, reducing their efficacy.To validate our on assay utilizin7 strongly competed with vitronectin (Vn) in inhibiting the adhesion of MDA-MB-231 cells, suggesting its strong affinity towards \u03b1v\u03b25. A relatively lower potency of 7 was observed when inhibiting U-87 MG cell-adhesion to Vn (Vn binds to \u03b1v\u03b23 and \u03b1v\u03b25),7 towards \u03b1v\u03b23. 11 was the other member of the thio-scan library that showed better affinity than 6 towards the pro-angiogenic integrins in vitro, which was also reflected by its efficacy in the cell-adhesion assay.We were quite excited to note that as detected in the solid phase assay, 9 with thionation at Arg, which led to a complete reshuffling of the residues about which both the turns in 9 were centered affinity and efficacy of 9b in comparison to 9, by simple alteration in the spatial positioning of the pharmacophores on the thioamide backbone. To emphasize the effect of thio substitution, we synthesized compound 12 on the NMR time scale, as observed in 6, whereas 9b showed a single conformation, further reinforcing the rigidifying role of thioamides in peptide macrocycles.The spatial screening of in 9a\u20139d , of whicg of 9b) , which s9 and the spatial screen analogs (9a\u20139c) were comparable, except for 9d, which did not undergo the conformational switch scale\" fill=\"currentColor\" stroke=\"none\">S group and the surrounding atoms are critical in dictating the conformation of thioamidated macrocycles.Interestingly, the backbone conformations of l switch . This isin vitro and in cellulo activity of the synthesized peptides between H\u03b5 of Phe and one of the carboxylate oxygens of (\u03b2)-Asp126 . . in vitr)-Asp126 . The C\u2013H11. However, the lower potency of 11 stems from the loss of some crucial interactions with the receptor mediated by the \u2013RGD\u2013 motif scale\" fill=\"currentColor\" stroke=\"none\">S group compared to the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group.32The docked poses of all the other thioamidated peptides do not show such a C\u2013H\u00b7\u00b7\u00b7O interaction, except for motif ESI. Likewis9b and 7, which differ only in the chirality about the phenylalanine, show comparable affinity for \u03b1v\u03b25 and \u03b15\u03b21, but >103 fold difference in \u03b1v\u03b23 affinity. Docking of 7 revealed that this difference is due to the smaller distance between Arg and Asp C\u03b2 compared to Cilen and 9b, leading to the loss of end-on hydrogen bonding between Arg and (\u03b1)-Asp150 -Asp150 and the )-Asp150 . This re mode ESI. The comCilen was required to achieve the half maximal inhibitory concentration (IC50). This clearly suggested that incorporation of thioamides into macrocyclic peptides does not result in unspecific cytotoxicity even after 48 h, which is an important concern for the use of thioamides in lead design. We also noted that glioblastoma cells were more sensitive towards these antagonists than breast cancer cells, presumably due to the expression of all the pro-angiogenic integrins, despite the known resistance of U-87 MG cells against detachment-induced apoptosis.6 and 12 displayed minimal detachment-induced apoptosis in breast cancer cells compared to the potent thioanalogs.Since integrin antagonists are known to inhibit the proliferation of cancer cells,Cilen (N-methylated peptide) and the most potent thioanalogs in human serum ex vivo for 72 h (6 showed slightly better metabolic stability (t1/2: 9 h) than 12 (t1/2: 7 h) due to the presence of d-Phe. It is interesting to note the significant improvement in metabolic stability of all the thioamidated analogs throughout the course of the experiment as observed previously in linear thionated peptides.11 and 9b showed a significantly improved serum half-life (t1/2: 36 h each) compared to that of the clinical candidate Cilen (t1/2: 12 h). These data collectively suggest that thioamidation could have a stronger influence in improving the metabolic stability of macrocyclic peptides than d-amino acid incorporation.One major drawback to translating peptides as drugs is their inherent metabolic instability due to the action of endo- and exoproteases.for 72 h . As expe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO to C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS substitution in peptide macrocycles dramatically reduces the conformational flexibility while minimally perturbing the global conformation as observed in the model alanine, thio-scan and spatial screen integrin antagonists. Thus, thioamide incorporation leads to predictable changes in the conformation of the peptide backbone, unlike other amide bond modifications. Thioamide incorporation fine tunes the 3D-pharmacophore orientation, which qualifies thioamides as important bioisosteric mimics of peptide bonds.in vitro and in cellulo data against the pro-angiogenic integrins demonstrates the specificity of these thioamidated macrocyclic peptides against their endogenous target, which can be extended to other bioactive peptides as well. Thioamidated macrocyclic peptides are non-cytotoxic and, presumably due to their marked conformational rigidity, display enhanced stability against degradation by proteases,36In summary, we have demonstrated that macrocyclic peptides exhibit conformational flexibility in both apolar and polar environments (integrin antagonists), which tends to reduce their bioactivity.10, the conformational restriction imparted by the thioamidation of glycine is also predicted to stabilize the local conformation in the vicinity of the active site in methyl-coenzyme M reductase, leading to the increased half-life of the protein.i.e. conformational flexibility and metabolic instability, will accelerate the discovery of peptide-based drugs and antibacterials.in vivo and are currently being investigated.It is curious to note that few thioamide containing peptide natural products, such as thioviridamide, thioholgamides, and their related analogs,There are no conflicts of interest to declare.Supplementary informationClick here for additional data file."}
+{"text": "Treatment of an anionic dimanganaborylene complex with cationic coinage metal complexes led to the coordination of the incoming metal and displacement of dimethylsulfide in the formation of hexametalladiborides. 2Mn}2B]\u2013) with coinage metal cations stabilized by a very weakly coordinating Lewis base (SMe2) led to the coordination of the incoming metal and subsequent displacement of dimethylsulfide in the formation of hexametalladiborides featuring planar four-membered M2B2 cores comparable to transition metal clusters constructed around four-membered rings composed solely of coinage metals. The analogies between compounds consisting of B2M2 units and M4 units speak to the often overlooked metalloid nature of boron. Treatment of one of these compounds (M = Cu) with a Lewis-basic metal fragment (Pt(PCy3)2) led to the formation of a tetrametallaboride featuring two manganese, one copper and one platinum atom, all bound to boron in a geometry not yet seen for this kind of compound. Computational examination suggests that this geometry is the result of d10\u2013d10 dispersion interactions between the copper and platinum fragments.Treatment of an anionic dimanganaborylene complex ([{Cp(CO) Dating from the early work of Lipscomb and fellow main group pioneers, the bonding arrangements behind the clustering of boron atoms into three dimensions has been methodically explored.The relationship between molecular clusters and solid state materials has drawn interest and engendered discussions.2Mn}2B]\u2013, 1). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tMn] unit of the borylene either in a position equidistant from the two Mn centers, in an arrangement held together by intermetallic bonds between the incoming metal and Mn, or spanning one of the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tMn bonds, using the \u03c0-system as a side-on ligand with interactions roughly described by the Dewar\u2013Chatt\u2013Duncanson bonding model , 1,3-bis(4-tolyl)imidazol-2-ylidene (ITol), and 1--3,3,5,5-tetramethylpyrrolidin-2-ylidene (CAAC), had a direct influence on the bonding preferences of their accompanying coinage metals. Despite the observed differences, each of the three ligands explored in Which of these bonding geometries a complex took, was found to depend on the combination of the metal's identity and its stabilizing base. The magnitudes of both the \u03c3-basicity and \u03c0-acidity of the three ligands studied, tricyclohexylphosphine . As this chemical shift fell near the range established as normal for trimetallaborides (\u223c209\u2013216 ppm),To assess the effects of a highly \u03c3-acidic metal stabilized by a weak \u03c3-donor, we synthesized AuCl and CuCl stabilized by dimethyl sulfide (DMS) and reacted each with 1 . In both2 and 3 consist of planar M2B2 units with [Cp(CO)2Mn] fragments bridging each M\u2013B bond, alternating in positions above and below the M2B2 plane. This framework is reminiscent of a class of transition metal cluster complexes constructed around homometallic four-membered planar cores of naked coinage metal ions, with each M\u2013M bond similarly bridged by a transition metal fragment.162 and 3 can be directly compared to two such compounds, the Cu4[(CO)4Co]4 and Au4[Cp(CO)2Mo]4 clusters reported by Kl\u00fcfers and Braunstein, respectively and 2.8030(9) \u00c5. The Cu\u2013Cu bond length in 2 (2.4730(5) \u00c5) is substantially shorter than the edge Cu\u2013Cu bonds found in Kl\u00fcfer's complex (2.703(4)\u20132.731(4) \u00c5), and even shorter than bonds comprising various triangular arrangements of Cu atoms (\u223c2.58\u20132.67 \u00c5),Both ectively .16b,e Thi.e., open valence shells, Lewis acidity, lower electronegativity than hydrogen, etc.) have been noted, and comparisons have been drawn between the chemical behaviors of boron and metals, both in bulk materials and discrete molecules.3Fe3-core of a [FeBH2]3 compound reported by Walter ,The mimicry of the coinage metals by boron is interesting. Despite its position on the periodic table within the span occupied by elements commonly thought of as \u201cmetalloids\u201d, boron has most often been treated solely as a non-metal.2 and 3 are assumed to follow a pathway involving the initial formation of the triangular trimetallaboride complex (DMS1\u00b7M) followed by loss of DMS and dimerization . In contrast, the analogous release of an N-heterocyclic carbene ligand or simple phosphine from a the Au complex requires 33.2 kcal mol\u20131 (IMe) and 20.7 kcal mol\u20131 (PMe3), and 30.3 kcal mol\u20131 (IMe) and 18.5 kcal mol\u20131 (PMe3) from the Cu complex. As the \u0394G values for the dimerization of two liberated fragments in the formation of 2 and 3 are \u201323.9 and \u201327.8 kcal mol\u20131, respectively, the process of ligand-loss and subsequent dimerization is only downhill for the DMS-bound metals, explaining the fact that such dimerization has not been previously observed in reactions with either phosphine- or NHC-stabilized trimetallaborides. The treatment of 2 and 3 with PCy3 led to separation of each complex into two equivalents of PCy31\u00b7M, in line with the calculated thermochemistry. The computed energies of each compound are compiled in Table S1.The syntheses of rization . Dative 1 for Cu , leaving01\u00b7M complexes are themselves stronger ligands for open coordination sites on coinage metal cations than DMS, but weaker ligands than NHCs or phosphines. Such reactivity, of course, requires them to be amphoteric in a Lewis sense. In the case of Au, these fragments are in the proper orientation for direct dimerization via simple HOMO/LUMO interactions 2. The addition of two equivalents of Pt(PCy3)2 to a toluene solution of 2 led to the formation of a new product with an 11B NMR peak at 215 ppm. Crystallographic isolation indeed showed the splitting of 2, but instead of addition to the Lewis acidic Cu atom, Pt(PCy3)2 was found to have donated one phosphine to Cu and inserted along the adjacent Mn\u2013B bond, immediately next to Cu, yielding a tetrametallaboride , The easy separation of 4 along the plane formed by the B, Cu and Pt atoms (2. An abbreviated structure 2* (the ligand architecture has been removed from two of the four Mn atoms) is displayed with the line-of-sight along the Cu\u2013Cu\u2013B plane. The above- and below-plane positions of Mn1 and Mn2 in 4 mimic the positions of Mn1 and Mn2 in 2*, while Mn3 and Mn4 in 2* have been replaced by PCy3 ligands in 4. This observation lends support to the notion that B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tMn \u03c0-bonds, such as those in 1, may act as \u03c3-donating side-on ligands in their interactions with metals.A view of compound Pt atoms shows th1 coordinated to Pt(PCy3) and Au(ITol)+ has been reported, but in an altogether different geometry.5) was formed through the reaction of [{Pt(PCy3)}{Cp(CO)2Mn}2B]\u2013 (6)3\u2013CuCl and 6 again yielded 4 (eqn (3)). When the ligand on copper was changed for an NHC (ITol\u2013CuCl) the same reaction (eqn (4)) led to the formation of a new product with an 11B NMR peak at 226 ppm, close to the shift reported for 6 (224 ppm). Single crystal X-ray analysis confirmed the distorted planar geometry of the boride, with the platinum fragment situated symmetrically between the Mn atoms, and the Cu bridging one of the two B\u2013Mn bonds scale\" fill=\"currentColor\" stroke=\"none\">Mn \u03c0-bond and participates in back bonding with a \u03c0* orbital + fragment bridges the B\u2013Mn1 bond in an arrangement typical of Class A bonding, while on the other the Pt(PCy3) fragment adopts a Class B geometry, bending the [Mn\u2013B\u2013Mn] backbone (168.2(3)\u00b0) to maximize intermetallic bonding of both Mn1 and Mn2 with Pt. As was found typical of Class A bonding, the Cu-bridged Mn1\u2013B bond (1.970(5) \u00c5) was elongated with respect to the Mn2\u2013B bond (1.907(5) \u00c5). As typical for Class B bonding, the Mn1\u2013Pt (2.707(1) \u00c5) and Mn2\u2013Pt (2.731(1) \u00c5) bonds were similar, and both shorter than the sum of the covalent radii of Mn and Pt (2.75 \u00c5) as determined by Cordero.As mentioned, we recently described two different bonding motifs assumed by d orbital , Class An number , Class B3) fragment as Lewis acidic is at odds with previous descriptions of the behavior of this fragment in similar trimetallaborides. Calculations on a compound composed of a Pt(PCy3) fragment complexed to a dimetallaborylene backbone consisting of a boron atom between iron and platinum (3) as a Lewis base stabilizing an electrophilic boron.7 are both shorter than the sum of covalent radii, the Pt\u2013Pt distance in the complex with the [Fe\u2013B\u2013Pt] backbone is roughly 3.3 \u00c5, significantly longer than the 2.72 \u00c5 sum of covalent radii, indicating little metallophilic interaction between the incoming Pt(Cy3) fragment and the Pt in the borylene backbone. Subsequent reports from our group used this description of Pt(Cy3) as a base in conjunction with the [Mn\u2013B\u2013Mn] backbone;This description of the Pt, the cve is tabulated as 98. If instead the four lighter metals (Mn) use 9 AO and two heavier metals (Cu and Au) use 8 AO, the cve counts become 94. Cluster 4 is unique in that it possesses 60 cve; however, if the same approach is applied as for 2 and 3, it yields 66 cve, in the case where all metals use 9 AO, and 62 when Mn uses 9 and Pt/Cu use 8 AO. The extra electrons are perhaps more localized on the metal centers and thus are not involved in skeletal bonding. It is common for heavier transition metals, e.g. Pt and Au, to form complexes with either 16 or 14 valence electrons,2\u20134.The comparison made in 4 and 7 are perplexing. It is perhaps attractive to view the systems as examples of four-coordinate boron exiting in both distorted planar (7) and distorted tetrahedral (4) geometries; however, the distortions from ideal tetrahedral geometry in 4 are rather large, with angles as large as 148\u00b0 and as small as 70\u00b0. Another possible explanation of the observed differences stems from the possibility of metallophilic interactions between the Cu and Pt in 4, and a lack of these interactions in 7. Closed shell, d10\u2013d10 interactions involving these two nuclei are rare in comparison to examples involving gold;i) interaction has been suggested as possible by a combined HF-DFT-MP2 study of simple model compounds.4 (2.668(3) \u00c5) is slightly less than the sum of covalent radii of the two metals (2.68 \u00c5),7, featuring identical metals, seemingly contradicts this argument. Optimization of 4 using the OLYP functional failed to accurately reproduce the experimental Pt\u2013Cu bond length, instead giving a much longer distance (2.83 \u00c5). As it is well known that standard DFT methods do not adequately treat dispersion interactions,3)+ fragment in 4 was replaced by a Cu(IMe)+ fragment (IMe4)4 than a compound with an NHC-stabilized Cu atom.The differences between 2 dimers as compared to a range of other ligands, including phosphines.2 dimers, these Au\u00b7\u00b7\u00b7L interactions were found to be the strongest when L = NHC, but only in conformations where the planes of the NHCs were parallel to one another. In other conformations, the stabilizing interaction is far smaller, falling below the computed strength of the Au\u00b7\u00b7\u00b7PH3 interaction in the [PH3\u2013AuCl]2 dimer. Calculations at the MP2 level have indicated that in the case of a [PH3\u2013CuCl]2 dimer the Cu\u00b7\u00b7\u00b7PH3 contribution to dispersion is the dominant term.IMe4, which perhaps limits the strength of the dispersion forces. Both the [Cu(PCy3)]+ and [Cu(ITol)]+ fragments are bulky, and from a strictly steric standpoint would favor inhabiting opposite sides of the molecule from the likewise bulky [Pt(PCy3)] fragment (the distorted square planar arrangement); however, the significant dispersion forces calculated for 4 may play the deciding role in the compound's observed geometry.The influence of stabilizing ligands on the dispersion forces between closed-shell metal ions is a matter of open debate. In comparing model L\u2013AuCl systems, Pyykk and coworkers found NHCs to promote the strongest dispersion forces in [L\u2013AuCl]4 is the seeming lack of them in 2 and 3, especially when considering the rather short Cu\u00b7\u00b7\u00b7Cu and Au\u00b7\u00b7\u00b7Au distances. The optimized geometries for both of these compounds give M\u00b7\u00b7\u00b7M lengths of 2.48 and 2.82 \u00c5 for 2 and 3, respectively, which are slightly greater than, but still in the range of, their experimental values (2.4730(5) \u00c5, 2; 2.803(1) \u00c5, 3). The application of Grimme's dispersion correction changed the optimized bond distances only slightly . Though confirmation of this through ab initio methods is still needed, these findings suggest that the geometries of 2 and 3 are dictated by covalent bonding in the Mn4M2B2 core rather than by closed-shell dispersion interactions.Perhaps even more interesting than the presence of strong dispersion forces in 3)2, giving structures that seem to rely on dispersion-type d10\u2013d10 interactions for their shape.The use of coinage metal ions with easily-displaced ligands provided a route to expanded metallaboride compounds containing six metal atoms. Systems such as these may find use in the future as mimics for the surfaces of boron-containing bulk materials. In these compounds the metalloid nature of boron is on display. These hexametalladiborides were split into tetrametallaborides through treatment with Pt(PCyElucidation of the transition from boron-rich metallaboranes to metal-heavy transition metal borides may well lead to the discovery of bulk materials with many possible applications. Knowledge regarding the systematic syntheses of compounds within this continuum, such as the findings described here, are important tools in these efforts.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Utilization of tellurite anion as template, led to the formation of unprecedented oxothiometalate based building blocks and the spontaneous manifestation of chirality. 2S2O2(H2O)6]2+ and a tellurite anion led to the formation of three new clusters, 1\u20133, with unique structural features. The tellurite anion not only templated the formation of [(Mo2O2S2)4(TeO3)(OH)9]3\u20131 and [(Mo2O2S2)12(TeO3)4(TeO4)2 (OH)18]10\u20133, but also the in situ generation of two different types of dimeric {Te2O6} based moieties induced the spontaneous assembly of the chiral [(Mo2O2S2)10(TeO3)(Te2O6)2(OH)18]8\u2013 anionic cluster, 2.Utilization of [Mo Polyoxometalates (POMs) are metal oxide-based molecular clusters that have attracted a lot of attention in the last three decades due to their structural versatility42\u2013 or WO42\u2013),2O2S2]2+ which forms the basis of the work reported herein.The principal factor that distinguishes POTMs from conventional POMs is the unique set of building blocks from which these compounds are derived. Whereas conventional POMs are synthesised in most cases directly from mononuclear metal oxide anions 32\u2013) or tellurite (TeO32\u2013) anions30In the absence of any other structure directing agents, the structures formed by the condensation of the [Mo2O2S2]2+ cationic dimers and form intricate architectures, it has been the only inorganic species observed to template the formation of building blocks on their own. In an effort to expand and diversify the existing building block library, it was hypothesised that the larger atomic radius of the tellurite anion, TeO32\u2013, its tendency for aggregation and difference in redox properties32\u2013 anions could influence the assembly process and potentially trigger redox processes which could lead to the generation of new building block libraries and facilitate the formation of new species.While it has been demonstrated that the selenite anion can template constructively [Mo3[(Mo2O2S2)4(TeO3)(OH)9]\u00b720H2O (1), K8[(Mo2O2S2)10(TeO3) (Te2O6)2(OH)18]\u00b745H2O (2) and (C4H12N)K9[(Mo2O2S2)12(TeO3)4 (TeO4)2(OH)18]\u00b748H2O (3) . Interes2O2S2]2+ solution gave rise to a series of new building blocks \u20131.921(9) and 1.831(8)\u20131.865(7) \u00c5; Mo\u2013Mo bond lengths within the [Mo2O2S2]2+ unit are found to be 2.831(1)\u20132.866(1) and 2.807(1)\u20132.848(1) \u00c5; Mo\u2013S bond lengths vary from 2.231(3)\u20132.360(3) and 2.306(3)\u20132.344(3) \u00c5; and Mo PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond lengths vary from 1.664(8)\u20131.695(7) and 1.666(9)\u20131.693(8) \u00c5, respectively. Finally, the Mo\u2013O(Te) distances are found to be 2.142(7)\u20132.499(8) and 2.198(7)\u20132.373(7) \u00c5 while the distance between the Mo centres and the hydroxo bridges Mo\u2013O(H) spans the ranges 2.056(7)\u20132.171(7) and 2.100(8)\u20132.149(8) \u00c5.The presence of the tellurite anion in the [Mog blocks . The bui2O2S2]2+ dimer units gave rise to the formation of two fundamentally new building blocks, [(Mo2O2S2)3(Te2O6)(OH)8]4\u2013C and D. The discovery of these two new building blocks was possible due to the ability of the tellurite anion to aggregate into small clusters which can then template further the formation of [Mo2O2S2]2+ building blocks. This chemical behaviour has been observed before where small multi-nuclear tellurite fragments were trapped by vanadium-based polyoxometalate fragments as reported by Norquist et al., although organic species have been known to trap these types of moieties as well.C and D building blocks might look similar, there is a crucial difference of the connectivity between the tellurium atoms. In C, the tellurium atoms are linked through two bridging oxygen atoms with varying Te\u2013O bond lengths, 1.924(6)\u20132.270(7) \u00c5 while building block D exhibits only a single bridging oxygen atom between the two tellurium atoms with the relevant Te\u2013O bond lengths falling within the range of 1.872(6) and 2.220(6) \u00c5. The difference in connectivity which is reflected in the bond distances, and causes significant distortion in the \u201copen-ring\u201d structure and asymmetry in the available coordination sites is proven to be crucial during the assembly process, which will be discussed below.Interestingly, the interaction of tellurite anions with the 4\u2013 anion. It is important to note here that the observed change in coordination mode is not associated with a change in its oxidation state as shown by bond valence sum (BVS) calculations. The [TeIVO4]4\u2013 template adopts a \u201csee-saw\u201d configuration; the two \u201carm\u201d oxygen atoms display an angle of 163.2(3)\u00b0 while the \u201cpivot\u201d oxygen atoms display an angle of 98.6(4)\u00b0. The \u201carm\u201d oxygen atoms are coordinated to one Mo-centre each, where one of the \u201cpivot\u201d oxygen atoms is coordinated to two and the other one is free. In this case, the Te\u2013O bonds appeared to be elongated as expected; the Te\u2013O(arm) bond lengths fall in the range 2.034(9)\u20132.042(9) \u00c5, while the Te\u2013O(pivot) (coordinated) and Te\u2013O(pivot) (uncoordinated) bonds were found to be 1.864(9) and 1.940(10) \u00c5, respectively. Finally, the rest of the bond distances appeared to be in agreement with the previously discussed A\u2013D building blocks; the Mo\u2013Mo, Mo\u2013S and Mo PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO distances were found to be 2.819(1)\u20132.826(1), 2.315(3)\u20132.334(3) and 1.683(9)\u20131.701(9) \u00c5, respectively. Finally, the bonding distances between the oxygen of the template and the Mo centres range from 2.142(8)\u20132.155(9) \u00c5 [Te\u2013O(arm)] and 2.290(9)\u20132.297(9) \u00c5 [Te\u2013O(pivot)].Finally, building block A\u2013E building blocks in the reaction mixtures became evident also during the course of the electrospray ionization mass spectrometry (ESI-MS) studies in solution. It was possible to identify not only the intact 1\u20133 species but also their building blocks generated by partial fragmentation of the clusters into their most stable components and 60.45\u00b0 to the B 12(TeO3)4(TeO4)2(OH)18]10\u2013, is the largest member of this family of clusters and is constructed from four type A and two type C building blocks. These building blocks form a large ring and are arranged in an alternating fashion, with each one rotated 180\u00b0 relative to the two on either side of it. This gives rise to a structure reminiscent of the chair-conformer of cyclohexane. The central cavity of the molecule is 8.97 \u00c5 in diameter, with all lone pairs on the Te atoms pointing towards the centre of the cavity. Crystallographic studies revealed the presence of disordered electron density within the cavity attributable to the presence of potassium cations. The ring shaped topology in combination with the directionality of the tellurium based lone pair electrons makes a cluster framework that resembles an inorganic \u201ccrown ether\u201d topology with the ability to bind different cations in its central cavity.Compound 3 are considered relatively symmetric, the overall structure exhibits less symmetry elements than excepted due to the relevant orientation between the two C-type and four A-type building blocks. Thus, the point group of cluster 3 is lowered to CS, which exhibits only a reflection plane and involves the Te-atoms of the two C-type building blocks. Very subtle and localised changes in coordination geometry and orientation of the building blocks drastically reduced the symmetry of the entire molecule. It is worth noting at this point a few synthesis considerations which influence the formation of 1\u20133. In each case, the reaction takes place under the same conditions. However, there is a narrow range of pH values (6.8\u20137.8) which distinguishes the different assembly processes 3(Te2O6)(OH)8} C and {(Mo2O2S2)3(Te2O6)(OH)8} D. Interestingly, the ability of the tellurite anion to aggregate into small clusters, {Te2O6}, not only templated the formation but also induced asymmetry to the discovered building blocks and influenced further their connectivity and assembly. This resulted finally in the spontaneous assembly of the second example2, and dramatically lowered the overall symmetry to CS for 1 and 3. In future work, we will attempt to generate new templates which will give rise to new building blocks and will also extend our symmetry breaking approach to gain access to new POTM structural features, nuclearities and symmetries.In conclusion, we have discovered and characterised the first members of a new family of POTM clusters which are constructed using [MoThe authors declare no conflicts of interest.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The Cr-catalyzed [aziridine + CO2] coupling to form oxazolidinone was found to exhibit excellent selectivity for the 5-substituted oxazolidinone product in the absence of any cocatalyst. 2] coupling to form oxazolidinone was found to exhibit excellent selectivity for the 5-substituted oxazolidinone product in the absence of any cocatalyst. Quantum mechanical calculations suggest that the preferential opening of the substituted C\u2013N bond of the aziridine over the unsubstituted C\u2013N bond is a key factor for this selectivity, a result that is supported by experiment with several phenyl-substituted aziridines. In the presence of external nucleophile such as dimethyl aminopyridine (DMAP), the reaction changes pathway and the ring-opening process is regulated by the steric demand of the nucleophile.The Cr-catalyzed [aziridine + CO Traditional oxazolidinone syntheses often rely on the use of phosgene and reactive derivatives of carbonic acid, which is not atom-economical and can limit the scope of their utility.2 is an attractive alternative that can exploit the easy accessibility of a broad range of substituted aziridines and CO2.2.Oxazolidinones constitute an important class of organic molecules with significant biological relevance,2 into 4-substituted oxazolidinone or an unselective mixture of 5- and 4-substituted oxazolidinones. We also reported the use of [CrIIICl + DMAP] catalyst in the facile conversion of a range of aziridines into 5-substituted and 4-substituted oxazolidinones with selectivity up to 20\u2009:\u20091 favoring the 5-substituted isomer (eqn (1)).2, the observed selectivity was only moderately in favor of 4-substituted oxazolidinone, consistent with the opening of the aziridine ring at the less substituted position.IIICl + DMAP] catalyst system is quite unique and we proposed that this is a consequence of a Lewis-acid activation that favored ring-opening at the carbon stabilized by the aryl substituent.30During the past decade, a handful of catalysts\u2014including DMAP,IIICl was even more selective for reaction 1 in the absence of DMAP cocatalyst: the conversion of N-propyl-2-phenylaziridine to the corresponding 5-substituted oxazolidinone proceeds with a selectivity of 40\u2009:\u20091, albeit with a slightly slower rate than that for the DMAP-cocatalyzed reaction.N-propyl-2-(p-methoxyphenyl)aziridine (see below). These data are in stark contrast to the analogous [epoxide + CO2] coupling2 to the CrIII center CrIII(aziridiniumcarbamate) intermediate (3). The CO2-derived oxygen nucleophile of the carbamate moiety can then intramolecularly ring-open the tethered aziridine substrate. The uniqueness of this mechanism lies in the key presence of the CO2-coordinated intermediate 2 and the ability of the carbamate oxygen nucleophile to regulate the oxazolidinone selectivity by preferentially opening one of the two available C\u2013N bonds in an intramolecular fashion, depending on the ability of the substituents at the aziridine C2 to stabilize the developing cationic charges.Interestingly, CrI center . This ac2 can weakly bind to the highly Lewis-acidic CrIIICl center and cause a slight polarization of the electron density in the coordinated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond. This results in an increase in the electrophilicity of the CO2 carbon and renders it susceptible to a nucleophilic attack by the phenyl aziridine substrate to form intermediate 3 CrIIICl center results in a polarization of the coordinated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond, which slightly elongates (1.17 \u00c5) over the other C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond (1.16 \u00c5).2 carbon -fitted charge increases to 0.73 from 0.69), rendering it easier to undergo attack by the phenyl aziridine substrate. Our quantum mechanical calculations suggest that this event is favored enthalpically by 7.5 kcal mol\u20131, but is canceled out by the translational entropic penalty to afford a solvation-corrected Gibbs free energy of \u20130.1 kcal mol\u20131, measured from the initial lowest-energy reference state of the system .As mentioned above, the binding of CO2 by CrIIICl, as shown in 2 employed in our experiments, it can be inhibited by the direct binding of the Lewis-basic aziridine substrate to the Cr center. Such coordination can competitively retard the rate of the catalytic cycle, especially in the absence of a cocatalyst that can ring-open the coordinated substrate. Indeed, our calculations reveal that while the Lewis acid\u2013Lewis base interaction between CrIIICl and the aziridine substrate does significantly activate the aziridine ring CrIIICl-coordinated alkoxide intermediate 3 for this process can be located at an energy of 14.6 kcal mol\u20131. Consistent with such a nucleophilic attack, the linear CO2 becomes significantly bent to 157.8\u00b0, with noticeable elongations of both \u201cC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u201d bonds (\u223c0.03 \u00c5). The formation of intermediate 3 is energetically uphill by 8.7 kcal mol\u20131 from the initial lowest-energy state. At this intermediate stage, the coordinated aziridine retains its three-membered ring structure despite significant elongations of both substituted and unsubstituted C\u2013N bonds compared to the unsubstituted N\u2013C3 bond (to 1.48 \u00c5 from 1.45 \u00c5). This differential elongation is larger than the bond lengths change when aziridine binds directly to the CrIII center CrIIICl center and the aziridine substrate, does not require the opening of a new coordination site from distorting the salen ligand, as proposed by Luinstra and coworkers for the coupling of CO2 and epoxide.The nucleophilic attack of the aziridine substrate on the activated COediate 3 , where C\u2013N bonds . Notably2 bond in the aziridine-attacked intermediate 3 should logically lead to a selective formation of the 5-oxazolidinone product. To verify whether the observed selectivity of reaction 1 has a thermodynamic component, we evaluated the difference in ground-state energies of nine pairs of 5- and 4-aryl-N-propyl oxazolidinones comprising a broad range of para (p)-substituted phenyl groups. The apparent insensitivity of this difference to electronic changes in the aryl substituent . Since this process is completely intramolecular, the carbon with higher partial positive character is more likely to undergo nucleophilic attack. Thus, the presence of electron-donating (or -withdrawing) p-substituents on the aziridine phenyl rings can be expected to greatly influence this process via stabilization (or destabilization) of the developing carbocationic charge at the C2 center. To verify this, we evaluated the differences in charges between C2 and C3 centers for five different analogs of 3 where the phenyl groups of the coordinated aziridine rings possess p-substituents ranging from electron-donating to -withdrawing , effectively stabilizing the developing positive charge of the \u201cincipient carbocation\u201d. Indeed, the corresponding molecular orbital picture of major3-TS for the C2\u2013phenyl bond, to 1.29 from 1.02, that is considerably higher than that of a single bond (\u223c1.00). Upon free-geometry optimization, the located major3-TS easily leads to intermediate 4, indicating a direct connection between it and the 5-substituted oxazolidinone product.Having verified that ring-opening is favored at the Cediate 3 , we locaaction 1 , the rin3 are equally efficient for the subsequent nucleophilic aziridine ring-opening. The alternative ring-opening transition state major3-TS\u2032, where O4 is the nucleophile, is electronically only 1.45 kcal mol\u20131 higher in energy than major3-TS and has essentially the same solvation-corrected free energy for this reaction, the amount of free chloride ion CrIIICl catalyst) that can promote the ring-opening of any activated aziridine through a \u201cbimolecular\u201d mechanism would be negligible. The low level of chloride can be attributed to a combination of low catalyst loading (\u22641 mol%) and the strong bond between the anionic chloride ligand and the cationic Cr(III) center: our calculations suggest that the dissociation of chloride ion from CrIIICl would cost a sizable energy penalty of 26.5 kcal mol\u20131. The catalyst, CrIIICl itself, being a very poor nucleophile, also cannot open the activated aziridine ring in a bimetallic reaction mode in this asynchronous TS are quite similar. In the gas phase, the electronic energy of minor3-TS was \u223c7.3 kcal mol\u20131 higher than that of major3-TS, consistent with the disfavored formation for the 4-substituted oxazolidinone that was experimentally observed.\u20131) is higher than our expectation, it reproduces well the trend in favor of the major product.Interestingly, transition-state searches for the path that leads to the 4-substituted oxazolidinone minor product revealed an minor3-TS starts with rot3, a rotamer of intermediate 3 where proper alignment of the respective interacting groups have been attained scale\" fill=\"currentColor\" stroke=\"none\">O bond is elongated considerably (from 1.21 to 1.24 \u00c5), a direct consequence of its rehybridization into a nucleophilic C\u2013O moiety. This change can be quantified by the change in the Mayer\u2013Mulliken BO for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group, which is reduced to 1.56 in minor3-TS from an initial value of 1.81 in rot3. Upon closer inspection, it becomes evident that the unstabilized incipient carbocation at C3 is so electron-deficient that the phenyl group on the adjacent C2 carbon is taking part in anchimeric assistance. As in the case of major3-TS, minor3-TS also adopts an envelope structure that is characteristic of five membered rings. Given the high energy of minor3-TS, we surmise that the small amount of 4-substituted oxazolidinone minor product observed under our experimental condition does not arise from the intramolecular opening of the aziridine ring by the carbonyl functionality of 3. Instead, an alternative pathway may be operative where a CrIII-bound aziridine is opened by another aziridine molecule, in a manner similar to DMAP in the mechanism shown in 2 and the minor product forms via ring-closing (see discussion below).It is noteworthy that the pathway leading to attained . The req3 that eventually leads to the enhanced formation of 5. Such differences in charge development should be apparent through product selectivity in a Hammett-type investigation. To this end, we examined the CrIIICl-catalyzed coupling of CO2 with several p-substituted N-propyl-2-arylaziridines in the competitive presence of the parent N-propyl-2-phenylaziridine and in the absence of DMAP (eqn (2)). Notably, the experimental selectivity for the 5-substituted isomer was found to vary over almost an order of magnitude, with as high as 80\u2009:\u20091 for N-propyl-2-(p-methoxyphenyl)aziridine and as low as 12\u2009:\u20091 for N-propyl-2-(p-bromophenyl)aziridine.Thus far, our theoretical analyses predict a differential activation of the two carbons on the activated aziridine ring in intermediate \u03c3p+ values, the ratio of oxazolidinone products (5-substituted/4-substituted) obtained from the corresponding aziridines in reaction 2 afford an excellent linear correlation (R2 = 0.98), signifying a clear influence of substrate electronic effects on product selectivity. In addition, the moderate magnitude of this negative \u03c1 (\u20131.28) is consistent with the presence of an incipient cationic character2 in the aziridine ring-opening step. This fits well with our computational results that the aziridine N\u2013C2 bond becomes polarized upon attacking the coordinated CO2 moiety on the coupling.Because reaction 1 passes through a concerted, synchronous transition state CrIII(aziridiumcarbamate) intermediate. Theoretical modeling and transition state search reveal that such a process is only possible through an initial key coordination of the CO2 molecules to the CrIII center, which activates the CO2 carbon for nucleophilic attack by the aziridine substrate. In the resulting CrIII(aziridiumcarbamate) intermediate, either of the two carbamate oxygen atoms can act as an intramolecular nucleophile to ring-open the aziridine moiety, allowing for an exquisite control of the regioselectivity. Together, these results also shed light on the erosion of selectivity for the 5-substituted isomer when the CrIIICl-catalyzed [aziridine + CO2] coupling is carried out in the presence of the DMAP cocatalyst.In summary, we presented the complete mechanism of the Cr2 allows for the substituents of the aziridine substrates to have a substantial influence on both their reactivities with CO2 and the selectivities for the final product. Indeed, the broad range of selectivity for 5- vs. 4-substituted oxazolidinone varies almost over an order of magnitude for different aziridines (80\u2009:\u20091 for N-propyl-2-(p-methoxyphenyl)aziridine to 12\u2009:\u20091 for N-propyl-2-(p-bromophenyl)aziridine).Notably, we showed through a detailed Hammett study that while there is not a significant formal charge development in the aforementioned ring-opening process, its intramolecular nature and the incipient cationic nature of the aziridine CSupplementary informationClick here for additional data file."}
+{"text": "The trifunctional P/B/B frustrated Lewis pairs 11a\u2013c featuring bulky aryl groups at phosphorus were synthesized. Compounds 11a,b react with carbon monoxide and form the macrocyclic dimers 17a,b, while the carbonylation reaction of the Mes*P/B/B FLP 11c gives the macrocyclic trimer 18c. 11a\u2013c featuring bulky aryl groups at phosphorus react with H2 by heterolytic hydrogen splitting followed by cleavage of HB(C6F5)2 to give the zwitterionic six-membered heterocyclic PH phosphonium/borate products 14a\u2013c. Compounds 11a,b react with carbon monoxide by means of a Lewis acid induced CO insertion/rearrangement sequence that eventually results in the formation of the macrocyclic dimers 17a,b. The respective carbonylation reaction of the Mes*P/B/B FLP gives the macrocyclic trimer 18c. The new products were characterized spectroscopically and by X-ray diffraction and the reaction mechanism was analyzed by DFT calculations.The trifunctional P/B/B frustrated Lewis pairs Macrocyclic compounds have very interesting structural features.We have now found that Lewis pair formation might favor intermolecular cyclooligomerization in cases where the direct internal interaction of the Lewis acid and base functionalities is effectively precluded by specific geometric restrictions. We have found that this may selectively lead to cyclodimeric and even cyclotrimeric ring systems in a rather simple experimental procedure. First examples will be presented and discussed in this account.6F5)2] (2) occurs readily.1) hydroboration compound PhCH2CH2B(C6F5)2 (3), however, do not readily insert CO at ambient conditions 3. The difference is even more pronounced with vicinal P/B frustrated Lewis pairs (FLPs), such as compound 6, which readily reacts with CO, but does not form the CO insertion product into the [B]\u2013CH2\u2013 linkage but rather undergoes cooperative 1,1-P/B addition to the carbon atom of carbon monoxide to yield the CO-bridged product 7. A number of related P/B FLPs show a similar behavior.Alkyl boranes are important building blocks in organic synthesis. Many such systems are readily available by convenient hydroboration routes.6F5)2 Lewis acid unit making the alkyl migration step to carbon monoxide unfavorable. Introduction of a second B(C6F5)2 group into the system might potentially provide a way out of this behavior: specifically located it could function as an activator for the P/B bonded carbonyl unit and thus initiate the otherwise unfavorable CO insertion reaction in such systems. This turned out to be a successful concept and, in addition, it opened an easy pathway to several rather unusually structured macrocyclic ring systems. Three such examples with some of their remarkable characteristic features will be reported in this account.We reasoned that this behavior might originate from the very special properties of the strong B(C8a\u2013c by treatment of the respective ArPCl2 precursors8c with one molar equiv. of HB(C6F5)2 which had given the unique zwitterionic methylene phosphonium product 10cvia internal B(C6F5)2 addition to the adjacent vinyl phosphane and 2,4,6-triisopropylphenyl (Tipp) aryl groups at phosphorus, respectively. Compound 11a also features an equilibrating dynamic structure in solution analogous to the previously described behavior of 11c. We had shown that the P/B/B system 11c splits dihydrogen in the presence of the external base tBu3P to give 12c.49We have prepared the aryldivinylphosphanes hane see .48 Additcopy see .49f We h11a\u2013c to dihydrogen in the absence of the external base and found a markedly different behavior which indicated a surprising mode of participation of the extra \u2013B(C6F5)2 Lewis acid. Typically, the in situ generated system 11a was exposed to a H2 atmosphere (1.5 bar) in dichloromethane solution for 30 min at r.t. to give a mixture of the zwitterionic heterocyclic phosphonium/borate product 14a (Ar: Dmesp) and HB(C6F5)2. The latter was removed from the mixture by the hydroboration reaction with 1-pentene converting it to pentane soluble pentyl-B(C6F5)2. It was isolated and identified as its pyridine adduct 15py . The 13C NMR spectrum shows signals of the six-membered core unit at \u03b4 19.0 and \u03b4 20.8 , respectively 2 Lewis acid becomes actively involved and forms the six-membered P/B heterocycles 14 by a \u03c3-bond metathesis type reaction6F5)2. The formation of the products 14 and HB(C6F5)2 (2) gave us a strong indication of the active role of the additional-B(C6F5)2 Lewis acid in the compounds 11. This we used advantageously in the reaction of the P/B/B FLPs 11a\u2013c with carbon monoxide.The P/B/B compounds 11b (Ar: Tipp) in situ 2 functionalityvia16A might initiate the kinetically facile and thermodynamically feasible formation of the CO insertion product3216B. Isomerization forms the P/B Lewis pair. In 16C the direct internal interaction of the carbonyl oxygen with the pendent borane Lewis acid is geometrically precluded; the system may serve as an active C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO/B frustrated Lewis pair. This leads to dimerization giving the observed macrocyclic reaction product 17b.We assume a reaction pathway as it is depicted in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7borane interactions. The remaining boron atoms form Lewis pair interactions with their adjacent phosphane Lewis bases. In this situation two diastereoisomers are possible due to the phosphorus chirality;C2-symmetric rac-structure in the crystal = 1588 cm\u20131 [\u03bd\u0302(13CO) = 1547 cm\u20131] carbonyl stretching band.In solution, compound 11a reacts analogously with CO. We isolated the C2-symmetrical dimer 17a in 61% yield and characterized it by C,H-elemental analysis, by NMR and IR spectroscopy (\u03bd\u0302(CO) = 1579 cm\u20131) and by X-ray diffraction (for details see the ESI17b. Compound 17a lost CO upon heating to 50 \u00b0C (12 h) in dichloromethane solution to give the starting material 11a.The Dmesp substituted P/B/B system 11c took a slightly different course. Exposure of the in situ generated Mes*P/B/B system 11c to CO gave compound 18c (81% isolated) (see 11c in solution (CD2Cl2). Therefore, the solution NMR data were monitored using in situ generated samples at low temperature and a cis-, trans-, trans-isomer. The latter structural situation is found in the crystal of compound 18c. Each of the three symmetry inequivalent but chemically closely related subunits features a five-membered P/B containing heterocyclic carbonyl moiety. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group is used for bridging to the pendent \u2013B(C6F5)2 Lewis acid of the next monomeric subunit (see The carbonylation reaction of the Mes*P/B/B system ted) see . The comunit see .18c). We note an almost co-linear arrangement for the pair of Tipp-P units in the dimer 17b. The respective P1\u2013C11\u2013C14 angles for the pair of crystallographically independent Tipp-P subunits were found at 174.4\u00b0 and 173.1\u00b0. We find a slightly bent structure for the more bulky Dmesp-P groups in compound 17a with P1\u2013C11\u2013C14 angles of 171.0\u00b0 and 166.2\u00b0, respectively, but we note a rather extreme bending of the Mes*-P moiety. In the Mes*-PCl2 reagent the P1\u2013C11\u2013C14 type angle amounts to 156\u00b0.18c we find this distortion of the (aryl)C\u2013P moieties being increased further by ca. 10\u00b0 to P1\u2013C11\u2013C14 values of 144.1\u00b0, 147.9\u00b0, and 146.1\u00b0, respectively. 18c, which visualizes this strong distortional effect. This might actually have created an overall conformational situation that may have contributed to determining the observed chemistry of this system to a considerable extent, especially the specific association behaviour of the monomeric subunits forming the observed cyclotrimer 18c.Arylphosphanes usually have the C(aryl)-P vector oriented in line with the aryl plane. Very bulky arylphosphanes may deviate from this behavior structure of the cyclotrimer 18c containing three different phosphorus atoms. Consequently, three 31P NMR signals at 12, 13 and 15 ppm were observed which are broadened and additionally split by the indirect 31P\u201311B spin\u2013spin coupling (1J(31P\u201311B) \u223c 80 Hz). As illustrated in 11B and 1H decoupling enhances the resolution of the 12 pairs of diastereotopic CH2 hydrogen atoms as well as 12 methylene 13C NMR signals of the core ring carbons. There are nine separate 1H NMR t-Bu singlets and the 19F NMR signals of 12 C6F5 groups at the boron atoms of compound 18c. The 13CO derived isotopologue showed three 13C NMR carbonyl signals 2 Lewis acid function influences the reaction of the internal ethylene-bridged P/B FLP functionality of the compounds 11 in two decisive ways: activation of the carbonyl group at the stage of the conventional cooperative P/B CO addition intermediate 16A2\u2013B(C6F5)2 group feasible. Our DFT analysis of the CO insertion step of the Mes*P/B/B system revealed an exergonic formation of the intermediate 16Bc = 0]. Once the carbonyl compound is formed by C\u2013C bond formation it is prone to rearrangement generating a monomeric intermediate 16C featuring both an organic carbonyl function and a remote free \u2013B(C6F5)2 Lewis acid, a combination which paves the way to formation of the unique macrocyclic oligomers 17 and 18 by Lewis adduct formation between these pairs of functional groups.It seems that the presence of the additional B in the Tipp substituted system vs. the cyclotrimer (18c) in the case of the Mes* containing system: in the Tipp containing system we find an energetic preference of the formation of the cyclodimer of ca. 5 kcal mol\u20131 over the trimer, whereas in the case of the more bulky Mes* system this becomes reversed and the cyclotrimer is favored by ca. 10 kcal mol\u20131 over the dimer (see the ESI18c might indeed point to a marked influence of specific conformational features introduced by the very bulky aryl Mes* substituent into this chemistry.Why are the macrocyclic dimers and even a cyclotrimer formed in our examples instead of the alternative linear oligomers? Actually, we do not know for sure, but we may speculate that this has to do with the special properties encountered in phosphane/borane frustrated Lewis pair chemistry. This chemistry is governed by van der Waals interactions between the bulky protagonists and it becomes increasingly apparent that conformational features strongly determine frustrated Lewis pair behavior.11 emphasizes the potential that frustrated Lewis pair chemistry has for discovering surprisingly facile pathways to unusual products formed under mild reaction conditions.The formation of the macrocyclic dimers and trimers from our carbonylated P/B/B FLP systems may place some frustrated Lewis pair reactions into the group of macrocyclic ring closure procedures that show a \u201cnatural\u201d tendency of favoring the internal bond formation in cases of a suitable general design.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We report a monometallic dysprosium(iii) single molecule magnet with record energy barriers and unusual spin relaxation behaviour. iii) bis(methanediide) single molecule magnet (SMM) where stabilisation of the highly magnetic states and suppression of mixing of opposite magnetic projections is imposed by a linear arrangement of negatively-charged donor atoms supported by weak neutral donors. Treatment of [Ln(BIPMTMS)(BIPMTMSH)] with benzyl potassium/18-crown-6 ether (18C6) in THF afforded [Ln(BIPMTMS)2][K(18C6)(THF)2] . AC magnetic measurements of 2Dy in zero DC field show temperature- and frequency-dependent SMM behaviour. Orbach relaxation dominates at high temperature, but at lower temperatures a second-order Raman process dominates. Complex 2Dy exhibits two thermally activated energy barriers (Ueff) of 721 and 813 K, the largest Ueff values for any monometallic dysprosium(iii) complex. Dilution experiments confirm the molecular origin of this phenomenon. Complex 2Dy has rich magnetic dynamics; field-cooled (FC)/zero-field cooled (ZFC) susceptibility measurements show a clear divergence at 16 K, meaning the magnetic observables are out-of-equilibrium below this temperature, however the maximum in ZFC, which conventionally defines the blocking temperature, TB, is found at 10 K. Magnetic hysteresis is also observed in 10% 2Dy@2Y at these temperatures. Ab initio calculations suggest the lowest three Kramers doublets of the ground 6H15/2 multiplet of 2Dy are essentially pure, well-isolated |\u00b115/2, |\u00b113/2 and |\u00b111/2 states quantised along the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axis. Thermal relaxation occurs via the 4th and 5th doublets, verified experimentally for the first time, and calculated Ueff values of 742 and 810 K compare very well to experimental magnetism and luminescence data. This work validates a design strategy towards realising high-temperature SMMs and produces unusual spin relaxation behaviour where the magnetic observables are out-of-equilibrium some 6 K above the formal blocking temperature.We report a dysprosium( Proposals have been made for devices employing the quantum effects of molecular magnets,iii).Ueff, for thermal relaxation processes. Furthermore, owing to the high symmetry of the LF potential there should be no mixing between components of opposite magnetic projection, therefore disallowing short-cuts through or under the barrier.iii), where equatorial LF potentials are required; this alternative approach has recently yielded an excellent result in the form of [Er(COT)2]\u2013.Ueff barriers.Many interesting SMMs have been reported based on a single lanthanide centre,Ueff.et al. reported the bis(methanediide) complex [Zr{C(PMe2NSiMe3)2}2], where the two ligands are orthogonal due to the \u2018locking\u2019 effect of the imino arms to avoid steric clashing.Simple electrostatic considerations imply that the strength of the axial LF depends on the charge on the donor atoms on the axis, and hence we proposed that the use of dianionic methanediides would optimise iii) which has a Ueff value of 813 K, the largest for any monometallic dysprosium(iii) complex. This complex also possess rich magnetisation dynamics where out-of-equilibrium magnetisation is observed below 16 K yet TB appears to be 10 K. Although the bis(methanediide) complex is not a two-coordinate linear system, it is clear that there is significant charge accumulation along the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axis which effectively mimics the linear arrangement we ultimately seek. Thus, this work experimentally validates our proposition that a linear arrangement of negative charges in a dysprosium(iii) complex should lead to very large energy barriers to magnetic relaxation, and provides a promising direction to making high-temperature SMMs a reality.Here we report the synthesis, structure, theoretical characterisation and magnetic studies of a bis(methanediide) complex of dysprosium(iii) complex is shown in 2Ph)3(THF)3]TMSH2 [BIPMTMSH2 = H2C(PPh2NSiMe3)2] in toluene produces an orange solution, which when briefly heated fades to yellow. Work-up and recrystallisation from toluene affords colourless crystals of the mixed methanediide\u2013methanide complex [Dy(BIPMTMS)(BIPMTMSH)] (1Dy) in 63% isolated yield. Alternatively, treatment of [Dy(BIPMTMS)(CH2Ph)(THF)] with one equivalent of BIPMTMSH2 also affords 1Dy in 63% yield. Complex [Dy(BIPMTMS)(CH2Ph)(THF)] was reported previously by us,TMS)(CH2Ph)(THF)] that effects metallation of free BIPMTMSH2 when heated. We previously showed that early, large lanthanides (La\u2013Gd) spontaneously form the mixed methanediide\u2013methanide combination irrespective of reactant ratios, presumably via highly reactive [Ln(BIPMTMS)(CH2Ph)(THF)] complexes due to the large metal size, whereas the later, smaller lanthanides like Dy and Er form isolable methanediide\u2013benzyl combinations. The formulation of 1Dy is supported by IR, CHN, and Evans method magnetic moment (\u03bceff = 11 \u03bcB), but the 1H NMR spectrum is broad and uninformative due to the paramagnetic DyIII ion.The route to a bis(methanediide) dysprosium derivative. Treatment of 1Dy with benzyl potassium in THF gave an orange suspension, which yielded a yellow solution after stirring. Following addition of 18-crown-6 ether (18C6) and concentration, yellow crystals of the bis(methanediide) complex [Dy(BIPMTMS)2][K(18C6)(THF)2]\u00b72THF (2Dy) were obtained in 43% isolated yield. The identity of 2Dy is supported by IR, CHN, and Evans method magnetic moment data (\u03bceff = 11 \u03bcB); however, as for 1Dy the 1H NMR spectrum of 2Dy is uninformative. For the purposes of doping 2Dy into a diamagnetic host we prepared the yttrium bis(methanediide) analogue [Y(BIPMTMS)2][K(18C6)(THF)2]\u00b72THF (2Y) in 60% yield from [Y(BIPMTMS)(BIPMTMSH)] (1Y). The interaction of the methanediide centres in 2Y with yttrium can be seen in the 13C NMR spectrum, which exhibits a single triplet of doublets at 53.70 ppm showing that the methanediides are magnetically equivalent on the NMR timescale; this can be compared to the 13C NMR spectrum of 1Y which exhibits a triplet at 19.87 ppm (JPC = 114.25 Hz) and a triplet of doublets at 66.50 ppm for the methanide and methanediide centres respectively. This suggests a significant interaction between the yttrium and methanediide centres in 2Y, and by inference a similar situation for the dysprosium and methanediide centres in 2Dy, which is important for generating a largely axial LF at dysprosium.With 1Dy and 2Dy were determined by X-ray crystallography and are illustrated in 1Dy crystallises as discrete monomers where the dysprosium centre is six-coordinate. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy\u2013C angle is 158.25(6)\u00b0, and the N\u2013Dy\u2013N angles are 129.51(5) and 110.51(5)\u00b0 for the methanediide and methanide ligands, respectively. The Dy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and Dy\u2013C bond lengths are 2.3640(17) and 2.9001(18) \u00c5, respectively, which reflects the formal double and single bond character of these linkages. The Dy\u2013N distances are longer in the methanediide [range: 2.4587(15)\u20132.4786(15) \u00c5] than the methanide [range: 2.3903(15)\u20132.4092(15) \u00c5]. The methanediide centre adopts an essentially T-shaped planar geometry [\u03a3\u2220 = 355.06(16)\u00b0] whereas the methanide is puckered to accommodate the hydrogen atom. Complex 1Dy does not approach the linear arrangement of highly charged donor atoms that we seek.The solid state structures of 2Dy crystallises as a solvent separated ion pair and there are no significant contacts between the [Dy(BIPMTMS)2]\u2013 anion and the [K(18C6)(THF)2]+ cation components. Complex 2Dy has the on-axis C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC arrangement of highly charged donor atoms required to test our proposal for high-temperature SMMs. The dysprosium ion is six-coordinate and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC angle is almost linear at 176.6(2)\u00b0. The methanediide centres adopt planar T-shaped geometries [av. \u03a3\u2220 = 357.1(6)\u00b0] and, importantly, the two C(PN)2Dy planes are disposed essentially orthogonal to each other [89.47(12)\u00b0]. The Dy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond distances of 2.434(6) and 2.433(6) \u00c5 are statistically identical, and longer than the Dy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC distance of 2.364(2) \u00c5 in four coordinate [Dy(BIPMTMS)(CH2Ph) (THF)] and in six-coordinate 1Dy, reflecting the trans-disposition of the two methanediide centres and the electron-rich, anionic formulation of the dysprosium fragment in 2Dy. The Dy\u2013N bond lengths in 2Dy average 2.461(9) \u00c5, which is consistent with the analogous methanediide-derived Dy\u2013N bond lengths in 1Dy. All other bond distances and angles in the (BIPMTMS)2\u2013 are unexceptional for this ligand in its dianionic state.Complex 1Dy and 2Dy were measured as neat polycrystalline powders dispersed in eicosane and flame sealed in a quartz NMR tube. The room temperature value of \u03c7mT of 2Dy is 13.5 cm3 mol\u20131 K, around 10% lower than expected for a free DyIII ion . Magnetisation (M) versus field (H) curves at 1.8 K saturate at a value of \u223c5.1 \u03bcB mol\u20131, confirming a well isolated |\u00b115/2 ground state.The magnetic properties of 2Dy in zero DC field show temperature and frequency dependent behaviour, characteristic of slow magnetic relaxation over two thermal barriers, \u03c4) at high temperatures is indicative of a dominant Orbach relaxation mechanism, whilst at lower temperatures its curvature suggests competing relaxation processes are active. As a temperature independent regime is not reached, this cannot be attributed to QTM and we therefore interpret this as a second order Raman process.iii) Kramers ion in the absence of a static magnetic field. A second-order Raman process is invoked because measurements were performed in zero DC field.\u00a7The first-order process should not be active for a Dy(AC magnetic measurements performed on Ueff(1) = 721(1) K (501 cm\u20131), \u03c40(1) = 1.11(3) \u00d7 10\u201312 s, C(1) = 3.01(7) \u00d7 10\u201311 s\u20131 K\u20138, n(1) = 8, \u03b1(1) = 0.01\u20130.03, Ueff(2) = 813(1) K (565 cm\u20131), \u03c40(2) = 5.65(20) \u00d7 10\u201313 s, C(2) = 3.55(10) \u00d7 10\u20139 s\u20131 K\u20136, n(2) = 6 and \u03b1(2) = 0.11\u20130.21. The values of \u03c40 are of the correct order of magnitude expected for an Orbach relaxation process over a large barrier (\u03c40 \u223c (10\u20135 to 10\u20133)/Ueff3)C and n are as expected for the second-order Raman process for Kramers ions.27iii) complex where the phonon spectrum is likely to be more complex. The fitted data were measured over a temperature range of 22\u201341 K where the approximations inherent to the phonon spectrum treatment mean that a simple T9 law cannot be expected to hold for the two-phonon process of a Kramers ion. For further details see pg 564\u2013565 of n are: non-Kramers doublet, n = 7; Kramers doublet, n = 9; multiplet with small splitting, n = 5. These exponents are based on a number of approximations that are parameterised overall by two numbers and thus represent a guide and not absolutes. For further details see pg 65\u201366 of \u00b6The Raman pre-factor ranges are wide but are close to predictions. The theoretical framework is based on simple crystal lattices with Debye-like phonon spectra; here we have an isolated 6-coordinate Dy, Fig. S3,Fitting the two data sets with eqn (1) yields TB) is conventionally defined as the maximum in the ZFC susceptibility;et al. have pointed out that for SMMs a second temperature, TIRREV, is also important which is the point where the FC and ZFC susceptibilities diverge, as this is the temperature below which the magnetic observables are out-of-equilibrium and show history dependent behaviour.TB and TIRREV are very similar, and observed differences have been assigned to a distribution of relaxation times.TB is the temperature where the relaxation time is 100 s.The blocking temperature (TB and TIRREV for 2Dy. Magnetic hysteresis is observed in M(H) loops for 10% 2Dy@2Y to at least 10 K for a sweep rate of 3.5 mT s\u20131 (2Dy gives a relaxation time of 100 s at 12 K. FC(c)/zero-FC (ZFC) measurements for 2Dy diverge at temperatures up to 16 K ; these data also diverge from FC(c) at temperatures up to 16 K depending on rates. Unusually, for any rate that we measured, the FC(w) data go above the FC(c) before reaching equilibrium. Such behaviour would normally be associated with a metastable state arising from the phenomenon of magnetostriction,We have used DC and AC magnetic measurements to establish both 5 mT s\u20131 and S4\u2020; to 16 K , with thTB and TIRREV, usually explained as owing to a range of relaxation times, is very large and does not appear to have precedent in SMMs. Accounting for these two observations, we can only suggest that multiple relaxation processes are competitive at low temperatures, including Raman and QTM mechanisms, which gives rise to this strange behaviour.Furthermore, the discrepancy of up to 6 K between M(H) even at the lowest temperature measured (1.8 K), Fig. S4 and S5.M = 0.15 \u03bcB after 10 hours. This is only 3% of the saturation magnetisation, but clearly some component of the system has a very long lifetime.There remains a significant, sweep-rate dependent, loss of magnetisation at zero-field in \u03c7mT of 1Dy is 13.7 cm3 mol\u20131 K at room temperature and is weakly temperature dependent until below 70 K where it starts to gradually fall, followed by a larger drop at very low temperatures at 1.8 K saturates at a value of \u223c5.2 \u03bcB mol\u20131 vs. 1/T curve at high temperatures, whilst at lower temperatures we observe a transition to a temperature independent regime vs. 1/T plot still curves at lower temperatures K (177 cm\u20131), \u03c40 = 3.55(9) \u00d7 10\u201312 s, C = 1.46(3) \u00d7 10\u20135 s\u20131 K\u20137, n = 7, \u03c4QTM = 9.26(10) \u00d7 10\u20133 s and \u03b1 = 0.06\u20130.22. The values of \u03c40 are of the correct order of magnitude expected for an Orbach relaxation process over a large barrier and the values of C and n are as expected for the second order Raman process for Kramers ions.27The best-fit parameters are 1Dy and 2Dy, we performed ab initio calculations of the CASSCF/RASSI/SINGLE_ANISO variety with MOLCAS 7.8.\u03c7mT vs. T plots for both compounds are almost identical to that obtained experimentally, save for the sub-16 K data for 2Dy scale\" fill=\"currentColor\" stroke=\"none\">Dy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axis. The result of this is that thermal relaxation via the second and third states is quenched. The fourth and fifth doublets are strongly mixed, and have main magnetic axes perpendicular to that of the ground state, allowing efficient relaxation (Ueff(1) = 721 K and Ueff(2) = 813 K.Based on the X-ray crystal structures of for 2Dy and S7\u2020,lets see and S1\u2020.\u2013\u2013P+(R)2\u2013C2\u2013\u2013P+(R)2\u2013N\u2013\u2013R resonance form of the (BIPMTMS)2\u2013 dianion is known to be the most appropriate way to formulate the formal charge distribution of this ligand,v) centres withdraw electron charge from the nitrogen centres rendering them relatively soft donors more in keeping with the imino character that is drawn in Lewis-style depictions. Although the phosphorus(v) centres do polarise some of the methanediide charge, it is evident from extensive studies of early metal BIPMTMS chemistry that the majority of the dianion charge remains at carbon available for donation to a coordinated metal.13C NMR chemical shift of the methanediide centres in 2Y is consistent with charge accumulation at these carbon centres and by inference this should be the case for 2Dy also. Thus, and in accord with experimental observations, the symmetrical disposition of the four nitrogen donors, which reside away from the formal equatorial plane due to the bite angle of the BIPMTMS ligand, imposes an axially symmetric equatorial potential (approximate S4 symmetry) which reduces the strength of, but does not destroy, the axial potential of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC motif in 2Dy. It is germane to note that although the dysprosium centre in 2Dy is of pseudo-octahedral geometry, an effectively linear charge build-up is obviously felt by the dysprosium centre, resulting in strong axial anisotropy, as evidenced by the magnetic behaviour of this system. If the pincer nitrogen donors could be replaced by more weakly coordinating groups, the Ueff value(s) would be even higher,Whilst the RN1Dy the ground doublet is largely |\u00b115/2 with a small admixture of |\u00b111/2, while the second doublet is more significantly mixed but still shows a dominant 81% |\u00b113/2 contribution scale\" fill=\"currentColor\" stroke=\"none\">Dy\u2013C(H) angle = 158.3\u00b0] and has a weaker axial potential due to the mono- and di-anionic ligands vs. the bis(di-anionic) set of 2Dy. The result is that the third doublet has a main magnetic axis perpendicular to the ground state and shows significant transverse g-factors, thus providing an efficient thermal relaxation pathway, Fig. S13 and Tables S5 and S6.Ueff value of 245 K agrees very well with the experimentally determined value of Ueff = 255 K.For 2Dy; we report results recorded at 13 K. After excitation with UV irradiation, sensitised complexes of DyIII are known to exhibit luminescence in the optical region owing to radiative decay from the 4F9/2 multiplet to the 6HJ multiplets, with photon energies (wavelengths) of approximately 21\u2009100 cm\u20131 (475 nm), 17\u2009500 cm\u20131 (570 nm) and 15\u2009200 cm\u20131 (660 nm), for the J = 15/2, 13/2 and 11/2 multiplets, respectively.2Dy exhibits strong emission at 20\u2009000\u201321\u2009000 cm\u20131 (J = 15/2) and 16\u2009700\u201317\u2009700 cm\u20131 (J = 13/2) but only weak signals are observed around 15\u2009000 cm\u20131 (J = 11/2), To further test and corroborate the validity of our model, variable temperature optical emission spectroscopy has been performed for 4F9/2 term, the only reliable transition is that of lowest energy into each multiplet, corresponding to a transition from the lowest lying 4F9/2 state into the highest energy states of the 6HJ multiplets. Therefore, using the low energy edge of the emission band to fix the location of the highest energy Kramers doublet in both the 6H15/2 and 6H13/2 multiplets, we compare the observed transitions to the calculated energy levels (6H15/2 multiplet (\u223c20\u2009490 cm\u20131) corresponds well to the calculated position of the third excited state, which suggests that the strong mixing of this state results in an enhanced transition probability. Conversely, transitions into the first excited and ground states of the 6H15/2 multiplet are expected to be much weaker as these are virtually pure |\u00b113/2 and |\u00b115/2 states. These conclusions are supported by the ab initio calculated transition probabilities between the lowest lying 4F9/2 state and the eight Kramers doublets of the 6H15/2 multiplet complex to date, where a Ueff of 481 K was previously the highest found in a Dy-salen-type Schiff base complex,4K2O(OtBu)12],2] derivative.3)2)3]Ueff = 122 K seems much more compatible with relaxation via the second state at a spectroscopically-determined 158 K.50The AC data are unequivocal that relaxation between 20 and 40 K occurs by Orbach and Raman mechanisms alone; the Orbach process going 2Dy. Firstly, there is a large step at zero-field in M(H) plots, which is conventionally explained as the hallmark of QTM. Our calculations predict a virtually pure |\u00b115/2 ground state and for such a state QTM should have a vanishingly small probability, therefore more work is required to investigate the relaxation mechanisms which cause this phenomenon. This step remains in the 3% diluted sample, and therefore it is possible that this is not dilute enough to completely remove transverse dipolar fields from nearby paramagnetic complexes. An alternative explanation is that nuclear hyperfine interactions may be responsible for this fast relaxation \u2013 a mechanism not accounted for in our purely electronic calculations. Such arguments have been made in Ho-SMMs,et al., who show that isotopic enrichment with nuclear-spin-free 164Dy provides a significant opening of the hysteresis loop compared to the I = 5/2 161Dy isotope.Below 16 K there are features we do not presently understand for 2Dy which contains two methanediide centres that are disposed trans to one another. Although the pincer arms coordinate in off-axial positions, and in principle may carry some charge, it is clear that overall the dysprosium(iii) bis(methanediide) complex 2Dy possess a strong axial LF due to significant negative charge accumulation along the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axis. We find that the weak equatorial donors do not destroy this strong axial LF; this is in contrast to the recent report of Zhang et al. who show that erbium(iii) complexes are strongly affected by weak axial donors, lowering the Ueff = 122 K of [Er{N(SiMe3)2}3] to Ueff = 34 K for [Er{N(H)Dipp}3(THF)2].48In the continued absence of true two-coordinate bis lanthanide complexes, we have prepared complex 2Dy in zero DC field show temperature- and frequency-dependent SMM behaviour. Orbach relaxation dominates at high temperature, but a second-order Raman process becomes important as the temperature is lowered. We find thermal energy barriers (Ueff) of 721 and 813 K for two distinct processes, the largest Ueff values reported for any monometallic dysprosium(iii) complex.45AC magnetic measurements of Ab initio calculations, which independently model the magnetic data remarkably well and are in good agreement with experimental optical spectra, suggest that the bottom three Kramers doublets of the ground 6H15/2 multiplet of 2Dy are essentially pure, well-isolated |\u00b115/2, |\u00b113/2 and |\u00b111/2 states quantised along the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC axis. Thermal relaxation via the second and third states is quenched, and relaxation occurs via the fourth and fifth states because they are strongly mixed, with calculated Ueff values of 742 and 810 K that compare very well to experimental values.2Dy suggest that TB = 10\u201312 K, yet the FC/ZFC data show a clear divergence at TIRREV = 16 K. Compound 2Dy is therefore a peculiar molecule where the magnetism is history dependent at a temperature significantly above the conventional \u201cblocking\u201d temperature. Previous in-depth studies to assess the competing relaxation mechanisms2Dy move us into a new area where chemical control of molecular geometry generates new and intriguing electronic structures. Despite a mature understanding of the microscopic origins of magnetic relaxation in complexes of the 3d metals,58Magnetic measurements of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy\u2013F\u2013Dy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC unit, which should provide a platform to examine in great detail the exchange interactions between pure mJ states. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tDy PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC units could be coupled through a radical ligand bridge which also represents a promising direction for Ln SMMs.62Given the properties of the molecules presented herein, realised by following a simple design strategy, we anticipate that such motifs could be employed with other contemporary Ln chemistry, using the idea of \u2018building-block engineering\u2019.TMSH2, [K(CH2Ph)], [Ln(CH2Ph)3(THF)3] and [Ln(BIPMTMS)(CH2Ph)(THF)] were prepared as described previously.261H, 13C, 29Si, and 31P NMR spectra were recorded on a Bruker 400 spectrometer operating at 400.2, 100.6, 79.5, and 162.0 MHz respectively; chemical shifts are quoted in ppm and are relative to TMS and 85% H3PO4 (31P). FTIR spectra were recorded on a Bruker Tensor 27 spectrometer. Variable-temperature magnetic moment data for 2Dy, 10% 2Dy@2Y and 3% 2Dy@2Y were recorded in an applied dc field of 0.1 T on a Quantum Design MPMS XL5 superconducting quantum interference device (SQUID) magnetometer using doubly recrystallised powdered samples. Samples were carefully checked for purity and data reproducibility between several independently prepared batches for each compound examined. Care was taken to ensure complete thermalisation of the sample before each data point was measured and samples were immobilised in an eicosane matrix to prevent sample reorientation during measurements. Diamagnetic corrections were applied using tabulated Pascal constants and measurements were corrected for the effect of the blank sample holders and eicosane matrix. Solution magnetic moments were recorded at room temperature using the Evans method. CHN microanalyses were carried out by Tong Liu at the University of Nottingham. The compounds described herein can be classed as moderately air-/moisture-sensitive, but with adequate precautions they can be handled under a dry nitrogen atmosphere for extended periods with no sign of decomposition.All manipulations were carried out using Schlenk techniques, or an MBraun UniLab glovebox, under an atmosphere of dry nitrogen. Solvents were dried by passage through activated alumina towers and degassed before use or were distilled from calcium hydride. All solvents were stored over potassium mirrors except for THF which was stored over activated 4 \u00c5 sieves. Deuterated solvent was distilled from potassium, degassed by three freeze\u2013pump\u2013thaw cycles and stored under nitrogen. BIPMTMSH2 in toluene (10 ml) was added dropwise to a precooled (\u201378 \u00b0C) suspension of [Dy(CH2Ph)3(THF)3] in toluene (15 ml). The resulting orange suspension was warmed to room temperature with stirring over 16 h then refluxed for 10 minutes to afford a yellow solution. Volatiles were removed in vacuo and the resulting yellow residue recrystallised from hot toluene (4 ml) to afford colourless crystals of 1Dy on cooling to room temperature. Yield: 2.02 g, 63%. Anal. calcd for C62H77DyN4P4Si4: C, 58.33; H, 6.08; N, 4.39%. Found: C, 58.38; H, 6.05; N, 4.36%. FTIR \u03bd/cm\u20131 (Nujol): 1306 (w), 1106 (m), 1047 (w), 841 , 697 (w), 610 (w), 553 (w), 522 (w). Magnetic moment : \u03bceff = 10.61 \u03bcB.BIPMTMSH2 in toluene (10 ml) was added dropwise to a precooled (\u201378 \u00b0C) suspension of [Y(CH2Ph)3(THF)3] in toluene (15 ml). The resulting orange suspension was warmed to room temperature with stirring over 16 h then refluxed for 10 minutes to afford a yellow solution. Volatiles were removed in vacuo and the resulting yellow residue recrystallised from hot toluene (4 ml) to afford colourless crystals of 1Y on cooling to room temperature. Yield: 2.91 g, 48%. Anal. calcd for C62H77N4P4Si4Y: C, 61.90; H, 6.45; N, 4.66%. Found: C, 61.74; H, 6.45; N, 4.57%. 1H NMR : \u03b4 0.31 3), 0.39 3), 2.40 P2), 7.06 , 7.25 , 7.79 , 7.94 ppm. 13C{1H} NMR : \u03b4 5.11 (NSi(CH3)3), 6.16 (NSi(CH3)3), 19.87 P2), 66.50 , 126.88 (Ar-C), 127.68 (Ar-C), 128.50 (Ar-C), 130.57 (Ar-C), 132.32 (Ar-C), 134.10 (Ar-C), 135.08 (Ar-C), 141.81 ppm. 31P{1H} NMR : \u03b4 7.50 , 21.74 P2) ppm. 29Si{1H} NMR : \u03b4 \u20138.34 (NSi(CH3)3), \u20132.59 (NSi(CH3)3) ppm. FTIR \u03bd/cm\u20131 (Nujol): 1305 (w), 1242 (w), 1105 (m), 1045 (m), 841 , 696 (s), 597 (w), 522 (m).BIPMTMS)(BIPMTMSH)] and [K(CH2Ph)] . The resulting orange suspension was allowed to slowly warm to room temperature with stirring over 16 h to afford a yellow solution. 18C6 in THF was then added and the resulting yellow solution stirred for 2 h. The solution was then reduced in volume to ca. 2 ml, which afforded yellow crystals of 2Dy on standing at room temperature. Yield: 0.30 g, 43%. Anal. calcd for C82H116DyKN4O8P4Si4: C, 57.16; H, 6.78; N, 3.25%. Found: C, 56.67; H, 6.67; N, 3.39%. FTIR \u03bd/cm\u20131 (Nujol): 1350 (w), 1303 (w), 1070 (s), 959 (m), 848 (m), 760 (m), 744 (s), 699 (m), 634 (m), 523 (s). Magnetic moment : \u03bceff = 11.16 \u03bcB.THF (15 ml) was added to a precooled (\u201378 \u00b0C) mixture of [Dy(BIPMTMS)(BIPMTMSH)] and [K(CH2Ph)] . The resulting orange suspension was allowed to slowly warm to room temperature with stirring over 16 h to afford a yellow solution. 18C6 in THF was then added and the resulting yellow solution stirred for 2 h. The solution was then reduced in volume to ca. 2 ml, which afforded yellow crystals of 2Y on standing at room temperature. Yield: 1.26 g, 60%. Anal. calcd for C82H116KN4O8P4Si4Y: C, 59.71; H, 7.09; N, 3.40%. Found: C, 59.01; H, 6.92; N, 3.56. 1H NMR : \u03b4 1.84 3), 4.93 2O)6) 7.30 , 8.05 . 13C{1H} NMR : \u03b4 6.11 (NSi(CH3)3), 53.70 P2), 70.13 (((CH2)2O)6), 127.58 (Ar-C), 128.76 (Ar-C), 134.00 (Ar-C), 145.19 ppm. 31P{1H} NMR : \u03b4 1.55 ppm. 29Si{1H} NMR : \u03b4 \u201311.34 (NSi(CH3)3) ppm. FTIR \u03bd/cm\u20131 (Nujol): 1351 (w), 1303 (w), 1067 (s), 960 (m), 848 (m), 760 (m), 743 (s), 700 (m), 635 (m), 523 (s).THF (15 ml) was added to a precooled (\u201378 \u00b0C) mixture of [Y(BIPM\u20136 mbar or better was maintained. The sample temperature was monitored via silicon PIN diode and controlled using an Oxford Instruments ITC 503 Intelligent Temperature Controller. Photo-excitation was provided, off-axis by a 10 mW 375 nm coherent cube laser diode with an unfocussed spot size of \u223c4 mm. The photoluminescence was collected using a collimating lens and focussed onto the slit of a 1 m, single 1200 lines mm\u20131 grating spectrometer. The signal was detected using a Hamamatsu photon counting head and Stanford Research Systems SR400 gated photon counter from where it was read-in and displayed on a PC using a custom built LabView program.The sample was installed in a custom bored-out copper support and sealed with a sapphire window in a glove box environment before being transferred to the cold finger of a recycling He cryostat in which a vacuum of 109 configuration of DyIII was modelled with a complete active space of 9 electrons in 7 orbitals, where 21 sextets, 224 quartets and 158 doublets were included in the orbital optimisation and 21 sextets, 128 quartets and 130 doublets were mixed by spin-orbit coupling. The ab initio results were then parameterised by a set of crystal field parameters,12For all calculations the Dy atoms were treated with the ANO-RCC-VTZP basis, the N and C donors and the P atoms with the ANO-RCC-VDZP basis, while all other atoms were treated with the ANO-RCC-VDZ basis.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We compiled a list of 11\u2009016 unique structures of small-molecule ligands bound to proteins representing 750\u2009873 protein\u2013ligand atomic interactions, and analyzed the frequency, geometry and the impact of each interaction type. The most frequent ligand\u2013protein atom pairs can be clustered into seven interaction types. As the protein databank (PDB) recently passed the cap of 123\u2009456 structures, it stands more than ever as an important resource not only to analyze structural features of specific biological systems, but also to study the prevalence of structural patterns observed in a large body of unrelated structures, that may reflect rules governing protein folding or molecular recognition. Here, we compiled a list of 11\u2009016 unique structures of small-molecule ligands bound to proteins \u2013 6444 of which have experimental binding affinity \u2013 representing 750\u2009873 protein\u2013ligand atomic interactions, and analyzed the frequency, geometry and impact of each interaction type. We find that hydrophobic interactions are generally enriched in high-efficiency ligands, but polar interactions are over-represented in fragment inhibitors. While most observations extracted from the PDB will be familiar to seasoned medicinal chemists, less expected findings, such as the high number of C\u2013H\u00b7\u00b7\u00b7O hydrogen bonds or the relatively frequent amide\u2013\u03c0 stacking between the backbone amide of proteins and aromatic rings of ligands, uncover underused ligand design strategies. Significant progress in high-throughput X-ray crystallography9Several approaches have been developed for large-scale analysis of protein\u2013small molecule interactions, such as SuperStar, or the method implemented to build the Relibase database.A statistical analysis of the nature, geometry and frequency of atomic interactions between small molecule ligands and their receptors in the PDB could inform the rational optimization of chemical series, help in the interpretation of difficult SAR, aid the development of protein\u2013ligand interaction fingerprints, and serve as a knowledge-base for the improvement of scoring functions used in virtual screening. To the best of our knowledge, such public resource is currently missing.Here, we analyze the frequency of common atomic interactions between protein and small molecules observed in the PDB. We find that some interactions occur more frequently in fragments than drug-like compounds, or in high-efficiency ligands than low-efficiency ligands. We next review in detail each of the most frequent interactions and use matched molecular pairs to illustrate the impact of these atomic interactions on binding affinity.We extracted from the PDB all X-ray structures of small-molecules in complex with proteins, with a resolution \u22642.5 \u00c5, resulting in a collection of 11\u2009016 complexes. To be considered as a ligand, the compound had to meet several criteria such as being a small molecule and be of interest for medicinal chemistry applications for compounds with high FQ are 27 and 1.7, respectively, and 21 and 0.2, respectively, for compounds with low FQ. Both groups showed similar profiles for other properties like polar surface area (median PSA: 95.3 vs. 89.8 \u00c52), hydrogen bond acceptors (median HBA: 5 for both), and hydrogen bond donors (median HBD: 2 for both). Taken together these results show that small-molecule ligands that bind their target with high efficiency are more hydrophobic, and that hydrophobic interactions are a driving factor for the increased ligand efficiency.We find that hydrophobic interactions are more frequent in high-efficiency ligands. In particular, the frequency of hydrogen bonds is reduced from 59% to 34% of that of hydrophobic contacts in efficient binders, and the frequency of salt bridges is more than halved, from 13% to 7% . This obSince fragments are typically binding their targets with higher ligand efficiency than larger ligands, we asked whether hydrophobic interactions were also more frequent in protein-fragment complexes. The frequency of each interaction type was calculated for two random groups of 1500 protein\u2013ligand complexes, one with fragment molecules (HA \u2264 20), the other with drug-like molecules (30 \u2264 HA \u2264 50) . Unlike 23The higher prevalence of polar interactions in fragments compared to drug-like compounds could be seen as a requirement for high solubility, as fragments are tested at high concentrations. It also reflects the fact that fragments are freer than larger compounds to adopt binding poses that will optimally satisfy the geometric constraints of high-efficiency interactions, such as electrostatic or hydrogen-bonds.24Together, these results show that fragments are using polar interactions to gain maximum binding efficiency from a limited number of interactions, but as small-molecule ligands are optimized, geometric constraints associated with polar bonds are more challenging to satisfy, and the contribution of hydrophobic interactions increases.To gain further insight, we next analyzed in detail the composition, geometry, frequency, protein side-chain preference, and impact towards binding affinity of each protein\u2013ligand interaction type in the PDB.From our analysis, hydrophobic contacts are by far the most common interactions in protein\u2013ligand complexes, totalizing 66\u2009772 contacts between a carbon and a carbon, halogen or sulfur atom . Hydroph\u20131 compared with a purely hydrophobic interaction.27Contacts involving an aromatic or aliphatic carbon in the receptor and an aliphatic carbon in the ligand were observed in 8899 and 8974 instances, respectively Table S2. We obse\u20131 or a 3.2-fold increase in binding constant per methyl group.29Hydrophobic interactions are the main driving force in drug\u2013receptor interactions. The benefit of burying a solvent-exposed methyl group on a ligand into a hydrophobic pocket of a protein is about 0.7 kcal molvs. 7551, respectively). Proteins were more often hydrogen-bond donors than acceptors . Surprisingly, glycine was the most frequent hydrogen-bond acceptor, and the second most frequent donor, probably due to the absence of side-chain to mask backbone atoms, and increased backbone flexibility to better satisfy the spatial constraints of hydrogen-bonds .We find that hydrogen bonds were the second most frequent type of interactions observed in our collection of protein\u2013ligand complexes, with a total of 28\u2009577 . N\u2013H\u00b7\u00b7\u00b7Os Fig. S6. Arginins Fig. S6. Among Os Fig. S6. The moss Fig. S6. Serine s Fig. S6. Finally PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and OH/NH.We found that heavy atoms in N\u2013H\u00b7\u00b7\u00b7O, N\u2013H\u00b7\u00b7\u00b7N, and O\u2013H\u00b7\u00b7\u00b7O hydrogen bonds were all separated by similar median distances of approximately 3.0 \u00c5 . This va\u20131 to \u20134.7 kcal mol\u20131.39Hydrogen bonds are the prevailing directional intermolecular interactions in biological complexes,Among numerous examples, a series of potent thrombin inhibitors shows a remarkable increase in binding affinity (>500-fold) through simple addition of hydrogen-donating ammonium group .40 In th41The third most frequent protein\u2013ligand contacts in the PDB were aromatic interactions . Interac6 (IC50 = 7 nM), the phenyl ring is positioned to allow \u03c0-stacking interaction with H524 without the phenyl ring is l00-fold less potent. While \u03c0-stacking interaction can increase the binding affinity of the inhibitor for its target, it has been pointed out that reducing the number of aromatic rings of a molecule might improve its physicochemical properties, such as solubility.Interactions involving aromatic rings are major contributors to protein\u2013ligand recognition and concomitantly to drug design.ith H524 , while avs. 708 interactions, Table S2The fourth most frequent interactions (13\u2009600 contacts) were C\u2013H\u00b7\u00b7\u00b7O hydrogen bonds, the existence of which is well documented .48,49 WhThe median distance of the C\u2013H\u00b7\u00b7\u00b7O hydrogen bonding was 3.4 \u00c5, which is 0.4 \u00c5 longer than traditional hydrogen bonds , and distances separating the two heavy atoms were rarely lower than 3.2 \u00c5 . The ang50\u03b1\u2013H\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC interactions are about one-half the strength of an NH\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC hydrogen bond.\u03b1\u2013H\u00b7\u00b7\u00b7O hydrogen should be better interpreted as secondary interactions, as they are frequently accompanied by bifurcated N\u2013H\u00b7\u00b7\u00b7O hydrogen bonds.2 by a methyl group on the thiazole ring of compound 8 was the fifth most frequent interaction type in our analysis (7276 interactions) .The contact between a positively charged nitrogen and a negatively charged oxygen (actions) . The numN,N-dimethylamino tail of 10 forms a salt bridge with D831 in the kinase domain of epidermal growth factor receptor (EGFR) potency was reduced by more than 800-fold.71Salt bridges contribute little to protein stability as the favorable binding energy obtained from forming a salt bridge is not sufficient to offset the energetic penalty of desolvating charged groups.r (EGFR) . When thInteractions between an amide group and an aromatic ring were the sixth most frequently observed . In thesKi between a matched pair of oxazole-containing factor Xa inhibitors was attributed to the influence of the dipole of the oxazole ring on the amide\u00b7\u00b7\u00b7\u03c0 interaction with the trimethylated ammonium group (compound 17), indicated that the cation\u2013\u03c0 interaction contributed to a 60 fold increase in potency (Many drug\u2013receptor interactions involve cation\u2013\u03c0 interactions. One of the earliest examples is the recognition of acetylcholine (ACh) by the nicotinic acetylcholine receptor (nAChR). Similarly, GABA,3 receptor potency .Although specific interactions involving halogen atoms were much less frequent than the other interactions discussed above we included them in our analysis as the impact of these interactions is regularly debated among medicinal chemists.We found 351 interactions of the type C\u2013X\u00b7\u00b7\u00b7Y where Y was either from protein side chain or backbone. These halogen bonding (XB) interactions96From the 351 interactions, those involving a chlorine atom were the most frequent (222 interactions), followed by bromine (91 interactions) and iodine (38 interactions) Table S2. This isHalogen bonds are well-characterized intermolecular interactions in small molecules, and have many applications in fields as diverse as crystal engineering and supramolecular chemistry.102a]pyrimidine PDE2a inhibitors.meta position of inhibitor 19 scale\" fill=\"currentColor\" stroke=\"none\">O (or N\u2013C) and X\u00b7\u00b7\u00b7C\u20131) associated with fluorine multipolar interaction.108Compared with other interactions, little attention has been given to the role of multipolar interactions in molecular recognition events of chemical and biological systems.24 (IC50 = 106 nM) by fluorine in 25 (IC50 = 14 nM) improved the potency by approximately 8-fold (para-position of the ring in the crystal structure of 24 confirms a short distance from the peptide carbonyl carbon and amide nitrogen of L104 and V105, respectively, indicative of a multipolar interaction (A series of p38\u03b1 inhibitors recently illustrated the potential impact of a fluorine multipolar interaction.y 8-fold . Introdueraction .We presented here a statistical analysis of the nature, geometry and frequency of atomic interactions between small molecule ligands and their receptors available in the PDB. The enrichment of polar interactions in bound fragments, but hydrophobic contacts in optimized compounds reflects the challenge of overcoming desolvation penalty during lead optimization. This unbiased census recapitulates well-known rules driving ligand design, but also uncovers some interaction types that are often overlooked in medicinal chemistry. This analysis will help in the interpretation of difficult SAR, and may serve as a knowledgebase for the improvement of scoring functions used in virtual screening.The author declare no competing interests.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file."}
+{"text": "Binding of C2H2 in MFM-300(VIII) showing interactions to O\u2013H, carboxylate O-centres and intermolecular packing. III) {[VIII2(OH)2(L)], LH4 = biphenyl-3,3\u2032,5,5\u2032-tetracarboxylic acid} is accompanied by deprotonation of the bridging hydroxyl groups to afford isostructural MFM-300(VIV), [VIV2O2(L)]. The precise role of the hydroxyl groups, O-carboxylate centres and \u03c0\u2013\u03c0 interactions in the supramolecular binding of C2 hydrocarbons in these materials has been determined using neutron diffraction and inelastic neutron scattering, coupled with DFT modelling. The hydroxyl protons are observed to bind to adsorbed unsaturated hydrocarbons preferentially in MFM-300(VIII), particularly to C2H2, which is in a sharp contrast to MFM-300(VIV) where interactions with O-carboxylate centres and \u03c0\u2013\u03c0 interactions predominate. This variation in structure and redox leads to notably higher separation selectivity for C2H2/CH4 and C2H4/CH4 in MFM-300(VIII) than in MFM-300(VIV). Significantly, owing to the specific host\u2013guest interactions, MFM-300(VIII) shows a record packing density for adsorbed C2H2 at 303 K and 1 bar, demonstrating its potential for use in portable acetylene stores.Fine tuning of host\u2013guest supramolecular interactions in porous systems enables direct control over the properties of functional materials. We report here a modification of hydrogen bonding and its effect on guest binding in a pair of redox-active metal\u2013organic frameworks (MOFs). Oxidation of MFM-300(V Porous materials have shown great promise for substrate binding, storage, separation, and delivery due to their unique host\u2013guest interactions.via binding of the unsaturated species to metal centres.2 hydrocarbons, in particular for distinguishing between alkenes and alkynes.Metal\u2013organic frameworks (MOFs) with extraordinary tuneability of the pore geometry and surface functionality can facilitate control over adsorptive separation of small molecule hydrocarbons, and their high surface areas generally give rise to a large working capacity for dynamic separation.III), {[VIII2(OH)2(L)] LH4 = biphenyl-3,3\u2032,5,5\u2032-tetracarboxylic acid}, and its oxidised iso-structural counterpart MFM-300(VIV), [VIV2O2(L)], provide a unique platform to study the precise role of the \u2013OH group in the supramolecular binding of hydrocarbon molecules.via neutron powder diffraction (NPD) and inelastic neutron scattering (INS), coupled with DFT modelling. These complimentary studies find that the hydroxyl protons play an important role in binding of C2H2/C2H4 molecules in the pores in contrast to the case of MFM-300(VIV) where adsorbed C2H2/C2H4 molecules are found to be remote from the bridging oxy groups. The pore environment of MFM-300(VIII) is found to be optimal for binding of C2H2 and leads to an exceptional packing density of up to 0.38 g cm\u20133 of adsorbed C2H2 at 303 K and 1 bar.We were interested in assessing the role of hydroxyl groups within porous MOFs for the selective binding of light hydrocarbons for potential adsorptive separation. We sought to modify the hydroxyl groups within the pore while still retaining the overall structure and porosity of resultant MOF. MFM-300(VIII) was synthesised following our previously reported methodI4122. Adjacent pair of VIII centres are bridged by two carboxylates and a \u03bc2-hydroxyl group forming an extended chain of [V2(OH)2O4]\u221e along the c axis. The carboxylate ligands further bridge the [V2(OH)2O4]\u221e chains to give a three dimensional network with square-shaped channels decorated with hydroxyl groups pointing into the pores (IV) was obtained by heating the as-synthesised MFM-300(VIII) sample at 150 \u00b0C under a flow of O2 for 16 h. MFM-300(VIV) retains the space group I4122 and the overall framework structure. The V\u2013O bond length involving the bridging oxygen reduces upon oxidation, and loss of the hydroxyl hydrogen atom in MFM-300(VIV) is confirmed. Analysis of the high pressure CO2 adsorption isotherm at 273 K by DFT/Monte-Carlo methods gives surface areas of 1892 and 1565 m2 g\u20131, pore size distributions (PSD) centred at 5.2 and 5.4 \u00c5, and cumulative pore volumes of 0.490 and 0.481 cm3 g\u20131 for MFM-300(VIII) and MFM-300(VIV), respectively. Another pair of MOFs, MIL-47(VIII) and MIL-47(VIV), has structural similarity to MFM-300(V). However, MIL-47(VIII) and MIL-47(VIV) show significantly different porosity owing to framework flexibility as confirmed by CO2 and H2O adsorption,cis-\u03bc2-OH groups thus yielding highly robust isostructural frameworks for both VIII and VIV materials.MFM-300 is 8.1 and 6.9 mmol g\u20131 at 273 and 303 K, respectively, and those for MFM-300(VIV) are 7.8 and 6.1 mmol g\u20131 under the same conditions (2H2 in MFM-300(VIII) is calculated to be 0.38 g cm\u20133 at 303 K, which is 184 times higher than the safe compression limit for C2H2 storage at 2.0 bar. This value is comparable to the highest value of 0.38 g cm\u20133 observed in [Zn2(adc)2(dabco)] octane] but at a lower temperature of 296 K,\u20133 at 296 K)\u20133 at 296 K).2H2 uptake of MFM-300(VIII) is 0.3 mmol g\u20131 higher than that of MFM-300(VIV) at 1.0 bar, while the difference is significantly greater (\u0394 = 1.7 mmol g\u20131) in favour of MFM-300(VIII) at 0.1 bar than in MFM-300(VIV) at low surface coverage; with increasing gas loading, less surface sites are available and guest\u2013guest interaction start to be significant in driving the gas adsorption, leading to a reduced difference in gas uptake.Gravimetric adsorption isotherms for CH73\u2013303 K . At 1.0 nditions . The denr Fig. S1. Given t2 hydrocarbons of both MFM-300(VIII) and MFM-300(VIV) track the order of C2H2 > C2H4 > C2H6 at 1.0 bar and 273\u2013303 K (III) follows the order of C2H2 > C2H6 > C2H4, while that in MFM-300(VIV) follows C2H6 > C2H2 > C2H4. At low surface coverage, the effect of MOF\u2013gas interaction is more pronounced in driving physical adsorption processes. The inversion of uptakes of C2H6 and C2H2 in MFM-300(VIII) and MFM-300(VIV) indicates that the host\u2013guest binding mechanism is very sensitive to the presence of hydroxyl groups in the pore and to the small difference in chemical structure of these hydrocarbon molecules.The uptake capacities of C73\u2013303 K . This is2Hn/CH4 for MFM-300(VIII) and MFM-300(VIV) were calculated at 303 K and 0\u20131 bar (III) outperforms MFM-300(VIV) for the selectivities of C2H2/CH4 and C2H4/CH4 by ca. 40%. This is likely due to the presence of stronger binding sites to unsaturated hydrocarbons in MFM-300(VIII). The C2H6/CH4 selectivity of MFM-300(VIII) is between 22\u201314, and is nearly identical to that of MFM-300(VIV) under same conditions. The C2H6/CH4 selectivity of MFM-300(V) is comparable with the benchmark MOFs, [Fe2(dobdc)] (20 at 313 K and 1.0 bar)2H6 in MFM-300(VIII) is as high as 5.0 mmol g\u20131 at 303 K and 1.0 bar, which is comparable to that of MOF-74(Fe) (5.0 mmol g\u20131 at 318 K and 1.0 bar) and much higher than that of UTSA-35a (2.4 mmol g\u20131 at 296 K and 1.0 bar), suggesting that MFM-300(VIII) is a promising material for separation of C2H6 from CH4.The IAST selectivities of equimolar mixture of C 0\u20131 bar . MFM-300Qst, for C2H2 in MFM-300(VIII) is centered at 32.0 \u00b1 0.1 kJ mol\u20131 without notable variation as a function of surface coverage. In contrast, the Qst of C2H2 in MFM-300(VIV) is estimated as 26.0 \u00b1 0.4 kJ mol\u20131 at low pressure and increases gradually with increasing gas loading to 30.1 \u00b1 0.1 kJ mol\u20131 at 4.0 mmol g\u20131. Interestingly, the Qst value for C2H2 in MFM-300(VIII) is significantly higher than that of MIL-53(Al) (19.2 kJ mol\u20131), which adopts similar structural feature but with trans-orientated hydroxyl groups at the metal centre.\u20131) incorporating open CuII center.Qst values of C2H6 for both compounds are similar and lie within the range of 28\u201332 kJ mol\u20131. The Qst value of C2H4 in MFM-300(VIII) (28\u201331 \u00b1 0.1 kJ mol\u20131) is also higher than that of MFM-300(VIV) (24\u201326 \u00b1 0.1 kJ mol\u20131). Finally, the Qst values of CH4 are similar for both compounds and within the range of 17\u201319 kJ mol\u20131.The isosteric heat of adsorption, i.e., C2H2 and C2H4), the uptake capacity and Qst are much higher in MFM-300(VIII) than in MFM-300(VIV) at low pressure, indicating the presence of possible \u2013OH\u00b7\u00b7\u00b7C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC interactions. In comparison, for saturated hydrocarbons , the Qst in both compounds are similar, suggesting the presence of similar host\u2013guest binding mechanisms for saturated hydrocarbons in MFM-300(VIII) and MFM-300(VIV). The observed undulations in the Qst plots may suggest a packing effect reflecting optimum packing of the substrate within the pore at specific loadings.For unsaturated hydrocarbons , NPD experiments were carried out for gas-loaded samples of MFM-300(VIII) and MFM-300(VIV) at 7 K. Comparison of the NPD patterns for bare and gas-loaded MOFs indicated that no major structural phase change took place on gas-loading, and NPD data enabled full structural analysis via Rietveld refinement to yield positions, orientations and occupancies of adsorbed gas molecules within the framework hosts.In order to determine the preferred binding sites for C2D2/V, analysis of the NPD data revealed two crystallographically independent sites for C2D2 (I and II) scale\" fill=\"currentColor\" stroke=\"none\">CC distance of 3.016(1) \u00c5 (c.g. = centre of gravity), indicating a moderate hydrogen bond between the \u03c0-electrons of C2D2 and the HO\u2013V moiety. C2D2II interacts with the carboxylate O atoms with a D\u00b7\u00b7\u00b7O distance of 2.608(1) and 2.871(1) \u00c5. The HOH\u00b7\u00b7\u00b7c.g. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC distance is shorter than that found in the C2D2-loaded MFM-300(Al) [3.26(1) \u00c5] studied by NPD at 10 K.III) is likely attributed to the difference in the acidity between the Al\u2013OH and V\u2013OH bridges, and is consistent with the observation in the corresponding CO2-loaded MFM-300 systems where adsorbed CO2 binds to V\u2013OH groups more strongly than to the Al\u2013OH group.2D2I and the aromatic benzene rings in the carboxylate ligand, with a c.g. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC\u00b7\u00b7\u00b7c.g.phenyl distance of 3.591(2) \u00c5. Further dipole interactions are observed between adsorbed C2D2 molecules on sites I and II in a T-shape arrangement with a D\u00b7\u00b7\u00b7c.g. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC distance of 3.190(1) \u00c5 scale\" fill=\"currentColor\" stroke=\"none\">CC = 3.178(1) \u00c5].2D2 molecules was obtained by free refinement against the NPD data. The occupancies of C2D2I and C2D2II are found to be 0.55 and 0.45, respectively, at a loading of 1.0 C2D2/V, indicating that site I which contacts to the hydroxyl group directly is more favourable at low pressure. As the loading increases to 1.76 C2D2/V, the occupancies of C2D2I and C2D2II are found to be 0.82 and 0.94, respectively, indicating the presence of intermolecular cooperative binding between adsorbed gas molecules.At a loading of 1.0 C and II) . C2D2I i2D2-loaded MFM-300(VIV) also shows two independent binding sites for adsorbed C2D2 molecules with retention of the framework structure. C2D2I\u2032 interacts with the carboxylate group with D\u00b7\u00b7\u00b7OCOO distances of 2.34(1) and 2.43(1) \u00c5, which are slightly longer than the H2H2C\u00b7\u00b7\u00b7OCOO hydrogen bond distance (2.2 \u00c5) observed in [Cu2(pzdc)2(pyz)] at 170 K ,COO separation of 3.12(1) \u00c5 found in C2D2-loaded MFM-300(VIII). This indicates a shift in the nature of the primary binding site on going from C2D2-loaded MFM-300(VIII) to C2D2-loaded MFM-300(VIV) scale\" fill=\"currentColor\" stroke=\"none\">CC\u00b7\u00b7\u00b7c.g.phenyl distance of 3.78(1) \u00c5. The shortest separation between the adsorbed C2D2 molecules and the bridging oxy group is 4.83(1) \u00c5.Analysis of the NPD data of C300(VIV) . \u03a0\u00b7\u00b7\u00b7\u03c0 ie.g., MgO) by forming hydrogen bonds between the acidic C\u2013H groups and the basic sites on the material surface. In this study, the absence of any notable binding interactions between adsorbed C2D2 molecules and the surface oxy groups is a direct result of the weak basicity of the oxy bridges in MFM-300(VIV), which, in turn, reflects the relative acidity of the hydroxyl bridges in MFM-300(VIII), consistent with the binding observed in C2D2-loaded MFM-300(VIII). In contrast to C2D2-loaded MFM-300(VIII), \u03c0\u00b7\u00b7\u00b7\u03c0 interactions are observed between the adsorbed C2D2I\u2032 and C2D2II\u2032 molecules in MFM-300(VIV) with a c.g.I\u2032\u00b7\u00b7\u00b7c.g.II\u2032 distance of 3.45(2) \u00c5 .Acetylene or propyne are frequently used as probes to determine the basicity of oxide materials (2D2 molecules within the two frameworks is compared in III) while the guest\u2013guest interaction is stronger in MFM-300(VIV). This result suggests that the proton on the bridging oxy group can not only affect the host\u2013guest binding through fine-turning of the pore surface chemistry, but also alter the subsequent guest\u2013guest interaction, thus controlling the gas adsorption and substrate packing within the pores.The packing of adsorbed C2D2-loaded MFM-300(VIII) and MFM-300(VIV) have also been optimised by DFT calculations at a loading of 2.0 C2H2/V (III) confirms that the adsorbed C2H2 molecules (i) interact with the hydroxyl groups in a side-on model scale\" fill=\"currentColor\" stroke=\"none\">CC = 2.56 \u00c5); (ii) form \u03c0\u00b7\u00b7\u00b7\u03c0 bonds with the phenyl rings of ligands scale\" fill=\"currentColor\" stroke=\"none\">CC\u00b7\u00b7\u00b7c.g.phenyl = 3.86 \u00c5); (iii) bind with the carboxylate oxygen atom via dipole interactions (H2H2C\u00b7\u00b7\u00b7Ocarboxylate = 2.88 \u00c5). In contrast, the DFT calculation for MFM-300(VIV) confirms (i) an absence of binding interaction between the adsorbed C2H2 molecules and the bridging oxy group; (ii) presence of \u03c0\u00b7\u00b7\u00b7\u03c0 interaction between C2H2 molecules and the phenyl rings of ligands scale\" fill=\"currentColor\" stroke=\"none\">CC\u00b7\u00b7\u00b7c.g.phenyl = 3.89 \u00c5); (iii) the adsorbed C2H2 molecules interact strongly with the carboxylate oxygen atom (H2H2C\u00b7\u00b7\u00b7Ocarboxylate = 2.77 \u00c5). The shift of the binding strength for host\u2013guest and guest\u2013guest interaction on going from MFM-300(VIII)\u00b74C2H2 to MFM-300(VIV)\u00b74C2H2 was clearly observed in the DFT calculation \u00b72.12C2H4 shows two binding domains for C2D4 (2D4I (occupancy = 0.56) is located close to the hydroxyl group with a c.g. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC\u00b7\u00b7\u00b7HOH distance of 3.737(1) \u00c5, which is much longer than the corresponding value of 3.016(1) \u00c5 observed in MFM-300(VIII)\u00b72.0C2D2. This result suggests the presence of a weaker hydrogen bond due to the reduced \u03c0-electron density in C2D4 compared to C2D2. C2D4II molecules (occupancy = 0.50) contacts with the carboxylate O atoms with D\u00b7\u00b7\u00b7Ocarboxylate distances in the range of 2.64(1)\u20133.03(2) \u00c5. The NPD analysis of C2D6-loaded MFM-300(VIII) suggests two sites for adsorbed C2D6 molecules, C2D6I molecule is aligned at a long distance to the \u2013OH group [distance c.g.C\u2013C\u00b7\u00b7\u00b7HOH = 3.87(1) \u00c5] as a result of no \u03c0-electron density and notable repulsion between the host and guest hydrogen atoms confirms no specific host\u2013guest interactions but van der Waals interactions between adsorbed CD4 molecules and the MOF interior [distance c.g.C\u2013C\u00b7\u00b7\u00b7HOH = 3.59(2) \u00c5] The Qst values for C2H2 and C2H4 are higher in MFM-300(VIII) than those in MFM-300(VIV) at low surface coverage, which is due to the stronger binding interaction between adsorbed C2H2 and C2H4 molecules with the framework host of MFM-300(VIII), particularly with the free acidic hydroxyl groups via hydrogen bonds. (ii) The Qst for C2H2 increases with increasing gas loading in MFM-300(VIV), while that for MFM-300(VIII) remains near-constant over the entire loading, which is due to the stronger intermolecular interaction between adsorbed C2H2 molecules within the pore of MFM-300(VIV) as a result of lack of specific surface binding sites. (iii) The Qst values of C2H6 and CH4 are similar for both MFM-300(VIII) and MFM-300(VIV) because of the absence of host\u2013guest hydrogen bonds via the hydroxyl groups and the van der Waals interaction drives the adsorption of C2H6 and CH4 in both materials.Combining the results of NPD experiments and DFT calculations, the differences in measured 2H2, C2H4, C2H6 and CH4 molecules in MFM-300(VIII) and C2H2 in MFM-300(VIV) shows a series of peaks in the range of 40\u201360 MeV attributed to the deformational modes of the hydroxyl group, and the disappearance of these peaks in the INS spectrum of MFM-300(VIV) unambiguously confirms the deprotonation of the bridging hydroxyl group upon oxidation.In addition to static crystallographic studies, we have combined INS and DFT to directly visualise the binding dynamics of adsorbed C300(VIV) . INS is III) to MFM-300(VIII)\u00b73C2H2 . On convergence, excellent agreement between the calculated and experimental structural models were obtained K to minimize the thermal motion of the adsorbed hydrocarbons and the host, reveals five major changes in peak intensity on going from bare MFM-300(VI)\u00b73C2H2 . Peaks Iobtained . Peaks Ine rings . The sig2H2 in MFM-300(VIV) is accompanied by the appearance of four new peaks in the INS spectrum . No major changes in the intensity at 40\u201370 MeV, which is in a sharp contrast to that in the INS study of MFM-300(VIII) .2H4-loaded MFM-300(VIII), small changes in intensity of peaks at 47 and 115 MeV were observed upon addition of C2H4, which are attributed to the interaction of adsorbed C2H4 with the hydroxyl and C\u2013H groups from phenyl rings, respectively (2H6-loaded MFM-300(VIII), it is clear that all peaks are ascribed to the adsorbed C2H6 molecules, and no specific host\u2013guest interaction was seen (4 in MFM-300(VIII) does not induce an obvious change in the INS spectra either , in excellent agreement with the NPD study and the Qst analysis.In the case of Cectively and S17\u2020was seen and S18\u2020III), both \u2013OH and \u2013CH/phenyl ring are active binding sites for adsorbed C2H2 molecules; (ii) in MFM-300(VIV), \u2013CH/phenyl ring is the sole binding sites for adsorbed C2H2 molecules via formation of supramolecular contacts. These observations are entirely consistent with the NPD studies and confirm the significant effects of bridging hydroxyl groups on the guest binding in the host on a molecular level.Thus, the INS and DFT results confirm that (i) in MFM-300(VIII/IV), incorporating redox-active vanadium centers. The oxidation of V centers from III to IV induces deprotonation of the bridging hydroxyl group, achieving fine-tuning of the pore environment. It has been confirmed in this study that these protons play a key role in adsorption of unsaturated hydrocarbons (both uptakes and isosteric heats of adsorption). A comprehensive study combining NPD, INS and DFT modelling has unambiguously determined the preferred binding sites and structural dynamics for these host\u2013guest systems. The differences in C2Hn/CH4 selectivities between MFM-300(VIII) and MFM-300(VIV) are fully rationalised. The acidic bridging hydroxyl groups in the pore provides specific binding activity to unsaturated hydrocarbons via formation of hydrogen bonds, leading to both high selectivity and packing efficiency of adsorbed gas molecules.We report the adsorption of light hydrocarbons in a pair of iso-structural MOFs, MFM-300(VThe authors declare no competing financial interests.Crystal structure dataClick here for additional data file.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Structural, spectroscopic and magnetic methods have been used to characterize the tris(carbene)borate compound PhB(MesIm)3Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN as a four-coordinate manganese(iv) complex with a low spin (S = 1/2) configuration. 3Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN as a four-coordinate manganese(iv) complex with a low spin (S = 1/2) configuration. The slow relaxation of the magnetization in this complex, i.e. its single-molecule magnet (SMM) properties, is revealed under an applied dc field. Multireference quantum mechanical calculations indicate that this SMM behavior originates from an anisotropic ground doublet stabilized by spin\u2013orbit coupling. Consistent theoretical and experiment data show that the resulting magnetization dynamics in this system is dominated by ground state quantum tunneling, while its temperature dependence is influenced by Raman relaxation.Structural, spectroscopic and magnetic methods have been used to characterize the tris(carbene)borate compound PhB(MesIm) Strong spin\u2013orbit coupling can lead to SMM properties in complexes having f1 electron configurations. For example, the SMM behaviour of the 5f1 U(v) complex, (trenTIPS)U(O) (trenTIPS = {N(CH2CH2NSiiPr3)3}3\u2013) has been attributed to an energy gap between the MJ = \u00b13/2 ground Kramers doublet and the lowest-lying excited Kramers doublet (either MJ = \u00b11/2 or MJ = \u00b15/2).1 Ce(iii) complexes have been similarly rationalized.9 SMM, [Ni(6-Mes)2]+ -3,4,5,6-tetrahydropyrimidin-2-ylidene),S = 1/2 Ni(i) complexes attributed the observed SMM properties to direct and Raman processes.S = 1/2 SMM systems is often difficult to establish as it can be induced by different mechanisms ,Since the discovery of a four-coordinate iron tris(carbene)borate complexes.ST = 1/2) Fe(v) complex, + borate ligands.vg>N]+ .16 Detaiiv) nitride, PhB(MesIm)3Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN (PhB(MesIm)3\u2013 = phenyltris(3-mesitylimidazol-2-ylidene)borato) which shows similar structural and spectroscopic properties to the Fe(v) complex. Magnetic measurements reveal that this new manganese complex shows slow relaxation of its magnetization, which is unexpected for a low spin (ST = 1/2) d3 configuration. A combined approach using a detailed experimental study of the relaxation time (in temperature and dc field) and electronic structure theory has been used to delineate the origin of the observed magnetization dynamics in this new SMM.Building from this work, we report in this contribution the synthesis, characterization, spectroscopic and magnetic properties of the isoelectronic Mnborate ligand precursor, PhB(MesImH)3OTf2, was prepared according to a literature procedure.131H NMR data were recorded on a Varian Inova 400 MHz spectrometer at 20 \u00b0C. Resonances in the 1H NMR spectra are referenced to residual C6D5H at \u03b4 = 7.16 ppm. IR spectra were recorded on a Perkin Elmer Spectrum Two spectrometer in THF solution. Cyclic voltammograms were measured using a CH Instruments Model 600B Series Electrochemical Analyzer/workstation in a glovebox with a glassy carbon working electrode. Elemental analysis data were collected by Midwest Microlab, LLC .All manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in an MBraun Labmaster glovebox. Glassware was dried at 150 \u00b0C overnight. Diethyl ether, 3(OTf)2 in Et2O (50 mL) at \u201378 \u00b0C. The resulting mixture was stirred at \u201378 \u00b0C for 15 min and then slowly warmed to room temperature. After stirring until the reaction mixture became golden yellow, the solvent was removed in vacuo. Tetrahydrofuran (15 mL) was added to the resulting yellow solid, followed by MnCl2 . The reaction was stirred at room temperature overnight and then dried under vacuum. After washing with Et2O and drying under vacuum, the product was obtained 3(OTf)2) as white solid. Colorless crystals were obtained by diffusion of pentane into a THF solution of the product at \u201335 \u00b0C. \u03bceff = 6.1(3) \u03bcB [\u03c7T = 4.6(1) cm3 K mol\u20131]. Elemental analysis calcd for C42H44BMnCl: (%) C 68.79, H 6.04, N 11.45 found (%) C 68.70, H 6.04, N 11.39.Lithium diisopropylamide was added to a precooled slurry of PhB(MesImH)1 , NaN3 and THF (100 mL). The mixture was stirred overnight under UV irradiation to yield a yellow solution. The solvent was removed in vacuo. Minor impurities were removed by washing with Et2O. The remaining solid was extracted into THF and filtered through Celite to yield a yellow solution. The solvent was removed in vacuo to afford a yellow solid 3MnCl). X-Ray quality crystals were obtained by the slow diffusion of n-pentane into a THF solution of the product at \u201335 \u00b0C. 1H NMR : \u03b4 12.8 ; 10.8 ; 9.3 ; 8.9 ; 7.0 ; 2.7 ; \u20133.2 ; \u201311.9 . Elemental analysis calcd for C42H44BMnN7\u00b70.5C4H8O (%) C 71.35, H 6.53, N 13.24; found (%) C 70.56, H 6.51, N 13.32.A 250 mL quartz round-bottom-flask was charged with 1 was measured using a Bruker APEX II Kappa Duo diffractometer equipped with an APEX II detector at 150(2) K. Complex 2 was investigated with synchrotron radiation at 100(2) K at the ChemMatCARS 15IDB beamline at the Advanced Photon Source at Argonne National Lab, Chicago. Additional details of the data collection and refinement are included in the ESI.Complex 1 were collected on a modified Bruker ESP-300 spectrometer with 100 kHz field modulation (4 G modulation amplitude) at 20 K through the utilization of an Oxford Instruments liquid helium flow cryostat. Simulations of EPR spectra were performed using the MATLAB EasySpin (v4.5) toolbox .17Continuous-wave (CW) X-band (9.32 GHz) EPR spectra of The magnetic measurements were carried out with the use of Quantum Design MPMS-XL SQUID magnetometer and PPMS-9 susceptometer. These instruments work between 1.8 and 400 K with applied dc fields ranging from \u20137 to 7 T (MPMS).2 sealed in a polyethylene bag and covered with mineral oil or directly in their frozen THF mother liquor within a sealed straw to prevent desolvation of the solid. Only experiments done with 2 maintained in frozen mother liquor and prepared under nitrogen atmosphere led to reproducible dc and ac magnetic data. No evaporation of the mother liquor was observed during these measurements. The mass of the sample was determined after the measurements and subsequent mother liquor evaporation. Prior to the experiments, the field-dependent magnetization was measured at 100 K in order to confirm the absence of any bulk ferromagnetic impurities. Ac susceptibility measurements were made with an oscillating field of 1 to 6 Oe with a frequency from 10 to 10\u2009000 Hz (PPMS). The magnetic data were corrected for the sample holder, mineral oil, mother liquor and the intrinsic diamagnetic contributions.Measurements were performed on a polycrystalline samples of Versa Probe II instrument equipped with monochromatic Al K source. The X-ray power of 50 W at 15 kV was used for 200 micron beam size. The instrument work function was calibrated to give a binding energy (BE) of 84.0 eV for Au 4f7/2 line for metallic gold and the spectrometer dispersion was adjusted to give BEs of 284.8, 932.7 and 368.3 eV for the C 1s line of adventitious carbon presented on the non-sputtered samples, Cu 2p3/2 and Ag 3d5/2 photoemission lines, respectively. The PHI dual charge compensation system was used on all samples. XPS spectra with the energy step of 0.1 eV were recorded using software SmartSoft-XPS v2.0 and processed using PHI MultiPack v9.0 at the pass energies of 46.95, 23.5, 11.75 eV for Mn 2p and Mn 3s, for N 1s, and for C 1s regions, respectively. Peaks were fitted using GL line shapes, i.e., a combination of Gaussians and Lorentzians with 0\u201350% Lorentzian content. Shirley background was used for curve-fitting.XPS experiments were performed using PHI ab initio ligand field theory (AILFT) approach.21Electronic structure calculations were performed using the ORCA 3.0.3 software package and MOLCAS 8.0.3Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN (2) is accessible by the same synthetic pathway used to prepare the related Fe(iv) nitrides (ii) complex PhB(MesIm)3MnCl (1) reveal 2 to be a four-coordinate Mn(iv) nitride complex with a low spin (ST = 1/2) d3 electron configuration that is subject to a Jahn\u2013Teller distortion. The molecular structure of 2 has been determined by single crystal X-ray diffraction (Table S1iv) nitrides,iv) centre. The manganese ion lies ca. 0.1 \u00c5 out of the plane defined by the carbon atoms of the tris(carbene)borate ligand, which is similar to the equivalent distance observed in the iron analogues. Similarly to the isoelectronic + complex,2 and the related Mn(iv) nitride + (TIMENxyl = tris[2-(3-xylylimidazol-2-ylidene)ethyl]-amine)xyl)Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN]+, which has a relatively flexible tris(carbene)amine ligand, significant elongation of one Mn\u2013C bond (by 0.15 \u00c5) occurs to lower the local symmetry at the Mn site. The greater rigidity of the tris(carbene)borate ligand in 2 evidently hinders such a distortion, and all Mn\u2013C distances are similar in length. Instead, the B\u2013Mn\u2013N angle in 1 is bent away from 180\u00b0 (B\u2013Mn\u2013N = 174.7\u00b0), whereas the equivalent angle in + is almost linear (179.4\u00b0).The manganese nitride complex, PhB(MesIm)nitrides .22 SpeciMnCl (1) in the p Table S1, reveali Table S1, that cr Table S1. The Mn\u20132 has also been spectroscopically characterized. The solution 1H NMR spectrum reveals eight paramagnetically-shifted resonances with relative integration appropriate for a three-fold symmetric complex. The solution magnetic moment, as determined by the Evans' method (\u03bceff = 2.2(3) \u03bcB; \u03c7T = 0.6(1) cm3 K mol\u20131), is consistent with a single unpaired electron and unquenched spin\u2013orbit coupling seen in the solid state (see below).Complex 2 have been investigated by cyclic voltammetry. As with the structural data, interesting differences with + are observed (2 and + can be reversibly reduced on the CV timescale, only the latter can be oxidized to Mn(v).v) state for the TIMENxyl ligand is in part due to the ability of apical bridgehead nitrogen atom of this ligand to bind to Mn in this higher oxidation state, forming a five-coordinate complex. Such additional stabilization is not possible with the tris(carbene)borate ligand.The redox characteristics of observed , likely 2 have been obtained from EPR spectroscopy. The frozen solution EPR spectrum (iv), I = 5/2, centre. The |MI\u3009 = |\u22125/2\u3009 and | = |\u20135/2\u3009 = |\u22125/2\u3009 and | and |MI = |\u20133/2 = |\u22123/2\u3009 manifolds at the low magnetic field edge of manifolds at the low magnetic field edge of g\u2225 are well resolved, and simulated with an A1(55Mn) = 300 MHz coupling. The g\u22a5 values are slightly split, with anisotropic 55Mn hyperfine couplings, as determined by simulation of the EPR spectrum, yielding g values and 55Mn couplings . The average g value, gav = [(g1 + g2 + g3)/3] = 2.096, is in agreement with the g factor, 2.1(1), determined from the magnetic susceptibility measurements detailed below. The electronic structure of 2 and EPR parameters remarkably resemble those of other low-spin trigonal d3 centres (Mn(iv) and Fe(v)) with tris(carbene) ligands.2 was also prepared for EPR characterization by suspending the solid in pentane to form a slurry. The X-band EPR spectrum of this slurry feature is too broad and not observed, however, the A355Mn hyperfine splitting of 204 MHz is distinctly observed in the EPR spectrum of the slurry parameters of the slurry sample match those observed for the solution. EPR spectra of this slurry collected at various temperatures (3.6 to 20 K) exhibit only the S = \u00bd Mn(iv) complex identifiable by the 55Mn hyperfine structure (see ESI3 Mn(iv) nitride are the same in both solution and the solid state.More detailed insights into the electronic structure of spectrum , top incs slurry , middle s slurry , top. The see ESI. In shor2. This oxidation state assignment has been confirmed using X-ray Photoelectron Spectroscopy (XPS). The standard position of the 2p3/2 peak for the Mn(iv) state is accepted to be in the range from 641.1 to 642.5 eV with the spin\u2013orbit splitting of 11.7 eV between Mn 2p3/2 and Mn 2p1/2 levels. The measured binding energies of Mn 2p3/2 for 2 are well within this range (2+ ions) is observed for MnPO4, but not for Mn2O3, despite the Mn(iii) state of both compounds.iv) complex, which clearly are more resolved for the Mn(ii) complex 1 ions in a SnO2 matrix.2 in comparison to that of 1 d3 electron configuration.In summary, the combined characterization data reveal that 2 have been studied by dc and ac techniques. Perfectly reproducible data were obtained when the compound was maintained below 200 K during the measurements and in its THF mother liquor, which prevents loss of solvent from the polycrystalline sample. At 200 K, the \u03c7T product has a value of 0.47 cm3 K mol\u20131 in good agreement with a magnetically isolated low-spin (ST = 1/2) Mn(iv) centre . At lower temperatures and as already detected by EPR (vide supra), the marked decrease of the \u03c7T product reveals the presence of antiferromagnetic interactions between Mn(iv) complexes. These intermolecular interactions were evaluated at \u20130.6(1) K (zJ/kB) by simulating the experimental data in the frame of the mean-field approximation\u03c7T vs. T values (red line in S = 1/2 species (M = 1.05 \u03bcB at 7 T & 1.85 K). The fit of the experimental data with an S = 1/2 Brillouin function confirms an average g factor around 2.10(2), which is in perfect agreement with that deduced from EPR .The magnetic properties of ) centre . When lo\u03c7\u2032) susceptibility consistent with the dc susceptibility (\u03c7\u2032\u2032). However, application of a dc field leads to the detection of a relaxation process in both components of the ac signal indicating a weak distribution of the relaxation time (\u03c4) and thus a relaxation mode that is dominated by a single relaxation process. The characteristic frequency of this relaxation mode continuously decreases when applying higher fields (to about 1000 Hz at 1 T) while the amplitude of the mode (\u03c70 \u2013 \u03c7\u221e) exhibits a maximum around 0.45 T suggests the presence of a thermally activated (Orbach) process of relaxation with a pre-exponential factor, \u03c40, of 5(1) \u00d7 10\u20136 s and an energy gap of only 5.1(5) K (3.5 cm\u20131). While the origin of the relaxation process will be discussed in more detail below, it is important at this stage to note the unusually small energy barrier and the large value of \u03c40 .The magnetization dynamics of this manganese nitride complex were probed by ac susceptibility measurements. In the absence of a dc field, the ac data, above 1.8 K and for frequencies up to 10 kHz, display a frequency independent in-phase K .5 cm\u20131. 2 were further analysed by means of an ab initio multireference methodology. A symmetrized model complex was first studied to obtain a qualitative description of the ground state nature of 2 and then these conclusions were corroborated by calculations of the full complex.The magnetic properties of the low-lying states of C3v group. Initial CASSCF calculations for the model system using the ORCA code indicate the following orbital sequence : dxy and dx2\u2013y2 at a reference energy (i.e. 0.0 cm\u20131), dz2 at 31\u2009000 cm\u20131 and at 32\u2009500 cm\u20131 leads to the correct spin state ordering and a NEVPT2 correction that preserves the ground state for the model structure. The lower energy orbitals in the CASSCF calculations are still , with a doubly degenerate ground state that corresponds predominantly (81% weight in both wavefunctions) to the and configurations. The next excited state is 7300 cm\u20131 higher in energy (10\u2009100 cm\u20131 in NEVPT2) and is not relevant for discussing the SMM properties of 2. Thus, magnetic anisotropy in this system emerges from the quantum mixing of the degenerate ground state by the spin\u2013orbit coupling (SOC), given that the dx2\u2013y2 and dxy orbitals are connected by the z component of the angular momentum operator.S = 1/2 states, separated by 470 cm\u20131 (676 K). The ground doublet of the model system presents a markedly uniaxial g tensor with gz = 5.15, gx = gy = 0.15. This strong anisotropy is significantly reduced in the full system due to the deviations from trigonal symmetry that breaks the degeneracy between dx2\u2013y2 and dxy orbitals, partially quenching the SOC mixing. In the full complex, the calculated ground state is split to an energy difference of 2103 cm\u20131 calculation including only doublets). This splitting leads to a marked decrease of the g tensor anisotropy of the ground doublet to values of gx = 1.940, gy = 1.942 and gz = 2.674, yielding a gav of 2.185, in satisfactory agreement with the values obtained for magnetization and EPR measurements. Equivalent CASSCF + RASSI calculations performed with MOLCAS code provide similar values with a first excited Kramers doublet at 1932 cm\u20131 (2800 K) and gx = 1.927, gy = 1.933 and gz = 2.790 values , direct and Raman mechanisms.The model complex was constructed from its original geometry, where the aryl groups were replaced with methyl substituents, symmetrizing the structure to the 2, which (i) should be dominated by QTM, direct and/or Raman mechanisms and (ii) cannot involve Orbach processes. With these elements in mind, the experimental relaxation time has been further analysed starting from its field dependence at 1.8 K (\u03bcBH \u226a kBT), most of the processes inducing a magnetization relaxation are weakly field dependent and thus they have been included as constant, k(T), in eqn (1).B1 = 24\u2009800(50) s\u20131, B2 = 15.6(5) T\u20132 and k(T) = 5427 s\u20131) confirming the key role of the quantum tunnelling of the ground doublet in the relaxation mechanism, in agreement with the theoretical predictions (TH4 term in eqn (1). The fit of the experimental data ) and including thermally active processes, which are either thermally activated (Orbach) or following a power law of the temperature for Raman mechanisms (with exponents ranging from 1 to more than 9).The temperature dependence of the relaxation at 0.45 T was analysed analogously, considering n) of 2.93(5) (with b = 1105 s\u20131 K\u20132.93 and \u03c4QTM fixed at 1.67 \u00d7 10\u20134 s). As discussed recently by Sessoli etal. for an ST = \u00bd VIV complex,ca. 2 \u00d7 10\u20134 s. Nevertheless, this relaxation mechanism is clearly assisted by Raman processes that rationalize the thermal dependence of the relaxation time.Remarkably, eqn (2) is able to reproduce the experimental data with a single power law and an exponent (iv) complex PhB(MesIm)3Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN (2) is a rare example of a low spin (S = 1/2) d3 complex. Its degenerate electron configuration is subject to a Jahn\u2013Teller distortion, which is manifested in 2 by bending of the B\u2013Mn\u2013N vector, similarly to the isoelectronic Fe(v) complex, +.\u20131 above the ground state, SMM properties observed by ac susceptibility measurements cannot rely on an Orbach mechanism and even if the traditional semi-logarithm \u03c4 vs. T\u20131 presentation of the experimental data could suggest the contrary. A detailed analysis of the field and temperature dependence of the relaxation time supports the theoretical CASSCF + RASSI calculations, and highlights the key role of the quantum tunnelling mechanism in the slow dynamics of the magnetization in this S = \u00bd species. Additionally, the signature of Raman processes could be detected in the thermal variation of the relaxation time. Since theoretically the Jahn\u2013Teller distortion significantly activates the quantum tunnelling mechanism, we anticipate that complexes where the structural distortion is smaller than in 2 will have much larger relaxation times. Investigations aimed at testing this hypothesis are currently in progress.Structural and spectroscopic methods reveal that the Mn(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "EPR spectroscopy and DFT calculations show that the site of reduction of porphyrinato gold(iii) complexes depends on the counterions X, the meso substituents R and the solvent. Meso tetraarylporphyrinato gold(iii) cations bearing different substituents at the aryl substituents were prepared and characterised. Their reversible one-electron reductions were studied by (spectro)electrochemical means as well as by selective chemical one-electron reduction using cobaltocene. The preferred location of the spin density, namely gold centred or porphyrin centred, was probed by electron paramagnetic resonance spectroscopy as well as by density functional theory calculations (spin densities). In all cases studied experimentally and theoretically, the gold(ii) valence isomer (5d9 electron configuration) is preferred over the porphyrin \u03c0 radical anion. In the hexafluorophosphate salt of the nitro derivative a further nitro \u03c0 radical anion valence isomeric species is significantly populated. In the presence of chloride ions this nitro \u03c0 radical anion/AuII valence isomeric equilibrium evolves towards the porphyrin \u03c0 radical anion. The electronic structures of the nitro \u03c0 radical and the AuII \u03c3 radical valence isomers could be calculated by DFT methods. The electron transfer pathway between the nitro \u03c0 radical anion and the AuII valence isomer is well described by the location of the hexfluorophosphate counterion, the Au\u2013N distances , the symmetric stretching mode of the NO2 substituent and a meso-nitrophenyl rotation. The specific geometric and electronic properties of the favoured gold(ii) \u03c3 radical valence isomer, namely counterion dislocation and \u03c3 symmetry of the redox orbital, might stabilise charge-shifted states [(gold(ii) porphyrin)-donor\u02d9+] by retarding the back electron transfer to give the ground state (gold(iii) porphyrin)-donor. This will guide the design of (photo-induced) electron transfer pathways with tetraarylporphyrinato gold(iii) complexes as electron acceptors. Based on early UV/Vis spectroscopic and theoretical studies the products of the reduction of gold(iii) porphyrins had been described as porphyrin-centred \u03c0 radical anions.H]+[A to HA is metal centred giving gold(ii) porphyrins . Disproportionation and dimerisation of [AuII(en)2]2+2+D has been suppressed by encapsulation in the pores of a zeolite (en = ethylenediamine).15The site of gold(rphyrins .9 Only aii) porphyrin HA (iii) porphyrin cation +[AH] with the strongly reducing naphthalene radical anion yielded a broad EPR resonance centred at gav = 2.06.197Au has been reported for the central g line .ii) complex B of hematoporphyrin IX with g\u22a5 = 2.035, g\u2225 = 1.970 and A\u22a5(197Au) = A\u2225(197Au) = 15 G at 130 K suggesting a less pronounced metal character (+]*[BF4] followed by disproportionation to AuIII and Au0 was unsuccessful as well (tht = tetrahydrothiophene).+[2a] was prepared via metallation and ion exchange of nitroporphyrin ester Ia to give 6][1a] with SnCl2/HCl to give the aurated amino-substituted porphyrin [2a]Cl (iii) ion was neither reduced nor removed. Hence, the AuIII porphyrins are stable under protic conditions. Counterion exchange of [Au(porph)][AuCl4] or [2a]Cl with KPF6 yielded the corresponding soluble hexafluorophosphate salts which are conveniently purified by column chromatography.Auration of the amino-substituted porphyrin n [2a]Cl . During [1a][PF6]\u2013[3a][PF6] are sufficiently soluble in dichloromethane. However, THF is required for acids 6][4b][PF and 6][4c][PF and even methanol is necessary for 6][4a]\u2013 counterions show the characteristic septet at \u03b4 = \u2013144 ppm in the 31P NMR spectra. Upon auration the characteristic high-field pyrrol NH resonances of the free-base porphyrin disappear. Furthermore, auration of the free-base porphyrins consistently shifts the pyrrole CH proton resonances to lower field by 0.5 ppm, in accordance with the positive charge of the metal centre. In the IR spectra, characteristic absorptions for group vibrations are found for the ester, amine, amide, nitro, trifluoromethyl and acid substituents at around 1719, 1618, 1690, 1520/1346, 1324 and 1716 cm\u20131, respectively. The [PF6]\u2013 counterions display absorptions for the PF stretching and deformation modes at 835\u2013843 and 556\u2013558 cm\u20131, respectively. ESI mass spectra fully confirm the integrity and stability of the complex cations displaying peaks at m/z values corresponding to the intact complex cation (see Exp. section).Ester-substituted complexes 3 = OnBu-substituted complex +[4b] all gold(iii) porphyrinato complexes +[1a], +[2a], +[3a], +[4a] and +[4c] show hypsochromically shifted Soret bands as compared to their corresponding free-base porphyrins Ia, IIa, IIIa, IVa and IVc porphyrinato complexes are non-emissive at room temperature in fluid solution as exemplarily checked for 6][1a][3a][PF and 6][4c][PF.With the exception of the electron-rich R+[1a], +[2a], +[3a], +[4b] and +[4c] 10\u20133 M in 0.1 M [nBu4N][PF6]/THF solution than +[Au(TPP)] to Au(TPP) (\u20130.97 V), while +[2a] (\u20130.99 V) is more difficult to reduce. Similarly, the potentials shift to more negative values in the series +[4c] (\u20131.00 V), +[4a] (\u20131.02 V) and +[4b] (\u20131.08 V), which is again explicable by the increasing electron donating nature of the substituents . Similar to the corresponding free-base porphyrins the shifts are only small.2 substituent . The nitro derivative +[1a] shows even further reversible reductions. Hence, one of the +[1a] reductions might be associated to the nitro substituent itself (vide infra).Several reversible reductions are observed for cations [1a]+, a+, [3a]+solution . For solobserved , Table 1KC > 1010 for the neutral complexes.The differences between the first and second reduction potentials amount to 0.60\u20130.68 V which corresponds to very high comproportionation constants of iii) complexes were reduced electrochemically to the neutral species in an optically transparent thin layer electrochemical (OTTLE) cell using THF as solvent (MeOH for +[4a]). In all cases, isosbestic points were observed corroborating the reversible nature of the first reduction process (+[Au(TPP)]/Au(TPP) process in THF porphyrin complexes were dissolved in CH2Cl2 (6]\u2013[1c][PF6][1a][4b][PF/6][4c][PF) or MeOH (6][4a] by CoCp2 in CH2Cl2 shows a well-resolved EPR pattern which could be reasonably simulated by a rhombic g tensor with hyperfine interaction to a single 197Au nucleus scale\" fill=\"currentColor\" stroke=\"none\">; natural abundance 100%) and superhyperfine coupling to four 14N nuclei . The high resolution allows a very good estimation of the high-field parameters while the low-field parameters are less well-resolved (Cu(TPP) complex scale\" fill=\"currentColor\" stroke=\"none\">; combined natural abundance 100%; g1 = 2.197, g2 = g3 = 2.054)A1 *[C with strongly electron donating meso substituents at the gold porphyrin a much larger hfc to 197Au has been reported [A1(197Au) = 180 G].2+D with the pure \u03c3 donor ligand ethylenediamine features a significantly larger hyperfine coupling to 197Au than Au(TPP) as well.Indeed, resolved , Fig. 4. = 197 G d] is sig1.000000,.000000 s1a\u20133a the broad EPR resonance corresponding to the AuII valence isomer is less well resolved due to the lower symmetry and hence different superhyperfine interactions . These data fit to gold(iii) porphyrin radical anions 2a\u2032 and 3a\u2032. For 4a\u20134c prepared in THF or MeOH, the corresponding gold(iii) porphyrin radical anions 4a\u2032, 4b\u2032 and 4c\u2032 are only present in negligible amounts (ii) valence isomers 2a\u20134c and their corresponding porphyrin radical anions 2a\u2032\u20134c\u2032 is in favour of the gold(ii) isomers. The very strong preference of 4a\u20134c over 4a\u2032\u20134c\u2032 independent of the meso substituents might be due to a solvent effect overwhelming the substituent effects. Indeed, in THF or in MeOH solvent-separated ion-pairs +//[PF6]\u2013[4a\u20134c] should be present while in CH2Cl2 solution contact ion pairs of 6][2a][PF or 6][3a][1a][PF in CH2Cl2 . This is in good accordance with a nitroarene radical anion.1a\u2032\u2032. The radical distribution 1a\u2009:\u20091a\u2032\u2009:\u20091a\u2032\u2032 is estimated as 78\u2009:\u20093\u2009:\u200919. The decomposition into the component spectra is displayed in the ESI.nBu4N]Cl to the solution prior to reduction of the gold(iii) porphyrin with CoCp2. No significant changes are observed for Au(TPP), 3a (CH2Cl2) or 4c (THF) in the presence of chloride. However, the presence of chloride transforms the 1a\u2009:\u20091a\u2032\u2009:\u20091a\u2032\u2032 radical mixture almost completely into a 1a\u2009:\u20091a\u2032 mixture (65\u2009:\u200935) as only the gold(ii) resonance and the porphyrin radical anion resonance are observed under these conditions radical (1a), the porphyrin based \u03c0 radical (1a\u2032) and a further nitro group based \u03c0 radical (1a\u2032\u2032). Assuming, that rapid freezing does not strongly affect the equilibria of valence isomers, we can conclude that the environment, namely anions and the solvent, appears to influence these valence isomeric equilibria significantly. The substituents influence the equilibria as well, especially, when a strongly electron accepting nitro group is present. A conceivable intervalence transition between 1a and 1a\u2032/1a\u2032\u2032 is not detected in the UV/Vis spectrum by comparison with the spectra of 2a and 3a radicals 1a\u20134c, the valence isomeric equilibrium 1a/1a\u2032\u2032 and the effect of counterions will be addressed by theoretical methods in the next section.The electronic structure of the gold(iii) porphyrins +[Au(TPP)], +\u2013[4c]+[1a] and the structures of all corresponding neutral species Au(TPP), 1a\u20133a and 4a\u20134c were optimised by DFT methods complexes and their neutral congeners are found in the Au\u2013N distances which increase by ca. 4% from 2.051 to 2.124 \u00c5 in all cases (B2u) distortion is noted in the neutral complexes bond distances which is not observed. The calculated Mulliken spin densities are in full accordance with these structural parameters. In all neutral complexes the majority of the spin density is located at the metal centre (Mulliken spin density at Au: 0.44), especially in the 5dx2\u2013y2 orbital . Compared with the isoelectronic Cu(TPP) the spin densities are more delocalised onto the nitrogen atoms which is in agreement with the EPR results as well optimised structure of 1a\u2032\u2032 as shown in 1a\u2032\u2032 are fully consistent with a gold(iii) oxidation state (+[1a] and 1a the C6H4NO2 torsion angle with respect to the porphyrin plane C5\u2013C12\u2013C38\u2013C43 is significantly reduced from 66.1\u00b0 and 62.4\u00b0 to 50.8\u00b0 suggesting a conjugative electron withdrawing effect of the gold(iii) porphyrin as expected for a \u03c0-centred radical. The spin density is mainly located at the NO2 substituent and partially delocalised over the \u03c0-system of the porphyrin. The Mulliken spin density at the gold atom in 1a\u2032\u2032 is essentially zero but only hydrogen-bonded to two CH groups of the aryl substituents fully agree with a gold(iii) porphyrin but not with a gold(ii) porphyrin . The N\u2013O distances have increased from 1.284 \u00c5 in 6][1a\u00b7\u00b7\u00b7PF\u2013 to 1.315 \u00c5 in 6]\u2013[1a\u2032\u2032\u00b7\u00b7\u00b7PF as expected for population of N\u2013O antibonding orbitals. The spin density is largely confined to the NO2 substituent and partially delocalized to the \u03c0-system of the porphyrin. The C5\u2013C12\u2013C38\u2013C43 torsion angle of the nitrophenyl substituent decreases from 61.4\u00b0 (6]\u2013[1a\u00b7\u00b7\u00b7PF) to 50.2\u00b0 (6]\u2013\u2013[1a\u00b7\u00b7\u00b7PF and 6]\u2013[PF6] as the supporting electrolyte in THF (MeOH). Potentials are given relative to the ferrocene/ferrocenium couple. Spectroelectrochemical experiments were performed using a thin layer quartz glass (path length 1 mm) cell kit equipped with a Pt gauze working electrode, a Pt counter electrode and a Ag/AgNO3 reference electrode . X-band CW EPR spectra were measured on a Miniscope MS 300 . g-Values are referenced to external Mn2+ in ZnS . Simulations were performed with the program package EasySpin.Porphyrins H2Cl2) was employed. No (symmetry) constraints were imposed on the molecules, except for the NO distance constraint for 1a\u2032. The presence of energy minima of the ground states was checked by analytical frequency calculations.Density functional calculations were carried out with the Gaussian09/DFT seriesiii) porphyrin complex (c = 5 \u00d7 10\u20133 M) in CH2Cl2 (6][Au(TPP)][1a][2a][3a][4a][PF) or THF was treated with 0.95 equivalents of cobaltocene CoCp2. The X-band EPR spectrum of the sample was measured immediately after freezing the solution to 77 K. The effect of chloride was measured by addition of 2.0 equivalents of [nBu4N]Cl prior to the reduction.Under an inert atmosphere a solution of the respective gold(iii) and sodium acetate were dissolved in glacial acetic acid (20 mL). The reaction mixture was heated to reflux for 20 h, allowed to cool to room temperature, and diluted with dichloromethane (100 mL). The mixture was washed with water (2 \u00d7 50 mL), saturated sodium carbonate solution (2 \u00d7 50 mL) and water (1 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (50 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (10 mL) for 72 h. The mixture was diluted with dichloromethane (100 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate, and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][Au(TPP)]+. HR-MS (ESI): m/z 809.1993 . CV : E\u00bd/V \u20132.350, \u20131.650, \u20130.975.5,10,15,20-Tetraphenylporphyrin , potassium tetrachloridoaurate, potassium tetrachloridoaurate(iii) and sodium acetate were dissolved in glacial acetic acid (40 mL). The reaction mixture was heated to reflux for 22 h, allowed to cool to room temperature, and diluted with dichloromethane (200 mL). The mixture was washed with water (2 \u00d7 100 mL), saturated aqueous sodium carbonate solution (2 \u00d7 100 mL) and water (1 \u00d7 100 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (100 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (20 mL) for 72 h. The mixture was diluted with dichloromethane (100 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate, and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][1a]+. HR-MS (ESI): m/z 912.1905 . CV : E\u00bd/V \u20132.300, \u20131.795, \u20131.560, \u20130.920.10,20-Di(phenyl)-15-(4-(methoxycarbonylphenyl))-5-(4-nitrophenyl)porphyrin iii) hexafluorophosphate 6][1a] to yield 6][2a]+. HR-MS (ESI): m/z 882.2163 . CV : E\u00bd/V \u20132.500 (irrev.), \u20132.280, \u20131.645, \u20130.990.gold(N-Acetylaminophenyl))-10,20-di(phenyl)-15-(4-(methoxycarbonylphenyl))porphyrin IIIa , potassium tetrachloridoaurate(iii) and sodium acetate were dissolved in glacial acetic acid (20 mL). The reaction mixture was heated to reflux for 24 h, allowed to cool to room temperature, and diluted with dichloromethane (100 mL). The mixture was washed with water (2 \u00d7 50 mL), saturated aqueous sodium carbonate solution (2 \u00d7 50 mL) and water (1 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (50 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (10 mL) for 72 h. The mixture was diluted with dichloromethane (50 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate, and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][3a]+. HR-MS (ESI): m/z 924.2229 . CV : E\u00bd/V \u20132.490 (irrev.), \u20132.300, \u20131.630, \u20130.990.5-(4-(N-Acetylaminophenyl))-10,20-di(phenyl)-15-(4-(carboxyphenyl))porphyrin IVa , potassium tetrachloridoaurate(iii) and sodium acetate were dissolved in glacial acetic acid (20 mL). The reaction mixture was heated to reflux for 24 h, allowed to cool to room temperature and diluted with dichloromethane (100 mL). The mixture was washed with water (2 \u00d7 50 mL), saturated aqueous sodium carbonate solution (2 \u00d7 50 mL) and water (1 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (50 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (10 mL) for 72 h. The mixture was diluted with dichloromethane (50 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate, and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][4a]+. HR-MS (ESI): m/z 910.2115 . CV : E\u00bd/V \u20131.030.5-(4-(N-Acetylaminophenyl))-10,20-di((4-butoxy)phenyl)-15-(4-(carboxyphenyl))porphyrin IVb , potassium tetrachloridoaurate(iii) and sodium acetate were dissolved in glacial acetic acid (40 mL). The reaction mixture was heated to reflux for 24 h, allowed to cool to room temperature, and diluted with dichloromethane (200 mL). The mixture was washed with water (2 \u00d7 100 mL), saturated aqueous sodium carbonate solution (2 \u00d7 100 mL) and water (1 \u00d7 100 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (100 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (20 mL) for 72 h. The mixture was diluted with dichloromethane (100 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][4b]+. HR-MS (ESI): m/z 1054.3218 . CV : E\u00bd/V \u20132.450, \u20131.745, \u20131.070.5-(4-(N-Acetylaminophenyl))-10,20-bis(4-(trifluoromethylphenyl))-15-(4-(carboxyphenyl))porphyrin IVc , potassium tetrachlorido aurate(iii) , and sodium acetate were dissolved in glacial acetic acid (20 mL). The reaction mixture was heated to reflux for 24 h, allowed to cool to room temperature and diluted with dichloromethane (100 mL). The mixture was washed with water (2 \u00d7 50 mL), saturated aqueous sodium carbonate solution (2 \u00d7 50 mL) and water (1 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was evaporated to dryness and the residue dissolved in dichloromethane (50 mL). The organic phase was stirred with a saturated aqueous solution of potassium hexafluorophosphate (10 mL) for 72 h. The mixture was diluted with dichloromethane (50 mL) and washed with water (2 \u00d7 50 mL), dried over anhydrous magnesium sulfate and filtered. The filtrate was removed under reduced pressure and the residue purified by chromatography over silica to yield 6][4c]+. HR-MS (ESI): m/z 1046.1863 . CV : E\u00bd/V \u20132.300, \u20131.590, \u20130.990.5-(4-(meso-tetraaryl substituted AB2C porphyrins with KAuCl4 in the presence of HOAc/NaOAc cleanly gives the corresponding gold(iii) porphyrinato complex cations. Amino-substituted porphyrins are N-acetylated under these conditions and have to be prepared from the corresponding nitro-substituted gold(iii) porphyrins by reduction with SnCl2/HCl. The gold(iii) complexes can be reduced at least three times. The potentials slightly depend on the electron withdrawing and donating nature of the substituents. The first reduction is addressed by UV/Vis spectroelectrochemistry and by EPR spectroscopy. Upon one-electron reduction, the Soret band experiences a small bathochromic shift. The intensity of the Soret band of the electron rich complexes +[2a] (R2 = NH2) and +[4b] (R3 = OnBu) slightly increases upon reduction while all other neutral complexes feature less intense Soret bands as compared to their parent AuIII complexes. These spectral data clearly suggest the presence of an unreduced porphyrinato ligand in all cases under these conditions. Chemical one-electron reduction of the porphyrinato gold(iii) hexafluorophosphate salts by cobaltocene yields the corresponding AuII porphyrin complexes with a characteristic EPR pattern displaying hyperfine coupling to 197Au and 14N. The degree of 197Au hfc and g anisotropy places the gold contribution to the spin density in (tetraphenylporphyrinato)gold(ii) complexes in between that of [Au(en)2]2+ porphyrins bearing carboxylic acid, amine and amide substituents, as introduced in this report, with light-harvesting porphyrins and electron donating porphyrins via amide connectivityAuration of (en)2]2+ and the Supplementary informationClick here for additional data file."}
+{"text": "Synthesis of strained five-membered cyclic sulfamides has been achieved for the first time by intramolecular 1,5-C(sp3)\u2013H amination via Co(ii)-based metalloradical catalysis. ii)-based metalloradical catalysis (MRC) proves effective for intramolecular 1,5-C\u2013H amination of sulfamoyl azides under neutral and nonoxidative conditions, providing a straightforward approach to access strained 5-membered cyclic sulfamides with nitrogen gas as the only byproduct. The metalloradical amination system is applicable to different types of C(sp3)\u2013H bonds and has a high degree of functional group tolerance. Additional features of the Co(ii)-catalyzed 1,5-C\u2013H amination include excellent chemoselectivity toward allylic and propargylic C\u2013H bonds. The unique reactivity and selectivity profile of the Co(ii)-catalyzed 1,5-C\u2013H amination is attributed to the underlying radical mechanism of MRC.Co( If successful, the catalytic C\u2013H amination process \u2013H amination to prepare N-heterocycles of variable ring size and functionality.via metal-catalyzed intramolecular C\u2013H amination.3)\u2013H amination for the formation of 5-membered cyclic sulfamides is a challenging process, which is presumably attributable to the potentially strained [3.1.0]-bicyclic transition state associated with the asynchronous concerted mechanism that is shared by most catalytic C\u2013H amination systems via metallonitrene intermediates.A) followed by low-barrier radical substitution,ii)-based metalloradical system exhibits excellent chemoselectivity and high functional group tolerance.A number of different metal-based catalytic systems have been developed for regioselective intramolecular C\u2013H amination via MRC \u2013H bond, affording the strained 5-membered cyclic sulfamide 2a in 51% yield. Further optimization experiments indicated that [Co(P1)], which is supported by the D2h-symmetric amidoporphyrin 3,5-DitBu-IbuPhyrin (P1), was a superior metalloradical catalyst for the radical C\u2013H amination reaction, leading to the formation of the desired 2a in 90% yield (P1)] over [Co(TPP)] is ascribed to the stabilization of the key \u03b1-Co(iii)-aminyl radical intermediate by the amide functionalities through hydrogen-bonding interaction (A).At the outset of this project, the sulfamoyl azide via MRC . Initial0% yield . The enheraction , A.5a,b,P1)]-based metalloradical system was shown to be effective for intramolecular 1,5-C(sp3)\u2013H radical amination of a wide range of sulfamoyl azide substrates (ii)-based catalytic system could efficiently aminate \u03b1-C(sp3)\u2013H bonds of heteroaromatic rings such as furan (entry 5) and thiophene (entry 6), without complication from potential reactions with the heteroatoms. As exemplified by the high-yielding formation of trans-cyclic sulfamide 2c, excellent diastereoselectivity could be achieved (entry 3). The metalloradical amination by [Co(P1)] could also be applied for non-benzylic C\u2013H substrates, as demonstrated with the successful formation of the cyclic sulfamide 2g and bicyclic sulfamide 2h in respectable yields (entries 7 and 8), along with the corresponding 6-membered structure product formation.3)\u2013H substrates, such as \u03b1-C\u2013H bonds of esters and amides, could be aminated smoothly, producing \u03b1,\u03b2-diamino acid derivatives (entries 9 and 10).3)\u2013H bonds as well (entries 7 and 11). It is notable that the \u03b1,\u03b2-diamino acid derivative 2k bearing a quaternary \u03b1-carbon center could be synthesized in near quantitative yield (entry 11). Different N-substituents in the azide substrates were effectively tolerated in the C\u2013H amination process. For example, sulfamoyl azides containing both electron-donating and electron-withdrawing N-substituents, such as N-benzyl (entry 1), N-methyl (entry 2), N-Boc groups (entry 11), and N-4-methoxybenzyl (entry 15), groups proved to be suitable substrates.Under the optimized conditions, the [Co]-catalyzed 1,5-C\u2013H radical amination system exhibited excellent chemoselectivity towards allylic C\u2013H bonds without affecting the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC \u03c0 bonds.2l and 2m without observation of the corresponding aziridination products (entries 12 and 13). Furthermore, this amination process was shown to be stereospecific regarding the stereochemistry of the alkene units as exemplified by the catalytic reactions of both trans- and cis-alkene-derived sulfamoyl azide substrates (entries 14\u201316). Under the standard conditions, the expected allylic C\u2013H amination products 2n, 2o and 2p were formed in high yields with excellent stereospecificity as well as chemoselectivity. The fact that no olefin isomerization was observed during these catalytic amination reactions suggests the 5-exo-tet radical cyclization of the corresponding \u03b5-Co(iii)-allylic radical (B to 2) proceeds with a low barrier and even faster than the facile trans- and cis-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC \u03c0 bond isomerization.ii)-based MRC is among the few catalytic systems that are effective for amination of propargylic C\u2013H bonds without affecting the electron-rich C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC \u03c0 bonds.2t in 89% yield.The [Co]-catalyzed 1,5-C\u2013H amination made it possible for late-stage functionalization of complex molecules in a predicable fashion. For example, when stigmasterol-based azide 1u, which was directly prepared from the corresponding amine by a one-step procedure scale\" fill=\"currentColor\" stroke=\"none\">C bonds was chemoselectively achieved, providing the fused multicyclic sulfamide 2u in 70% yield ], the propargylic C\u2013H bond was selectively aminated to afford the deoxyuridine-derived 5-membered cyclic sulfamide 2v in 95% yield ).The demonstrated chemoselectivity and functional group tolerance of is an effective catalyst with the capability of activating a broad scope of sulfamoyl azides for intramolecular 1,5-amination of different types of C(sp3)\u2013H bonds with high stereospecificity, providing straightforward access to the potentially bioactive 5-membered cyclic sulfamide compounds in high yields. The Co(ii)-based catalytic system can be simply operated under neutral and non-oxidative conditions without the need for any additives, generating nitrogen gas as the only byproduct. Furthermore, this 1,5-C(sp3)\u2013H amination process features excellent chemoselectivity and functional group tolerance, allowing for late-stage functionalization of complex molecules. The success in addressing this challenging amination process by Co(ii)-MRC is believed to be directly related to the underlying radical mechanism involving the key \u03b1-Co(iii)-aminyl radical intermediate.In summary, by applying the concept of metalloradical catalysis (MRC), a new approach has been successfully demonstrated for addressing the challenges of intramolecular 1,5-C(spSupplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We report an unusual reaction design in which a chiral bis-cyclometalated rhodium(iii) complex enables the stereocontrolled chemistry of photo-generated carbon-centered radicals and at the same time catalyzes an enantioselective sulfonyl radical addition to an alkene. iii) complex enables the stereocontrolled chemistry of photo-generated carbon-centered radicals and at the same time catalyzes an enantioselective sulfonyl radical addition to an alkene. Specifically, employing inexpensive and readily available Hantzsch esters as the photoredox mediator, Rh-coordinated prochiral radicals generated by a selective photoinduced single electron reduction are trapped by allyl sulfones in a highly stereocontrolled fashion, providing radical allylation products with up to 97% ee. The hereby formed fragmented sulfonyl radicals are utilized via an enantioselective radical addition to form chiral sulfones, which minimizes waste generation.We report an unusual reaction design in which a chiral bis-cyclometalated rhodium( In this respect, some elegant protocols have been disclosed in enantioselective transformations of photo-generated allylic carbon radicals. In 2013, MacMillan and co-workers introduced a radical\u2013radical recombination process by the combination of a chiral amine and photoredox catalyst in which only one example with moderate enantioselectivity was reported showing the challenge of stereocontrol over such radical intermediates 15 as a photoredox mediator for the generation of radical species under mild conditions generates the key Rh-coordinated radical intermediate B, which is trapped by an electron-deficient allyl sulfone 2 delivering the secondary radical intermediate C. The subsequent fragmentation11 of C provides the sulfonyl radical E and enolate intermediate D, the latter of which yields the C\u2013C bond formation product 3 upon protonation. Meanwhile, the sulfonyl radical E undergoes a stereocontrolled radical addition16 to A in a reversible fashion11 and a subsequent HAT followed by ligand exchange provides the C\u2013S bond formation product 4.Our design is based on our recently introduced bis-cyclometalated chiral rhodium-based Lewis acids (LAs)nditions . Initial1 to ensure a highly chemoselective reduction. Secondly, the radical trapping and subsequent fragmentation process should be fast enough to compete with the protonation of intermediate B which would generate undesirable free \u03b2-carbonyl carbon radicals. The reaction of such free radicals with 2 would compromise the enantioselectivity of product 3. Therefore, this design with the utilization of the leaving sulfonyl radicals, which otherwise would lead to by-products, is very attractive not only from the perspective of green and sustainable chemistry17 but also for suppressing side reactions of the sulfonyl radical and shifting the equilibrium of a potentially reversible radical fragmentation.11Two key challenges are needed to be solved to achieve a high asymmetric induction. Firstly, a robust and effective chiral Lewis acid catalyst is required to control the stereochemistry of two mechanistically distinct processes as well as reduce the reduction potential of substrate N-acylpyrazole 1a with allyl sulfone 2a under visible light irradiation employing a stoichiometric amount of the Hantzsch ester HE-1 as the photoredox mediator and reductant.15 Although our well-established iridium catalyst \u0394-IrS18 could not give any detectable product . Interestingly, the related \u0394-RhO provided 3a in much higher ee indicating that the mechanism differs from our previous reports about Giese-type radical reactions in which RhS, which features a higher steric congestion, works better than RhO. Notably, our recently developed chiral rhodium complexes show a unique reactivity for this reaction. Other Lewis acids such as Sc(OTf)3 gave very low efficiency while LiBF4 could not even catalyze the process (entries 4 and 5) and no conversion was observed without catalyst (entry 6). Other substituted HE species also worked very well (entries 7 and 8), whereas DIPEA, which is widely used as a sacrificial reductant in photoredox catalysis, could not accomplish the transformation (entry 9). These results highlight the multiple functions of the HE in our system acting as a photoredox mediator as well as an electron donor and proton source. Furthermore, on illumination with blue LEDs, which do not emit any UV light along with the recycled C\u2013S formation products 4a\u2013h in good yields and ee (up to 89% ee) (entries 1\u20138). Intriguingly, a lower yield and slightly lower ee were observed for the radical functionalization product 3b when allyl sulfone bearing a less electron deficient ester group was employed (compare entries 9 with 1). It is noteworthy that functional groups including a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond, a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond and an imide are well tolerated under these mild conditions (entries 11\u201313). As a limitation, substrates with a long chain at the \u03b2-position (1b\u2013d) produced the radical allylation products 3f\u2013h with decreased ee (eqn (1)) and \u03b2-aryl \u03b1,\u03b2-unsaturated N-acylpyrazole could not afford any expected product. Furthermore, the alkenyl sulfone 5 was proven to be competent, providing the radical alkenylation product 6 in 54% yield with 93% ee (eqn (2)).With the optimized conditions at hand, we next investigated the substrate scope with respect to radical acceptors . A wide 1a + 2a \u2192 3a + 4a in the presence of a series of common chemical functionalities as additives containing azido, cyano, and carbonyl groups that are vulnerable to reductive conditions can be recovered in high yields under the standard conditions (entries 1\u20134). Importantly, several heterocycles which might competitively coordinate to the catalyst did not erode the enantiomeric excess of products (entries 3\u20139). Several natural products, including coumarin, caffeine, and (\u2013)-citronellol, were found to have little influence on the reaction outcomes (entries 7\u201310). Furthermore, N-acylpyrazoles known as a useful and reactive synthetic building block can be easily converted into other compounds, such as alcohols or amides (eqn (3) and (4)). Overall, these results highlight the potential of this protocol for further applications in the synthesis of complex molecules.To further evaluate the functional group tolerance and robustness of this catalytic system, we conducted the reaction nalities and ESI\u2020HE as a visible light harvesting antenna being consistent with recent reports and RhO-1a (\u20131.62 V vs. Fc/Fc+), thus making highly selective SET between RhO-1a and the excited state of HE-1 (E+/HE*)(HE\u02d9 = \u20132.23 V vs. Fc/Fc+) feasible or 2,2,6,6-tetramethyl-piperidinooxy (TEMPO) as radical scavengers. When the reaction was monitored by electron paramagnetic resonance (EPR) using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a free radical spin-trapping agent, mixed signals containing two radical species were observed, one of which was identified as a phenyl sulfonyl radical (Fig. S8 in ESI22 Finally, a quantum yield of 0.09 was determined for the reaction 1a + 2a \u2192 3a + 4a, which is consistent with the proposed mechanism being devoid of any chain process (see ESI for detailsA number of experiments support the proposed mechanism . Firstly23In conclusion, we here have introduced an unusual reaction scheme in which a chiral rhodium complex enables the catalytic enantioselective functionalization of a photo-generated carbon radical employing cheap and readily available Hantzsch esters as a photoredox mediator and reductant. Intriguingly, in this radical allylation reaction using allyl sulfones as reagents, the generated sulfonyl radical by-product can be trapped by electron deficient alkenes and transformed into valuable enantioenriched S-containing building blocks thereby minimizing waste generation. The simple reaction setup and the mild reaction conditions as well as the demonstrated compatibility with a wide range of functionalities render this robust catalytic system an appealing process. Further investigations on the stereocontrolled chemistry of prochiral radicals are ongoing in our laboratory.There are no conflicts to declare."}
+{"text": "Moderate variations in the fuel structure cause large changes in the rate of the back and forth motions experienced by a chemically fuelled catenane-based switch. para-substituents in the order Cl > H > CH3 > OCH3 (\u03c1 = +5.2). Thus, the time required to complete a full cycle was almost two days for the OCH3 derivative and dropped to a few minutes for the Cl derivative. These results show for the first time that the rate of operation of a molecular switch can be regulated by variations in the fuel structure.This work deals with the use of 2-cyano-2-arylpropanoic acids as chemical fuels for an acid\u2013base operated molecular switch that consists of a Sauvage-type catenand composed of two identical macrocycles incorporating a phenanthroline unit. When used as a base promoter of the decarboxylation of propanoic acid derivatives, the switch undergoes large amplitude motion from the neutral catenand to a protonated catenate and back again to the neutral state. The rate of back proton transfer, which determines the rate of the overall process, was markedly affected by While B\u2032 and B\u2032\u2032 are well-defined states with the two phenanthroline subunits tightly held together by interactions with the shared proton, state A is not co-conformationally well-defined. The fuel, 2-cyano-2-phenylpropanoic acid undergoes base-promoted quantitative decarboxylation via a carbanion intermediate, which is rapidly formed (step B\u2032 \u2192 B\u2032\u2032) and slowly transformed (step B\u2032\u2032 \u2192 A) to the \u201cwaste\u201d product 2-phenylpropanonitrile by back proton transfer.It is only lately that molecular machines operated by the irreversible reaction of a single chemical fuel have been reported by uspara positions of 2-cyano-2-(p-chlorophenyl)propanoic acid , 2-cyano-2-(p-methylphenyl)propanoic acid and 2-cyano-2-(p-methoxyphenyl)propanoic acid on the rate of the fuelled switching of catenand 1.Since the stability and reactivity of carbanions are strongly structure dependent,2 were prepared according to the same procedure adopted for the preparation of the parent acid 2 (X = H) (6Compounds (X = H) .62\u2013 bond, the Et3N promoted decarboxylation of the acid derivatives was monitored by 1H NMR spectroscopy in CD2Cl2 at 25 \u00b0C for comparison with the corresponding reaction of the parent acid 2 (X = H). For the latter it has been established2 (X = H) to Et3N generates a hydrogen bonded ion pairinter alia, with the finding that the time required to complete the decarboxylation of 2 (X = H) dropped from about 3 h to 10 min when Et3N was replaced by the proton sponge 1,8-bis(dimethylamino)naphthalene the concentration of free ions is most likely negligibly small.\u00b6Because of the low polarity of dichloromethane becomes the slow step in the decarboxylation of the parent acid 2 (X = H).61H NMR spectra of a 1\u2009:\u20091 mixture of 1 and 2 (X = H) . The exceptional slowness of the proton removal from the tetrahedral cavity defined by the four N atoms1H+ is such a weakly interacting anion as CF3CO2\u2013, the equivalence of the two phenanthroline units in the 1H NMR spectrum in dichloromethane at 25 \u00b0C were monitored by 1H NMR spectroscopy , the spectra showed that in all cases the sole reaction product was the corresponding decarboxylated compound 3, besides the catenane in its original neutral state. Furthermore, the 1H NMR spectra recorded in the course of the reactions confirmed the presence of transient species, characterized by patterns of signals very similar to each other, as well as to those displayed by the reaction of the parent acid (B\u2032\u2032 in 2 (X = H) led us t Quite remarkably, the time required to achieve quantitative transformation to 3 amounts to almost two days for the OCH3 derivative and decreases in the order OCH3 > CH3 > H > Cl, becoming as short as a few minutes for the Cl derivative.The reactions of ent acid . Clearlyd B\u2032\u2032 in are invo2 (X = OCH3) . The trace at t = 2.5 min shows that 1 is no longer in its original, neutral state, but the signals of the ion pair B\u2032\u2032 are still barely perceptible. This means that the major component of the reaction mixture is the salt denoted by B\u2032 in 1H+ and its carboxylate counterion. The concentration of this transient species is still significant at t = 14.5 min and becomes negligibly small in the next spectrum at 34.5 min.The spectra related to the early stages of the sluggish reaction of CH3) see , particu 5.5 ppm , gave in\u03bbmax = 375 nm) belonging to transient species. The latter were identified with intermediates B\u2032\u2032 or, more precisely, with their carbanion components, since the absorbance of 0.30 mM 1H+ is 0.30 at 350 nm, drops to 0.05 at 375 nm and becomes negligibly small at 380 nm and beyond. Indeed, the spectra related to the reaction of 2 (X = OCH3) (B\u2032\u2032 as monitored by 1H NMR spectroscopy (2 (X = CH3 and H) the maximum is reached in about 3 and 1.5 min, respectively, which means that the build-up of B\u2032\u2032 was complete, or very nearly so, when the first 1H NMR spectrum in Fig. S7 and S6,Corroborating evidence came from investigation of the time-dependent UV-vis spectra of the reaction mixtures, which was prompted by the observation that the solutions became yellow in the course of the reactions, but were colourless at the end. The four sets of time-dependent UV-vis spectra are char = OCH3) show thatroscopy . In the 2 (X = OCH3 and CH3), the absorbance growth and subsequent decay were treated as two separate first-order reactions with rate constants k\u2032 and k\u2032\u2032, respectively. k\u2032 and k\u2032\u2032.For the reactions of 1 and 2 (X = OCH3) was varied over the range 0.30\u20131.50 mM , A set of four kinetic runs in which the initial concentration of 0 mM ESI, page S184NBr on the rate of reaction of 0.30 mM 2 (X = H) with equimolar 1 was investigated. UV-vis monitoring of the reactions showed in all cases a rapid growth followed by a slower decay of the absorption band centered at 375 nm, the shape and maximum intensity of which were hardly affected by the added salt, even at the highest salt concentration of 5.0 mM increased with increasing salt concentration and showed a marked tendency to saturate. B\u2032\u2032 (Kass = 1600 M\u20131), which is significantly more reactive than uncomplexed B\u2032\u2032 .1H+Br\u2013 and Bu4N+R\u2013. It should be stressed that this mechanism, which is almost kinetically indistinguishable from that in \u2021An alternative mechanism involves fast and reversible double exchange between ion pair partners, followed by a rate limiting second-order reaction between .In a last set of rate measurements the effect of added Bu Fig. S10. Again, B\u2032\u2032, namely 1H+ and the carbanion derived from 2 (X = H), are brought into an orientation more adapted to proton transfer when B\u2032\u2032 becomes a component of an ion quartet as a result of association with Bu4NBr. However, due to the lack of structural information on the ion quartet, a detailed interpretation of the rate enhancing effect exerted by the added salt does not appear to be accessible.It seems likely that the components of the ion pair 1H NMR and UV-vis spectroscopy strongly supports the operation of the reaction mechanism outlined in B\u2032 and B\u2032\u2032 as reaction intermediates.To sum up, the combination of data from 1H NMR spectroscopy. Firstly, the transient absorption band at 375 nm provided direct evidence of the existence and kinetic behavior of the carbanion intermediates, whose signals in the 1H NMR spectra were hardly visible. Secondly, the kinetics based on UV-vis spectroscopy gave qualitative information about the substituent effects on the rate of step B\u2032 \u2192 B\u2032\u2032. The reactivity order Cl > H > CH3 > OCH3 is the same as that observed in the reactions promoted by Et3N, but the rupture of the R\u2013CO2\u2013 bond is much faster in the reactions promoted by 1 because any stabilization of R\u2013CO2\u2013 by hydrogen bonding is hardly conceivable when 1H+ is the countercation.Data from UV-vis spectroscopy gave pieces of information which could not be obtained from B\u2032\u2032 \u2192 A), whereas only a qualitative reactivity order could be obtained from the 1H NMR spectra. The Hammett plot of log (k\u2032\u2032x/k\u2032\u2032H) vs. \u03c3p reported in \u03c1 = 5.2 (r = 0.98). Such a large \u03c1 value is indicative of a much larger fraction of negative charge on the benzyl carbon atom in the transition state, which is equivalent to saying that the kinetic basicity of the anionic component in B\u2032\u2032 is enhanced by EWGs and depressed by EDGs. Unusual as it might seem, such a behavior is not unprecedented.et al.2 (12 substituents). They found that the rates of protonation of ArCMe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNO2\u2013 were enhanced by EWGs and retarded by EDGs (\u03c1 > 0) and concluded that there is a very little delocalization of the fractional negative charge to the oxygen atoms in the transition state, whereas the negative charge is mostly localized on the oxygen atoms of the nitronate anions.Finally, kinetic treatment of the UV-vis data provided a quantitative estimate of the effect of the substituents on the rate of the back proton transfer with Bu4NOH.2 benzylic carbon atom, as well as significant delocalization to the nitrogen atom of the cyano group. In our case, a high negative charge density on the nitrogen atom of the CN group would guarantee a strong electrostatic stabilization of B\u2032\u2032, whose shape is supposed to be one in which the group PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013 points to the proton embedded in the two-phenanthroline core.Although a cyano group is less effective than a nitro group in stabilizing a negative charge on an adjacent carbon atom, we suggest that a similar interpretation applies to the protonation of our cyano-stabilized carbanions. Accordingly, it seems likely that the canonical structure I , unlike 1H NMR spectra were recorded on a 300 MHz spectrometer. The spectra were internally referenced to the residual proton signal of the solvent at 5.30 ppm. Spectrophotometric measurements were carried out on a diode array spectrophotometer equipped with a thermostated cell compartment. Mass spectrometric measurements were carried out using an ESI-TOF spectrometer.2Cl2 and CD2Cl2 were flushed through basic alumina immediately prior to use. The same batch of solvent was used in each of the sets of kinetic measurements. Et3N was distilled from metallic sodium before use. Catenane 1 was available from a previous investigation.2 (X = H) was available from a previous investigation2 were prepared from the corresponding ethyl esters14All reagents and solvents were purchased at the highest commercial quality and were used without further purification unless otherwise stated. CH1H NMR \u03b4: 7.55\u20137.52 , 7.46\u20137.43 , 3.52 , 1.99 .This compound had a m.p. of 81\u201382 \u00b0C, lit. 81\u201382 \u00b0C.151H NMR \u03b4: 7.46\u20137.43 , 7.24\u20137.22 , 4.05 , 2.36 , 1.97 . 13C NMR \u03b4: 171.2, 139.1, 131.8, 129.8, 125.7, 119.0, 47.7, 24.2, 20.9. UV-vis (CH2Cl2): \u03bbmax (\u03b5) = 230 nm (3200 cm\u20131 M\u20131), 262 nm (400 cm\u20131 M\u20131), 285 nm (200 cm\u20131 M\u20131). ESI-MS (negative-ion-mode): 144 (M \u2013 H+ \u2013 CO2).This new compound had a m.p. of 86\u201388 \u00b0C (dec.). 1H NMR \u03b4: 7.51\u20137.46 , 6.99\u20136.93 , 4.95 , 3.82 , 1.97 . 13C NMR \u03b4: 171.3, 160.0, 127.1, 126.7, 119.2, 114.3, 55.3, 47.1, 23.8. UV-vis (MeOH): \u03bbmax (\u03b5) = 230 nm (13\u2009900 cm\u20131 M\u20131), 274 nm (1600 cm\u20131 M\u20131), 281 nm (1300 cm\u20131 M\u20131). ESI-MS (negative-ion-mode): 160 (M \u2013 H+ \u2013 CO2).This new compound had a m.p. of 87\u201389 \u00b0C (dec.). para-substituent of the 2-cyano-2-arylpropanoic acid used as a fuel. The time taken to complete a full cycle decreased in the order OCH3 > CH3 > H > Cl. It was as long as two days for the OCH3 derivative, and dropped to a few minutes for the Cl derivative. Fine tuning of the motion rate could be further achieved by the addition of Bu4NBr. A detailed kinetic investigation has shown the intermediacy of ion pairs B\u2032 and B\u2032\u2032, which differ in the nature of the anionic component. The negative charge of the anion in B\u2032\u2032 was suggested to be mostly localized on the nitrogen atom of the CN group, and strongly shifted to the benzyl carbon atom in the transition state of the rate-determining proton transfer step.In this work we have described the first example of a chemically operated molecular switch in which the rate of the back and forth motion could be regulated within wide limits by variations in the fuel structure, namely by variations in the nature of the There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "To date, enantiomerically enriched molecules containing gem-diaryl containing tertiary or quaternary stereogenic centers have been readily accessed by transition metal-catalyzed enantioselective or stereoconvergent aryl transfer reactions. gem-diaryl containing tertiary or quaternary stereogenic centers are present in many natural products and important pharmacophores. While numerous catalytic asymmetric methods enable access to 1,1-diaryl motifs, transition metal-catalyzed asymmetric arylations (TMCAAr) are one of the most powerful methods to prepare enantiopure gem-diarylalkane compounds. The main methodology includes enantioselective 1,2- or 1,4-additions across C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds by arylmetallic reagents; aryl cross-couplings of olefins, benzylic (pseudo)halides and aziridines; asymmetric aryl substitution reactions of allylic substrates; and isotopic benzylic C\u2013H arylation.Chiral Thus, the development of effective methods to access enantiomerically enriched diaryl structural motifs will play a significant role in both academic and industrial settings. Enantiomerically pure drugs or their precursors are usually produced by the chiral kinetic resolution technique. However, access to 1,1-diarylalkanes with a high level of optical purity using this technique is challenging because little differentiates the two aryl groups installed on the stereogenic center electronically and sterically. This issue can be solved by asymmetric synthetic methods through either stereospecific or enantioselective transformations. In the last few decades, an array of catalytic enantioselective approaches towards the construction of nonracemic gem-diaryl compounds have been developed, including asymmetric Friedel\u2013Crafts reactions, asymmetric aryl transfer reactions (arylations), asymmetric hydrogenation of 1,1-diarylalkenes, asymmetric C\u2013H functionalization of enantiotropic diarylalkanes and so on. Among them, transition metal-catalyzed asymmetric arylations (TMCAArs), which install an aryl group onto the benzylic position of substrates in an enantioselective or stereoconvergent manner, represent the most powerful method. In this field, development of new reactions, chiral ligand families and metal complexes has enabled the precise construction of various chiral diaryl motifs, including dibenzyl alkanes and alkenes, 1,1-diarylmethanols, 1,1-diarylmethylamines and so on. To the best of our knowledge, TMCAAr for the synthesis of gem-diaryl compounds includes nucleophilic 1,2- or 1,4-additions of arylmetallic reagents across C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds; aryl cross-couplings to olefins, benzylic (pseudo)halides and aziridines; asymmetric aryl substitution reactions of allylic substrates; isotopic benzylic C\u2013H arylation and so on scale\" fill=\"currentColor\" stroke=\"none\">C, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds represent a highly efficient method to construct tertiary or quaternary stereogenic centers, concomitant with the formation of Csp3\u2013Csp2 bonds. These transformations are frequently used to prepare important chiral gem-diaryl containing compounds from activated styrene and aryl-substituted carbonyl substrates. Gem-diaryl stereogenic centers are generated in the key step of aryl migratory insertion across the unsaturated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC(O or N) bonds, followed by the hydrolysis or \u03b2-H elimination of the metal-binding intermediate -catalyzed highly enantioselective 1,4-addition of arylboronic acids to \u03b2-aryl substituted unsaturated carbonyl derivatives using a carvone-derived chiral diene ligand (L1)tert-butyl 3,3-diarylpropanoates were afforded with 89\u201393% ee. Miyaura found that both Rh(i)ii)S,S)-chiraphos ligand are competent catalysts for TMCAAr of \u03b2-aryl-\u03b1,\u03b2-unsaturated ketones and esters (R)-Segphos catalyst to provide enantiomerically pure 4-arylchroman-2-ones. The product, (R)-6-methyl-4-phenylchroman-2-one, was readily converted in two steps into (R)-tolterodine, an important urological drugi) complex of sulfoxide\u2013phosphine was an appropriate catalyst to afford chiral 1,3,3-triarylpropan-1-ones with up to 98% ee.7In 2005, Carreira successfully realized Rh . NonraceN,N-dimethylsulfamoyl imino esters with a new bicyclic bridgehead phosphoramidite ligand (L3). Chiral (Z)-\u03b3,\u03b3-diaryl-\u03b1,\u03b2-dehydroamino esters were afforded with excellent yields and enantioselectivities (75\u201396% ee) .N-heterocyclic carbene ligand (L4) (i) mediated the catalytic cycle that consists of transmetalation/insertion/ligand exchange. Zhou and coworkersL5) efficiently promoted the enantioselective 1,4-addition of chalcones with arylboroxines and a direct 1,4-insertion mechanism was proposed and supported by DFT calculations and natural-abundance 13C KIE experiments , top. Theriments , bottom.2.2L6 could give 69% conversion but a low ee value (\u20137%), while the more sterically hindered L7 gave 28% ee but a low conversion (4%) (L6 and L7 in a 1\u2009:\u20091 ratio could improve the conversion (92%) as well as the enantioselectivity (31%). In 2013, IulianoL8) significantly improved the enantioselectivities (94\u201399%) as well as the yields (82\u201398%) of the desired products , top. Inproducts , bottom.L9). In 2013, Wu and coworkersL10) in the arylation of nitroalkenes with high enantioselectivities (89\u201397%) , right. L11L12 ligand L11L12 , middle.L14) as a chiral ligand, enantioenriched 2,2-diaryl nitroalkanes can be produced in high yields and good enantioselectivities in air induces the protonation of the alkylrhodium intermediate faster than the \u03b2-H elimination process, thus selectively forming the addition product instead of the substitution product. Later on, Xu employed the chiral phosphine\u2013olefin ligand (L16) in the same asymmetric reaction to achieve generally high yields and ee valuesIn contrast to the extensive studies on conjugate arylations of nitroalkene substrates, successful conjugate additions of sulfonyl olefins have rarely been reported.2.3syn-diastereoselective arylfluorination of chromenes with arylboronic acids and selectfluor.S)-4-tert-butyl-2-(2-pyridyl)oxazoline (L17) as the chiral ligand, a wide spectrum of enantioenriched 2-fluoro-4-phenylchromanes were produced with up to 96% ee, albeit in moderate yields -catalyzed electrophilic arylation of allylic amidesIn contrast to nucleophilic arylation, Gaunt recently reported a novel copper/bisoxazoline isoborneol (L19)iPr)4 also promoted the enantioselective addition of Ph3Al, ArTi(OiPr)3 and ArMgBr to ketones, producing chiral diaryl alkyl carbinols.31For ketone arylations, Fu reported the first enantioselective 1,2-addition of PhL20) as the chiral ligand, albeit with only 39% ee (L21) was demonstrated to promote the addition of arylborons to cyclic or acyclic arylketones with up to 68% eeL22 complex, which produced a range of chiral diaryl alkyl carbinols with excellent ee (95\u201399%) , right. i)-spirophosphite (L23) catalystN-(sulfinyl)cinnamylamine ligand (L24) in the arylation of \u03b1-ketoesters and \u03b1-diketones.2(p-cymene)]2 and -Me-BIPAM (L25) could also promote the asymmetric addition of arylboronic acids to \u03b1-ketoesters with high enantioselectivities.33For the 1,2-arylation of activated ketones, Xie and Zhou developed the first highly enantioselective addition of arylboronic acids to \u03b1-ketoesters using a chiral Rh/phosphoramidite (L26) catalysed 1,2-addition of arylboronic acids to 2,2,2-trifluoroacetophenones was highly effective in the Rh-catalyzed arylation of trifluoroacetophenones ,ii),i)ii)R)-MeO-mop as a chiral ligand. A variety of optically active 3-hydroxy-3-aryl-2-oxindoles were afforded in good to excellent yields (49\u201398%) with high enantioselectivities (72\u201391%) (i)-catalyzed arylation of NH isatin but obtained a poor enantioselectivity (55%). Liao and co-workersL28 is also compatible with the NH isatin arylation process and gives an improved efficiency , left. Mficiency , right.N-tosyl ketimines with sodium tetraarylborates by employing a chiral diene ligand (L29) . The met3 group are attractive to organic and medicinal chemists. In 2013, Xu and coworkers developed a rhodium-catalyzed asymmetric addition of arylboronic acids to CF3- or alkoxycarbonyl-substituted cyclic ketimines.L30) which they developed themselves to provide such molecules in high yields with excellent enantioselectivities and phosphine-oxazoline (L31) ligands, respectively (ii)/L33 complex and enables the synthesis of enantioenriched 3-amino-3-aryl-2-oxindoles with high ee. Zhang also demonstrated the first Ni(ii)-catalyzed asymmetric addition of arylboronic acids to cyclic imines using a tropos phosphine-oxazoline biphenyl ligand.41Pd-catalyzed enantioselective additions of arylboronic acids to cyclic ectively . Analogo3i)/L34 complexes, which afforded the \u03b3 product with a high enantioselectivity but moderate \u03b3-regioselectivity as the promoter. The formal SN2-substituted products, gem-diarylpropenes, were obtained with excellent ee reactions of cinnamyl electrophiles are one of the most important strategies to access chiral 1,1-diarylpropene molecules. Although the transfer of aryl groups to \u03b3-aryl substituted substrates resulted mainly in the achiral \u03b1 product with palladium catalysis, the \u03b3-regioselectivity is facile for iridium and copper catalysis. In 2007, Alexakisectivity , top. Rellent ee , bottom.i)-catalyzed AAAr,N-heterocyclic carbenes displayed remarkably high \u03b3-regioselectivity as well as excellent enantioselectivity reagents can couple with cinnamyl bromides or carbonates to construct tertiary and quaternary gem-diarylmethine stereogenic centres.In the field of Cu/L39 catalyst. The method was applied to a gram-scale synthesis of (S)-sertraline tetralone from the available racemic 4-hydroxy-4-phenylbutanoate. Other efforts to attempt the enantioconvergent arylation of racemic benzylic chloride or trifluoroborate, also by Ni(ii)/bis(oxazoline) catalysis, revealed the moderate stereoselectivity. In 2017, ReismanL40) as the chiral ligand as the reductant was the best ligand for the asymmetric transformation.The catalytic asymmetric \u03b1-arylation of styrenyl aziridines is one of the most important methods to access nonracemic 2,2-diarylethylamine derivatives. However, successful cross-coupling reactions rely on the stereospecific transformation of enantiomerically enriched aziridines. Recently, Sigman and Doyle developed an elegant Ni-catalyzed stereoconvergent reductive cross-coupling of racemic eductant , bottom.4.2gem-diarylalkanes, wherein the precoordination of the metal catalyst with prochiral substrates in a bidentate or monodentate manner is usually demanded. In 2015, DuanL41) into the Pd(ii)-catalyzed direct \u03b2-arylation of aminoquinoline derived aliphatic amides with aryl iodides. An array of \u03b2,\u03b2-diaryl carboxylic acid derivatives were produced in moderate to good enantiomeric ratios catalysts. In the end, both high yields and enantioselectivities were obtained using a substoichiometric amount of chiral phosphoric acid (L42) under solvent-free conditions \u2013H arylation of benzaldehydes via the precoordination of Pd(ii) with the in situ generated imine intermediatel-tert-leucine, 10 mol% Pd(OAc)2 and 3 equiv. H2O, o-alkyl benzaldehydes reacted with a wide range of aryl iodides to produce 1,1-diaryl alkanes in moderate yields with high enantiomeric ratios.In 2016, Yu employed chiral \u03b1-amino acids as transient directing groups in the enantioselective benzylic C(spL43) ligands in the Pd(ii)-catalyzed monodentate auxiliary directed C(sp3)\u2013H arylation of aliphatic amides.Soon afterwards, the same group employed chiral acetyl-protected aminoethyl quinoline -segphos as a chiral ligand. Enantioenriched 3-aryl-3-fluorooxindoles including a chiral quaternary center were obtained in high yields with excellent enantioselectivities trifluoroacetate and a chiral spiro phosphoric acid (SPA) (2(TFA)4 catalyst is responsible for the generation of the zwitterion (I). The 1,2-proton shift occurs via a proton shuttle model, which is mediated and stereochemically controlled by the chiral SPA (L44).In 2015, Zhu and Zhouid (SPA) . Chiral 5gem-diaryl moieties. The conceptual strategy of this method involves the enantioselective formation from the styrene and stereospecific coupling of metal bound benzyl intermediates. These species are either nucleophilic or electrophilic depending on the nature of the initiator (M1-R\u2032) .Inspired by the efficiency of direct aryl-benzyl coupling, transition metal-catalyzed three-component cross-coupling reactions of olefins have been developed as an important and complementary method in the construction of (M1-R\u2032) . In this5.12 atmosphereL45) could give the best enantioselective induction (up to 64%).In 2010, the Sigman group initially studied the palladium-catalyzed asymmetric hydroarylation of styrenes with arylboron esters in the presence of an i-PrOH solvent and in an Ovia double aryl cross-coupling to acrylates.L46 and Pd2(dba)3, optically active 3,3-diaryl esters with a high enantioselectivity were produced (ii)\u2013H complex intermediate.In 2016, Sigman and Toste developed an elegant enantioselective 1,1-diarylation method produced . The pro2SiH proceeded smoothly to produce enantioenriched 1,1-diarylethanes in good yields with good to excellent enantioselectivities.Recently the Buchwald group developed an alternative strategy to realize highly enantioselective hydroarylation of styrenes through CuH/Pd(0) cooperative catalysis5.2L47) was compatible with a variety of 1,2-bisubstituted alkyenylarene substrates with excellent diastereo- and enantioselectivities. The syn/trans selectivity of the arylboration addition of 1,2-dihydronaphthalene was facilely switched by changing the achiral ligands on the Pd(ii)-complex to promote the Cu/Pd-catalyzed enantioselective arylboration of terminal vinylarenes with aryl iodides under mild conditions /L49 catalyst, the enantioselective trifluoromethyl and aminoarylation of styrenes proceeded smoothly and afforded gem-diarylethane derivatives in moderate to high yields and with good ees to provide nonracemic gem-diarylalkane compounds. Due to distinguishing features including the wide range of substrate scope, good functional group tolerance and the use of easily accessible substrates, the related methodologies have received increasing interest from synthetic and pharmaceutical chemists, aiding the latter in synthesising medicinal molecules in a highly efficient manner.In this review, a large number of TMCAAr reactions, which target the construction of chiral gem-diaryl molecules has recently been highlighted and will be the focus of continuous research. The present methods, including hydro- or borylarylation, direct benzyl C\u2013H bond arylation and so on, need improvement of the efficiency and broadening of the substrate scope, and their use in the construction of quaternary carbon stereogenic centres remains challenging.Predictably, the development of strategies that transform commercially available feedstocks to highly valuable There are no conflicts to declare."}
+{"text": "The general capability of graphene quantum dots to serve as capping ligands exchanging native organic stabilizers for various types of semiconductor nanoparticles affords the opportunity to engineer functional nanocomposites with remarkable thermoelectric properties. Graphene quantum dots (GQDs) are shown to serve as phase transfer agents to transfer various types of nanoparticles (NPs) from non-polar to polar solvents. Thorough characterization of the NPs proves complete native ligand exchange. Pellets of this GQD\u2013NP composite show that the GQDs limit the crystal size during spark plasma sintering, yielding enhanced thermoelectric performance compared with NPs exchanged with inorganic ions. A photoluminescence study of the GQD\u2013NP composite also suggests energy transfer from GQDs to NPs. Herein, we present the use of graphene quantum dots (GQDs) as ligands to stabilize nanoparticles.Recent advances in nanocomposite materials allow for a scalable methodology to generate multifunctional materials with properties stemming from both their individual components and, more interestingly, their synergistic interactions.GQDs can be viewed as a derivative of the extensively studied two-dimensional material graphene.Recent incorporation of GQDs into nanocomposite materials also offers the opportunity to take advantage of their unique charge carrier extraction capability for better solar cell efficiency.Inorganic NPs were made following well-developed wet-chemistry methods.vs. Cd) with GQDs. The TEM images before and after phase transfer indicate that the NPs\u2019 shape and size are preserved scale\" fill=\"currentColor\" stroke=\"none\">O and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, respectively, indicating the presence of GQDs after ligand exchange. Furthermore, 1H nuclear magnetic resonance (NMR) spectroscopy clearly proves the exclusive removal of alkyl H atoms in the range of 0.8\u20132.5 ppm and alkene H atoms at 5.3 ppm (The Fourier transform infrared spectroscopy (FTIR) spectrum of the NP dispersion after phase transfer shows a greatly reduced peak for the C\u2013H stretching mode at \u223c2900 cm\u20131 and S3\u2020, 5.3 ppm and S4\u2020; 5.3 ppm in whichX-ray diffraction (XRD) patterns for PbTe NPs before and after GQD ligand exchange are shown in Fig. S5a.in situ. \u03b6-potential in the insets of via increasing their energy of solvation. The proposed scenario is presented in in situ details of their status in the GQD\u2013NP complexes, which still remains a major challenge for almost all types of ligands on NP surfaces.It would be interesting to learn how the GQDs assemble near the surface of the NPs to form a stable dispersion in a polar solvent. We therefore performed a dynamic light scattering (DLS) study to reveal this behaviour \u03c41 = 1.34 ns and \u03c42 = 6.77 ns to \u03c41 = 0.98 ns and \u03c42 = 6.56 ns, respectively (To further prove the binding of GQDs to NPs, we studied the PL of GQD-capped CdSe NPs dispersed in solution .43,44 Cdectively , which sectively for CdSeComposites made from NPs are promising materials for thermoelectric applications, because of their inherent low thermal conductivity and enhanced Seebeck coefficients that result from quantum confinement and energy filtering effects.The thermoelectric measurements highlight the advantages of using GQDs over SCNs as capping agents for both electrical conductivity and Seebeck coefficient . The fin2 NPsThe prepared GQD\u2013NP composite may also be applied when the collective properties of different components are desired. We have demonstrated the effect of GQDs in lessening the sintering of PbTe NPs for enhanced thermoelectric performance. Another application is likely to be photovoltaic materials. There are reports of mixing GQDs with TiOIn conclusion, for the first time, we reported the general capability of GQDs to serve as capping ligands exchanging native organic stabilizers for various types of semiconductor NPs. The FTIR, NMR, TEM and XRD characterization results proved that the ligand exchange is complete and that the integrity of the NPs is preserved. Thermoelectric measurement of GQD\u2013PbTe composites revealed that the GQDs play a crucial role in limiting crystal size leading to an enhanced Seebeck coefficient, and thus a considerable ZT value of 0.46, without tuning the composition or doping level of the NPs. The PL lifetime of the GQD\u2013NPs indicated efficient energy transfer between the GQD ligands and the NP cores. Given the many and yet tunable properties of GQDs, we anticipate that versatile properties could be engineered from this novel type of GQD\u2013NP composite and to benefit various applications, including photovoltaic and thermoelectric devices, and catalysis.Supplementary informationClick here for additional data file."}
+{"text": "Enantioselective 3-exo iodo-cycloetherification of allyl alcohols was realized by employing a novel ion-pair organocatalyst. exo iodo-cycloetherification of allyl alcohols was achieved using NIS as a halogen source. Based on this reaction, one-pot asymmetric 3-exo iodo-cycloetherification/Wagner\u2013Meerwein rearrangement of allyl alcohols en route to enantioenriched 2-iodomethyl-2-aryl cycloalkanones was subsequently developed. Due to the participation of adjacent iodine, the Wagner\u2013Meerwein rearrangement of 2-iodomethyl-2-aryl epoxide proceeds with unusual retention of stereoconfiguration.By designing a novel chiral ion-pair organocatalyst composed of chiral phosphate and DABCO-derived quaternary ammonium, highly enantioselective 3- In this regard, although 3-exo halo-cycloetherification of allyl alcohols has long been known,exo halocyclization, which impedes the development of an asymmetric version of this reaction.Halogenative functionalization of olefins is one of the most important transformations in organic synthesis, as it not only provides a versatile handle for further derivatization, but also delivers highly diastereoselective ring closure when the nucleophile and alkene are tethered together.via combinational approaches, which greatly accelerates the catalyst screening process. Inspired by Toste's recent workWith the advent and booming of organocatalysis,exo iodo-cycloetherification of allyl alcohols using commercially available NIS as a halogen source. Additionally, this protocol provides direct access to enantiopure 2-iodomethyl epoxides,15Herein, we would like to report the success of implementation of the ion-paring strategy, leading to the discovery of a novel ion-pair organocatalyst. This unprecedented organocatalyst enables the first enantioselective 3-exo-iodocyclization of allyl alcohol 1a was explored using an ion-pair organocatalyst generated in situ by combining silver phosphate with DABCO-derived quaternary ammonium salt for convenience of catalyst screening . Further structural modification of ammonium salt A3 revealed that A8 was the optimal cation fragment for the ion-pair organocatalyst, furnishing epoxide 2a with 92% ee (entries 3\u20139). As for the anion fragment, 8H-R-TRIP-OAg provided a better result than any other chiral silver phosphate evaluated were also surveyed under identical reaction conditions but gave no desired cyclization product, with the starting material being fully recovered . As a slight excess of A8 was used in the in situ procedure, we reasoned that A8 might be an effective promoter for this reaction. Indeed, comparable enantioselectivity was obtained by adding a catalytic amount of A8 to the reaction. It is postulated that A8 might act as a Lewis base to stabilize the iodonium intermediate PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPPh3 and electron-donating groups (2ag-2ah and 2ca\u20132ch) on the phenyl moiety were tolerated, affording the corresponding epoxides with good to excellent enantioselectivities (87% to 99% ee). Gem-substituents were crucial for the reaction, as 2f lacking gem-substituents was obtained in only 41% yield and 63% ee. Epoxides with cyclic gem-substituents were obtained with higher enantioselectivities (2c-2ch and ESI2a and 2b). A 2-alkyl substituted allyl alcohol was also smoothly converted to epoxide 2g, albeit with low enantioselectivity (37% ee). Furthermore, gram syntheses of epoxides 2a and 2c\u20132e were also smoothly realized by using 5 mol% C1 without affecting enantioselectivities, and the catalyst loading could even be reduced to 1 mol% affording comparable results . Surprisingly, the absolute configuration of 3c was established to be S by X-ray crystallographic analysis of hydrazone 4 derived from 3c,TS2, which then rearranged to ketone 3c with double inversion of configuration. Furthermore, derivatizations of 3c were also performed to demonstrate its synthetic utility. Substitution of the iodide with NaN3 provided azide ketone 5 smoothly, and the iodide could also be converted to an alcohol via formyloxylation/hydrolysis6 in satisfactory yield. It is noteworthy that no erosion of enantiopurity was detected in all these reactions.Next, Wagner\u2013Meerwein rearrangementn center . BF3\u00b7Et2r see ESI, deliverexo iodo-cycloetherification/Wagner\u2013Meerwein rearrangement was also developed . Different substituents on the phenyl group were found to be compatible with the one-pot process, affording the corresponding cyclohexanones 3c\u20133f in satisfactory enantiopurities. Furthermore, seven-membered cycloketone 3g could also be obtained via this one-pot cascade reaction with 91% ee (comparable with that of the corresponding epoxide 2d), providing a complementary route to previous protocols involving enantioselective halonium-induced semi-Pinacol rearrangement for the enantioselective construction of halogenated cycloheptanones.To simplify the operation, one-pot asymmetric 3-eveloped . Fortunaexo iodo-cycloetherification of allyl alcohols using NIS as a halogenating reagent. By employing this novel catalyst, a variety of enantiopure 2-iodomethyl-2-aryl epoxides were successively prepared with good to excellent enantioselectivities, even on a gram scale. Subsequently, one-pot asymmetric 3-exo iodo-cycloetherification/Wagner\u2013Meerwein rearrangement of 2-aryl-2-propen-3-ol was explored, which provided direct access to chiral 2-iodomethyl-2-aryl cycloalkanones with good enantioselectivities. Unusual retention of configuration owing to the assistance of the adjacent iodide was also observed in the Wagner\u2013Meerwein rearrangement.In conclusion, a novel ion-pair organocatalyst comprised of chiral phosphate and DABCO-derived quaternary ammonium was designed, which enabled the first asymmetric 3-Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Covalent organic frameworks with high porosity and crystallinity have been synthesized, through macrocycle-to-framework strategy, using shape-persistent arylene-ethynylene macrocycles as the key components to control the topology and modulate the porosity. Macrocycle-to-framework strategy was explored to prepare covalent organic frameworks (COFs) using shape-persistent macrocycles as multitopic building blocks. We demonstrate well-ordered mesoporous 2D COFs (AEM\u2013COF-1 and AEM\u2013COF-2) can be constructed from tritopic arylene-ethynylene macrocycles, which determine the topology and modulate the porosity of the materials. According to PXRD analysis and computer modelling study, these COFs adopt the fully eclipsed AA stacking mode with large accessible pore sizes of 34 or 39 \u00c5, which are in good agreement with the values calculated by NLDFT modelling of gas adsorption isotherms. The pore size of COFs can be effectively expanded by using larger size of the macrocycles. Provided a plethora of polygonal shape-persistent macrocycles with various size, shape and internal cavity, macrocycle-to-framework strategy opens up a promising approach to expand the structural diversity of COFs and build hierarchical pore structures within the framework. Mesoporous 2D COFs with high surface area, large pore volume, good thermal stability and high crystallinity were successfully prepared from arylene-ethynylene macrocycles. By varying the size of macrocycles, the pore size of the COFs can be systematically tuned.Covalent organic frameworks (COFs) represent a novel class of porous crystalline polymers, in which the building blocks are assembled into two- or three-dimensional architectures through covalent bonds. COFs possess rigid structures, high thermal stabilities, and low densities. Since the pioneering work of Yaghi and co-workers,vC),1 and AEM-2, which closely resemble the commonly used trigonal connector, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), were prepared (1 and AEM-2 have similar triangle shape as HHTP (7 \u00c5) but with increased sizes, having the extended lateral lengths of approximately 9 \u00c5 and 13 \u00c5 respectively. Gram-scale AEM-1 and AEM-2 were obtained from simple dipropynyl monomer 1, or 2 through acyclic diyne metathesis macrocyclization (ADIMAC), followed by deprotection of TBS groups in high yields. Highly active multidentate triphenolsilane-based Mo(vi) carbyne complexAmong various SPMs, arylene-ethynylene macrocycles (AEM) are of our particular interest, since they are perfectly planar and rigid and their size and geometry can be easily tailored.prepared . AEM-1 a1 and AEM-2 as a novel type of multitopic building units, which can modulate pore size/distribution of COFs. We fixed the length of the linker using the same simple 1,4-benzenediboronic acid (BDBA), and varied the size of multitopic connectors: HHTP (7.1 \u00c5), AEM-1 (9.3 \u00c5), and AEM-2 (13.2 \u00c5). For the comparison purpose, COF-5, which was previously reported by Yaghi,1 was obtained in mesitylene/dioxane by heating the reaction mixture at 100 \u00b0C for 7 days without stirring. Although AEM\u2013COF-2 shares a similar structure motif with AEM\u2013COF-1, it requires a different solvent combination. A low surface area material was obtained when AEM-2 and BDBA were heated (120 \u00b0C) in mesitylene/dioxane for 7 days. Among various solvent systems we tested , the combination of DMAc/DCB provided crystalline AEM\u2013COF-2 with the highest surface area under conventional heating or microwave heating . AEM\u2013COF-1 and AEM\u2013COF-2 were isolated as yellow microcrystalline powders through centrifugation followed by successive washing with anhydrous acetone. Both COFs are insoluble in common organic solvents such as alkanes, arenes, acetone, ethers, and N,N-dimethylformamide.Most COFs are generally constructed from two types of building blocks: symmetric multitopic connectors and ditopic spacers. The multitopic connectors not only determine the topologies of the COFs, but also work in tandem with the spacers to determine the pore sizes, pore volumes, surface areas and functions of the COFs. Since there are a rich diversity of ditopic spacers readily available, a common strategy to enlarge pore apertures of COFs with a given topology has been to increase the length of the rigid ditopic linkers.1 and AEM\u2013COF-2 were characterized by FT-IR, 13C-MAS NMR, elemental analysis, TGA, SEM and PXRD analysis. The FT-IR spectra of AEM\u2013COF-1 and AEM\u2013COF-2 show stretching bands of B\u2013O at 1335 cm\u20131 and 1323 cm\u20131, respectively. We also observed broad absorption band around 3430 cm\u20131, which likely corresponds to the residual hydroxyl groups of the macrocycles and boronic acids. In the magic angle spinning (MAS) solid-state 13C NMR spectrum of AEM\u2013COF-1, we observed a single peak at 92.6 ppm which can be assigned to the carbons of triple bonds, indicating the uniformity of the chemical environment around C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. The 13C NMR spectrum of AEM\u2013COF-2 shows C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond carbon peak at 90.7 ppm. Thermogravimetric analysis (TGA) of AEM\u2013COF-1 and AEM\u2013COF-2 shows <10% weight loss at 400 \u00b0C and <30% at 800 \u00b0C under a nitrogen atmosphere characterization measurement. The PXRD patterns of the COFs exhibit intense peak at 2\u03b8 = 2.9\u00b0 and 2.2\u00b0, for AEM\u2013COF-1 and AEM\u2013COF-2, respectively, along with some other peaks with lower diffraction intensities, indicating long-range molecular ordering in both COFs. We did not observe diffraction peaks that are characteristic for the starting materials a fully eclipsed model with an AA stacking (space group P6/mmm), and (ii) a staggered model with an AB stacking (space group P63/mmc). Each layer was translated from the next one by one-half of the a and b lattice parameters. A geometrical energy minimization was performed using the universal force-field implemented in the forcite module to optimize the geometry of the building molecules, as well as the unit cell parameters. The powder diffraction patterns for the models were then calculated and compared with the experimental ones. We found the simulated PXRD patterns of the fully eclipsed models of AEM\u2013COF-1 and AEM\u2013COF-2 are in excellent agreement with experimental results, indicating the eclipsed stacking mode of the layers ; and AEM\u2013COF-2: a = b = 40.935 \u00c5, c = 3.257 \u00c5 , both of which agree well with the observed reflections. Therefore, similar to COF-5, AEM\u2013COF-1 and AEM\u2013COF-2 adopt eclipsed stacking of the layers, which lead to 1D mesopores with theoretical diameters of 34 \u00c5 and 39 \u00c5 respectively.The crystallinity of AEM\u2013COF-e layers . A full 1 and AEM\u2013COF-2 were then investigated by N2 adsorption isotherms at 77 K and the results are summarized in P/P0 = 10\u20135 to 10\u20132) followed by a second stage pore filling starting around P/P0 = 0.05, which levels off at a relative pressure of P/P0 = 0.18, 0.25 and 0.35 for COP-5, AEM\u2013COF-1 and AEM\u2013COF-2, respectively. The gradual shift of the step positions suggests the increasing sizes of the pores in these three COFs. Calculations based on the non-local density functional theory (NLDFT) also reveal the trend of increasing pore sizes in the series, showing a narrow pore-size distribution (PSD) centered around 2.6 nm for COF-5, 3.2 nm for AEM\u2013COF-1, and 3.8 nm for AEM\u2013COF-2 predicted from the modelling based on XRD crystal packing. Correspondingly, we observed increasing pore volumes (Vp), which were calculated to be 0.828 cm3 g\u20131 (COF-5), 1.15 cm3 g\u20131 (AEM\u2013COF-1), and 1.38 cm3 g\u20131 (AEM\u2013COF-2) at P/P0 = 0.90. No or little hysteresis loops were observed in the whole range of adsorption\u2013desorption isotherms in all three frameworks. The absence of hysteresis loop has been observed for similar mesoporous MCM-41 with tubular hexagonal pores of sizes <40 \u00c5 at temperatures above 77.4 K.2 g\u20131 (correlation coefficient = 0.998), which is in good agreement with the reported literature value (1590 m2 g\u20131).1 and AEM\u2013COF-2 . As shown in macrocycle-to-framework strategy to construct ordered crystalline COFs with tunable pore diameters and volumes by varying the dimensions of tritopic macrocyclic building units.The porosities of the frameworks AEM\u2013COF-EM\u2013COF-2 . These v2, which contains AEM-2 with interior void of 5.8 \u00c5. However, we did not observe micropores below 1 nm range. Although the X-ray diffraction data is in excellent agreement with the perfectly eclipsed model of the AEM\u2013COF-2 layered structure, there might be slight offset between the adjacent interlayers, leading to the restricted accessibility of such micropores. In order to obtain COFs with multiple-type pore structures, the use of macrocycles with large intrinsic pores are desired.Initially, we expected hierarchical pore structures in the case of AEM\u2013COF-e.g. arylene-vinylene macrocycles (AVM),macrocycle-to-framework strategy opens up new avenues in the synthesis of COFs with intriguing architectures, properties and applications.We have demonstrated that arylene-ethynylene macrocycles (AEMs) can be utilized as well-defined building blocks for construction of COFs with high thermal stability, permanent porosity, and high crystallinity, either under conventional solvothermal conditions or microwave heating. The \u03c0\u2013\u03c0 interactions between rigid arylene-ethynylene backbones likely contribute considerably to the eclipsed packing of the layers as well as the formation of ordered crystalline materials. Our study shows that the customizable SPMs can be effectively utilized as a new type of multitopic connectors to control the topologies of the COFs and tune the surface area, pore size, and pore volume of the COFs. Given the vast availability of SPMs with different backbones and properties, Supplementary informationClick here for additional data file."}
+{"text": "A non-oxido V(v) complex with glutaroimide-dioxime (H3L), a ligand for recovering uranium from seawater, was synthesized from aqueous solution as Na[V(L)2]\u00b72H2O, and the structure determined by X-ray diffraction. v) complex with glutaroimide-dioxime (H3L), a ligand for recovering uranium from seawater, was synthesized from aqueous solution as Na[V(L)2]\u00b72H2O, and the structure determined by X-ray diffraction. It is the first non-oxido V(v) complex that has been directly synthesized in and crystallized from aqueous solution. The distorted octahedral structure contains two fully deprotonated ligands (L3\u2013) coordinating to V5+, each in a tridentate mode via the imide N (RV\u2013N = 1.96 \u00c5) and oxime O atoms (RV\u2013O = 1.87\u20131.90 \u00c5). Using 17O-labelled vanadate as the starting material, concurrent 17O/51V/1H/13C NMR, in conjunction with ESI-MS, unprecedentedly demonstrated the stepwise displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds by glutaroimide-dioxime and verified the existence of the \u201cbare\u201d V5+/glutaroimide-dioxime complex, [V(L)2]\u2013, in aqueous solution. In addition, the crystal structure of an intermediate 1\u2009:\u20091 V(v)/glutaroimide-dioxime complex, [VO2(HL)]\u2013, in which the oxido bonds of vanadate are only partially displaced, corroborates the observations by NMR and ESI-MS. Results from this work provide important insights into the strong sorption of vanadium on poly(amidoxime) sorbents in the recovery of uranium from seawater. Also, because vanadium plays important roles in biological systems, the syntheses of the oxido and non-oxido V5+ complexes and the unprecedented demonstration of the displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds help with the on-going efforts to develop new vanadium compounds that could be of importance in biological applications.A non-oxido V( Sorption of these cations on poly(amidoxime) sorbents follows the order: vanadium(v) \u226b iron(iii) > uranium(vi).\u20131, 37 nM)v) from the sorbent for reuse are much harsher than those used to elute uranium and other cations and ultimately destroy the sorbent.Although these results are promising, studies also reported significant co-sorption of iron(vi) and Fe(iii) complexes with glutaroimide-dioxime (iii) much more strongly than U(vi) as manifested by the shorter Fe\u2013O and Fe\u2013N bond lengths relative to the corresponding U\u2013O and U\u2013N bond lengths (even after taking into consideration the difference in ionic radii between Fe3+ and UO22+). The shorter bond lengths in the Fe(iii) complex were attributed to the higher charge density of Fe(iii) as well as its larger orbital participation in bonding relative to uranium. The higher thermodynamic stability and shorter bond lengths of the Fe3+/glutaroimide-dioxime complexes were postulated to be responsible for the higher sorption of Fe3+ compared to UO22+ in marine tests.Structural studies can be used to provide valuable insights into the coordination behavior of vanadium and other metal cations with amidoxime ligands and can also help explain their subsequent sorption behavior with poly(amidoxime) sorbents. For example, the crystal structures and thermodynamic stability constants have been reported for U with glutaroimide-dioxime has not been reported, reasonable speculations about its structure can be made using information obtained from the known V(v) crystal structures. Based on the reported structures of V(v) complexes with organic ligands prepared from aqueous solutions (or ionic liquid equilibrated with water), it is known that the VO2+ moiety with two short oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds scale\" fill=\"currentColor\" stroke=\"none\">OV = 1.60\u20131.63 \u00c5) usually remains intact.22+ cation which possesses a linear trans dioxido configuration that allows two tridentate ligands to bind in the equatorial plane to form a strong 1\u2009:\u20092 U(vi)/L complex,2+ cation with its bent cis dioxido configuration cannot accommodate two such ligands due to steric hindrance and insufficient coordination sites.Though the crystal structure of V is sorbed much more strongly than U(vi) by the amidoxime sorbents. One hypothesis that could explain the much stronger complexation of V(v) is that V(v) exists in the glutaroimide-dioxime complex as a non-oxido, \u201cbare\u201d V5+ ion coordinated with the ligand(s). A non-oxido V5+ cation could have a very high affinity for O and N donor ligands due to its high charge density and could easily accommodate two tridentate ligands in a mode similar to that in the Fe3+/glutaroimide-dioxime complex.4+ complexes with ligands such as 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci)N-hydroxy-iminodiacetate5+ complexes from aqueous solutions are extremely rare. One non-oxido V5+ complex, [PPh4][\u0394-V-HIDPA)2]\u00b7H2O dipropionic acid, H3HIDPA), was crystallized as the oxidized analogue of the naturally-existing Amavadiniv) complex by Ce(iv).5+ complexes directly synthesized from oxido V(v) species scale\" fill=\"currentColor\" stroke=\"none\">V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO]+ or vanadates) and crystallized from aqueous solution. In addition, the formation of non-oxido V5+ complexes in aqueous solutions via the displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds by chelating ligands complex with 4-hydroxy-dipicolinic acid , a ligand that is structurally similar to glutaroimide-dioxime, was shown to exhibit insulin mimetic behavior in vivo.v) complexes could prove useful for the design of improved insulin mimetic compounds.Although complexation of vanadium with Schiff bases such as glutaroimide-dioxime is problematic for the extraction of uranium from seawater, such complexes are currently of great interest for a variety of biological applications. For example, the V(v)/glutaroimide-dioxime complexes and characterize their crystal- and solution structures by single-crystal X-ray diffraction (XRD), multinuclear nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and electron paramagnetic resonance (EPR). This work represents the synthesis and identification of the first non-oxido V(v) complex that was directly synthesized from an oxido V(v) species and crystallized from aqueous solution. The displacement of oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds by chelating ligands that leads to the formation of a non-oxido V(v) complex in aqueous solution has been unprecedentedly demonstrated by concurrent 51V/17O NMR experiments. Results from this work provide important insights into the strong sorption of vanadium on poly(amidoxime) sorbents in the recovery of uranium from seawater.In an effort to provide structural insights into vanadium complexation with amidoxime ligands, the present work has been conducted to synthesize crystals of V(2]\u00b72H2O(cr) consists of a \u201cbare\u201d V5+ center bound to two fully deprotonated glutaroimide-dioxime ligands (L3\u2013), through one nitrogen and two oxygen atoms of each ligand, along with a sodium ion and two water molecules (P1[combining macron] (a = 7.9375(3) \u00c5, b = 8.7365(4) \u00c5, c = 12.1972(5) \u00c5, \u03b1 = 102.684(2)\u00b0, \u03b2 = 107.187(2)\u00b0, \u03b3 = 103.796(2)\u00b0. The bond lengths for the V\u2013N bonds are 1.9557(8) and 1.9551(8) \u00c5 while those for the V\u2013O bonds are 1.8667(8), 1.8741(7), 1.9039(6), and 1.9024(8) \u00c5. The extended crystal structure can be considered as successive [V(L)2]\u2013 complexes bridged by sodium atoms via N(2) and N(5) to form a one dimensional chain. The chains are then linked via bridging water molecules (O(1W)) between the sodium atoms to form a ribbon \u2013N(3)*, O(2W)\u2013O(2)*, and O(2W)\u2013N(6)*, where the superscript * denotes symmetry related positions. Tables S1 and S2 in the ESI2]\u00b72H2O.The asymmetric unit of Na[V(L)olecules . The bin macron] with unia ribbon . The rib2]\u00b72H2O(cr) are within the range of V\u2013O bond distances reported for other non-oxido V5+ compounds obtained from non-aqueous solutions (1.8\u20132.0 \u00c5), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bonds (\u223c1.6 \u00c5).The V\u2013O bond distances in Na(cr).The 1\u2009:\u20091 V complex with glutaroimide-dioxime can be synthesized and crystallized from aqueous solution. In other words, the glutaroimide-dioxime ligand can displace the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds in vanadate and form a \u201cbare\u201d V5+ complex. In addition, the crystallization of Na[VO2(HL)] suggests that an intermediate 1\u2009:\u20091 complex, in which the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds in vanadate are only partially displaced by glutaroimide-dioxime, may also exist in aqueous solution. To verify the structure of the unusual non-oxido V5+ complex and demonstrate the stepwise displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds in aqueous solutions, we hypothesized a reaction scheme ]\u2013 in the crystal structure (OH)L]\u2013 or [VO2(HL)]\u2013 does not alter the validity of the discussions below.The successful synthesis of Na\u2013 complex is the only vanadium species present. At this point, all of the V = 17O bonds of the starting vanadate would be displaced by the donor atoms of glutaroimide-dioxime and there would be no 17O atoms in the [V(L)2]\u2013 complex.17O NMR experiments have shown no oxygen exchange between the 17O-enriched water and the glutaroimide-dioxime ligand under the experimental conditions within 12 days.\u2021Prior Concurrently, the 51V NMR signal for the vanadate (with V\u2013O coupling) should disappear and a new 51V NMR signal for the [V(L)2]\u2013 complex with no V\u2013O coupling would appear.As shown in 51V/17O NMR spectra of a series of solutions with [L]/[V] ratios ranging from 0 to 3 are shown in 51V NMR spectrum of a D2O solution of Na[V(L)2]\u00b72H2O(cr) was collected to help confirm the assignment of the vanadium signal and is also shown in 51V NMR spectrum of the initial solution (a) in the absence of glutaroimide-dioxime shows the peaks for the vanadates (VO43\u2013 and HVO42\u2013) at \u03b4 = \u2013537, \u2013561 ppm. The vanadate peak has broad shoulders indicating the spin\u2013spin coupling with 17O shows a broad peak at \u223c560 ppm for the vanadate species , with an apparent linewidth of 5250 Hz due to coupling with the spin-7/2 51V nucleus. These 17O/51V spin\u2013spin coupling features agree with those reported for 17O-labelled NaVO3 in the literature.29The 51V and 17O signals for vanadates disappeared. In addition, a new 51V signal in the 51V spectra began to appear at \u03b4 = \u2013410 ppm (\u25bf) and achieved maximum intensity at [L]/[V] = 1 (51V spectrum b), diminished as [L]/[V] was increased to 2 (51V spectrum c), and nearly disappeared as [L]/[V] was further increased to 3 (51V spectrum d). Concurrently, a new peak appeared in the 17O spectra around \u03b4 = 905 ppm (\u25bf) and achieved maximum intensity at [L]/[V] = 1 (17O spectrum b), diminished at [L]/[V] = 2 (17O spectrum c), and completely disappeared at [L]/[V] = 3 (17O spectrum d).As different equivalents of glutaroimide-dioxime were added to the vanadate solution, both the \u2013, that is hypothesized in 17O signal for the intermediate 1\u2009:\u20091 V/L complex (\u25bf) suggests that, in this complex, the glutaroimide-dioxime ligand only partially displaces the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond(s) from the initial 17O-labelled vanadate, which is consistent with 2(HL)] and 2 (17O spectrum c) were noted to be slightly different. The difference probably results from different degrees of protonation in the [V(O)(OH)L]\u2013 species due to slight differences in pH between the two solutions .Based on the changes in the peak intensities with the increase of [L]/[V] and the occurrence of the maximum intensity at [L]/[V] = 1, it is reasonable to assign these peaks (\u25bf) to a 1\u2009:\u20091 intermediate complex, such as [V(O)(OH)L]h 2(HL)] . The 17O51V peak at \u03b4 = 740 ppm (\u25a1) appears at [L]/[V] = 1 (51V spectrum b), intensifies at [L]/[V] = 2 (51V spectrum c), and achieves maximum intensity at [L]/[V] > 2 (51V spectrum d). The chemical shift is identical to that of the 51V peak in spectrum e for the solution of Na[V(L)2]\u00b72H2O, implying that this peak (\u25a1) can be assigned to the 1\u2009:\u20092 V/L complex, [V(L)2]\u2013, hypothesized in 51V peak for the 1\u2009:\u20092 complex should not show 17O/51V spin\u2013spin coupling features because the ligands in the 1\u2009:\u20092 complex completely displace the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bonds of the initial 17O-labelled vanadate. However, the large linewidth of the 51V signal resulting from the low symmetry of the complex precludes the verification of the absence or presence of the coupling features for the 51V NMR signal of the 1\u2009:\u20092 (\u03b4 = 740 ppm) or 1\u2009:\u20091 complex (\u03b4 = \u2013410 ppm). Nevertheless, the absence of NMR signals on the 17O spectrum d clearly indicates that the 1\u2009:\u20092 complex does not contain oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bonds and is a \u201cbare\u201d V5+ complex.Accompanying the appearance and disappearance of the peaks (\u25bf) for the 1\u2009:\u20091 V/L complex, a new and extremely shifted 51V NMR signal for the final complex at [L]/[V] > 2 remained unchanged beyond 12 days, which suggests that vanadium remained in the V(v) oxidation state in the solution at neutral to slightly alkaline pH. If reduction of V(v) to the paramagnetic V(iv) species were to occur, it would diminish and eventually \u201cwash-out\u201d the 51V NMR signal. Further reduction to V(iii) is very unlikely: V(iii) is generally much less stable in aqueous solutions, and no signals were observed in the lower 51V chemical shift range of below \u03b4 = \u20131000 ppm.28The intensity of the 51V/17O NMR experiments in acidic solutions were not performed in this study because (1) [V(L)2]\u2013 may not be the dominant and most stable complex in acidic regions and (2) preliminary experiments suggested that redox reactions could occur between V(v) and glutaroimide-dioxime in more acidic solutions. The redox reactions between V(v) and the ligand are the subject of a future study.51V/17O NMR experiments have unprecedentedly demonstrated that the displacement of oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds in vanadates by glutaroimide-dioxime leads to the formation of a non-oxido V5+ complex in aqueous solution. The 51V chemical shift of the complex is identical to that of the solution of Na[V(L)2]\u00b72H2O(cr), suggesting that the complex in solution is probably [V(L)2]\u2013. Further verification of the stoichiometry by 1H NMR and ESI-MS is described below.To summarize, concurrent 1H and 13C NMR spectra of the V(v)/glutaroimide-dioxime solutions used in the 17O/51V experiments , as well as a solution of only glutaroimide-dioxime (a\u2032), were acquired. A 1H COSY spectrum of solution c was also acquired to confirm the peak assignments. The 1H NMR and COSY spectra are shown in 13C NMR spectra are provided in ESI /glutaroimide-dioxime solutions show two sets of signals at \u03b4 = 2.5\u20132.8 ppm and \u03b4 = 1.8\u20132.1 ppm, respectively. In each set, there are three signals that were straightforward to assign to the free glutaroimide-dioxime (\u25cb), the 1\u2009:\u20091 V/L complex (\u25bf), and the 1\u2009:\u20092 V/L complex (\u25a1), respectively, based on the NMR spectrum of the pure ligand, the COSY spectrum, the spin\u2013spin coupling patterns, and the intensity changes as a function of the [L]/[V] ratio. The signals for the 1\u2009:\u20091 complex (\u25bf) achieve maximum intensity at [L]/[V] = 1 (spectrum b) and diminish as [L]/[V] is increased to 2 and higher (spectra c and d), while the signals for the 1\u2009:\u20092 complex (\u25a1) are weak at [L]/[V] = 1 (spectrum b), intensify as [L]/[V] is increased to 2 (spectrum c), and achieve a maximum at [L]/[V] > 2 (spectrum d). These observations support the proposed structures of the 1\u2009:\u20091 and 1\u2009:\u20092 V(v)/glutaroimide-dioxime complexes, corroborate the 17O/51V NMR data, and validate the hypothesized stepwise displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds leading to the formation of the non-oxido [VL2]\u2013 complex in aqueous solution.The 1H spectra of the complexes showed that the equivalencies of the H atoms in the free ligand remain unchanged in the 1\u2009:\u20091 and 1\u2009:\u20092 complexes (1H resonances (two) with the same spin\u2013spin coupling fine structures is observed for the complex and the free ligand, which agrees with the coordination modes of the ligand in the complexes hypothesized in 5+/glutaroimide-dioxime complex. The same analysis can be made with the 13C NMR spectra with [L]/[V] = 1 and 2 are shown in m/z = 223.8 and 251.8, respectively. The peak at 223.8 corresponds to the intermediate 1\u2009:\u20091 [V(O)(OH)L]\u2013 complex hypothesized in m/z = 251.8 corresponds to a 1\u2009:\u20091 [V(O)(OCH2CH3)L]\u2013 complex . Evidently, ethoxide (OCH2CH3\u2013) from the electrospray solvent substituted the hydroxide (OH\u2013) of the [V(O)(OH)L]\u2013 complex during the dilution and/or electrospray process. The solution with [L]/[V] = 2 (lower spectrum) shows a single peak with m/z = 330.8 corresponding to [V(L)2]\u2013 , confirming the formation of the 1\u2009:\u20092 V/L complex. Simulations of the collected spectra for the regions containing the peaks at m/z = 223.8, 251.8, and 331.0 are provided in the ESI section, Fig. S2.The negative mode ESI-MS spectra for two aqueous solutions . Consequently, the initial vanadate peak corresponding to an isotopologue containing one 18O, should be observed if the vanadium complex still contains an oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bond from the vanadate and, more importantly, the (m +2) peak should be absent if all oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bonds of the vanadate are displaced by the glutaroimide-dioxime ligand.According to the manufacturer's specifications, the 10% vanadate was actum/z = 330.8 does not show the unnatural (m + 2) isotopic pattern that could indicate the presence of one 18O atom (or two 17O atoms with a much lower probability) in the 1\u2009:\u20092 complex scale\" fill=\"currentColor\" stroke=\"none\">*O bonds of the initial 17,18O-labelled vanadate are displaced by the ligands to form the non-oxido 1\u2009:\u20092 V(v)/glutaroimide-dioxime complex in solution. The presence of a small (m +1) peak at m/z = 331.8 is in accord with the natural 13C/15N abundances.Notably, the base peak at \u2013 and [V(O)(OCH2CH3)L]\u2013) show unnatural (m + 2) peaks at 225.8 and 253.8, respectively, corresponding to the presence of one 18O atom (or two 17O atoms with a much lower probability) in the complex. The presence of the (m + 2) peak indicates incomplete displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bonds of the initial 17,18O-labelled vanadate in the intermediate 1\u2009:\u20091 complex, in agreement with m + 1) peaks include the contributions from the natural 13C/15N abundances, and the additional contribution from the isotopologue containing one 17O atom.In contrast, the two base peaks for the 1\u2009:\u20091 complexes ([V(O)(OH)L]m + 2) feature that corresponds to the non-oxido complex, [V(L)2]\u2013, and a peak at 238.0 with a prominent (m + 2) feature that corresponds to a 1\u2009:\u20091 complex, [V(O)(OCH3)L]\u2013, containing one 18O. In the 1\u2009:\u20091 complex, it is the methoxide that substitutes the hydroxide of [V(O)(OH)L]\u2013 during the dilution and/or spray process.Two ESI-MS spectra obtained by using a different diluent (methanol) on a different spectrometer (Finnigan LTQ FT mass spectrometer) are shown in ESI, Fig. S3.2CH3)L]\u2013 in 3)L]\u2013 in Fig. S2,\u2013 by ethoxide and methoxide, respectively. This is consistent with the existence of the 1\u2009:\u20091 V(v)/glutaroimide-dioxime complex as [V(O)(OH)L]\u2013 in aqueous solution as hypothesized in 2(HL)]\u2013 observed in solid. The exact mechanism of substitution is unclear, but it is reasonable to assume that, energetically and kinetically, substitution of a V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond in [VO2(HL)]\u2013 is less favorable than that of a V\u2013OH bond in [V(O)(OH)L]\u2013.Interestingly, the ethoxide and methoxide adducts, [V(O)2]\u2013, in aqueous solution via the displacement of the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t*O bonds. The presence of an intermediate 1\u2009:\u20091 complex that still contains oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds, [V(O)(OH)L]\u2013, in solution has also been confirmed.To summarize, all of the ESI-MS data have validated the hypothesized reaction scheme and confg = 2.00 and no hyperfine coupling was observed, which is due to the presence of organic radicals. This signal is frequently observed due to the high sensitivity of EPR spectroscopy. The lack of hyperfine coupling and the fact that the g value is quite different from that typical for V(iv), 1.95, strongly suggest that only V(v) is present at low temperature.iv) is only a minor component at this temperature. Overall, the EPR spectra are consistent with a V(v) ground state and indicate the potential presence of a low lying charge transfer state that could be populated at high temperatures.EPR spectra of powdered crystals were recorded at 300 K and 4 K to poly(amidoxime) sorbents in marine tests was reportedly much higher than that of Fe(iii) and U(vi), following the order: V(v) \u226b Fe(iii) > U(vi). Useful structural insights into the higher sorption of V(v) can be gained by comparing the structural parameters and coordination modes of the glutaroimide-dioxime complexes with V(v), Fe(iii), and U(vi), as shown in 2]\u00b72H2O(cr) and Fe(H2L)(HL)\u00b78H2O(cr) are non-oxido metal (V5+ or Fe3+) complexes in distorted octahedral environments with similar O\u2013V\u2013N and O\u2013Fe\u2013N bond angles of approximately 73\u201375\u00b0. The average bond distances of V\u2013O and V\u2013N in Na[V(L)2]\u00b72H2O(cr) are 1.8868 \u00c5, and 1.9554 \u00c5, respectively, and are shorter than those of Fe\u2013O and Fe\u2013N in Fe(H2L)(HL)\u00b78H2O(cr) by 0.16 \u00c5 and 0.06 \u00c5, respectively. Taking into consideration the fact that the ionic radii for V(v) (0.54 \u00c5) and low spin Fe(iii) (0.55 \u00c5) are nearly identical,5+ forms a stronger complex with glutaroimide-dioxime than Fe3+ assuming a predominantly ionic bonding model. The formation of stronger V5+ complexes is most probably responsible for the higher sorption of V(v) than Fe(iii) by poly(amidoxime) sorbents.As previously mentioned, the sorption of V(2(H2L)(H2L)\u00b7H2O(cr) complex is very different from those of Na[V(L)2]\u00b72H2O(cr) and Fe(H2L)(HL)\u00b78H2O(cr). In the U(vi) complex, the UO22+ moiety maintains its linear di-oxido configuration and the two ligands coordinate to U via its equatorial plane. Evidently, glutaroimide-dioxime is not sufficiently strong to displace the oxido U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds to form a \u201cbare\u201d U6+ complex in aqueous solutions. However, it is interesting to note that the existence of a non-oxido U5+/U4+ couple was reported in the aqueous solutions of redox systems containing the unsaturated polyoxometalate anions \u03b1-[P2W18O62]6\u2013, [P2W17O61]10\u2013, and [SiW11O39]8\u2013. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds (from U5+ to UO2+) that results in the existence of a non-oxido U5+ complex in aqueous solutions containing the U5+/U4+ couple.The structure of the UO3L) in the three complexes decreases in the order: V(v) > Fe(iii) > U(vi). In Na[V(L)2]\u00b72H2O(cr), both ligands are triply deprotonated whereas in Fe(H2L)(HL)\u00b78H2O(cr), one ligand is doubly deprotonated and the other is singly deprotonated. Lastly, in UO2(H2L)(H2L)\u00b7H2O(cr), both ligands are singly deprotonated. Since each batch of crystals was obtained from solutions prepared at or near neutral pH where the ligand had the same protonation state (H3L), it is evident that V(v) competes the most effectively with protons for the ligand under these conditions. In conjunction with the parallel trend in bond lengths discussed above, this observation corroborates the suggestion that vanadium(v), in the form of the \u201cbare\u201d V5+ ion, forms the strongest complex with glutaroimide-dioxime by complete deprotonation of the ligand.The degree of deprotonation of glutaroimide-dioxime (as Hv) by the poly(amidoxime) sorbents is probably due to the formation of the very stable non-oxido V5+ complex with glutaroimide-dioxime. To improve the selectivity of the sorbent for U(vi) over V(v), an ideal ligand would be the one(s) with a binding ability that is sufficiently high for U(vi) but not high enough to displace the oxido V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond(s) in the V(v) species. Starting with the cyclic glutaroimide-dioxime platform, adding electron-withdrawing groups to the platform could reduce the basicity of the imide and oxime groups and \u201cfine-tune\u201d the binding ability of the ligand(s).In summary, the extremely strong sorption of V(v) complex from aqueous solution is a very rare occurrence. To the best of the authors' knowledge, only one other non-oxido V(v) complex has been reported. The non-oxido V(v) complex, [PPh4][\u0394-V(HIDPA)2]\u00b7H2O(cr), can be synthesized by oxidizing Amavadin, which is itself a non-oxido V(iv) complex of -2,2\u2032-(hydroxyimino)dipropionic acid (H3HIDPA), and subsequently precipitating it from an aqueous solution containing a tetraphenylphosphonium (PPh4+) salt.2\u2013 complex contains two tetradentate ligands that coordinate via a central nitrogen and three oxygen donors unlike [V(L)2]\u2013, in which tridentate bonding is observed. As 2]\u00b72H2O(cr) are significantly shorter than the analogous bonds for the V(HIDPA)2\u2013 complex by 0.075 \u00c5 and 0.055 \u00c5, respectively. The shorter bond lengths coupled with the fact that the oxime moieties of glutaro-imidedioxime are more basic (pKa \u2248 11\u201312) than the carboxylate moieties (pKa \u2248 4\u20135) in HIDPA implies that [V(L)2]\u2013 is likely a stronger complex.The isolation of a \u201cbare\u201d non-oxido V(v)- and 1\u2009:\u20092 non-oxidovanadium(v)\u2013glutaroimide-dioxime complexes could help to understand and develop vanadium(v) compounds that mimic the effects of insulin in the treatment of diabetes. It is known that vanadium plays very important roles in biological systemsv) organic complexes, such as the aforementioned K[VO2(Dpa-OH)] complex, exhibit insulin mimetic behavior.2(Dpa-OH)]\u00b7H2O(cr) and the two V(v)\u2013glutaroimide-dioxime complexes.In addition to helping improve the extraction of uranium from seawater, the structural information for both the 1\u2009:\u20091 oxidovanadium(2(HL)](cr) are shorter than the analogous bond distances in K[VO2(Dpa-OH)]\u00b7H2O(cr) by 0.10 \u00c5 and 0.06 \u00c5, respectively, implying stronger bonding in the glutaroimide-dioxime complex. Interestingly, the oxido V\u2013O bonds in VO2(HL)\u2013 are slightly longer than the oxido bonds in the Dpa-OH complex, which implies weaker V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds and may explain the ability of the second glutaroimide-dioxime ligand to subsequently displace the two oxido oxygens. In fact, the non-oxido [V(L)2]\u2013 complex formed upon addition of a second ligand to VO2(HL)\u2013 leads to an even more significant reduction of bond lengths in the Na[V(L)2]\u00b72H2O crystal. The V\u2013N and average V\u2013O bonds in [V(L)2]\u2013 are the shortest of all three complexes by 0.13 \u00c5 and 0.12 \u00c5, respectively, compared to VO2(Dpa-OH)\u2013. In this case, the higher charge density of V5+ (compared to the VO2+ moiety) coupled with the very short bond lengths indicate that [V(L)2]\u2013 is a much stronger complex than VO2(Dpa-OH)\u2013.As shown in the table, the V\u2013N bond and the average V\u2013O bond distances in Na exhibits insulin mimetic behavior in vivo, the mechanism of action could be different from that of the dissociated VO2(Dpa-OH)\u2013 complex, making Na[VO2(HL)] a worthy candidate for further investigation.Concurrent solution showed tiv) complexes, very compelling evidence was provided suggesting that only those complexes that transformed to their vanadyl (oxido) form at physiological pH exhibited insulin mimetic behavior.v) complexes partly because very few non-oxido V(v) complexes have been identified. The non-oxido and oxido V(v) complexes with glutaroimide-dioxime could provide a unique opportunity to investigate the in vivo behavior of intact oxido- and non-oxido V(v) complexes containing the same ligand, binding motif, and overall charge at physiological pH. The results of these studies could help corroborate the hypothesis of Yoshikawa et al. regarding the requirement for an oxido (or dioxido) vanadium moiety to observe insulin mimetic behavior.Lastly, in a detailed study carried out by Yoshikawa and co-workers of six different crystalline non-oxido V(v) complex with glutaroimide-dioxime (H3L), Na[V(L)2]\u00b72H2O(cr), was crystallized from aqueous solution and characterized via X-ray diffraction. The complex was found to contain two fully deprotonated L3\u2013 ligands bound to the bare V5+ cation via two oxime oxygens and the imide nitrogen. An intermediate complex, Na[VO2(HL)](cr), was also isolated and found to contain the typical VO2+ moiety present in many V(v) complexes.A rare, non-oxido V\u2013glutaroimide-dioxime complex. ESI-MS studies of V(v)\u2013glutaroimide-dioxime solutions allowed the identification the intermediate 1\u2009:\u20091 M\u2009:\u2009L complex as well as the bare [V(L)2]\u2013 complex at m/z = 330.8.Further characterizations using v) to amidoxime-based sorbents relative to U(vi) and Fe(iii) were gained by comparing the structural parameters of the V(v)\u2013glutaroimide-dioxime complex with the analogous U(vi)\u2013 and Fe(iii)\u2013glutaroimide-dioxime complexes. For these complexes, the degree of protonation of the ligand was found to decrease from U(vi) to V(v). In conjunction with the substantially shorter bond lengths observed for the V(v) complex relative to the other complexes, this implies stronger bonding in the V(v) complex and higher thermodynamic stability. In fact, the trend in binding strengths parallels the observed trend in sorption of these cations to poly(amidoxime) sorbents in marine tests.Structural insights into the much higher sorption of V(v) compounds suitable for the treatment of diabetes, the structural studies with glutaroimide-dioxime are useful for aiding the development of new, highly stable organic V(v) compounds. In fact, the high solubility of Na[V(L)2]\u00b72H2O in aqueous and ethanol solutions coupled with its stability at physiological pH could make it a potential candidate for use in diabetic treatment studies.Lastly, as there are ongoing studies to synthesize vanadium(2]\u00b72H2O(cr) were prepared at Lawrence Berkeley National Laboratory (LBNL). The glutaroimide-dioxime ligand was synthesized, and its purity was verified as described previously.3 (0.2 mmol), NaCl (12 mmol), and 0.5 mmol glutaroimide-dioxime was slowly evaporated over the course of a week to generate shiny, dark brown/black acicular crystals. The crystals are very soluble in water, fairly soluble in ethanol, and less soluble in acetonitrile and methanol. Interestingly, it was observed that prolonged heating of aqueous Na[V(L2)] solutions at \u223c50\u201360 \u00b0C resulted in the apparent decomposition of the complex as evidenced by the fading color of the solution from dark brown to a yellow-orange color. However, no further efforts were made to ascertain whether the apparent decomposition was due to either partial oxidation of glutaroimide-dioxime by V(v) or to other mechanisms.Single crystals of Na[V(L)\u03bb = 0.7749 \u00c5 were calculated using the Brennan method in XDISP2]\u00b72H2O(cr) are provided in ESI, Table S1.A single crystal was selected, removed from Paratone oil with a MiTiGen microloop, and mounted on to a Bruker goniometer equipped with a PHOTON100 CMOS detector and Oxford Systems Cryostream 800 series on beamline 11.3.1 of the Advanced Light Source at LBNL. The data were collected at 100K using the Bruker APEX2 software2(HL)] were prepared at Pacific Northwest National Laboratory (PNNL). Glutaroimide-dioxime3 was added, resulting in a dark brown solution immediately. After stirring for 5 h, the solution was filtered to remove any undissolved solids prior to removing the solvent. The residue was then re-dissolved in ethanol and filtered as before. Orange crystals were obtained from vapor diffusion of hexane into the ethanol solution. Note that the undissolved solids remaining after either filtration were not characterized.Single crystals of Na[VO2(HL)](cr) are provided in ESI, Table S3.A Bruker-AXS Kappa Apex II CCD diffractometer with 0.71073 \u00c5 Mo K\u03b1 radiation was used for data collection. Crystals were mounted on a MiTeGen MicroMounts pin using Paratone-N oil. Data were collected at 100 K. The software used for data analysis includes Br\u00fcker APEX II17O-labelled solutions for NMR experiments was performed at LBNL. NMR data were collected at University of California, Berkeley (UCB) and LBNL.Preparation of the 17O-enriched water was purchased from Cambridge Isotope Laboratories, Inc. (Lot # I1-3969). 3.67 mg (0.296 mmol) NaVO3 was dissolved in 2.0 mL 17O-enriched H2O, followed by adding 50.7 mg 40% NaOD (in D2O) solution. The colorless solution was agitated and set aside for 2\u20133 days at room temperature to allow 16O/17O exchange. The solution was checked by 17O NMR after 2 and 3 days to confirm the oxido ligand exchange.217O solutions precluded accurate pH measurements, the pH of the solutions were determined to be 7.5 (b), 8.5 (c) and 8.7 (d) by using H2O solutions of a larger volume (4.0 mL) containing the same concentrations of vanadate and glutaroimide-dioxime as the H217O solutions. These solutions were allowed to equilibrate for one day after acid additions before acquisition of NMR spectra. The final colors of solutions b, c, and d were amber, brown, and dark brown, respectively.The above-described vanadate solution was equally divided into four solutions for multinuclear NMR experiments. Different quantities of glutaroimide-dioxime were added into solutions b, c, and d to obtain an [L]/[V] ratio of 1, 2 and 3 for solutions b, c, and d, respectively. At this time, solution a (with vanadate only) remained colorless, but solutions b, c, and d (with vanadate and glutaroimide-dioxime) became pale yellow. A total of 0.12 mL 0.980 M HCl was added in two portions into each of solutions b, c, and d to adjust the pH of the solutions to around 8. Because the small volume (0.5 mL) of the H217O solutions of V(v)/glutaroimide-dioxime described above , one D2O solution of pure glutaroimide-dioxime (a\u2032) and one D2O solution of the Na[V(L)2]\u00b72H2O crystal (e) were also prepared for 1H/13C and 51V NMR experiments. Detailed information on the conditions of solutions a, b, c, d, e, and a\u2019 is provided in ESI, Table S3.In addition to the four H51V spectrum of the D2O solution of Na[V(L)2]\u00b72H2O(cr) was acquired at LBNL on a Bruker AV-300 spectrometer referenced to an external standard of VOCl3 in C6D6. All other 17O, 51V, and 13C NMR spectra were acquired at UCB on a Bruker DRX-500 spectrometer equipped with a Z-gradient broadband probe. The 1H spectra were acquired at UCB on a Bruker AV-500 spectrometer equipped with a Z-gradient triple broadband inverse detection probe using WATERGATE solvent suppression. The 1H, 13C, and 51V spectra were referenced to an external standard of VOCl3 in C6D6 and the 17O spectra were referenced to the H217O water resonance.All NMR spectra were acquired at 20\u201322 \u00b0C. The \u20131. The ESI-MS experiments with methanol spray were conducted on a Finnigan LTQ FT mass spectrometer (Thermo) at the QB3/Chemistry Mass Spectrometry Facility (UCB). Aliquots of the 1\u2009:\u20091 and 2\u2009:\u20091 [L]/[V] samples were taken and diluted in methanol. The samples were injected directly via a syringe at a flow rate of 5 \u03bcL min\u20131 with a spray voltage of 3.5 kV.Two sets of ESI-MS experiments were performed using different spray solutions on two different instruments. The ESI-MS experiments with the ethanol/water mixture were performed using an Agilent 6340 quadrupole ion trap mass spectrometer with a micro-ESI source at LBNL. Aliquots of the solutions with [L]/[V] at 1\u2009:\u20091 and 2\u2009:\u20091 were diluted in (90/10) ethanol/water and injected into the instrument and sprayed in the negative ion mode at 1 \u03bcL ming = 2.0036).EPR spectra were obtained at LBNL at room temperature and at 4 K with a Varian E-12 spectrometer equipped with liquid helium cryostat, an EIP-547 microwave frequency counter, and a Varian E-500 gaussmeter, which was calibrated using 2,2-diphenyl-1-picrylhydrazyl and participated in unlabeled 51V/1H/13C NMR and EPR experiments. B. F. Parker conducted the unlabeled and 17O-labeled 51V/17O/1H/13C NMR and ESI-MS experiments (methanol spray). S. J. Teat collected and analyzed the structure data for Na[V(L)2]\u00b72H2O(cr). Z. Zhang participated in 17O-labeled 51V/17O/1H/13C NMR and ESI-MS experiments. W. W. Lukens collected and analyzed the EPR data. P. D. Dau conducted the ESI-MS experiments with ethanol spray. J. Arnold and J. K. Gibson supervised the research of B. F. Parker and P. D. Dau, respectively. L. Rao, B. F. Parker, and Z. Zhang designed the concurrent 17O/51V/1H/13C NMR experiments. L. Rao supervised the research of C. J. Leggett and Z. Zhang, and organized the preparation of the manuscript, to which all authors contributed. S. M. Peterson and M. G. Warner designed the experiments for synthesizing Na[VO2(HL)](cr) and S. M. Peterson conducted the synthesis. A. J. P. Cardenas collected and analyzed the crystal structure data for Na[VO2(HL)](cr).C. J. Leggett synthesized the glutaroimide-dioxime ligand and Na[V(L)Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The formal cyclopentane-1,3-diyl derivatives [E1(\u03bc-NTer)2({E2C} = NDmp)] were prepared by 1,1-insertion of CNDmp into the N\u2013E2 bond of [E1(\u03bc-NTer)2E2] . 1(\u03bc-NTer)2({E2C} = NDmp)] were prepared by 1,1-insertion of CNDmp into the N\u2013E2 bond of [E1(\u03bc-NTer)2E2] . The insertion does not occur for E1 = E2 = As or E2 = Sb. Dependent on the choice of formal radical centres E, either a biradicaloid or a zwitterion was obtained. The biradicaloid features a P and an As radical center and its biradical character was established by computations as well as characteristic reactivity with respect to the formation of a housane derivative and the activation of molecules bearing multiple bonds, which was demonstrated using the example of PCtBu. In contrast, the formally N,As- and N,P-centered biradicaloids are better regarded as zwitterionic species in accord with computations and diminished reactivity, as neither housane formation nor activation of multiple bonds could be observed.The formal cyclopentane-1,3-diyl derivatives [E To date, several heteroatom-substituted derivatives of cyclopentanediyl bearing different substituents are known (selected examples: B\u2013D).Biradicals and biradicaloids are highly reactive species that can occur in the processes of bond formation and bond breaking. They were discussed as intermediates even in Diels\u2013Alder reactions by M. Dewar 2P] and [E1(\u03bc-NTer)2E2] ]2,2 ,2 phenyl),2Ge2 phenyl).2(\u03bc-NTer)2N], only diminished reactivity was observed, hence these are better regarded as zwitterionic compounds than as biradicaloids in agreement with computational studies. In the case of [Sb(\u03bc-NTer)2P], the biradicaloid was found to be a transient intermediate, whose existence could be proven by trapping experiments.34Until recently, all known cyclobutane-1,3-diyl derivatives incorporated equivalent radical centres, even though several examples investigated by the groups of Power and Yoshifuji are known featuring differing bridging moieties. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, into cyclodiphospha diazanediyl, [P(\u03bc-NTer)]2 (1PP), which afforded species E scale\" fill=\"currentColor\" stroke=\"none\">N\u2013R 2, Ter; Ter = 2,6-dimesityl-phenyl, Dmp = 2,6-dimethylphenyl), with diphosphadiazanediyl 1PP. By variation of the organic substituent, steric and electronic properties of the isonitrile could be varied. These could be adjusted to cleanly afford the cyclopentane-1,3-diyl derivative, when 2,6-dimethylphenyl-isonitrile was utilized by reaction of the available group 15 cyclobutanediyl derivatives (1E21E) with a selected isonitrile, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013Dmp .2N3H and the product 2NP could not be isolated. Upon insertion of the isonitrile, the colour of the solution changed from yellow (1NP) to red .tBu did not alter any of these characteristics, indicating that no reaction with 2NP occurred in accord with a rather small biradical character (see below).On the contrary, the ring expansion reaction of the triazenide-derived cyclobutanediyl derivatives smoothly when a s1NAs with CNDmp similarly resulted in a change of colour from initially yellow (\u03bbmax = 379 nm) to red, indicating the presence of 2NAs . Similar to 2NP, 2NAs features a \u03bd scale\" fill=\"currentColor\" stroke=\"none\">N) vibration at 1612 in the Raman and at 1610 cm\u20131 in the IR spectrum which is significantly different from the \u03bd scale\" fill=\"currentColor\" stroke=\"none\">N) vibration of pure CNDmp exhibiting a CN triple bond (2123 cm\u20131). Crystals suitable for single X-ray studies were obtained after concentration at 4 \u00b0C in good yields (83%). Red needle-shaped crystals of 2NAs decompose above 141 \u00b0C and are moisture and air sensitive. Like 2NP, 2NAs does not react with PCtBu also displaying diminished biradical character. The molecular structure of 2NAs (3CAs heterocycle. The As\u2013N bond of 1.875(3) \u00c5 is considerably longer than in the known tetrazarsole galliumtrichloride adduct Mes*N4As\u00b7GaCl3 (1.784(2), 1.805(2) \u00c5; cf. \u03a3rcov(As\u2013N) = 1.91 \u00c5) indicating single bond character.rcov(As\u2013C) = 1.97 \u00c5). The N\u2013N distances in 2NAs of 1.316(4) and 1.349(4) \u00c5 are between the sum of covalent radii for a double and a single bond , indicating delocalized double bond character, while the C49\u2013N3 bond length (1.428(5) \u00c5) corresponds to a single bond (\u03a3rcov(C\u2013N) = 1.46 \u00c5) contrary to the exocyclic C49\u2013N4 bond (1.293(5) \u00c5) which is in the typical range of a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN double bond.54The reaction of of 2NAs features1PAs in benzene with CNDmp. Within 10 minutes the insertion of CNDmp into the dark purple 1PAs (\u03bbmax = 550 nm)2PAs, which is of green colour vibration is dramatically shifted from 2123 to 1633 cm\u20131, as expected for the transition from a C\u2013N triple to double bond. Crystals of 2PAs decompose above 122 \u00b0C.In a next series of experiments we treated a solution of 13C NMR data, in which the former isonitrile carbon atom gives rise to a resonance at 184.98 ppm, which appears as doublet with a small JCP = 9.9 Hz, indicating a 2J coupling. X-ray diffraction experiments on single crystals of 2PAs revealed a secondary irradiation-induced isomerization to the housane isomer 2\u2032PAs scale\" fill=\"currentColor\" stroke=\"none\">C triple bond. The initially green solution of 2PAs in benzene quickly turned yellow upon addition of the phosphaalkyne and formation of 3PAs was observed in good yields , indicating that exclusively one isomer was formed. The strong JPP coupling of 260 Hz is characteristic for a 1JPP coupling constant. Single crystal X-ray structure elucidation unequivocally revealed the exclusive formation of one isomer . It is interesting to note that for the cyclobutanediyl derivative [As(\u03bc-NTer)2P], the regioselectivity was opposite and only the C\u2013P and P\u2013As bonded isomer was observed due to thermodynamic preference of a C\u2013P over C\u2013As bond.32The biradical character of lds 78%, , Fig. 3.2PAs/2\u2032PAs and 3PAs suitable for structure analysis were obtained from benzene solutions. The most prominent structural feature of 2PAs represents the almost planar five-membered heterocycle with rather short P\u2013N bond lengths (P1B\u2013N1 1.636(2), P1B\u2013N2 1.691(2) \u00c5) in the range of PN double bonds scale\" fill=\"currentColor\" stroke=\"none\">N) = 1.62 \u00c5), while the As\u2013N (As1B\u2013N1 1.874(2) \u00c5) and As\u2013C bonds (As1B\u2013C49 1.937(2) \u00c5, 2NAs, Single crystals of 2\u2032PAs. The transannular P\u2013As distance is shortened from 3.049(2) to 2.2920(7) \u00c5 clearly indicating the presence of a transannular P\u2013As single bond (\u03a3rcov(P\u2013As) = 2.32 \u00c5). Additionally, the P\u2013N\u2013As angle strongly decreases from 120.5(1) to 77.10(6)\u00b0. The three-membered As\u2013N\u2013P ring is almost perpendicular condensed to the four-membered As\u2013P\u2013N\u2013C ring. These experimental structural parameters are in good agreement with those of DFT computations \u00c5. The P\u2013C bridging bond length amounts to 1.673(2) \u00c5 in accord with a P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond.The phosphaalkyne addition product 1E22E five-membered heterocycles was computed for 1E22E and CASSCF computations were carried out (CASSCF = complete active space self-consistent field). Experimentally, biradicaloids 1E22E show no EPR signal and 1H, 13C, and 31P NMR signals. All 1E22E compounds have a singlet ground state in accord with rather large \u0394ES\u2013T values computations confirmed the biradicaloid nature of 1E22E. The dominant contributions to the CI wave function arise from the HOMO/LUMO exchange. The biradicaloid character can be estimated by using the formula: \u03b2 = 2c22/(c12 + c22).1 the biradical character is preserved compared to the starting material 1E21E. Therefore, as illustrated in 1 = As < P < N and E2 = Sb < As < P. For example, a biradical character \u03b2 of only 13% was computed for 2NP and 11% for 2NAs, respectively , coefficients of main contributions 0.946, \u20130.250 for 1NP and 0.956, \u20130.229 for 1NAs).2PAs features substantial biradical character of \u03b2 = 24% , c1 = 0.916 and c2 = \u20130.339), in agreement with the experimental fact that this species is capable of activating molecules containing triple bonds (vide supra) contrary to 2NP or 2NAs. Moreover, the larger zwitterionic character of 2NAs compared to 2PAs is also manifested by the HOMO of 2NAs featuring very large coefficients at As and very small ones at N, while for 2PAs the contributions are distributed almost evenly.To investigate the biradicaloid character of T values signific\u03b2 and Wiberg bond index (WBI) between the two radical centers (1\u2013E2) of all considered species 1E22E ranges from 0.262 to 0.434, which originates from partial occupation of the transannularly bonding LUMO. This reflects strong antiferromagnetic coupling between the radical centers E1 and E2. NICS values decrease when heavier elements are incorporated in the five-membered ring, indicating less stabilization by electron delocalization within the heterocycle, which is due to diminished orbital overlap between E and the adjacent N or C atoms.The computational data show a correlation between biradical character centers . The WBI1PP and the reaction of 1PP with different isonitriles, we suggest a mechanism involving the formation of a [1.1.1]bicyclic intermediate, which subsequently rearranges to give the cyclopentanediyl derivative < P (82.0) < Sb (126.8 kJ mol\u20131) for E. For the heavier homologues with E1 being P, it is exothermic and the reaction energy increases in the same order: E2 = As (\u201368.8) < P (\u201349.9) < Sb (\u201328.9 kJ mol\u20131). The second reaction step, the rearrangement from the [1.1.1]bicycle to the planar five-membered ring, is exothermic in every case. In this case, there is a tendency of the reaction becoming less exothermic as the pnictogen E2 becomes heavier .2PAs as well as 2\u2032PAs. However, upon UV irradiation, decomposition occurred, preventing the isolation of the housane species 2\u2032PAs.Finally, we want to address the issue of housane formation. Computational studies indicate, that 2\u2032PAs, which also features a localized double bond aside the P\u2013As axis of ble bond .e.g. within the homologous series 2NP, 2NAs, 2NSb), the distance between the radical centres is large and hence the orbital overlap is small, thereby reducing the stability of the heavier cyclopentane-1,3-diyl species. This is reflected in the decreasing relative stability of the singlet ground state compared to the lowest lying triplet state.In summary, the ring expansion reaction of cyclobutanediyls with isonitriles enabled the synthesis of three new group 15 derivatives of cyclopentane-1,3-diyl featuring N/P, N/As, or P/As atoms as radical centres within the five-membered heterocycle. However, there are limitations to this insertion reaction, and the preparation of cyclopentane-1,3-diyls bearing N/Sb, As/As, or P/Sb radical centres remains a challenge. Two reasons can be accountable for this: (i) in the zwitterionic border case, due to strong polarization the valence electron density distributed far from equally between the formal radical centres, so the biradical reactivity is diminished, and (ii) by incorporating heavier elements in the heterocycle (3 moiety (E1 = N) have strongly polarized N\u2013E2 bonds, a rather small biradical character and therefore are better referred to as zwitterions, which is also manifested by their inability to activate molecules bearing multiple bonds. In contrast, the P/As centered biradicaloid 2PAs exhibits a considerable biradical character, higher reactivity and can be isomerized to the short-bond species 2\u2032PAs or be utilized in small molecule activation.The new cyclopentane-1,3-diyl derivatives containing an NSupplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The syntheses and 1,2-addition reactivities of nontrigonal phosphazenes supported by trianionic tricoordinating chelates of the type L3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNdipp (3: L3 = N[CHC(tBu)O]23\u2013; 4: L3 = N(o-NMeC6H4)23\u2013; dipp = 2,6-diisopropylphenyl) are reported. 3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNdipp (3: L3 = N[CHC(tBu)O]23\u2013; 4: L3 = N(o-NMeC6H4)23\u2013; dipp = 2,6-diisopropylphenyl) are reported. These compounds are characterized by multinuclear NMR and single-crystal X-ray diffraction experiments. Distorted phosphazenes 3 and 4 are shown to add B\u2013H, B\u2013O, and Si\u2013H bonds across the formal P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN double bond, and their reactivities are contrasted with acyclic analogues. Derivatives of phosphazene 3 bearing sterically unencumbered N-substitutents readily dimerize to form the corresponding cyclodiphosphazanes; compounds with sterically demanding N-substituents are interconvertible between their monomeric and dimeric forms. The enhanced electrophilicity of the phosphorus center in nontrigonal phosphazenes 3 and 4 is rationalized by DFT calculations. Gas phase fluoride ion affinities are computed to be markedly higher for distorted phosphazenes, while proton affinities are largely unaffected by geometric distortion. These results are interpreted to suggest that distortion from pseudotetrahedral geometry results in stabilization of the P-based LUMO, while HOMO energies are essentially unchanged.The syntheses and 1,2-addition reactivities of nontrigonal phosphazenes supported by trianionic tricoordinating chelates of the type L PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit proves quite inert; indeed, the robustness of the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN moiety forms the basis for the many remarkable applications of polyphosphazene inorganic/organic hybrid materials.2Phosphazenes, \u03c3 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN double bond scale\" fill=\"currentColor\" stroke=\"none\">NR\u2032 \u2194 R3P+\u2013N\u2013R\u2032) also gives rise to numerous applications for phosphazenes as nitrogen-based electron pair donors. For instance, phosphazenes are known to be strong donor ligands for transition metals.t-Bu-P4 displays exceptionally high Br\u00f8nsted\u2013Lowry basicity and has been investigated for a variety of base-mediated transformations.4As might be expected on the basis of the differing electronegativities of phosphorus and nitrogen, however, the polarization of the formal P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit. Chief among this class of reactions are metathetical transformations stemming from formal (2 + 2) addition/elimination of unsaturated organic compounds at the phosphazene P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN moiety, of which the aza-Wittig7Apart from this nitrogen-based reactivity, phosphazenes also have been employed in a number of transformations that leverage the vicinal ambiphilic character of the P1 at phosphorus through a ligand-cooperative mechanism.In addition, we reported the synthesis of mpound 2 , top and1 and 2 might range beyond the tricoordinate state to support interesting chemical properties of their distorted \u03c34,\u03bb5-phosphazene derivatives. In this study, we report a combined theoretical and experimental treatment of phosphazenes based on supporting structures 1 and 2 which validate the hypothesis that imposition of a geometric constraint at positions ancillary to the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit enhances vicinal ditopic ambiphilicity of these phosphazenes. We also show that 1,2-reactivity of the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit leads to facile addition of \u03c3-bonded B\u2013H, B\u2013O, and Si\u2013H reagents across the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN moiety. In total, the results establish a rational framework for the design of bespoke phosphazenes with novel properties and reactivities that expand the functional role of this important class of main group compounds.Based on this precedent, we wished to ascertain the extent to which the distinctive reactivity traits of nontrigonal phosphorus compounds 2.2.1.3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNH (1\u2013P\u2013H3 (\u03b1) in the range 90\u00b0 < \u03b1 < 180\u00b0 at the M06-2X/def2-TZVP level of theory2\u2013P\u2013N\u2013H4 was relaxed to minimize energy associated with rotation about the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN formal double bond; bond lengths were held constant at values obtained from the equilibrium geometry of H3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNH ; these parameters are in good agreement with those found in previous computational studies of H3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNH.17A computational appraisal of the consequence of molecular distortion on phosphazene frontier electronic structure illustrates the theoretical framework underlying our experimental study. With the parent phosphazene Hsvg>NH , inset a1.000000,.000000 s\u03b1 = 97.9\u00b0) predictably lead to increases in overall energy (\u03b5HOMO) remains more or less constant across the scanned coordinate. Visual inspection of the relevant orbitals provides for a qualitative interpretation of this observation; highest occupied molecular orbitals are found to be mostly nitrogen-based, corresponding largely to the N lone pair (nN) with minor contributions from the ancillary phosphorus substituents.Deviations from the equilibrium geometry (\u03b5LUMO) decreases as the bond angle \u03b1 increases, ultimately resulting in stabilization of more than 3 eV as LUMO takes on increasing s-orbital character in the distortion to seesaw geometry (\u03b1 = 180\u00b0). This electronic picture suggests that the nontrigonal distortion of phosphazenes should retain the Lewis basicity of the N position but dramatically increase the Lewis acidity of the P position. We posit that the juxtaposition of donor and acceptor character at adjacent atoms should lead to an increase in 1,2-ambiphilic reactivity of the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit, in analogy to well-established chemistry of early transition metal imido scale\" fill=\"currentColor\" stroke=\"none\">NR) complexes.By contrast, the energy of the lowest unoccupied orbital , followed by removal of volatiles and trituration of the residue in pentane, produced a white solid whose 31P{1H} NMR spectrum displayed a resonance at \u03b4 7.3 ppm; the observed chemical shift is consistent with compositionally similar O,N,O-substituted phosphazenes previously reported in the literature.1H NMR spectrum, both vinylic protons (\u03b4 5.49 ppm) and tBu groups (\u03b4 0.91 ppm) on the O,N,O-support scaffold of 3 give rise to a single resonance, respectively, suggesting a time-averaged molecular geometry of Cs molecular symmetry or higher. In contrast to the planar starting material 1, the 3JP\u2013H scalar coupling constant between phosphorus and the vinylic hydrogen nuclei for 3 (3JP\u2013H = 29 Hz) is discernible and modest in magnitude. Arduengo previously noted3JP\u2013H value and the extent of molecular folding of the O,N,O-supporting ligand in related \u03c34-P compounds. On this basis, we infer that the bicyclic O,N,O ligand backbone is distorted from planarity by folding along the P\u2013N axis. We therefore assigned the structure of 3 as in The requisite phosphazenes are easily prepared by Staudinger imination4 was prepared by the reaction of 2 with 1 equiv. of 2,6-diisopropylphenyl azide and subsequent recrystallization from a solution of pentane and dichloromethane. The 31P{1H} NMR spectrum of this compound showed a resonance at \u03b4 14.5 ppm, consistent with typical values for tetraazaphosphazenes. The spectroscopic equivalence of both ligand N-methyl substituents in the 1H NMR spectrum suggest time-averaged Cs or higher symmetry, as with compound 3.Similarly, compound 7 and 8 were likewise synthesized from the corresponding phosphorus compounds 5 and 6 and N,N,N- (8)Crystalline solids of termined , Table 13 displays substantial opening of the O1\u2013P1\u2013O2 bond angle relative to the acyclic phosphazene 7; the bond angle in 3 (112.62(6)\u00b0) is 16\u00b0 wider than that of 7 (96.70(8)\u00b0). The increase in O1\u2013P1\u2013O2 bond angle in 3 is complemented by a moderate (ca. 5\u201310\u00b0) decrease in internal bond angles O1\u2013P1\u2013O2. Additionally, the N1\u2013P1\u2013N2 angle likewise increases in 3 (124.96(7)\u00b0) relative to 7 (116.46(11)\u00b0) in order to restrict unfavorable steric interactions between the N-dipp substituent and the ligand backbone. Thus, the solid state structure of phosphazene 3 corresponds to a deviation from idealized pseudo-tetrahedral geometry along the distortion coordinate illustrated in The solid state structure of N,N,N-phosphabicyclic phosphazene 4 has an expanded N3\u2013P1\u2013N4 bond angle of 4 (119.73(6)\u00b0), 14\u00b0 greater than the average angle in 8 (105.15(15)\u00b0). Furthermore, the N2\u2013P1\u2013N3 and N3\u2013P1\u2013N4 endocyclic angles were generally smaller relative to 8. As with constrained phosphazene 3, there was also an expansion of the N1\u2013P1\u2013N2 bond angle in 4 (129.22(6)\u00b0) versus8 (109.99(15)\u00b0, average of 3 angles), constituting a difference of 19\u00b0; this difference is greater than that of the 3/7 pair and is likely a result of increased steric congestion imposed by the N-methylanilides of 4.Similarly, via a bicyclic ligand framework results in a nontrigonal geometry along the distortion coordinate toward see-saw molecular structures.These solid state structures confirm our hypothesis that imposing geometric constraints 2.2.33, 4, 7, and 8 at the M06-2X/def2-TZVP level of theory as a way of quantifying their respective Lewis acidities and basicities and proton affinity (PA) calculations on 3 and 4 are significantly greater than their unconstrained analogues 7 and 8. This result conforms with qualitative predictions from the model system H3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNH ; upon distortion from pseudo-tetrahedral geometry, the phosphorus-based LUMOs decrease in energy, allowing for stronger interactions of exogenous anions like F\u2013 with nontrigonal 3 and 4 than with trigonal compounds 7 and 8.Fluoride ion affinities for constrained phosphazenes 3 and 7 are 238 kcal mol\u20131 and 239 kcal mol\u20131, respectively. For compounds 4 and 8, the PAs are 246 kcal mol\u20131 and 258 kcal mol\u20131, respectively. Given the magnitude of the calculated proton affinities, the difference in calculated PAs for 3/7 and 4/8 does not exceed 6% overall. This outcome is in accord with the interpretation from calculations in Section 2.1. in which molecular distortion would not be expected to affect significantly the N-based HOMOs responsible for Lewis basicity.Differences in proton affinities, on the other hand, are much smaller in magnitude. For instance, the computed PAs for compounds 2.3.2.3.13 could be prepared and characterized as indicated above, prolonged standing of solutions (ca. 3 d) at 60 \u00b0C led to the emergence of a new species with a low-field 31P NMR resonance (\u03b4 = \u201326.9 ppm). The formation and intensity of this new signal followed a concentration dependence in [3], suggesting a possible bimolecular origin. In accord with this observation, the identity of the new species was ultimately confirmed by single crystal X-ray diffraction analysis to be that of a head-to-tail homodimeric 1,3-diaza-2,4-diphosphetidine (cyclodiphosphazane) 3\u2032, which could be selectively crystallized from benzene solutions of 3/3\u2032 \u00c5) than the equatorial P\u2013N bonds (dP\u2013N = 1.665(3) \u00c5). Both bond distances are elongated as compared to monomeric 3 (dP\u2013N = 1.5069(14) \u00c5). In short, the structural metrics are consistent with a superposition of the Lewis structures for 3\u2032, displayed in Cyclophosphazane cal site . The mos3\u2032 in C6D6 at ambient temperature resulted in repopulation of the mixture containing both dimer 3\u2032 and monomer 3 as judged by 1H and 31P NMR spectroscopy. Consequently, we conclude that the formal 2 + 2 dimerization of 3 to 3\u2032 is reversible, as illustrated in 3 and 3\u2032 in the 31P NMR spectra is most consistent with a slow interconversion relative to the NMR timescale.Dissolution of a single-crystalline sample of O,N,O-phosphazene 3, dimerization of the constrained N,N,N-phosphazene 4 was not observed under any conditions.N-substituent prohibits close approach of a second phosphazene as would be necessary for dimer formation. Additionally, the phosphorus center of 4 is less Lewis acidic than that of 3 , so it is possible that decreased electrophilicity at P precludes sufficient driving force for phosphazene dimerization.In contrast to the deformed 2.3.2N-substituent has a controlling effect on the rate and position of monomer\u2013dimer equilibrium for phosphazenes based on O,N,O-platform 1. Whereas the N-dipp substituted phosphazene could be isolated in either monomeric (3) or dimeric (3\u2032) forms, O,N,O-phosphazenes bearing less sterically encumbered N-substituents could be isolated only in their dimeric cyclodiphosphazane forms moieties are detected as transient intermediates in the overall process, converting ultimately to the dimeric cyclodiphosphazane . By contrast, phosphazenes with electron-withdrawing phenyl, 10\u2032, \u03b4 \u201344.0 ppm) and alkyl N-substituents were observed only in their dimeric cyclodiphosphazane forms.The identity of the imino ne forms . In a tyosphorus . In situ31P NMR resonances of cyclodiphosphazanes 9\u2032\u201312\u2032 appear at noticeably lower field compared to 3\u2032, suggesting a geometric distinction between the very bulky 2,6-diisopropyl-substituted cyclodiphosphazane and less sterically demanding congeners. Single crystals of dimeric N-p-tolyl derivative 9\u2032 were obtained by slow evaporation of a benzene solution, and the structure was interrogated by X-ray diffraction \u00c5) and equatorial P\u2013N (dP\u2013N = 1.635(3) \u00c5) bond lengths for N-p-tolyl cyclodiphosphazane 9\u2032 are approximately 0.04 \u00c5 shorter than for N-dipp cyclodiphosphazane 3\u2032. We infer that the reduced steric congestion about the P2N2 core for 9\u2032 permits tighter association of the monomer subunits in a head-to-tail fashion that is manifest in the 31P isotropic chemical shielding differences. Congruent with this assessment, attempts to access monomeric phosphazenes 9\u201312 by heating of benzene solutions of 9\u2032\u201312\u2032 were unsuccessful; formal (2 + 2) dimerization appears to be prohibitively downhill in enthalpy and, therefore, irreversible for these less sterically congested cyclodiphosphazanes.The fraction . Globall PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN units is well-precedented in the literature, specifically for phosphazenes bearing strongly electron-withdrawing P-substituents or where relief of ring strain provides a driving force.O,N,O-phosphazenes (9\u2032\u201312\u2032) readily dimerize is thus a qualitative indication of the marked Lewis acidity of these phosphorus centers as compared to their acyclic congeners. Furthermore, the sum of the observations concerning the monomer\u2013dimer speciation of distorted phosphazenes 3/3\u2019 evidences a propensity for 1,2-ambiphilic reactivity of the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit, suggesting that intermolecular 1,2-additions of exogenous reagents might be feasible.Formal [2 + 2]-cyclodimerization of phosphazene P2.4.2.4.1 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit in deformed phosphazenes 3 and 4, we elected to attempt the 1,2-addition of \u03c3-bonded E\u2013H small molecules. To this end, treatment of O,N,O-phosphazene 3 with 1 equiv. of pinacolborane (HBpin) in C6D6 at room temperature resulted in rapid consumption of the starting materials and formation of a single new compound with a 31P NMR resonance at \u03b4 \u201343.7 ppm presenting as a doublet of triplets . The magnitude of the larger coupling constant is indicative of a direct P\u2013H linkage; existence of a P\u2013H moiety was confirmed in 1H NMR spectra by the appearance of a doublet centered at \u03b4 9.37 ppm with complementary coupling (1JP\u2013H = 837 Hz). Although attempts to obtain a solid state structure of 13 from X-ray diffraction analysis were unsuccessful, these spectroscopic signatures are consistent with formation of hydrido amido phosphorane 13 in which the O,N,O-chelate spans two apical and one equatorial position about a phosphorus-centered trigonal bipyramid, and the hydride and borylamide substituents reside in the equatorial plane. Further support for this assignment comes by way of analogy to previous results from our group. We reported previously that hydrido amido phosphoranes related to 13 are accessible via intermolecular N\u2013H oxidative addition to 3.3 gave a crystallographically characterized oxidative addition product (i.e. the des-boryl congener of 13) that exhibits spectroscopic features in close agreement with those obtained for 13. In short, the combined data lend strong evidence to the structural assignment of the B\u2013H addition product 13.To investigate reactivity of the PN,N,N-phosphazene 4 with 1 equiv. of pinacolborane in C6D6 at ambient temperature quickly consumed starting materials to yield a species 14 with a doublet 31P NMR signal at \u03b4 \u201337.6 ppm . Complementary coupling was observed in the 1H NMR spectrum with a doublet resonance at \u03b4 6.36 ppm. As with the reaction of 3 and HBpin, these spectral data are characteristic of pentacoordinated hydrido amido phosphorane featuring a direct P\u2013H bond. By analogy to previous results on the intermolecular N\u2013H oxidative addition of 2,6-diisopropylaniline to 4,14 as in N,N,N-ligand, equatorial N-dipp substituent, and an axial hydride.Likewise, treating 3 and 4, acyclic O,N,O- and N,N,N-phosphazenes 7 and 8 were unreactive with respect to pinacolborane under identical reaction conditions. Additionally, none of the dimeric cyclodiphosphazanes 9\u2032\u201312\u2032 were found to undergo reaction with HBpin. We conclude, therefore, that the ability of the phosphazenes 3 and 4 to undergo 1,2-addition of H\u2013Bpin is dependent on the distorted structure enforced by the trianionic heteroatom supporting structures, and that access to the monomeric form of the phosphazene is critical for intermolecular addition.By contrast to 2.4.2O,N,O-phosphazene 3 was also able to add B\u2013O \u03c3 bonds across the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit. Addition of 1 equiv. of n-butoxy catecholborane to a C6D6 solution of 3 at room temperature , which can be attributed to coupling between the phosphorus center and the vinylic protons of the O,N,O-ligand. The magnitude of this coupling is smaller than would be expected for \u03c35-phosphorus compounds with a planar, meridional O,N,O-chelate. This result suggests that antiperiplanarity between P and H has been lost; that is, the dihedral angle between the phosphorus and vinylic hydrogen atoms has decreased from 180\u00b0 in accordance with the Karplus equation for 3J scalar coupling,O,N,O-framework adopts a folded geometry.The deformed perature resultedO,N,O-folding (15 is the unexpectedly short distance between the ligand amido N atom and the N-dipp-bound boron (dN2\u2013B1 = 1.637(3) \u00c5), consistent with the presence of a dative interaction N2 \u2192 B1 in 15; pyramidalization of the boron atom evident in the solid state structure further evidences this conclusion. By consequence of this interaction, compound 15 may be viewed as a trigonal bipyramidal phosphorus compound supported by a tetracoordinating boroazaphosphatrane ligand, where the fifth apical binding site of the trigonal bipyramid is occupied by the n-butoxy substituent. Indeed, the apical bond distance dP1\u2013N2 is quite long (1.9392(19) \u00c5), conforming to precedent from cationic phosphatranescf. dP\u2013N = 1.986(5) \u00c5 for [HP(OCH2CH2)3N][BF4];29dP\u2013N = 1.967(8) \u00c5 for [HP(MeNCH2CH2)3N][BF4]15 is substantially longer than the equatorial P1\u2013N1 bond (1.6195(18) \u00c5), comprising a difference of more than 0.3 \u00c5. As a consequence, the trans apical P1\u2013O3 bond is found to be quite short (1.5906(16) \u00c5); in fact, the apical P\u2013O bond is shorter than the equatorial P\u2013O bonds (1.6242(16) \u00c5 and 1.6252(16) \u00c5). This observation runs counter to typical trigonal bipyramidal geometries, where the 3-center, 4-electron apical bonds are usually longer than the 2-center, 2-electron equatorial bonds. These unusual structural features of the B\u2013O adduct of phosphazene 3 likely arise from molecular constraint imposed by the O,N,O-ligand and by the Lewis acidic boron atom.A single crystal suitable for X-ray diffraction was grown from benzene solution, and the solid state structure corroborates the above conclusion regarding -folding . A disti3, N,N,N-ligated phosphazene 4 did not react with n-butoxy catecholborane, perhaps again due to increased steric congestion about the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit. Likewise, acyclic analogues 7 and 8 were unreactive to B\u2013O bonds.Unlike phosphazene 2.4.33 was reactive toward the Si\u2013H bond of phenylsilane. Treating phosphazene 3 with phenylsilane in C6D6 at 50 \u00b0C for 16 h . Likewise, a doublet resonance with a large coupling constant centered at \u03b4 9.44 ppm (1JP\u2013H = 802 Hz) was observed in the 1H NMR spectrum. Another complementary doublet signal, corresponding to ligand vinylic protons, appeared at \u03b4 5.34 ppm (3JP\u2013H = 31 Hz). Analogous to other \u03c35,\u03bb5-phosphorus compounds synthesized here (vide supra), the coupling constant of 31 Hz is indicative of a planar O,N,O-chelate, as in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond of 3 to give a hydrido phosphorane with a N-silyl substituent.In addition to activating B\u2013H and B\u2013O bonds, phosphazene for 16 h producedN,N,N-Phosphazene 4 also reacted with phenylsilane, but at a slower rate than 3. The conversion of 4 and phenylsilane to hydrido phosphorane 17 was completed after 48 h of heating at 80 \u00b0C in C6D6. The resulting 31P NMR spectrum showed one signal centered at \u03b4 \u201329.1 ppm ; the magnitude of the scalar coupling constant is characteristic of a P\u2013H bond, consistent with the structure of the \u03c35-phosphorus Si\u2013H addition product 17. By analogy to other N,N,N-ligated compounds synthesized earlier, we expect the trianionic chelate to adopt a folded structure, as in 7 and 8 were found to be unreactive to Si\u2013H addition. The fact that compounds of this type are robust to silane addition has been exploited by Fontaine, who has shown that phosphazenes similar to 8 can be used as Lewis base-catalysts for catalysed hydrosilylation of CO2.30Acyclic phosphazenes PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit of a phosphazene has often been invoked, albeit usually in tandem with subsequent elimination from P(v) and without direct observation of the elementary step. Kawashima has studied the intramolecular addition of a Si\u2013H bond to a functionalized phosphazene.in situ reduction of a phosphazene, presumably initiated by 1,2-addition of hydrosilane.via 1,2-addition via a trigonal bipyramidal hydrido amido phosphorane intermediate, but despite the prevalence of the 1,2-addition proposal, there do not exist discrete, well-characterized analogues of this key step. Our current results represent a rare well-defined addition reaction giving rise to stable pentacoordinate adducts that substantiate the notion of 1,2-addition of hydrosilanes to phosphazenes.The 1,2-addition of hydrosilane across the P3.O,N,O- and N,N,N-ligands exhibit increased cyclodimerization and 1,2-addition reactions of B\u2013H, B\u2013O, and Si\u2013H \u03c3 bonds as compared to acyclic congeners. The results of the combined experimental and theoretical studies above support the conclusion that nontrigonal distortion of phosphazenes leads to an enhancement of the 1,2-ambiphilic reactivity of the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN unit. In view of the multivarious roles of phosphazenes, the ability to master electronic structure and reactivity as a function of a modifiable parameter contributes to the discovery of novel applications. In conjunction with established approaches to synthetic tuning through substituent effects, the current results establish a rational geometry-based framework for modulating the reactivity of this important class of main group compounds, which may be leveraged in the design of functionally novel entities.Constrained phosphabicyclic phosphazenes supported by trianionic scaffolding 4.Full experimental details are available in the online ESI.4.1.6D6 (1 mL) was stirred at 40 \u00b0C for 16 h. All volatiles were removed in vacuo, and the resulting residue was triturated with pentane. The crude product was obtained after filtration, and pure 3 was isolated as a white solid by recrystallization from a 10\u2009:\u20091 dichloromethane/pentane solution . 1H NMR : \u03b4 7.23\u20137.21 , 7.12\u20137.07 , 7.07 , 5.49 , 3.83 , 1.40 , 0.91 ppm. 13C NMR : \u03b4 154.19, 141.29 , 123.03, 121.98, 112.43 , 32.64 , 29.35, 26.89, 23.75 ppm. 31P NMR : \u03b4 7.21 ppm. MS (ESI) calc'd for C24H37N2O2P (M+) 416.2593, found 416.2596.A solution of 1 with 2,6-diisopropylphenyl azide in C4.2.6D6 (1 mL) was stirred under ambient temperature for 12 h. The solvent was removed in vacuo, and the resulting solid product was recrystallized from a 10\u2009:\u20091 dichloromethane/pentane solution . 1H NMR : \u03b4 7.26 , 7.16 , 7.09\u20137.02 , 6.98\u20136.85 , 6.77 , 6.23 , 3.65 , 2.73 , 1.22 ppm. 13C NMR : \u03b4 141.38, 141.00 , 138.09 , 134.58 , 124.56, 123.26, 121.34, 120.14, 116.34 , 108.66 , 29.29 , 23.75 ppm. 31P NMR : \u03b4 14.54 ppm. MS (ESI) calc'd for C26H31N4P (M+) 430.2286, found 430.2290.A solution of 2 with 2,6-diisopropylphenyl azide in C4.3.6D6 (0.3 mL) was stirred at ambient temperature for 15 min. The solvent was removed in vacuo to afford the crude product . 1H NMR : \u03b4 9.38 , 7.27\u20137.25 , 7.08\u20137.04 , 5.49 , 3.62\u20133.56 , 1.53 , 1.19 , 1.15 ppm. 13C NMR : \u03b4 150.73 , 147.14, 126.64, 124.52 , 124.02, 123.42, 100.51 , 82.52, 31.69, 28.25, 27.51, 24.66, 23.62, 23.26 ppm. 31P NMR : \u03b4 \u201343.02 ppm. MS (ESI) calc'd for C30H49BN2O4P (M\u2013H+) 543.3518, found 543.3523.A solution of 3 and HBpin in C4.4.6D6 (0.3 mL) was stirred at 80 \u00b0C for 48 h. All volatiles were removed in vacuo to afford 20 as a yellow oil . 1H NMR : \u03b4 7.32 , 7.14\u20136.99 , 6.95 , 6.87 , 6.73 , 6.37 , 5.75 , 5.05 , 3.45\u20133.33 , 2.49 , 1.15 , 1.06 ppm. 13C NMR : \u03b4 148.30 , 137.93, 135.77 , 134.65 , 134.25, 133.46, 129.01, 127.16 , 123.90 , 121.42, 119.38, 113.89 , 108.72 , 29.69 , 27.61, 26.24, 23.84 ppm. 31P NMR : \u03b4 \u201328.54 ppm. MS (ESI) calc'd for C32H40N4PSi (M + H+) 539.2760, found 539.2763.A solution of 4 and phenylsilane in CThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The neutral molecule NPrO and its anion NPrO\u2013 are characterized to be linear pentavalent praseodymium nitride-oxides that possess Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN triple bonds and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bonds. \u2013 are produced via co-condensation of laser-ablated praseodymium atoms with nitric oxide in a solid neon matrix. Combined infrared spectroscopy and state-of-the-art quantum chemical calculations confirm that both species are pentavalent praseodymium nitride-oxides with linear structures that contain Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN triple bonds and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bonds. Electronic structure studies show that the neutral NPrO molecule features a 4f0 electron configuration and a Pr(v) oxidation state similar to that of the isoelectronic PrO2+ ion, while its NPrO\u2013 anion possesses a 4f1 electron configuration and a Pr(iv) oxidation state. The neutral NPrO molecule is thus a rare lanthanide nitride-oxide species with a Pr(v) oxidation state, which follows the recent identification of the first Pr(v) oxidation state in the PrO2+ and PrO4 complexes . This finding indicates that lanthanide compounds with oxidation states of higher than +IV are richer in chemistry than previously recognized.The neutral molecule NPrO and its anion NPrO Combined matrix-isolation infrared absorption spectroscopy and sophisticated quantum chemistry studies reveal that both species are linear pentavalent compounds with Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN triple bonds and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bonds, and that the neutral NPrO molecule, which is isoelectronic to the PrO2+ cation, is also a pentavalent praseodymium species with a Pr center in the highest +V oxidation state. The NPrO species thus provides additional evidence that lanthanides can form complexes with oxidation states higher than IV.Herein, we report a combined experimental and theoretical study on the neutral NPrO molecule and its anion NPrO15NO were used without further purification. The as-deposited samples were subjected to annealing and photolysis experiments to initiate diffuse and photo-induced reactions. The infrared absorption spectra of the products were recorded in the mid-infrared region (4000\u2013450 cm\u20131) using a Bruker Vertex 80V spectrometer at a resolution of 0.5 cm\u20131 using a liquid nitrogen cooled HgCdTe (MCT) detector.Praseodymium nitride-oxide species were prepared by reactions of praseodymium atoms and nitric oxide in solid neon, and were studied by infrared absorption spectroscopy as described in detail previously.ab initio single-reference WFT method of coupled-clusters with singles, doubles and perturbative triples (CCSD(T))16Quantum chemical calculations were performed at the density functional theory (DFT) and wavefunction theory (WFT) levels to gain insight into the geometries, electronic structures, bonding and oxidation states of the observed species. The hybrid B3LYP functionalIn addition, multi-configurational complete active space self-consistent-field theory and complete active space with second-order perturbation theory (CASSCF/CASPT2) methods2\u20134d10] for Pr, and [1s2] for O and N. Kohn\u2013Sham molecular orbital (MO) analysis and calculations of Mayer bond order indexes25Electronic structure and bonding analyses were performed at the B3LYP level using the ADF 2013 program.\u2013 species in a solid argon matrix but did not address their oxidation states.2, (NO)2+ and (NO)2\u2013 absorptions,\u20131. This band can be attributed to diatomic PrO absorption, which is observed at 817.0 cm\u20131 in solid argon and at 826 cm\u20131 in the gas phase.\u20131 were also observed upon sample deposition, sharpened and decreased upon sample annealing at 10 and 12 K, and diminished under \u03bb > 800 nm light irradiation. Three additional groups of absorptions were produced when the sample was annealed at high temperatures (10 and 12 K) at the expense of NO absorption. The first group involves two doublet absorptions at 926.2/918.5 and 762.2/755.9 cm\u20131, which slightly decreased under \u03bb > 800 nm irradiation. The second and third groups each involve three absorptions at 1862.6, 886.6 and 751.6 cm\u20131 and 1825.2, 1720.6 and 826.3 cm\u20131, respectively. The latter two groups of absorptions were destroyed upon \u03bb > 800 nm light irradiation, during which absorption at 747.3 cm\u20131 was produced, which can be assigned to the antisymmetric OPrO stretching vibration of the weakly perturbed PrO2 complex, as this absorption shows no shift with 15NO with a band position very close to that of PrO2.15NO and 14NO + 15NO samples. Selected regions of the isotopic spectra are shown in 26The reaction products from the co-deposition of laser-ablated praseodymium atoms with nitric oxide in excess argon were previously studied using Fourier transform infrared absorption spectroscopy, which indicated the formation of NPrO and NPrO\u20131 absorptions are assigned to the NPrO molecule trapped in solid neon in two trapping sites. The upper doublet shifted to 903.9/896.6 cm\u20131 with 15NO. The observed quite large 15N-isotopic shift indicates that this mode is mainly a Pr\u2013N stretching vibration. The low doublet shifted to 757.0/750.7 cm\u20131 with 15NO, and the quite small 15N-isotopic shift implies that this mode is largely due to a Pr\u2013O stretching vibration. Analysis of the spectrum obtained from the experiment using the mixed 14NO + 15NO sample confirms the involvement of only one N atom and one O atom in this molecule. The two stretching vibrational modes of NPrO were observed at 900.8 and 742.0 cm\u20131 in solid argon,\u20131, respectively, thus indicating significant argon matrix effects that are non-negligible. The Pr\u2013N stretching frequency of NPrO is higher than that of diatomic PrN, which was reported at 857.9 cm\u20131 in solid argon.\u20131 in Ne and 817.0 cm\u20131 in Ar). The NPrO absorptions increased markedly upon annealing in both neon and argon matrices, indicating that the ground state praseodymium atoms can insert into the N\u2013O bond of nitric oxide spontaneously with negligible activation energy required.The 926.2/918.5 and 762.2/755.9 cm\u20131 absorptions observed right after sample deposition correspond to the absorptions observed at 718.2 and 612.3 cm\u20131 in solid argon, which were attributed to the NPrO\u2013 anion species.\u20131 absorption shows almost no shift with 15NO, thus indicating that this band is a pure Pr\u2013O stretching mode. In contrast, the 730.9 cm\u20131 band shifted to 709.2 cm\u20131 with 15NO, and the isotopic 14N/15N frequency ratio of 1.0306 implies that it is a Pr\u2013N stretching mode. The argon-to-neon shifts of 12.7 and 11.6 cm\u20131 are only about half of those of the neutral NPrO, thus suggesting that the NPrO\u2013 anion is less affected by the noble gas atoms. The NPrO\u2013 anion is presumably formed via electron capture of the neutral NPrO molecule during the co-condensation process. It is well-known that laser ablation of a metal target can produce not only neutral metal atoms but also metal cations and electrons.\u20131 at the CCSD(T) level of theory , which is consistent with the experimental observation that the NPrO\u2013 anion is photobleached upon \u03bb > 800 nm light irradiation.The rather weak 730.9 and 623.9 cm\u20131 absorptions are assigned to an NPrO(NO) complex. The upper mode shifted to 1829.8 cm\u20131 with 15NO, with the band position and isotopic shift indicating a terminally bound nitrosyl stretching vibration. The 886.6 and 751.6 cm\u20131 bands are assigned to the Pr\u2013N and Pr\u2013O stretching modes, respectively, which are slightly red-shifted from those of the NPrO molecule. The 1825.2, 1720.6 and 826.3 cm\u20131 absorptions are assigned to an NPrO(NO)2 complex, with the two upper absorptions corresponding to N\u2013O stretching vibrations. The spectrum of the mixed 14NO + 15NO sample indicates that two equivalent NO subunits are involved in these two modes. The 826.3 cm\u20131 absorption exhibits less 15N-isotopic shift (9.1 cm\u20131) than the Pr\u2013N stretching mode of NPrO (22.3 cm\u20131), thus implying that the 826.3 cm\u20131 absorption can instead be assigned as an antisymmetric NPrO stretching mode. Calculations also suggested that the symmetric stretching is too weak to be observed.The 1862.6, 886.6 and 751.6 cm\u20131 lower in energy than the singlet state at the B3LYP level, but is 10.0 kcal mol\u20131 higher than the latter at the more accurate CCSD(T) level. Both the quintet and triplet states can thus be ruled out as they are clearly excited states. The calculated Pr\u2013N and Pr\u2013O stretching vibrational frequencies are compared to the experimental values in Theoretical calculations were performed to elucidate the structure, oxidation states and bonding of the observed species. Geometry optimizations were performed at both the B3LYP and CCSD(T) levels of theory on the neutral NPrO molecule with spin multiplicity of 1, 3 and 5, and the results are listed in 22+) and the PrO2+ ion, the neutral NPrO molecule in the singlet ground electronic state also prefers a linear structure in order to optimize the overlap of the Pr 5d and 4f orbitals with those of the N and O atoms. The Pr\u2013N and Pr\u2013O bond lengths are predicted to be 1.677 and 1.765 \u00c5, respectively, at the B3LYP level of theory, and CCSD(T) calculations give slightly higher values (1.697 and 1.775 \u00c5). The Pr\u2013N bond length is about 0.14 \u00c5 (B3LYP) or 0.12 \u00c5 (CCSD(T)) smaller than the sum of the triple-bond covalent radii of Pr and N proposed by Pyykk\u00f6 et al.2+ calculated at the same level of theory.Similar to the isovalent uranyl ion (UO1\u03a3 singlet ground state of NPrO is isoelectronic to PrO2+ and has a ground electronic configuration of [core](1\u03c0)4(1\u03c3)2(2\u03c0)4(2\u03c3)2(4f5d)0. As shown in 0d0) configuration and that Pr\u2013N is triple bonded and Pr\u2013O is double bonded, which is consistent with the Lewis electron-pair model. Accordingly, the linear singlet NPrO neutral molecule can be classified as a pentavalent praseodymium species with an oxidation state of +V as the PrO2+ cation. Natural bond orbital (NBO) analyses scale\" fill=\"currentColor\" stroke=\"none\">N and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO multiple bonding in NPrO with two sets of localized \u03c32\u03c04 bonds. The Pr\u2013N \u03c3 bond is composed of 60.9% Pr and 36.8% N character, with a Pr 5d\u2009:\u20094f contribution of 21\u2009:\u200974 and an N 2s\u2009:\u20092p contribution of 13\u2009:\u200987. The two degenerate \u03c0 bonds are each composed of 32.5% Pr and 67.5% N character, with a Pr 5d\u2009:\u20094f contribution of 41\u2009:\u200958. The Pr\u2013O \u03c3 bond is composed of 30.9% Pr and 67.3% O character, with a Pr 5d\u2009:\u20094f contribution of 26\u2009:\u200971 and an O 2s\u2009:\u20092p contribution of 13\u2009:\u200987. Each of the two degenerate Pr\u2013O \u03c0 bonds that represent one covalent and one dative bond are composed of 17.1% Pr and 82.8% O character, with a Pr 5d\u2009:\u20094f contribution of 44\u2009:\u200955. These bonding analyses clearly show that the Pr\u2013O bonding interaction is much more strongly polarized than the Pr\u2013N bonding interaction, which is consistent with the electronegativity difference and the lower Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond order. The greater covalency of the Pr\u2013N interaction results in a shorter Pr\u2013N bond (1.677 \u00c5 at B3LYP and 1.697 \u00c5 at CCSD(T)) than the Pr\u2013O bond (1.765 \u00c5 at B3LYP and 1.775 \u00c5 at CCSD(T)), albeit the atomic radius of oxygen is slightly smaller than that of nitrogen. As has been discussed before,2+ and NPrO species. In contrast, our preliminary calculations show that the analogous protactinium nitride-oxide NPaO species is a Pa(v) complex with a slightly bent structure because of the significant participation of Pa 5f orbitals in addition to the 6d/7s ones in the chemical bonding.The 2+ and NPrO, in terms of O2\u2013 and N3\u2013, with PrO3+. In this diagram, only the 2p atomic orbitals of the N and O atoms are shown, with the 2s ones omitted for clarity. The bonding interactions in these two isoelectronic species are in general quite similar. The interactions of the three 2p atomic orbitals of O2\u2013 or N3\u2013 with the highest fully occupied 1\u03c0 and 1\u03c3 MOs of PrO3+ lead to the six highest fully occupied MOs of PrO2+ and NPrO level. The calculated red-shifts from the corresponding modes of neutral NPrO are 192.3 and 174.8 cm\u20131 at the CCSD(T) level and 207.2 and 185.2 cm\u20131 at the B3LYP level, which are in reasonable agreement with the experimentally observed shifts of 195.3 and 138.3 cm\u20131 (for the major site absorptions of NPrO in solid neon) when considering that no matrix effects are accounted for. The NPrO\u2013 anion in the 2\u03a6 ground electronic state has an electronic configuration of (core) (1\u03c0)4(1\u03c3)2(2\u03c0)4(2\u03c3)2(1\u03c6)1. The unpaired electron is located on the 1\u03c6 MO that is a non-bonding Pr-based 4f atomic orbital, which is consistent with Mulliken population analysis which shows that the spin density is located on the Pr center. Therefore, the anion can be regarded as being formed by adding an electron to the 1\u03c6 LUMO of the neutral NPrO molecule. The extra electron reduces the natural charge of the Pr center from +1.49 in NPrO to +1.14 in the NPrO\u2013 anion, which significantly increases the ionic radii and reduces the electrostatic interaction in the anion. The Pr center in the 2\u03a6 state of NPrO\u2013 has an (f\u03c61d0) electronic configuration, and thus corresponds to a Pr(iv) oxidation state. Natural bond orbital analyses indicate that despite the Pr(iv) oxidation state in NPrO\u2013, the 2\u03a6 ground state NPrO\u2013 anion is also a pentavalent species with Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO multiple bonds scale\" fill=\"currentColor\" stroke=\"none\">N and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds, respectively or 7.0 kcal mol\u20131 (CCSD(T)) higher in energy than the 2\u03a6 ground state. This 2\u0394 state NPrO\u2013 anion has a Pr(f\u03b41d0) configuration and an oxidation state of +IV as well. The most stable quartet state with a linear structure, an (f\u03b41f\u03c61\u03c31) electronic configuration and a Pr(iii) oxidation state is 15.4 (B3LYP) or 43.3 kcal mol\u20131 (CCSD(T)) higher in energy than the ground state.The NPrOtructure . The Pr\u2013 Table S3, which aectively . Another\u2013 species, additional single-point multi-configurational SCF calculations using CASSCF were performed on the optimized structures of the linear singlet neutral NPrO molecule and the doublet NPrO\u2013 anion at the B3LYP level of theory. The CASSCF calculations, with 12 electrons in 12 orbitals including six bonding orbitals and six antibonding orbitals (f0d0) configuration from the CASSCF calculations has a dominated weight of 86.7%, the sum of the natural orbital occupation numbers (NOONs) of the six low-lying orbitals amounts only to 0.29 e\u2013 in total. Moreover, the T1-diagnostic value of 0.056 obtained from the single-determinant CCSD(T) calculation also implies that the wavefunction does not exhibit particularly large multi-reference features (f1d0) configuration has a dominated weight of 88.8% and that the sum of the NOONs of the five low-lying orbitals amounts only to 0.27 e\u2013. These results indicate that the single-reference DFT and CCSD(T) calculations are reasonably reliable, and the assignments of the oxidation states of Pr(v) in neutral NPrO and Pr(iv) in the NPrO\u2013 anion are appropriate due to the single reference features of their wavefunctions and the calculated state energies.To assess the potential single-reference nature of the electronic structures of the NPrO and NPrOs Fig. S4 on the sfeatures . Similars Fig. S5 found th\u2013 molecules, our experiments show that the NPrO molecule further reacts with nitric oxide to form NPrO(NO) and NPrO(NO)2 complexes spontaneously upon annealing. The NPrO(NO) complex is predicted to have a doublet ground state with a Cs symmetry 2 complex is predicted to have a singlet ground state is reduced to Pr(iv) and that the complexes are converted to PrO2 and N2 under near infrared light irradiation.In addition to the NPrO and NPrOy Fig. S6, which ie Fig. S6, which c2 complexes indicates that NPrO is a Lewis acid, which points to the possibility of forming complexes with noble gas atoms. DFT/B3LYP calculations with or without dispersion correction (D3) were thus performed on the complexes formed between NPrO and noble-gas atoms for comparison. The total Ng binding energies are calculated as the energy change for the process: (NPrO)Ngn \u2192 NPrO + nNg. The calculated binding energies are listed in Table S26 complex, which is predicted to have a C6v structure with all the argon atoms equatorially coordinated to the metal center. The total binding energy of the six argon atoms is 12.7 kcal mol\u20131 with dispersion correction. Upon argon atom coordination, the Pr\u2013N and Pr\u2013O stretching modes red-shifted by 11.9 and 7.9 cm\u20131, respectively. This result implies that the NPrO molecule trapped in a solid argon matrix may be regarded as a matrix-isolated NPrO(Ar)6 complex, as in the case of the argon-coordinated CUO molecule.5 complex has a slightly smaller binding energy , which might be partially responsible for the different matrix sites of NPrO observed. However, consistent with the much lower coordination ability or Lewis basicity of neon, the binding between Ne atoms and NPrO is rather weak, which leads to a total binding energy of only 7.2 kcal mol\u20131 for the NPrO(Ne)6 complex, thus suggesting that the coordination effect of neon atoms compared to argon atoms is somewhat more insignificant.Observation of the NPrO(NO) and NPrO(NO) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO multiple bonds. Thus, the neutral NPrO molecule is another pentavalent species with a Pr(v) oxidation state, which follows the recently reported PrO2+ complexes with a Pr(v) center.\u2013 anion is also formed via electron capture of the neutral molecule during the co-condensation process. Although the anion exhibits quite large red-shifted Pr\u2013N and Pr\u2013O stretching frequencies relative to those of the neutral molecule, the anion is characterized to be another pentavalent praseodymium species with Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and Pr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO multiple bonds. Especially noteworthy is the Pr(iv) oxidation state of this pentavalent NPrO\u2013 complex. Evidence is also presented for the formation of the NPrO(NO) and NPrO(NO)2 complexes, which convert to PrO2 complexes with a Pr(iv) oxidation state under \u03bb > 800 nm light irradiation. Theoretical calculations suggest that NPrO is weakly coordinated by noble gas atoms in solid noble gas matrices. The present study together with our previous work on PrO2+ and PrO4 complexesv) oxidation state are plausible in both oxides and nitrides. Further investigations into lanthanide oxofluorides, nitride-oxides, halides and carbides would be interesting to explore the undeveloped pentavalent lanthanide chemistry.The reactions of praseodymium atoms with nitric oxide are studied using matrix-isolation infrared absorption spectroscopy. The ground state Pr atoms react with NO to spontaneously form an inserted NPrO molecule upon annealing in solid neon, with the molecule characterized to have a linear structure with both PrSupplementary informationClick here for additional data file."}
+{"text": "A systematic, efficient route to the first heavier tetrylidyne complexes of niobium starting from the carbonyl niobate (NMe4)[Nb(CO)4(\u03ba2-tmps)] is presented. 4)[Nb(CO)4(\u03ba2-tmps)] (1) (tmps = MeSi(CH2PMe2)3) with a suitable organotetrel(ii)halide. Compound 1 was obtained from (NMe4)[Nb(CO)6] and the triphosphane tmps by photodecarbonylation. Reaction of 1 with the disilene E-Tbb(Br)Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(Br)Tbb in the presence of 4-dimethylaminopyridine afforded selectively the red-brown silylidyne complex methyl)phenyl). Similarly, treatment of 1 with E(ArMes)Cl afforded after elimination of (NMe4)Cl and two CO ligands the deep magenta colored germylidyne complex (3-Ge), and the deep violet, light-sensitive stannylidyne complex (3-Sn), respectively. Formation of 3-Sn proceeds via the niobiastannylene [(\u03ba3-tmps)(CO)3Nb\u2013SnArMes] (4-Sn), which was detected by IR and NMR spectroscopy. The niobium tetrylidyne complexes 2-Si, 3-Ge and 3-Sn were fully characterized and their solid-state structures determined by single-crystal X-ray diffraction studies. All complexes feature an almost linear tetrel coordination and the shortest Nb\u2013E bond lengths (d(Nb\u2013Si) = 232.7(2) pm; d(Nb\u2013Ge) = 235.79(4) pm; d(Nb\u2013Sn) = 253.3(1) pm) reported to date. Reaction of 3-Ge with a large excess of H2O afforded upon cleavage of the Nb\u2013Ge triple bond the hydridogermanediol Ge(ArMes)H(OH)2. Photodecarbonylation of [CpNb(CO)4] (Cp = \u03b75-C5H5) in the presence of Ge(ArMes)Cl afforded the red-orange chlorogermylidene complex (5-Ge). The molecular structure of 5-Ge features an upright conformation of the germylidene ligand, a trigonal\u2013planar coordinated Ge atom, and a Nb\u2013Ge double bond length of 251.78(6) pm, which lies in-between the Nb\u2013Ge triple bond length of 3-Ge (235.79(4) pm) and a Nb\u2013Ge single bond length (267.3 pm). Cyclic voltammetric studies of 2-Si, 3-Ge, and 3-Sn reveal several electron-transfer steps. One-electron oxidation and reduction of the germylidyne complex of 3-Ge in THF are electrochemically reversible suggesting that both the radical cation and radical anion of 3-Ge are accessible species in solution.A systematic, efficient approach to first complexes containing a triple bond between niobium and the elements silicon, germanium or tin is reported. The approach involves a metathetical exchange of the niobium-centered nucleophile (NMe Whereas earlier work concentrated exclusively on group 6 metals, recent studies have shown that also group 7, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE functionality. Group 5 metal complexes featuring a triple bond to the heavier tetrels (E = Si\u2013Pb) are presently not known, and even compounds with a M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE double bond are very scarce and poorly characterized illustrating the challenge to make such compounds. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE (E = Si\u2013Sn) triple bonds.Complexes of the general formula were prepared, following the method developed by J. E. Ellis et al.m-terphenyltetrel(ii)halides E(ArMes)Cl = 2,4,6-trimethylphenyl).4)[Nb(CO)6] with Ge(ArMes)Cl in refluxing toluene did not provide any evidence for a conversion of the niobate even after prolonged heating, probably due to the poor nucleophilicity of [Nb(CO)6]\u2013. Therefore, as next we turned our attention to niobates containing ligands with a higher \u03c3-donor/\u03c0-acceptor ratio than CO, such as trialkyl- or triarylphosphanes. Various carbonyl(phosphane) niobates of the general formula [Nb(CO)4L2]\u2013 (L2 = bidentate di- or oligo-arylphosphane ligand) have been accessed from [Nb(CO)6]\u2013 upon photolytic CO substitution.2PMe2)3 (tmps).12We decided to apply the first method, given the availability of anionic niobium carbonyl complexes.4)[Nb(CO)6] was carried out in the presence of one equivalent of tmps in THF at room temperature. A high-power blue light LED (\u03bb = 465 nm) was used instead of a high-pressure mercury UV-lamp. The use of a nearly monochromatic source with an exciting wavelength close to the longest-wavelength absorption maximum of [Nb(CO)6]\u2013 (\u03bbmax = 440 nm in CH2Cl2)11Photolysis of (NMe4(\u03ba2-tmps)]\u2013 proceeding via the pentacarbonyl intermediate [Nb(CO)5(\u03ba1-tmps)]\u2013 (\u03bd(CO) in THF: 1966 (m), 1821 (vs) cm\u20131). After work-up the salt (NMe4)[Nb(CO)4(\u03ba2-tmps)] (1) was isolated in nearly quantitative yield (97%) as an orange, analytically pure, very air-sensitive powder, which decolorizes immediately upon exposure to air. The salt decomposes upon heating at 142 \u00b0C to a dark brown mass, and is well soluble in acetonitrile and tetrahydrofurane (THF), but only moderately soluble in benzene, toluene, and diethyl ether. Attempts to grow suitable single crystals of 1 for an X-ray diffraction study failed, however unambiguous proof for the composition and structure of 1 was provided by elemental analysis, IR spectroscopy and 1H, 13C{1H}, 31P{1H} and 29Si{1H} NMR spectroscopy. The IR spectrum of 1 in THF displays four \u03bd(CO) absorption bands at 1900, 1787, 1764 and 1732 cm\u20131 4 fragment.\u03bd(CO) bands of 1 are shifted to lower frequencies than those of [Nb(CO)4(Ph2PCH2CH2PPh2)]\u2013 (\u03bd(CO) in THF = 1908, 1806, 1782 and 1746 cm\u20131) or related disubstituted arylphosphane-carbonyl niobates.1, which enhances the electron density at the metal center and leads to a stronger Nb(d\u03c0) \u2192 CO(\u03c0*) backbonding and softening of the CO bonds in 1. The NMR spectra of 1 corroborate the presence of an overall Cs symmetric complex, in which one of the arms of the tripodal ligand tmps is pendant and the other two arms are bonded to the niobium center. For example, the 31P{1H} NMR spectrum of 1 displays a sharp singlet for the 31P nucleus of the pendant CH2PMe2 arm, which appears at almost the same position (\u03b4(PA) = \u201355.8 ppm in benzene-d6) as that of the non-coordinated (\u201cfree\u201d) tmps (\u03b4(P) = \u201355.1 ppm in benzene-d6), and a very broad signal for the two symmetry-equivalent Nb-bonded 31P nuclei at considerably lower field (\u03b4(PB) = \u201311.6 ppm in benzene-d6) = 696 Hz) is caused by the quadrupole moment of the 93Nb nucleus and its effect on the relaxation time.29Si{1H} NMR spectrum of 1, which shows a sharp signal for the bridgehead Si atom, that is split to a doublet of triplets = 14.7 Hz, 2J = 8.2 Hz). A positional exchange of the pendant and the Nb-bonded arms of the tmps ligand in 1 was not observed in solution at 298 K.In fact, IR-monitoring of the reaction revealed a slow, but very selective conversion into the tetracarbonyl niobate chloride Ge(ArMes)Cl in toluene at \u201340 \u00b0C followed by warming to room temperature afforded rapidly and selectively the germylidyne complex (3-Ge) , that is moderately soluble in benzene and toluene, and well soluble in THF. No evidence for the formation of the putative metallogermylene intermediate [(\u03ba3-tmps)(CO)3Nb\u2013GeArMes] could be obtained during IR monitoring of the reaction of 1 with Ge(ArMes)Cl in toluene, the reaction starting at \u201335 \u00b0C and proceeding rapidly with CO evolution below 0 \u00b0C.Similarly, treatment of complex ] (3-Ge) . Compounm-terphenyltin(ii)chloride Sn(ArMes)Cl with 1 in toluene afforded after stirring at ambient temperature the brick-red metallostannylene [(\u03ba3-tmps)(CO)3Nb\u2013SnArMes] (4-Sn) with a small amount of the stannylidyne complex (3-Sn) . Prolong4-Sn to afford 3-Sn is a remarkable, new type of reaction in the chemistry of metallostannylenes. In fact previous attempts to transform the metallostannylenes [Cp(CO)3M\u2013SnR] ,2Fe\u2013SnR] 3W\u2013Sn(IDipp)]+ (Idipp = C[N(Dipp)CH]2, Dipp = C6H3\u20132,6-iPr2)4-Sn and decreases thereby the barrier for a CO dissociation. In addition, formation of a strong Nb PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSn triple bond resulting from the higher energy and larger radial extension of the d orbitals, which are engaged in the Nb(d\u03c0) \u2192 SnR(\u03c0*) back bonding, may be also a driving force for the reaction.Decarbonylation of 2-Si, 3-Ge and 3-Sn were characterized by elemental analyses, IR spectroscopy and 1H, 13C{1H}, 31P{1H}, 29Si{1H} and 119Sn{1H} NMR spectroscopy. In addition their molecular structures were determined by single-crystal X-ray crystallography (3-bonded) tmps ligand, which spans three facial coordination sites with the P\u2013Nb\u2013P bite angles varying in a small range (85.3\u201387.9\u00b0). A view along the Si\u00b7\u00b7\u00b7Nb vector reveals that the CH2 groups connecting the bridgehead Si atom with the P donors are twisted out creating a local C3 symmetric, right or left-handed conformation, which reduces the bite of the chelating triphosphane ligand and optimizes the bonding with the niobium center pm) is ca. 28 pm shorter than the Nb\u2013Si single bonds of silyl complexes (d(Nb\u2013Si)mean of 28 structurally characterized complexes = 261.3 pm),3-Ge (235.79(4) pm) ca. 31 pm shorter than a Nb\u2013Ge single bond (d(Nb\u2013Ge)mean = 267.3 pm).3-Sn (253.3(1) pm) is ca. 30 pm shorter than a Nb\u2013Sn single bond (d(Nb\u2013Sn)mean 282.9 pm).2-Si, 3-Ge and 3-Sn with those of related molybdenum tetrylidyne complexes scale\" fill=\"currentColor\" stroke=\"none\">Si) in = 222.41(7) pm;1d scale\" fill=\"currentColor\" stroke=\"none\">Ge) in (R = C(SiMe3)3, ArMes, ArTrip) = 227\u2013228 pm;d scale\" fill=\"currentColor\" stroke=\"none\">Sn) in trans- = 248\u2013249 pm) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE triple bond lengths compare reasonably well with the difference (7 pm) of the metallic radii of the two elements .et al.2-Si, 3-Ge and 3-Sn, are however, longer than the sum of the theoretically predicted triple bond radii scale\" fill=\"currentColor\" stroke=\"none\">E)calc = Si: 218 pm, Ge: 230 pm, Sn: 248 pm).The tetrylidyne complexes 2-Si: 159.2(2)\u00b0, 3-Ge: 164.0(1)\u00b0, 3-Sn: 160.9(3)\u00b0). Bending occurs in all cases towards the CO ligands. It is presently unclear, whether this phenomenon, which is also observed in a series of group 6 metal dicarbonyl ylidyne complexes, is of steric or electronic origin or both. No clear evidence for steric congestion is at least provided by the molecular structures of 2-Si, 3-Ge and 3-Sn. For example, the closest van der Waals contacts were found in 2-Si between the methyl groups of the tmps ligand and the SiMe3 methyl groups of the Tbb substituent (d(H\u00b7\u00b7\u00b7H) = 244 pm). These contacts are longer than twice the van der Waals radius of hydrogen (rvdW(H) = 110 pm). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE\u2013R atom sequence from linearity does not require a lot of energy, indicating that subtle electronic effects may cause such a bending.26In all complexes the tetrylidyne ligand is slightly bent at the tetrel center as evidenced by the bonding angle Nb\u2013E\u2013C1 bands of almost equal intensity, which are typical for cis-dicarbonyl complexes and can be assigned to the in-phase (A\u2032 symmetric) and out-of-phase (A\u2032\u2032 symmetric) CO stretching modes assuming local Cs symmetry of the M(CO)2 fragment (\u03bd(CO) bands of 3-Sn appear at lower frequencies (1851 and 1791 cm\u20131 in toluene) than those of 3-Ge (1868 and 1805 cm\u20131 in toluene), which suggests that the stannylidyne ligand SnArMes has a higher \u03c3-donor/\u03c0-acceptor ratio than the germylidyne ligand GeArMes. Notably, the \u03bd(CO) bands of 2-Si appear also at lower wavenumbers (1855 and 1790 cm\u20131 in toluene) than those of 3-Ge. This shift can be rationalized with the stronger +I effect of the Tbb substituent, leading to a higher \u03c3-donor/\u03c0-acceptor ratio of the silylidyne ligand SiTbb than that of the germylidyne ligand GeArMes. The low-frequency position of the \u03bd(CO) bands of 2-Si, 3-Ge and 3-Sn suggests the presence of an electron-rich Nb center that is engaged in strong Nb(d\u03c0) \u2192 CO(\u03c0*) backbonding. Additional evidence for a strong Nb(d\u03c0) \u2192 CO(\u03c0*) backbonding is provided by the 13C{1H} NMR spectra, which all display a broad CO signal at even lower field (\u03b4CO = 238.7 ppm (2-Si), 239.2 ppm (3-Ge), 238.9 ppm (3-Sn)) than that of 1 (\u03b4CO = 226.5 ppm).Cs symmetry of the tetrylidyne complexes in solution and a rapid rotation of the tetrel-bonded aryl group about the E\u2013Caryl bond. The signals of all nuclei directly attached to the quadrupolar 93Nb nucleus are significantly broadened due to fast relaxation (vide supra). For example, the 29Si{1H} NMR spectrum of 2-Si displays at 298 K a very broad signal (\u0394\u03bd1/2 = 130 Hz) for the Nb PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi nucleus at \u03b4 = 267.8 ppm, for which the 2J coupling could not be resolved. In comparison, the remote positioned bridgehead Si atom of the tmps ligand and the SiMe3 groups of the Tbb substituent give rise to sharp signals at \u03b4 = \u20130.7 ppm and +1.5 ppm, respectively, with the first of these signals being split into a quartet due to coupling to the three 31P nuclei = 9.7 Hz) and \u201310.7 ppm (\u0394\u03bd1/2 \u2248 187 Hz at 283 K), respectively, instead of two 31P NMR signals expected for an AX2 spin system coupling of 20.9 Hz as illustrated by the 31P NMR spectrum of 3-Ge at 193 K at \u03b4 = 829.7 ppm . Similan system . Broadneat 193 K . Taking . S36 ESI).3-Ge and the related molybdenum germylidyne complexes (R = C(SiMe3)3, ArMes, ArTrip). Thus treatment of with H2O or MeOH (one equiv.) in diethyl ether at 0 \u00b0C followed by warming to ambient temperature afforded within one hour selectively the brown hydroxy/methoxygermylidene complexes , which were fully characterized.3-Ge with H2O (one equiv.) was observed in THF even at 60 \u00b0C. The inertness of 3-Ge can be rationalized with the stronger metal-germylidyne Nb(d\u03c0) \u2192 GeR(\u03c0*) back bonding, which reduces the electrophilicity of the Ge center in 3-Ge, and increases in combination with the steric protection of the metal center by the tridentate tmps ligand the activation barrier for the H2O addition at the Nb PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe bond. In fact, a large excess of water (925 equiv.) and prolonged heating (3 h) was necessary to effectuate a full conversion of 3-Ge accompanied by a color change of the reaction solution from magenta to orange. IR monitoring of the reaction did not provide any evidence for the formation of the anticipated H2O addition products. Instead, a continuous decrease in intensity of the two \u03bd(CO) bands of 3-Ge was observed suggesting the formation of mainly CO-free products. Benzene extraction of the orange-brown solid obtained after solvent evaporation afforded a benzene soluble, pale-orange part containing mainly the germanediol Ge(ArMes)H(OH)2, as well as a benzene-insoluble brownish part. The unprecedented hydridogermanediol1H NMR spectroscopy. Its IR spectrum displays two \u03bd(OH) bands at 3600 and 3398 cm\u20131 and a characteristic \u03bd(Ge\u2013H) band at 2104 cm\u20131, the latter one appearing at a close position to that of GeBr2HMes (\u03bd(Ge\u2013H) = 2105 cm\u20131).1H NMR spectrum a distinctive doublet signal is observed for the Ge(OH)2 protons at \u03b4 = 0.91 ppm and a triplet signal for the Ge\u2013H functionality at \u03b4 = 5.61 ppm = 3.5 Hz) in the integral ratio of 2\u2009:\u20091. Notably, the Ge\u2013OH protons of the germanetriol Ge(ArTrip)(OH)3 have a similar chemical shift (\u03b4 = 0.77 ppm in CDCl3).29First studies reveal a marked difference in the reactivity of the niobium germylidyne complex 4]\u03bb = 465 nm) in the presence of one equivalent of Ge(ArMes)Cl. IR monitoring of the reaction revealed a quite selective decarbonylation leading to the chlorogermylidene complex 5-Ge, which after work-up was isolated as red-orange, air-sensitive crystals in 25% yield (5-Ge and to form the putative germylidyne complex cation + were not successful so far. For example, no reaction of 5-Ge with Na[B(ArF)4] 2) was observed in C6H5F at room temperature.Attempts were also undertaken to access cationic tetrylidyne complexes. For this purpose, (d(Ge\u2013Cl) = 232.2(1) pm),3)3Ni PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe(ArMes)Cl] (d(Ge\u2013Cl) = 230.03(8) pm)3)3Pd PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe(ArMes)Cl] (d(Ge\u2013Cl) = 227.3(1) pm),5-Ge provides a rationale for its inertness towards mild chloride abstraction reagents.The germylidene ligand adopts an upright conformation, with the Are (251.78 pm) of 5e (251.78 pm) of 55-Ge are fully consistent with its solid-state molecular structure. Thus, the IR spectrum of 5-Ge in THF displays three intense \u03bd(CO) absorption bands at 1980, 1910 and 1899 cm\u20131, as expected for a Nb(CO)3 fragment with local Cs symmetry, which are assigned to the A\u2032 , A\u2032 and A\u2032\u2032 symmetric (two COlat modes out-of-phase) CO stretching modes, respectively. The \u03bd(CO) absorption bands of 5-Ge are high-frequency shifted compared to those of [CpNb(CO)3THF] (\u03bd(CO) in THF = 1961, 1840 cm\u20131)3PEt3] (\u03bd(CO) in THF = 1953, 1850 cm\u20131),3N2] (\u03bd(CO) in n-heptane = 1991, 1905 cm\u20131)MesCl and the N2 ligand. The 1H and 13C{1H} NMR spectra also confirm the Cs symmetry of 5-Ge in solution. Rotation of the m-terphenyl substituent about the Ge\u2013Caryl bond occurs fast on the NMR time-scale at ambient temperature leading to an exchange of the two diastereotopic ortho and meta positions of the enantiotopic mesityl substituents. Therefore, only one singlet signal is observed in the 1H NMR spectrum of 5-Ge for the C2,6-bonded methyl groups and C3,5-bonded protons of the mesityl substituents, respectively.The solution IR and NMR spectra of 2-Si, 3-Ge and 3-Sn were carried out using cyclic voltammetry to elucidate the redox properties of these compounds. All complexes display a rich electrochemistry involving several electron-transfer steps of \u20132.612 mV and \u2013405 mV vs. the dmfc1+/0 redox couple (dmfc = decamethylferrocene), respectively ). Evidence that the redox process at E1/2 = \u2013405 mV involves a one electron oxidation of 3-Ge was provided by chemical means. Thus, no reaction of 3-Ge with the one-electron reducing agent cobaltocene (E1/2 of CoCp2 in DME = \u2013740 mV) was observed in fluorobenzene even at 70 \u00b0C, whereas an instantaneous oxidation of 3-Ge occurred upon treatment with one equivalent of [Fe(\u03b75-C5Me5)2][B(ArF)4] in fluorobenzene solution at \u201330 \u00b0C. Unfortunately, attempts to isolate the putative germylidyne complex radical cation [(\u03ba3-tmps)(CO)2Nb(GeArMes)]+ failed so far.36 Notably, the redox potential for the one-electron oxidation of 3-Ge is slightly lower than that of the molybdenum tetrylidyne complexes trans- verifying the presence of an electron-rich Nb center in 3-Ge.In comparison, the corresponding redox steps of 4)[Nb(CO)4(\u03ba2-tmps)] allowed to explore its reactivity towards a series of organotetrel(ii) halides, which lead to the isolation of the first niobium complexes featuring triple bonds with the elements Si, Ge and Sn. Photochemical CO substitution in [CpNb(CO)4] (Cp = \u03b75-C5H5) by Ge(ArMes)Cl afforded also the novel chlorogermylidene complex . The structural, spectroscopic and electrochemical data of the tetrylidyne complexes (2-Si), (3-Ge) and (3-Sn) suggest the presence of an electron-rich metal center that is engaged into strong metal (d\u03c0) \u2192 ER(\u03c0*) and metal (d\u03c0) \u2192 CO(\u03c0*) back bonding. Remarkably, one-electron oxidation and reduction of the germylidyne complex 3-Ge are electrochemically reversible.The synthesis of the tailor-made carbonyl-niobate (NMeSupplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Establishing the structure\u2013property relationship for multi-stimuli responsive mechanochromic materials based on charge transfer luminogens. i.e., cross packing), and subsequently, does not give rise to mechanochromism. The Hirshfeld surface analysis from a single crystal infers that non-covalent interactions are extremely important to yield mechanochromism under external force. Correlating all solid-state behavior with the molecular structure, we conclude that the synergistic effect between the twisting and conformational flexibility of donor moieties along with numerous non-covalent interactions gives rise to multi-stimuli responsive behaviors. Finally, the newly designed molecules are found to be highly emissive in solution and potentially applicable in fluorescence thermometer construction, lighting up cells, acid\u2013base sensors and rewritable devices.Prediction of multi-stimuli responsive behavior in newly developed luminogens is an appealing yet challenging puzzle, since no concrete design strategy has been developed so far. In this article, we demonstrate a potent strategy to gain a deep understanding of the structure\u2013property relationship to design multi-stimuli responsive mechanochromic materials. To achieve our goal, a variety of new isoindolinone core based charge transfer luminogens exhibiting aggregation-induced emission (AIE) have been prepared through C\u2013H bond activation using a cost-effective ruthenium (Ru) metal catalyzed one-pot synthetic strategy. We have shown that slight tuning of the donor moiety is found to be highly effective in controlling molecular packing and metastable energy states in solid states, and thus, optical properties and multi-stimuli responsive behaviors. The flexibility and twisting of donor moieties afford a loosely bound \u2018herringbone\u2019 packing, enabling reversible transformation under multiple mechanical stimuli. The cyclized derivative of the donor exhibits a completely different packing mode ( However, the PVS attached isoindolinone framework , which exhibits flexibility, and twisting nature (CNC angle 123.9\u00b0).i.e., carbazole is a well-known moiety having interesting material properties, such as charge transport, luminescence and thermal stability.According to the focus of this work, we have incorporated three common frameworks in each molecule: (1) D\u2013A framework, (2) twisted conformation of the donor moiety and (3) multiple non-covalent interaction sites. In addition, attention has been paid to the tuning of the donor moiety to control the flexibility and molecular packing. After a careful search, we have selected isoindolinone as the core moiety for this work. Isoindolinone, a typical planar, electron deficient molecule, consists of a fused phenyl and pyrrolidinone ring, and hence, it may be well suited for the \u03c0\u00b7\u00b7\u00b7\u03c0 stacking. A slight modification of the five-membered heterocyclic pyrrolidinone ring of isoindolinone has been performed by introducing a phenyl vinyl sulfone (PVS) group }2 (5.0 mol%), silver salt (AgSbF6 (20 mol%)), Cu(OAc)2, and H2O (2.0 equiv.) in acetic acid (AcOH) solution at 120 \u00b0C for 36 h (for details see ESIin situ synthetic route results in the cyclization product (Z)-3-((phenylsulfonyl)methylene)isoindolin-1-one (PMI) (3a) selectively as a Z-stereoisomer with high product yield (72%). In the same manner, substituted benzonitrile (2b\u2013d) efficiently undergoes an in situ cyclization reaction with PVS (4) resulting in (Z)-5-(diphenylamino)-3-((phenylsulfonyl)methylene)isoindolin-1-one (DPAPMI), (Z)-5-(9H-carbazol-9yl)-3-((phenylsulfonyl)methylene)isoindolin-1-one (CPMI), and (Z)-5-(dimethylamino)-3-((phenylsulfonyl)methylene)isoindolin-1-one (DMAPMI) (3b\u2013d) with 63%, 66% and 53% product yield, respectively catalyzed, step economical one-pot synthetic procedure using C\u2013H bond activation as a key step. To the best of our knowledge, this is the first ever report on synthesizing mechanoactive molecules based on Ru metal catalyzed C\u2013H bond activation. A brief representation of the synthetic scheme and mechanism is outlined in Scheme S2. In brieScheme S2. The funE) of donor substituted molecules narrows down compared to the parent PMI molecule. The calculated HOMO energies of DPAPMI, CPMI and DMAPMI are \u20135.73, \u20135.49 and \u20135.72 eV, respectively.To assess the viability of the molecular design and the electronic effect of donor substituents on the parent PMI molecule, we have conducted density functional theory (DFT) calculations at the B3LYP/6-31G level (see ESIf = 0.208) to assign the LE and CT emission peaks and at 505 nm (CT state), respectively in bulk THF. Upon gradual addition of water (poor solvent) into the THF, the emission becomes gradually weaker for both PMI and DMAPMI with a concomitant redshift of \u223c45 nm only for DMAPMI . The formation of nano-aggregates is confirmed by DLS, FE-SEM and AFM studies at higher water content like normal rigid fluorophores. Surprisingly, despite the presence of DMA substitution, DMAPMI shows ACQ nature in the aggregated state. This observation suggests that the smaller size of the DMA group is not sufficient enough to disturb the \u03c0\u00b7\u00b7\u00b7\u03c0 stacking interactions between the PMI moieties in the aggregated state. For DPAPMI and CPMI, probably the twisting conformations of the molecules do not allow them to be involved in effective stacking interactions in the aggregates. This is also evident from the crystal-induced enhanced (CIE) emission observed in the condensed state for both the compounds. Generally, the intramolecular rotations decrease the emission efficiency from the CT state in bulk solution medium, whereas in the CT process in the aggregate, the intramolecular rotation is restricted, thereby, causing an increase in the efficiency of CT emission. As a result, the emission from the CT state gets a boost by the aggregation induced emission (AIE) process for both DPAPMI and CPMI molecules.Z-conformation Z-conformer creates a one-dimensional planar sheet aided by multiple hydrogen bond scale\" fill=\"currentColor\" stroke=\"none\">O\u00b7\u00b7\u00b7H\u2013C) interactions in the symmetric repetitive fashion at 20 \u00b0C for all luminogens , the acceptor PMI part sits just above the DPA donor unit of the lower DPAPMI molecule \u03b82), while the other aryl group highly twists to \u223c77.78\u00b0 (\u03b83) with respect to the PMI core to fit into the crystalline lattice PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7H\u2013C (2.56 \u00c5 and 2.45 \u00c5), C\u2013H\u00b7\u00b7\u00b7\u03c0 (2.89 \u00c5), C\u2013H\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS , C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7\u03c0 (3.15 \u00c5), etc. , etc. . Moreove\u00c5), etc. taking a\u00c5), etc. . Emissio\u00c5), etc. , with tri.e., DMAPMI also displays a \u2018herringbone\u2019 packing like DPAPMI (\u03bc) value of \u223c9.41 D , and the partially double bond character of the C\u2013N bond (dC\u2013N = 1.366 \u00c5) between the donor (DMA) and the acceptor (PMI) moiety column in a symmetrical fashion scale\" fill=\"currentColor\" stroke=\"none\">S (2.631 \u00c5), C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7H\u2013C (2.464 \u00c5), S PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7\u03c0 (3.211 \u00c5 and 3.072 \u00c5), C\u2013H\u00b7\u00b7\u00b7H\u2013C (2.266 \u00c5), C\u2013H\u00b7\u00b7\u00b7\u03c0 (2.602 \u00c5), etc. , etc. and S4\u2020.\u20131) of stabilization. Interestingly, the C\u2013H\u00b7\u00b7\u00b7\u03c0 (% C\u00b7\u00b7\u00b7H) interaction contributed substantially in DPAPMI and DMAPMI luminogens, while the \u03c0\u00b7\u00b7\u00b7\u03c0 (% C\u00b7\u00b7\u00b7C) interaction has a minor contribution for all donor substituted luminogens to mechanochromism (for details see Note S2 in the ESIminogens and 7. Cgens (\u20131 ) and its\u03c1 values obtained for DPAPMI and DMAPMI are 7.2 and 5.86 respectively, inferring the herringbone packing for both these molecules. However, CPMI exhibits the lowest \u03c1 value of \u223c1.5 owing to its highest % of \u03c0\u00b7\u00b7\u00b7\u03c0 (% C\u00b7\u00b7\u00b7C in 3) despite the presence of multiple non-covalent interactions and a twisted carbazole ring. This is probably because CPMI contains four molecules per unit cell than CPMI but nearly the same void space as DPAPMI, as it contains flexible acyclic donor (DMA) substitution, like the DPAPMI molecule.The Fig. S13, while aSince some of our designed molecules have flexibility and void space, their solid state emission properties should depend on the alteration of molecular arrangements in response to external mechanical treatment (mechanochromism), temperature (thermochromism) and exposure to solvent (vapochromism). The pristine powder of the parent PMI molecule exhibits non-emissive behavior Fig. S14. Even af\u03c6pristine = 65 \u00b1 10%) having an intense peak at \u223c545 nm (CT) and a peeping peak at \u223c425 nm (LE) , although the peeping peak (LE state) remains nearly unaltered and \u223c77.78\u00b0 (\u03b83)) compared to the PMI core 3). Hence, grinding results in the release of twisting stress and rupturing of non-covalent interactions, which probably leads to more planarized individual DPAPMI molecules. As a result, the CT state is getting more stabilized due to the increased orbital overlap between the donor and the acceptor; hence, a redshift is observed under high grinding conditions compared to the pristine powder. Taking together the molecular conformation and emission color change upon stepwise grinding of DPAPMI, it is clearly understandable that two metastable states are generated due to the presence of two flexible aryl rings with different twisting angles in DPAPMI, the good solvent (DCM) molecule can access inside that accessible void space resulting in the rearrangement of the crystalline state of the luminogen molecules. The PXRD measurements reveal the transformation from the metastable semi-crystalline state to the crystalline state upon DCM treatment Fig. S21. However Fig. S21. Moreove Fig. S21. The sha Fig. S21. Most in Fig. S21. Once itIn modern technological applications, mechanochromic luminogens are mostly used as thin films, where they often stay as thin layers or in segregated states.3), which rarely allows the molecule to take different metastable energy states under mechanical stress and external stimuli. Thus, we conclude that it is not possible to disturb the architecture of highly stable \u2018cross mode\u2019 molecular arrangements of CPMI with the aid of any external stimulus and stress, and hence, CPMI is considered as a mechano-inactive molecule. It is also clear from PXRD data that the crystalline feature of CPMI before and after the grinding almost remains intact plays a significant role in designing a mechanochromic material, since the twisting angle of the donor is the only structural difference between them 3) owing to its cyclized donor unit and at the same time, it is also a mechano-inactive molecule. Thus, the mechano-inactivity of CPMI compared to its acyclic analogue DPAPMI suggests that a flexible donor unit is desirable to construct a mechanochromic material. Thirdly, Hirshfeld surface analysis of mechanochromic DPAPMI suggests that both C\u2013H\u00b7\u00b7\u00b7\u03c0 and \u03c0\u00b7\u00b7\u00b7\u03c0 interactions are important, however, it seems that the C\u2013H\u00b7\u00b7\u00b7\u03c0 interaction is dominant over the \u03c0\u00b7\u00b7\u00b7\u03c0 interaction to yield mechanochromism. To provide further insight, we have extensively mapped the Hirshfeld surface over the shape index and curvedness to get specifically the \u03c0\u00b7\u00b7\u00b7\u03c0 interaction region. Interestingly we have noticed that the mechanoactive DPAPMI molecule contains the \u03c0\u00b7\u00b7\u00b7\u03c0 interaction region in a small part residing at the central aryl ring with a minimum percentage of 4.1%, while other luminogens exhibit the \u03c0\u00b7\u00b7\u00b7\u03c0 interaction in a much wider region with higher percentage play major roles in mechanochromism. The importance of the twisting of the donor moiety in mechanochromism can be understood by looking at the molecular structure, packing style and Hirshfeld surface analysis of DPAPMI and DMAPMI. Hirshfeld surface analysis reveals nearly the same % C\u2013H\u00b7\u00b7\u00b7\u03c0 and % \u03c0\u00b7\u00b7\u00b7\u03c0 interactions for DPAPMI and DMAPMI . Moreovef = 0.003) upon excitation at 350 nm to the PMI core (A). Here, It is pertinent to mention that unlike other conventional ICT/TICT molecules, where the CT state is generated from the LE state, here the CT state can be generated by direct excitation at \u2265405 nm , the molecule probably reaches a high energy state, in which the diphenyl rings are not properly oriented to have an efficient charge transfer process. Now, the excited molecule can come back to the ground state by a radiative transition at 400\u2013430 nm from that higher energy state. Alternatively, it can also reach the other stabilized state having a CT character. When the molecule emits from this stabilized CT state, it shows a red-shifted emission (CT) compared to the LE state. The formation of the CT character has also been justified by a redshift and dramatic decrease in the emission intensity of the CT peak in highly polar solvents. When the solvent polarity is further increased (\u0394f > 0.22), the emission profile of DPAPMI consists of only a redshifted LE peak , the lower energy peak shows a gradual red shift with increment of solvent polarity (\u0394f > 0.014). In highly polar solvents (\u0394f > 0.31), the lower energy peak exhibits a usual redshift and higher energy emission appears as a shoulder. The high energy peak in n-heptane may be attributed to the pyramidal conformation of the \u2013N(CH3)2 group, which consists of a less charge character, as the \u2013N(CH3)2 group is out of resonance with the PMI moiety. This claim is further supported by the absorption spectrum, where the absorption for the CT peak (>400 nm) is very much less. The lower energy peak is attributed to the CT emission and this CT nature is further verified by the emission profile collected upon selective excitation of the charge transfer band, i.e., at 405 nm 2 and PMI stay in a perpendicular geometry, resulting in maximum charge transfer between donor and acceptor moieties.When two phenyl moieties are replaced by methyl groups, then the solvatochromic behavior dramatically changes. The methyl substituted derivative DMAPMI exhibits a low intensity peak at \u223c430 nm and 470 nm in non-polar solvents, like Fig. S25. Althoug Fig. S28. The exii.e., CPMI also exhibits unique solvatochromic behavior. CPMI shows an emission maximum at \u223c430 nm upon photo-excitation at 350 nm in non-polar solvent n-heptane , dual emission peaks appear in the emission profile, where the CT peak dominates the LE peak suggesting that LE and CT states are proximately closer in energy in this polarity region sensors and security ink. Moreover, highly emissive CPMI may be useful as a possible candidate for organic lasing materials and OLED fabrication. Here, we have demonstrated the applications of these newly developed luminogens in fluorescence thermometers, lighting up cells, rewritable media and acid\u2013base induced fluorescence switching media.Charge transfer (CT) luminogens having fluorescence switching ability between LE and ICT states by varying temperature are ideal for the construction of fluorescence thermometers, which are often used in industrial, atmospheric and deep-sea research, where conventional thermometers can't be used.Luminogens with aggregation-induced emission (AIE) have been recognized as potential candidates in recent years to light up a targeted part of the cell.To demonstrate rewritable media application, we have chosen DPAPMI, as this molecule only shows mechanoactivity. For this purpose, \u2018IISERP\u2019 has been written with a metal spatula on a glass substrate and the grinding induced emission color was monitored under UV irradiation . The wri3 vapor .Finally, dynamic fluorescence on\u2013off switching of DPAPMI and CPMI has been monitored under TFA and NH Fig. S30. Owing ti.e. CPMI) leads to a completely different packing mode (cross mode), which subsequently gives rise to the mechano-inactive properties of the luminogen. Surprisingly, although DMAPMI (having a dimethylamine group as a donor) exhibits a comparable packing style and non-covalent interactions to DPAPMI, it does not show mechanoactivity like its close analogue. Besides, Hirshfeld surface analysis specifically infers that non-covalent (C\u2013H\u00b7\u00b7\u00b7\u03c0 and \u03c0\u00b7\u00b7\u00b7\u03c0) interactions are also responsible for the observed mechanochromic properties. Considering all these aspects, we conclude that the loose molecular packing, conformational twisting and flexibility of the donor along with numerous non-covalent interactions are crucial for designing efficient CT mechanochromic luminogens. Moreover, these results establish the unique role of the flexible propeller-shaped donor unit in the self-reversible mechanochromism of CT luminogens. Although, we have chosen CT luminogens to establish the structure\u2013property relationship for designing multi-stimuli responsive materials, we believe that this strategy may also be beneficial to use as a general strategy to obtain mechanochromism. Finally, the designed molecules are found to be potentially applicable for fluorescence thermometer construction, lighting up cells (HEK 293), rewritable devices, acid\u2013base induced fluorescence switching, etc.This article provides a new avenue regarding the structure\u2013property relationship in order to design mechanochromic materials based on CT luminogens. To achieve our goal, we have developed a series of new isoindolinone based D\u2013A dyes using a one pot synthetic strategy through a Ru metal catalyzed C\u2013H bond activation approach. Slight tuning of the donor moiety is found to be very effective in controlling the molecular packing, and thus, the solid-state optical properties and mechanochromism as well. The crystal-induced emission enhancement (CIEE) effect is believed to be responsible for the observed high quantum yields of two of our synthesized luminogens, namely, DPAPMI and CPMI in the solid state. In DPAPMI (consisting of a diphenylamine group as a donor), the herringbone packing along with multiple non-covalent interactions and the flexible donor unit affords a loose herringbone molecular packing, enabling it to undergo reversible transformation under multiple stimuli. Cyclization of the donor unit (There are no conflicts to declare.Supplementary informationClick here for additional data file.Supplementary movieClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Rare and amphoteric intermediates, in situ generation: controlled reactivity in diverse cascade reactions, over 100 examples. C-substituted isocyanates, nitrogen-substituted isocyanates (N-isocyanates) are rare. Their high reactivity and amphoteric/ambident nature has prevented the scientific community from exploiting their synthetic potential. Recently, we have developed an in situ formation approach using a reversible equilibrium, which allows controlled generation and reactivity of N-isocyanates and prevents the dimerization that is typically observed with these intermediates. This blocked (masked) N-isocyanate approach enables the use of various N-isocyanate precursors to assemble heterocycles possessing the N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motif, which is often found in agrochemicals and pharmaceuticals. Cascade reactions for the rapid assembly of several valuable 5- and 6-membered heterocycles are reported, including amino-hydantoins, acyl-pyrazoles, acyl-phthalazinones and azauracils. Over 100 different compounds were synthesized using amino-, imino- and amido-substituted N-isocyanates, demonstrating their potential as powerful intermediates in heterocyclic synthesis. Their reactivity also enables access to unprecedented bicyclic derivatives and to substitution patterns of azauracils that are difficult to access using known methods, illustrating that controlled reactivity of N-isocyanates provides new disconnections, and a new tool to assemble complex N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO containing motifs.In contrast to normal Classical rearrangement reactions such as the Curtius, Schmidt, Lossen and Hoffman rearrangements are commonly used to form isocyanates in situ. In contrast, blocked (masked) isocyanates are simple precursors releasing isocyanates through a chemical equilibrium. Such blocked isocyanates\u2014typically generated from an isocyanate and a blocking group e.g. thermolysis, base, acid, and metal catalyzed formation).2The high reactivity of isocyanates is essential to many industrial processes but their promiscuous nature can be problematic. Therefore, for a variety of applications the use of C-substituted isocyanates.N-isocyanates) are a class of heterocumulene possessing comparable synthetic potential to C-substituted isocyanates. However, despite the early discovery of N-isocyanates,N-isocyanates results in difficult syntheses and a propensity for these intermediates to homodimerize or oligomerize, even at temperatures as low as \u201340 \u00b0C.4Isocyanates attached to heteroatoms are also known, but are less developed and used than normal N-isocyanates, and only explored their reactivity.N-isocyanates under UV photolysis conditions. Despite this pioneering work, the reaction conditions required to form these amphoteric intermediates, and their propensity to dimerize, severely limited their synthetic applications. To date, only a few reactions are reported using N-isocyanates or their blocked derivatives. After an extensive literature search, we only found 57 publications either forming, studying, using or suggesting the formation of N-isocyanates and N-isothiocyanates.N-isocyanate intermediates. In contrast, there are over 100\u2009000 publications and patents on C-isocyanates, and over 7000 on blocked C-isocyanates. The difference between the synthetic uses of C-isocyanates vs. N-isocyanates is inherently proportional, and highlights the need for a convenient procedure to form N-isocyanates and control their reactivity. Recently we have developed several blocked N-isocyanate precursors as part of our efforts on intra- and intermolecular alkene aminocarbonylation reactions (eqn (1)). These reactions involve N-isocyanates as key intermediates in a reaction sequence allowing the transformation of alkenes into valuable \u03b2-aminocarbonyl motifs. This work required the development of practical reagents: the use of hydrazide and hydrazone derivatives as N-isocyanate precursors emerged as a practical and general approach for these reactions. Most importantly, it allowed the desired concerted [3 + 2] alkene cycloaddition to occur in high yield, with little N-isocyanate dimerization or decomposition .C-isocyanate literature: (1) they appear to follow similar deblocking temperature trends; (2) base catalysis is also possible; (3) observations support a reversible equilibrium favoring the hydrazide and hydrazone starting materials.Much of the early work studied the formation of N-isocyanates, for example with alcohols, amines, and thiols as nucleophiles. This encouraged us to investigate the generation and reactivity of N-isocyanate precursors with simple nucleophiles. Gratifyingly, the substitution reactions proceeded efficiently under stoichiometric conditions using both hydrazonesN-isocyanates scale\" fill=\"currentColor\" stroke=\"none\">O motif in complex bioactive molecules, including several marketed agrochemicals and pharmaceuticals scale\" fill=\"currentColor\" stroke=\"none\">O containing substructures: fully or partially incorporated within a heterocycle, or in acyclic molecules.In parallel to this aminocarbonylation work, we noticed the paucity of simpler reactions of cyanates . A compaeuticals . There a PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motif in complex molecular scaffolds is highly desirable. However, it is a considerable challenge due to the diversity of motifs present and due to intrinsic chemoselectivity issues associated with hydrazine derivatives: the presence of two nitrogen atoms that can react and lead to different products.N-isocyanate chemistry and the diversity of N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motifs present, it was hypothesized that N-isocyanates could provide the missing link for a unified approach to N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO incorporation in heterocyclic chemistry; provided that their reactivity could be controlled enough to allow for new cascade reactions. This article constitutes a detailed account of our work toward this goal.Therefore, the development of strategies for the incorporation of the N\u2013N\u2013CN-isocyanates for the synthesis of heterocyclic molecules. In addition to previously communicated work toward saturated 5- and 6-membered azacycles and nitrogen-substituted hydantoins, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motif in several different orientations. N-Isocyanates were used to assemble 5- and 6-membered aromatic heterocycles including acyl-pyrazoles, acyl-phthalazinones and azauracils. This novel synthetic approach gives rise to substitution patterns that have otherwise been difficult or impossible to access, and allows the formation of new bicyclic heterocycles. With over 100 new compounds spanning 6 heterocyclic classes assembled using cascade reactions of amphoteric N-isocyanate intermediates, this article highlights that highly controlled reactivity is possible through the use of blocked (masked) N-isocyanate precursors.Herein, we discuss the first cascade reactions developed using amino-, imino- and amido-substituted N-isocyanate precursors could lead to efficient cascade reactions, we first targeted a reaction sequence in which generation of the N-isocyanate and reaction at its electrophilic carbon would occur first, followed by cyclization. It was expected that the substitution of nitrogen nucleophiles (e.g. amines) on N-isocyanates would be essentially irreversible. Building on our expertise in metal-free hydroamination reactions of hydrazine derivatives,N-isocyanate addition/Cope-type hydroamination cascade for the formation of saturated nitrogen heterocycles (eqn (2)), illustrated below using blocked N-isocyanate 1a.7To acquire proof of concept results to validate that the controlled reactivity of N-isocyanate precursors allowed the formation of several 5- and 6-membered nitrogen heterocycles incorporating one nitrogen atom (\u03b2N) of the amino-isocyanate in the desired heterocycle (in situ generated N-isocyanate to form the corresponding semi-carbazide (A), which then undergoes a Cope-type hydroamination to form the nitrogen heterocycle. Since isocyanate generation/addition occurred rapidly (ca. <10 minutes at 80 \u00b0C), the hydroamination reaction was rate limiting and the build-up of the unsaturated semi-carbazide A was observed when monitoring these reactions. However, upon heating at temperatures allowing hydroamination to occur, this cascade allowed the synthesis of semi-carbazide-based pyrrolidines , piperidines and piperazine (2c) using pyrrolidine as the nucleophilic amine. As expected, substitution was well tolerated on the alkenyl chain, and incorporation of a Thorpe\u2013Ingold bias was beneficial to achieve cyclization at a lower temperature (2d) or to reduce the time required for reaction completion (2e). Unfortunately, the incorporation of a small chiral centre on the alkenyl chain didn't result in any diastereoselecitivty . The cascade reaction also allowed cyclization via the more challenging hydroamination of an internal alkene (2h). A protected alcohol on the alkene chain was also tolerated (2g) and could allow further functionalization of the desired product. In addition to providing a cascade for the rapid assembly of molecular complexity, this data showed that semi-carbazide formation is essentially irreversible at temperatures up to 175 \u00b0C, a useful finding for the development of other cascade reactions.Gratifyingly, erocycle . This reN-isocyanate precursors in cascade reactions allows the formation of multiple hydroamination substrates from a common precursor, followed by intramolecular hydroamination events. This approach led to a diversity-oriented synthesis of pyrrolidines shown in Before developing other cascade reactions, we decided to address an important limitation of intramolecular hydroamination reactions.N-isocyanate addition/Cope-type hydroamination cascade ten different semi-carbazide-based pyrrolidines were synthesized from the same carbazate precursor , and piperidine derivatives (3c\u2013g) yielded the desired products in good to excellent yields. (S)-Prolinol was also a competent nucleophile but only showed modest diastereoselectivity. Product 3g bearing a bromine atom was also formed to highlight the potential of this metal-free method. The medicinally relevant 2-oxopiperazine demonstrated chemoselectivity for the most nucleophilic nitrogen, providing the desired heterocycle 3h in 85% yield. While both acyclic and cyclic secondary amines proved competent reaction partners, the result with primary amine 3j led to a modest, but preparatively useful yield. We attribute this difference of reactivity to a more challenging hydroamination step, due to the relative population of the E- and Z-conformers of the semi-carbazide.Using this rsor 1a, . Cyclic E hydrazide conformer is thermodynamically favoured.i.e. destabilizing interaction between R2 and \u03b2N in the E-conformer). Thus, the Z-conformer of these intermediates is thermodynamically favoured. Previous DFT studies suggest that the Z-conformer is the reactive conformer in Cope-type hydrohydrazidations , with an alkene present on the N-isocyanate substrate. To further develop cascade reactions of N-isocyanates, we were drawn to different cascade reactions in which cyclization would occur on a functional group (FG) present on the incoming nucleophile. Recently, we reported such a cascade reaction using \u03b1-amino esters to rapidly assemble N-substituted hydantoins would yield the 5-membered amino-hydantoin, while cyclization using the distal nitrogen (\u03b2N) would yield the 6-membered aza-diketopiperazine.o-esters .3N-substituted glycine esters . Alanine (5d), leucine (5e) and proline (5f) esters also cyclized in moderate to good yields. However, racemization occurred under these reaction conditions. In addition, we were pleased to observe the formation of a dihydrouracil ring (5g) in moderate yield using a N-benzyl \u03b2-aminoester as the reaction partner. Since the reaction was completely selective for the cyclization on the proximal nitrogen (\u03b1N), we decided to expand this study to include other N-isocyanate precursors. As indicated in the introduction, differences are expected and observed for the formation and reactivity of diverse N-isocyanates. In the context of this cascade reaction we wondered if blocked precursors of other amino-isocyanates , imino-isocyanates , and amido-isocyanates would be suitable reaction partners. The results using various N-isocyanate precursors are presented in N-alkyl glycine esters . We were also pleased that electron-rich and electron-poor aromatic carbazones both led to efficient product formation (7c\u2013e). We then surveyed the reactivity of bulky keto-carbazones: acetophenone, fluorenone and diisopropyl ketone-derived reagents afforded the cyclized products in good yields (7f\u2013h). A heteroaromatic carbazone also produced the desired heterocycle in good yield (7i). We also investigated the use of several N-glycine esters using the aldcarbazone derived from 4-methoxybenzaldehyde as a test substrate. The somewhat hindered N-isopropyl glycine ester afforded the desired hydantoin 7j in moderate yield. Functional groups such as nitriles (7k) and esters (7l) were tolerated on the nitrogen substituent. Even N-aryl glycine esters provided the N-aryl substituted amino-hydantoins. This indicates that electron-rich (7n), electron-neutral (7m) and even electron-poor (7o) anilines are competent nucleophiles under the reaction conditions. We then used this late-stage functionalization strategy to synthesize 5 azumolene analogues (7s\u2013w), without the use of chromatography (i.e. purified by filtration). Finally, we performed exploratory attempts toward three related cascades. These proved rewarding as we showed that: (1) imidazolidinone (7p) formation was possible if ring closure was achieved via 1,4-addition , using an \u03b1,\u03b2-unsaturated amino-ester as reagent; (2) an N-isothiocyanate precursor also engaged in a related cascade7q); (3) amide-substituted hydantoin (7r) could be synthesized using an amido-isocyanate precursor. Collectively, this data suggested that a variety of N-isocyanate precursors could engage in cascade reactions and display similar reactivity.Aliphatic carbazones afforded the desired hydantoins in excellent yields ).Considering the encouraging results obtained with the two reaction sequences presented above, we felt confident that we could expand this chemistry to different synthetic targets. The diversity of NCO (eqn ).4aq4i.e. NH2vs. NHR, previously) would result in a greater propensity to dimerize. We thus became interested in achieving even milder reactivity through the use of base catalysis. Previous studies conducted in the context of our alkene aminocarbonylation work showed that bases (e.g. Et3N) led to imino-isocyanate formation under milder conditions.C-isocyanatesN-isocyanate precursors, which could prove an asset for the development of other cascade reactions. Gratifyingly using 20 mol% of DBU with O-phenyl carbazate proved to be a convenient way of generating NH2\u2013NCO at room temperature. This was performed in the presence of a nucleophilic amine (1.1 equiv.) and afforded the desired semicarbazide products . Both primary and secondary benzylic amines proved competent reactants yielding the desired semi-carbazide in good to excellent yield. Propargylamine underwent the substitution reaction providing the propargylic semi-carbazide in modest yield . In general, both acyclic and cyclic secondary amines were tolerated . An ester functionality was also tolerated to yield the substituted piperidine based semi-carbazide . Finally, we were pleased to observe that double substitution could also be achieved using piperazine . Overall, the data shown in N-isocyanates could also benefit from base catalysis, with no detectable dimerization or oligomerization occurring under the reaction conditions. This new reactivity also provided a new route to semi-carbazides that could serve as building blocks for more complex derivatives.16Using this base catalysis procedure, we studied the reaction of different amines with O-phenyl carbazate could also engage in established cascade reactions. The advantage of this strategy is the ability to provide a free NH2 group for further derivatization reactions. We were quite pleased to see that the reaction with N-methyl glycine ethyl ester provided the NH2-substituted hydantoin in 91% yield on gram scale (eqn (5)). We then used the NH2 group to form pyrrole-substituted hydantoin 10b in 90% yield (eqn (6)). We were also able to synthesize an imidazolidinone derivative through a N-isocyanate cascade exploiting addition/cyclization by 1,4-addition (eqn (7)).A natural extension was to explore if N-isocyanates to form saturated heterocycles, amino-hydantoins and imidazolidinones, we sought to develop reaction cascades forming aromatic heterocyclic compounds possessing the N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motif. One could expect that the aromaticity of the product should prove advantageous by either facilitating the cyclization event or simply by forming stable products that do not interfere with the cascade reaction. However, this strategy also inherently implied the use of precursors at a higher oxidation state, with the unsaturations required for aromatization being present in their structure.Having established the potential of N-isocyanate precursor , morpholine and an ether-containing proline derivative yielding the desired heterocycle efficiently after heating for 18 h. Cascade reactions of secondary acyclic amines required prolonged heating (48 h) but yielded the corresponding phthalazinones in almost quantitative yields . Symmetrical and unsymmetrical amines afforded the desired products, but mixtures of semi-carbazide rotamers were observed by 1H NMR for the adducts of unsymmetrical amines. Unfortunately, all attempts to use primary amine nucleophiles resulted in the free N\u2013H phthalazinone. This observation strongly suggested that the desired product was formed, but then acted as a blocked C-isocyanate precursor by forming the isocyanate upon thermal extrusion of N\u2013H phthalazinone. Nevertheless, despite being limited to secondary amines this cascade provided us with the first cascade reaction forming a heteroaromatic core using N-isocyanate intermediates. The hydantoin and phthalazinone work showcased the cyclization potential of carbazone-derived N-isocyanates on esters.Pleasingly, optimization provided the desired cascade reaction, and carbamoyl-substituted phthalazinones were formed with several secondary amines at 100 \u00b0C. The reaction was tolerant of secondary cyclic amines such as pyrrolidine , morpholine (14b) and piperazine derivatives (14c and d) all cyclized in high yield. A halogen substituted aromatic group was tolerated in the reaction (14c), which highlights the possibility of further functionalization. Acyclic amines were also good reaction partners for the synthesis of acyl pyrazoles (14e\u2013l). Secondary amines yield the desired heteroaromatic core in high yield at room temperature. In contrast, primary amines required gentle heating at 50 \u00b0C but also provided the desired pyrazoles in good yield. Interestingly, benzylamine (14g) and furfurylamine (14j) did not require higher temperature to form the corresponding pyrazoles. Anilines could also be used as nucleophiles (14k). Given the low nucleophilicity of anilines, their use in this cascade reaction at 50 \u00b0C again supports the formation of a reactive N-isocyanate intermediate as the participating electrophile. The reaction could also be highly chemoselective for the most nucleophilic amine when using diamines, as demonstrated by the selective formation of adduct 14l. In parallel to efforts using different amines the cascade reaction was also performed with several carbazones, using pyrrolidine as a representative nucleophile (1) substituent on the outcome of the cascade reaction proved minimal. Products containing both small and large substituents were formed in high yield. The result obtained with the methyl-substituted carbazone was especially noteworthy. Indeed, both E and Z isomers of the carbazone starting material were present, favoring (ca. 9\u2009:\u20091 by 1H NMR) the E isomer which was not the appropriate configuration to cyclize. Thus the high yield supports that carbazone or imino-isocyanate isomerization occurred under the reaction conditions to form the Z-isomer required for cyclization on the alkyne. Alkyne substitution (R2) was also well tolerated and allows the formation of 1,3,5-trisubsituted pyrazoles under similar conditions (14p\u2013r). Finally, it should be noted that product formation for these 1,3,5-trisubtituted entries was observed at room temperature but that yields were typically higher at 50 \u00b0C, and that this cascade reaction is also scalable (eqn (8)).Gratifyingly, the y amines .22 A widy amines , top. Cyleophile , bottom.14 (R4 = H) are known to be blocked (masked) C-isocyanate precursors.3N-treated silica gel was also needed, suggesting that mildly acidic conditions could promote isocyanate formation. Overall, this data illustrated the usefulness of milder conditions for the development of new reaction cascades.It was imperative to use basic conditions for the formation of these acyl pyrazoles due to the labile nature of products formed with primary amines. Indeed, attempts to form acyl pyrazoles upon heating in the absence of base led to formation of free N\u2013H pyrazoles, since the acyl-pyrazoles products N-isocyanates could engage in cascade reactions forming 5-membered and 6-membered aromatic heterocycles, we sought to develop a cascade in which the amine nucleophile would be incorporated within the aromatic heterocycle formed. Strategically, this represented the most difficult cascade reaction targeted with N-isocyanates. After surveying potential scaffolds that could be obtained using this approach, the 6-azauracil ring system stood out as an excellent synthetic target due to reported biological activities7 receptor antagonists,1A receptor agonists.N-isocyanates to readily form semi-carbazones, we envisioned the use of carbazones derived from \u03b1-keto-esters.After showing that As illustrated in eqn (9), using this approach would provide the ability to incorporate the primary amine reagent at the 3 position of the azauracil compounds, upon cyclization of the incoming-nitrogen atom on the ester group of the parent carbazone.A under mild conditions. We believed that both E and Z isomers of A would be in equilibrium thus allowing for complete conversion to the stable aromatic product. However, we expected a strong conformational preference for this intermediate that would make the cyclization step difficult, noting that related cyclizations (R2 = H) typically only proceed at high temperatures.N-isocyanate addition products (semi-carbazone A) were observed at temperatures below 150 \u00b0C. However cyclization was typically observed around 150 \u00b0C, and further optimization showed that the desired azauracils formed in good yields upon heating at 175 \u00b0C. With these conditions in hand, we explored the scope of this cascade reaction: the results are displayed in Initially, we were confident about the ability to access semi-carbazone 15a (R1 = Me). We were pleased that a variety of primary amines, a hydrazine and a hydroxylamine could form azauracil products in moderate to high yield (35\u201385%). The reaction tolerated the use of hindered amines such as cyclohexylamine , of less nucleophilic amines such as anilines (16f), and of primary amines with a proximal electron-withdrawing group . While conducting the reaction with 4-bromoaniline, a crystalline product (16p) was obtained in 77% yield, and X-ray analysis secured the structural assignment , an ester (16v) and a tetrahydrofuryl group at the R1 position. These substitution patterns have medicinal relevance, for example product 16u is a C-linked nucleoside analogue. Finally, this cascade tolerated a diverse set of functional groups, including a free hydroxyl (16h), allyl (16o) and propargyl (16b) groups, a nitrile (16i), ethers (16t and 16u), an ester (16v), heteroaromatic rings such as thiophene (16x) and N\u2013H indole (16j), a free amide (16k), and aromatic bromides (16p) and fluorides (16e). Collectively, these results highlight that this cascade reaction has broad applicability to rapidly assemble 6-azauracil compounds.Fortunately, the cascade reaction forms a variety of substituted 6-azauracils effectively . First, via an intramolecular condensation, rather than form a bis-azauracil through cyclization of each nitrogen atom precipitated out of the reaction upon heating in acetonitrile, and cooling at the end of the reaction. In addition to encouraging results to form tricyclic systems using 1,2-aminoaniline (entries 1 and 2), we were pleased that 1,3-diaminopropanes yielded the corresponding 6,6-bicyclic compounds in good yields (entries 3\u20135). Surprisingly, this ring system had not been described in the literature, despite decades of work on the synthesis of purine analogues,26c further highlighting that cascade reactions of N-isocyanates can provide access to new heterocycles through simple reaction sequences.Encouragingly, several diamines engaged in a cascade reaction forming bicyclic or tricyclic systems. Relatively high yields (55\u201376%) were obtained considering that product formation involves N-isocyanates are powerful intermediates in heterocyclic chemistry. Our data shows that the use of N-isocyanates provides a versatile strategy to assemble heterocyclic compounds possessing N\u2013N\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO motifs, which are common in agrochemicals and pharmaceuticals. Various heterocycles could be assembled by taking advantage of the controlled reactivity provided by the use of blocked (masked) precursors that reversibly form the desired N-isocyanates upon heating or in the presence of catalytic bases such as DBU. This reactivity also demonstrated the ability of different N-isocyanates\u2014amino-, imino-, and amido-isocyanates\u2014to engage in cascade reactions and allowed a comparison of their reactivity. We also demonstrated the use of O-phenyl carbazate as a precursor for the simplest N-isocyanate, NH2\u2013NCO. Over 100 new heterocyclic products were formed using new reaction cascades, including new heterocycles and heterocyclic products with substitution patterns that are either difficult to prepare or that have not been reported in the literature. Beyond providing a new tool in heterocyclic chemistry, this work addresses an important void in the isocyanate literature: the lack of reactions exploiting the reactivity of N-isocyanates. This scarcity is surprising considering that the applications of C-substituted isocyanates are extremely well developed. We hope that this first thorough study on the synthetic uses of N-isocyanates will encourage others to develop reactions of N-isocyanates, also taking advantage of the blocked N-isocyanate approach to overcome dimerization. Efforts along these lines are ongoing in our laboratories and will be reported in due course.In summary, we have demonstrated that despite their amphoteric nature and reported propensity to dimerize, Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "For the first time, \u03b1-formyldiazoacetates (FDA), have been successfully applied for asymmetric olefin cyclopropanation via Co(ii)-based metalloradical catalysis. via Co(ii)-based metalloradical catalysis. The cobalt(ii) complex of the D2-symmetric chiral amidoporphyrin [Co] is an effective metalloradical catalyst that can activate \u03b1-formyldiazoacetates to cyclopropanate both aromatic and aliphatic olefins with varied electronic properties, affording the synthetically useful 1,1-cyclopropaneformylesters in high yields with both high diastereo- and enantioselectivity.For the first time, \u03b1-formyldiazoacetates have been successfully applied for the asymmetric cyclopropanation of alkenes As stable metalloradicals, cobalt(ii) complexes of the D2-symmetric chiral amidoporphyrins [Co(D2-Por*)] have emerged as a class of effective catalysts for asymmetric olefin cyclopropanation through a distinct radical process involving the catalytic generation of \u03b1-metalloalkyl radicals as the key intermediates (A).5 It has been suggested that the unusual capability of [Co(D2-Por*)] in activating acceptor/acceptor-substituted diazo reagents as well as regulating the reactivity and selectivity of the radical processes is further enhanced by the postulated double hydrogen-bonding interactions between the amide N\u2013H donors on the amidoporphyrin ligand and the two acceptors on the C-centered radical moiety -based metalloradical catalysis (Co(ii)-MRC), we were attracted to the possibility of accessing a new type of \u03b1-metalloalkyl radical bearing both \u03b1-formyl and \u03b1-alkoxycarbonyl functionalities from the metalloradical activation of \u03b1-formyldiazoacetates (FDA).6 Despite the fact that free \u03b1-formylalkyl radicals are scarce and prone to H-atom abstraction because of the weak aldehydic C\u2013H bonds,7 we reasoned that this type of \u03b1-metalloalkyl radical might be accessible on the basis of the combined effects of metal stabilization, double H-bonding interaction, and protection by the well-defined cavity of the ligand system (A). Assuming that the \u03b1-formyl-\u03b1-alkoxycarbonyl-\u03b1-Co(iii)-alkyl radicals (A) are capable of undergoing stereoselective radical addition with olefins, followed by the effective 3-exo-tet radical cyclization8 of the corresponding \u03b3-Co(iii)-alkyl radicals (B), we anticipated the potential development of a new catalytic process for the asymmetric synthesis of optically active cyclopropanes bearing both aldehyde and ester functionalities, which would be valuable for stereoselective organic synthesis . The development of this catalytic process apparently confronts the formidable challenges associated with the inherent low reactivity of the acceptor/acceptor-substituted diazo reagents and the incompatibility of the aldehyde functionality with existing catalytic systems.11 Recently, Fokin and coworkers developed a Rh2-catalyzed system for a highly asymmetric cyclopropanation with N-sulfonyl-1,2,3-triazoles for the production of cyclopropyl imines, which could be subsequently transformed into the corresponding formyl cyclopropane derivatives.12 While this offers a valuable alternative for the preparation of optically active formyl cyclopropanes, the direct synthesis via asymmetric cyclopropanation with \u03b1-formyl diazo reagents is an appealing process that remains to be developed. As a new application of Co(ii)-MRC, we herein wish to report the first catalytic system based on [Co(D2-Por*)] that is highly effective in activating FDA for asymmetric cyclopropanation. This asymmetric radical process is generally applicable for a broad scope of alkenes, offering a direct method for the high-yielding synthesis of 1,1-cyclopropaneformylesters with excellent control of the diastereo- and enantioselectivity. The products can be readily transformed into other chiral 1,1-bifunctionalized cyclopropanes and chiral dihydrofurans.The catalytic asymmetric cyclopropanation of alkenes with diazo reagents represents the most general approach for the stereoselective synthesis of optically active cyclopropanes.ii)-MRC (2(OAc)4] was indeed incompatible (entry 1), [Co(TPP)] only produced trace amounts of the corresponding cyclopropane from ethyl \u03b1-formyldiazoacetate (EFDA) (entry 2). Remarkably, when the Co(ii) complex of the D2h-symmetric achiral amidoporphyrin [Co(P1)]13 was used as the catalyst, the reaction proceeded successfully to form the desired (E)-1,1-cyclopropaneformylester in a 46% yield (entry 3). The dramatic difference in the catalytic activity between [Co(TPP)] and [Co(P1)] is in alignment with the hypothesized role of the double H-bonding interaction in activating EFDA and stabilizing the resulting intermediate A (P2)],14 the reactivity was further enhanced with the observation of a significant level of enantioselectivity (entry 4). Of the solvents examined, toluene was proven to be the medium of choice (entries 4\u20138). Lowering the reaction temperature further increased the enantioselectivity, but decreased the yield (entries 8\u201310). The diastereoselectivity was greatly improved when the bulkier tert-butyl \u03b1-formyldiazoacetate (t-BFDA) was used, affording cyclopropane 1a in a 78% yield with 95\u2009:\u20095 dr and 96% ee (entry 11). The product yield could be further improved to 84% by increasing the catalyst loading to 5 mol% while maintaining the high level of diastereo- and enantioselectivity (entry 12).Initial experiments were carried out with styrene as the model substrate to examine the suitability of FDA for the catalytic radical cyclopropanation by Co(ii)-MRC . While [ediate A . By switii)-based asymmetric radical cyclopropanation was investigated (P2)] with t-BFDA. For example, p- and m-alkyl styrenes were cyclopropanated to formylcyclopropanes 1b\u20131d in high yields with excellent diastereo- and enantioselectivity (entries 1\u20133). Halogenated (entries 4\u20136) and electron-deficient (entries 7 and 8) styrene derivatives could also undergo high-yielding cyclopropanation, producing 1e\u20131i with high stereoselectivities. The configurations of the two contiguous chiral centers in 1h were established as by X-ray crystal structural analysis (see ESI1j (entry 9). In addition, 1,1-disubstituted olefins such as \u03b1-methylstyrene could also be effectively employed, affording (E)-formylcyclopropane 1k in a 93% yield with remarkable control of both the diastereo- and enantioselectivity of the two newly-generated contiguous all-carbon quaternary stereogenic centers (entry 10). To demonstrate the functional group tolerance of the Co(ii)-based radical cyclopropanation, m-formylstyrene could be effectively cyclopropanated to cyclopropane 1l in a high yield with high diastereo- and enantioselectivity (entry 11). Notably, the two unprotected formyl groups were well tolerated by the metalloradical system. It is also worth mentioning that the Co(ii)-catalyzed cyclopropanation process could be scaled up ten-fold as demonstrated with the high-yielding synthesis of the cyclopropane 1d on a 1.0 mmol scale without affecting the excellent stereoselectivity (entry 3).Under the optimized conditions, the scope of this Co(stigated . Like sts see ESI. The cycii)-based radical cyclopropanation was further highlighted for its exceptional reactivity toward electron-deficient olefins, which are typically problematic substrates for catalytic systems involving electrophilic metallocarbene intermediates. For example, [Co(P2)] could catalyze the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC cyclopropanation of acrylonitrile with t-BFDA to form 1,1,2-cyclopropaneformylesternitrile 1m in a high yield with good enantioselectivity (entry 12), leaving the cyano group untouched. In marked contrast, when treated with Rh2-based catalyst, acrylonitrile was previously shown to react with the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond of FDA to form oxazoles.15 Other electron-deficient olefins such as ethyl and methyl acrylates could also be cyclopropanated to form the 1,1,2-cyclopropaneformyldiesters 1n and 1o in good yields with 96% ee and 97% ee, respectively, although with diminished control of diastereoselectivity (entries 13 and 14). The presence of three electron-withdrawing groups in the cyclopropanes 1m\u20131o renders them highly electrophilic, making them valuable intermediates for synthetic applications.16 Furthermore, aliphatic olefins, another class of challenging substrate for asymmetric cyclopropanation, could also be cyclopropanated by [Co(P2)] as exemplified by the high-yielding reaction of 1-octene under neat condition, forming 1p with high stereoselectivity (entry 15).The Co(E)-1a could be transformed into a trans-vinyl unit via the Horner\u2013Wadsworth\u2013Emmons reaction, affording (E)-1,1-cyclopropanevinylester 2 in a 78% yield with full retention of both the relative and absolute configurations (eqn (1)). When treated with Bestmann\u2013Ohira reagent, the formyl group in (E)-1a could be smoothly converted to a terminal alkyne functionality, resulting in chiral (E)-1,1-cyclopropaneethynylester 3 in a 70% yield without any diminishment of the original stereochemistry (eqn (2)). This transformation provides an alternative way to direct asymmetric cyclopropanation with \u03b1-ethynyldiazoacetates for chiral 1,1-cyclopropaneethynylesters.17 It is noted that \u03b1-ethynyldiazoacetates containing terminal alkyne units seem synthetically inaccessible. While the [Co(P2)]-catalyzed cyclopropanation with FDA generally forms (E)-cyclopropanes, the (Z)-diastereoisomers could be conveniently accessed through the stereospecific epimerization previously reported.5 As demonstrated with (E)-1a, treatment with 5 equivalents of NaI at room temperature resulted in the formation of (Z)-1a as the major diastereomer with only partial loss of the original optical purity (eqn (3)). Interestingly, when (E)-1g was treated with 10 equivalents of NaI at an elevated temperature, a ring-expansion involving the formyl group occurred instead, affording 2,3-dihydrofuran 4 in a 74% yield (eqn (4)). In the absence of any external chiral induction, the enantiopurity appeared to be largely retained during the rearrangement.As an initial exploration of applications, the formyl unit of the resulting chiral 1,1-cyclopropaneformylesters could be readily converted into other functional groups, forming various cyclopropane derivatives while retaining high enantiopurity. For example, the formyl group in (P2)] can effectively activate \u03b1-formyldiazoacetates (FDAs) for a highly asymmetric olefin cyclopropanation, without affecting the otherwise reactive aldehyde functionality. This represents the first application of \u03b1-formyldiazo reagents for metal-catalyzed asymmetric cyclopropanation. The Co(ii)-based radical cyclopropanation with FDA can be successfully applied to a broad scope of olefin substrates, permitting the direct synthesis of chiral 1,1-cyclopropaneformylesters in high yields with high diastereo- and enantioselectivity. Given that the resulting enantioenriched cyclopropanes contain two contiguous chiral centers in the ring structure, including one all-carbon quaternary stereogenic center bearing both aldehyde and ester functionalities, this new Co(ii)-based asymmetric radical cyclopropanation process should find wide applications in stereoselective organic synthesis.In summary, we have demonstrated that the metalloradical catalyst [Co("}
+{"text": "A multitechnique investigation of an evaporable vanadyl spin system with long-lived quantum coherence that self-assembles on gold. i.e. the logic units of quantum computers. These have to retain memory of their quantum state for a sufficiently long time allowing quantum operations to be performed. For molecular based spin qubits, strategies to increase phase coherence by removing nuclear spins are rather well developed, but it is now crucial to address the problem of the rapid increase of the spin\u2013lattice relaxation rate, T1\u20131, with increasing temperature that hampers their use at room-temperature. Herein, thanks to the combination of pulsed EPR spectroscopy and AC susceptometry we evidence that an evaporable vanadyl complex of formula VO(dpm)2, where dpm\u2013 is the anion of dipivaloylmethane, presents a combination of very promising features for potential application as molecular spin-qubit. The spin\u2013lattice relaxation time, T1, studied in detail through AC susceptometry, decreases slowly with increasing temperature and, more surprisingly, it is not accelerated by the application of an external field up to several Teslas. State-of-the art phase memory times for molecular spin systems in protiated environment are detected by pulsed EPR also in moderate dilution, with values of 2.7 \u03bcs at 5 K and 2.1 \u03bcs at 80 K. Low temperature scanning tunnel microscopy and X-ray photoelectron spectroscopy in situ investigations reveal that intact molecules sublimated in ultra-high vacuum spontaneously form an ordered monolayer on Au(111), opening the perspective of electric access to the quantum memory of ensembles of spin qubits that can be scaled down to the single molecule.Electronic spins in different environments are currently investigated as potential qubits, T1, which corresponds to the lifetime of a classical bit that can assume either the |0> or the |1> value; ii) the characteristic time in which the spin loses the memory of the phase of the superposition state in which it has been prepared. A lower estimation of this decoherence time, T2, can be extracted by the memory time, Tm, which is commonly measured with pulsed EPR or NMR: the ratio of Tm over the time necessary for an individual quantum operation has to be larger than 104 to allow for fault tolerant quantum computing.The realization of a quantum computer is expected to trigger a second revolution in information and communication technology,Tm, the research in this field has recently focused back on the simplest spin S = 1/2 systems constituted either by organic radicalsTm, in particular at high temperature, because there are no excited spin levels that can foster the magnetic relaxation when thermally populated. In these systems the interaction of the electronic spin with the nuclear spins is the most relevant source of decoherence. Outstanding results have very recently been obtained with vanadium(iv) ions assembled with nuclear spin-free ligands.2, Tm approaches one millisecond at low temperature,T2.T1, thus resulting in enhanced coherence time at high temperatureT1, are still poorly investigated.In the field of electron spin-based qubits nitrogen vacancies in diamondiv) by the combination of AC magnetic susceptometry to study spin\u2013lattice relaxation with pulsed EPR spectroscopy to characterize the spin coherence. The two techniques can in fact shed light on different contributions to the relaxation but their association is unprecedented in the search for potential spin-based qubits.In this study we have investigated the magnetic relaxation of a simple mononuclear complex of vanadium scale\" fill=\"currentColor\" stroke=\"none\">O bond is expected to increase the rigidity of the coordination sphere with a reduction of spin\u2013lattice relaxation efficiency. The presence of \u03b2-diketonate ligands in a neutral complex imparts a high volatility that can be exploited to deposit the molecule on surfaces. An unexpected long T1 over wide field and temperature ranges has been found to accompany Tm values that are among the longest ones observed in molecular species surrounded by spin active nuclei. The in situ morphological and spectroscopic characterization of a monolayer deposit of VO2(dpm)2 on Au(111) suggest that the molecules are intact on the surface, making these simple units potential candidates as molecular qubit individually addressable by scanning probe techniques.The vanadyl complex VO(dpm)2 was achieved according to an earlier reported procedure,2, prepared in the crystalline form and characterized by X-ray diffractometry scale\" fill=\"currentColor\" stroke=\"none\">O double bond (1.59 \u00c5 vs. an average of 1.964 \u00c5 for the V\u2013O single bonds). Deviations from tetragonal symmetry are already visible in the first coordination sphere in both bond lengths and bond angles. Given that the system crystallizes in the monoclinic P21 space group, two sets of molecules with the V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO directions forming an angle of 64.1\u00b0 are present in the crystal lattice. The strongly axial ligand field produced by the short V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond removes orbital degeneracy with the dxy orbital being the lowest in energy and the only one to be half occupied. Vanadyl systems are therefore well described by a spin S = 1/2 with slightly anisotropic g tensor close to the free electron value. The most abundant isotope of vanadium, 51V (99.75%), is characterized by I = 7/2 thus the S = 1/2 doublet is further split in 16 states by hyperfine interaction as schematized in The synthesis of crystalline VO(dpm)y see ESI, presenty see ESI with a s2, hereafter 1bulk, revealed no imaginary component of the susceptibility in zero static field down to the lowest investigated temperature (1.9 K). The application of a weak field induced however slow relaxation of the magnetization with the concomitant decrease of the real component \u03c7\u2032 and the appearance of a peak in \u03c7\u2032\u2032 component , evidencing also a gradual increase in the width of the distribution on lowering the temperature corresponds to the direct mechanism, dominating at low temperature, and the second one (b = 0.052 s\u20131 Kn\u2013) to a Raman-like, i.e. a multiphonon process involving virtual excited states.n = 3.22 \u00b1 0.02 is much smaller than the value of 9 or higher expected for the Raman process,34Maxima in i.e. up to 8.8 T, for three different temperatures, 5, 10, and 15 K. Notice that in this temperature range the direct process dominates as indicated by the almost linear dependence of \u03c4\u20131 on T. The corresponding relaxation times are reported in \u03c4 for weak applied field is followed by an almost flat region that extends up to ca. 4 T, followed by a rapid decrease at higher fields. Data of S = 1/2 systems. According to the seminal work done by de Vroomen et al. on the Cu2+ Tutton salt,To shed light on the mechanisms of magnetic relaxation the AC susceptibility was investigated in a wide field range, S = 1/2 should not be able to relax in zero field. The second term takes into account a sort of internal field whose origin can be either intramolecular (i.e. hyperfine interactions) or intermolecular (i.e. due to dipolar or exchange interactions). The latter is responsible for the efficient relaxation in zero field and presents, for the direct mechanism,The first term represents the direct mechanism between the two states split by the Zeeman energy, which is expected to vanish in zero field as a result of the Kramers theorem.S = 1/2 spin and reflects the fact that the larger is the Zeeman splitting between the states the higher is the density of phonons matching it. In the second one the d term represent the zero field relaxation rate, similar to the tunnelling rate in SMMs,f parameter takes into account the ability of the external field to suppress these mechanisms, while the e parameter, strongly dependent on the concentration of the spin centres, takes into account the field effects on the relaxation of interacting spins.c parameter for T = 5 K should be considered with caution because only a small fraction of the susceptibility is detected at such high fields. The field range where the relaxation remains slow is really remarkable, suggesting that the direct mechanism of relaxation is not very efficient.The first term is the typical field dependence of the direct process for a \u03b1 of the extended Debye formula 2 in favour of the dimeric one [TiO(dpm)2]2,1 in polystyrene with mass ratio 1\u2009:\u20095, 1PS1\u2009:\u20095, and 1\u2009:\u200910, 1PS1\u2009:\u200910, as well as a frozen 200 mM solution of 1 in a 2\u2009:\u20093 CH2Cl2\u2009:\u2009toluene mixture (1sol200 mM), were prepared and investigated by AC susceptometry vs. log(T) plot of \u03c4\u20131 \u221d Tn, with n = 1.49 \u00b1 0.04 for 1PS1\u2009:\u20095 and n = 1.86 \u00b1 0.04 for 1sol200 mM. Exponents larger than one for the direct mechanism are generally attributed to spin\u2013phonon bottleneck effects,\u03c4 of 1sol200 mM was also investigated at T = 5 K (see The long spin\u2013lattice relaxation time of VO(dpm)y Fig. S5. This watization : polymer 5 K see and reve1 (1sol1 mM) is shown in 1bulk, 1PS1\u2009:\u20095, 1PS1\u2009:\u200910, and 1sol200 mM spectra available in ESI Fig. S6The low temperature CW-EPR X-band spectrum of a frozen 1 mM solution of I = 7/2 nuclear spin of 51V: at the high and low field extreme region, peaks due to the parallel components of the hyperfine structure are observed, whereas in the centre the closely spaced perpendicular ones are evident, as schematized by the resonant fields in The spectra clearly show the features due to the anisotropic hyperfine coupling of the electron spin to the gx = 1.9880(2); gy = 1.9815(3); gz = 1.9490(2) and Ax = 0.0056(1) cm\u20131 (167.9 MHz); Ay = 0.0063(3) cm\u20131 (190.4 MHz); Az = 0.0170(2) cm\u20131 (509.6 MHz). These parameters are in the range previously reported for VO2+ \u03b2-diketonate-type derivativesSpectral simulations were performed1sol200 mM, 1sol1 mM, and 1PS1\u2009:\u200910 diluted samples (2 sample is experiencing the detected coherence.An echo-detected field-swept EPR spectrum (EDFS) was recorded using the standard Hahn sequence see ESI for 1sol samples . The obs1 as molecular qubit was performed by measuring the coherence time, Tm, as a function of temperature and field position for 1sol1 mM to reduce spin\u2013spin interactions. To maximize the observed echo the temperature dependence of Tm has been investigated on the so-called powder like line evidenced by an arrow in Determination of the potential applicability of diluted samples of The echo decay traces were theTm values ,T1 between 5 K and 110 K in 1sol1 mM, for which the AC susceptibility technique does not have the necessary sensitivity.Since earlier studies revealed strong correlation between the spin\u2013lattice relaxation time \u03b21 being in the range 0.6\u20130.9 in the investigated temperature range 2 in H2O:glycerol solution,T1 are observed at low temperature (50 ms at 4 K) and on heating T1 tends toward Tm (6 \u03bcs at 110 K). Interestingly, a Tn\u2013 dependence with n = 3.2 \u00b1 0.2 is observed above 40 K, with a gradual decrease of n at lower temperatures, in agreement with AC susceptibility results.Given the large range of relaxation times two different experimental procedures were applied: at low temperature (5\u201360 K) the echo saturation by fast repetition, suitable for long relaxation times1sol200 mM by pulsed EPR: the obtained results are consistent with those obtained by AC susceptibility deposit assembled on the Au(111) surface. A complete in situ X-ray photoelectron spectroscopy (XPS) and low temperature scanning tunnelling microscopy (STM) characterization was carried out, while the stability of the sample toward oxidation was investigated by exposing a thick film to air. T = 30 K for sub-ML coverage. As observed for other complexes with dpm\u2013 ligands,The high volatility of VO(dpm)2. By increasing the deposition time full coverage was achieved: regularly packed molecules still revealing the herringbone structure underneath were found scale\" fill=\"currentColor\" stroke=\"none\">OV), in good agreement with what observed for vanadyl phthalocyanine, VOPc, on Ag(111),\u2013 ligands scale\" fill=\"currentColor\" stroke=\"none\">OC). The ratio of the area of the two peaks is close to 1\u2009:\u20094, as expected for the stoichiometry of the molecule, thus confirming the integrity of the complex on surface. An analogous analysis allows to distinguish three components contributing to the C 1s region: the carbonylic carbon (287.2 eV), methyl carbon (285.4 eV) and the third one regrouping the remaining carbons .The observed broad O 1s peak around 532 eV was reproduced by considering two components. The smaller one at 531.3 eV was attributed to the oxygen of the vanadyl group scale\" fill=\"currentColor\" stroke=\"none\">OV 1s \u2013 V 2p3/2) of 14.9 eV which well compares with that observed in VOPc monolayer and multilayers scale\" fill=\"currentColor\" stroke=\"none\">OV 1s \u2013 V 2p3/2) = 14.6 eV).Even more interestingly the vanadium photoelectron peaks allowed to provide specific hints on the oxidation state of this element and thus on possible interaction with the metal surface. The V 2p2 molecules can be deposited intact on the surface and features a weak interaction with the gold substrate as the only occupied d orbital, dxy, is expected to lie flat with limited overlap with the substrate orbitals. A similar scenario was observed for copper(ii)phthalocyanine molecules that are known to retain their unpaired electron in the dx2\u2013y2 orbital.S = 1/2 of VIV compared to thicker films. It is therefore reasonable to envisage that VO(dpm)2 molecules retain their paramagnetic nature when in contact with the gold substrate. This system represents therefore an appealing alternative to the use of N-donors phthalocyanine- and porphyrin-based systems for deposition on surfaces, though VO(dpm)2 films resulted somehow instable in air: ex situ prepared thick films of about 150 nm showed a partial surface oxidation as suggested by the decrease in the scale\" fill=\"currentColor\" stroke=\"none\">OV 1s \u2013 V 2p3/2)) value accompanied by a progressive shift of the V 2p peak et al.S = 3/2 of CoII in Co(acac)2(H2O)2.S = 1/2 due to time reversal symmetry. VO(dpm)2 corresponds exactly to the hyperfine-split S = 1/2 model recently developedI = 7/2 gives origin to two sets of states characterized by F = |S \u00b1 I| with multiplicity 9 and 7, respectively, as can be observed in F = 4 and F = 3 states, which are however further split by the anisotropic components of the hyperfine tensor (see eqn (4)). The application of a weak static field has a different effect when applied along the molecular z direction, the one of largest hyperfine interaction corresponding to the V PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond direction, or perpendicular to it, as also indicated in the eigenvectors composition 2pseudo-spin S = 1/2 system, some striking quantitative differences are evident. The first one is that the relaxation time remains long over a wide field range, ca. 30 times larger in VO(dpm)2 compared to the CoII derivative. At 5 K, where the relaxation is still governed by the direct mechanism, the relaxation rate starts to grow above 3 T, to be compared to the drastic 0.1 T upturn observed for CoII at 1.8 K.II spins2 is unprecedented. This is extremely appealing for technological applications as it allows to exploit higher frequencies to coherently manipulate the spins, e.g. at W-band, corresponding to 95 GHz, with significant improvement of sensitivity. Moreover, working at W-band was also shown to increase Tm in samples of Yb3+ diluted in CaWO4, though at the same time the larger field was found to reduce T1. This serious drawback of the use of high frequencies is not expected for VO(dpm)2.55If similar features were already observed in the Co(acac)T1 of VO(dpm)2 remains long over a wide temperature range. For instance, a relaxation time of 2 ms is observed at 6 K for diluted Co(acac)2(H2O)2 but at temperatures as high as 40 K in concentrated VO(dpm)2. The anomaly arises from the small exponent of the Tn dependence of the Raman-like mechanism of relaxation. Such low exponents are relatively common for S = 1/2 states with small orbital contributions comprising light elements and have been associated to the soft character of the molecular lattices.The origin of the striking difference between the two compounds can be associated to the reduced efficiency of the direct mechanism of relaxation, which relies on the spin\u2013phonon coupling. The latter is mediated by the spin\u2013orbit coupling, which is significantly lower for such a light transition metal as vanadium. As a result, Tm values observed for a frozen solution of VO(dpm)2 are slightly longer \u2013 in the whole investigated temperature range \u2013 than those reported for a dispersion in protiated solvents at the same concentration of a vanadium complex with nuclear-spin free ligands:2 diluted in deuterated solvents. A substantially unchanged Tm was detected . We must stress that the processability and the surface stability of this \u03b2-diketonate complex are comparable to those of metal porphyrins, without the drawback of introducing 14N magnetic nuclei. This is not only relevant for reducing the efficiency of decoherence; as suggested by Freedman et al.,g is practically zero and therefore are weakly affected by changes in the local field. Enhanced coherence time for these clock transitions have been recently observed in Bi doped silicon enriched in 29Si nuclei.2 for which clock transitions are expected at fields where the magnetization dynamics is already rather slow.The observed decoherence times for VO(dpm)Tm of VO(dpm)2 is compared with relaxation times for a copper dithiolate complex with deuterated PPh4+ cation reported by van Slageren et al.et al., is expected to increase Tm of VO(dpm)2 as well as its T1.On the other hand, when T1, in terms of both temperature and field dependence, is mandatory for the realization of molecular spin qubits that can be operated at room temperature. AC susceptibility gives easily access to the field dependence of T1, in contrast to EPR, which relies on the resonance condition. Though T1 extracted with the two techniques are exactly the same only in the case of a S = 1/2 with no hyperfine splitting, a close relation exists also for systems with more than two levels. The simple molecule we have picked up with this approach, though not yet optimized for coherent manipulation of the spin state, presents state-of-the-art phase memory times combined with additional interesting features. The spin\u2013lattice relaxation remains slow even in strong fields, allowing the use of higher frequencies for coherent spin manipulation without losses in performances.We have shown here that a more rational search for potential qubits can significantly benefit from the combination of AC susceptometry with pulsed EPR techniques. This multitechnique approach is of particular relevance to define synthetic strategies because the optimization of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond needs to be further investigated by extending the approach developed here to other and more promising systems.Ab initio modellization of the spin relaxation could also help to identify which structural features can favour long T1, and consequently long Tm, at high temperature.A particularly low efficient spin\u2013phonon coupling appears to be at the basis of this behaviour and the potentially positive role played by the strong Vg-factors.61Even if the crucial aspect of qubits entanglement has not been addressed in this work it can be easily achieved through connection of \u03b2-diketonate pockets in more complex architectures.2 molecules, retaining their paramagnetic nature thanks to the reduced interaction of the orbital carrying the unpaired electron with the substrate. Metallic nanostructures can be easily decorated with a monolayer of ordered VO(dpm)2 molecules, allowing to investigate the response of an ensemble of identical molecular qubits, whose size can be easily controlled by lithographic exposure of the metallic substrate. Thin films of VO(dpm)2 could be evaporated directly on a \u03bc-SQUID to detect by AC susceptometry the effects of surface confinement on the dynamics of the magnetization, as already done on SMMs.2 could be also a good candidate to investigate quantum coherence at the single molecule level thanks to the recently developed approach based on spin-polarized scanning tunnelling microscopy, employed at very low temperature on single Fe atoms deposited on a MgO surface.63Of great relevance is the possibility to obtain monolayers of ordered arrays of intact VO(dpm)T2 in nuclear spin free environments with the possibility to control the spin\u2013lattice relaxation through a rational synthetic design is foreseen to boost the interest for molecular spin systems as potential qubits.Combining the optimization of Supplementary informationClick here for additional data file."}
+{"text": "The M-(\u03b72-BMn) complex [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(Cl)(tBu)Au(PPh3)}] (2) can be functionalized via halide substitution reactions to afford isostructural complexes [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(R)(tBu)Au(PPh3)}] . 2-BMn) complex [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(Cl)(tBu)Au(PPh3)}] (2) can be functionalized via halide substitution reactions to afford isostructural complexes [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(R)(tBu)Au(PPh3)}] . It also reacts with coinage metal complexes [MCl(PPh3)] in the presence of halide abstraction reagents to afford borylene-bridged heteromultinuclear complexes [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc2-B(tBu)}2M][BArx4] 2). Experimental characterization as well as computational studies revealed that these complexes are best viewed as transition metal borylene complexes side-on coordinated to monovalent coinage metal cations, thus representing the first boron analogs of Stone's alkylidyne-bridged multinuclear complexes.The M-(\u03b7 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN(SiMe3)2.These complexes possess a distinctly different structural architecture to the relatively small library of multi- and di-nuclear borylene complexes, all of which have been described in terms of [BR] bridging. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB(R)] as a ligand, which reveals that it serves as a side-on \u03c0-ligand that resembles classical metal olefin or alkyne \u03c0-interactions and thus also their isolobal alkylidyne complexes (OC)2Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tBtBu] (1) reacted with gold(i) chloride complexes to form heterodinuclear complexes [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(Cl)(tBu)}Au(L)] 2}), which are best viewed as \u03c3-coordinated transition metal haloboryl complexes.3) affords the best yield and therefore complex 2 has been used for subsequent studies , the reaction mixture afforded orange crystals 5a and 5b in moderate yields after cooling at \u201330 \u00b0C overnight. The 11B NMR spectrum of 5a showed a broad singlet at 121 ppm, slightly downfield-shifted from that observed for 2 (108 ppm). The chemical shift of the 11B NMR signal of 5b is not significantly different from that of its precursor, lying at 107 ppm. Both signals of 5a and 5b fall within the range expected for transition metal boryl complexes,Intuitively, the reactive boron\u2013halogen bond in haloboryl complexes should be relatively straightforward to functionalize, yet in reality, examples of such a reaction remain rare. Most of these transformations introduce \u03c0-donating \u2013OR and \u2013NReactions . Upon ad5a and 5b to be [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(R)(tBu)}Au(PPh3)] , which are isostructural to 2, apart from the second anionic substituent at boron.5a and 5b are 2.156(3) and 2.157(9) \u00c5, respectively, very similar to each other and both slightly longer than that observed in 2 (2.126(9) \u00c5). Concurrently, the Au\u2013B bond also elongates slightly upon halide replacement, exhibiting Au\u2013B distances of 2.356(2) and 2.326(8) \u00c5 for 5a and 5b, respectively, compared to 2.303(9) \u00c5 of 2. The Mn\u2013Au distances (5a: 2.548(1) \u00c5; 5b: 2.547(2) \u00c5), on the other hand, are barely altered by halide substitution (cf. 2.553(1) \u00c5). As observed in 2, the boron centers of 5a and 5b adopt an almost planar geometry when the gold atom is disregarded .Single-crystal X-ray diffraction studies have confirmed the structures of 2 with [NBu4][NCS] led to a less selective reaction, from which a small amount of pale orange crystals (5c) were isolated from a complex mixture. Single-crystal X-ray diffraction studies confirmed the structure of this compound to be [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(NCS)(tBu)}Au(PPh3)] (5c), isostructural to 5a and 5b with an unusual boron-bound isothiocyanate substituent (5c are 2.113(5) \u00c5 and 2.320(5) \u00c5, noticeably shorter than those observed in 5a and 5b. The B\u2013N distance of 1.532(7) \u00c5 falls between those established for aminoboranes R2B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR2 and amine-borane adducts R3B\u2013NR3, indicating significant \u03c0-donation from the nitrogen to boron. This is also reflected by the linear geometry (B\u2013N\u2013C 177.0(5)\u00b0 and N\u2013C\u2013S 178.3(5)\u00b0) of the BNCS moiety. To the best of our knowledge, complex 5c represents the first structurally characterized example of a transition metal complex bearing an isothiocyanate\u2013substituted boryl ligand. The 11B NMR spectrum of 5c showed a more upfield-shifted singlet at 95 ppm, which also falls within the range expected for transition metal boryl complexes.Similar reactions of stituent .29 The M3 shows similar reactivity towards nucleophiles. However, the expected products [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(R)(tBu)}Au(PCy3)] of the analogous reactions were in all cases found to be in equilibrium with the parent borylene complex 1 and [AuR(PCy3)] in the reaction mixtures, and thus could not be isolated. This liability of the [AuR(PCy3)] moiety in the [(\u03b75-C5H5)(OC)2Mn{\u03bc-B(Cl)(tBu)}\u2013Au(PCy3)] system was confirmed from the reaction of 3 with the platinum (0) complex [Pt(PCy3)2] and the isocyanide ligand CNMes* (OC)2Mn{\u03bc-CO}{\u03bc-B(tBu)}Pt(PCy3)] (6)5-C5H5)(Mes*NC)(OC)Mn{(CO)B(tBu)(CNMes*)}] (7)3)] (1 and the gold acetylide complex [Au(CCPh)(PPh3)], which afforded the acetylide\u2013borylene coupling product 5b in 61% yield (34Complex ] (7)3)] . These o1% yield . Gold ac2 was also probed with sodium tetraarylborates for halide abstraction reactions. Upon addition of Na[BArCl4] to a toluene solution of 2, with shaking, a cloudy orange solution was formed. After filtration and cooling at \u201330 \u00b0C over a week, the reaction mixture afforded orange crystals, which are insoluble in hexane, benzene or toluene, and moderately soluble in dichloromethane. The 11B NMR spectrum obtained from a CD2Cl2 solution showed a broad signal at 144 ppm and a sharp singlet at \u20137.04 ppm. The former is identical to that of the free borylene complex 1 (144 ppm), and the latter is attributed to the boron nuclei of the tetraarylborate counterion.Complex 5-C5H5)(OC)2Mn}{\u03bc-B(tBu)}Au(PPh3)][BArCl4] (ArCl = C6H3Cl2), single-crystal X-ray diffraction studies revealed the structure of these orange crystals to be [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc-B(tBu)}2Au][BArCl4] ([8][BArCl4]), comprising two borylene moieties coordinated to a single gold(i) cation (2\u20135 (2.110\u20132.157 \u00c5), and only marginally longer than the parent borylene complex 1 (1.810(9) \u00c5). This suggests that the Mn\u2013B interaction of [8]+ retains most of its multiple bond character while coordinated to the gold(i) cation, as also suggested by its 11B NMR signal. The Au\u2013Mn distance of 2.619(1) \u00c5, is noticeably longer than those observed for 5a\u2013c (2.548\u20132.555 \u00c5), however, shorter than that observed in the neutral trimetallic gold boride complex [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc-B(Au(PPh3))}] (2.651(4) \u00c5), in which the Au(PPh3) moiety migrates between the two Mn\u2013B parts rapidly even at \u201390 \u00b0C.5a\u2013c (2.320\u20132.356 \u00c5). The angle between the two Mn\u2013B\u2013Au planes is 72.8\u00b0.Instead of the expected product [{(\u03b7) cation . The Mn\u20138][BArCl4] was somewhat puzzling. Therefore, the reaction was repeated with an alternative halide abstracting agent Na[BArF4] (ArF = C6H3(CF3)2). From this reaction, besides the analogous product [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc-B(tBu)}2Au][BArF4] 2), crystals of another product were also obtained, which was found to be [Au(PPh3)2][BArF4] (12) by X-ray crystallography. From this we proposed that the formation of [8][BArx4] (Arx = ArCl and ArF) proceeds via the expected cationic halide abstraction intermediate, followed by a ligand exchange, a route that has been reported for the analogous alkylidyne complexes ] in toluene led to formation of an inseparable mixture. However, in the presence of a stoichiometric amount of the halide abstracting agent Na[BArCl4], a mixture of 2 equiv. of 1 with [AgCl(PPh3)] led to formation of a mixture of colorless and orange crystals after being stored at \u201330 \u00b0C for 3\u20134 days. These crystals are extremely light-sensitive and thermally-unstable. Even in the strict argon atmosphere of a glovebox, black colloidal silver was observed inside and on the surface of crystals after being stored at room temperature. X-ray crystallographic studies revealed that this crystal mixture contained both the intended silver(i) product [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc-B(tBu)}2Ag][BArCl4] ([9][BArCl4]) and the by-product [Ag(PPh3)3][BArCl4] was found to be possible in the presence of a non-coordinating counterion. The reaction of 1 and Ag[BArCl4] led to clean formation of [9][BArCl4] in 90% yield of [9]+ were found in both coplanar and staggered geometries from different crystal samples. This suggests that the energy difference between these two geometries is insignificant, which has been confirmed by computations (vide infra). In the staggered form, the angle between the two Ag\u2013B\u2013Mn planes is 67.8(8)\u00b0.The solid-state structures of [1 with [CuCl(PPh3)] and sodium tetraarylborate Na[BArCl4] in toluene or fluorobenzene were less selective compared to those involving silver(i) complexes. In both solvents, small yields of crystals were isolated. X-ray crystallography revealed the solid state structure of these crystals to be [11][BArCl4], where [11]+ consists of two metal\u2013borylene-coordinated copper moieties connected by a [MnH(\u03b75-C5H5)(CO)2] fragment, which makes it a diamagnetic compound (CO)3] was added to the reaction of 1 with [CuCl(PPh3)] and Na[BArCl4] in toluene. This reaction afforded low yields of orange crystals, which was confirmed to be the originally-intended product [{(\u03b75-C5H5)(OC)2Mn}2{\u03bc-B(tBu)}2Cu][BArCl4] ([10][BArCl4]) by X-ray crystallography. Crystals of 10 and 11 are sparingly soluble in benzene and toluene. Although moderately soluble in dichloromethane, the solutions decompose within a minute at room temperature. Due to this extreme instability and low yields of the products, no useful NMR data could be obtained. Subsequently both [10][BArCl4] and [11][BArCl4] could only be characterized by X-ray crystallography \u00c5), [10]+ (1.850(6) \u00c5 and 1.857(5) \u00c5) and [11]+ (1.865(4) \u00c5) are only slightly longer than that of the terminal borylene complex 1 (1.810(9) \u00c5) and much shorter than a Mn\u2013B single bond.8]+\u2013[11]+ range from 156.4\u00b0 to 162.7\u00b0 (cf. in 1: 174.3\u00b0). These structural features are in contrast to all other homo- and hetero-dinuclear bridging borylenes containing the same [MnBR] fragment, in which the Mn\u2013B distances are considerably longer (1.91\u20132.02 \u00c5) and the Mn\u2013B\u2013C angles are significantly more acute (135.2\u2013145.8\u00b0).5-C5H5)(OC)2Mn(\u03bc-BtBu)] moiety, (i.e. the borylene moiety is more semi-bridging), which is consistent with the 11B NMR data. Furthermore, The Mn\u2013M distances of [9]+ (M = Ag) and [10]+ (M = Cu) are 2.683(1) \u00c5 and 2.447(1) \u00c5 respectively (cf. Mn\u2013Au 2.619(1) \u00c5 in [8]+), consistent with the trend of the atomic radii of Au, Ag and Cu.8]+, [9]+, and [10]+ are listed in 2Au(\u03bc-CC6H4Me-4)2(CO)4(\u03b7-C5H5)2]+] (62\u00b0).41The important bond distances angles of the cations +\u2013[10]+ corresponded to the observed non-planar geometry of the M(MnB)2 cores. The optimization and subsequent harmonic frequency calculations of the coplanar Ci structure observed for [9]+ showed it to be a transition state on the energy hypersurface. The energy difference between the co-planar and staggered form is very small . This is presumably due to the closed-shell d10 centre of Ag+, the geometry of which is not dictated by crystal field effects.To gain more insight into the bonding of complexes ns orbital of coinage metal, which leads to its smaller overlap with the \u03c0-type orbital of the borylene unit. For the backbonding, the coinage metal delivers electrons from its (n \u2013 1)d orbital to the empty \u03c0* orbital of borylene. In the case of copper the 3s,p and 3d orbitals have similar size, thus the 3d \u2192 \u03c0* interaction is weakened by repulsion with the 3s,p orbitals, which have symmetries incompatible with this interaction. When changing to Ag, the orthogonality of the 4d and 3d orbitals causes an increase of the radii of the 4d orbitals. The spatial separation of the 4s,p and the 4d orbitals is larger and thus the repulsion is smaller, while the orbital overlap is better. In the case of Au, the relativistic contraction additionally amplifies this effect and therefore results in the strongest backdonation.43No localized two-center, two-electron bonds between the central metal and the borylene ligands have been found using the Natural Bond Orbital (NBO) method. However, strong donor\u2013acceptor interactions have been found using the second-order perturbation analysis. The dominating interactions are the donations from the Mn\u2013B bonds to a low-populated coinage-metal-centred orbital. The backdonation to the borylene from the coinage metals is an order of magnitude weaker. Computations carried out employing gross populations of fragment orbitals have shown that charge donation from the borylene ligands to the coinage metals decreases from Cu to Au , whereas the backdonation grows from Cu to Au . The first of these effects can be ascribed to the increasing size of the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB bond and large Mn\u2013B\u2013R angle). In turn, the semibridging geometry and the slight preference of the staggered geometry may play a role in maximising backdonation from the coinage metal cations to the borylene in a similar way to the bisphosphine gold(i) system [(DPCb)AuCO]+ (DPCb = o-carborane diphosphines) reported by Amgoune, Bourissou and co-workers. It has been observed that ligands in Au(i) complexes that deviate from linear geometry cause the energies of the 5d orbitals to rise, which strengthens the backdonation from the Au(i) center to the ligand (CO).+, alkylidynes also exhibit larger M\u2013\u03bcC\u2013R angles and shorter M\u2013\u03bcC bonds than bridging alkylidynes with most other metals, where the \u03bcCR vector is closer to perpendicular to the M\u2013Au bondThe weak backdonation from the coinage metal cations to borylene may be responsible for its semibridging geometry and preserved strong borylene character scale\" fill=\"currentColor\" stroke=\"none\">B \u2192 \u03c3-Cu+) and the minor backdonation from the copper HOMO into the LUMO of the borylene moieties scale\" fill=\"currentColor\" stroke=\"none\">B). This is in contrast to the semi-bridging aminoborylene complexes [LnM{\u03bc-BN(SiMe3)2}M\u2032(CO)5] (LnM = (\u03b75-C5Me5)(OC)Ir, M\u2032 = Cr, W) and +\u2013[10]+. Despite the bonding interactions between the Mn and M evident in the structural data, no bond critical points (BCP) between the manganese and the coinage metal cations, nor any ring critical points, could be found for the three-membered M{MnB} rings, similar to previously reported multi- and dinuclear borylene-bridged complexes.2,8]+\u2013[10]+ are strongly bent towards the manganese atom, suggesting that the interactions between the boron and coinage-metal atoms are not covalent but rather \u03c3-donation from \u03c0-orbitals of the manganese borylene unit. The valence shell charge concentration (VSCC) close to the boron atom is extended over both metal\u2013boron BCPs coordinated coinage metal complexes have been presented and their bonding has been thoroughly examined using DFT calculations, in which the terminal metal\u2013borylene moieties are treated as a ligand as a whole for the first time.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "An unexpected N-heteroacene with a slipped two-dimensional ladder-like packing feature shows a hole mobility up to 0.3 cm2 V\u20131 s\u20131, while theoretical calculations suggest that this compound possesses potential well-balanced ambipolar charge-transport characteristics. b]phenazine) (2BPP) consists of two identical backbones piperazin-3-onephenazine), which are fused together through a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond and two intramolecular H-bonds. A study on the charge carrier transport indicates that a 2BPP single crystal has a hole mobility up to 0.3 cm2 V\u20131 s\u20131, while theoretical calculations suggest that this compound might possess potential well-balanced ambipolar charge-transport characteristics.An unexpected \u201ckinked\u201d N-heteroacene with a slipped two-dimensional ladder-like packing feature is produced from the conventional condensation reaction. The as-obtained compound bipiperazin-3-one[2,3- To date, most of the explored N-heteroacenes are linearly-fused systems, which can be prepared through the condensation reaction between ortho-diamine based acenes and ortho-diketone, ortho-dihydroxy, ortho-dicyano, or ortho-dihalogen substituted acenes and N-heteroacene derivatives have attracted a lot of attention, being widely investigated for applications in organic field-effect transistors (OFETs), organic resistance memories (ORMs), organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs).d acenes .6 HoweveTHNQ (shown in BTDP) and hexaketocyclohexane (HKCH), in which we believe that the steric effect of the TIPS group plays a crucial role.HKCH.BTDP and HKCH. In this situation, we might miss some important unknown N-heteroacene products. Thus, we reinvestigated this type of reaction and discovered a meaningfully \u201ckinked\u201d compound bipiperazin-3-onephenazine) (2BPP). To the best of our knowledge, this is the first report of the generation of a meaningfully \u201ckinked\u201d N-heteroacene through the conventional substitution reaction.In our previous study, we have already reported that linearly-fused N-heteroacene shown in can be p2BPP might undergo an unstable intermediate (UI) step, in which the diketone could be eliminated instead of participating in the further condensation reaction with the amine groups. The as-formed intermediate could be converted into the final product 2BPP through a rotation and radical pathway (initiated by light). The possible mechanism has been provided in the ESI (Scheme S12BPP was obtained in a low yield of 2.3% and was fully characterized by high-resolution mass (HR-MS) spectrometry, 1H NMR and 13C NMR spectroscopy, and single-crystal analysis. It is noteworthy that two 5,12-bis(TIPS)piperazin-3-onephenazine moieties are linked together by one double bond, which makes 2BPP fully \u03c0-conjugated along the backbone. In addition, the expected H-bonds along both sides were assumed to stabilize the large heteroacene system.As shown in Scheme S1. Note th14206812BPP suitable for single-crystal X-ray diffraction analysis were obtained by diffusing the poor solvent acetonitrile into a toluene solution. 2BPP crystallizes in a triclinic unit cell, space group P1(2). The molecular structure of 2BPP is shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond (1.35 \u00c5), suggesting that the two piperazin-3-onephenazine, BPP) moieties are connected by a C2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC2\u2032 bond. The distance between H1 and O1 or H1\u2032 and O1\u2032 is 1.95 \u00c5, indicating the existence of an intramolecular H-bond. Clearly, the formation of the intramolecular H-bonds with a six-member ring configuration is helpful for stabilizing the planar molecular shape and supports the electron delocalization. In fact, the as-prepared molecule possesses a good planarity from the side view scale\" fill=\"currentColor\" stroke=\"none\">C2\u2032 bond is \u223c2.42\u00b0. As shown in 2BPP exhibits a slipped 2-D \u03c0-stacking motif, similar to that observed for some soluble TIPS-pentacene derivatives. The interplanar distance in 2BPP is \u223c3.27 \u00c5 along the b axis, less than that of the typical distance for van der Waals interactions, while the centre-to-centre distance between two adjacent molecules is \u223c14.65 \u00c5. The slipping angle of two adjacent \u03c0-conjugated BPPs is \u223c45\u00b0, contributing to a significant molecular overlap and ensuring the strong \u03c0\u2013\u03c0 interaction. While viewing along the a axis, the distance between two adjacent molecules is \u223c3.33 \u00c5 and in this stacking mode, the characterized centre-to-centre distance is about 17.61 \u00c5 with a much smaller slipping angle (\u223c30\u00b0) between two interactional individual BPPs leading to poorer electronic coupling. 2BPP molecules interact with each other to form two-layer BPP units. The face-to-face stacking mode results in overlapping between the second layer units and the first layer BPPs can be determined to be 1.71 eV. The strong absorption from 650 nm to 725 nm is similar to that of other hydro-azaacenes, and probably comes from the intramolecular charge transfer. The electrochemical properties of 2BPP were investigated by cyclic voltammetry of \u20131.29 V, which determines the LUMO level of 2BPP to be \u20133.51 eV. The HOMO level was calculated to be \u20135.22 eV from the LUMO level and Eg. The geometry structure of 2BPP was optimized by DFT calculations (B3LYP/6-31G*),2BPP. In both the experimental and theoretical calculated results, 2BPP has relatively high HOMO levels and a moderate band gap, which indicates 2BPP could be used as a promising suitable semiconducting material.etry CV, . Unlike 2BPP were grown on an octadecyltrichlorosilane (OTS)-treated SiO2/Si substrate by a drop-casting method. OTS was used to form a siloxane self-assembled monolayer (SAM) on the SiO2 layer, which could promote and facilitate molecular self-organization during the growth of ribbons. The optical and AFM images in 2BPP ribbons display a rhombic shape with unambiguous boundaries, indicating the high quality of the ribbons. The as-obtained micro/nanoribbons are several to tens of micrometers in width, and several tens to hundreds of micrometers in length. Three sharp and strong diffraction peaks at 2\u03b8 = 5.19, 10.32, and 15.45 degrees are observed in the out of plane X-ray diffraction patterns (XRD) (c-axis (17.27 \u00c5), meaning that the molecules stand up along the c-axis with an angle of 73\u00b0 on the substrate. The major driving force for the self-assembly of the \u03c0-conjugated material is the \u03c0\u2013\u03c0 interaction from the adjacent molecules, which causes the superior growth direction along either the a-axis or b-axis. The measured angle of the lamellar crystal is 100.4\u00b0, which is consistent with the 100.2\u00b0 dihedral angle between the (100) and (010) planes in the crystal structure. From the crystal morphology, it can be clearly seen that the primary growth direction is along the \u03c0-stacking direction (b-axis). In this direction, the slipping angle between the adjacent overlapped 2BPP units and the close contact between the adjacent \u03c0-scaffolds contributes to the significant molecular overlap and ensures the effective charge transport in the \u03c0\u2013\u03c0 stacking , which cstacking . In addi\u03bc) was extracted from the saturation regime, and the mobility was calculated by the linear fitting of (IDS)1/2vs. VG curves. Nearly 50 transistors have been measured and all the devices exhibited good gate modulation. According to the transfer characteristics, the mobility was probed in the range of 0.008\u20130.3 cm2 V\u20131 s\u20131 along the b-axis, the best hole mobility could reach 0.3 cm2 V\u20131 s\u20131 with a threshold voltage (VT) of \u201310 to \u201325 V and on-to-off current ratios (Ion/Ioff) > 105.The crystalline ribbons grown on the substrates were fabricated as top-contact, bottom-gate configuration transistors. The gold source and drain electrodes were deposited with copper masks covering the selected ribbons. With this simple method, 50 nm of Au was deposited on the covered substrate; and then, the masks were removed from the ribbon surface and the ribbon devices with a length of about 20 \u03bcm were manufactured. The electrical characteristics of the devices were measured at ambient conditions. The transfer and output curves are displayed in 2BPP, Marcus electron transfer theory and an incoherent Brownian motion model have been employed to calculate the hole and electron mobilities which has a transfer integral of ca. 60 meV. Although the material has been predicted to possess a well-balanced ambipolar property, electron transport was not apparently observed and the measured mobility was relatively low. However, we believe that with proper modification of this specific heterocyclic molecule or tuning of the device fabrication conditions, ambipolarity and good transport character could be realized.To understand the structure\u2013property relationship of s see ESI based on2BPP), in which two BPP units are fused together through a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond and two H-bonds. Single crystal X-ray studies have demonstrated that 2BPP is a near coplanar molecule with close intermolecular interactions. For the double-layer structure, the face-to-face stacking mode results in an overlap between the second layer BPP unit and the first layer unit of the second BPP molecule, forming a ladder-like corrugate. The electronic structure calculations suggest the unique large heterocyclic molecule could exhibit a good intrinsic ambipolar charge transport property. Experimentally, single-crystal FETs with charge carrier mobilities of 0.3 cm2 V\u20131 s\u20131 and current on/off ratios of 105 have been realized. Further studies on the mechanism of this unusual compound as well as the hydrogen bonding supramolecular synthons would provide more insights to design and prepare novel large conjugated heteroacenes with unique properties.In conclusion, we have presented the synthesis and full characterization of an unexpected \u201ckinked\u201d N-heteroacene (Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The facile non-radiative decay for gold(iii) complexes is due to the thermally accessible 3LLCT, but not the usually assumed 3dd excited state. iii) arylacetylide complexes, , with different extents of \u03c0-conjugation at the doubly C-deprotonated [C^N^C] ligand via replacement of one of the phenyl moieties in the non-conjugated CH^N^C ligand (1) by a naphthalenyl (2) or a fluorenyl moiety . Conforming to the conventional wisdom that extended \u03c0-conjugation imposes rigidity on the structure of the 3IL(\u03c0\u03c0*(C^N^C)) excited state , the calculated Huang\u2013Rhys factors for the 3IL \u2192 S0 transition follow the order: 1 > 2 > 3-exo \u223c 3-endo, which corroborates qualitatively the experimental non-radiative decay rate constants, knr: 1 \u226b 2 > 3-exo, but not 3-endo. Density Functional Theory (DFT) calculations revealed that there is an additional triplet excited state minimum of 3LLCT character scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) \u2192 \u03c0*(C^N^C)]) for complexes 1 and 3-endo. This 3LLCT excited state, possessing a large out-of-plane torsional motion between the planes of the C^N^C and arylacetylide ligands, has a double minimum anharmonic potential energy surface along this torsional coordinate which leads to enhanced Franck\u2013Condon overlap between the 3LLCT excited state and the ground state. Together with the larger spin\u2013orbit coupling (SOC) and solvent reorganization energy for the 3LLCT \u2192 S0 transition compared with those for the 3IL \u2192 S0 transition, the calculated knr values for the 3LLCT \u2192 S0 transition are more than 690- and 1500-fold greater than the corresponding 3IL \u2192 S0 transition for complexes 1 and 3-endo respectively. Importantly, when this 3LLCT \u2192 S0 decay channel is taken into consideration, the non-radiative decay rate constant knr could be reproduced quantitatively and in the order of: 1 \u226b 3-endo, 2 > 3-exo. This challenges the common view that the facile non-radiative decay rate of transition metal complexes is due to the presence of a low-lying metal-centred 3dd or 3LMCT excited state . By analysis of the relative order of MOs of the chromophoric [C^N^C] cyclometalated and arylacetylide ligands, one may discern why complexes 1 and 3-endo have a low-lying 3LLCT excited state while 3-exo does not.We have performed theoretical analyses of the photophysical properties of a series of cyclometalated gold( One of the impediments to the progress of photoluminescence of gold(iii) complexes is the high electrophilicity of the gold(iii) ion and the presence of a low-lying Au(5d\u03c3*) orbital. In effect, the deactivating ligand-to-metal charge transfer (LMCT) and/or dd ligand-field excited states become close in energy to the emitting excited state, leading to efficient luminescence quenching in gold(iii) complexes.N-heterocyclic carbenes (NHC), to the gold(iii) cyclometalated complexes; these complexes were reported to be weakly emissive in solution (\u03c6 < 0.01) at room temperature.Gold(-lying Aud\u03c3* orbitiii) cyclometalated complexes with different extents of \u03c0-conjugation at the [C^N^C] ligand).iii) complexes with a fluorenyl moiety incorporated into the doubly deprotonated [C^N^C] ligand.iii) cyclometalated complexes in solution reach 0.58, and the corresponding non-radiative decay rate constant (knr) falls to 1.74 \u00d7 103 s\u20131 is replaced by a fluorenyl moiety.ii) complexes when compared with the non-conjugated CH^N^C analogue;To enhance the emission quantum yield, the structural distortion between the emitting excited state and the ground state must be minimized, thereby decreasing the non-radiative decay rate.endo\u201d in the gold(iii) pincer complex and a nearly 40-fold increase in the non-radiative decay rate constant (knr \u223c 6.76 \u00d7 104 s\u20131) when compared with its \u201cexo\u201d analogue (endo\u201d complex). This means that, even with a seemingly suitable cyclometalated ligand , the phosphorescence efficiency of gold(iii) complexes is not necessarily high. Thus, for effective design of functional luminescent molecules, it is important to understand the effect of \u03c0-conjugation in the C-deprotonated cyclometalated [C^N^C] ligand on the excited state properties of these luminescent gold(iii) complexes.Interestingly, when the fluorenyl moiety is disposed in such a fashion that the long alkyl chains are \u201ciii) complexes with different [C^N^C] cyclometalated ligand scaffolds (H^N^C (1) and the \u03c0-conjugated Cnp^N^C (2) and Cfl^N^C (3-exo and 3-endo); complexes 2 and 3-exo (and 3-endo) have one of the phenyl moieties of 1 replaced by a naphthalenyl (np) or a fluorenyl (fl) moiety respectively. The ancillary ligand, p-methoxyphenyl acetylide scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe]\u2013) is kept the same for all four complexes. A detailed list of definitions and abbreviations is provided in the appendix.In this work, we have performed a detailed theoretical analysis of four gold is in equilibrium with the ground state electron density of the solute, while the solvent nuclear polarization (the \u201cslow\u201d component) remains equilibrated with the excited state electron density of the solute. For this reason, we have employed the state-specific (SS) approach to account for the dynamical solvent effect. Within the SS scheme, rather than using the ground state electronic density as in LR-TDDFT and \u0394SCF, the electronic density of the emitting excited state is used to compute the ground state energy.ESSem) is given by:EESEQ(QES0) is the energy of the excited state (ES) with equilibrium solvation at the optimized excited state geometry (QES0), and EGSNEQ(QES0) is the energy of the ground state (GS) with non-equilibrium solvation at (QES0) and time-dependent DFT (TDDFT) are the commonly used tools to study the ground state and excited state properties of medium- to large-sized molecules. In the literature, computation of emission energies in solutions is performed using either linear response TDDFT (LR-TDDFT) or the \u0394SCF method. For both types of calculations, both the excited state of interest and the ground state are calculated with equilibrium (EQ) solvation. However, in an emission process, the ground state should be treated with solvent polarization in the non-equilibrium (NEQ) regimet (QES0) .11\u03bbs), which is the ground state energy difference calculated with non-equilibrium solvation (EGSNEQ(QES0)) and with equilibrium solvation (EESEQ(QES0)) at the optimized excited state geometry (QES0) :112\u03bbs \u03bbSSV) is given by:EGSEQ(QGS0) is the energy of the ground state computed with equilibrium solvation at the optimized ground state geometry QGS0 to the S0 state vibrational manifolds is given by the sum of individual radiative decay rate constants (denoted kr\u03b1(\u03bd\u0303)), each corresponding to a single vibronic transition, T1\u03b1(\u03c5\u2032 = 0) \u2192 S0(\u03c5\u2032\u2032), with photon energy, \u03bd\u0303, and vibrational quantum number for the T1 and S0 states, \u03c5\u2032 and \u03c5\u2032\u2032, respectively:The total radiative decay rate constant from the vibrational ground state of the emitting T\u03b7 is the solvent refractive index, \u03bd\u0303 is the triplet emission energy (in cm\u20131), and MT\u03b1(Q) is the transition dipole moment of the T1\u03b1 \u2192 S0 transition (in ea0), and the prefactor 8\u03c02/3\u03b50\u0127 = 2.0261 \u00d7 10\u20136.The radiative decay rate constant for the single vibronic transition can be calculated from the Einstein coefficient of spontaneous emission:12i.e., MT\u03b1(Q) \u2248 MT\u03b1(QT10) with QT10 being the optimized T1 excited state geometry) and combining eqn (4) and (5), the total radiative decay rate constant, kr\u03b1, is given by:13\u03c7\u03c5\u2032\u2032 and \u03c7\u03c5\u2032 are the vibrational wavefunctions of the S0 and the T1 states respectively.By invoking the Condon approximation can be accounted for by the Franck\u2013Condon factors ((|\u222b\u03c7*\u03c5\u2032\u2032\u03c7\u03c5\u2032dQ|2). In general, one may approximate the last term in the summation as:13I(\u03bd\u0303) being the emission intensity at \u03bd\u0303 (corrected to the number of photons emitted per unit wavenumber). The emission intensity can be obtained either from experiment or by computational simulation. The total radiative decay rate constant for the T1\u03b1 \u2192 S0 transition may then be written as:Unless the emission spectrum is sharply peaked, as in an atomic emission spectrum, one should not take the integral in eqn (6) as unity and replace the summation in eqn (6) by the emission peak maximum, MT\u03b1(QT10) could be obtained by first-order perturbation interactions between the T1\u03b1-spin sub-state and the singlet excited state via spin\u2013orbit coupling (SOC):12Mm,jS is the j-axis projection of the Sm \u2192 S0 transition dipole moment, E(T1) and E(Sm) are the energies of the T1 and the mth singlet (Sm) excited states, respectively, and T1\u03b1|HSOC|Sm are the SOC matrix elements between the T1\u03b1-spin sub-state and the Sm excited state.The transition dipole moment 1\u03b1-spin sub-states is less than 5 cm\u20131, all sub-states should be equally populated at room temperature. Therefore, the average radiative decay rate constant kr is given by:As the energy splitting between the three Tknr) of the T1 \u2192 S0 transition can be estimated by application of the Fermi's Golden Rule expression, assuming that both electronic states are harmonic:14In the limit of the Franck\u2013Condon approximation in the non-adiabatic regime, the non-radiative decay rate constant intraligand vibrational modes (\u0127\u03c9M > 1000 cm\u20131), typically corresponding to the aromatic CC/CN stretching modes (\u0127\u03c9M \u223c 1200\u20131500 cm\u20131) and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC stretching modes scale\" fill=\"currentColor\" stroke=\"none\">CC \u223c 2200\u20132300 cm\u20131) if the acetylide ligand is involved in the complex; \u03bbS is the solvent reorganization energy and may be obtained from eqn (2); \u0394E is given byE00 being the zero-point energy difference between the T1 and S0 states and \u03bblf being the reorganization energy contributed by the low-frequency (lf) modes of the complex . Assuming that all the normal modes are harmonic oscillators,Sj, mj, and \u0394Qj are the Huang\u2013Rhys factor, the reduced mass, and the equilibrium displacement of the jth normal mode \u03c9j, respectively; SM and nM are the Huang\u2013Rhys factor and the number of quanta of the effective high frequency mode \u0127\u03c9M (corrected to the nearest integer), respectively:This expression can be applied when \u03bbFCv, could be estimated as:\u03c9j.Under the harmonic oscillator approximation, the intramolecular reorganization energy, 2Cl2; \u03b7 = 1.424).0) and the lowest triplet excited state (T1) were respectively carried out using restricted and unrestricted density functional theory formalisms without symmetry constraints. Frequency calculations were performed on the optimized structures to ensure that they were minimum energy structures by the absence of imaginary frequency . Stability calculations were also performed for all the optimized structures to ensure that all the wavefunctions obtained were stable.In this work, the hybrid density functional, PBE0,E(Sm), the associated transition dipole moment of the Sm \u2192 S0 transition Mm,jS , and the coefficients necessary to compute the SOC matrix elements of Au in the MO relevant to the coupling excited states and the corresponding CI coefficients), were all obtained from a state-specific approach using \u201cExternalIteration\u201d implemented in G09.Vertical transition energies were computed using the linear response approximation for absorption, but the state specific approach for emission.Sj (using eqn (12c)) for the normal mode j\u03c9 may be obtained by performing a Franck\u2013Condon calculation implemented in G09 via \u201cfreq = fc\u201d and \u201cprtmat = 2\u201d. The simulated emission spectrum allows one to calculate the Franck\u2013Condon factor-weighted emission energy \u03bd\u0303fcf (using eqn (7)). The high-frequency normal modes (1000 < \u0127\u03c9m \u2264 1800 cm\u20131) can be characterized by a mean frequency \u03c9M and an effective electron-phonon coupling strength (or Huang-Rhys factor) SM:21The Huang\u2013Rhys factor Further computational details can be found in the ESI.1, 3-exo, and 3-endo are in good agreement with the X-ray crystallography data (<0.05 \u00c5 and 8.5\u00b0) except for the dihedral angle between the planes of the [C^N^C] ligand and the phenyl ring of the acetylide ligand (\u03b4); calculations revealed a nearly coplanar geometry (\u03b4 \u223c 5.7\u00b0 and \u20130.27\u00b0 for 1 and 3-exo respectively) whereas experimentally determined \u03b4 values are 66.1\u00b0 and 54\u00b0 respectively.3-endo (\u03b4 \u223c 130\u00b0), the corresponding X-ray data is only \u223c59\u00b0 (see ESI3-endo). In addition, the Au\u2013C(acetylide) distance for 1 was calculated to be 1.950 \u00c5 while the corresponding distance from the crystallography data is 2.009 \u00c5.H^N^C)AuIIIC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCPh-4-Y] (Y is a substituent) complexes are in the range of 1.945\u20131.980 \u00c5;In general, the optimized ground state structures of 0 geometries of the four complexes studied herein. A full list of the TDDFT results can be found in the ESI.1 is 1LLCT in nature (LLCT = ligand-to-ligand charge transfer), with a calculated vertical excitation energy at \u03bb = 408 nm (f = 0.23).53-exo, the first singlet excited state (S1) is a 1LLCT excited state, derived mainly from the HOMO \u2192 LUMO transition, 1[\u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) \u2192 \u03c0*(C^N^C)] in character (>80%); this 1IL excited state is derived from the H \u2013 1 \u2192 LUMO transition and is a 1\u03c0\u03c0*(C^N^C) excited state. The difference in the nature of the S1 excited state among the four complexes can be rationalized as follows: upon increasing the \u03c0-conjugation along the series 1, 2, 3-endo, and 3-exo, H \u2013 1 is destabilized and the MO splitting (\u0394\u03b5) between HOMO and H \u2013 1 decreases from 0.62 eV (1) to 0.26 eV (3-endo) and 0.20 eV (3-exo), , . This de Table S9. As a reiii) complexes are listed in The experimental photophysical data regarding the emissions of the four gold.As depicted in 2 and 3-exo, only one triplet excited state, 3\u03c0\u03c0*(C^N^C) IL excited state, was found. On the other hand, two triplet excited state minima, one 3IL in character and the other 3LLCT scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) \u2192 \u03c0*(C^N^C)]), were found for both 1 and 3-endo. The electron difference density maps (eddms) for the calculated triplet excited states, together with the relative energy splitting between the 3IL and 3LLCT excited states for complexes 1 and 3-endo, are presented in To understand the emission properties of the four complexes depicted in E00), vertical emission energies , and radiative decay rate constants of the optimized T1 excited states of the four gold(iii) complexes studied herein. \u0394ESSem, , Franck\u2013(i)2, there is generally a close correlation between the experimental solution emission maxima (\u03bbmax) at room temperature and the calculated \u0394E00 of the 3IL excited states of the gold(iii) complexes in 1, 3-exo, and 3-endo, the emission maximum may correspond to the 0\u20130 transition of 3IL \u2192 S0. The experimental emission maximum of 2 is at a lower energy than that of 3-exo (ii) [C^N^C] cyclometalated complexes, the one with a naphthalene moiety at the [C^N^C] ligand displays a higher energy emission peak than the one with a fluorene unit .ii) [C^N^C] cyclometalated complexes: \u0394E00 of the gold(iii) complexes is in the order 1 > 2 > 3-endo \u223c 3-exo. This trend is a manifestation of the increase in \u03c0-conjugation at the [C^N^C] cyclometalated ligand when one goes from 1 to 2 to 3-endo and 3-exo. Increasing \u03c0-conjugation destabilizes the \u03c0(C^N^C) orbital, .With the exception of of 3-exo . For relsee also , thereby(ii)1 excited states of the four complexes. Although the kr values of the 3IL excited states are slightly underestimated by a factor of \u223c2.7\u20133.1, they are consistent with the experimental kr values except in the case of 2 complexes .2 at 298 K and 77 K originated from different excited states. However, no other triplet excited state minimum was found for complex 2 using the present DFT/TDDFT method. compare with 4. perature . However(iii)3IL excited states of the four gold(iii) complexes. As depicted in SM) are in the order: 1 > 2 > 3-exo \u223c 3-endo. This trend is in line with the S0 to T1 structural distortion of the following organic molecules in the order: benzene > naphthalene > carbazole (carbazole is isoelectronic to fluorene).3IL excited states of these four gold(iii) complexes are mainly localized on the phenyl, naphthalenyl, and fluorenyl moieties, respectively to the H \u2013 1 (HOMO for 3-exo and 3-endo), at their optimized T1 geometries, are 4.18 (1), 0.36 (2), 1.94 (3-exo), and 1.07 (3-endo), respectively. As SOC is mainly brought about by the gold(iii) ion, the larger the coefficient of Au(d) in the H \u2013 1/HOMO, the larger should be the SOC matrix element, 3IL|HSOC|S02. The Au(d) character in the H \u2013 1/HOMO of the gold(iii) complexes studied herein is related to the nature of the HOMO of the C-deprotonated moiety in the [C^N^C] ligand. For complex 2, the H \u2013 1 is mainly localized on the long molecular axis of the naphthalene fragment (np^N^C] ligand to have little interaction with the gold(iii) ion and therefore, the smallest cd in the H \u2013 1 orbital of 2. On the other hand, the corresponding orbital of complex 3-exo is along the short molecular axis of the fluorene fragment, thus the [Cfl^N^C] ligand could have a stronger interaction with the gold(iii) ion, and hence, a larger cd in the HOMOs of complexes 3-exo and 3-endo.Besides, the magnitude of the SOC matrix element between the fragment , thus reSM and the SOC between the T1 and S0 states are largest for 1, the calculated non-radiative decay rate constant knr for the 3IL \u2192 S0 transition is smaller than that of 3-exo, a result contrary to the order of experimental knr values; knr: 2 > 3-exo > 1; knr(expt): 1 \u226b 2 > 3-exo. This is because 1 has a much larger energy gap between the 3IL and S0 states than the other three gold(iii) complexes (knr (3IL \u2192 S0) of 1. Similarly, the calculated non-radiative decay rate constant for 3-endo is \u223c1.25 \u00d7 103 s\u20131, which is also smaller than that of 3-exo, and is inconsistent with the experimental data scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) \u2192 \u03c0*(C^N^C)], excited state. This 3LLCT excited state displays a large amplitude motion along the dihedral angle between the [C^N^C] plane and the arylacetylide plane (\u03b4): from \u223c\u20134.132\u00b0 (S0) to \u201388.739\u00b0 (3LLCT) for 1 and from 130.381\u00b0 (S0) to 92.352\u00b0 (3LLCT) for 3-endo (see 0 and 3LLCT excited states for complexes 1 and 3-endo). Because of this large amplitude motion, we refrained from performing a Franck\u2013Condon calculation on the 3LLCT \u2192 S0 transition, as we have performed for that of the 3IL \u2192 S0. This is because, for the Franck\u2013Condon calculation implemented in G09, the normal modes are represented in Cartesian coordinates. Cartesian coordinates are inadequate to describe large amplitude motions, such as torsions, as this could lead to artificial bond breaking and bond forming at its extreme.3LLCT to the S0 state. Moreover, such fictitious bond breaking and bond forming will lead to a diffuse Duschinsky matrix, which could lead to an incorrect interpretation of the fast non-radiative decay rate constant due to a large Duschinsky effect.Although both the effective Huang\u2013Rhys factor omplexes , making compare and 5. Fas found . This tr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC stretching normal mode is decoupled from the other normal modes, as reflected by the Duschinsky matrix elements of the 3LLCT \u2192 S0 transition; \u03c9 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCC is the only normal mode that has the diagonal matrix element equal to 1. Therefore, we estimated the non-radiative decay rate constants of the 3LLCT excited state by replacing all the Huang\u2013Rhys factors (Sj) of the 3LLCT \u2192 S0 transition with those of the 3IL \u2192 S0 transition, but keeping the Huang\u2013Rhys factor of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC stretching normal mode from a Franck\u2013Condon calculation of the 3LLCT \u2192 S0 transition. Such an assumption is based on the fact that both the 3LLCT and 3IL excited states of the gold(iii) complexes involve changes in electron density at the [C^N^C] ligand.Nevertheless, the C3LLCT excited states of 1 and 3-endo are noted: (a) The solvent reorganization energy (\u03bbS) of 3LLCT is much larger than that of 3IL. This is attributed to the dipole moment of the 3LLCT being much larger than that of 3IL and the ground states (see \u03bcT1) and \u03bcGS)). In the framework of the SS approach, solvent reorganization energy is proportional to the square of the difference in dipole moments between the T1 excited state and the S0 ground state, i.e., \u03bbs \u221d (\u03bcT1 \u2013 \u03bcGS)2.3LLCT and the S0 potential energy surfaces (PESs) at the equilibrium geometry of the 3LLCT excited state. Thus, fewer quanta of the high-frequency vibrational mode (nM) are needed (see eqn (12e)) and the activation energy ) is smaller as this energy term is inversely proportional to the solvent reorganization energy; (b) the square of the HSOC matrix element between the 3LLCT excited state and the S0 ground state is larger than that between the 3IL excited state and the ground state calculation of the 3LLCT \u2192 S0 transition. (We have used the Huang\u2013Rhys factor of the 3IL \u2192 S0 transition where there is no such large amplitude torsion.) We have undertaken a rigid scan along the torsional coordinate (\u03b4) for 1. \u03b4 for the ground state, 3IL excited state, and 3LLCT excited state of complex 1. The potential energy minimum is roughly harmonic for both the ground state and the 3IL excited state but anharmonic for 3LLCT excited state. As the 3LLCT excited state has a double minimum potential while the ground state is approximately harmonic, the Franck\u2013Condon factor (FCF) between 3LLCT and S0 is expected to be larger than that between the 3IL and S0 states, where both PESs are harmonic along the torsion coordinate \u03b4. This may be rationalized as illustrated in 3LLCT excited state) than that with a harmonic PES \u223c 1.6 \u00d7 107 s\u20131 and knr(expt) \u223c 5.9 \u00d7 107 s\u20131). In other words, the major deactivating channel for the emissive excited state of 1 is not 3dd or 3LMCT, as is usually ascribed to efficient non-radiative decay for luminescent transition metal complexes, but 3LLCT due to a large SOC, a large solvent reorganization energy, and the non-planar torsional motion between the [C^N^C] and arylacetylide ligands. For 3-endo, the 3LLCT excited state is calculated to be \u223c1400 cm\u20131above that of the 3IL state. Therefore, the re-estimated knr becomes \u223c1.5 \u00d7 104 s\u20131, which is in good agreement with the values derived from the experimental measurements in solutions at 298 K (knr(expt) \u223c6.8 \u00d7 104 s\u20131).If one supposes that the torsional motion increases the FCF of the 3LLCT excited state that contributes to the very fast non-radiative decay rate. The relative order of the 3LLCT and 3IL excited states would thus be important in determining the phosphorescence efficiency. In the present series of gold(iii) complexes, this relative order can be understood from the relative energies of the \u03c0(C^N^C) and \u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) MOs. As the LLCT excited state is a charge transfer excited state, while the IL excited state is localized, the singlet\u2013triplet splitting of LLCT excited states (E(1LLCT)\u2013E(3LLCT)) would be smaller than that of IL excited states (E(1IL)\u2013E(3IL)). In the case of 1, due to the large orbital energy difference (\u0394\u03b5) between the \u03c0(CH^N^C) and \u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) MOs MOs , the 1ILed state .3IL\u20133LLCT gap of 2 should fall between that of 1 and 3-endo, as deduced from the relative order of the \u03c0(Cnp^N^C) and \u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) MOs depicted in 3LLCT excited state was located in the course of LR-TDDFT optimization; subsequent SS-TDDFT calculation at this geometry showed that this 3LLCT excited state is lower-lying than the 3IL one. However, global hybrid density functionals, generally underestimate the energy of charge transfer excited states within the TDDFT framework. Thus, we performed UDFT optimization starting from these TDDFT-optimized structures (which have a stable wavefunction) to see if there is a 3LLCT excited state minimum. Unfortunately, UDFT optimization starting from the TDDFT-optimized 3LLCT excited state went back to the 3IL excited state. It is likely that this 3LLCT excited state is metastable and exhibits vibronic coupling with other close-lying excited states.Based on the above rationale, it is speculated that the iii) [C^N^C] cyclometalated complexes with different extents of \u03c0-conjugation. It is commonly prescribed that a rigid ligand in a transition metal complex can minimize structural distortion between the emitting triplet excited state and the ground state, thereby decreasing the non-radiative decay rate. Franck\u2013Condon analyses on the 3\u03c0\u03c0*(C^N^C) IL \u2192 S0 transitions of the four gold(iii) complexes confirmed that an increase in \u03c0-conjugation at the [C^N^C] cyclometalated ligand results in a more rigid transition metal complex, as reflected by the effective Huang\u2013Rhys factor, SM: 1 > 2 > 3-exo and 3-endo. Although this trend correlates with the experimentally determined non-radiative rate constants, 1 \u226b 2 > 3-exo, the calculated knr of the 3IL \u2192 S0 transition is inconsistent with the experimental data if one also takes into consideration the 3IL\u2013S0 energy gap. DFT/TDDFT calculations reveal that there is an additional triplet excited state minimum, 3[\u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) \u2192 \u03c0*(C^N^C)] LLCT, for complexes 1 and 3-endo, but not for 3-exo. It was found that the non-radiative decay rate constant for this 3LLCT \u2192 S0 transition exceeds 107 s\u20131, which is more than three orders of magnitude faster than the knr for the 3IL \u2192 S0 transition. More importantly, if the relative splitting between the 3LLCT and 3IL excited states was included in estimating the knr of complexes 1 and 3-endo, the calculated and experimental knr are in quantitative agreement. Based on the analysis of the relative order of \u03c0(C^N^C) and \u03c0 scale\" fill=\"currentColor\" stroke=\"none\">CPh-4-OMe) MOs, one could rationalize why complexes 1 and 3-endo, but not 3-exo, have low-lying 3LLCT excited states. Our present analysis highlights the importance of the relative order of the frontier MOs of the coordinating ligands in multi-chromophoric transition metal complexes in designing strongly luminescent transition metal complexes. It also challenges the presumption that the low phosphorescence efficiency of transition metal complexes is due to the close proximity of the dd ligand-field state to the emitting triplet excited state.We have carried out a detailed theoretical study on four gold(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Aziridine aldehydes participate in a multicomponent reaction with \u03b1-amino amides and isocyanides to generate reactive imidoanhydride intermediates. Aziridine aldehyde dimers, peptides, and isocyanides participate in a multicomponent reaction to yield peptide macrocycles. We have investigated the selectivity and kinetics of this process and performed a detailed analysis of its chemoselectivity. While the reactants encompass all of the elements of the traditional Ugi four-component condensation, there is a significant deviation from the previously proposed mechanism. Our results provide evidence for an imidoanhydride pathway in peptide macrocyclization and lend justification for the diastereoselectivity and high effective molarity observed in the reaction. The vast majority of chemical processes rely on polar reactions between nucleophilic (Nu) and electrophilic (E) functional groups.91 . This pathway differs substantially from conventional Ugi MCR reactivity. We present evidence that implicates imidoanhydrides in aziridine aldehyde-driven macrocyclization of peptides. Our study underscores the notion that kinetically amphoteric molecules provide fertile grounds towards the deployment of underexplored intermediates and their application in the synthesis of valuable products.In this paper, we evaluate multicomponent reactivity between isocyanides, aziridine aldehydes, and linear peptides towards peptide macrocycles, an increasingly important class of molecules.Since 2010, we have been investigating the utility of aziridine aldehydes in the synthesis of chiral molecules.429, suggested that the rate-determining step was the formation of open dimer 4 (6 (the iminium ion produced from compounds 4 and 5), is a concerted asynchronous process with carboxylate group engagement that takes place at the same time as the isocyanide addition, directing the face of isocyanide attack to form mixed anhydride 8 LY(tBu)F in a TFE/DCM (1\u2009:\u20091) mixture.13C-labelled PS(tBu)LY(tBu)F precursor 10 reacted with excellent selectivity for macrocycle 12 as the parent sequence, which contained all hydrocarbon side chains. During the course of these studies, two products were identified in addition to the aziridine amide-bearing macrocycle (B). These were assigned to a bridged-amidine (C) and an amidine (D). Bridged-amidine products (C) failed to react with several different nucleophiles, confirming that no aziridine ring was present in the structure, while amidine products (D) were isolated after telescopic ring-opening with thioacids and desulfurization.I* has also been isolated in select instances and PH\u03b1 resonances were missing. We identified three new signals were found around 45 and 20 ppm for the methine and methylene positions, respectively. In contrast, the 13C and 1H\u201313C HSQC NMR spectra of 18C were devoid of these resonances, ruling out the possibility that 18C still contained an aziridine unit.The structure of the bridged-amidine products was assigned by a combination of 1D and 2D NMR. In the signals instead R see ESI, the conne group . The 13CC\u03b1 was designated as a quaternary center in 18C as no corresponding PH\u03b1 resonance could be observed in either the 1H or 1H\u201313C HSQC NMR. Another diagnostic difference in the 1H\u201313C HMBC NMR was the fact that the F PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC and P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC chemical shifts were observed at 173 ppm and 169 ppm, respectively. The F PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC chemical shift was notably more upfield than a typical carbonyl of an aziridine amide (>180 ppm),18C.P15N, 1H\u201315N HSQC, and 1H\u201315N HMBC NMR . An 15N-labelled bridged-amidine peptide, 25C, was isolated and studied by 15N NMR. Gratifyingly, a 15N signal at 103 ppm was observed for the labelled compound 25C in DMSO-d6 with 0.1% formic acid , and too far upfield to be consistent with an amide (110\u2013130 ppm), but was in good agreement with reported chemical shifts for protonated amidines. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNC was also in line with the literature reported chemical shift of amidine carbons.49The identity of the nitrogen atoms was confirmed by R see ESI. In all mic acid . By 1H\u201311H\u201313C HMBC NMR . Using a similar set of NMR methods as those used for the structure elucidation of 18C and 25C scale\" fill=\"currentColor\" stroke=\"none\">O2C.To isolate the non-bridged amidine products, we employed the telescopic methodC see ESI, we dedu amidine . The 1H\u201322D and other amidine derivatives, we noticed that two peaks corresponding to the amidine product could be resolved, yet after purification they had a tendency to coalesce into one product by NMR. The PH\u03b1 atom is allylic with respect to the amidine moiety and thus potentially labile and prone to epimerization to a more thermodynamically stable epimer. Using 2D ROESY NMR, the major isomer of 22D was assigned as epi-22D and amidine (D) products involved the proline amide, we sought to perturb the system by varying either the N-terminal proline residue or the amino acid adjacent to proline and studying the effects on the cyclization outcome. First, we employed N-methylated amino acids in an attempt to affect the nucleophilicity of the proline amide. We observed no productive reaction from sarcosine- or N-methyl-leucine-containing peptides P-Sar-LGF and P-MeLeu-LGF and could not isolate neither the peptide macrocycles nor the amidine and bridged-amidine products (see ESIAs the formation of both the bridged-amidine (s see ESI.18). (l-\u03b2-homoPro)-GLGf failed to produce any of the expected products (see ESIl-\u03b1-MePro)-GLGf, formation of the amidine product was observed by NMR, but no bridged-amidine product was observed or isolated LY(tBu)F linear peptide 10 to obtain finer detail on the features that govern productive macrocyclization. (l-\u03b2-HomoPro)-S(tBu)LY(tBu)F failed to react productively to make the macrocycle or either of the amidine products , only trace aziridine amide peaks were detected by 13C NMR LY(tBu)F F 10, , where tBu)F 10, . The ratpecies 4 . While i32 and aziridine aldehyde dimer 3 would form the nitrilium intermediate, 33 or in a concerted addition, similar to the piperazinone chemistry .The imidoanhydride intermediate C and D, . If we cidine 39 . Aziridi39 and acidity of the PH\u03b1 would enable direct deprotonation of PH\u03b1 to make enamine 43 or imidate-containing (40) intermediates , the reaction also failed, presumably due to the comparably disfavoured seven-membered ring formation requirement.Further proof for the involvement of nditions . When pr47 and 48, we conclude that the proline amide is vital to the cyclization and these results imply that imidoanhydride 37 would be the first expected intermediate and the driving force for the diastereoselectivity (37 at either of the two positions, one of which would generate the macrocycle precursor 34 or the 14-membered ring 45. Compound 45 is yet another mixed anhydride which can undergo intramolecular transacylation with the aziridine to generate the macrocycle. The aziridine can also attack the other position of mixed anhydride 45 to generate 46, the aziridine amidine that is the precursor to the amidine products. Intermediate 46 can also be formed directly from 37 as presented in the amidine pathways (Based on the unfavourable cyclizations of ectivity . From thpathways .37, N-terminus and match of stereochemistry between the N-terminal amino acid and aziridine aldehyde dimer.37 is formed at the N-terminus, the linear peptide tail has to fold in for attack by the C-terminal carboxylate. While the experimental evidence obtained in the course of our work is consistent with the intermediacy of 37, parallel macrocyclization pathways cannot be discounted (In order to rationalize favourable conditions and a peptide sequence that will result in a macrocycle, it is important to note the duality of bond-forming events in the proposed mechanism . The firscounted .The abundance of intramolecular pathways leading to amidine and bridged-amidine products and 10 eN-terminal amide acting as a kinetic trap to avoid intermolecular reactivity with the nitrilium ion, the occurrence of multiple intramolecular pathways from the imidoanhydride intermediate avoids the oligomerization issues seen with conventional Ugi reactions to make macrocycles. This serves to increase the effective molarity of the reaction. The amide participation suggests a way for selecting a cyclization-friendly sequence. These considerations will help improve the cyclization process and enable pre-selection of cyclization-friendly linear peptide sequences. In broader terms, the interception of nitrilium ions by nucleophilic amides to yield imidoanhydrides may play a role in other MCRs,We have probed the mechanism of the aziridine aldehyde-promoted macrocyclization reaction. This investigation unveiled the features governing both diastereo- and chemoselectivity of the process. Through kinetic analysis and product characterization, we have found evidence for an imidoanhydride-driven pathway during macrocyclization with aziridine aldehydes. With the Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "This side-by-side reactivity study of a borylene and a diborene with the same empirical formula demonstrates their non-interconvertibility. 4 -3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, (II), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis. Furthermore, reactions of I or II with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC-stabilized cyanoboron\u2013chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena-2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between I and II.The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)] Having failed thus far to realise the interconversion of I and II through photolysis and/or heating, we were eager to test their respective reactivity with suitable reagents in order to define any differences or similarities, and hopefully gain definitive proof of their ability (or inability) to interconvert. Herein we present the reactivity of I and II with elemental chalcogens and dichalcogenides, based on our recently-reported reactions of these chalcogen reagents with B\u2013B multiply-bonded species.I and its formal dimer II, and they may therefore be viewed as close relatives, subtle differences in reactivity confirm that no Wanzlick-type equilibrium exists between the two.Our recent synthesis of the aforementioned tetraborylene macrocycle [(cAAC)B(CN)]4 I; , left9 aAC)] II; , right11I with four equivalents of diorganyldichalcogenides, E2R2 in benzene proceeded selectively to the corresponding cAAC-supported cyanoboron dichalcogenides, [(cAAC)B(CN)(ER)2] , which were isolated in moderate to good yields 2 (\u201318.4 ppm) and 3 (\u201314.4 and \u201315.8 ppm) exhibiting shifts significantly downfield from the bis(sulfide) 1 (\u20139.6 ppm). Furthermore, at room temperature the bis(phenylselenide) 3 displayed highly broadened 1H NMR ligand resonances as well as two distinct, very broad 11B NMR resonances (\u201314.4 and \u201315.8 ppm), which coalesced upon heating to 70 \u00b0C, indicating hindered rotation, presumably owing to steric interactions between the bulky cAAC substituents and the large phenylselenide ligands.The reaction of tetrameric borylene d yields . WhereasII and Ph2S2 or Ph2Se2 showed the monoboron bis 1 and 3 to be sole products of these reactions, independent of the stoichiometry used scale\" fill=\"currentColor\" stroke=\"none\">B double bond and, subsequently, across the remaining B\u2013B single bond. Although both compounds I and II reacted with Ph2Te2 at high temperatures, these reactions were rather unselective and did not yield any tractable products.NMR spectroscopic data of reaction mixtures of diborene try used . These r1\u20133 readily crystallized from THF at room temperature, 1 as a colorless crystalline solid, and 2 and 3 as yellow crystals.2 repeatedly crystallized as extremely thin, overlapping yellow plates, which could not be separated. X-ray crystallographic analysis of these provided proof of connectivity but data were of insufficient quality for further structural discussions \u00c5) is slightly elongated compared to that in diselenide 3 (1.597(9) \u00c5). The B\u2013CCN bond lengths (1: 1.584(2); 3: 1.580(9)) are similar to those found in other cAAC-supported cyanoboranes (1.574(5)\u20131.589(3) \u00c5).d]dithiaboroles (B\u2013S: 1.899(5)\u20131.930(2) \u00c5)ortho-carboranes (B\u2013Se: 2.031(6)\u20132.065(5) \u00c5).1\u20133 represent the first examples of boron chalcogenides synthesized by the atom efficient insertion of a borylene into the E\u2013E bond of a diorganodichalcogenide.Compounds I with elemental sulfur in a 1\u2009:\u20091 boron-to-sulfur ratio in benzene for 5 d at room temperature resulted in a yellow suspension, which upon filtration and slow evaporation yielded compound 4 as a yellow crystalline solid . The analogous reaction with elemental selenium at 60 \u00b0C for 3 d similarly provided compound 5 as an orange crystalline solid in 70% yield. Compound 5 was isolated as a single species with an 11B NMR singlet at \u201333.5 ppm, shifted ca. 25 ppm upfield from that of 4, and a highly shielded, broad 77Se{1H} NMR resonance at \u2013143.1 ppm. In solution at room temperature 5 partially isomerized to a second species presenting an 11B NMR shift at \u201331.8 ppm and slightly shifted 1H and 13C NMR resonances. High resolution mass spectrometry experiments performed on 4 and 5 provided molecular masses consistent with dimeric compounds of the formula [(cAAC)B(CN)E]2 .Stirring of a dark red suspension of tetrameric borylene ne solid . Compoun4 and 5 crystallized in near-identical triclinic unit cells as centrosymmetric species presenting planar 1,3-dithia- and 1,3-diselena-2,4-diboretane cores, respectively. The B2S2 ring in 4 is an approximate square with four almost identical B\u2013S bonds (1.939(3) and 1.940(3) \u00c5) and near-perpendicular B\u2013S\u2013B and S\u2013B\u2013S angles (85.21(12) and 94.80(12)\u00b0, respectively), whereas the planar B2Se2 ring in 5 displays two slightly different B\u2013Se bond lengths (2.069(4) and 2.100(4) \u00c5) as well as near-perpendicular B\u2013Se\u2013B and Se\u2013B\u2013Se angles (85.13(17) and 94.87(17)\u00b0, respectively). There are only a couple of structurally characterized 1,3,2,4-dichalcogenadiboretanes in the literature, all displaying sp2 hybridized boron centers stabilized by \u03c0-donating amino substituents.2S2 and B2Se2 heterocycles are ca. 0.08\u20130.10 \u00c5 shorter than in 4 and 5, while the B\u2013E\u2013B and E\u2013B\u2013E angles are ca. 3\u00b0 narrower and wider, respectively.18This was confirmed by X-ray crystallographic analyses, the results of which are displayed in es , 5: 1.606(5) \u00c5) suggest that the cAAC ligand functions as a pure \u03c3-donor ligand to the sp3 borane, unlike in borylene I, where a significant contribution of \u03c0-backbonding from the electron-rich B(i) center shortens the bond (ca. 1.47 \u00c5). It is noteworthy that both the B\u2013CcAAC and B\u2013CCN bond lengths are significantly longer in 4 than in 5 (B\u2013CCN: 4 1.597(4), 5 1.577(6) \u00c5).For both compounds the plane consisting of the cyanoboron moiety and the \u03c0-framework of the cAAC ligand forms a 4 proved indefinitely stable in solution at room temperature, the 11B NMR spectrum of an analytically pure sample of 5 in CD2Cl2 left at room temperature for 3 d showed the partial disappearance (<10%) of 5 concomitant with the appearance of a new boron-containing species at \u201322.8 ppm (2B2(CN)2Se] (6). X-ray crystallographic analysis of this compound showed that 6 is indeed a bis(cAAC)-stabilized 2,3-dicyano-2,3,1-diboraselenirane . The disordered 2,3-dicyano-2,3-diboraselenirane cores of both parts were freely refined. Fig. S45\u00a7The solid-state structure of molecule The structure of 6 is similar to that of the bis(NHC)-stabilized 2,3-dithienyl-2,3,1-diboraselenirane obtained by our group upon reaction of one equivalent of selenium with the corresponding diborene precursor,trans-arrangement of the cyano and cAAC ligands with respect to the B2Se core. Attempts to generate 6 from I using a 2\u2009:\u20091 boron-to-selenium ratio failed, resulting instead in 50% conversion to the diselenadiboretane 5, with the remaining 50% of I left unreacted at room temperature in C6H6, as shown by the appearance of the 11B NMR shift around \u201322 ppm at room temperature in C6H6 yielded the corresponding 2,3-dicyano-1,2,3-thiadiborirane 7 H2B\u2013B(CO)(cAAC)], which we reported recently.19The reaction of 33.5 ppm . Similarretane 4 . But whe7 showed a structure very similar to that of its selenium analogue 6, displaying the same trans-arrangement of the cyano and cAAC ligands with respect to the B2S core (7 1.777(6); 6 1.757(6) \u00c5) enforced by the significantly shorter B\u2013E bonds and the slightly wider B\u2013E\u2013B angle (6: 56.9(2); 7: 51.31(18)\u00b0). Unlike the IMe-supported dithienyldiborene2Mn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tBtBu(IMe)] (Cp = cyclopentadienyl),I or II showed any reactivity toward elemental tellurium in toluene, even after prolonged heating in benzene at 80 \u00b0C.Single crystals of B2S core . The onl4 the refinement of the data generated some residual electron density around the B2S2 ring that hinted at its overlap with a five-membered 1,2,4-dithia-3,5-diborolane ring representing less than 5% of the structure. This was consistent with the observation that recrystallized samples of 4 always showed some contamination with another species showing an 11B NMR resonance at \u20139 ppm, and that closer inspection of the mass spectrum of 4 revealed traces of a compound with the formula [(cAAC)2B2(CN)2S3]. Based upon this observation, attempts were made to obtain this compound by addition of sulfur to 4. However, even in the presence of excess sulfur with prolonged heating at 60 \u00b0C, only starting material was recovered of the reaction of borylene I with selenium in a 2\u2009:\u20093 boron-to-selenium ratio in benzene at 60 \u00b0C diastereomer, the observation of two non-exchanging isomers of 8 in solution suggests that the meso diastereomer of 8 may also be formed. The formation of a single diastereomer of 9 may be attributable to the higher reaction temperature favoring the thermodynamic diastereomer. The structure of 8 is reminiscent of that of the bis(NHC)-stabilized 3,5-dithienyl-1,2,4-trithia-3,5-diborolane obtained by the reductive insertion of three sulfur atoms into the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB double bond of a diborene precursor, with very similar B\u2013S bond lengths and B\u2013S\u2013B and S\u2013B\u2013S angles.9 is reminiscent of that obtained by Tokitoh and co-workers upon irradiation of a boron bis(methylselenide) bound to a very bulky aryl ligand 2H)3C6H2).3 hybridization of the cAAC-supported boron atoms in 9, however, the B\u2013Se bonds (2.068(4), 2.086(4) \u00c5) are slightly elongated and the Se\u2013B\u2013Se angle (109.4(2)\u00b0) is significantly more acute than in [(Tbt)2B2Se3] (B\u2013Se: 1.942(7), 1.926(8) \u00c5; Se\u2013B\u2013Se: 118.8(4)\u00b0).21Like their Bructures show a f8 revealed the presence of another boron-containing species presenting an 11B NMR singlet at \u201311.2 ppm and a single symmetrical cAAC ligand environment in its 1H NMR spectrum. Surmising that this may be a tetrathiadiborinane resulting from a 1\u2009:\u20094 boron-to-sulfur reaction, a scaled-up reaction with this stoichiometry was carried out -stabilized 3,6-dicyano-1,2,4,5-tetrasulfa-3,6-diborinane displaying a cis-arrangement of the cyano and cAAC ligands with respect to the central B2S4 ring, which displays a boat conformation . Attempts to insert a fourth sulfur atom into the isolated 1,2,4-trithia-3,5-diborolane 8 failed to yield 9, suggesting that, like 8, compound 9 forms directly from I, presumably by dimerization of a monomeric [(cAAC)B(CN)S2] intermediate. While 1,2,4,5-tetrasulfa-3,6-diborinanes have been postulated as minor reaction products by both Lappert and later N\u00f6th, based solely on elemental analysis, mass spectrometry and IR spectroscopy data,10 constitutes the first structurally and NMR-spectroscopically characterized B2S4 heterocycle.Multiple recrystallizations of 2B2Se3] from [(Tbt)B(SeMe)2].2]. This monomeric borylene may then dimerize to an electron-deficient diborene (A), which then undergoes the reductive insertion of three atoms of selenium atoms with full cleavage of the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB bond. For path B, the authors proposed a monomeric intermediate resulting from the reaction of \u201c(Tbt)B:\u201d with Se, which dimerizes to a 1,3-diselena-2,4-diboretane and finally inserts the third selenium atom. Regarding path A, numerous attempts on our part have failed to convert borylene I into its diborene relative, compound II, under thermal and/or photolytic conditions. The fact that the three-membered B2E heterocycles 6 and 7 can only be accessed directly from diborene II, but not from borylene I, is further evidence that, despite extensive overlap of reactivity outcomes, I and II do not interconvert.With all these data in hand, it was now possible to reassess the viability of the mechanism proposed by Tokitoh and co-workers for the formation of [(Tbt)B(Tbt)] , path A,I by Lewis bases showed that only a relatively small and strong Lewis base \u2013 the NHC 1,3,4,5-tetramethylimiazol-2-ylidene \u2013 is able to break up the tetramer and generate the mixed base-stabilised [(cAAC)(NHC)B(CN)] borylene.I instead occurs by association of the reactant with the tetramer itself, ultimately causing it to deaggregate into mononuclear intermediates and products. For reactions involving I, the generation of intermediate [[B] PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE] monomers following path B therefore seems the most likely. While the dimerization of via bridging chalcogen atoms provides compounds 4 and 5, the latter do not insert another chalcogen atom to form 8 and 9, respectively, under the reaction conditions employed herein scale\" fill=\"currentColor\" stroke=\"none\">E] yields the B2E3 heterocycles 8 and 9. Similarly, the B2S4 heterocycle 10 would result from the dimerization of [[B]S2].Our previous report on the deaggregation of tetramer d herein . This me11B NMR spectroscopic analysis of the final reaction mixture, the reaction of I with sulfur in a 2\u2009:\u20093 boron-to-sulfur ratio yielded 8 in 70\u201385% selectivity at most, alongside the smaller and larger heterocycles 4 and 10, whereas the analogous reaction with selenium provided 9 in near-quantitative yield. The increased selectivity in the formation of 9 may be ascribed to the possibility of selenium de-insertion, which allows any B2Se2 heterocycle (5) formed in the course of the reaction to lose a Se atom, forming the diboraselenirane 6, which can in turn be converted to 9 (2S2 (4) and B2S4 (10) heterocycles formed in the course of the reaction are inert towards sulfur de-insertion and will therefore remain as by-products. Finally, the fact that the four- and five-membered B2E2 and B2E3 heterocycles are inert towards chalcogen insertion, whereas the three-membered B2E heterocycles may be converted to both the larger B2E2 and B2E3 heterocycles, suggests that ring-expansion only proceeds by insertion of a single chalcogen atom or an E2 unit into any remaining B\u2013B bonds.It is noteworthy that, while the selenium-based reactions were highly selective, those based on sulfur always yielded a mixture of products. For example, based on ted to 9 . In conti) compounds of the same empirical formula, the tetrameric, self-stabilizing cyanoborylene I and its dicyanodiborene relative II, has demonstrated that, while both compounds provide access to the same products in many cases, this occurs via different pathways as shown in This first comparative study on the reactivity of two boron as sole products scale\" fill=\"currentColor\" stroke=\"none\">B double bond, resulting in full B\u2013B bond cleavage is most likely at work.In reactions with dichalcogenides, both products . In the I or II employing a 1\u2009:\u20091 or 2\u2009:\u20093 boron-to-chalcogen ratio yielded the corresponding 1,3-dichalcogena-2,4-diboretanes or 1,2,4-trichalcogena-3,5-diborolanes, respectively. A unique 1,2,3-thiadiborirane could only be accessed from the reaction of diborene precursor II with sulfur in a 2\u2009:\u20091 boron-to-sulfur ratio, whereas the corresponding diboraselenirane was accessible both directly from the analogous reaction with selenium, and indirectly by de-insertion of one selenium atom from the four-membered 1,3-diselena-2,4-diboretane Borylene-based reactions do not proceed (ii) Ring-expansion reactions can only proceed by insertion of chalcogens into existing B\u2013B bonds;(iii) Ring-contraction is possible in the case of boron\u2013selenium heterocycles only by de-insertion of Se atoms.I and II provide confirmation that no Wanzlick-type equilibrium exists between a putative monomeric form of I and its B\u2013B bonded dimer, diborene II, the question remains as to whether this is a result of the extremely stable, tetrameric constitution of borylene I. To date, I and II represent the only existing borylene/diborene pair with the same empirical formula, however, recent advances in the synthesis of borylenes will hopefully enable a more definitive answer to the question of a possible interconversion between [LRB:] borylenes and diborenes. Beyond the interest of such an interconversion from a fundamental point of view, its undeniable potential for providing a new, more reliable route towards hitherto inaccessible diborenes should continue to stimulate research into this area.Although the subtle divergences in reactivity between The authors declare no conflicts of interest.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Three endogenous biothiols in single cells were simultaneously quantified by plasmonic Raman probes and quantitative principal component analysis (qPCA). i.e. cysteine (Cys), homo-cysteine (Hcy) and glutathione (GSH), and quantify their concentrations within single living cells, using one platform of Raman probe. By monitoring the reaction kinetics of biothiols with Raman probes and discriminating their products with a quantitative principal component analysis (qPCA) method, these three biothiols could be simultaneously quantified in both cell lysis and single living cells. The concentrations of Cys, Hcy and GSH in single Hela cells were 158 \u00b1 19 \u03bcM, 546 \u00b1 67 \u03bcM and 5.07 \u00b1 0.62 mM, respectively, which gives the precise concentrations of these three biothiols at a single cell level for the first time. This method provides a general strategy for discriminating each component from a mixed system and has potential for quantifying any biomolecules within an in vitro or in vivo biological environment.Intracellular biothiols mediate many important physiological and pathological processes. Due to their low content and competing thiol-reactivity, it is still an unmet challenge to quantify them within a complicated intracellular environment. Herein, we demonstrated a strategy to discriminate three biothiols, Comparatively speaking, Raman spectroscopy with a very narrow bandwidth (i.e. 1\u20132 nm) and a wealth of fingerprint information can provide much more molecular structural information.via the one probe platform.Over the past few decades, a number of techniques have been exploited to detect biothiols, including high performance liquid chromatography (HPLC),N-(2-cyanobenzo[d]thiazol-6-yl)-5-pentanamide, TA-CBT) obtained by 2-cyano-6-aminobenzothiazole (CBT-NH2) and thioctic acid (TA) via a one-pot procedure, and the chemical structure was fully characterized by 1H/13C NMR (nuclear magnetic resonance) spectroscopy and liquid chromatography-mass spectrometry (LC-MS) analysis with high reactivity, but it reacts with free thiol groups (e.g. GSH) with much lower reactivity. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN) can react with the sulfydryl groups (S\u2013H) of the biothiols to form products with alternative structures scale\" fill=\"currentColor\" stroke=\"none\">N at 2235 cm\u20131, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN at 2235 cm\u20131 and S\u2013H at \u223c2543 cm\u20131,The Raman probe was composed of polyethyleneglycol (PEG)-modified 60 nm gold nanostars (AuNSs) and Raman reporter molecules, denoted as plasmonic Raman probes (PRPs) . Scheme k\u2032mix = [kCys + kHcy(y/x) + kGSH(z/x)][Cys]0, where k\u2032mix is the pseudo-first-order reaction rate constant of a mixture with unknown [Cys]0, [Hcy]0 and [GSH]0, kCys, kHys and kGSH are the second-order rate constants for Cys, Hcy and GSH, respectively, and [Cys]0\u2009:\u2009[Hcy]0\u2009:\u2009[GSH]0 = x\u2009:\u2009y\u2009:\u2009z. From the above equation, [Cys]0, [Hcy]0 and [GSH]0 could be calculated if k\u2032mix and x\u2009:\u2009y\u2009:\u2009z were given, since kCys, kHys and kGSH do not depend on the concentration of the reactants. In this work, k\u2032mix could be experimentally determined by monitoring the reaction kinetics of PRPs with a mixture of Cys, Hcy and GSH, and x\u2009:\u2009y\u2009:\u2009z was obtained by running a qPCA analysis on the Raman spectra of their products scale\" fill=\"currentColor\" stroke=\"none\">N in the PRPs disappeared gradually with the extension of the reaction time, so we could monitor the reaction kinetics by following the Raman band intensity of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN. Firstly, we examined the kinetic changes of the reaction with a relatively large excess of Cys, Hcy or GSH over PRPs in pH 7.4 PBS at 37 \u00b0C. With varying concentrations of Cys, Hcy or GSH, we collected the real-time Raman spectra of PRPs at different time intervals (k\u2032) was calculated on the basis of the exponential fitting of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN over time (k), and then we could calculate the second-order reaction rate constants for the reaction of PRPs with Cys, Hcy and GSH: (2.22 \u00b1 0.02) \u00d7 10\u20134 min\u20131 \u03bcM\u20131, (1.74 \u00b1 0.14) \u00d7 10\u20134 min\u20131 \u03bcM\u20131, and (3.53 \u00b1 0.49) \u00d7 10\u20136 min\u20131 \u03bcM\u20131, respectively (x\u2009:\u2009y\u2009:\u2009z) in a mixed system , Hcy (0.1\u20131 mM) and GSH (1\u201310 mM) reported in previous literature, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN over time was calculated by fitting the changes of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN over time scale\" fill=\"currentColor\" stroke=\"none\">N changes over time in the real-time Raman spectra of PRPs reacted with biothiols from single living cells (k\u2032cell) was calculated are expected to be precisely revealed in the near future.We demonstrated a strategy to discriminate and quantify three endogenous biothiols within single cells by one platform of Raman probe. For the first time, the precise concentrations of Cys, Hcy and GSH were simultaneously obtained at the single cell level. This strategy combining reaction kinetics with the unique qPCA method provides potential for extracting and measuring biomolecules in complex biological environments, 4\u00b73H2O), cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) were purchased from Sigma-Aldrich . Silver nitrate (AgNO3), hydrochloric acid (HCl), ascorbic acid (AA), and trisodium citrate were purchased from Aladdin Chemistry Co. Ltd . Polyethyleneglycol was obtained from Jenkem Technology Co. Ltd . All chemicals were used without further purification, unless otherwise stated.Isobutyl chloroformate, thioctic acid, 4-methylmorpholine (MMP), tetrahydrofuran (THF), 2-cyano-6-aminobenzothiazole, tetrachloroauric acid trihydrate and 50 \u03bcL of 1 M HCl were added to 50 mL of 0.25 mM HAuCl4 solution at room temperature under moderate stirring. Then, 1 mL of 0.5 mM AgNO3 and 0.25 mL of 0.1 M AA were added simultaneously and then stirred for 30 s.AuNSs were synthesized by a seed-mediated growth method.1H NMR \u03b4 10.40 , 8.76 , 8.18 , 7.72 , 3.64 , 3.16 , 2.42 , 1.88 , 1.65 , 1.44 ; 13C NMR \u03b4 171.75, 147.39, 139.76, 136.71, 134.70, 124.71, 120.58, 113.58, 110.92, 56.05, 38.08, 36.28, 34.13, 28.28, 24.73. LC-MS: m/z calcd for C16H18N3OS3+ [(M + H)+]: 364.06; found 364.00. The details are shown in Scheme S1 and Fig. S2\u2013S4.Isobutyl chloroformate was added to a mixture of thioctic acid and MMP in THF at 0 \u00b0C. The mixture was stirred for 30 min, to which 2-cyano-6-aminobenzothiazole was then added, and then stirred at room temperature overnight. After the reaction, the solvent was removed under vacuum, and the residue was purified by flash chromatography on silica gel to yield the desired product Raman reporter as a white yellow solid . The AuNSs (50 mL of 0.1 nM) were first incubated with 100 \u03bcL of 0.05 mM PEG in a shaker for 12 h and then purified by centrifugation at 8000 rpm for 10 min. Subsequently, these PEGylated AuNSs (4 mL of 0.5 nM) were treated with 200 \u03bcL of 0.05 mM reporter and purified using centrifugation at 8000 rpm for 10 min to yield plasmonic Raman probes (PRPs). These PRPs were re-dispersed in phosphate-buffered saline for subsequent use and kept at 4 \u00b0C for long-term storage.via the reaction with different concentrations of Cys, Hcy and/or GSH in pH 7.4 PBS at 37 \u00b0C. All of the Raman spectra were obtained using a Renishaw inVia-Reflex Raman spectrometer equipped with a 785 nm excitation laser.The three products were obtained by reaction with a large excess of Cys, Hcy or GSH over PRPs in pH 7.4 PBS at 37 \u00b0C. By varying the concentrations of Cys, Hcy or GSH reacted with PRPs, a series of samples were prepared in pH 7.4 PBS at 37 \u00b0C. Multiple mixed products were gained 2 and 95% air.The HeLa cells were cultured in Dulbecco\u2019s Modified Eagles\u2019 Medium , supplemented with 10% fetal bovine serum , and 1% antimycotic solution (KeyGEN BioTECH) at 37 \u00b0C in a humidified incubator containing 5% COCell lysis was obtained by cells treated with NP-40 lysis , and then reacted with PRPs. The pH of cell lysis was adjusted by 0.1 M NaOH to 7.4. For single living cells, the cells were pre-cultured in 12-well cell culture plates for 24 h and to these 0.5 nM PRPs were added. After incubation for 0.5 h at 4 \u00b0C, the cells were incubated at 37 \u00b0C for another 2 h to allow the internalization of PRPs, and then washed with pH 7.4 PBS three times. Then the coverslips were placed in a homemade live cell chamber with pH 7.4 PBS maintained stable humidity and 37 \u00b0C temperature.via a commercial software package . The dielectric constant of gold was from Johnson and Christy.x-polarized and y-polarized incident plane wave propagating along the z-axis.The electromagnetic field distribution of the AuNS was simulated by FDTD vs. PC2 scores was utilized to classify the four products.We developed a quantitative principle component analysis (qPCA) method to quantify each of the components in a mixed system. The full proof and details about the mathematical model and calculation strategy are provided in the ESI.There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "We present herein a nickel-catalyzed dicarbofunctionalization of alkenes using readily available organoboronic acids and organic halides in a three-component fashion. N-allylpyrimidin-2-amine is achieved when aryl and methyl iodides are utilized. In contrast, the use of alkyl bromides with \u03b2-hydrogens results in 1,3-hydroarylation or oxidative 1,3-diarylation. Preliminary mechanistic studies suggest an isomerization involving nickel hydride in the 1,3-difunctionalization reactions. On the other hand, the use of alkenyl or alkynyl halides promotes alternative regioselectivities to deliver 1,2-alkenylcarbonation or intriguing 2,1-alkynylcarbonation products. Such 2,1-alkynylarylation is also applicable to N-allylbenzamide as a different class of substrates. Overall, this nickel-catalyzed process proves to be powerful in delivering versatile difunctionalized compounds using readily available reagents/catalysts and a simple procedure.Efficient difunctionalization of alkenes allows the rapid construction of molecular complexity from simple building blocks in organic synthesis. We present herein a nickel-catalyzed dicarbofunctionalization of alkenes using readily available organoboronic acids and organic halides in a three-component fashion. In particular, an unprecedented regioselectivity of the 1,3-dicarbofunctionalization of To this end, the transition-metal-catalyzed dicarbofunctionalization of alkenesvia metal catalyzed C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond isomerization , has also attracted much attention.In a related area of research, remote alkene functionalization, which selectively installs a functionality distal to the initial alkene moiety Our group has been previously interested in the carbofunctionalization of alkenes under base metal catalysis.2.2.11a) and N-allyl aniline (1b) using iodobenzene and phenylboronic acid. Under various nickel-catalyzed conditions, unfortunately, no diarylation product was detected at all or an ester (1e) as the directing group proved futile (entries 3\u20135), we were excited to observe the formation of a desired diarylation product in 23% isolated yield from the use of 1f (entry 6), together with 42% yield of a Suzuki coupling side product. A screening of common phosphine ligands was carried out, from which dppm provided the optimal 47% isolated yield (entry 9 vs. 7 and 8). Here again, Suzuki cross-coupling consumed the reagents to a large extent (40% yield of biphenyl). Intriguingly, the product was determined to be a mixture of 2f and an unexpected 1,3-difunctionalization product 2f\u2032, which represents an unprecedented regioselectivity in alkene difunctionalization. Gratifyingly, when 1g bearing 2-aminopyrimidine was examined next, the 1,3-diarylation product 2g\u2032 was isolated exclusively with an improved yield of 68% (entry 10). Moreover, the undesired Heck and Suzuki products were minimized to 5% and 15% respectively. Other substrates, bearing related directing groups (1h\u2013j), were also examined and suffered from either low conversion or deallylation of the substrate (entries 11\u201313). Different metal precursors were also examined under the optimized conditions. Ni(ii) species in the presence of a reductant proved to be much less effective (entries 14 and 15). Importantly, the use of a palladium catalyst resulted in the deallylation of the substrate and undesired Suzuki coupling without any difunctionalization (entry 16).We initiated our investigation with the dicarbofunctionalization of simple alkenes such as allylbenzene , alkene (3g), ester (3f) and ketone (3h) groups. A higher temperature was required for the ortho-substituted aryl iodides probably due to steric hindrance (3i and 3j). In the case of 4-iodo-benzonitrile, a lower temperature of 85 \u00b0C proved to be important to produce 3d in a good 65% yield, while higher temperature led to much decomposition. Unfortunately, heteroaryl iodides like 2-iodo thiophene, pyridine, and pyrimidine gave only trace amounts of the desired product. A wide range of aryl boronic acids bearing bromo, vinyl, fluoro and trifluoromethyl substituents could also be used to deliver a range of diarylation products 3l\u2013u with good efficiency. Notably, alkenyl boronic acids could also be employed under the same conditions to afford the arylalkenylation products 4a\u2013e in good to high yields, which dramatically expanded the scope of this 1,3-dicarbofunctionalization of alkenes. However, heteroaryl boronic acids led to only trace amounts of the products owing to the decomposition of these boronic acids under the diarylation conditions.With the optimal conditions in hand, we moved on to examining the substrate scope of this 1,3-difunctionalization reaction. Initial efforts were focused on the variation in the substitution pattern of the alkene substrate. Unfortunately, various internal alkenes including l and 1m all fail2.3tert-butyl-p-cresol) or \u03b1-cyclopropylstyrene 8 on the difunctionalization reaction catalyst.Based on these data, we proposed a domino Heck\u2013isomerization\u2013Suzuki reaction pathway for the 1,3-diarylation as shown in 2.45a\u2013f). Besides, dialkenylation could also be realized to deliver 5g.When alkenyl bromides were examined under the same conditions, the related alkenylarylation proceeded smoothly, but with an interesting switch to the 1,2-regioselectivity . Under tvs. 1,3-difunctionalization (r.r.) for most 5 products was >10/1 (as determined by GC-MS), the electronic property of the styryl halides had a significant influence on the regioselectivity. As shown by the comparison of 5c and 5d, the change of the electron-withdrawing CF3 to the electron-donating OMe increased the ratio from 7.7/1 to >100/1. We assume that this 1,2-regioselectivity for alkenylarylation could be attributed to the coordinating effect of the alkenyl unit on nickel scale\" fill=\"currentColor\" stroke=\"none\">C bond from the electrophile would coordinate to nickel and suppress the isomerization. When an electron-deficient alkenyl halide is used, it presumably does not coordinate to nickel so effectively, leading to a higher ratio of isomerization and in turn 1,3-difunctionalization.10It is worth noting that while the ratio of 1,2 n nickel . Once in2.51g with various aryl and alkenyl halides, a three-component reaction between 1g, (bromoethynyl)benzene and PhB(OH)2 was tested under the previously optimized conditions (6a using Ni(COD)2/dppm. The use of alkynyl chloride and iodide also yielded 6a, albeit in lower yields. To our great surprise, both NMR and X-ray structure analysis confirmed an unexpected reverse regioselectivity. In contrast to the 1,2-alkenylarylation in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond while the phenyl groups were added on to the terminals. To further optimize this intriguing transformation, various bisphosphine, monophosphine, phosphite and bipyridine ligands were screened (6a could be improved to 85% by using PCy3 as the ligand and toluene as the solvent. It is noteworthy that a good yield of 77% could be obtained for 6a even in the absence of a ligand in dioxane (<2% in toluene). The coordinative solvent presumably played an important role in stabilizing the nickel species in this case. On the other hand, the combination of Ni(ii) precursors with PCy3 or the use of a Pd complex were much less effective for this 2,1-alkynylarylation (<11% for 6a).Alkynyl halides are versatile and powerful reagents for the introduction of alkynyl groups into organic molecules.nditions . A moderscreened . The yie6b), trifluoromethyl (6c), acetyl (6d) and chloro (6e) substituents on the phenylboronic acids could be well-tolerated. Alkenylboronic acids also worked well to yield 6f and 6g in good yield.The scope of this 2,1-alkynylation was extended to various alkynyl bromides and boronic acids under optimized conditions . Bromo (6h), the perturbation of the electronic property of aryl-alkynyl bromides and the use of alkyl-substituted alkynyl bromide all resulted in no conversion to the desired product. While the previous 1,3- and 1,2-dicarbofunctionalizations necessitate the use of pyrimidine directing groups, we were curious whether the 2,1-alkynylarylation could overcome this limitation. To our excitement, simple N-allylbenzamide 1c was identified to be a suitable substrate for this reaction. As shown in 7 was obtained in a good yield of 56% at a slightly higher temperature. Further exploration of the scope of this transformation is ongoing.This catalytic system, however, showed a narrow scope for the alkynyl reagents. Other than electron-neutral aryl-substituted alkynyl bromides 2 to form B, which featured two distinct carbanion ligands on nickel. Selective insertion of 1g into the aryl/alkenyl\u2013nickel bond led to the formation of intermediate C, which delivered the 2,1-alkynylarylation products through reductive elimination. The key chemo-selectivity in the carbonickelation step was likely due to the fact that nickel\u2013alkynyl bonds are much stronger than the Ni\u2013aryl and Ni\u2013alkenyl counterparts.12It is noteworthy that in the previous 1,3-diarylation and 1,2-alkenylcarbonation reactions, a small amount of Heck product was isolated as the side product. In contrast, no Heck product was observed in the 2,1-alkynylcarbonation. Instead, a small amount of Suzuki product was detected. This observation was further confirmed in the attempted two-component couplings under standard conditions ; the alk2.61g, the 1,3-methylarylation (8a) or 1,3-methyl alkylation (8b) products could be obtained in 41% and 39% yield by using phenyl or styryl boronic acid, respectively. In addition, an unexpected oxidative diarylation product (2g\u2032) was also obtained.Alkyl halides are usually poor electrophiles in transition-metal catalyzed cross-coupling reactions due to their slow oxidative addition and facile \u03b2-hydride elimination.8c) was detected using GC-MS, while 2g\u2032 was obtained as the major product in 35% yield dibromide (B) by the release of ethylene gas.B with organoboronic acid then generated the key organo-nickel intermediate C. The next steps will then follow the pathways for either 1,3-diarylation was attempted under similar conditions. To our excitement, the desired product 8a was successfully obtained, albeit in a moderate yield . On the other hand, the removal of the pyrimidine moiety was also attempted under various conditions, which only led to the cleavage of the aminopyrimidine completely to deliver hydrocarbon products scale\" fill=\"currentColor\" stroke=\"none\">C bond coordination helped to anchor the Ni(ii) intermediate, resulting in less of a tendency towards isomerization and the formation of 1,2-difunctionalization instead. The reaction with alkynyl halides produced a reversed 2,1-regioselectivity, presumably resulting from an alternative sequence of transmetalation followed by selective C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion into the weaker Ni(ii)-carbon bond. Alkyl halides with \u03b2-hydrogen furnished the 1,3- or 1,4-hydrofunctionalization product. In addition, dihaloethane worked as an oxidant under the same conditions to form the oxidative dicarbofunctionalization products. These methodologies can be used for the synthesis of 2-aminopyrimidine motifs as attractive pharmacophores. Current efforts in our laboratory are directed towards the dicarbofunctionalization of more diverse alkenes and enantioselective variants of these transformations.In summary, we have realized the first nickel-catalyzed dicarbofunctionalization of There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A highly oriented 2D nanosheet metal\u2013organic framework membrane is fabricated by a direct growth strategy. 2(bIm)4 (bIm = benzimidazole) ZIF nanosheet tubular membrane, based on graphene oxide (GO) guided self-conversion of ZnO nanoparticles (NPs). Through our approach, a thin layer of ZnO NPs confined between a substrate and a GO ultrathin layer self-converts into a highly oriented Zn2(bIm)4 nanosheet membrane. The resulting membrane with a thickness of around 200 nm demonstrates excellent H2/CO2 gas separation performance with a H2 performance of 1.4 \u00d7 10\u20137 mol m\u20132 s\u20131 Pa\u20131 and an ideal separation selectivity of about 106. The method can be easily scaled up and extended to the synthesis of other types of Zn-based MOF nanosheet membranes. Importantly, our strategy is particularly suitable for the large-scale fabrication of tubular MOF membranes that has not been possible through other methods.Highly oriented, ultrathin metal\u2013organic framework (MOF) membranes are attractive for practical separation applications, but the scalable preparation of such membranes especially on standard tubular supports remains a huge challenge. Here we report a novel bottom-up strategy for directly growing a highly oriented Zn On the other hand, Gascon et al.2/CH4 separation performance.In recent years, as a new member of the 2D family, 2D MOF nanosheets are receiving increasing attention because of their large internal surface areas, uniform channels, (sub)nanometer-sized cavities, thermal stability, and chemical tailorability.In fact, the top-down preparation method inevitably involves the exfoliation step which usually causes some fragmentation and morphological damage of the detached sheets.tubular substrate for H2/CO2 separation by the GO-guided self-conversion of ZnO NPs. As shown in 2 domains, and thus it can act as structural nodes and participate in bonding interactions with MOFs.In our previous study, a 2D ZIF nanosheet membrane was achieved by a self-conversion growth of ZnO nanoparticles (NPs).2(bIm)4 (Zn2(benzimidazole)4) as an example to demonstrate our GO-guided metal oxide self-conversion strategy, as the Zn2(bIm)4 units are considered as subunits of the 2D structure, in which the apices are occupied by Zn atoms and the sides are formed by benzimidazole ligands. Its aperture size, a four-membered ring, is no more than 0.21 nm. Thus, the 2D Zn2(bIm)4 membrane can demonstrate excellent performance in separating H2/CO2 mixtures and have potential applications in some small-molecule gas separations.19We chose Zn2.2.1The commercial porous \u03b1-alumina tubes with 4 mm OD (outer diameter), 3 mm ID (inner diameter) and an average pore size of 100 nm as substrates were purchased from Hyflux Ltd. Co. The tubes were cut into 60 mm lengths and washed sequentially with distilled water and ethanol several times. The tubes were then dried at 100 \u00b0C for 5 h before calcination at 550 \u00b0C for 6 h.3H8O2, EGME, 99.0%), toluene (\u226599 wt%), ammonium hydroxide , N,N-dimethylformamide , monoethanolamine and anhydrous methanol (\u226599.5%) purchased from Sinopharm Chemical Reagent Co., Ltd. Benzimidazole , phthalic acid and 1,3,5-benzenetricarboxylic acid were supplied by Sigma-Aldrich Chemical. Co. Ltd. Zinc oxide nanoparticles were purchased from Beijing Nachen S&T Ltd.The chemicals used in the membrane preparation include zinc nitrate hexahydrate (\u226599.0%), zinc acetate (98.0%), ethylene glycol monomethyl ether with a molar composition of 1\u2009:\u20091\u2009:\u200945\u2009:\u200945 was first prepared for the formation of ZIF nanosheets. Then, the tube with both ZnO NP and GO layers was placed in the synthesis solution at 100 \u00b0C for the desired reaction time. After the synthesis, the membrane was taken out, immersed in methanol for 2 days and then thoroughly rinsed with methanol. Finally, the membrane was dried at room temperature overnight and then stored in a desiccator for later use.According to our previous studies,2.5\u20131) were recorded on a Bruker Equinox 55 spectrometer in KBr plates. Thermal gravimetric analysis (TGA) in a DTU-2 was done in flowing air from 25 \u00b0C to 700 \u00b0C at 10 \u00b0C min\u20131. AFM micrographs were recorded with a Veeco Multimode Nanoscope 3A microscope operating in tapping mode. The MOF samples were applied to a previously annealed mica wafer substrate. Before microscopy inspection, a couple of drops from a suspension of nanosheets in methanol were applied and allowed to dry over the mica substrate. The surface elemental composition was obtained by X-ray photoelectron spectroscopy using a monochromatic Al X-ray source (1486.6 eV).X-ray diffraction (XRD) measurements were performed on a D/max-2400 X-ray diffractometer using Cu K\u03b1 radiation in the range of 3\u201360\u00b0 operating at 20 kV/100 mA. Scanning electron microscopy (SEM) images were obtained with a NOVA NANOSEM 450 SEM (FEI Company) and a Tecnai F30 transmission electron microscope (TEM). The settings of the SEM were as follows: high voltage (HV) 5\u201315 kV, working distance (WD) 5\u201310 mm and spot size 3.0. Fourier transform infrared (FTIR) spectra (4000\u2013400 cm2 (0.29 nm), CO2 (0.33 nm), N2 (0.36 nm) and CH4 (0.38 nm), while the separation of binary gas mixtures was investigated for H2/CO2, H2/N2 and H2/CH4. The experimental setup is shown in Fig. S1 of the ESI.Pi, is defined by following eqn (1): where Ni is the permeation rate of component i (mol s\u20131), \u0394Pi is the trans-membrane pressure difference of i component (Pa), and A is the membrane area (m2). Fi is the flux of component i (mol m\u20132 s\u20131). The ideal separation factor is calculated as the ratio of permeance Pi and Pj in eqn (2).Gas permeances of the highly oriented nanosheet membranes achieved were measured for single gases including H2/CO2, H2/N2 and H2/CH4). The feed gas was constant at a 1\u2009:\u20091 volume ratio. The total pressure on each side of the membrane was atmospheric. Nitrogen was used as the sweep gas on the permeate side for H2/CO2 and H2/CH4 mixtures, while methane was used for the H2/N2 mixture. The gas composition was analyzed using an online gas chromatograph (GC7890T). The separation selectivity \u03b1i/j for the binary gas mixtures was defined as the following eqn (3): where Xi and Xj are the molar fractions of components i and j in the retentate stream which is similar to the feed component, while, Yi and Yj are the molar ratios of components i and j on the permeate side.The separation properties were investigated for equimolar binary gas mixtures . As shown in 2(bIm)4 structure, indicating that this membrane is not oriented. This mainly results from the reason that the nucleation and self-conversion growth of ZnO NPs is able to take place in any direction on the substrate surface in the absence of orientational control, thus resulting in the formation of a layer of randomly oriented multiple nanosheets. Therefore, to date, few continuous 2D nanosheet MOF membranes have been successfully prepared using the direct growth method.For comparison, a thin layer of ZnO NPs coated on a porous substrate was directly converted to grow a ZIF nanosheet membrane in the ligand synthesis solution for 5 h without using any GO. As shown in via some reactions in the alkaline synthesis solution.2(bIm)4 of a highly oriented nanosheet membrane formed by self-conversion of ZnO NPs in a confined space of GO.Here, to obtain an oriented ZIF membrane, a thin layer of GO acting as orientational control was employed to coat the top of the ZnO NP layer supported on the porous substrate to form a sandwich-like structure in which the ZnO NP layer is sandwiched between the GO and surface of the substrate, realizing an oriented growth of a nanosheet membrane. As shown in via coating to form a ZnO NRs@GO layer supported on the substrate for growing a nanosheet membrane under the same synthesis conditions. As shown in To further verify the guiding function of the GO layer on the top of the ZnO NP layer, a layer of ZnO nanorods (NRs), instead of ZnO NPs, was grown on the porous substrate, followed by a thin layer of GO According to the crystallographic data calculated from XRD patterns, the 3D crystalline structure of the ZIF nanosheet was achieved on the surface modified with ZnO NPs .2(bIm)4 consisting of 2D layers is in agreement with that of the substrate. The aperture size of the ZIF is estimated to be 0.21 nm as shown in Fig. S8.The pore direction of the Zn3.22(bIm)4 nanosheet membrane using this bottom-up method. To investigate the role of the GO layer during the preparation of the membrane and further clarify the formation mechanism of the highly oriented membrane, a series of characterizations of the samples were carried out by using FTIR and XPS techniques. The FTIR spectra of Zn2(bIm)4 nanosheets, GO, and Zn2(bIm)4 grown for 9 h (M-9) achieved after the reaction for 9 h are shown in \u20131, representing C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO in carbonyl, and C\u2013O and C\u2013O\u2013C in the epoxy group, respectively, are obviously present.2(bIm)4 nanosheets and Zn2(bIm)4 M-9 have similar FTIR spectra. However, in the spectra of the Zn2(bIm)4 M-9, the intensities of the peaks at 1930 cm\u20131, 1900 cm\u20131 and 1780 cm\u20131 decreased and that of the peak at 470 cm\u20131 increased, showing the formation of a chemical covalent bond of Zn\u2013O between GO and Zn2(bIm)4 because the carboxyl groups and epoxy groups of GO can interact with Zn2+ to form Zn\u2013O bonds.\u20131) related to the coplanar vibration of sp2 bonded carbon atoms and the D band (1340 cm\u20131). The D (associated with the order/disorder of the system) and G (an indicator of the stacking structure) bands of the Raman spectra are the dominant vibrational modes observed in graphitic structures.ID/IG) is often used as a means of determining the number of layers and their overall stacking behavior in a graphene sample. A high ID/IG ratio indicates a high degree of exfoliation/disorder. It is found that the ID/IG value of the Zn2(bIm)4 membrane-9 increased from 0.96 to 1.28 compared with GO. This should be ascribed to the presence of abundant covalent bonds of Zn\u2013O formed by the interaction of C\u2013O and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO of GO with ZnO NPs.The above discussion indicates that the GO layer plays a key role in guiding the oriented growth of the ZnFrom the above analysis of FTIR and Raman spectra, it is obvious that the GO on the top of the ZnO NP layer can interact with ZnO to produce Zn\u2013O covalent bonds in the ligand solution, which favors the nucleation and oriented growth of the ZIF membrane.2(bIm)4/GO composite. The C 1s peaks of GO consist of three components arising from C\u2013C/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, C\u2013O and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC peaks of the Zn2(bIm)4/GO composite become predominant, while the peaks of carbon atoms bonded to oxygen (C\u2013O) are weakened remarkably, implying the conversion of the C\u2013O group into the Zn\u2013O bond by interaction with ZnO in the solution. From 2(bIm)4/GO, the peak in the O 1s spectrum displays a skewing to low binding energy, yet the binding energies of Zn-based bonds of the Zn2(bIm)4/GO composite are larger than those of Zn2(bIm)4. This should be ascribed to the fact that the electron cloud of bonds is shifted from Zn to O atoms, thus confirming that a Zn\u2013O coordination bond between the O of the GO and Zn in Zn2(bIm)4 is formed.2(bIm)4 nanosheets and the formation of the membrane because GO with abundant oxygen groups can play a seed role. Based on the above characterizations and analyses, a possible formation mechanism for the highly oriented Zn-based MOF nanosheet membrane is proposed as indicated in 2(bIm)4 nanosheets should start from the interface between GO and the top of the ZnO NP layer because the C\u2013O/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups of the GO surface easily react with Zn2+ from ZnO NPs in the ligand solution. The ZnO NPs coming into contact with GO will preferentially react with the ligands to generate Zn2(bIm)4 nanosheets. Then, the formed nanosheets act as a seed-like template to induce the conversion of the bottom ZnO NPs into nanosheets downward under the GO restriction. With the reaction time, the nanosheets are gradually produced and then extended in a horizontally oriented direction along the surface of the GO sheet layer to form a continuous nanosheet membrane. Moreover, under the restricted state of the GO layer, the nanosheets in a parallel direction can only grow down toward the ZnO NP layer and stack into a multilayered nanosheet Zn2(bIm)4/GO membrane. Simultaneously the ZnO NPs are also consumed gradually and are finally used up with the increase of the nanosheet membrane thickness. Thus, in this method, the thickness of the ZnO NP layer determines that of the corresponding nanosheet membrane, while the GO layer on the top of the ZnO NP layer plays a key role in restricting and guiding the growth direction of the nanosheet membrane. Both these aspects lead to a highly oriented nanosheet MOF membrane. During the assembly of the nanosheet membrane, the part of the GO layer acting as nanosheets is possibly interweaved with ZIF nanosheets to form a ZIF nanosheet membrane interlaced with GO. Therefore, GO may remedy some defects possibly generated from the nanosheet membrane, thus leading to a high-performance membrane compared with the membrane obtained without any GO layer.To further confirm the reaction between the functional groups of GO and ZnO NPs, XPS spectra for the samples were recorded as shown in 3.32, N2, CO2 and CH4) through the membrane decreased rapidly with increasing the kinetic diameter of gas molecules. The smallest H2 gas showed the highest permeance among these gases, while the permeances of larger gases were far lower than that of H2. This indicated that the as-prepared membrane exhibited excellent molecular sieve performance for H2 over other gases. The ideal selectivities were as high as 106, 126 and 256 for H2/CO2, H2/N2 and H2/CH4, respectively, which are far beyond their corresponding Knudsen selectivities . Moreover, the molecular sieve performance of the M-9 membrane was confirmed by the separation of equimolar mixtures of H2 and CO2, N2 and CH4, and the separation selectivities for H2/CO2, H2/N2 and H2/CH4 at 30 \u00b0C reached about 89, 103 and 221, respectively. This showed that the nanosheet membrane gave excellent molecular sieve performance for H2 over other gases, especially for H2 over CO2, demonstrating the ultrahigh separation function of the nanosheet membrane for small-molecule mixtures. In addition, to further assess the mechanical stability of the obtained membrane, the permeation performances of gas molecules were measured at different trans-membrane pressure drops as shown in Fig. S9.2/CO2 separation selectivity through the nanosheet membrane could almost remain unchanged when the H2 partial pressure increased from 0.5 to 1.5 bar, thus demonstrating excellent mechanical stability. The permeances of all the gases through the membrane are independent of the trans-membrane pressure drop. This implies that the prepared nanosheet membrane is compact and contains no pinholes or defects.To evaluate the entire quality of the oriented nanosheet tubular membrane achieved after the solvothermal growth of 9 h (denoted as M-9), gas permeation performances with single and binary mixtures were measured, respectively. 2/CO2 and the long-term permeation performances of gas molecules for the achieved nanosheet tubular membrane were also investigated to evaluate its thermal and operating stability as shown in 2 and CO2 hardly changed within the temperature range from 30 to 150 \u00b0C. However, both the permeance of H2 and separation selectivity of H2/CO2 slightly increased at elevated temperature as shown in 2 is larger than the aperture size of the nanosheets, this tiny change of pore size can cause a slight increase in the permeance of H2 and hardly has an influence on the permeance of CO2, thus resulting in a slight increase in the separation selectivity of H2/CO2 at elevated temperature.19The influence of temperature on the gas permeance and selectivity of H2/CO2 binary mixture through the membrane. Then, the membrane was heated to 100 \u00b0C and exposed to equimolar H2/CO2 binary gas mixtures for 100 h. After that, the membrane was heated up to 150 \u00b0C and tested for 100 h before cooling down to room temperature. It is seen that there are barely changes for the permeances of both H2 and CO2 during the operating period of 400 h within the temperature range from 30 to 150 \u00b0C. No degradation in membrane performance was observed within the entire test except that there was a slight increase in the gas selectivity of H2/CO2 with elevated temperature because of a tiny increase of H2 permeance. Hence, this long-term permeation result showed that the nanosheet tubular membrane has excellent thermal and operating stability.2(bIm)4 nanosheet tubular membrane with some membranes reported in previous references for H2/CO2 separation was also made. As shown in Table S12/CO2, and the black dashed line represents the 2010 upper bound of microporous inorganic membranes for the separation of H2/CO2 mixtures, our prepared nanosheet membrane far surpassed the trade-off line and had much better separation performance for H2/CO2 than most of the other reported microporous molecular sieve membranes including zeolites, MOFs and polymers, demonstrating that our highly oriented nanosheet membrane is of high quality and has excellent gas separation performance for H2/CO2 mixtures. This suggests that highly oriented nanosheets play an important role in transporting gases through the molecular sieve membranes. Compared to the Zn2(bIm)4 nanosheet membrane with around 5 nm thickness supported on a porous disc by the exfoliation\u2013deposition method reported by Yang's group,2/CO2. The differences may mainly result from the substrate difference for membrane preparation. It is well recognized that the substrate quality seriously influences the membrane quality and its separation performance.2/CO2 gas separation performance.tubular substrate than a planar one. Unfortunately, by this strategy, we have not achieved a much thinner nanosheet membrane yet by now. Nevertheless, the separation performance of our nanosheet membrane is still much higher than those of other molecular sieve membranes reported to date and ZnBTC , were chosen to prepare their corresponding nanosheet membranes as shown in Fig. S11.4.i.e. bottom-up method) to prepare a highly oriented ZIF nanosheet tubular membrane. Excellent gas separation performance with a H2 permeance of 1.5 \u00d7 10\u20137 mol m\u20132 s\u20131 Pa\u20131 and a H2/CO2 ideal separation selectivity of 106 was achieved through our membrane. The method is based on self-conversion of a thin layer of ZnO NPs confined between the surface of a tubular substrate and an ultrathin layer of GO into a nanosheet membrane. The ZnO NP layer acts as seeds and anchoring sites for the membrane growth, while the GO layer on the top of the ZnO NP layer can confine and guide the oriented growth of nanosheets due to the interaction of the abundant carboxylate groups at the surfaces and edges of the GO layer with the Zn2(bIm)4 nanosheets generated at the initial stage. The highly oriented nanosheet membrane achieved is like a window-frame structure exhibiting excellent operating stability. Moreover, this method can also be used for the synthesis of other Zn-based MOF nanosheet membranes such as ZnBDC and ZnBTC. It is believed that this work opens up a simple and scalable direct growth route for achieving a highly oriented nanosheet MOF membrane, especially a tubular membrane for potential industrial applications.In conclusion, we for the first time developed a direct growth strategy (There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Luminescent platinum(ii) complexes show anti-cancer and pH-dependent self-assembly and sustained-release properties under physiological conditions. ii) complexes [Pt(C^N^Npyr) scale\" fill=\"currentColor\" stroke=\"none\">NR)]+ [HC^N^Npyr = 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine)] containing pincer type ligands having pyrazole moieties. These Pt(ii) complexes exert potent cytotoxicity to a panel of cancer cell lines including primary bladder cancer cells and display strong phosphorescence that is highly sensitive to the local environment. The self-assembly of these complexes is significantly affected by pH of the solution medium. Based on TEM, SEM, ESI-MS, absorption and emission spectroscopy, and fluorescence microscopy together with cell based assays, [Pt(C^N^Npyr) scale\" fill=\"currentColor\" stroke=\"none\">NR)]+ complexes were observed to self-assemble into orange phosphorescent polymeric aggregates driven by intermolecular Pt(ii)\u2013Pt(ii) and ligand\u2013ligand interactions in a low-pH physiological medium. Importantly, the intracellular assembly and dis-assembly of [Pt(C^N^Npyr) scale\" fill=\"currentColor\" stroke=\"none\">NR)]+ are accompanied by change of emission color from orange to green. These [Pt(C^N^Npyr) scale\" fill=\"currentColor\" stroke=\"none\">NR)]+ complexes accumulated in the lysosomes of cancer cells, increased the lysosomal membrane permeability and induced cell death. One of these platinum(ii) complexes formed hydrogels which displayed pH-responsive and sustained release properties, leading to low-pH-stimulated and time-dependent cytotoxicity towards cancer cells. These hydrogels can function as vehicles to deliver anti-cancer agent cargo, such as the bioactive natural products studied in this work.Supramolecular interactions are of paramount importance in biology and chemistry, and can be used to develop new vehicles for drug delivery. Recently, there is a surge of interest on self-assembled functional supramolecular structures driven by intermolecular metal\u2013metal interactions in cellular conditions. Herein we report a series of luminescent Pt( PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR1)]Cl complex undergoes aggregation in cancer cells, showing persistent 3MMLCT emission in the cytoplasm.6Self-assembly of \u03c0-conjugated organometallic complexes driven by non-covalent interactions, such as metal\u2013ligand coordination, metal\u2013metal and ligand\u2013ligand interactions, has spurred extensive studies by virtue of the intriguing optical, electronic and chemical properties resulting from these interactions.III(C^N^C)(4-dpt)]OTf , which displayed anti-proliferative and sustained release properties in biological systems.There has been a growing interest in developing metal complexes which target DNA as well as proteins of relevance to cancers.ii) complexes are well documented to have rich luminescent properties, and more recently, to show anti-cancer properties. Indeed, examples of pincer type platinum complexes which display promising in vivo anti-tumor effect in animal model studies have recently been disclosed.ii) complexes (ii) complexes which form poly-electrolytes having hydrogel properties have been reported, an example of which is the dinuclear complex having [Pt(C^N^N) scale\" fill=\"currentColor\" stroke=\"none\">NR1)]+ motifs covalently connected to oligo(oxyethylene) chains.ii) isocyanide complexes containing the C-deprotonated C^N^Npyr ligand (HC^N^Npyr = 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine) scale\" fill=\"currentColor\" stroke=\"none\">NR1)]Cl, [Pt(C^N^Npyr) scale\" fill=\"currentColor\" stroke=\"none\">NR1)]Cl, 1a (1a-hydrogel); (2) its self-aggregation and emission properties in aqueous solutions are pH-dependent; (3) it selectively forms aggregates in low-pH lysosomes in cancer cells; the accumulation of Pt(ii) complexes in lysosomes is suggested to contribute to its cytotoxicity towards cancer cells; (4) 1a-hydrogel exhibits sustained-release cytotoxicity towards cancer cells. Notably, the release activity of 1a-hydrogel can be stimulated by acidic environment; (5) 1a-hydrogel can encapsulate and deliver bioactive natural products, an example of which is the anti-metastatic, berberine.Pincer type platinum(omplexes . Platinuyridine) . Compare)]Cl, 1a , displayii) complexes containing various isocyanide ligands (pyr)Cl] with excess isocyanide ligand at room temperature for 12 h, and were characterized by 1H NMR spectroscopy, ESI-MS and elemental analyses \u2192 \u03c0*(L)) transitions of the C^N^Npyr ligand while the lower energy absorption beyond 375 nm can be assigned to singlet d\u03c0(Pt) \u2192 \u03c0*(L) metal-to-ligand charge transfer (1MLCT) transition.\u03bbmax at 503\u2013507 nm and lifetimes in the range of 7.4\u201315.6 \u03bcs, which are attributed to triplet excited states with mixed 3IL and 3MLCT character.The cyclometalated platinum were examined (1a displays green emission (\u03bbmax = 503 nm) in MeOH. Upon increasing the H2O content, the emission color gradually changes to yellow-orange \u2192 \u03c0*(C^N^N)] excited state. Parallel study using UV/Vis absorption spectroscopy also revealed the appearance of a new absorption band at \u223c375 nm, concomitant with the decrease of absorbance at \u223c350 nm were measured C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR1]+ cation at m/z 546.1 together with a singly charged cation at m/z 1091.2 attributed to the dimeric species (2[M]+ \u2013 H). All these findings are congruent with the formation of Pt(ii) aggregates in water, reminiscent of the previously reported self-aggregation behavior of [Pt(C^N^N) scale\" fill=\"currentColor\" stroke=\"none\">NR1)]Cl.The spectroscopic properties of examined . Complexw-orange . In 80\u20139 99% H2O ; this lom Fig. S4. The cryas anion displaysmeasured . At 298 1a could form hydrogels since the pyrazole moiety supports an intermolecular H-bonding interaction. Upon heating a suspension of 1a in water to 80 \u00b0C, the complex completely dissolved to give a clear solution complexes having different isocyanide ligands, 1b and 2\u20135, could form different nano-aggregates, including nanorods (1b), nanocubes (2), nanospheres (3), and nanofibers by evaporation of their ethanol solutions . Lam, Wong and coworkers reported that low pH (favoring the R2NH form) facilitates intramolecular Pt\u2013Pt interactions in dinuclear [Pt2(C^N^Npyr)2(\u03bc-dppm)]2+ while high pH (favoring R2N\u2013) does not.pyr)isocyanide]+ complexes in phosphate buffered saline solutions having different pHs . Taking 2 as an example, at pH 8, the complex in a mixture of buffer/acetonitrile showed a vibronic structured emission (\u03bbmax = 504 nm) which is typical of the emission of mononuclear [Pt(C^N^Npyr)isocyanide]+ complexes complexes were observed to form aggregates displaying red-shifted emissions at low pH containing single stranded DNA . The anionic phosphate backbone in ssDNA is known to facilitate assembly of cationic Pt(ii) complexes.1a shows a broad low-energy emission peaked at \u223c640 nm at pH 4 in the presence of ssDNA; however, there is no significant low-energy red emission in the absence of ssDNA or in the presence of peptide nucleic acid (PNA) which does not contain the anionic backbone. The broad prominent peak at \u223c640 nm observed at low pH is indicative of the self-assembly of the positively charged 1a ion on the nucleic acid backbone. Upon an increase in pH, the intensity of the long wavelength emission band decreases, which can be accounted for by the disassembling of surface bound Pt(ii) aggregates. It is conceivable that at high pH, deprotonation of pyrazole-H weakens the ionic binding interactions between the surface bound Pt(ii) complex and anionic ssDNA backbone, thus disrupting the intermolecular Pt\u2013Pt interactions along the surface of the DNA backbone. In contrast, the cationic form of the Pt complex in low pH undergoes self-assembly, which is synergistically enhanced by the ionic interactions between the cationic Pt complex and anionic DNA complexes accumulate in acidic lysosomes by fluorescence microscopy. After treatment of HeLa cells with 1a or 2 (10 \u03bcM) for 20 min, green emission could be detected in the cytoplasm or nuclei (Hoechst 33342) (R < 0.15). The existence of both green and orange emission in low-pH lysosomes is consistent with the aforementioned emission measurements in solutions of different pH.Lysosomes are acidic cellular compartments (pH = \u223c5) harboring acid hydrolases for the degradation of obsolete biomolecules and unwanted materials. We tested whether the Pt complexes in lysosomes, HeLa cells were incubated with nigericin, a H+/K+ ionophore that equalizes the pH across the lysosomes and cytosol to pH 8, in phosphate buffered saline (pH = 8), for 10 min after treatment of the cells with 2 for 1 h. As depicted in 2 for 1 h, the emission color in cells with nigericin treatment turned green. The disappearance of the orange-yellow emission after equalizing the cellular pH to 8 further suggests that formation of the intracellular aggregates was induced in acidic compartments such as lysosomes in the cancer cells. Complexes 1a, 1b, 3, 4, and 5 all demonstrated similar intracellular localization complexes in lysosomes was associated with an increase in lysosomal membrane permeability (LMP). HeLa cells were first stained with acridine orange, a cell-permeable dye which gives red fluorescence in acidic lysosomes but exhibits green emission in the cytoplasm and nucleus. The cells were then treated with 1a or 2 at different concentrations.1a or 2 at 5 or 10 \u03bcM led to dose-dependent reductions of red fluorescence, indicative of increased LMP.ii) complexes towards different cancer cells by means of MTT -2,5-diphenyltetrazolium bromide) under similar conditions. Complex 1a (2 \u03bcM) also inhibited anchorage-independent colony formation in HeLa cells under the same conditions.We then tested whether accumulation of platinum(bromide) and naphbromide) assays. Fig. S14. More im1a-hydrogel possesses sustained release properties in buffered solutions of varying pH by UV/Vis absorption spectroscopy. As shown in Fig. S16,1a-hydrogel showed time-dependent release activity at all pHs. It is noteworthy that 1a-hydrogel showed much faster release activity at pH 5 and 3 compared to pH 7.4 and 9. The sustained cytotoxicity of 1a-hydrogel towards HeLa cells was tested in double-chambered Transwell\u00ae 24-well plates (1a-hydrogel (100 \u03bcM) at different time intervals, the upper chambers were removed and the HeLa cells were further incubated in the absence of the hydrogel. After a total of 72 h, the cell survival percentage was quantified by MTT assay. As shown in 1a solution in the upper chamber caused the cell survival rate to rapidly drop to \u223c15% after incubation for 1 h in the lower chambers, and then putting the 1a-hydrogel to carry other therapeutic drugs such as berberine was examined. Berberine is a natural product with extensive pharmacological applications; its potential anti-cancer properties, especially its anti-metastatic property is well documented.1a-hydrogel) could also be formed after cooling a heated mixture of 1a and berberine in water to room temperature in the upper chamber for 4 h and 8 h. The wound of HeLa cells without treatment showed 93% recovery of the scratched area complexes containing C-deprotonated pincer ligands with pyrazole groups, which display self-assembly and anti-cancer properties. These Pt(ii) complexes form aggregates in low-pH buffer solutions, accumulate in acidic lysosomes, increase lysosomal membrane permeability and exert cytotoxicity towards different immortalized cancer cells and a primary cancer cell. One of these complexes, 1a, forms hydrogels in water, which displays sustained and pH-responsive release properties. The anti-cancer active 1a-hydrogel could also be used to deliver berberine, and, in principle, other therapeutic agents to achieve dual therapeutic effects.In summary, we have developed a class of platinum(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "To further our understanding of the role of solution chemistry in directing nucleation processes new experimental and computational data are presented on the solution and crystallisation chemistry of tolfenamic acid (TA), a benchmark polymorphic compound. via dimers and clusters and raise experimental questions about how best to undertake relevant crystallisation studies.To further our understanding of the role of solution chemistry in directing nucleation processes new experimental and computational data are presented on the solution and crystallisation chemistry of tolfenamic acid (TA), a benchmark polymorphic compound. With these, and previously published data, we were able to establish that TA is rapidly fluctuating between conformers in solution with either solvated monomers or dimers present depending on the solvent. Hence, despite the fact that conformational polymorphs can be obtained from crystallisations in ethanol, we found no links between solution chemistry and crystallisation outcomes. We discuss the implications of these conclusions for the nature of the nucleation pathway R,S mandelic and benzoic acids crystallised from alcohols) yield harvested crystals which contain centres of symmetry despite the fact that strong solvation prevents the formation of dimers in the solution-phase.e.g. ethenzamide)In our quest to understand the molecular pathways involved in the nucleation of organic crystals from solutions, significant progress has been made over the last decade.In this contribution we explore further this central question of how much can really be learnt about nucleation from solution-phase experiments and associated computational studies. In particular we consider the essential levels of theory needed in the computational elements of such work; we question how best to characterise the solution species present; we also reflect on the question of how to measure the crystallisation outcomes of experiments so as to shed light on nucleation.et al.twisted or T hereafter) and a second more planar-like . These molecular conformations differ, as seen in \u03c4) which is \u00b174.95\u00b0 in Form I and \u00b1142.63\u00b0 in Form II. Although TA does not contain a chiral centre, its conformers are chiral. Because of the presence of an inversion centre in both polymorphs each crystal structure comprises both enantiomers (hence the \u00b1 sign for \u03c4). The enantiomers can in principle interconvert by rotation about \u03c4, but it is unlikely that this occurs spontaneously due to the high energy barrier. Further to this, it is also apparent that the transfer of the acid proton between oxygen atoms would offer the possibility of the existence of two tautomeric forms. Whilst both tautomeric forms have been studied in this work, the data for the metastable tautomer B is given in the ESIA, found in the solid state, is always the most stable in crystal, liquid and gas phases.As a vehicle for this journey we utilise tolfenamic acid (TA), 2-[(3-chloro-2-methylphenyl) amino] benzoic acid . This isFrom earlier studies,ca. 140 M\u20131 and 31 M\u20131 at 25 \u00b0C by the two techniques. These were interpreted in terms of the existence of carboxylic acid hydrogen-bonded dimers (HBD) in the ethanolic solutions. The reported relationship between supersaturation and the relative appearance of the two forms was then rationalised through the idea that increasing solute concentration creates increasing numbers of dimers and that, based on computational results, the most stable dimer is that in which the molecules adopt the Form I conformation (twisted). Thus the rationale was that at low supersaturations the solutions are rich in monomers displaying the conformer of Form II (planar) whilst at high supersaturations the solutions are rich in dimers displaying the conformer of Form I (twisted). Nucleation was then assumed to dominate the crystallisation outcome and the observations related directly to the solution chemistry.Mattei and Li have made an intensive study of the solution chemistry and crystallisation behaviour of TA Forms I and II.In our exploration of the solution chemistry \u2013 nucleation relations in this system we were first interested in re-examining the conformational energy relationships at varying levels of theory for monomer and dimers in both vacuum and solvent environments. Secondly, we wanted to review and extend the available spectroscopy in order to be clear about the nature of the solution species. Finally we wanted to extend the crystallisation experiments of Mattei and Liet al.Conformer energies were computed in the gas-phase and with various implicit solvation models using GAUSSIAN09.\u03c4 was generated by optimising molecular geometries with \u03c4 constrained every 10\u00b0 between \u2013220\u00b0 to 220\u00b0. All calculations were performed in an SMD solvation model for ethanol at the B97D/6-31+G level of theory.The potential energy surface (PES) of TA about G) is the sum of the electronic energy plus the thermal free energy (G(T) = Ee + Gcorr(T) where Gcorr(T) is calculated from the frequency analysis). Ee was re-computed via a single point energy calculation of the optimised geometries with the same functional but a larger basis set (B97D/def2QZVPP). The use of the large basis sets for this calculation ensures minimisation of the basis set superposition error. To minimise computational costs, the Gcorr term was computed with the smaller basis set B97D/6-31+G model only. The free energies of the dimers were then calculated at different temperatures as the difference between the free energy of the dimer (with either planar or twisted conformation) minus the free energy of two monomers with the planar conformation (since this is the most stable conformer according to our models).Gd(T) = Gdimer-planar/twisted(T) \u2013 Gmono-planar(T) \u2013 Gmono-planar(T).\u00a7\u0394 Similar models have recently been used for the computational study of self-association of various carboxylic acids in solution.20Geometry optimisations and frequency calculations of several dimer and monomer models were computed, free of constraints, at the B97D/6-31+G level of theory in the gas-phase and in the six different SMD solvent models. The Gibbs free energy was purchased from Sigma Aldrich and used without further purification. TA Form II was crystallised by crash cooling an ethyl acetate solution (3.45 g TA Form I and 50.00 g of ethyl acetate) to 10 \u00b0C. Both forms were isolated as pure phases as judged by their powder X-ray diffraction (PXRD) patterns. Ethyl acetate (EtOAc), ethanol and 2-propanol were purchased from VWR International Ltd. (UK), toluene from Fischer Chemicals and deuterated ethanol (EtOD) from Sigma Aldrich (>99.5%D). All solvents were of analytical reagent grade and the molar purities were >99.5%.Powder X-ray diffraction (PXRD) was performed using a Rigaku miniflex X-ray powder diffractometer at a wavelength of 1.5406 \u00c5 controlled by DIFFRACPLUS software from 4\u00b0 to 40\u00b0 with a step size of 0.03\u00b0.\u20131 resolution. The spectra were corrected for the solvent contribution by recording solvent spectra in the same liquid cell and subtracting these from the solution spectra.The FTIR spectra of solutions of TA in EtOD and deuterated toluene were recorded in 0.50 or 1.00 mm thick liquid-sample cells, using a Perkin Spectrum Two spectrometer with 2 cm\u20131 was used.Differential Scanning Calorimetry (DSC) experiments were performed using either a Mettler Toledo DSC 30 instrument controlled by Mettler TC15 complete with a liquid nitrogen cooling system with data analyzed by STARe software v.610 or a TA DSC Q100 with software universal analysis 2000 v. 4.5A. A heating rate of 10 K minThe crystallisation of TA was investigated in crash cooling experiments in toluene, ethylacetate, 2-propanol and ethanol. These experiments were carried out using a 50 mL jacketed vessel with an overhead 2-blade impeller stirring at 200 rpm. Solutions at different concentrations were prepared by dissolving the corresponding amount of TA Form I in 40 g solvent. The solutions were kept at 60 \u00b0C for 1 h to ensure that all the crystals were dissolved completely. 10 mL aliquots of the solutions were then withdrawn and filtered through a pre-heated 0.2 \u03bcm syringe filter, transferred to the jacketed vessel pre-set to the desired crystallisation temperature . The crystals were filtered immediately after nucleation and dried at room temperature for 0.5 h. Each experiment was repeated 5 times and both PXRD and visual observation (colour) were used to identify the polymorphic forms of the product crystals.\u20131 at 10 \u00b0C.Lattice energy calculations, thermal analysis, slurry and solubility measurements were used to determine the thermodynamic relationship between Forms I and II TA see ESI. Forms Iet al.22\u20131 .The relative stability of the TA conformers and the energy barriers for conformational change are key for the understanding of the role played by conformational flexibility during crystallisation. We have computed the stability of the various possible monomeric species of TA using several computational methods and compared the results with previous literature reports in the ESI.\u03c4 in ethanol also for tautomer A and for both enantiomers of TA about the rotatable bond ntiomers . The enevia stacking as presented in Considering the crystal structures of Forms I and II TA as guides, two types of self-assembly modes may be envisaged for TA : (1) thrIt is clear that solvatioIn comparing the relative free energies of HBDs to SDs at room temperature, it appears that HBDs are always preferred in non-polar media while both types of dimer are similarly stable in alcohols and DMSO. Only in water do SDs become more stable than HBDs. With respect to the molecular conformation, dimers with the planar conformer usually appear to be more stable than those with the twisted one. The energy differences, however, are small so dimerization is unlikely to be a cause of conformational restriction.et al.et al.1H-NMR spectra of TA in acetone were recorded at various temperatures. They concluded that the spectra did not show significant variations in the range 210\u2013290 K, indicating that TA does not exist in any favoured conformation under those conditions. Mattei et al.1H-NMR chemical shifts in ethanol with temperature and concentration and observed only very small variations in chemical shifts. This was particularly true as a function of concentration where the observed dependencies were interpreted in terms of molecular dimerisation in solution at increasing concentrations and decreasing temperatures. It was explicitly assumed that this dimer was identical to the H-bonded dimer found in the crystal structures and, following their computational results, that such a solution dimer should bear the twisted conformation. We have reexamined the available experimental data15Proton NMR experiments of TA solutions have been performed by Andersen \u03c4 in 10\u00b0 increments. It is clear from \u03c4 values between 110\u00b0 and 135\u00b0.To understand how the chemical shifts of the different protons change with conformation, we computed NMR chemical shifts for all conformations studied in the PES of TA at values of \u03b4exp = a\u03b4pred + b. This procedure was done twice, first with the monomeric species and second with the dimer species .In order to compare how well the chemical shift predictions for the two conformers of TA reproduce the experimental values, we carried out linear regression on the predicted against the experimental chemical shifts . NMR chea and the good of fitness R2 are presented in \u03c4 and that there is no preferred conformation.The resulting values for With respect to aggregation, the experimental H-NMR chemical shifts of low and high concentrated solutions hardly change see . The cal PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group (\u223c1700 cm\u20131) of TA in ethanol as a function solution concentration. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch mode is a very sensitive probe of carboxylic-acid dimerization. This is partly because of hydrogen-bond induced weakening of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond, but mainly because transition-dipole coupling between the two C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds in a dimer results in a Raman-active symmetric and an IR-active antisymmetric C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch mode which both have frequencies very different from that of the monomer. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch of a dimer has a frequency 40\u201350 cm\u20131 lower than the monomeric C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch . PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch and the dimer antisymmetric C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch), and their relative intensities depend strongly on concentration: at low concentration the monomer peak dominates, at high concentration the dimer peak. In the IR spectra of TA in ethanol scale\" fill=\"currentColor\" stroke=\"none\">O-stretch peaks, but the frequency splitting is only 20 cm\u20131, much less than would be expected for a monomer-dimer difference. More importantly, the intensity ratio of the two peaks is completely independent of concentration, which we varied over more than an order of magnitude scale\" fill=\"currentColor\" stroke=\"none\">O-stretch peaks cannot be due to TA dimerization. We ascribe this difference to a TA\u2009:\u2009ethanol hydrogen-bonding equilibrium scale\" fill=\"currentColor\" stroke=\"none\">O-stretch frequencies corresponding to hydrogen-bonded and non-hydrogen-bonded CO groups, respectively). In fact, a solution of N-methylacetamide in methanol has a similar, concentration-independent two-peak C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO-stretch spectrum due to the formation of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7H\u2013O hydrogen bonds by part of the molecules,\u20131, exactly the same value as observed here.In order to shed further light on this issue we have used FTIR to monitor the band associated with stretching of the C ethanol we obseragnitude . Hence, Our overall conclusion from both the existing NMR data and new FTIR results is that ethanolic solutions of TA are unlikely to contain hydrogen-bonded or stacked dimers, rather the solutions are populated with solvated monomeric species in which the chlorine-containing ring oscillates between the twisted and the planar conformers. The calculations carried out in the previous section also suggest that monomers are preferred over dimers in ethanol solutions.We have proven in the previous sections that TA exists as a monomer in ethanol solutions. But, what species should be favoured for TA in toluene? Intuitively, toluene is a non-polar aromatic solvent so we might expect it to interact more strongly with the aromatic side of the TA molecule but not with the carboxylic acid group. In fact, the calculations in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO band for TA solutions of various concentrations in toluene scale\" fill=\"currentColor\" stroke=\"none\">O-stretching peaks at \u223c1700 cm\u20131 and \u223c1660 cm\u20131 respectively. The intensity of the dimer band at \u223c1660 cm\u20131 increases relative to the intensity of the monomer band at \u223c1700 cm\u20131 in going from a 2 mM to a 4 mM solution of TA in deuterated toluene scale\" fill=\"currentColor\" stroke=\"none\">O-stretch spectrum are due to water-vapour absorption and supersaturations (S) were studied. Detailed results are given in the ESIvia transformation.The polymorphic outcomes of crash cooling crystallisation in toluene, ethyl acetate, 2-propanol and ethanol at different temperatures to the most polar solvent (ethanol) solutions will go from being dimer to monomer rich. Using this insight, together with the data in Firstly it seems clear from both the computations and our comments on the available NMR data that for TA, conformation change is facile so that a crystal nucleating or growing from a monomer rich solution will be insensitive to the existence of the two conformers. Hence each molecule is a potential growth unit and we would expect no conformationally driven outcomes when crystallisation occurs from monomeric solutions. If crystallisation takes place from a dimer-rich solution then the situation is unchanged since the computations suggest that H-bonded dimers (like monomers) show no significant conformational preference. Our analysis shows no experimental evidence from NMR to support the existence of a preferred conformation in ethanol solutions.Considering dimerization, on the one hand ethanol solutions appear to favour the solvation of the acid group and are hence, monomer rich. Toluene solutions, on the other hand, seem to favour the formation of HB dimers. Crystallisation results, however, show that both monomer and HB dimer containing solutions follow Ostwald's Rule of Stages.In considering the creation of crystal nuclei it is worth noting two points. Firstly there is nothing about the solution chemistry that would select a particular conformer for incorporation into a critical cluster. Secondly, while the existence of solution phase hydrogen-bonded dimers between enantiomer pairs could offer a pathway for the creation of the required crystallographic inversion centre, their absence means that both the conformation and the centre of symmetry must be determined at some other stage during nucleation. How this occurs remains an open question. For example, the expulsion of solvent from a disordered aggregate might enable the formation of dimers: with HB dimers a molecule has only to find its mirror image to begin the process of crystallisation. However, if we make an analogy with micellisation, a clustering phenomenon of amphiphiles in polar solvents, then we might imagine that a critical assembly of TA molecules has an aromatic core with acid groups at its surface, making use of the solvating power of the solvent. In this situation the drive towards crystalline order may be initiated by the attainment of stacking interactions. However since stacked dimers as found in Forms I & II comprise only one enantiomer, the centre of symmetry must be created through a subsequent self-assembly process between stacks and this might be seen as less likely. The development of H-bonded dimers and consequent centres of symmetry Finally, we note that other type of aromatic interactions between two TA molecules can be generated by inversion and are observed in Forms III and IV. However, these are less energetically favoured than the SDs considered here as found in Forms I & II. Interestingly, Forms III & IV can only be nucleated on surfaces of non-polar aromatic polymers.12In attempting to understand the relationship between crystal nucleation, solution chemistry and molecular conformation, it may be considered that TA is a suitable benchmark system. Prior to our current work, existing publications suggested that all that should be done on this system had been done \u2013 the crystal structures of two conformationally distinct forms had been reported, phase behavior and solubilities had been measured, crystallisation outcomes were recorded under well-defined conditions and significant investigations of solution chemistry made. All this had been combined with computational chemistry to develop a self-consistent interpretation relating crystallisation to dimerisation and molecular conformation.no energetic preference for the solid state conformers and in which there are no dimers to offer a pathway for symmetry and structural control during the self-assembly process. Importantly, it is worth considering how to proceed both experimentally and computationally when exploring such problems and what data we lack in trying to resolve the molecular issues surrounding the nucleation transition state.Having repeated and extended both experimental and computational aspects of this system, it now appears that there is no link between its solution chemistry and conformational polymorphism. Both additional experiments and higher-level computations have shed new light on the energetics of TA conformers and on the species existing in ethanolic solutions. It now appears that a comprehensive nucleation model for this system must be able to explain how the conformational polymorphs arise from a solution in which there is The initial impetus for study of this system came from the apparently anomalous outcome of the original crystallisation experiments which we were unable to repeat. Crystallisation is a response to an intimate combination of phase equilibria and kinetics and so we are not surprised that different workers, in different labs, using different equipment, chemicals of different purity and ethanol of different water contents should obtain different results. This possibility is well known to those active in the field and reflected in so-called \u2018disappearing polymorphs\u2019.28J and the growth rate constants, k3, of the two polymorphs that determines the experimental outcome. Subsequent workers, however, have continued to use the final, macroscopic outcome of crystallisation experiments to infer structural information about nucleation, ignoring the contribution made by growth.35Perhaps a more important consideration is the question of exactly which crystallisation experiments should be pursued to define the nucleation characteristics of a given system. Workers in the field have become used to the idea that structural characterisation of the final macroscopic crystals in any given experiment provides a link to nucleation. In their 1983 paper concerning the crystallisation of stearic acid polymorphs from cyclohexanone, Sato and BoistelleThe computational results of different workers should not be subject to the same variation in outcomes as the experiments. Our work confirms this but additionally highlights the need to perform calculations at suitable levels of theory in order to achieve the most reliable results, at least for this molecule in which intra- and intermolecular interactions need to be accurately modeled.a priori that a motif present in a crystal structure is also present in solution is a very dangerous assumption to make.Finally we note the difficulty in characterizing uniquely the state of molecular assembly in solutions. Solutions and their dynamic nature are of course fully characterised only in terms of the radial distribution functions describing the environment of the different atoms on the solute/solvent pair. Techniques such as NMR will only be useful in cases where dimers or conformers are particularly stable and abundant. FTIR offers a different view on the state of interactions of specific functionalities with their environment but as yet from the position and intensity of a particular absorbance it is hard to make a unique assignment concerning the intermolecular interactions involved. Certainly, to assume Supplementary informationClick here for additional data file."}
+{"text": "New cyclooctenes have been synthesized under continuous-flow conditions and applied in ring opening metathesis polymerization, providing highly functionalized materials. Functionalized cyclooctenes (FCOEs) are important monomers in ring-opening metathesis polymerization (ROMP). Herein, a new library of disubstituted FCOEs bearing adjacent heteroatoms were synthesized and applied in ROMP. To address the issues associated with the handling of the reactive thienyl chloride intermediate, a two-step continuous flow method has been developed to prepare 5-thio-6-chlorocyclooctene compounds from abundant cyclooctadiene starting materials. These newly synthesized FCOE monomers were subsequently polymerized through ROMP, giving rise to a range of functionalized polymers with high molecular weights. Furthermore, we demonstrated that the thermal properties of these polymers could be fine-tuned by changing the functional groups in the FCOE monomers. We expect that this functionalization-polymerization strategy will enable the preparation of a range of polymeric materials with complex structures. The development of synthetic methods to access functionalized polymers is of considerable interest due to the interesting physical and chemical properties associated with these materials. As a result, extensive efforts have been made to accomplish this task by designing well-tailored monomers for different synthetic methods, such as controlled radical polymerizationvia C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond addition of cyclooctadienes (CODs),9FCOE derivatives are a class of the most widely used monomers for ROMP.In contrast to monosubstituted FCOEs, polysubstituted FCOEs are much less investigated for ROMP reactions. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond addition to prepare FCOEs from cis,cis-1,5-COD . Although the thienyl chloride (RSCl) species has been known for over half a century, the explosive natureIn this regard, we have designed a two-step sequence of thienyl chloride formation/C1.000000,.000000 sp-toluenethiol 1a as the model substrate. In the flow setup, a solution of 1a in anhydrous dichloromethane (DCM) was mixed with SO2Cl2 in anhydrous DCM and introduced into a tubing reactor (R1) immersed in a cooling bath. After the arylthiol was completely converted, as monitored by thin layer chromatography (TLC) analysis, R1 was assembled with the following setup of step II via a T-mixer, allowing the solution from R1 to combine with the COD (3) solution in-line. The resultant mixture was further delivered into the second tubing reactor (R2), which was submerged in another cooling bath, to perform the direct difunctionalization of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond. After the reaction, the mixture was collected and directly analyzed without the isolation of 4a. Upon investigating a variety of reaction parameters, we determined that the synthesis of 4a proceeded in good yield with a 1/1.05/4 ratio of 1a/2/3, and two reactors cooled at 0 \u00b0C and \u201320 \u00b0C respectively (tR) of less than 4 min.4a investigated in 5b\u20135g in about 4 h of reaction time (5b\u20135g in satisfactory yields (55\u201370%). Notably, since aryl halides (e.g. Cl and Br) are versatile functional groups in metal-catalysed cross-coupling reactions, the incorporation of such groups (5c and 5d) would bring in reactivity orthogonal to the substituent on the COE backbone.1 and OMe into the COEs.With the method established for the preparation of 5, a three-step continuous-flow setup has been developed in DCM at room temperature (step IV).5a), an electron-withdrawing group , or a phenyl group , affording a variety of functionalized polymers in high yields (6a\u20136f: 90\u201396% yields) following isolation via a three-time precipitation from methanol. Similar to the Ru-promoted ROMP of alkylthio mono-substituted COEs reported by Noels and coworkers,nC12H25S,6-MeO-COE was used a decreased polymerizing reactivity was observed, providing 6g with 36% monomer conversion in 48 h of reaction time. This is probably due to the increased coordinating effect of an alkylthio group to the metal center compared to that of an arylthiol group. For all examples (5a\u20135g) investigated in Mn,GPC = 106\u2013311 kg mol\u20131, \u0110 = 1.49\u20131.73) were obtained, further confirming the reliability of the ROMP of these new FCOEs EtOAc in petroleum ether as an eluent. During the column chromatography process, 4a underwent a full hydrolysis within 30 min, resulting in the cyclic olefin 7a which has a hydroxy handle. Upon reaction with different electrophiles (step IV), the hydroxy handle was readily connected to a t-butyldimethylsilane , a benzyl , or an acetyl group. Additionally, the chloro group was also converted to an N-heteroatom containing substituent by simply reacting with a nucleophile . Although 3\u20134 steps were employed, compounds 7a to 7f were isolated in good overall yields, and these compounds were characterized by NMR, IR and HRMS analysis scale\" fill=\"currentColor\" stroke=\"none\">C double bond keeps a cis configuration, the SAr group and the morpholine group are trans to each other. This is consistent with the vicinal SR group assisted substitution process, which could proceed through a thiiranium ion intermediate.A solution containing COE 7a\u20137h) were next polymerized in the presence of G2 at room temperature . Although decreasing the monomer/G2 ratio to 20/1 led to complete monomer conversion within 24 h, 8a\u2032 with a much lower Mn,GPC of 6.8 kDa was provided (entry 2), with a \u0110 value similar to 8a . We hypothesized that the improved monomer conversion was due to less of the transition-metal being poisoned by increasing the G2/monomer ratio. When the reaction temperature was increased from room temperature to 45 \u00b0C, poly(FCOE)s were generated with a similar Mn and slightly improved control over the molecular weight distributions . When the third-generation of Grubbs carbene complex (G3) was used to initiate the ROMP of 7b ([7b]/[G3] = 200/1) at room temperature, the corresponding polymer was produced with \u0110 = 1.65 and Mn = 94 kDa at >99% conversion.The newly synthesized FCOE monomers . When the SR1 group was adjacent to a morpholine group instead, polymer 8f was isolated in 82% yield . Both NMR and IR analyses clearly demonstrate that both types of functional group have been successfully incorporated in polymers 8a\u20138f s with high molecular weights, a monomer/G2 ratio of 500/1 was used during the ROMP reaction of the other FOCEs. When 5a and 7f were employed. As shown in Mn,GPC values, while the \u0110 values stayed at a similar level s can be generated at the desired Mn by choosing a proper [M]/[G2] ratio within the investigated range.22To investigate the ROMP of difunctionalized FCOEs at different monomer/G2 ratios, 6a\u20136g and 8a\u20138f were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The summarized results of their glass-transition temperature (Tg) and decomposition temperature (Td) are shown in 6a to 6g, while keeping the MeO group constant, changing the alkylthio side chains to arylthio chains resulted in polymers possessing increased Tg values (6g: \u201356 \u00b0C vs.6a\u20136f: \u201312 \u00b0C to 35 \u00b0C). Among 6b\u20136g, an increased functional group size on the aryl ring or an increased degree of conjugation led to increased Tg values. These results are in agreement with the sidechain influence on the glass transition temperature, as observed by others.8b\u20138e, when the hydroxy side groups were protected with groups larger than methyl, the resultant Tg values were higher than 6b (8b\u20138e: 0\u201318 \u00b0C vs.6b: \u201312 \u00b0C). Replacement of the MeO group with a morpholine group also led to an increased glass-transition temperature (8f: 45 \u00b0C vs.6a: 4 \u00b0C). The thermogravimetric analysis in 6a\u20136g and 8a\u20138f possess Td values ranging from 225 \u00b0C to 350 \u00b0C at 5% weight loss.The thermal properties for the polymers 6e was conducted to demonstrate the preparation of linear polyolefins possessing two different side chains on every seventh and eighth backbone carbon, from the corresponding poly(FCOE)s. The hydrogenation reaction was performed using p-toluenesulfonylhydrazide as the reductant and tri-n-hexylamine as the base with a catalytic amount of 2,6-di-t-butyl-4-methylphenol (BHT) in o-xylene solvent.9 was obtained in 88% isolated yield via precipitation from methanol. As shown in the 1H NMR spectra no new shoulder peaks in the GPC traces, suggesting that the polymer backbone remains intact during the reduction process. Moreover, the hydrogenated polymer 9 has a lower Tg value than 6e s.Finally, the hydrogenation of polymer spectra , during 6e and 9 show: in anhydrous DCM, and fitted to the syringe pump. Another syringe was loaded with a solution of 2 in anhydrous DCM, and fitted to a same syringe pump. The third syringe was loaded with a solution of COD in anhydrous DCM, and fitted to the second syringe pump. Following the setup as shown in 1a and 2 were mixed and reacted in the tubing reactor R1 submerged in a cooling bath. When the reaction was complete, the resultant solution was mixed with the solution of COD and reacted in the tubing reactor R2 submerged in another cooling bath. After the reaction, the resultant mixture was passed through a back-pressure regulator before collection. After reaching steady state (waiting for 12 min), 1.0 mmol samples (10 mL reaction solution) were collected into an oven-dried vial equipped with a stir bar.The experimental procedure for the preparation of via syringe at room temperature. When the reaction was completed, as monitored by TLC analysis, the mixture was treated with DCM (150 mL) and NaHCO3 saturated aqueous solution (20 mL). The separated organic layer was washed with brine two times (2 \u00d7 10 mL), dried over Na2SO4 and then concentrated under vacuum. The residue was purified by column chromatography (eluting with 0\u20132% EtOAc in petroleum ether) to afford 5a in 64% isolated yield.Anhydrous MeOH (10 mmol) was added into the vial 5a (0.5 M) in anhydrous DCM under N2. The G2 compound solution was added via micro syringe into the vial at room temperature. After stirring for 24 h, the mixture was concentrated and then added dropwise into MeOH with vigorous stirring. The solid compound was collected and re-dissolved in a minimal amount of DCM. The precipitation procedure was repeated three times in total to afford the target product. The produced polymer was characterized by 1H NMR, 13C NMR, FT-IR, GPC, DSC and TGA analysis.An oven-dried vial equipped with a stir bar was charged with a 1.0 mL solution of There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Quantitative dihydroboration of cyclic dienes leading to new, tunable boron-containing hydrocarbon polymeric materials. 11B NMR to identify the actual boron species formed, as opposed to the most common analysis of the resultant oxidation products. Quantitative dihydroboration was achieved for the full range of cyclic dienes investigated including dienes, which were previously reported to be resistant to dihydroboration, leading to the formation of new boron-containing polymeric materials. The conditions favoring dihydroboration are reported as well as full characterisation of the materials. Furthermore, a hydroboration cascade mechanism is proposed for the formation of such boron-containing polymers, supported by both experimental and theoretical data.The hydroboration 1,3- and 1,4-cyclic dienes has been systematically investigated. The behavior of such dienes towards mono and dihydroboration was monitored directly by We found the exceptional resistance of smaller rings towards dihydroboration, even in the cases where excess hydroborating agent was used, rather puzzling. Although a diene is certainly a more electron rich system when compared to an alkene, the non-conjugated nature of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond present in the formed monohydroboration products could potentially compel them to be more reactive than the starting diene, on account of the non-conjugated double bond compared to the initial system. Additionally, both the cyclic diene and the borane reagents (both the starting borane and the formed products) are capable of undergoing further hydroboration reactions. Thus, one might expect the formation of polymeric and/or network materials, as was previously reported in the case of straight-chain dienes31It is possible that dihydroboration of cyclic dienes to generate diols has not been thoroughly explored as a result of the strong and contradicting conclusions drawn in a series of published studies by H. C. Brown i.e. by identifying the boron species present.1 was used.26As a result of our interest in preparing substituted diboranes, we aimed to systematically investigate the hydroboration of cyclic dienes in order to identify the suitable conditions for dihydroboration of smaller rings. While the results and conclusions by Brown 1 utilized by H. C. Brown et al.3\u00b7SMe2vs. B2H6 prepared from NaBH4 and BF3\u00b7OEt2).We first focused our attention on the number of equivalents of diene present in the reaction, as the large excess of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds were only observed in entry 1, while the borane starting reagent was fully consumed. Analysis of the filtrates obtained for entries 2\u20134 , revealed large amounts of unreacted starting borane, seen as a quartet at \u201320 ppm in the 11B NMR. Furthermore, the absence of any C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds in the 1H NMR for these entries suggested that full dihydroboration has taken place utilising all C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds.In order to fully characterise the reaction, the precipitates were collected by filtration (under nitrogen) and the filtrates were analysed by NMR. All B\u2013H bonds appeared to undergo hydroboration, as unsaturated Cin situ, the same trend was observed gas production. This was achieved by either adding BF3\u00b7OEt2 to a solution containing both NaBH4 and 1, resulting in a slow release of the desired gas (as the reaction proceeds via the formation of the NaBH4BH3 complex first), or by addition of NaBH4 to a solution containing both BF3\u00b7OEt2 and diene 1, which resulted in the instantaneous release of diborane(6). As in the case of BH3\u00b7SMe2, all reactions yielded a white precipitate, with only NaBF4 being observed in the filtrate, appearing at approximately \u20130.4 ppm in the 11B NMR, indicating reaction completion.When the source of borane was changed to diborane(6), produced rved see . As dibo3\u00b7Lewis base adducts,4 serving as indirect evidence that boron hydrides are present in these materials indicating the presence of trapped solvents, which was confirmed by solid state NMR. Moreover, this strongly suggested the formation of a polymeric network. Addition of Lewis bases such as PPh2.1.1\u20131), terminal B\u2013Ht (2600\u20132500 cm\u20131), bridged B\u2013Hb (1600\u20131500 cm\u20131) and B\u2013C (1200\u2013800 cm\u20131) bonds and the absence of any C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds (1800\u20131700 cm\u20131). All solids analysed resulted in similar spectra despite originating from a number of different reaction conditions. The FT-IR spectra of four selected materials are shown in vide infra). The B\u2013Ht bond stretches could indicate either presence of a R2BHBH3 species (see 2BH)2 species and unreacted borane or diborane(6) starting material, due to R2BHBH2R or RBH2BH2R, or unbridged R2BH species or even due to BH3 trapped inside the material network. The latter option, however, could be dismissed based on solid state NMR data scale\" fill=\"currentColor\" stroke=\"none\">C double bonds in both the filtrate and the solid confirmed that full dihydroboration had taken place.Analysis of the materials by FT-IR under anaerobic conditions indicated the presence of C\u2013H .8 remained soluble in ether and could be isolated upon concentration followed by recrystallisation (+81 ppm in solution 11B NMR). The dominant formation of dicyclohexylborane 9 (R2BH)2, especially at the earlier stages of hydroboration, suggested that it was the kinetic product, which could be converted to the thermodynamic tricyclohexylborane 8 over time as opposed to the instantly pyrophoric and highly unstable tricyclohexylborane 8. The direct dependence on the rate of reagent addition towards the formation of kinetic product 9vs. thermodynamic product 8 led to materials with different physical properties and reactivities. For example, materials which are mainly consisted of the kinetic products bearing the boron hydride bridges are highly moisture sensitive but not pyrophoric. When these materials where exposed to moisture they transformed from solid to liquid clearly breaking the B\u2013H\u2013B bridges which hold the insoluble polymeric network together. We are currently investigating the applications of these materials especially as instant moisture scavengers.Three equivalents of cyclohexene 2.1.311B NMR analysis of model compounds 8 and 9 indeed allowed for deconvolution and assignment of the NMR spectra obtained from the white insoluble materials prepared by hydroboration of cyclohexadiene 1. As seen in 11B resonance from tricyclohexylborane 8 has a relatively broad line shape due to large anisotropic interactions , which are not efficiently reduced by magic angle spinning at 10 kHz. The isotropic chemical shift of +82 ppm fits well with the value measured in solution 11B NMR scale\" fill=\"currentColor\" stroke=\"none\">C bonds critically points to quantitative dihydroboration of 1 using a variety of borane sources and reaction conditions.The remaining signals appearing at approximately +50 and +18 ppm most likely correspond to other boron hydride species such as RR2BHBH2R . This is2.1.412 was observed in the absence of any unsaturated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. The formation of this alcohol could be attributed to a diborane elimination side reaction similar to what is shown in 10, is highly unlikely in the absence of a driving force, such as a Lewis base. Perhaps, SMe2, THF (if present), diglyme or even a species formed during the reaction could mediate such an elimination. Protonolysis of the \u03b1-boron atom, in the 1,2-disubstituted diborane case, could also possibly lead to the formation of an oxidised alkylborane which resembles a carboxylic acid ([(RO)2B(OR)OH]\u2013) thus eliminating one of the boron atoms and replacing it with a hydride. However, we believe that this is unlikely due to the large amounts of cyclohexanol 12 observed in some cases and the highly uncontrolled nature of this hydroboration system leading to a statistical mixture of 1,2-, 1,3- and 1,4-substitution patterns. Furthermore, during our studies we observed that \u03b2-hydride elimination of diboranes is possible, however, such an elimination followed by oxidation would not result in the formation of cyclohexanol but rather the unsaturated compound 2-cyclohexene-1-ol 2. Finally, elimination reactions caused by oxidation would also produce alcohols with C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds rather than cyclohexanol and therefore must also be discounted. We are currently further investigating the mechanism of this elimination.Basic oxidation of these insoluble materials with hydrogen peroxide, adapted from literature procedures1 combined with the trifunctional nature of BH3 and the energetic stabilisation gained from the formation of B\u2013H\u2013B bridges is akin to an A2 + B3 step-growth polymerisation leading to insoluble, crosslinked networks. Moreover, the solids readily transform into liquids upon exposure to air, further suggesting that oxidation leads to facile disruption of the borane-hydrocarbon polymeric network. Finally, the dependence of the materials' physical appearance on the reaction solvent (glassy in THF and a white powder in diglyme) together with the high solvent content present in these materials are also indicative of the formation of a polymer network.Several attempts were made to avoid the formation of the insoluble precipitates including lowering the reaction temperature (\u201378 \u00b0C), decreasing the concentration, or carrying out the reaction in non-ethereal solvents, known to considerably slow down the rate of hydroboration, such as DCM.2.2via a cascade of hydroboration reactions. Detailed inspection of the boron species formed during hydroboration by NMR gave rise to the following proposed mechanism shown in 1 undergoes monohydroboration to form either an allyl RBH2 species 13a or homoallyl RBH2 species 13b. The ratio of 13a to 13b is likely to be highly dependent on the particular diene structure and is beyond the scope of this study. However, it was expected that the allyl RBH2 species 13a is slightly more stable compared to the homoallyl 13b on account of conjugation with the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. Indeed, during our calculations we found that the BH2 group is stabilised in an axial position, when SMe2 is absent, by interactions with the adjacent double bond that partly delocalises to the boron 2p orbital , the equatorial conformation is preferred. It is worth noting, that the formed RBH2 species most likely exist as dimers, which contain B\u2013H\u2013B bridges providing substantial stabilisation,We believe that these materials are polymeric species formed 1 and borane. This was especially evident on account of the unreacted borane observed in solution after the consumption of all C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds, entries 2\u20134 in 1 leads to the formation of an isolated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, which was observed to be highly reactive (at least under our conditions) compared to the conjugated starting material 1, leading to a cascade of hydroboration reactions and concomitant formation of a cross-linked polymeric network as the monohydroboration species continue to react preferentially.Once hydroboration occurs, both the monohydroboration and dihydroboration species are much more reactive than the starting materials, conjugate diene 3 (or substituted RBH2 species) by breaking the solvent\u2013borane adduct or the borane dimer. The second step is the addition of the BH3 to the double bond and usually has a smaller barrier.3 intermediate is stabilized by short-lived intermediate complexes formed with the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond containing reaction partner. We found that the barrier of the first step is reduced from +26.1 kcal mol\u20131 to +14.6 kcal mol\u20131 using BH2-cyclohexene, to +15.0 kcal mol\u20131 using 1,3-cyclohexadiene 1, and to +13.8 kcal mol\u20131 using cyclohexene are used with electron-donating R groups, even when the free RBH2 is not further stabilised by adduct formation with a solvent molecule or a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. With R = cyclohexyl (or cyclohexenyl), the barrier to generate a free BRH2 is +13.3 kcal mol\u20131 , which is +12.7 kcal mol\u20131 smaller than for the dissociation of the BH3\u00b7SMe2 complex can further react rapidly and hydroborate another cyclohexadiene molecule . It is worth noting that the second hydroboration reaction can produce eight distinct diborane cyclohexane isomers in general if the chair-boat conformational change is not hindered, and many more in the conformationally restrained polymers. The formation of each isomer has different potential reaction mechanisms and corresponding rates. Interestingly, the intermolecular hydroboration, with the bridged cis-1,2-cyclohexane scale\" fill=\"currentColor\" stroke=\"none\">C bond, in relation to the sterically demanding group, was crucial in the formation of these materials, which were not limited by ring size.Intrigued by the results of our study on 1,3-cyclohexadiene, we expanded the substrate scope to include a range of different cyclic dienes including: \u03b1-terpinene, 1,3-cycloheptadiene, 1,3-cyclooctadiene, 1,3,5,5-tetramethyl-1,3-cyclohexadiene, \u03b3-terpinene, 1,4-cyclohexadiene, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, 1,5-cyclooctadiene and the acyclic 2,3-dimethyl-1,3-butadiene as a control and direct comparison to the reported polymer structures (see ESI S9, Fig. S493et al.To conclude, boron containing polymers form when cyclic 1,3- or 1,4-dienes, free of sterically demanding groups are fully hydroborated, irrespective of the cyclic diene size, borane equivalents and mode of addition. When steric hindrance is present or cyclic borane species are favourably formed, as for example when straight chain of 1,5-dienes are utilised, clear solutions are observed. These materials were characterised by solid state FT-IR and NMR and were found to consist of boron hydride bridged species due to stabilisation reasons and the synthetic time scale utilised. Further supported by oxidation analysis, it was clear that hydroboration proceeds further than the monosubstituted borane adducts to form higher substituted, more stable, bridged borane species. Therefore, our results are in disagreement with the published conclusions on the study of dihydroboration of cyclic dienes by H. C. Brown Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file."}
+{"text": "Amination of a silylated ester generates an intermediate urea that transfers an aryl ring to the aminated centre and cyclises to a hydantoin. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond of an azocarboxamide, generating a N-amino-N\u2032-aryl urea derivative of a substituted aminoester. Treatment with a base forms an ester enolate which undergoes arylation by intramolecular migration of an aryl ring to the \u03b1-position of the ester. The product undergoes ring closure to a hydantoin, which may itself be deprotected and functionalised. Aryl migration is successful with rings of various electronic character and with esters bearing functionalised and unfunctionalised chains, and the products have features in common with several bioactive compounds.5,5-Disubstituted hydantoins, formally the cyclisation products of quaternary amino acids, were formed connectively from simple ester-derived starting materials by a one-pot tandem method. Amination of the silyl ketene acetal derivative of a methyl ester takes place by silver-catalysed addition to the N Hydantoin rings, formally the cyclocarbonylation products of amino acids, are found in a number of medicinally significant molecules .1,2 For 6Methods for the synthesis of substituted hydantoinsWe have shown that intramolecular migration of an aryl ring to the \u03b1-position of an amino acid-derived urea can provide a general method for making substituted hydantoins20N\u2032-aryl migration to the \u03b1-position of the resulting ester followed by ring closure would give a hydantoin.Our initial plan for a direct route to structurally diverse 5,5-disubstituted hydantoins is illustrated in Three major challenges need to be overcome. Regioselective addition of the silyl ketene acetal to the azocarboxamide must lead to a 2-ureido ester to allow the subsequent aryl migration step. Secondly, the enolate of the product must undergo rearrangement rather than any other alternative reaction (such as substitution or elimination), and finally the product must cyclise to a hydantoin. All these steps ideally should occur in a single, tandem process.1 were made by acylation of hydrazine with N-methyl-N-arylcarbamoyl chloride followed by oxidation with NBS.1a and the silyl ketene acetal 2a with AgOTf (20 mol%) in dichloromethane gave the addition product 3 in 68% yield . Increasing the amount of KHMDS to 3.0 equiv. gave clean product 4a in 75% yield (entry 4).We started by exploring the amination step with a symmetrical azodicarboxamide to allow us to study the viability of the rearrangement while avoiding issues of regioselectivity. Silver-catalysed aminations of silyl ketene acetals were known using azodicarboxylates,8% yield , entry 11b\u2013g were made, and likewise treated with silyl ketene acetals 2a and 2b .The products S see ESI, we wereioisomer , entry 1N-Boc-protected aminohydantoin 7a (entries 3\u20135) took place, in parallel with the results seen using the symmetrical aminating agent 1a. With 2.0 equiv. of KHMDS, warming the reaction to \u201340 \u00b0C for 2 h, hydantoin product 7a was formed in 20% yield (entry 3), increasing to 72% yield on warming to \u201320 \u00b0C (entry 5). Other unsymmetrical aminating agents were also explored, including N-benzoyl, N-tert-butyl-carboxamido and N-methyl-N-tert-butyl carboxamido substituted azo compounds. Although intermediate aminated products corresponding to 6 were obtained, treatment with the base led only to decomposition.When KHMDS was added directly to the crude reaction mixture containing the amination product, arylation and cyclisation to the 5 and silyl ketene acetals 2 and the antibacterial drug nitrofurantoin (9b). Alternatively, the N\u2013N bond of the product could be cleaved to reveal the parent hydantoins 10. Several methods were screened for this transformation, and we found that treatment of a selection of products 7 with sodium nitrite in 3\u2009:\u20091 acetic acid/1 M HCl at 110 \u00b0C scale\" fill=\"currentColor\" stroke=\"none\">O stretching absorptions at 1745 cm\u20131 (ester), 1720 cm\u20131 (carbamate) and 1678 cm\u20131 (urea). A transforms initially into an intermediate which we assign as the enolate B, consistent with the disappearance of the ester C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretch at 1745 cm\u20131, and the appearance of peaks we assign to the enolate function at 1640\u20131660 cm\u20131 plus a peak at 1604 cm\u20131 corresponding to the anionic carbamate. The enolate evolves to a species that has C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching absorptions at 1764 cm\u20131 and 1710 cm\u20131, typical of a hydantoin,\u20131. We assign these peaks to species D, the conjugate base of the ultimate product 7i. The rearrangement of B to D presumably passes through an undetectable transient intermediate C that cyclises rapidly to D. Evidence from related reactions suggests that the formation of the new C\u2013C bond and breakage of the old C\u2013N bond during the formation of the proposed intermediate C are to some extent concerted.The course of the reaction between model substrates PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond of a new class of unsymmetrical azocarboxamides, and the arylation takes place by base-promoted intramolecular N to C migration within the N\u2032-aryl urea linkage that results from the amination step. The hydantoin then forms directly from the product of enolate arylation. In situ infra-red spectroscopy reveals four successive species on the reaction pathway from the amination step to the hydantoin ring closure. The one-pot protocol allowed the connective synthesis of a range of 5,5-disubstituted hydantoins bearing electronically diverse aryl substituents, compounds which have potential applications in the construction of biologically active molecules.In conclusion, 5,5-disubstituted hydantoins may be formed by a tandem amination-intramolecular arylation sequence of silyl ketene acetals. The amination entails silver-catalysed regioselective addition to the NThere are no conflicts of interest to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "An efficient aerobic unactivated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleavage process was achieved, in which the succinimide or glutarimide derivatives could be prepared directly from alkenyl amides. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond double cleavage are always attractive but very challenging. We report herein a chemoselective approach to valuable cyclic imides by a novel Cu-catalyzed geminal amino-oxygenation of unactivated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. O2 was successfully employed as the oxidant as well as the O-source and was incorporated into alkenyl amides via C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleavage for the efficient preparation of succinimide or glutarimide derivatives. Moreover, the present strategy under simple conditions can be used in the late-stage modification of biologically active compounds and the synthesis of pharmaceuticals, which demonstrated the potential application.The transformations of unactivated alkenes through C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond cleavage. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleavage,via chemoselective C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond cleavage would be highly promising to produce succinimides in the presence of oxygen (ii)-catalyzed intramolecular aza-Wacker-type cyclization. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleavage was successfully achieved but in two steps. DABCO was required as a base with the formation of \u03b3-lactam products. To the best of our knowledge, the chemoselective cleavage of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds in alkene-tethered amides for cyclic imide synthesis has not been accomplished yet.Recently, Of oxygen . To dateN-methoxy alkenyl amide 1a. After a lot of experiments, we were surprised to find that the unactivated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond could be cleaved with the incorporation of one oxygen atom using O2. Encouraged by the copper catalyzed olefin amino-oxygenation which delivered 2a in 47% yield (Ligand II) as the ligand the unactivated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond geminal amino-oxygenation reaction in toluene proceeded well and produced the desired succinimide product 2a with excellent efficiency while substrates bearing bulky groups showed poor conversion (2d and 2e). When a hydrogen atom (2f) or benzyl group (2g) was attached to the amide nitrogen, the reaction did not work. The reason is that the alkyl-metal intermediate formation might be favored with the assistance of alkoxy protecting groups.2h\u20132o), producing polysubstituted and spiro-succinimides in moderate to good yields. It is noteworthy that the reaction could contain one of the identical allyl groups specifically to give the allylic imide in 44% yield (2o). The mono-methyl or benzyl substituted enamides were also tolerated, and the desired products could be obtained in fair yields (2p and 2q). To our delight, the vinylcyclohexane derived enamide underwent the process smoothly to afford the corresponding imide 2s. 2-Vinylbenzamide was also compatible to give the synthetically important phthalimide 2t albeit the efficiency is a little bit low because the conjugated alkenes would undergo unwanted oxidation. Unfortunately, the alkene-tethered amide without alkylation of the backbone did not work. Notably, the glutarimide derivatives 4a\u20134d were also obtained in moderate yields with hex-5-enamides as an anti-inflammatory, antipyretic and analgesic agent, could deliver succinimide nditions . The stri and methsuximide ii , which possesses antiepileptic effects. This method avoids the use of highly toxic hydrocyanic acid in industrial production. Similarly, the methsuximide 17 could also be obtained from succinimide 15 in good overall yield.Furthermore, our strategy can be applied to the synthesis of two pharmaceutical compounds ethosuximide imide ii . As show18 could be obtained in 87% yield, with the formation of 2a in only 10% yield scale\" fill=\"currentColor\" stroke=\"none\">C bond cleavage, 2-pyrrolidinone 19 was employed under standard conditions. The formation of 2r with some unconsumed raw materials compared with the results in 18O2 delivered the labeled succinimide [18O]-2a in 80% yield (67% 18O) due to the exchange with H2O is oxidized to copper(ii) by O2 in the initial step. Then, copper(ii)-catalyzed alkene cis-amidocupration affords an unstable organocopper(ii) intermediate B. Primary radical C, which could be trapped by TEMPO enolate G which undergoes formal [2 + 2] cycloaddition with another molecule of oxygen to give the 1,2-dioxetane Jvia radical species H and the cyclic peroxo intermediate I.2a and release carbon monoxide.Based on previously reportedby TEMPO , is subs TEMPO B. could novia a chemoselective cyclization/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleavage processes that revealed an efficient approach to polysubstituted succinimides and glutarimides. Our reaction exhibited good functional group tolerance under simple conditions. The success of this protocol in the late-stage modification of biologically active compounds and the synthesis of pharmaceuticals would motivate further exploration of the transformations of unactivated alkenes.In summary, we developed a novel molecular oxygen mediated geminal amino-oxygenation of unactivated olefins in alkene-tethered amides The authors declare no competing financial interest.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Crystalline and porous covalent organic frameworks (COFs) with donor-acceptor moieties in their backbone are utilized as initiators for visible light induced radical polymerization. The COFs are efficient photoinitiators, maintaining their structural integrity for several cycles. b]thiophene-2,5-dicarbaldehyde or -5,5\u2032-dicarbaldehyde linkers are presented. The resulting crystalline and porous COFs have been applied as photoinitiator for visible light induced free radical polymerization of methyl methacrylate (MMA) to poly-methyl methacrylate (PMMA). These results pave the way to the development of robust and heterogeneous systems for photochemistry that offers the transfer of radicals induced by visible light.Covalent organic frameworks (COFs) are promising materials for applications in photocatalysis, due to their conjugated, porous and chemically stable architectures. Alternating electron donor\u2013acceptor-type structures are known to enhance charge carrier transport mobility and stability in polymers and are therefore also interesting building units for COFs used as photocatalysts but also as photoinitiator. In this work, two donor\u2013acceptor COFs using electron deficient 4,4\u2032,4\u2032\u2032-trianiline and electron rich thiophene-based thieno[3,2- Covalent organic frameworks (COFs) have recently received increasing interest due to their intriguing properties such as low density, high porosity, good crystallinity and the possibility to introduce a range of organic functional moieties into chemically stable frameworks.To further improve the catalytic activities, strategies such as introduction of heteroatoms (N and S),b]thiophene-2,5-dicarbaldehyde or -5,5\u2032-dicarbaldehyde , respectively, in presence of 6 M acetic acid (0.5 mL) and mesitylene/dioxane (3 mL) as the solvents [Section S2, ESI13C solid-state cross-polarization magic angle spinning nuclear magnetic resonance (CP/MAS-NMR) spectroscopy, N2 sorption analyses, scanning electron microscopy (SEM), in situ as well as ex situ electron paramagnetic resonance (EPR) spectroscopy, and ultraviolet-visible spectroscopy (UV-vis) analyses.Considering the beneficial properties of donor\u2013acceptor based materials for charge generation, mobility and stability, we have attempted the synthesis of donor\u2013acceptor COFs as photoinitiators for visible light induced free radical polymerization .35,36 TT\u03bb = 1.5418 \u00c5) was performed to assess the crystallinity of the as-synthesized COFs. The PXRD patterns for TTT\u2013DTDA and TTT\u2013BTDA are dominated by an intense reflection in the low-angle region, at 2.68 and 2.52 2\u03b8 degrees for TTT\u2013DTDA and TTT\u2013BTDA, respectively, which can be assigned to the (100) facet of a primitive hexagonal lattice (\u03b8 degrees for TTT\u2013DTDA and TTT\u2013BTDA COFs that can be assigned to the (001) facet, confirms the formation of two-dimensional (2D) COFs in a crystalline and \u03c0\u2013\u03c0 stacked form. The structural models for TTT\u2013DTDA and TTT\u2013BTDA were constructed by generating the probable 2D hexagonal layers with hcb topology with either eclipsed (AA) or staggered (AB) stacking arrangement analyses with Cu K\u03b1 radiation scale\" fill=\"currentColor\" stroke=\"none\">N bonds, confirming the condensation reaction of aldehyde (TTT) and primary amines (DTDA or BTDA). The signals at \u223c110, 125, 130 and 138 ppm can be ascribed to the carbon atoms of the phenyl groups, while the sharp peak at \u223c165 ppm is attributed to the carbon atoms of core triazine ring from TTT linkers in the COFs, validating the presence of intact triazine moieties in the backbones. The formation of frameworks in TTT\u2013DTDA and TTT\u2013BTDA was further corroborated by Fourier transform infrared (FT-IR) spectroscopy. In the FT-IR spectra the presence of a strong vibration at 1582 cm\u20131 can be assigned to the stretching mode of the \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds and amino (\u223c3450 cm\u20131) stretching bands of respective starting materials completely disappeared after COF formation and Langmuir (440 m2 g\u20131) surface areas. In case of TTT\u2013BTDA, most probably, due to the partial offset stacking of adjacent layers seen in the less defined PXRD pattern in comparison to TTT\u2013DTDA, just moderate surface area values were observed \u2013COOCH3. The signal recorded after 160 min reaction time (g = 2.0048 and superhyperfine structure (shfs) constants for the coupling of the electron at C\u03b1 with the three CH3 protons and the two protons at C\u03b2, A3CH = 22.2 G, A\u03b21H = 14.7 G, A\u03b22H = 7.9 suggesting a light-driven process as well as involvement of a radical polymerization mechanism to poly-methyl methacrylate (PMMA), where COFs play a key role in the generation of holes that induce hydrogen abstraction from the amine co-initiator. The facile separation of these COF-photoinitiators from the MMA/PMMA mixture and their recyclability for multiple radical polymerization cycles together with their capability to initiate radical reactions under visible-light, make these materials very promising photoinitiators for a range of photochemical reactions.There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Just boil it in cumene! A general metal-free oxidation method is described. 2 and initiate radical chain reactions in catalyst-free conditions. In the absence of additional substrates, these processes can lead to acetophenones. In the presence of substrates, the cumene oxidation process can be intercepted in various chain reactions, affording very simple protocols for functional group oxidation.Due to the relative stability of the cumyl radical, cumenes and \u03b1-methyl-styrenes are ideally structured to directly harvest the oxidizing reactivity of O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleaving oxidation of styrenes with O3),2, such as in the Wacker process, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond cleaving oxidation of styrenes towards the corresponding phenones while using an iron(iii)-triflate catalyst bearing a tridentate amine ligand, with O2 as the terminal oxidant .4 = Ac, 2j), make the cumenes unreactive, likely by preventing the first oxidation step: the cumyl H-atom abstraction. For halides, methoxy, and phenyl functional groups, the tolerance is generally acceptable. A mechanism is proposed in 2 in a Hayashi-like mechanism.tert-butylphenol added to the reactor as a radical inhibitor suppresses acetophenone formation oxidizing strategy .2 system would also be competent for simple functional group oxidation. We therefore considered the oxidation of a series of organic substrates under those conditions. For example, benzhydrol 9 yields benzophenone . Diphenylmethane 10 also yields benzophenone , while xanthene (11) and fluorene (12) produce xanthone 16 and fluorenone 17 with 93% and 74% yield respectively. Finally 1,2-diphenylhydrazine (13) yields azobenzene 18 (93%). All were efficiently transformed while simply being heated up in cumene under 1 atm of O2 at 150 \u00b0C, without any further additive. These trivial oxidation processes are among the most studied reactions in the literature.The following reaction conditions were eventually selected: cumene, 14 mmol, is placed in an 85 mL glass reactor, which is then flushed with Oormation . This restrategy . One metydrazine yields a2 towards the corresponding phenones can proceed efficiently without a catalyst. These typically require significantly higher temperatures however than under catalytic conditions.2 mediated oxidation of cumene can be intercepted in the frame of cross dehydrogenative couplings, or the simple oxidation of diverse functional groups. Clearly, cumene and its congeners are well suited for the organic activation of O2 towards oxidative applications.In conclusion, the oxidative C\u2013C bond cleaving oxidation of cumenes or \u03b1-methyl-styrenes with OSupplementary informationClick here for additional data file."}
+{"text": "The synthesis and isolation of two-electron reduced naphthalenediimides is reported. A doubly zwitterionic structure is observed for the first time in a naphthalene moiety, which aids in its stabilization. \u2013) reduced, highly electron-rich naphthalenediimides (NDIs). A doubly zwitterionic structure is observed for the first time in a naphthalene moiety and validated by single crystal X-ray crystallography and spectroscopic methods. The synthesis avoids hazardous reducing agents and offers an easy, high-yielding route to bench-stable di-reduced NDIs. Notably, we realized high negative first oxidation potentials of up to \u20130.730 V vs. Fc/Fc+ in these systems, which establish these systems to be one of the strongest ambient stable electron donors. The study also provides the first insights into the NMR spectra of the di-reduced systems revealing a large decrease in diatropicity of the naphthalene ring compared to its 2e\u2013 oxidized form. The NICS, NICS-XY global ring current, gauge-including magnetically induced current (GIMIC) and AICD ring current density calculations revealed switching of the antiaromatic and aromatic states at the naphthalene and the imide rings, respectively, in the di-reduced system compared to the 2e\u2013 oxidized form. Notably, the substituents at the phosphonium groups significantly tune the antiaromatic\u2013aromatic states and donor ability, and bestow an array of colors to the di-reduced systems by virtue of intramolecular through-space communication with the NDI scaffold. Computational studies showed intramolecular noncovalent interactions to provide additional stability to these unprecedented doubly zwitterionic systems.The di-reduced state of the naphthalene moiety and its congeners have long captivated chemists as it is elusive to stabilize these intrinsically reactive electron-rich \u03c0-systems and for their emergent multifaceted properties. Herein we report the synthesis and isolation of two-electron (2e Although through-space charge delocalization has been elegantly formulated in NDI cyclophanes, ambient stabilization of 2e\u2013 reduced individual NDIs has not been possible.\u2013 uptake and release as well as the tunability of the aromatic naphthalene \u03c0-backbone and the nonaromatic imide rings. Thus, redox-assisted inter-conversion between the aromatic and nonaromatic states can be envisioned.Isolation of a two-electron reduced naphthalene dianion and its \u03c0-extended systems is a challenge being pursued over last several decades. In 1965, a naphthalene dianion was realized in the solution state1\u20135) with the first oxidation potential ranging from \u20130.724 to \u20130.263 V vs. Fc/Fc+ . We observed that second reduction potential of the dicationic NDI (2e\u2013 oxidized form) plays a key role during the synthesis of di-reduced compounds. EWGs at the axial- and the core-positions of the NDI led to a significant contrast between the first and second reduction potentials, which significantly favoured the one-step synthesis of 3\u20135. The reduction potentials and the corresponding LUMO levels of the parent dicationic compounds are listed in Herein we report the first synthetic protocol towards the isolation of ambient stable NDI-based di-reduced compounds at the axial positions , which is shifted upfield by 1.61 ppm compared to the same protons of 2+1 that appear at 8.94 ppm (J = 11 Hz). This signifies a significant contribution of the paratropic ring current in the naphthalene ring and decrease in diatropicity. This upfield 1H NMR chemical shift is observable even for the protons not directly attached to NDI scaffold. For example, the protons Hf and Hg of the ethyl groups linked to the phosphonium groups in 1 appear at 2.34 and 1.13 ppm, respectively, while in 2+1 they appear at 2.75 and 1.30 ppm, respectively. The axial group protons, He (5.30 ppm) and Hb\u2013d (7.28\u20137.15 ppm), of 1 also show measurable upfield chemical shifts compared to the same protons in 2+1 appearing at 5.41 and 7.48\u20137.27 ppm, respectively.In the presence of an external magnetic field, aromatic systems sustain a diatropic ring current while antiaromatic systems sustain a paratropic ring current.e of 12+ . In the 1H NMR spectra was also observed for 2\u20135. The phenylene/naphthalene protons in 2 solution.To have the first insight into the structural characteristics of the di-reduced compounds, we sought to crystallize 2+1 and 2+2 were grown from DCM: toluene (2\u2009:\u20091) solution at room temperature and the structural parameters compared with 1 and 2.23Further, single crystals of 1 crystallizes in the monoclinic space group \u201cC2\u201d with one molecule per asymmetric unit scale\" fill=\"currentColor\" stroke=\"none\">O bond length of 1 compared to 2+1 and the longest C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond was found to be 1.252 \u00c5, suggesting its partial double bond character. In addition, bond lengthening in the annular C5\u2013C5\u2032 and the transverse bonds of the naphthalene moiety along with shortening in the P1\u2013C2, C2\u2013C3, C1\u2013C6 and C4\u2013C7 bonds was observed indicating delocalization of the two additional electrons over the NDI scaffold (ESI Table S12+1 (vide infra). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups and shortening of the P\u00b7\u00b7\u00b7O distance suggest significant polarization of the positive and negative charges over the P atom of the phosphonium group and the O atom of the imide groups, respectively. A \u03c0-conjugated betaine-type di-zwitterionic structure is therefore pertinent from the crystallographic insight.ric unit . We obse2+1 crystallizes in the triclinic space group \u201cP1[combining macron]\u201d with a half molecule per asymmetric unit scale\" fill=\"currentColor\" stroke=\"none\">O adjacent to the phosphonium group shows a bond distance of 1.212 \u00c5, while the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond situated remote to the phosphonium group had a distance of 1.219 \u00c5. The intramolecular P\u00b7\u00b7\u00b7O non-bonded distance was found to be 2.811 \u00c5. The BF4\u2013 counter anions show strong anion\u2013\u03c0 interaction with a small shift towards the imide region of the NDI scaffold. The distance between the F atom of anion and the C atoms of the naphthalene moiety is in the range of 3.113\u20133.451 \u00c5 and the distance from the centroid of naphthalene (Ct) to the B atom of the anion was found to be 3.524 \u00c5.ric unit . The imi2 crystallizes in the triclinic space group \u201cP1[combining macron]\u201d with a half molecule per asymmetric unit scale\" fill=\"currentColor\" stroke=\"none\">O bond length of 1.224 \u00c5 in comparison to 2+2 (1.213 \u00c5) corroborates partial double bond character. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group remotely placed with respect to the phosphonium group also showed bond elongation (1.245 \u00c5) in comparison to 2+2 (1.208 \u00c5) scale\" fill=\"currentColor\" stroke=\"none\">O adjacent to the phosphonium group shows a bond length of 1.213 \u00c5, slightly longer than the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond (1.208 \u00c5) situated remote to the phosphonium group. The distance between P\u00b7\u00b7\u00b7O was found to be 2.738 \u00c5, which is 0.073 \u00c5 shorter than that in 2+1, corroborating a stronger P\u00b7\u00b7\u00b7O donor\u2013acceptor type interaction when the phosphonium groups are substituted with phenyl rings. Moreover, both the BF4\u2013 anions form anion\u2013\u03c0 interactions and are situated exactly on the top and bottom of the naphthalene ring with a distance of 2.968\u20134.010 \u00c5 between the naphthalene carbons and the F atom of BF4\u2013 anions and differential pulse voltammetry (DPV) experiments were performed for the di-reduced and dicationic forms in DCM reaching 3.3 \u00d7 104 L mol\u20131 cm\u20131 . In toluene\u2009:\u2009DCM (97\u2009:\u20093 v/v), the t1/2 was found to be 6.1 months, which is the highest stability amongst any reported di-reduced NDI molecules calculations. The negative NICS values indicate a diatropic ring current, while positive NICS values indicate a paratropic ring current.ectively . NICS values for the same was found to be 0.8 and 1.6 ppm respectively, which indicates the nonaromatic nature of the naphthalene moiety.However, the positive NICS (0) values of 4.0 ppm and 4.9 ppm for the naphthalene ring in the case of the di-reduced systems 2+1 and 2+2 comprising of the six-membered rings shows positive NICS (0) values of 4.7 and 5.2 ppm, respectively, indicating antiaromaticity. The NICS (1) values for the same were found to be 0.3 and 0.7 ppm, respectively, indicating nonaromatic nature. However in 1 and 2, the NICS (0) turns negative with values of \u20134.3 and \u20133.5 ppm, indicating its weakly aromatic nature, while NICS (1) turns negative with with values of \u20135.9 and \u20135.4, suggesting its aromatic nature. These findings indicate that in the di-reduced compounds, the naphthalene moiety nurtures antiaromatic/nonaromatic states and the imide rings provide the aromatic/nonaromatic state. Thus, a 2e\u2013 redox reaction can switch the antiaromatic\u2013aromatic sites in these electron-rich and electron-deficient systems.In contrast, the imide regions of XY scans for the di-reduced systems and compared with the corresponding dications.XY scan for 1 and 2+1 in different directions keeping NICS probes (dummy atoms) at 1.7 \u00c5 above the molecular plane under examination at 0.1 \u00c5 intervals and scanned along the X-axis value of the carbonyl group remote to the phosphonium group, respectively. This clearly suggests the bond lengthening of carbonyl groups adjacent to the phosphonium group due to the strong P\u00b7\u00b7\u00b7O non-bonding interactions as validated from crystallographic studies scale\" fill=\"currentColor\" stroke=\"none\">O bonds of the dication also shows antiaromatic nature basis set using the IEFPCM model in DCM. The axial groups in all the cases were replaced by the methyl group to save computational cost. The calculated HOMO and LUMO energies of 1 were found to be \u20134.145 and \u20131.436 eV, respectively, while for 2 they were \u20134.225 and \u20131.628 eV, respectively. For 2+1, the HOMO and LUMO levels were \u20138.372 and \u20134.903 eV, respectively, and for 2+2 they were \u20138.063 and \u20134.894 eV, respectively. The calculated HOMO energy levels of di-reduced and LUMO energy levels of dications are in excellent correlation with electrochemically obtained HOMO\u2013LUMO values distribution of m groups .Natural population analysis (NPA) = 2.24 kcal mol\u20131 for 2+2 and E(2) = 4.44 kcal mol\u20131 for 2 per P\u00b7\u00b7\u00b7O interaction was estimated using second-order perturbation theory. This stronger P\u00b7\u00b7\u00b7O interaction in 2 further supports greater distribution of the negative charge through the imide carbonyl groups due to the additional two electrons in the di-reduced compounds.Natural bond orbital (NBO) analysis1, 2 and its dicationic precursors.Atoms in molecule (AIM) analysis2\u03c1(rb) P\u00b7\u00b7\u00b7O, E(rb)P\u00b7\u00b7\u00b7O, G(rb)P\u00b7\u00b7\u00b7O, and V(rb)P\u00b7\u00b7\u00b7O for the P\u00b7\u00b7\u00b7O interactions are summarized in \u03c1(rb), values at the BCP of the P\u00b7\u00b7\u00b7O are in the range of H-bonding interactions (\u03c1H-bond \u2248 0.002\u20130.04 a.u.).\u03c1(rb) for 1 (0.021 a.u.) and for 2 (0.025 a.u.) are higher than that for 2+1 (0.018 a.u.) and 2+2 (0.018 a.u.) validating a stronger P\u00b7\u00b7\u00b7O interaction in the di-reduced compounds. The Laplacian density, \u22072\u03c1(rb), is also in the range of strong H-bond interactions.The 2D critical bond paths are shown in E(rb) for molecule 2+2 indicates its dominant electrostatic nature and the negative E(rb) values for 2 indicate its partial covalent nature [E(rb) value at a specific BCP indicates whether the interaction is electrostatic dominant E(rb) > 0 or covalent dominant E(rb) < 0]. The positive value of G(rb) and negative value of V(rb) support its stable, bound stationary states reduced, highly electron-rich, bench-stable NDIs. A doubly zwitterionic structure is observed in a naphthalene moiety and validated by single crystal X-ray crystallography. This new genre of compounds was achieved in high-yields via a solvent-free synthetic protocol. The di-reduced systems endow exceptional inherent stability with a half-life time of more than six months in toluene under ambient conditions. Notably, high negative first oxidation potentials up to \u20130.730 V vs. Fc/Fc+ and HOMO levels extending to \u20134.360 eV were realized.We demonstrated isolation of two-electron (2e\u2013 oxidized form, suggesting a large decrease in the diatropicity of the naphthalene ring. The NICS, NICS-XY, GIMIC and AICD calculations revealed redox switching of the antiaromatic and aromatic states at the naphthalene and the imide rings, respectively, in the di-reduced system compared to the corresponding rings of the 2e\u2013 oxidized form. The substituents at the axial- and core-positions tune the antiaromatic\u2013aromatic states and the electron donor ability. Further an array of diverse colors was achieved for the di-reduced systems. The through-space non-covalent interactions are key elements assisting this tunability. Isolation of this new class of ambient stable systems should have fascinating implications in controlling electron transfer reactions and development of new switchable materials.The study offers the first insights into the NMR spectra of the di-reduced systems revealing large upfield chemical shifts for the NDI-core atoms and the adjoining groups compared to their 2eThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Dual modulated luminescence of carbogenic nanodots derived from zeolites has been acquired by controlling the concentration and pH value of CND aqueous dispersions. N-methylpiperazine-templated zeolite precursor by calcination and NaOH treatment. The isolated CNDs exhibit tunable photoluminescence according to the concentration and pH value of aqueous dispersions of the CNDs. Fine-tuning of the fluorescence emission wavelength across the entire visible spectrum can be easily achieved by varying the concentration of the CND dispersions. Meanwhile, both the emission wavelength and intensity of the photoluminescence can be tuned by controlling the pH value of the CND dispersion. The pyrolysis of organic templates confined in nanoporous zeolites represents a new approach to controlling the optical properties of CNDs, which may open more opportunities in applications such as multimodal sensing and full-color displays.Hydrophilic N-doped carbogenic nanodots (denoted as CNDs) have been prepared from a Recently, the pyrolysis of organic templates confined within zeolites has been found to be an efficient approach for preparing well dispersed CNDs with uniform size, benefiting from the well-confined pore space of zeolites.Carbogenic nanodots (denoted as CNDs) are defined as small graphene-based oxygenous carbon nanoparticles with a size of less than 10 nm. As a new member of the nanocarbon family, luminescent CNDs have attracted increasing attention due to their intriguing advantages when compared with conventional semiconductor quantum dots, such as their low toxicity, biocompatibility, low cost and chemical inertness.etc., may affect the PL properties of CNDs, some alternative methods have been used to adjust the PL of CNDs. For example, Li et al. have reported the size-dependent photoluminescence of CNDs by controlling the current intensity of an electrochemical oxidation method.et al. have reported the PL modulation of graphene quantum dots through a surface chemistry route.et al. have observed that the fluorescence intensity of CNDs decreased when the pH value of the solution was shifted from 7.0 - regardless of whether it was increased or decreased.et al. observed that the emission intensities of CNDs were similar within the pH range of 4\u201312, but decreased abruptly at lower pH values (<4).et al. and Hu et al. have presented CNDs with full-color emissions by varying the reagents and reaction conditions.Tunable photoluminescence (PL) is one of the attractive properties of CNDs for their practical application, in particular, CNDs with full-color emissions are highly desirable.N-methylpiperazine (NMP) confined in zeolite MgAPO-44 with CHA zeotype topology. The isolated CNDs exhibit excellent aqueous dispersibility and stability. Interestingly, the PL emission of aqueous dispersions of the CNDs can be simply modulated by controlling the concentration of CNDs, which display full-color emissions. In addition, not only the intensity of the photoluminescence, but also the emission wavelength can be tuned by varying the pH value of the CND dispersions. This ability to control the optical properties of CNDs may offer more opportunities in applications such as multimodal sensing and full-color displays.In this work, we present the preparation of uniform N-doped CNDs by the pyrolysis of 2O3\u2013P2O5\u2013NMP\u2013H2O. Typically, pseudoboehmite and magnesium acetate tetrahydrate (Mg(CH3COO)2\u00b74H2O, 99.0%) were dispersed in a solution of orthophosphoric acid in water under vigorous stirring at room temperature. Then, NMP was added to this mixture. After stirring for one hour, a homogeneous gel with an overall molar composition of 1.0 Al2O3\u2009:\u20091.0 MgO\u2009:\u20092.2 P2O5\u2009:\u20095.0 NMP\u2009:\u2009350 H2O was formed, which was heated under autogenous pressure at 180 \u00b0C in a 15 mL Teflon-lined stainless steel autoclave for 3 days. The crystals were washed in distilled water and dried at 60 \u00b0C overnight.The reagents and solvents employed in the synthesis were commercially available and used as received without further purification. The magnesium aluminophosphate zeolite MgAPO-44 was prepared under hydrothermal conditions in a reaction system of MgO\u2013Al\u20131 in air, followed by a 4 h isothermal hold at this temperature. Carbonization of NMP was occurring during this time, resulting in a CNDs@MgAPO-44 composite material.The as-synthesized zeolite product was placed into a normal furnace and heated from room temperature to 400 \u00b0C at a temperature ramp rate of 2 \u00b0C min\u20131. The R-CNDs sample was diluted to 0.92, 0.68, 0.22 and 0.04 g L\u20131 samples . To study the influence of the pH value on the PL properties of the CNDs, NaOH and HCl aqueous solutions were used to adjust the pH value of the G-CND solution to 8\u201314 and 1\u20136, respectively.400 mg of CNDs@MgAPO-44 sample was dissolved in 2.5 mL of 2.5 M NaOH aqueous solution at room temperature, and ultrasonic treatment was used to accelerate the dissolution. Then 5 mL of deionized water was added and insoluble residues were centrifugally separated from the solution. The dark colored supernatant was collected and neutralised with HCl solution to a pH value of about 7, it was then further centrifugally separated and purified by dialyzing with a cellulose ester membrane bag (molecular-weight cutoff = 1000). The initial purified CNDs were denoted as R-CNDs with a concentration of around 1.36 g L13C solid-state MAS NMR were performed on an Infinity Plus400 spectrometer operating at B0 = 9.7 T. 27Al solid-state MAS NMR were recorded on a Bruker AVANCE III 400 WB spectrometer operating at B0 = 9.4 T. Total Organic Carbon (TOC) analysis was performed on an Elementar Vario TOC cube. The absolute fluorescence quantum yields were measured on an Edinburgh FLS920 fluorimeter. Photoluminescence spectra were recorded on a Fluoromax-4 spectrofluorometer (Horiba Jobin-Yvon). Nano-second fluorescence lifetime measurements were performed using a time-correlated single-photon counting (TCSPC) system under right-angle sample geometry. A NanoLED-340 was used to excite the samples. The white light used in this work was obtained by irradiation with a High Power Xenon Lightsource (HPX-2000).Powder X-ray diffraction (PXRD) data were collected on a Rigaku Ultima IV diffractometer. The CND ethanol solution was spotted onto a salt plate and the spectrum was measured on a Bruker FTIR IFS-66V/S. A baseline correction was applied after measurement. UV-vis adsorption spectra were obtained on a Shimadzu UV-2550 spectrophotometer. The TEM and HRTEM images were taken on a FEI Tecnai G2 S-Twin F20 transmission electron microscope. The X-ray photoelectron spectroscopy (XPS) measurements were performed using a Thermo Escalab 250 spectrometer with monochromatized Al K\u03b1 excitation. CHA zeotype structure.13C MAS NMR pattern of MgAPO-44 images reveal their lattice spacings to be 0.21 nm, which is consistent with the lattice spacing of the (100) plane of graphene.TEM images of the isolated CNDs are shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds (284.7 eV), C\u2013N/C\u2013O bonds (286.2 eV) and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds (287.9 eV). The N 1s spectra can be deconvoluted into two peaks of pyridinic type (399.0 eV) and pyrrolic type (400.1 eV) N atoms. The O 1s spectra are assigned to O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds (531.0 eV), O\u2013C bonds (532.8 eV) and adsorbed water (535.6 eV). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds spectra of the B-CNDs and R-CNDs are shown in C bonds 5.0 eV, O\u2013In previous reports, near zero or only a few percent (about 2%) N content has been found in CNDs obtained by the pyrolysis of templates confined in zeolites.ca. 18.7% (B-CNDs) without any further functionalization, which is higher than most of the bare and raw CNDs, which have typical values below 10%.Strikingly, the isolated CNDs not only exhibit excitation-dependent luminescence, but also display concentration-modulated luminescence. The as-made CND dispersions are stable for over six months, and no obvious PL changes are observed (Fig. S7, ESINotably, such concentration-modulated luminescence of CNDs across the entire visible spectrum is distinguished from previous reports, which tune emissions by controlling the reaction conditions or subsequent oxidation/reduction operations.The PL decay curves of the obtained CNDs were measured, and the decay fitting results are listed in Table S1.i.e., blue, green and green-yellow, can be observed at pH values of 2, 6 and 10 respectively, upon irradiation with white light (The influence of the pH value on the PL properties of the CNDs has also been investigated. As shown in te light . PreviouFTIR and UV-vis spectra of the CND dispersions at pH values of 2, 6, and 10 have been obtained (Fig. S11 and S12, ESIN-methylpiperazine occluded in the MgAPO-44 zeolite. Abundant N/O-containing hydrophilic groups are in situ generated on the surface of the as-made CNDs, endowing these CNDs with excellent aqueous dispersibility and stability, as well as a high PL quantum yield of up to 18.7% without any further functionalization. These CNDs exhibit interesting concentration-dependent PL properties, including full-color emissions when excited by white light. Such tunable PL of CNDs might mainly result from the energy transfer between multiple emitters in the nanoclusters that form in the highly concentrated CND dispersions. Meanwhile, pH-sensitive color and PL intensity modulation of the CND dispersions have also been observed. The detailed mechanism needs to be further investigated. This work provides a new approach for facilely controlling the optical properties of CNDs through the pyrolysis of organo-templated zeolites, which may open more opportunities in the application of CNDs in multimodal sensing and full-color displays.In summary, we have successfully developed fluorescent CNDs responsive to the concentration and pH value of their CND dispersions. The CNDs are prepared by the pyrolysis of Supplementary informationClick here for additional data file."}
+{"text": "Through mixed metal cooperativity, alkali metal magnesiates efficiently catalyse the cyclisation of alkynols. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond. In order to optimise the reaction conditions and to garner vital catalytic system requirements, a series of alkali metal magnesiates were enlisted for the catalytic intramolecular hydroalkoxylation of 4-pentynol. In a prelude to the main investigation, the homometallic magnesium dialkyl reagent MgR2 (where R = CH2SiMe3) was utilised. This reagent was unsuccessful in cyclising the alcohol into 2-methylenetetrahydrofuran 2a or 5-methyl-2,3-dihydrofuran 2b, even in the presence of multidentate Lewis donor molecules such as N,N,N\u2032,N\u2032\u2032,N\u2032\u2032-pentamethyldiethylenetriamine (PMDETA). Alkali metal magnesiates MIMgR3 performed the cyclisation unsatisfactorily both in the absence/presence of N,N,N\u2032,N\u2032-tetramethylethylenediamine (TMEDA) or PMDETA. When higher-order magnesiates were employed, in general a marked increase in yield was observed for MI = Na or K; however, the reactions were still sluggish with long reaction times (22\u201336 h). A major improvement in the catalytic activity of the magnesiates was observed when the crown ether molecule 15-crown-5 was combined with sodium magnesiate Na2MgR4(TMEDA)2 furnishing yields of 87% with 2a\u2009:\u20092b ratios of 95\u2009:\u20095 after 5 h. Similar high yields of 88% with 2a\u2009:\u20092b ratios of 90\u2009:\u200910 after 3 h were obtained combining 18-crown-6 with potassium magnesiate K2MgR4(PMDETA)2. Having optimised these systems, substrate scope was examined to probe the range and robustness of 18-crown-6/K2MgR4(PMDETA)2 as a catalyst. A wide series of alkynols, including terminal and internal alkynes which contain a variety of potentially reactive functional groups, were cyclised. In comparison to previously reported monometallic systems, bimetallic 18-crown-6/K2MgR4(PMDETA)2 displays enhanced reactivity towards internal alkynol-cyclisation. Kinetic studies revealed an inhibition effect of substrate on the catalysts via adduct formation and requiring dissociation prior to the rate limiting cyclisation step.Mixed s-block metal organometallic reagents have been successfully utilised in the catalytic intramolecular hydroalkoxylation of alkynols. This success has been attributed to the unique manner in which these reagents can overcome the challenges of the reaction: namely OH activation and coordination to and then addition across a C Being 100% atom efficient,2-vinylidene metal complex intermediate (I), which is then susceptible to nucleophilic addition to generate a Fischer oxacarbene (II) that ultimately yields the endocyclised product (III).A catalogue of catalysts has been developed for the cyclisation of alkynols, including various transition metal complexes as well as alkaline earth and f-block compounds. Transition metals previously used to promote this transformation are mostly precious metalsrmediate , I, whicacarbene , II that product , III.53\u2013Besides the numerous examples of transition metal catalysts, the use of f- and s-block catalysts for this reaction has been investigated. In terms of f-block chemistry, Marks has utilised lanthanide amide catalysts,via exocyclisation, although with alkaline earth metal amides two different product isomers were observed, an internal and external alkene. Since Hill's initial study, several papers focusing on alkali metal and alkaline earth catalysts have been published. Liu has shown that potassium tert-butoxide is an effective and selective catalyst for cyclisation of aromatic alkynylamines and alkynols,cis-6-hydroxy- and cis-6-acyloxyhex-2-en-4-ynals to 2-acylfurans and 2-furans is achievable using calcium catalysis.These particular studies highlight that transformations proceed selectively PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. Combining kinetic experiments with reactivity studies, here we provide informative mechanistic insights on how cooperative effects can be maximised as well as on the key role that each metal plays in these novel magnesiate-catalysed transformations.Expanding the scope of s-block cooperative catalysis, here we report the first catalytic applications of alkali metal magnesiates to promote cyclisation reactions, focusing on intramolecular hydroalkoxylation of alkynols. Benefitting from the enhanced metallating and nucleophilic abilities of these synergistic systems, we envisaged that they could play a dual role in overcoming the main challenges encountered in these transformations, facilitating not only OH activation, but also the required addition across C2SiMe3)2, containing thermally stable monosilyl groups, as a potential pre-catalyst. Using 4-pentynol (1) (as previously employed by Marks and Hill) for benchmarking with a catalytic quantity of the magnesium reagent, no reaction was observed even when the mixture was heated to 75 \u00b0C for 36 h magnesium reagent Mg2 could be due to the magnesium centre not being large enough to simultaneously bind to the oxide anion and be in close proximity to the \u03c0-density of the carbon\u2013carbon triple bond.This raises the question, \u201cwhy is magnesium unable to mediate this cyclisation whereas calcium can?\u201d Major contributory factors are likely due to the significant difference in ionic radii between the two metal cations and the low \u03c0-philicity of magnesium.2SiMe3) and Na(CH2SiMe3) were employed in the same reaction; however, the conversions were poor (<5%) (see ESI2SiMe3) (2SiMe3), Na(CH2SiMe3) and Mg(CH2SiMe3)2 can perhaps be attributed to the larger ionic radius of potassium versus the other metals allowing it to interact with the carbon\u2013carbon triple bond, activating it for cyclisation.We next focused on testing homometallic alkali metal organometallics, which, being significantly more polar than their Mg counterparts, have recently found applications in hydrophosphination catalysis.) see ESI. Using tI2SiMe3) , entry 3i.e., promote a dual-activation where a magnesium alkoxide forms, thus preparing one end of the substrate for cyclisation while the alkali metal could then interact with the \u03c0-system of the carbon\u2013carbon triple bond. As alluded to previously, this latter feature is essential as the magnesium alone cannot provide this interaction. LiMg(CH2SiMe3)3 . Moving to sodium (2SiMe3)]. When the potassium magnesiate KMg(CH2SiMe3)3 (2SiMe3) (11%). So, in summary, lower order magnesiate reagents are generally poor at catalysing the hydroalkoxylation/cyclisation reaction.Next, we investigated the catalytic ability of a lower-order magnesiate. It was envisaged that a bimetallic magnesiate could function cooperatively, 2SiMe3)3 , entry 5o sodium , entry 62SiMe3)3 , entry 8N,N,N\u2032,N\u2032-tetramethylethylenediamine) and PMDETA , were employed to completely fill the coordination sphere of the alkali metals. Again, starting with the lithium derivative, the higher-order magnesiate (2MgR4(TMEDA)2 was employed (2MgR4(PMDETA)2 is used . In addition, they continue to have a high isomer selectivity with up to 90% of the external alkene isomer being produced. The remarkable alkali metal effect observed between Li2MgR4(TMEDA) and K2MgR4(PMDETA)2 is even more striking when considering that both mixed-metal species are isostructural.3(TMEDA) and KMgR3(PMDETA) (2MgR4(PMDETA)2 is unaffected when the bidentate Lewis base TMEDA is used in place of its tridentate analogue PMDETA (2MgR4(TMEDA)2 displayed the same reaction time and selectivity as its PMDETA variant, demonstrating the reaction rate to be unaffected by the choice of Lewis base.In the hope of improving this situation, higher-order magnesiate reagents were considered. The Lewis basic proligands, TMEDA (3\u2013 or Mg(OR)42\u2013 fragment, of the now solvent-separated complex, was not able to perform the catalysis on its own. Surprisingly, in contrast, the results obtained in these reactions showed a dramatic improvement in reactivity!To establish whether or not both metals need to be present for the magnesiate to function, a catalytic amount of crown ether was added as a co-catalyst. As a crown ether of appropriate size is often able to sequester an alkali metal, the intention here was to ascertain, if the alkali metal was captured (non-cooperative), that the remaining anionic Mg(OR)Adding catalytic quantities of 15-crown-5 or 18-crown-6 to the sodium and potassium systems respectively dramatically increased the activity of the magnesiate catalysts, with the sodium higher-order magnesiate now nearing completion in 5 h . Therefore, these results suggest that the alkali metal is intimately involved and plays a key role in the cyclisation reaction. To ascertain whether the 18-crown-6 is catalytically active, when it is combined with only Mg(CH2SiMe3)2 the reaction fails (entry 2).Due to the significant difference in completion rates of these two reactions (5 h 2a is produced by employing La[N(SiMe3)2]3.3)2}2 where Ae = Ca, Sr, Ba], where reaction times ranged from 2.5\u20136 h, exhibiting a 2a isomer selectivity of 90\u201397% , where the carbon\u2013carbon triple bond has moved from a terminal to an internal location (Z-enynols (7 and 9). In 7) employing the optimised conditions we see the production of an aromatic furan product (8). This product differs from the product previously reported using heavier alkaline earthHaving established the optimal conditions for cyclisation of 4-pentynol, the scope of the reaction was evaluated. Terminal and internal alkynes were tested to assess the range and robustness of the catalytic system and 3. Ilocation , entry 1location , entry 23 or CN functional groups were incorporated into the substrate. Looking at 5-phenylpent-4-yn-1-ol (11) and an internal alkene (12c) (note these three products are still exocyclic). In this work, it was also noted that the product ratio appeared to have a degree of temperature dependence and required significantly harsher reaction conditions .In order to further probe the functional group tolerance of the catalytic magnesiate system, a range of internal alkynes were synthesised with different pendant functional groups, including halogens, and electron-donating and electron-withdrawing groups. It transpired that no side reactions took place when MeO, F, Cl, CF-ol (11) , entry 1t-butyl group , the same isomer ratios were obtained for all the reactions which tended towards completion show nicely the benefit of using a bimetallic system for these cyclisation reactions. With the heavier alkaline earth metal amides and lanthanide amides, substrate 11 is more challenging to cyclise, taking 16 h at 90 \u00b0C with Ca(HMDS)2 and about 15 h at 120 \u00b0C with La(HMDS)2. Marks3 is sterically driven by the phenyl substituent that prevents interaction between the metal and the internal alkyne. Using a bimetallic system, it appears that this steric clash is somewhat circumvented giving rise to a faster reaction time than the other two systems mentioned.This set of substrates based on 5-phenylpent-4-yn-1-ol (1), as this was used for the initial parameterisation studies. A plot of concentration of 1 against time displays a linear fit until half conversion when a rate acceleration is observed ), while at high concentrations of 1 (k\u20131[1] \u226b k2) eqn (3) rules this process. Alternatively, a pre-equilibrium approximation in which dissociation of 1 from magnesium does not influence the reaction rate leads exclusively to eqn (3), and hence to a good inverse first order relationship in 1 at any concentration of this ligand. The plot of the observed initial rates vs. 1/[1] during the course of the reaction only occurs upon its decoordination.Overall the deduced mechanism starts with formation of the active catalyst from the magnesiate pre-catalyst. This involves the deprotonation of four alcohol substrate molecules to form a magnesiate alkoxide, liberating tetramethylsilane. This \u2018active catalyst\u2019 is then involved in a coordination/decoordination process with an additional substrate molecule as suggested by the kinetic studies. This additional molecule of In cycle A the carbon\u2013carbon triple bond of the alkyne is directly inserted into the metal\u2013oxygen bond, leading to the formation of only one product upon protonolysis. Cycle B on the other hand involves an equilibrium isomerisation from alkyne to allene which upon insertion into the metal\u2013oxygen bond, and subsequent protonolysis, can yield two product isomers. Protonolysis releases the cyclised products and reforms the active catalyst completing the cycle. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds of the substrate. Thus, coordination of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond to the larger more \u03c0-philic potassium centre enables further activation of this unsaturated group and brings it into close proximity to the di-anionic (magnesiate) {Mg(OR)4}2\u2013 component, which is significantly more nucleophilic than a charge-neutral magnesium compound, facilitating intermolecular ring-closure to furnish the relevant oxygen-heterocycle.Disclosing a unique cooperative behaviour under catalytic conditions, each of the metals plays a key role in this process, by simultaneously activating the O\u2013H and C2SiMe3)2, K(CH2SiMe3), LiMg(CH2SiMe3)3, NaMg(CH2SiMe3)3, KMg(CH2SiMe3)3, Li2Mg(CH2SiMe3)4(TMEDA)2, Na2Mg(CH2SiMe3)4(TMEDA)2, K2Mg(CH2SiMe3)4(TMEDA)2 and K2Mg(CH2SiMe3)4(PMDETA)2] were prepared following literature procedures2SiMe3), 1 and 5 were obtained from Sigma-Aldrich; 1 and 3 from Alfa-Aesar; and 7 from Fluorochem. Substrates 11, 13, 15, 17, 19 and 21 were synthesised based on literature procedures13\u201322 can be found in the ESI1H, 100.6 MHz for 13C or 128.4 MHz for 19F.All reactions were carried out under a protective atmosphere of argon using standard Schlenk techniques. Non-deuterated solvents were dried by heating to reflux over sodium ketyl radicals under nitrogen and deuterated solvents were degassed and stored over molecular sieves. Pre-catalysts and with the oil bath temperature being changed where necessary based on observed reaction times. 0.5 mmol alkynol substrate was used with the monometallic species and lower-order magnesiates, and 0.6 mmol with higher-order magnesiate pre-catalysts. 0.025 mmol pre-catalyst was employed in all cases, quantities shown in 2Mg(OAlk)4(18-c-6)2 resting-state\u2019.In the catalytic cyclisation of 4-pentynol (1) with K2Mg(CH2SiMe3)4(PMDETA)2 + 18-c-6, 4-pentynol was placed in a Young's tap NMR tube with C6D6 (0.6 mL), 1,2,3,4-tetraphenylnaphthalene and 18-crown-6 . To this K2Mg(CH2SiMe3)4(PMDETA)2 was added. The reaction was maintained at 70 \u00b0C in the NMR spectrometer and was monitored by 1H NMR spectroscopy. Yields were calculated using NMR spectroscopic integrals characteristic of 2a relative to the internal standard, 1,2,3,4-tetraphenylnaphthalene. This procedure was repeated with 0.90, and 1.20 mmol alkynol (1) to provide the data presented in Fig. S1In the kinetic studies to determine the rate dependence of alkynol in the cyclisation of 4-pentynol 4(PMDETA)2 were employed, necessitating 0.05, 0.06 and 0.07 mmol 18-crown-6 co-catalyst. The data from these experiments with varying catalyst concentration are presented in Fig. S2The same procedure was applied to the investigation of the dependence of the initial rates of the reaction on the catalyst. The same concentration of 2K2Mg(CH2SiMe3)4 paired with 18-crown-6 has been shown to function well with both terminal and internal alkyne substrates having a range of functional groups. Kinetic studies have revealed an inhibition effect of substrate on the catalyst under standard conditions by the formation of a coordination adduct which requires dissociation prior to the cyclisation step. Initial reactivity studies suggest that coordination of the 18-crown-6 to K finely tunes the reactivity of the bimetallic system, probably minimising the coordination of additional substrate molecules to the catalyst.In summary, alkali metal magnesiates have been shown to successfully promote the catalytic intramolecular hydroalkoxylation of alkynols through cooperative bimetallic catalysis. The roles of both magnesium and potassium components are crucial for the success of the process, affording a unique type of substrate activation that is not possible in conventional single-metal systems. Through cooperativity, the utilisation of an alkali metal magnesiate has overcome the inherent problems associated with homometallic magnesium systems. The optimised catalyst system, (PMDETA)There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The important role of hydrogen bonding in the interactions of cationic-amphiphilic polymers with bacterial membranes has been reported. N-alkyl maleimide based amphiphilic polymers. Our studies reveal that amide polymer (AC3P) is a potent antibacterial agent with high membrane-disrupting properties compared to its ester counterpart (EC3P). To understand these differences we performed bio-physical experiments and molecular dynamics (MD) simulations which showed strong interactions of AC3P including hydrogen bonding with lipid head groups of bacterial model lipid bilayers, that are absent in EC3P, make them selective for bacterial membranes. Mechanistic investigations of these polymers in bacteria revealed specific membrane disruptive activity leading to the delocalization of cell division related proteins. This unprecedented and unique concept provides an understanding of bacterial membrane interactions highlighting the role of hydrogen bonding. Thus, these findings will have significant implications in efficient design of potent membrane-active agents.Biomimetic antibacterial polymers, the functional mimics of antimicrobial peptides (AMPs), targeting the bacterial cell membrane have been developed to combat the problem of antibiotic resistance. Amphiphilicity, a balance of cationic charge and hydrophobicity, in these polymers has been shown to be pivotal for their selective interactions with anionic lipid membranes of bacteria instead of zwitterionic mammalian (human erythrocyte) membranes. However, it is unclear if and to what extent hydrogen bonding in amphiphilic antibacterial polymers contributes to this membrane binding specificity. To address this, we employ isosteric substitution of ester with amide moieties that differ in their potency for hydrogen bonding in the side chains of This amphiphilicity which is a fine balance of hydrophobicity and cationic charge has been shown to play a key role in the selective interaction of these polymers with the bacterial membranes instead of mammalian based amphiphilic polymers prepared from their maleic anhydride precursor polymer. Substitution of an ester with an amide is isosteric and also varies in the potency of hydrogen bonding. We found that the amide polymers (AC3P) displayed high antibacterial activity compared to their ester (EC3P) counterparts. To probe these differences, we performed biophysical experiments and molecular dynamic (MD) simulations on bacterial model lipid bilayers. Collectively, our studies provided the evidence that AC3P, but not EC3P, form strong interactions including hydrogen bonding with the phosphate head groups of bacterial model lipid bilayers based amphiphilic polymers. An amide bond is isosteric to an ester because the \u2013O\u2013 in the ester is of near-equal size as the \u2013NH\u2013 in the amide moiety.1H NMR analysis as described previouslyalt-N--maleimide) (PIBMI) based quaternized amide (A) and ester (E) appended alkyl side chains respectively. A control polymer, HexP was weakly antibacterial with MIC = 125\u2013250 \u03bcg mL\u20131 against both E. coli and S. aureus has potent antibacterial efficacy with MIC of 31 \u03bcg mL. aureus .\u20131 and 3 \u03bcg mL\u20131 for AC3P whereas EC3P showed 16 \u03bcg mL\u20131 and >200 \u03bcg mL\u20131 against S. aureus and E. coli, respectively (Table S150 > 1000 \u03bcg mL\u20131 (50 = 30 \u03bcg mL\u20131) leading to low selectivity (HC50/MIC) against E. coli and S. aureus at 25 \u03bcg mL\u20131. AC3P has higher depolarization than the corresponding ester, EC3P (E. coli and S. aureus. Kinetics of membrane permeabilization was studied by measuring the uptake of the fluorescent probe propidium iodide (PI) against E. coli and S. aureus at 25 \u03bcg mL\u20131. Amide containing polymer has higher ability to permeabilize the bacterial cell membrane than ester polymer showed higher release of ATP levels compared to its ester counterpart, EC3P (50 \u03bcg mL\u20131) in both E. coli and S. aureus , the dissipation of membrane potential resulted in the complete delocalization of MinD, MreB and FtsZ. CCCP had been used as a positive control to see the effect of dissipating the membrane potential on delocalization of MinD /(I440 + I490)).To emphasize the fact that the interaction of the polymers is indeed with the cell membrane, we used model lipid bilayers. Liposomes were made using DPPG\u2009:\u2009DPPE (88\u2009:\u200912) and DPPC mimicking the bacterial and human erythrocyte membranes respectively with Laurdan , a hydrophobic dye encapsulated in them .34 Due ti.e. by gradually reducing the concentration of the free polymer in the solution (lipid\u2009:\u2009polymer = 30\u2009:\u20091). The interaction of the polymers with a DPPG\u2009:\u2009DPPE (88\u2009:\u200912) model lipid bilayer was found to be an entropy-driven endothermic process. AC3P had a complete and spontaneous entropy-driven interaction with the bacterial model lipid bilayer (within 20 injections) having \u0394G = \u201311.03 kcal mol\u20131 but with a lower positive \u0394S = 43.9 cal mol\u20131 K\u20131 suggest the \u201chydrophobic effect\u201d explained by the loss of water as the amphipathic molecule enters the lipid bilayer.To delineate the molecular understanding of interactions between the model lipid bilayers and polymers, we used isothermal titration calorimetry (ITC) for obtaining the thermodynamics of interactions. DPPG\u2009:\u2009DPPE (88\u2009:\u200912) or DPPC model lipid bilayers were injected into the polymer solution, l mol\u20131) . The conn Fig. S3. On the n Fig. S3. These rn Fig. S3. PositivN-alkylmaleimide and isobutylene moieties) simulations. The interactions were modelled using a mixture of (POPE\u2009:\u2009POPG = 7\u2009:\u20093).oieties) which weoieties) . Conformoieties) . Even Heoieties) . These rSuch differences in conformations indicate that these isosteric amide and ester polymers differ in the favourability of their interactions with bilayer lipids. To investigate the same, their interaction energies with the lipid bilayers were computed. The interaction energies have been computed in per sequestered side chain basis to keep them in same footing, since various polymers have different number of sequestered side arms after 150 ns of simulations. It can be seen from g(r)). Radial distribution functions have been computed between the amide and ester groups' hydrogen bond formers and the same from lipid head group atoms and are interpret in the following as their relative affinities in forming hydrogen bonds. The amide group scale\" fill=\"currentColor\" stroke=\"none\">O moieties) of the amide polymers interacted through strong hydrogen bonds with the oxygen atoms of the phosphate head groups of the POPG lipid molecules as seen in The differences in the ability of isosteric polymer species to form hydrogen bonds with the lipid head group atoms were probed through direct computations of number of hydrogen bonds. The positional order in the spatial distribution of hydrogen bond forming lipid head group atoms in the neighbourhood of amide and ester moieties has also been calculated. Conventionally, in atomistic MD simulations, hydrogen bonds are calculated using geometric criteria and the same was used in the present cases (donor\u2013acceptor distance \u2264 4.0 angstrom (\u00c5) and donor\u2013H\u2013acceptor angle \u2264 60\u00b0). The amide polymers have displayed a greater propensity to form hydrogen bonds compared to their ester counterparts, both in the overall number of hydrogen bonds formed and the number of sequestered side arms observed to be involved in the formation of said bonds Table S2. The proThe discernible differences in lipid\u2013amide polymer and lipid\u2013ester polymer interactions described above are further reflected in the relative ability of isosteric polymers in inducing structural re-organization of the lipid bilayer. The number density distribution of polymers and POPG molecules in the upper leaflet is shown in 20\u20131) and the amide (\u2013CONH\u2013) and the ester (\u2013COO\u2013) regions in the polymers (1600\u20131800 cm\u20131).To gain further insight into the hydrogen bonding interactions of polymers with lipid molecules, Raman spectroscopic studies were performed. The organic solution of the lipid + polymer was drop-casted onto a substrate, dried and studied using a Raman spectrophotometer. The full Raman spectra are provided in ESI Fig. S9. Since t\u20131 vibrational mode is due to \u2013P\u2013O\u2013 (DPPG head group), 1100 cm\u20131 is due to PO2\u2013 and 1129 cm\u20131 is due to \u2013P\u2013O\u2013 (DPPG tail group) (blue curve) for DPPG.\u20131 vibrational mode splits into doublet upon interacting with AC3P and EC3P scale\" fill=\"currentColor\" stroke=\"none\">P\u2013O\u2013 has the ability to resonate, hence the Fermi resonance (expected in AB2) doublet does not exist in PO2\u2013 of DPPG and the higher frequency mode is due to the P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO group (1100 cm\u20131). Interestingly, the relative intensities of the two peaks in doublet is higher in AC3P + DPPG than in EC3P + DPPG suggesting the strong interactions of amide polymer with the lipid compared to the ester polymer of the spectra as shown in \u20131) and the side chain ester C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO vibrational mode (1740 cm\u20131). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO of DPPG scale\" fill=\"currentColor\" stroke=\"none\">O (imide) at around 1770 cm\u20131. It is interesting to see that amide I mode (1680 cm\u20131) disappears in DPPG + AC3P (green curve \u20131) peak has shifted showing some weak interaction between DPPG and HexP as observed earlier.The polymer region (1600\u20131800 cmTm) of DPPG is 41 \u00b0C) (\u20131) band above 35 \u00b0C suggested the breaking of hydrogen bond. The strong 1740 cm\u20131 also shows the emergence of long chain ester C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO vibration of the lipid. Similar experiments in the DPPG + EC3P spectrum bring the emergence of a strong 1740 cm\u20131 similar to DPPG + AC3P indicated the breaking of ester polymer C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO hydrogen bond with DPPG . The eme Fig. S10. Heating Fig. S10.The above results clearly suggests that the difference between the interaction of AC3P and EC3P with DPPG is that the amide provides strong hydrogen bonding interactions with DPPG compared to EC3P probably through the two hydroxyl groups of the DPPG head group. These results also correlated with MD simulations which showed the hydrogen bonding interactions of amide polymers with the hydroxyl and phosphate oxygen atoms of POPG in bacterial model lipid bilayers. Taken together, these data suggested that despite similar electrostatic interactions, the lack of strong hydrogen bonding interactions can render weaker binding of ester polymers with lipid bilayers compared to amide polymers.In conclusion, isosteric substitution of ester with amide moiety in cationic-amphiphilic polymers influences the bacterial membrane interactions. With the unique concept of amide and ester moiety bearing polymers, for the first time we provided evidence for the role of hydrogen bonding in bacterial membrane interactions. However, the differences in the binding affinity of the amide and ester polymers with the bacterial membranes might not be solely due to the hydrogen bonding. We believe that this understanding will aid in bacterial membrane specific design of membrane-active molecules in future.alt-maleic anhydride) , 3-aminopropyldimethylamine and 1-propyl amine were purchased from Sigma-Aldrich and used as received. 1-Propanol was obtained from Spectrochem (India) and used as received. Culture media and the antibiotics were from HIMEDIA (India) and Sigma-Aldrich respectively. NMR spectra were recorded using Bruker AMX-400 (400 MHz for 1H) spectrometer. The chemical shifts (\u03b4) are reported in parts per million downfield from the peak for the internal standard TMS for 1H NMR. Infrared (IR) spectra of the solid compounds were recorded on Bruker IFS66 V/s spectrometer using KBr pellets. IR spectra of the compounds soluble in low-boiling solvents were recorded with the same instrument using NaCl crystal. Mass spectra were recorded on a Micromass Q-ToF micromass spectrometer. Optical density and absorbance were measured by Tecan InfinitePro series M200 Microplate Reader.All the solvents were of reagent grade and dried prior to use wherever required. Bromoacetyl-bromide, poly(isobutylene-S. aureus (MTCC 737) and E. coli (MTCC 443 or ATCC 25922) were purchased from MTCC . The antibacterial activity of the polymers was done against both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria. E. coli was cultured in Luria Bertani broth . For solid media, 5% agar was used along with above mentioned composition. The bacterial samples were freeze dried and stored at \u201380 \u00b0C. 5 \u03bcL of these stocks were added to 3 mL of the nutrient broth and the culture was grown for 6 h at 37 \u00b0C prior to the experiments.Bacterial strains Synthesis and characterization are provided in ESI.Antibacterial activity, hemolytic activity, cytoplasmic membrane depolarization and permeabilization were performed as described earlier.8\u20139 CFU mL\u20131) were harvested and washed twice with 10 mM TRIS buffer (pH = 7.5) and were resuspended in the same buffer. Then, 150 \u03bcL of bacterial suspension and 50 \u03bcL of test drugs were added to the micro centrifuge tube and incubated at 37 \u00b0C for 15 min. After 15 min, the bacterial suspension was centrifuged and 50 \u03bcL of the supernatant was transferred into a Corning 96 well black plate with clear bottom to find out the released ATP levels using ATP Bioluminescence Assay Kit (Sigma Aldrich) as per the manufacturer's instructions. A standard curve for ATP levels was generated using the ATP standards provided in the kit in the range of 1 \u00d7 10\u20136 to 1 \u00d7 10\u201311 moles of ATP levels. Relative ATP levels both in the standard curve and the test sample measurement were measured by subtracting the background ATP levels from the test sample ATP levels as per the manufacturer's instructions. All measurements were performed in duplicates using Tecan InfinitePro series M200 Microplate Reader.Mid-log phase bacteria (\u223c10B. subtilis strains were cultured in LB medium. Overnight cultures from a single colony were diluted and grown at 30 \u00b0C. Xylose (0.1\u20130.5%) was added to induce the GFP fusion proteins. At OD600 \u223c 0.2, 200 \u03bcL of cells were incubated with 25 \u03bcg mL\u20131 of polymers or positive control for 10 minutes. The last 3 minutes, 1 \u03bcg mL\u20131 Nile red (Sigma) was added for membrane staining. Microscope slides were covered with 1% agarose in deionized water. 0.4 \u03bcL of cells were spotted onto the agarose layer and excess liquid was allowed to evaporate before a 0.31 mm cover slip (VWR) was placed on top. Cells were observed with a Nikon Eclipse Ti inverted microscope with Nikon plan apo 100\u00d7 1.45 oil objective, and Hamamatsu ORCA Flash UBB 3.0 camera. Images were processed using Nikon and ImageJ software.Lipids (0.5 mM of DPPC or 0.5 mM DPPG\u2009:\u2009DPPE (88\u2009:\u200912)) and Laurdan dye (5 \u03bcM) were taken in round-bottom glass vials in chloroform. Thin films were made under dry argon gas, and films were dried under vacuum for complete drying. Lipid films were hydrated with 1\u00d7 PBS (pH = 7.4) for overnight. Hydrated films were then processed for 10 freeze thaw cycles from 70 to 4 \u00b0C with intermittent vortexing. Multilamellar vesicles were then sonicated at 70 \u00b0C for 15 min to get unilamellar vesicles.I440 \u2013 I490)/(I440 + I490)wherein I440 and I490 represent the fluorescent emission intensity at 440 nm and 490 nm respectively.2 mL of Laurdan embedded liposome dispersion (lipid\u2009:\u2009dye = 100\u2009:\u20091) containing the polymer solution (lipid\u2009:\u2009polymer = 7.4\u2009:\u20091) in PBS (pH = 7.4) was taken in a fluorescence cuvette. The fluorescence emission intensity was measured at 440 nm and 490 nm by using the excitation wavelength at 350 nm. The measurements were performed at 37 \u00b0C using Water Peltier system attached PerkinElmer LS-55 Luminescence Spectrometer. Laurdan, a hydrophobic dye detects changes in the membrane-phase properties through its sensitivity to the polarity of environment in the lipid bilayer. Polarity changes are shown by shifts in the Laurdan emission spectrum, which are quantified by calculating the generalized polarization (GP). Then, membrane hydration was determined using perturbations in Laurdan dye fluorescence due to the result of hydration of the lipid bilayer and quantified by calculating general polarization (GP). GP was calculated by using the following equation.GP = with 10 min intervals to ensure that the titration peak returned to the baseline before the next injection was done. Each injection lasted for 10 s and the stirring speed was kept at 307 rpm for homogenous mixing. A background titration was performed under same conditions with the buffer placed in the calorimetric cell instead of the polymer solution. This result was subtracted from each polymeric sample titration to account for the heat of dilution. The change in enthalpy (\u0394H) and the association constant (Ka) were obtained by fitting the data to one set of sites model using Origin 7 software from Micro Cal Inc. The Gibbs free energy change (\u0394G) and change in entropy (\u0394S) were calculated using the following equation\u0394G = \u2013RT\u2009ln(55.5Ka) = \u0394H \u2013 T\u0394Swherein, R is the universal gas constant , factor 55.5 is to account for the molar concentration of water and T is the absolute temperature in K.All experiments were performed at 37 \u00b0C using isothermal titration calorimeter . Reference cell was filled with double distilled water. All the experiments were performed in 10 mM HEPES and 0.14 M NaCl (pH = 7.4) buffer. The liposomal suspensions (DPPC or DPPG\u2009:\u2009DPPE (88\u2009:\u200912)) were made in the above buffer at 1 mM and polymers were also dissolved in the same buffer and used at a concentration of 50 \u03bcg mL+, Cl\u2013). Equilibrium structures of the 12-monomer length polymers in aqueous environment were obtained by simulating single polymers in 150 mM NaCl solutions for 50 ns. Initial system sizes for such simulations were \u223c68 \u00d7 68 \u00d7 68 \u00c53 containing \u223c9500 water molecules. Polymer properties in aqueous environment were computed over the last 30 ns (20\u201350 ns) of simulation data. The polymer configurations at the end of 50 ns were extracted, replicated and used to construct the polymer-bilayer systems. To construct each of the polymer-bilayer systems, four polymers were placed dispersed in the bilayer plane \u223c(12\u201318) \u00c5 away along the bilayer normal from one of the bilayer leaflets (referred to as \u201cupper leaflet\u201d). Additional water molecules were added so as to prevent the polymers from interacting strongly with the other bilayer leaflet (referred to as \u201clower leaflet\u201d), at least at the initial stages of simulations. Further, Na+ and Cl\u2013 ions were added to neutralize the excess charges in the systems and set salt concentration at 150 mM. The number of atoms for the polymer-bilayer systems simulated was \u223c86\u2009000. These systems were each simulated for 150 ns and stationary properties were computed over the last 20 ns (130\u2013150 ns) of simulation, unless stated otherwise. All simulations were performed under isothermal\u2013isobaric (NPT) conditions at a temperature of 310.15 K. Pressure was maintained at 1 atm using Langevin Piston.Classical atomistic molecular dynamics (MD) simulations were performed using simulation package NAMD (versions 2.8 and 2.9)\u20131) of sample was drop coated onto Sapphire substrate, dried under vacuum and studied using a Raman spectrophotometer.Measurements were performed using WiTec Raman spectrometer (UHTS600 SMFC) equipped with CCD (CCD-17531). The excitation source was 532 nm with a power of \u223c20 mW at the sample. A 60\u00d7 objective (Nikon make) with a numerical aperture (NA) 0.8 was used for normal Raman and 50\u00d7 ultra long working distance objective with 0.45 NA was used for temperature dependent studies for focusing the laser and collecting scattered light in 180\u00b0 back scattering geometry. The typical accumulation times were 600 seconds. Temperature dependent measurements were performed using Linkam cryostage (Linkam Scientific Instrument). 20 \u03bcL of methanolic solution (400 \u03bcg mLSupplementary informationClick here for additional data file."}
+{"text": "The structures of metabolites produced in microgram quantities by enzymatic reductions with baker's yeast were analyzed using the crystalline sponge method. The crystalline sponge method coupled with HPLC purification would be a useful method for metabolic analysis and drug discovery. The structures of metabolites produced in microgram quantities by enzymatic reductions with baker's yeast were analyzed using the crystalline sponge method. The X-ray data provided reliable structures for trace metabolites including their relative and absolute stereochemistries that are not fully addressed by conventional NMR and LC-MS analyses. Technically, combining two or more chromatographic purification techniques is essential because, unlike abundant synthetic compounds, extracted metabolites contain many low level UV-silent impurities. The crystalline sponge method coupled with HPLC purification (LC-SCD) would thus be a useful method for metabolic analysis and drug discovery. NMR and MS) and separation techniques (e.g. GC and LC) have been frequently used and established to elucidate the structures of scarce metabolites from a mixture. However, full characterization of their structures, including their absolute stereochemistry, is still a laborious task because of limited sample supply.The structural information of metabolites is key to understanding enigmatic cellular processes and for drug design.The crystalline sponge method2)3(tpt)2\u00b7(c-C6H12)x]n -1,3,5-triazine),2) by reductases found in baker's yeast. When compound 2 (100 mg) was treated with fermenting baker's yeast (dry yeast (11.2 g) and sucrose (23.5 g) in 100 ml of water) at 30 \u00b0C for 1 week, a small amount of a metabolic product (\u223c1.3% yield based on UV spectroscopy) was detected in the ether extract obtained from the mixture. LDI-TOF MS spectrometry indicated the loss of one chlorine atom from 2, suggesting the formation of 1,1-bis(4-chlorophenyl)-2,2-dichloroethane . The formation of 3 in a low yield is consistent with the previous report.4, cannot be excluded as the product based solely on MS information.As a model case of metabolic analysis using a crystalline sponge [(ZnItpt)2\u00b7c-CH12x]n using PTLC, the analytical sample was further purified using HPLC with a narrow collection time window \u00b7(C7H4Cl2)\u00b72.5(C3H6), M = 2230.02, colorless block, 0.23 \u00d7 0.11 \u00d7 0.09 mm3, monoclinic, space group C2/c, a = 35.7365(13) \u00c5, b = 15.0610(5) \u00c5, c = 30.9345(11) \u00c5, \u03b2 = 104.141(7)\u00b0, V = 16\u2009145.2(11) \u00c53, Z = 8, Dc = 1.835 g cm\u20133, T = 93(2) K, 2.989\u00b0 < \u03b8 < 27.468\u00b0, 17\u2009652 unique reflections out of 88\u2009524 with I > 2\u03c3(I), GoF = 1.063, final R factors R1 = 0.0780, and wR2 = 0.2736 for all data, CCDC deposit number 1451761.\u2021Crystallographic data for One is located near a tpt ligand where guest 3 was observed with 100% occupancy . A better resolution was obtained for A, and the electron density map F0 clearly shows the structure of 3 were obtained presumably due to very minor disorder in 3, which cannot be modeled yet contributes to the residual electron density significantly because of the heavy atom (Cl).The crystallographic analysis confirmed the structure of the metabolite to be 3 . The cryure of 3 . Slightl13C or 2D NMR) become difficult even for determination of the relative stereochemistry. The absolute stereochemistry can hardly be addressed by any spectroscopic methods unless empirical rules or data for authentic compounds are available. Thus, we applied the LC-SCD analysis for the full structural characterization (including absolute stereochemistry) of a metabolite from tetralone 5. This compound exists as a racemate due to rapid enolization at C1 and can give four possible stereoisomers (including enantiomers) upon reduction of the carbonyl group at C2.When a prochiral functional group is enzymatically reduced to a chiral one, the stereochemical issues are of major concern for the structural characterization. Moreover, with the product(s) isolated only in microgram quantities, NMR analyses with baker's yeast (11.2 g) for 18 h gave analytically pure chiral alcohol 6 in 10 \u03bcg quantity after isolation using HPLC. The relative stereochemistry of 6 was confirmed to be cis by comparison with both an authentic cis\u2013trans mixture obtained by the NaBH4 reduction of 5 and literature reported spectroscopic data.cis isomer 6. An inclusion crystal 1\u00b76 was prepared by soaking a crystal of 1 in a cyclohexane/1,2-dichloroethane (v/v = 9\u2009:\u20091) solution of 6. The crystal structure was solved with a non-centrosymmetric space group C2.1\u00b76: C72H48I12N24Zn6\u00b73.79(C13H16O4)\u00b71.93(C6H12), M = 4220.24, colorless rod, 0.18 \u00d7 0.11 \u00d7 0.06 mm3, monoclinic, space group C2, a = 36.3783(8) \u00c5, b = 14.6755(2) \u00c5, c = 31.2278(6) \u00c5, \u03b2 = 103.184(2)\u00b0, V = 16\u2009232.2(5) \u00c53, Z = 4, Dc = 1.727 g cm\u20133, T = 100(2) K, 4.1720\u00b0 < \u03b8 < 74.0140\u00b0, 31\u2009961 unique reflections out of 69\u2009980 with I > 2\u03c3(I), GoF = 1.031, final R factors R1 = 0.0511, and wR2 = 0.1396 for all data, Flack parameter (Parsons) = 0.010(4), CCDC deposit number 1451762.\u00a7Crystallographic data for A reasonable Parsons' Flack parameter value of 0.010(4) was obtained and the final R1 and wR2 values were 0.0511 and 0.1396, respectively. In an asymmetric unit, three independent guest molecules 6 (G1\u2013G3 in 6 (G1\u2013G3) show a 1R,2S absolute configuration, consistent with a previous report,6. From this, a plausible reaction mechanism to give 6 is suggested to involve reduction from the Re face of a 1R isomer of 5 that is kinetically resolved within the enzyme pocket.Treating tetralone G1\u2013G3 in were cleG1\u2013G3 is worthy of additional discussion. The methoxycarbonyl groups in G1 and G3 are located at the pseudo-axial position, while that in G2 is at the pseudo-equatorial position. For G2, intramolecular hydrogen bonding between the OH and COOMe groups was indicated by the short OO\u2013H\u2013O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC distance (\u223c2.8 \u00c5) that may stabilize this conformation. Presumably, this conformer exists in solution and the crystalline sponge traps both conformers at different binding sites, enabling the concomitant observation of both conformers.Conformational analysis of the observed guests 7) provided a more challenging task because three prochiral carbonyl carbons at C3, C11, and C17 can in principle generate 26 different compounds upon reduction of the carbonyl group(s). When steroid 7 was metabolized by baker's yeast on a 200 \u03bcg scale, HPLC analysis revealed the exclusive formation of a single metabolic product (hereafter denoted as 8).The structural and stereochemical analysis of a metabolite from adrenosterone . The increase in mass unit by 2.0 Da from 7 suggests a mono-hydrogenation of 7 at either a carbonyl or C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC group. The 1H NMR spectrum of 8 was, unfortunately, not conclusively able to determine its structure and stereochemistry because of overlapping signals. The unequivocal structure determination of 8 can be achieved, given that 8 is obtained only in microgram quantity, most reliably by the LC-SCD analysis.The parent ion peak of metabolite ca. 20 \u03bcg of a crude mixture obtained from the ether extract was purified using HPLC and subjected to guest soaking with a crystal of 1. After guest soaking at 50 \u00b0C for 2 d, the crystallographic analysis revealed three independent molecules of 8 (H1\u2013H3 in 1\u00b78: C72H48I12N24Zn6\u00b72.8(C19H26O3)\u00b71.5(C6H12), M = 4147.41, colorless plate, 0.28 \u00d7 0.08 \u00d7 0.07 mm3, monoclinic, space group C2, a = 34.7707(6) \u00c5, b = 14.8406(3) \u00c5, c = 31.2152(5) \u00c5, \u03b2 = 102.601(2)\u00b0, V = 15\u2009719.6(5) \u00c53, Z = 4, Dc = 1.749 g cm\u20133, T = 93(2) K, 2.9030\u00b0 < \u03b8 < 73.3970\u00b0, 29\u2009574 unique reflections out of 106\u2009306 with I > 2\u03c3(I), GoF = 1.005, final R factors R1 = 0.0788, and wR2 = 0.2259 for all data, Flack parameter (Parsons) = \u20130.008(8), CCDC deposit number 1451763.\u00b6Crystallographic data for All the structures revealed that the carbonyl group at C17 in 7 is stereoselectively reduced to a hydroxy group with an S configuration. The two carbonyl groups at C3 and C11 remain intact: typical C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO distances (1.19(3) and 1.20(3)) were observed at C3 and C11, respectively, and these carbon atoms still adopt a trigonal planar geometry. In contrast, elongation of the C\u2013O bond length of 1.41(3) \u00c5 and a tetrahedral geometry at C17 were observed, indicating that the carbonyl reduction took place only at C17. Notably, favorable host\u2013guest interactions were observed. For example, guest H1 is trapped by the host framework of 1 with C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7H\u2013C or C\u2013H\u00b7\u00b7\u00b7I hydrogen bond interactions.Thus, H1\u2013H3 in in an as1 often preferentially absorbs minor components, even low-level impurities may disturb efficient guest soaking. Given that trace metabolites separated using HPLC are normally contaminated with many impurities, great care should be taken in the purification steps. Therefore, pre-purification with PTLC or LC\u2013LC is highly recommended. Second, pre-analysis of the abundant parent compounds would be beneficial because soaking conditions optimized for the parent compounds can usually be applied to the analysis of their metabolites. Third, having successful results in this study, we are more convinced that the crystalline sponge method, coupled with HPLC separation, will innovate the structural analysis of scarce amounts of microbial products in natural product chemistry as well as in drug discovery.In conclusion, LC-SCD analysis has been demonstrated as a useful tool for structural analysis of trace microbial metabolites. Some important lessons are learned in this study working with trace microbial metabolites, which we have not noticed in the previous analysis of abundant synthetic compounds. First, a key to the success of the analysis is to obtain high purity samples of the microbial metabolites by HPLC separation. As the crystalline sponge Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Nitric oxide reacts with a NiSOD model complex to yield a thiolate-ligated/N-nitrosated {NiNO}10 species with unusually labile Ni\u2013NO bonds. + and NO with the model complex, Et4N[Ni(nmp)(SPh-o-NH2-p-CF3)] picolinamide; \u2013SPh-o-NH2-p-CF3 = 2-amino-4-(trifluoromethyl)benzenethiolate) and its oxidized analogue ox1, respectively. The ultimate products of these reactions are the disulfide of \u2013SPh-o-NH2-p-CF3 and the S,S-bridged tetrameric complex [Ni4(nmp)4], a result of S-based redox activity. However, introduction of NO to 1 affords the green dimeric {NiNO}10 complex (Et4N)2[{Ni(\u03ba2-SPh-o-NNO-p-CF3)(NO)}2] (2) via NO-induced loss of nmp2\u2013 as the disulfide and N-nitrosation of the aromatic thiolate. Complex 2 was characterized by X-ray crystallography and several spectroscopies. These measurements are in-line with other tetrahedral complexes in the {NiNO}10 classification. In contrast to the established stability of this metal-nitrosyl class, the Ni\u2013NO bond of 2 is labile and release of NO from this unit was quantified by trapping the NO with a CoII\u2013porphyrin (70\u201380% yield). In the process, the Ni ends up coordinated by two o-nitrosaminobenzenethiolato ligands to result in the structurally characterized trans-(Et4N)2[Ni(SPh-o-NNO-p-CF3)2] (3), likely by a disproportionation mechanism. The isolation and characterization of 2 and 3 suggest that: (i) the strongly donating thiolates dominate the electronic structure of Ni-nitrosyls that result in less covalent Ni\u2013NO bonds, and (ii) superoxide undergoes disproportionation via an outer-sphere mechanism in NiSOD as complexes in the {NiNO}9/8 state have yet to be isolated.Nitric oxide (NO) is used as a substrate analogue/spectroscopic probe of metal sites that bind and activate oxygen and its derivatives. To assess the interaction of superoxide with the Ni center in Ni-containing superoxide dismutase (NiSOD), we studied the reaction of NO Additionally, NO, while not isoelectronic with O2\u02d9\u2013, has the same ground state electronic structure with a singly occupied \u03c0* MO. Thus, NO interactions with the active sites of O2-activating/ROS-breakdown enzymes report coordination (inner-sphere substrate binding) and the extent of substrate bond activation from vibrational spectroscopic measurements of the N\u2013O and M\u2013NO stretching frequencies.Nitric oxide (NO) and its derivatives (termed reactive nitrogen species or RNS) play a vital role in a variety of mammalian physiological and pathological processes.III/II-coordination to cysteinato-S (CysS) and peptido-N donors (2\u02d9\u2013) and products (O2 and H2O2) of the SOD catalyzed reaction.3S2 donor set found in the active site.III oxidation state due to redox associated with the coordinated thiolates. One model from our lab, namely Et4N[Ni(nmp)(SPh-o-NH2-p-CF3)] picolinamide; see vs. Fc/Fc+ in DMF) that, based on EPR, UV-vis, MCD, and DFT computations, represents the electrochemical conversion from NiII in 1 to a NiII-thiyl \u2194 NiIII-thiolate resonance species termed ox1.2\u02d9\u2013 probe to define potential intermediates that may be traversed in the NiSOD mechanism. We report here, for the first time, the reactions and product characterization of NO (and NO+) with 1 and the well-defined analogue of NiSODox (ox1). NO/NO+ oxidize the aromatic thiolate ligand in ox1 and 1, respectively. However, introduction of NO to 1 affords the green dimeric {NiNO}10 complex (Et4N)2[{Ni(\u03ba2-SPh-o-NNO-p-CF3)(NO)}2] (2) via NO-induced loss of nmp2\u2013 as the disulfide and N-nitrosation of the aromatic thiolate .N donors , the forthiolate . While 21 with NOBF4 and in situ prepared ox1 with NO then reacts with NO to form the Ni-nitrosyl, formally a {NiNO}8 complex, assuming binding of NO and no other coordination sphere changes, using the notation defined by Enemark and Feltham.ox1 to generate the same species. Mixing a DMF solution of 1 with NOBF4 (1\u2009:\u20091) resulted in instantaneous bleaching of the solution, consistent with oxidation of the RS\u2013 ligand to disulfide (RSSR), and the appearance of a dark-red precipitate that was spectroscopically identified to be the neutral S,S-bridged tetramer [Ni4(nmp)4] classification,9/8 species is not entirely unrealistic in light of the strong donors present in 1 and in NiSOD, i.e., peptido-N and alkyl-thiolato-S.In the anticipation of isolating a Ni-nitrosyl as an analogue of a potential Ni-superoxo/peroxo catalytic intermediate of NiSOD, we examined the reaction of with NO . In theo4(nmp)4] .16 This \u2013NO bond .27 OveraII complex 1 with NO. In general, NO does not react with square-planar [Ni(nmp)(SR)]\u2013 complexes due to their diamagnetic nature. However, when R contains a potentially bidentate chelate, as in 1, a different course takes place. For instance, exposing a DMF solution of 1 with NO(g) for 30 s resulted in a gradual change of the solution from dark-red to green over several minutes. Workup of this reaction indicated a Ni-nitrosyl based on the strong double-humped peak in the N\u2013O stretching (\u03bdNO) region of the IR spectrum (vide infra). Subsequent crystallization of the bulk material from MeCN/Et2O at \u201320 \u00b0C resulted in green crystals of a dinuclear thiolate-bridged {NiNO}10 complex (Et4N)2[{Ni(\u03ba2-SPh-o-NNO-p-CF3)(NO)}2] (2) as depicted in 2 are distorted tetrahedral ,2 is analogous to the limited number of four-coordinate/S-bound Ni-nitrosyls,thiolate bonds3Ni\u2013NO/L2XNi\u2013NO complexes exhibit similar metric parameters. The coordinated nitrosamine is bent (N\u2013N\u2013O: 115.4\u00b0), i.e., sp2-hybridized nitroso-N, with N\u2013N and N\u2013O distances of 1.299 and 1.269 \u00c5, respectively. These values suggest a small degree of delocalization in the R\u2013N\u2013N\u2013O unit. However, the structure is more biased towards the nitrosamino R\u2013N\u2013\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO versus diazoate R\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013O\u2013 resonance form. To compare, the structure of syn-methanediazoate reflects the true double bond character in an authentic R\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013O unit.3)(ON2Ph-p-NO2)] (I)vs. amine-N as in 2) also afford similar structural parameters in the RNNO.III(P)(ONNR2)2]+ (P = porphyrin) complexes are nearly identical and result in a single 15N-sensitive peak in the IR due to overlapping \u03bdNN/\u03bdNO modes.As a control, we also explored the reaction of Ni4 = 0.73 ) resulti2 was characterized by a variety of spectroscopic methods. The solid-state IR spectrum (KBr matrix) of 2 exhibits two closely spaced, but well-resolved, \u03bdNO at 1759 and 1743 cm\u20131 , two IR-active N\u2013O vibrational modes are expected. The other feasible isomer of 2 would be of Ci symmetry and would display one IR-active N\u2013O stretch. Indeed, the IR spectrum of 2 in DMSO exhibits one \u03bdNO at 1784 cm\u20131 suggesting possible cis/trans-NO conversion in solution or thiolate-bridge splitting to yield a four-coordinate mononuclear {NiNO}10 with DMSO as the fourth ligand, i.e., [Ni(\u03ba2-SPh-o-NNO-p-CF3)(DMSO)(NO)]\u2013. The 1H NMR spectrum of 2 in CD3CN are similar and thus do not distinguish any of the proposed structures. Comparable IR spectral changes in the opposite direction are observed for the one other thiolate-supported anionic dinuclear {NiNO}10, (Et4N)2[Ni2(NO)2(\u03bc-SPh)2(SPh)2] (II), with trans NO ligands .10 complex.15N-sensitive peaks in the IR of 2 at 1342 and 1258 cm\u20131 are assigned as \u03bdNO and \u03bdNN, respectively. In comparison, a series of secondary nitrosamines display \u03bdNO: 1428\u20131463 cm\u20131 and \u03bdNN: 1035\u20131154 cm\u20131 in CCl4.2 to cause the corresponding downshift in \u03bdNO/upshift in \u03bdNN. While no paramagnetically shifted resonances are observed in the 1H NMR (CD3CN) of 2, several species are indicated in freshly prepared solutions . The 15N NMR spectrum of 15NO2- confirms multiple solution speciation with four major peaks in the range for nitrosamines and linearly coordinated NO 2[Ni(NO)(SPh)3] (III) and an uncharacterized [Ni(NO)(SPh)] species.2 is centered at m/z: 248.960 ]2\u2013 species through loss of the Ni-coordinated NO and one Ni (vide infra).Complex N Fig. S6 or DMSO-s Fig. S6 that are2, especially in donor solvents such as MeCN or DMF, gradually lose their green color to give red-brown solutions more reminiscent of square-planar NiII\u2013N2S2 complexes.3CN solutions of 2 exhibit multiple peaks in the 1H/15N NMR, and ESI-MS shows a new species with a Ni isotope pattern at m/z \u223c 249 (vide supra). This change is enhanced when vacuum is applied and FTIR spectra of these reaction mixtures lack any \u03bdNO suggesting the loss of coordinated NO from 2 to generate a new Ni species. Slow diffusion of Et2O into MeCN solutions of 2 that have been left standing for several weeks result in crystals of a square-planar (\u03c44 = 0.12) NiII compound where two N,S-chelating o-nitrosaminobenzenethiolato ligands bind to Ni in a trans configuration, viz. trans-(Et4N)2[Ni(SPh-o-NNO-p-CF3)2] (3) .i.e., short C\u2013S, C\u2013N distances of the coordinated o-aminobenzenethiolate3 is unremarkable from 2. 1H and 15N NMR of crystals of 3 are consistent with the X-ray structure and analogous to other nitrosamines confirm this formulation with peaks corresponding to [M\u20132Et4N]2\u2013 as the prominent peak 2] (3) . The bon3)2] (3) are simi2 (forming 3 among other products), solutions of 2 were mixed with the NO(g) trap [Co(T(-OMe)PP)] (T(-OMe)PP = 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine).2 and the CoII\u2013P (1\u2009:\u20092) in CH2Cl2 at RT for 24 h resulted in the {CoNO}8 complex [Co(T(-OMe)PP)(NO)] in \u223c70% avg. yield as quantified by 1H NMR (CD2Cl2) and further verified by IR spectroscopy using 15NO2- via1H NMR to confirm the fate of the {NiNO}10 complex 2. To eliminate bimolecular NO-transfer via a putative Co\u00b7\u00b7\u00b7NO\u00b7\u00b7\u00b7Ni intermediate, NO(g) release was further verified by vial-to-vial trapping reactions wherein a CH2Cl2 solution of the CoII\u2013P was separated from an MeCN solution of 2 to generate the {CoNO}8 porphyrin complex (80% avg. yield) as shown by 1H NMR and IR measurements Cl] , a common HNO (or NO\u2013) trap.10 has not been characterized as a particularly labile EF notation, we note that the majority of these complexes are cationic or neutral without coordinated thiolate ligands.10 complex III photochemically releases NO to [Co(TPP)] in MeCN suggesting some lability in the Ni\u2013NO bond. Furthermore, the RN\u2013NO bond is quite stable (as noted by formation of 3) and the energetically stabilized MOs that contribute to the electronic structure of 2 and 3 where HOMO\u20133 represents a bonding MO with primary contributions from \u03c3-NR and \u03c3-NO orbitals is released from Fig. S24. In cont Fig. S25.2 and 3 at the OLYP/def2-TZVPP level of theory. Pure functionals such as BP86 and OLYP were used for geometry optimization and single point energy calculations, respectively, as these functionals have been established to deliver better matches with experimental geometries in MNO systems.2 was performed with coordinates from the crystal structure to yield DFT-optimized complex 2* are slightly beyond the allowable tolerances for satisfactory DFT performance in small molecules .2. The computations also reasonably match the two closely spaced N\u2013O stretching frequencies for the symmetric and asymmetric \u03bdNO in the IR at 1730 and 1708 cm\u20131, respectively. The \u223c30 cm\u20131 downshift from 2 is likely due to a slight overestimation of Ni\u2013NO bond covalency arising from Ni-d\u03c0 backbonding. Previous calculations on three-10 complexes support a NiII\u20133NO\u2013 oxidation state assignment. This is comparable to high-spin nonheme {FeNO}7 systems that are classified as FeIII\u20133NO\u2013 (Stot = 3/2).3NO\u2013 serves as a strong \u03c0-donor to afford a highly covalent Fe\u2013NO bond.3NO\u2013 to result in diminished M\u2013NO bond covalency. This property has been established in the {FeNO}7 case, but not yet for {NiNO}10. Indeed, examination of the frontier MOs of 2* show that, much like other {NiNO}10 systems with Tp ligands2Ni core. The HOMO is antibonding in nature and suggests a thermally unstable structure. As expected from analogous {FeNO}7 systems, based on the increased donor strength of the anionic nitrosamine-N/thiolate-S supporting ligands in 2*, the covalency in the Ni\u2013N\u2013O unit is less than in TpNi\u2013NO complexes and rationalizes the observed lability of the Ni\u2013NO bond and the Ni(\u03bc-SR)2Ni core in 2.Density functional theory (DFT) computations have provided a deeper understanding of the electronic structure of a variety of metal nitrosyls,mplex 2* . Structu3* were performed in the same fashion as for 2*. Geometry optimized 3* is square-planar (\u03c44 = 0.09) with metric parameters on-par with the X-ray structure of 3 and within the error of the DFT method /S(p\u03c0) contributions (SR)]\u2013 complexes at least in the solid-state. Introduction of NO(g) can then result in either: (i) reduction of NiII to NiI and formation of NO+ that nitrosates the coordinated amine, or (ii) nitrosylation of Ni to yield {NiNO}10 with the electron originating from the coordinated thiolate of nmp2\u2013 to result in the disulfide. Our results do not differentiate either of these transformations, but the disulfide of nmp2\u2013 . In ligand rearrangement, the products would be a NiI\u2013N2S2 precursor to 3 (3-PC), an L\u2013NiI\u2013NO species (L = solvent), and free NO. Ultimately this NiI intermediate oxidizes 3-PC to generate NiII complex 3 and an L\u2013Ni0\u2013NO complex that would presumably release NO(g) as evidenced by the NO(g) trap experiments (vide supra). While the reaction mechanism for the conversion of 2-to-3 is likely more complex, similar chemistry has been proposed for N-heterocyclic carbene (NHC) Ni-nitrosyls.The formation of shown in to yield1 reacts with NO(g) in the NiII state to form the metastable {NiNO}10 dimeric complex 2via loss of the nmp2\u2013 ligand as the disulfide and N-nitrosation of the o-aminobenzenethiolate ligand. Reaction of NO with ox1, or NO+ with 1, only yields the S,S-bridged tetrameric compound [Ni4(nmp)4] through oxidation of the aromatic thiolate ligand. While any reaction with NO (S = 1/2) is generally unexpected for square-planar (S = 0) NiII complexes, this Ni-nitrosyl likely forms due to an equilibrium mixture of 1 and a tetrahedral (S = 1) or five-coordinate derivative (9 (reaction of 1 with NO) or {NiNO}8 (reaction of ox1 with NO) oxidation levels have yet to be defined and support an outer-sphere superoxide interaction in NiSOD. Although these EF notations have yet to be accessed, one would propose that NiSOD mimetics, especially with strong-field carboxamido-N and alkyl-thiolato-S donors, would surely stabilize such an electron poor species. Furthermore, the properties of complexes such as 2 extend to biology, where analogous S-bridged mononitrosyl species, i.e., Fe\u2013S clusters and tetrahedral (RS)3Fe\u2013NO complexes are proposed as intermediates in the repair of NO-damaged clusters.2 is stable in the solid-state but breaks down slowly in solution causing rupture of the Ni(\u03bc-SR)2Ni core and release of NO that was trapped in near quantitative yield with a CoII\u2013porphyrin receptor. The resulting NiII\u2013N2S2 complex 3 (coordination of two o-aminobenzenethiolate in trans configuration) was isolated and structurally/spectroscopically characterized as the ultimate Ni breakdown product with the nitrosamine unit still intact. This release may take place through a disproportionation mechanism (or through ligand rearrangement), as has been proposed in other Ni-nitrosyls, to a yet ill-defined Ni0 complex is high or generate other reactive intermediates of environmental significance such as hyponitrite (N2O22\u2013) in five-coordinate {NiNO}10 speciesIn conclusion, NiSOD model complex rivative . Even ifplex see .28,78 Heal mol\u20131 ) compareThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Post-polymerization ladderization is explored as a promising technique to boost the photo-catalytic activity of conjugated polymers. via post-polymerization annulation and oxidation techniques to generate rigidified, planarized materials bearing dibenzothiophene (cLaP1) and dibenzothiophene sulfone subunits (cLaP2). The high photocatalytic activity of cLaP1 (1307 \u03bcmol h\u20131 g\u20131) in comparison to that of cLaP2 (18 \u03bcmol h\u20131 g\u20131) under broadband illumination (\u03bb > 295 nm) in the presence of a hole-scavenger is attributed to a higher yield of long-lived charges , as evidenced by transient absorption spectroscopy. Additionally, cLaP1 has a larger overpotential for proton reduction and thus an increased driving force for the evolution of hydrogen under sacrificial conditions.Conjugated ladder polymers (cLaPs) are introduced as organic semiconductors for photocatalytic hydrogen evolution from water under sacrificial conditions. Starting from a linear conjugated polymer (cLiP1), two ladder polymers are synthesized Building block 1 was synthesized from 1,4-dibromobenzene -catalyzed Suzuki\u2013Miyaura cross-coupling reaction gave the parent polymer cLiP1.+-MecLaP) was dealkylated using NEt4Br to give the ladderized polymer cLaP1. Further oxidation of cLaP1 with H2O2 in glacial acetic acid gives cLaP2, which is a ladder-type analogue of the linear dibenzothiophene sulfone polymer (P10).301H{13C} NMR and IR spectra for previously reported compounds scale\" fill=\"currentColor\" stroke=\"none\">OS) and, in the fingerprint region, sharp peaks corresponding to wagging C\u2013H and C\u2013C vibrations for 1,4- and 1,2,4,5-substituted benzene subunits are observed and 1156 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">S PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOO), see also Fig. S11\u20131 consistent with a polymer containing 1,2,4,5-substituted benzene subunits. The signals of the triflate anion scale\" fill=\"currentColor\" stroke=\"none\">OS)) after the ladderization could not be detected due to the overlapping signals of the triflate anion. Thus, no further conclusions on the success rate of the annulation or the presence of defects (non-annulated aryl sulfoxide groups) could be made at this point. Upon oxidation to cLaP2, the spectrum shows two strong stretching vibrations scale\" fill=\"currentColor\" stroke=\"none\">S PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOO) indicating the oxidation of the dibenzothiophene moiety to dibenzothiophene dioxide was used to analyze the insoluble polymers: Fig. S10. Upon la Fig. S12. AdditiocLiP1 has limited long-range order, while cLaP1 and cLaP2 are amorphous can be found in the ESI.\u00a7UV-vis and fluorescence spectra for and this clearly shows that the system has a higher degree of conjugation as the annulation of neighbouring conjugated units reduces their respective torsion angles close to zero degrees as the system is rigidified show that polymer Fig. S22. UV-vis id-state : polymercLaP2 and cLaP1 compared to cLiP1 , as observed previously.31The fluorescence emission spectra in the solid state show the same bathochromic shifts as the UV-vis absorption spectra. Moreover, a smaller Stokes\u2019 shift and resolved vibronic coupling in the excitation spectrum of \u03bb > 295 nm and \u03bb > 420 nm; cLiP1 showed very limited activity (15 \u03bcmol h\u20131 g\u20131), even compared to poly(p-phenylene) (232 \u03bcmol h\u20131 g\u20131).cLaP1, the photocatalytic activity increased dramatically to 1307 \u03bcmol h\u20131 g\u20131. When the material was recovered and used again as a photocatalyst, an increase in the hydrogen evolution rate to over 2000 \u03bcmol h\u20131 g\u20131 was observed .The photocatalytic activity of these materials for hydrogen evolution from water in the presence of triethylamine (TEA) as a sacrificial electron donor was studied under broad-spectrum and visible light irradiation . Similarly, cLaP2 showed a 10-fold increase in activity (from 18 to 272 \u03bcmol h\u20131 g\u20131) under broadband illumination with platinum as co-catalyst .All of the materials were tested as synthesized without the addition of any additional metal co-catalyst. However, it has been shown that residual palladium originating from the Suzuki\u2013Miyaura coupling reaction can act as a co-catalyst.cLaP1 in H2O/TEA/MeOH mixtures using monochromatic light and these show that the hydrogen production is indeed photocatalytic . This is higher than previously reported for P1 (EQE420 nm = 0.4%)P12 (EQE420 nm = 1.4%)B-BT-1,4 (EQE420 nm = 4.0%)b,d]thiophene sulfone P7 (EQE420 nm = 7.2%)2O/TEA/MeOH mixture.External quantum efficiencies (EQEs) were estimated for Fig. S31. At 420 cLiP1, cLaP1 and cLaP2 in the presence of a H2O/TEA/MeOH mixture under a nitrogen atmosphere (cLaP1 was far greater (\u00d75\u201310) than those of cLiP1 and cLaP2, indicating an increase in long-lived photogenerated species. The TA spectrum of cLaP1 contains two distinct absorptions centred at ca. 500 and 630 nm that decay at different rates , 25 \u03bcs (630 nm) under N2).\u00b6We note that the lifetimes of all of the bands are dependent upon the history of the sample and tend to decrease after prolonged experiments. However, the signal at 500 nm is consistently shorter-lived compared to the signal at 625 nm. In the absence of methanol and TEA the long-lived TA bands at 500 and 630 nm are no longer observed spectroscopy. TA has been shown to be an effective tool for studying the formation and lifetime of electron\u2013polaron states in polymer photocatalysts for hydrogen evolution.mosphere . All throbserved . The rol Fig. S37. The obscLaP2 are far smaller than those of cLaP1 on the \u03bcs timescale, the kinetic traces recorded at 500 nm for cLaP2 do indicate an extremely long-lived (t50% = 0.3 s) photogenerated species. The presence of extremely long-lived charges, potentially with a low thermodynamic driving force, may also be a factor behind the low HER observed for cLaP2. To explore this observation further, Pt was added as a co-catalyst in the hope that it may be able to either intercept photoelectrons and prevent trapping or offer suitable catalytic sites to facilitate charge transfer into solution. cLaP2@Pt does show an improvement in HER, increasing from 18 \u03bcmol h\u20131 g\u20131 to 272 \u03bcmol h\u20131 g\u20131 + H+ and II: TEAR + h+ + H2O \u2192 diethylamine + acetaldehyde + H+), then the fact that cLaP1 is predicted to have only negligible driving force for the first step, in contrast to cLaP2, might suggest that differences in catalytic activity between cLaP1 and cLaP2 stems from differences in the driving force for proton reduction. In line with experimental UV-vis absorption spectra, ladder polymers cLaP1 and cLaP2 are predicted to have optical gaps that are \u223c1.0 and \u223c0.8 eV lower for cLaP1 and cLaP2, respectively, than for cLiP1 is also in line with experimental spectra.To gain insights into changes in the thermodynamic driving force for proton reduction and TEA oxidation within the investigated series of polymers, the IP and EA levels as well as optical gaps for varying oligomer lengths were estimated using a family of recently developed semi-empirical density functional tight-binding methods.cLaP1 outperforms its non-annulated parent polymer, cLiP1, significantly, and the optical properties of the material after annulation show a red-shift in the absorption onset. The ability of cLaP1 to absorb more photons while maintaining a hydrogen reduction driving force at least partially explains its higher photocatalytic activity, especially under filtered visible light. No significant changes in the optical properties were observed upon oxidation of cLaP1 to cLaP2, but the resulting dibenzothiophene sulfone material is almost inactive. This low activity of cLaP2 is surprising since TCSPC shows that cLaP2 has the longest weighted average lifetime of the exited state; significantly longer than those of cLiP1 and cLaP1. Also, the introduction of dibenzothiophene sulfone motifs into other polymer photocatalysts has been reported to give materials with high photocatalytic activity.cLaP2 has a reduced overpotential for proton reduction relative to cLaP1, while cLaP1 and cLaP2 both have a reasonable driving force for TEA oxidation. From a thermodynamic perspective, cLaP1 thus appears to be the best material in terms of combining thermodynamic driving force with light absorption. This is supported by TA measurements, which show the highest yield of long-lived charges in the case of cLaP1. From the TA data, it is clear that there is a direct correlation between the yield of long-lived charges present and the measured hydrogen evolution rate, suggesting that electron polaron states with lifetimes on the \u03bcs to ms timescale are required in order for hydrogen evolution to occur. This might rationalize the higher hydrogen evolution yields for cLaP1. The greater yield of long-lived photoelectrons may be related to more efficient hole scavenging at early timescales. The catalytic activity of the materials does not correlate with the residual palladium content, but it is unclear whether the threshold for an effect of the residual palladium on the photocatalytic performance has been reached.cLaP2 shows a persistent long-lived feature, which could be attributed to a deep-trapped charge . In both cases, we observed an increase in photocatalytic performance, but there was no evidence for higher charge carrier yields in the TA spectrum of the platinized cLaP2.The ladder polymer d charge , right, cLiP1, cLaP1 and cLaP2 can be rationalized by comparison of charge carrier lifetimes, light absorption, and thermodynamic driving forces. Compared with related linear polymers, such as P6/P60 and P7/P10 (cLaP1 (1307 \u03bcmol h\u20131 g\u20131) were found to be similar to those of its linear, non-ladderized analogues P6 (1660 \u03bcmol h\u20131 g\u20131) and P60 (1295 \u03bcmol h\u20131 g\u20131). However, when Pt was used as a co-catalyst, cLaP1@Pt outperformed P60@Pt under both broadband (2297 vs. 1703 \u03bcmol h\u20131 g\u20131) and visible light irradiation (1489 vs. 213 \u03bcmol h\u20131 g\u20131).In summary, the differences in photocatalytic activity in the series of d P7/P10 , the ideb,d]thiophene and dibenzothiophene sulfone polymers, we set out to synthesize a new class of ladderized conjugated polymer photocatalysts for photocatalytic evolution of hydrogen from water. Through post-polymerization ladderization, a planarization of the polymer chain and expansion of the \u03c0-system could be achieved, as evidenced by the bathochromic shift of the absorption edge. A significant increase in photocatalytic activity was measured for one ladder polymer (cLaP1) while the other (cLaP2) remained almost inactive. The difference in photocatalytic activity could be rationalized by analysis of the charge carrier lifetimes via TA spectroscopy and comparison of the driving forces derived from calculations. These results suggest that post-polymerization ladderization could be a valuable technique in the preparation of efficient photocatalysts and that ladder polymers containing other photocatalytically active subunits might be considered for future studies.Inspired by photocatalytically active dibenzo[There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "A modular dynamic covalent approach towards rigid aryleneethynylene covalent organic polyhedrons (COPs) and the mechanistic features were explored. D2h symmetric), dimer, or interlocked complex can be formed from monomers with the same face-to-edge angle but in different sizes. As alkyne metathesis is a self-exchange reaction and non-directional, the cyclooligomerization of multi-alkyne monomers involves both intramolecular cyclization and intermolecular metathesis reaction, resulting in complicated thermodynamic process disturbed by kinetic competition. Although a tetrahedron-shaped tetramer (Td symmetric) has comparable thermodynamic stability to a D2h symmetric tetramer, its formation is kinetically disfavored and was not observed experimentally. Aryleneethynylene COPs consist of purely unsaturated carbon backbones and exhibit large internal cavities, which would have interesting applications in host\u2013guest chemistry and development of porous materials.A dynamic covalent approach towards rigid aryleneethynylene covalent organic polyhedrons (COPs) was explored. Our study on the relationship of the COP structures and the geometry of their building blocks reveals that the topology of aryleneethynylene COPs strongly depends on the size of the building blocks. A tetramer ( In addition, ethynylene linked COPs exhibit much higher stability, compared to those linked by C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds or B\u2013O bonds, which are usually labile and prone to hydrolysis. Ethynylene-linked COPs have generally been prepared through kinetically-controlled Sonogashira or Glaser-type coupling.Molecular cages have shown great potential in molecular recognition, chemical sensing, catalysis, and gas adsorption/separation.COP-I and interlocked dimer complex (COP-II) through one-step alkyne metathesis cyclooligomerization of simple building blocks (1 provides high yielding of COP-I (72%) without any noticeable amount of interlocked species, monomer 2 predominantly forms interlocked complex COP-II (59%) along with a small amount of single dimer (6%). Intrigued by these results, we replaced the central panel of the monomers with a benzene ring, the smallest possible planar moiety available, wondering what would be the assembly product, interlocked complex or a dimer cage COP-III. The synthesis of tricarbazolyl-substituted benzene monomer 4 is straightforward scale\" fill=\"currentColor\" stroke=\"none\">\u2014PPT) and drive the metathesis equilibrium to completion. The alkyne metathesis of the monomer 4 was completed within 2 h under the catalysis of molybdenum(vi) carbyne complex prepared from molybdenum(vi) trisamide precursor EtC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tMo[N(t-Bu)Ar]3 and triphenolamine ligand (LN).Previously, we reported covalent assemblies of dimeric , and 2) .50,51 Botforward . . These 1H NMR patterns are highly similar to the D2h symmetric tetrameric cage (COP-V), whose structure has been unambiguously determined by single crystal X-ray analysis .6 produces symmetrical dimer COP-VII instead of a D2h symmetric tetramer in excellent isolated yield (84%), whereas 7 produces unknown precipitates with a trace amount of a dimer species, which was only observed in the MALDI-MS spectrum of the crude product mixture (16H33) are attached to the monomer in order to prevent the premature precipitation of the oligomeric/polymeric products from the reaction medium. Many attempts under various conditions failed to provide a soluble discrete species from monomer 7.It is unexpected to obtain mixture . In bothin situ by mixing Mo(vi) carbyne precursor Et PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tMo[NAr(tBu)]3 with multidentate triphenolsilane (LSi) or triphenolamine (LN) ligands. Both catalytic systems are highly active and have long lifetime, thus suitable for the cage synthesis.We used molybdenum carbyne catalytic system containing multidentate ligand in the alkyne metathesis cyclooligomerization approach. The catalyst solution was prepared Alkyl substituents are attached to prevent precipitation of the reaction intermediates from the solution. In order to reach the equilibrium with the predominant formation of the desired cage products, precipitation (kinetic traps) should be avoided, which cannot further participate in the dynamic equilibrium process. We tested various alkyl chains, linear or branched, long or short. We found alkyl substituents have little effect on the control of cage topologies, that being said, their main contribution is to maintain good solubility of reaction intermediates.Alkyne metathesis is an exchange reaction involving redistribution of alkylidyne units between two alkynes through the proposed formation of metallacyclobutadienes followed by cycloreversion . Since aCOP-I), an interlocked complex consisting of two dimer cages (COP-II), or a tetrameric cage with D2h symmetry (COP-IV) were obtained as the assembly products, respectively (e.g.COP-III) similar to COP-I from all the monomers with face-to-edge angle of 90\u00b0. At first glance, such dimers would be entropically- and enthalphically-favored, since they consist of the fewest possible monomer units connected with minimum angle strain. Therefore, we were surprised to observe the predominant formation of tetrameric COP-IV with D2h symmetry from monomer 4. However, when we further scrutinized the reaction pathway, we found the possible steric reasons responsible for the disfavored formation of a dimer. As shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, there are two possible metathesis outcomes: nonproductive and productive pathways. In order to form a dimeric cage, in the final cyclization step, the two arms have to approach each other in head-to-head conformation to undergo a productive metathesis COP-V and our original target, tetrahedron-shaped COP-VI.The next puzzling observation that attracted our attention was the formation of COP-V and COP-VI. It should be noted that the pendant arms (carbazole or benzene) attached to the central panels (porphyrin or benzene) can freely rotate in all the monomers tested and are not preorganized to form a particular product. Since monomers are multitopic and self-reacting, the initial formation of the dimeric intermediate I[1+1] likely triggers intramolecular cyclization to form macrocyclic intermediates II[1+1] and further to form cages , interlocked dimer complexes (COP-II) or a tetramer COP-IV or COP-V are kinetically preferred. Unless there is a strong thermodynamic driving force towards COP-VI, its formation could thus be limited. When a benzene ring is used as the planar central piece in a monomer, the pendant third arms on the macrocyclic intermediate II[1+1] prefer intermolecular cyclization to form a tetramer COP-IV or COP-V rather than forming a dimer cage, presumably due to the significant angle strain built up in the latter case as discussed previously. The assemblies of building blocks vary significantly with the choice of connecting chemical bonds that display different properties, such as kinetics, directional/non-directional, bond angles, and torsional/rotational freedoms. The dynamic assembly of COPs through alkyne metathesis, which is self-reacting, represents a complex system in which both thermodynamic and kinetic factors have to be considered.Intrigued by these observations, we next investigated the possible kinetic competition between the formation of rm cages . We indeI[1+1] dimer, followed by a series of subsequent intramolecular cyclizations rather than intermolecular reactions, would be preferred. Therefore, the formation of tetrahedron-shaped COPs (e.g.COP-VI), which involves more intermolecular metathesis steps, is kinetically disfavored. However, formation of such a cage structure can be predominant when there is a strong thermodynamic preference. The dynamic assembly through non-directional alkyne metathesis is complicated, in which both thermodynamic stability and kinetic factors could play critical roles in determining the final product. Although a general predictable relationship between building blocks and the assembled structures can be deduced by exploiting analogy between supramolecular and covalent assembly, accurate assessment of such a relationship still remains challenging considering the diversity of dynamic reactions and the complexity of dynamic assembly process. We carefully design building blocks based on literature precedents and experience, however, all too often our planning instead brings something surprising, yet logical. Our study will shed some light on this intriguing dynamic covalent assembly, which has shown tremendous potential in chemistry, material science and biology.The design and syntheses of aryleneethynylene COPs through dynamic alkyne metathesis cyclooligomeriztion approach and the effect of the size and geometry of the building units on the final outcome of assembly process were systematically investigated. Alkyne metathesis is a non-directional exchange reaction, which requires regioselective arrangement of ethynylene groups in order to proceed the productive pathway. As a result, the dynamic assembly through alkyne metathesis is significantly influenced by the geometrical properties of building blocks. Our study indicates the size of building blocks plays a significant role in determining the topology of the assembly structure. Depending on the size of top and bottom panels, dimeric cage, tetrameric cage, or interlocked dimeric cage were obtained from the monomers with the same face-to-edge angle. The starting materials for the cage products are designed to be multitopic and self-reacting, which inevitably raise the kinetic competition between intramolecular and intermolecular cyclization. The initial bimolecular reaction to form Supplementary informationClick here for additional data file."}
+{"text": "We report a 2D manganese benzoquinoid network that undergoes simultaneous redox switching of magnetic order and electrical conductivity. 4N)2[MnII2(L2\u2013)3] , as synthesized via post-synthetic counterion exchange. This material is paramagnetic above 1.8 K and exhibits an ambient-temperature electrical conductivity of \u03c3295 K = 1.14(3) \u00d7 10\u201313 S cm\u20131 (Ea = 0.74(3) eV). Upon soaking in a solution of sodium naphthalenide and 1,2-dihydroacenaphthylene, this compound undergoes a single-crystal-to-single-crystal (SC\u2013SC) reduction to give Na3(Me4N)2[Mn2L3]. Structural and spectroscopic analyses confirm this reduction to be ligand-based, and as such the anionic framework is formulated as [MnII2(L3\u2013\u02d9)3]5\u2013. Magnetic measurements confirm that this reduced material is a permanent magnet below Tc = 41 K and exhibits a conductivity value of \u03c3295 K = 2.27(1) \u00d7 10\u20138 S cm\u20131 (Ea = 0.489(8) eV), representing a remarkable 200\u2009000-fold increase over the parent material. Finally, soaking the reduced compound in a solution of [Cp2Fe]+ affords Na(Me4N)[MnII2(L2\u2013)3] via a SC\u2013SC process, with magnetic and electrical properties similar to those observed for the original oxidized material. Taken together, these results highlight the ability of metal benzoquinoid frameworks to undergo reversible, simultaneous redox switching of magnetic order and electrical conductivity.Materials with switchable magnetic and electrical properties may enable future spintronic technologies, and thus hold the potential to revolutionize how information is processed and stored. While reversible switching of magnetic order or electrical conductivity has been independently realized in materials, the ability to simultaneously switch both properties in a single material presents a formidable challenge. Here, we report the 2D manganese benzoquinoid framework (Me Materials with switchable magnetic order or values of electrical conductivity underpin the realization of modern electronic and spintronic technologies.4via pre-synthetic design or post-synthetic modification.2Despite this potential, the realization of inorganic materials that possess switchable magnetic order associated with large changes in electrical conductivity faces several key challenges.As an alternative to inorganic compounds, metal\u2013organic frameworks (MOFs) represent a powerful platform to design materials with tailored conductive and magnetic properties, owing to their extraordinary chemical versatility and tunability.nBu4N)[CrIIIMnIIL3] 2 paddlewheel-TCNQ derivative.Tc = 10 to 33 K, whereas the latter undergoes switching between a paramagnet and a permanent magnet with Tc = 88 K. In addition, MOFs with high electrical conductivities have only very recently been realized.Although early examples of MOFs were nearly exclusively electrically insulating due to their composition of diamagnetic, redox-inert carboxylate linkers and metal nodes,0.9Co0.1O2 can be controlled through electrolyte gating, where a maximum of 6-fold change in conductivity is observed.3GeTe2, where a similar up to 6-fold change in conductivity was observed in a 70-layer device.3 in several studies,4N)2[Mn2L3], wherein reversible, post-synthetic chemical reduction transforms a paramagnet into a permanent magnet with Tc = 41 K, with a concomitant 200\u2009000-fold enhancement of electrical conductivity. To our knowledge, this material is unique in its ability to simultaneously undergo redox switching of permanent magnetism and variation in electrical conductivity of several orders of magnitude.The coexistence of switchable magnetic order and electrical conductivity is exceedingly rare in any class of materials. For example, the magnetic ordering temperature of a dilute magnetic oxide Ti4N)2[Mn2L3]\u00b7xDMF (1) as a platform to target switching of magnetism and conductivity, as it features exclusively S = 0 L2\u2013 linkers between S = PBM data was replaced with SVG by xgml2pxml: 0001111111111110000000000000000001 0011000000000000000000000000000011 0011000000000000000000000000000110 0011000000000000000000000000001100 0011000000000000000000000000011000 0011000000000000000000000000110000 0011000000000000000000000001100000 0011111111100000000000000011000000 0000000000111100000000000110000000 0000000000000110000000001100000000 0000000000000011000000011000000000 0011000000000011000000110000000000 0011000000001100000001100000000000 0000110000001100000011000000000000 0000011111111000000110000000000000 0000000000000000001100000000000000 0000000000000000011000000000000000 0000000000000000110000000000000000 0000000000000001100000000011110000 0000000000000011000000001100001100 0000000000000110000000110000000011 0000000000001100000000110000000011 0000000000011000000000000000000011 0000000000110000000000000000000011 0000000001100000000000000000000011 0000000011000000000000000000001100 0000000110000000000000000000110000 0000001100000000000000000011000000 0000011000000000000000001100000000 0000110000000000000000011000000000 0001100000000000000000110000000000 0011000000000000000000110000000000 0110000000000000000000110000000000 1100000000000000000000111111111111\tMnII centres and should not exhibit magnetic order at finite temperatures owing to weak metal\u2013metal interactions solution of (Me4N)BF4 at 75 \u00b0C for 40 h, followed by subsequent rinses with DMF and diethyl ether (Et2O), produced (Me4N)2[Mn2L3]\u00b73.2Et2O (2) suitable for single-crystal X-ray diffraction analysis 2[Mn2L3]\u00b73.9THF (3). Taken together, these data establish the composition of the 2D framework in 3 to be [Mn2L3]5\u2013. Considering the Mn\u2013O distance in 3 (see below) and the rare presence of MnI in molecular compoundsII remains unchanged upon reduction. Instead, each L2\u2013 undergoes a one-electron reduction to give the semiquinoid radical L3\u2013\u02d9, as is supported by the Raman spectroscopy and magnetometry described in detail below.To determine the chemical formula and to tentatively assign the oxidation states of Mn and organic linker in the reduced compound, we employed inductively coupled plasma optical emission spectroscopy (ICP-OES), NMR spectroscopy, and combustion elemental analysis. First, ICP-OES analysis gave a Na\u2009:\u2009Mn ratio of 2.99\u2009:\u20092, consistent with a three-electron reduction per Mn3 in a solution of 3.3 equivalents of [Cp2Fe](BF4) in THF/CH3CN at ambient temperature for 6 days afforded brown hexagonal plate-shaped crystals of the re-oxidized material Na(Me4N)[Mn2L3]]\u22195.5THF\u22190.8CH5.5THF]\u22195.5THF\u22190.8CH0.8CH3CN (4). The Na\u2009:\u2009Mn ratio in 4 was determined to be 1.03\u2009:\u20092 by ICP-OES, indicating removal of only 2/3 of the original Na+ counterions. From a charge-balance standpoint, a Me4N+ counterion is expected to remain in the compound, and its presence in 4 was confirmed by NMR spectroscopy transformation mechanism. Second, according to optical microscopy images, shown as insets of Fig. S11\u2013S13,2\u20134 across the ab planes are approximately 100 \u03bcm, and this unchanged crystal size and morphology further supports a SC\u2013SC mechanism. Third, the reduction from 2 to 3 was performed in THF. Again, a dissolution\u2013recrystallization mechanism is unlikely due to the poor solubility of the Mn2+, Me4N+, and L2\u2013. Finally, according to the 13C NMR spectrum of the reaction supernatant from 3 to 4 \u00c5 relative to that of 2.158(3) \u00c5 for 1 indicates the retention of the high-spin MnII upon counterion exchange \u00c5 that is consistent with PXRD analysis (see below). The Me4N+ counterions occupy the same positions as in 2. The Na+ ions could not be found in the difference electron density map, suggesting they are not ordered on any lattice positions. Bond length analyses further support the reduction of the ligand. As shown in 2\u2013 to L3\u2013\u02d9.24A single crystal of the reduced framework compound 3 to 4, the diffraction quality of 4 dramatically improved . The Me4N+ ion is situated at the same position as in 2 and 3, but with 50% crystallographic occupancy. Similar to 3, the remaining Na+ was not located in the electron density map, suggesting it is disordered within the pore space. While there is no contraction of the Mn\u2013O bond, the C\u2013O and C\u2013C bonds are shortened and lengthened, respectively peak shifts slightly toward higher angle, from 8.510\u00b0 to 8.675\u00b0. This shift indicates a minor shortening of the interlayer distance by 0.20(3) \u00c5, likely due to the smaller size of the Me4N+ in 2 compared to Et4N+ in 1. The reduction from 2 to 3 results in an even more pronounced shift of the (001) peak, corresponding to a shortening from 10.18(2) to 9.35(1) \u00c5. This interlayer contraction likely stems from increased electrostatic interactions between [Mn2L3]5\u2013 layers and five interlayer cations, compared to two cations with [Mn2L3]2\u2013 in 2. As expected, the oxidation from 3 to 4 alters the charge of the framework from [Mn2L3]5\u2013 to [Mn2L3]2\u2013, and therefore causes an increase of the interlayer distance from 9.35(1) to 10.20(2) \u00c5, identical to that of 2.In order to probe the phase purity of crystalline ysis see . The pea3, which is most prominent in the range 2\u03b8 = 19\u201323\u00b0. Furthermore, in stark contrast to 2, in which the high-angle diffraction peaks are well preserved upon counterion exchange, the high-angle peaks in 3 are completely extinguished upon reduction. For 3, the increase in peak full width at half the maximum intensity (FWHM) at higher angle appears to be more pronounced than what is described by the Scherrer equation for crystallite-size related broadening, where FWHM is expected to be inversely proportional to cos\u2009\u03b8. Instead, such a significant increase in FWHM seems proportional to tan\u2009\u03b8 2[ZnII2(L2\u2013)3],2\u2013 in 1, 2, and 4 are unambiguously confirmed. Upon reduction, the C\u2013C bonds and the C\u2013O bond are contracted and elongated, respectively, in 3, as determined above from X-ray diffraction. Consequently, the corresponding vibrations should shift toward higher and lower energy, respectively. Only one prominent band is present in the spectrum of 3, centred at 1426 cm\u20131. This band most likely corresponds to overlapping peaks for both C\u2013C and C\u2013O stretches of L3\u2013\u02d9. Although these vibrations in 3 are slightly shifted relative to those of \u03bdC\u2013C = 1390 and \u03bdC\u2013O = 1488 cm\u20131 observed for (Cp2CoIII)1.43(Me2NH2)1.57[FeIII2(L3\u2013\u02d9)3],\u20131 for the dinuclear complex [CrIII2(tren)2(L3\u2013\u02d9)]3+ (tren = tris(2-aminoethyl)amine).2\u2013 in 1, 2, and 4, and as L3\u2013\u02d9 in 3.To confirm the ligand oxidation state assignments for nd 4 see . Based o2\u20134 at 295 K \u00d7 10\u201313 and 1.45(2) \u00d7 10\u201313 S cm\u20131, respectively. The nearly identical conductivity values for 2 and 4 support the conclusion that the redox switchability of conductivity is close to completely reversible. These low conductivity values fall in the typical range observed for MnII-based MOFs with diamagnetic linkers.26To probe the impact of the ligand oxidation state on the electronic communication and transport in these frameworks, two-contact-probe conductivity measurements were carried out for pressed pellets of 95 K see , upper. 3 exhibited a conductivity of \u03c3295 K = 2.27(1) \u00d7 10\u20138 S cm\u20131, representing a 200\u2009000-fold increase relative to the parent compound 2. To our knowledge, this is the largest change in electrical conductivity stemming from ligand-based redox chemistry in a MOF. This large increase upon chemical reduction indicates that reduction effectively injects electrons into the framework and thereby dramatically improves its charge carrier density. Notably, the ambient temperature conductivity value of 3 is among the highest of structurally-characterized Mn-based MOFs, and is only eclipsed by the value of \u03c3 = 8(1) \u00d7 10\u20135 S cm\u20131 reported for a single crystal of Mn2(TTFTB) . Note that the observed pressed-pellet conductivity values for low-dimensional materials, such as 3, are typically several orders of magnitude lower than single-crystal measurements, due to the anisotropic conducting pathway and grain boundaries.3 is likely much higher than the value for the pellet.The reduced compound 3 is comparable to the 1D radical-bridged chain compound (Cp2Co)Mn , which exhibits an ambient-temperature conductivity of \u03c3 = 8.6 \u00d7 10\u20138 S cm\u20131.3 is 2.2 \u00d7 104 times lower than that of the related compound (Cp2Co)1.43(Me2NH2)1.57[FeIII2(L3\u2013\u02d9)3], which exhibits a pressed-pellet conductivity of \u03c3300 K = 5.1(3) \u00d7 10\u20134 S cm\u20131.3+/Fe2+ and L2\u2013/L3\u2013\u02d9 pairs relative to Mn3+/Mn2+ and L2\u2013/L3\u2013\u02d9 pairs. In particular, the better energetic match of redox potential in the former pair might allow ligand radical electrons to transport through the Fe3+ centres via a transient valence tautomerism mechanism,The conductivity value of 2, and 275\u2013375 K for 3, respectively. As depicted in the lower panel of 2 and 3, suggesting the presence of thermally-activated charge transport in both materials. Fitting the data using the Arrhenius equation (see ESIEa = 0.74(3) eV for 2 and 0.489(8) eV for 3, respectively. The lowering of the activation energy upon reduction is likely due to the Fermi level rising closer to the conduction band as a consequence of doping electrons into the material.30To further probe the origin of the electrical conductivity, variable-temperature two-contact-probe pressed-pellet conductivities were measured in the temperature range of 310\u2013385 K for 4N)2[Mn2L3] is remarkable among magnets. As noted above, the ability to modulate electrical conductivity values over several orders of magnitude in permanent magnets constitutes a significant synthetic challenge, as low values of on/off ratio typically observed for inorganic compounds have hampered their practical use in field-effect transistors. For example, a six-fold change in conductivity was observed at 300 K for the dilute magnetic oxide Ti0.9Co0.1O2 upon applying a gate voltage of 3.8 V through an ionic liquid,3GeTe2 upon applying a 5 V bias through an ionic gate.8The 200\u2009000-fold redox switching of electrical conductivity in scale\" fill=\"currentColor\" stroke=\"none\">MnII ions per formula unit with g = 2. Upon lowering the temperature, \u03c7MT for 2 and 4 remains nearly constant down to ca. 150 K. Below 150 K, \u03c7MT for 2 undergoes a monotonic decrease to reach a minimum value of \u03c7MT = 0.74 cm3 mol\u20131 K at 2 K, indicating relatively weak antiferromagnetic superexchange coupling between S = PBM data was replaced with SVG by xgml2pxml: 0001111111111110000000000000000001 0011000000000000000000000000000011 0011000000000000000000000000000110 0011000000000000000000000000001100 0011000000000000000000000000011000 0011000000000000000000000000110000 0011000000000000000000000001100000 0011111111100000000000000011000000 0000000000111100000000000110000000 0000000000000110000000001100000000 0000000000000011000000011000000000 0011000000000011000000110000000000 0011000000001100000001100000000000 0000110000001100000011000000000000 0000011111111000000110000000000000 0000000000000000001100000000000000 0000000000000000011000000000000000 0000000000000000110000000000000000 0000000000000001100000000011110000 0000000000000011000000001100001100 0000000000000110000000110000000011 0000000000001100000000110000000011 0000000000011000000000000000000011 0000000000110000000000000000000011 0000000001100000000000000000000011 0000000011000000000000000000001100 0000000110000000000000000000110000 0000001100000000000000000011000000 0000011000000000000000001100000000 0000110000000000000000011000000000 0001100000000000000000110000000000 0011000000000000000000110000000000 0110000000000000000000110000000000 1100000000000000000000111111111111\t MnII ions. As such, 2 is a paramagnet at temperatures down to at least 2 K. Conversely, in the case of 4, \u03c7MT undergoes a slight increase below 90 K to a maximum value of \u03c7MT = 9.59 cm3 mol\u20131 K at 40 K, followed by a monotonic decrease to reach a minimum value of \u03c7MT = 1.09 cm3 mol\u20131 K at 2 K. This slight upturn in 4 upon lowering the temperature is most likely due to the contribution from a minuscule amount of reduced species remaining in the sample (see below).To probe the magnetic behaviour of the manganese-quinoid compounds, variable-temperature dc magnetic susceptibility data were collected for 3, the value of \u03c7MT = 9.60 cm3 mol\u20131 K at 300 K is relatively close to that of 9.875 cm3 mol\u20131 K expected for magnetically isolated two S = PBM data was replaced with SVG by xgml2pxml: 0001111111111110000000000000000001 0011000000000000000000000000000011 0011000000000000000000000000000110 0011000000000000000000000000001100 0011000000000000000000000000011000 0011000000000000000000000000110000 0011000000000000000000000001100000 0011111111100000000000000011000000 0000000000111100000000000110000000 0000000000000110000000001100000000 0000000000000011000000011000000000 0011000000000011000000110000000000 0011000000001100000001100000000000 0000110000001100000011000000000000 0000011111111000000110000000000000 0000000000000000001100000000000000 0000000000000000011000000000000000 0000000000000000110000000000000000 0000000000000001100000000011110000 0000000000000011000000001100001100 0000000000000110000000110000000011 0000000000001100000000110000000011 0000000000011000000000000000000011 0000000000110000000000000000000011 0000000001100000000000000000000011 0000000011000000000000000000001100 0000000110000000000000000000110000 0000001100000000000000000011000000 0000011000000000000000001100000000 0000110000000000000000011000000000 0001100000000000000000110000000000 0011000000000000000000110000000000 0110000000000000000000110000000000 1100000000000000000000111111111111\t MnII ions and three S = \u00bd L3\u2013\u02d9 radicals per formula unit scale\" fill=\"currentColor\" stroke=\"none\">MnII centres that are antiferromagnetically coupled to three S = \u00bd L3\u2013\u02d9 radical ligands, giving a net repeating spin of and g = 2.00.To confirm the quantitative ligand-based reduction and to further investigate the nature of magnetic coupling in II and L3\u2013\u02d9 in 3 are clearly illustrated in the variable-temperature magnetization plot, obtained from data collected under an applied dc field of H = 10 Oe. As shown in 3 gradually increases, following a Curie\u2013Weiss relationship to ca. 50 K and out-of-phase (\u03c7\u2032M) components of the ac susceptibility are observed below 42 K, establishing an ordering temperature of Tc = 41 K.\u03c6 = 0.0085, indicating the possible presence of some glassy behaviour or other complicated magnetization dynamics.31To precisely determine the ordering temperature of 3 was probed by collecting variable-field magnetization data at selected temperatures. As shown in 3 at 1.8, 10, 20 and 25 K were determined to be HCi = 300, 100, 40, and 12 Oe, respectively, with field-sweep rates of 0.6, 0.6, 0.2, and 0.1 Oe s\u20131. These HCi values of 3 are significantly lower than the iron analogue (Cp2CoIII)1.43(Me2NH2)1.57[FeIII2(L3\u2013\u02d9)3], which features HCi = 4520 and 2270 Oe at 1.8 and 10 K, respectively. This difference likely stems from the negligible magnetic anisotropy associated with high-spin MnII. Indeed, the behaviour of 3 as a soft magnet may render the compound useful in spintronics applications, where the direction of its spin polarization can be easily manipulated with a weak external magnetic field.1Finally, the presence of magnetic hysteresis of 3 and Fe3GeTe2, capacitive post-synthetic doping of charge carriers can tune ordering temperature and coercivity.Tc. Similarly, post-synthetic modulation of Tc has been demonstrated in the metal\u2013organic permanent magnets (nBu4N)[CrIIIMnIIL3],2NH2)2[Fe2L3],nBu4N)2[Fe2(dhbq)3].2 is a paramagnet above 1.8 K, whereas the reduced compound 3 is a permanent magnet below Tc = 41 K, and this redox process is chemically reversible. To our knowledge, the only other MOF that can undergo reversible switching between paramagnetism and magnetic order is a Ru2 paddlewheel-TCNQ derivative.The ability to switch between a paramagnet down to 1.8 K and a permanent magnet is nearly unprecedented. In oxide-based dilute magnetic semiconductors or other 2D solid-state inorganic materials such as CrIgnets nBuN[CrIIIMn4N)2[MnII2(L2\u2013)3], accessed through SC\u2013SC cation exchange, behaved as a paramagnet above 1.8 K with an ambient-temperature electrical conductivity of \u03c3295 K = 1.14(3) \u00d7 10\u201313 S cm\u20131 (Ea = 0.74(3) eV). Subsequent post-synthetic chemical reduction afforded the reduced semiquinoid compound Na3(Me4N)2[MnII2(L3\u2013\u02d9)3] via a SC\u2013SC process. This latter species was found to be a permanent magnet with a characteristic temperature of Tc = 41 K, and its ambient-temperature conductivity of \u03c3295 K = 2.27(1) \u00d710\u20138 S cm\u20131 (Ea = 0.489(8) eV) represents a 200\u2009000-fold increase relative to the oxidized form. Finally, the redox process was shown to be chemically reversible, with oxidation of the semiquinoid compound affording Na(Me4N)[MnII2(L2\u2013)3]. Future efforts will target related compounds that undergo simultaneous switching of magnetism and conductivity, but with higher magnetic ordering temperatures and higher values of electrical conductivity.The foregoing results demonstrate the ability of metal\u2013organic frameworks to undergo reversible redox-switching of magnetic order and electrical conductivity. The 2D manganese-benzoquinoid framework compound (MeThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Organic isocyanates are readily converted to methyl amine products through their hydroboration with HBpin in the presence of a \u03b2-diketiminato magnesium catalyst. N-,O-bis(boryl)hemiaminal species have been identified as intermediates during the reductive catalysis, the overall reduction and C\u2013O activation is metal-mediated and proposed to occur through the further intermediacy of well-defined magnesium formamidato, formamidatoborate and magnesium boryloxide derivatives. Examples of all these species have been identified and fully characterised through stoichiometric reactivity studies and the stability of the borate species leads us to suggest that, under catalytic conditions, the onward progress of the deoxygenation reaction is crucially dependent on the further activation provided by the Lewis acidic HBpin substrate. These deductions have been explored and ratified through a DFT study.Organic isocyanates are readily converted to methyl amine products through their hydroboration with HBpin in the presence of a \u03b2-diketiminato magnesium catalyst. Although borylated amide and We have shown that use of compound 1 enables the heterofunctionalisation and hydroboration of an assortment of multiply bonded and heteroatomic C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE scale\" fill=\"currentColor\" stroke=\"none\">E has attracted increasing attention given its potential applications in biofuels and fine chemical syntheses.1 was able to effect ester cleavage during the hydroboration of 3-methylnicotinate with pinacolborane (HBpin). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond and the formation of the methanol-equivalent H3COBpin through the use of a modified catalyst system derived from 1 and a B(C6F5)3 co-catalyst. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO activation. Although a Schwartz reagent-mediated reduction of isocyanates has been described as a straightforward and direct route to otherwise inaccessible formamides and the in situ hydroboration of t-BuN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO with HBpin catalysed by [Mg(THF)6][HBPh3] has been very recently reported to provide the bis-borylated hemiaminal, t-BuN(Bpin)CH2OBpin,Hydrodeoxygenation of carbonyl-containing compounds oxide, O(Bpin)2, through comparison with literature data PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond within the substrate with consequent formation of the N-borylated N-methyl isopropylamine 2 by-product in the 11B NMR spectra. Contrary to expectation, increased RNCO substituent steric demands provided generally faster reaction times; R = i-Pr (entry 1) and t-Bu (entry 5) evidenced complete consumption of the isocyanate in less than 4 hours compared to Et (entry 3) and n-Pr (entry 4) both of which required 21 hours. The increased reactivity associated with enhanced alkyl substituent steric demands also coincided with the onset of secondary side reactions. Although attempts to identify the products of these side reactions were unsuccessful it is likely that oligomerisation of the isocyanates is competitive with the reductive C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO cleavage.N-phenyl and N-mesityl (Mes) isocyanate substitution provided ca. 90% conversion in 24 hours (entries 7 and 8), while an increase of the N-aryl substituent's steric demands to 2,6-di-isopropylphenyl (Dipp) resulted in a significantly reduced conversion during the same time period (entry 9).Extension of this reactivity to other commercially available alkyl isocyanates provided similar reactivity to i-PrNCO. Entries 1 to 6 in 1 at room temperature leads to stoichiometric formation of n-BuBpin and a may act as a source of a heteroleptic magnesium hydride species.2, the formation of which was clearly apparent from the appearance of a new downfield (1H by relative integration) singlet resonance at \u03b4 7.92 ppm in the resultant 1H NMR spectrum. Crystallisation of compound 2 direct from the reaction solution provided crystals suitable for a single crystal X-ray diffraction analysis. The results of this analysis was readily located and freely refined, clearly demonstrating that there was no significant Mg\u2013H interaction in the solid state. The structure of compound 3 is reminiscent of a previously described borate species resulting from addition of HBpin to a magnesium formamidinate supported by the same \u03b2-diketiminate ligand.3Addition of one equivalent of HBpin to a solution of compound N-borylated formamidine, DippN(Bpin)HC(O) , by prolonged (>24 hours) heating of samples of compound 3 in d8-toluene either at 60 \u00b0C or 80 \u00b0C failed to provide any evidence of onward reactivity. Similar treatment of 3 at the higher temperature of 100 \u00b0C for 16 hours, however, resulted in the production of a single new \u03b2-diketiminato species (4) along with the methylene imine, DippN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2, which was tentatively identified through the appearance of an AB spin system in the 1H NMR spectrum with signals at \u03b4 6.90 and 7.25 ppm. The identity of compound 4 was confirmed through the isolation of single crystals suitable for an X-ray diffraction experiment. The results of this analysis revealed that 4 was a dimeric magnesium boryloxide species scale\" fill=\"currentColor\" stroke=\"none\">CH2 as the mode of C\u2013O activation, the elevated temperature required for this reaction militates against its operation during the catalytic reactions summarised in 3 and a single equivalent of HBpin was, thus, undertaken. Although no consumption of 3 took place at room temperature, heating of this d8-toluene solution at 60 \u00b0C for 8 hours resulted in the predominant formation of DippN(Me)Bpin along with a variety of \u03b2-diketiminato magnesium species which could not be identified with any meaningful level of confidence. In an attempt to shed further light on this reactivity, compound 1 was reacted with 3 molar equivalents of HBpin and 2 equivalents of DippNCO. This reaction at room temperature surprisingly resulted in the generation of the amidate derivative (2) along with the concomitant production of a single new compound (5). This latter species was identified as the bis-borylated hemiaminal, Dipp(pinB)NCH2OBpin, through the appearance of a distinctive methylene singlet resonance at \u03b4 5.35 ppm in the 1H NMR spectrum and two broad signals of equal intensity at \u03b4 28.3 and 24.8 ppm in the corresponding 11B NMR experiment. Furthermore, continued treatment of this reaction mixture with additional equivalents of HBpin and DippNCO in a 2\u2009:\u20091 ratio provided for the catalytic production of compound 5.While the formation of compound 1 to provide compound 5 and the analogous N-mesityl species (6) within 10 minutes at room temperature oxide, O(Bpin)2, by-product.Attempted extension of this bis-borylation protocol to PhNCO and the range of 6 and Jones' \u03b2-diketiminato magnesium hydride complex, [CH{C(Me)NDipp}2MgH]2.1H NMR spectroscopy demonstrated that heating to 60 \u00b0C resulted in the generation of the N-borylated methyl amine, pinBN(Me)Mes, along with the magnesium boryloxide (4) (eqn (2)). A further reaction performed by addition of compound 6 to a d8-toluene solution of the pre-catalyst (1) and HBpin provided a similar result. Subsequent addition of HBpin to either of these reaction mixtures or to a solution of an isolated sample of compound 4 in d8-THF resulted in the consumption of the magnesium boryloxide with concomitant production of (pinB)2O and the regeneration of [CH{C(Me)NDipp}2MgH]2 (eqn (3)). Although these routes to compound 4 and its reactivity with HBpin suggest that the C\u2013O cleavage reaction is primarily magnesium mediated, it is notable that heating of a solution of compound 6 at 60 \u00b0C for 12 hours in the absence of any other reagents also resulted in the consumption of ca. 50% of the hemiaminal and production of (pinB)2O and the methylene imine, MesN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2.To provide further insight into the role of such hemiaminal species as potential intermediates during the course of the C\u2013O activation catalysis, a reaction was carried out between compound 5. Although a 1H NMR spectrum recorded five minutes after the initiation of the catalytic reduction of DippNCO with two equivalents of HBpin catalysed by 1 demonstrated the facile production of compound 5, the formation of this species was accompanied by a new compound (7) characterised by the appearance of a high frequency singlet resonance at \u03b4 9.04 ppm in the 1H NMR spectrum. Compound 7 was assigned as the N-borylated formamidine, DippN(Bpin)HC(O), which was completely consumed upon completion of the reaction. Several attempts to generate compound 7 by the reaction of a single equivalent of HBpin and DippNCO in the presence of 10 mol% 1 resulted in the consumption of only 50% of the isocyanate starting material and the production of compound 5. A similar reaction performed at lower catalyst loading (0.1 mol%) and in the minimum amount of toluene solvent, however, resulted in the formation of a significant quantity of crystalline material. Mechanical separation of single crystals formed within this material enabled a series of single crystal X-ray diffraction analyses which showed it to be primarily a mixture of compound 5 and compound 7. The results of the analysis of compound 7 are shown in An additional intermediate was identified during our investigation of the catalytic production of compound in situ monitoring (1H NMR spectroscopy) of a reaction of HBpin and i-PrNCO catalysed by 10 mol% 1 at 60 \u00b0C. en route to the ultimate methyl amine product HC(O), analogous to compound 7, was observed to accumulate during the initial 15 minutes of the reaction prior to any observable methyl amine formation . After this time, however, it was consumed simultaneously with the appearance of significant quantities of a bis-borylated hemiaminal derivative, i-Pr(pinB)NCH2OBpin, analogous to compounds 5 and 6, which was apparent as a persistent singlet resonance at \u03b4 5.08 ppm . A further low field singlet was observed at \u03b4 7.80 ppm . Once evolved, this latter resonance persisted at an effectively constant intensity throughout the course of the catalysis. This chemical shift is reminiscent of the signal associated with the amidato methine proton observed for compound 3 (\u03b4 7.69 ppm) and leads us to postulate that a borate species with a comparable constitution is also formed in a steady state concentration as a key intermediate during the reduction of i-PrNCO. The initial appearance of this species was accompanied by the emergence of a clear AB spin system , which may be cautiously assigned to the methylene imine, i-PrN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2. This small molecule is evidently consumed, however, at more mature phases of the catalysis.The significance of these observations with respect to the catalytic reactivity was assessed by ), i-Pr(pinB)NCH2OBpin and i-PrN(Bpin)Me during the reduction of i-PrNCO. N-borylated amidine production in our recent report of carbodiimide hydroboration catalysed by 1.3 in the absence of further HBpin.Evidence for a sequential mechanism was provided by examination of the temporal evolution of the signals assigned to i-PrN(Bpin)HC(O) to provide the transient magnesium hydride (or borohydride) necessary to generate formamidate and borate intermediates analogous to compounds 2 and 3. The apparent stability of this latter compound mitigated against its direct thermal conversion to boron-containing small molecules at temperatures relevant to the catalysis. We, thus, suggest that the most kinetically accessible cycle necessitates breakdown of a similar borate species to produce RN(Bpin)HC(O).Although these observations attest to a complex mechanistic landscape, we postulate that the gross features of this reactivity may be rationalised by the generic mechanism for the reduction of RNCO illustrated in N-borylated formamidine were observed to accumulate during the early stages of the catalytic reduction of i-PrNCO, this species is apparently consumed through its onward reaction with magnesium hydride. We have not identified any resultant magnesium hemiaminalate species but suggest that compounds of this type will be rapidly consumed through further B\u2013H/Mg\u2013O metathesis to yield R(pinB)NCH2OBpin. The ultimate production of RN(Bpin)Me and closure of the catalytic cycle are then predicated upon a sequence of C\u2013O/Mg\u2013H and Mg\u2013O/B\u2013H metathesis steps reminiscent of the stoichiometric reactivity summarised for the isolable species 6 and 4 in eqn (2) and (3).We postulate that this process occurs by the necessary activation of the borate intermediate through its interaction with a further equivalent of Lewis acidic HBpin prior to intramolecular boron to magnesium hydride transfer. This process is, thus, reminiscent of our recent reports on related magnesium borate species identified during the hydroboration of organic carbodiimides and nitriles. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2. It is notable that appreciable quantities of i-PrN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 were only observed after the generation of significant amounts of i-Pr(pinB)NCH2OBpin during the reduction of i-PrNCO. We infer, therefore, that this small molecule is generated by the direct decomposition of i-Pr(pinB)NCH2OBpin rather than any higher energy magnesium-centered process and implicates a second plausible pathway for the production of i-PrN(Bpin)CH3.Although our observations suggest that this reaction sequence predominates under the mild conditions applied during catalysis, the mechanism must also reconcile the production and consumption of RN2 and 3 were found to be formed by an overall exothermic sequence of isocyanate Mg\u2013H insertion and subsequent reaction of the as-formed magnesium amidate with HBpin. As deduced from the stability of compound 3, the production of a borylated formamide analogous to compound 7 entails the interaction of the magnesium amidatoborate with a second equivalent of HBpin to enable the necessary boron to magnesium hydride transfer. While the production of compounds such as 7 requires the traversal of a several higher energy transition states and intermediates, mainly associated with the HBpin insertion into the Mg\u2013O bond of 3 at a cost of 5.0 kcal mol\u20131 and the need for B\u2013O bond disruption , these processes occur prior to a kinetically facile and highly exothermic re-insertion of the carbonyl function into the magnesium hydride bond. The subsequent generation of bis(boryl)hemiaminals such as 5 and 6 occurs via B\u2013H/Mg\u2013O sigma bond metathesis, which incurs an enthalpic penalty of some 10.2 kcal mol\u20131 associated to the formation of a monomeric Mg\u2013H complex rather than its very stable dimeric form. However, while this is lower than the entrance channel , 5 can only be considered as an intermediate in the course of the formation of methyl amine product in line with the proposed catalytic cycle. The ultimate cleavage of the C\u2013O bond and production of the methyl amine product requires traversal of an energy barrier of some 40.0 kcal mol\u20131 involving the further interaction of these reduced intermediates with a magnesium hydride, whereupon the formation of a boryloxide derivative similar to compound 4 is significantly exothermic . Dimerisation and a further Mg\u2013O/H\u2013B metathesis with a further molecule of HBpin yield (pinB)2O with the regeneration of the magnesium hydride scale\" fill=\"currentColor\" stroke=\"none\">O bond. The sequential nature of this reactivity indicates that it may be further generalised to the targeted cleavage of the C\u2013O bonds in alternative molecular and, potentially, even macromolecular species. We are continuing to study these possibilities.In conclusion, we describe a mild protocol for the catalytic transformation of the isocyanate function to a methyl amine. The activation of the heterocumulene occurs through a magnesium-centered hydroboration and ultimately the complete cleavage of the CSupplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The unique abilities of homo-oligo-adamantyl peptides to adopt \u03b1- and \u03b3-turn conformations are demonstrated by X-ray diffraction, and NMR and FT-IR absorption spectroscopies. N\u03b1-formyl-adamantyl tripeptide iso-propyl and tert-butyl amides are respectively found to adopt an isolated \u03b1-turn and an incipient \u03b3-helix conformation by X-ray diffraction crystallography. The shortest example of a single \u03b1-turn with ideal geometry is observed in the crystalline state. In solution both peptides predominantly assume \u03b3-helical structures.The unique abilities of homo-oligo-adamantyl peptides to adopt \u03b1- and \u03b3-turn conformations are demonstrated by X-ray diffraction, and NMR and FT-IR absorption spectroscopies. Assembled by an Ugi multiple component reaction strategy, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7H\u2013N hydrogen bonds and minimization of side-chain steric interactions. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and NH groups, respectively, of residues i and i + 4 (\u03b1-turn13). On the other hand, a single \u03b1-turn in short linear peptides (\u22645 amino acid residues), unambiguously authenticated by X-ray diffraction analysis, is rare,i + 2 \u2192 i or C7) \u03b3-turn structures5Helices constitute the most abundant peptide and protein secondary structures in nature and play vital roles in protein\u2013protein recognition.\u03b1,\u03b1-Disubstituted glycines are known to be able to constrain peptides to adopt distinct secondary structures.\u03c6 and \u03c8 torsion angles adopted by these residues are typically contingent on the substituent size and nature. Specifically, C\u03b1,\u03b1-dimethylglycine and C\u03b1-methylated analogs of proteinogenic amino acids favor folded backbone conformations in the 310-/\u03b1-helical region ,10-helices,16 homo-oligomer.n-propyl, phenyl or benzyl substituents adopt predominantly fully-extended (C5) conformations .Ci.e., N\u03b1-unprotected N-carboxyanhydride, N\u03b1-acetyl/trifluoroacetyl 5(4H)oxazolones and EDC (N-ethyl-N\u2032-3-(dimethylaminopropyl)carbodiimide)/HOAt ] to provide simple dipeptides with N-terminal Adm residues.3) precursor of the \u03b1-amino group,12Although homo-oligomers of Aib have been commonly prepared and studied,\u03b1,\u03b1-disubstituted glycines with very bulky side chains, the Ugi reactions of adamantan-2-one has previously delivered -Adm-Gly- dipeptides, albeit in modest yields.3-NHR tripeptides 1 and 2 . A concomitant combination of X-ray diffraction crystallography and spectroscopic methods has demonstrated that the Adm residue can favor the elusive single 13-membered intramolecularly hydrogen-bonded \u03b1-turn, as well as the almost completely developed \u03b3-helix conformations.Among the potentially useful, alternative methods for synthesizing CN\u03b1-formyl-Adm homo-tripeptides 1 and 2 began respectively by reacting adamantan-2-one with iso-propyl and tert-butyl isocyanides 3 in methanol (MeOH) with ammonium formate dissolved in the minimum amount of water between \u20135 to \u201310 \u00b0C for 1\u20132 hours. After aqueous workup and column chromatography, isocyanides 5 were isolated as solids in \u226590% yields. Exposure of isocyanides 5 to similar Ugi conditions as those described above gave homo-dipeptides 6 as solids in \u226585% yields. Subsequently, formamide to isocyanide conversion went smoothly using the POCl3 conditions to afford isocyanides 7. Finally, the desired homo-tripeptides 1 and 2 were synthesized using the Ugi approach. However, the reaction was relatively sluggish, and required heating for 2 days in the presence of excess ammonium formate to provide solid products after chromatography in about 60% yields.The synthesis of 1 and 2 were determined by single crystal X-ray diffraction (1 (R = iPr) and ESI\u20201 was also crystallized from solvents of varying polarity within the limits imposed by solubility. Crystals suitable for X-ray diffraction analysis were obtained from three different systems; however, all gave the identical \u03b1-turn structure, within experimental error \u00c5 from the nitrogen atom of Adm(3), suitable for forming a 10-membered intramolecular hydrogen bond (\u03b2-turn),al error .1, the average \u03c6 and \u03c8 torsion angles over the three Adm residues differ only by 6\u00b0 and 10\u00b0, respectively, from the canonical values based on statistical analysis of \u03b1-helices in crystalline peptides.1 represents the shortest peptide sequence giving rise to an isolated \u03b1-turn of regular geometry.As stated above, crystallography of single \u03b1-turns is very unusual. \u201357\u00b0, \u20135\u00b0 differ 2, the backbone torsion angles .\u03c61 value, compared to that of \u03c62, in contrast to the less than 2\u00b0 difference in the values of \u03c81 and \u03c82. The distortion of \u03c61 weakens the N2\u2013H\u00b7\u00b7\u00b7O0 intramolecular hydrogen bond, but enables the N1\u2013H group to participate in an intermolecular hydrogen bond with the O2 atom of a symmetry related molecule (ESI\u03c8 torsion angle of Adm(3) is forced to adopt a value (\u2013113.2\u00b0) which prevents the C-terminal amide NH group from approaching the carbonyl oxygen of Adm(2) at a suitable hydrogen-bond distance.In the X-ray diffraction structure of tripeptide n angles and distn angles and ESI\u2020 \u03c6, \u03c8 = 7\u00b0,\u201375\u00b0.5 1 (1.254 g cm\u20133) was less than that of 2 (1.302 g cm\u20133). The packing mode of tripeptide 1 features one N\u2013H\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC hydrogen bond, three C\u2013H\u00b7\u00b7\u00b7O contacts within the distance of 2.66 \u00c5,2, intermolecular interactions include one N\u2013H\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC hydrogen bond, as well as two C\u2013H\u00b7\u00b7\u00b7O contacts and nine aliphatic H\u00b7\u00b7\u00b7H contacts in the range 2.10\u20132.39 \u00c5. Within the sum of the van der Waals radii, the latter may stabilize the packing and account for the higher density of crystals of 2 through London dispersion.21The calculated density for the crystals of 1 and 2 in solution, NMR and FT-IR absorption spectroscopic methods were employed.To study the conformation of peptides 1 and 2 in CDCl3 were achieved by a combination of COSY and HMBC experiments, the latter optimized to identify long-range, through-bond J couplings caused significant downfield shifts for only the formamide NH proton signal, suggesting that this group is exposed to solvent in contrast to the other NH proton signals which exhibited limited variations in chemical shifts (0.02 to 0.22 ppm). This different behavior of the formamide NH proton is already evident at the very beginning (2% DMSO in CDCl3) of the solvent titration curves the formamide NH signal relative to those of the other amide protons. The NH chemical shifts of the latter protons varied less with temperature in the solvent of lower polarity CDCl3 (\u0394\u03b4/\u0394K = \u20130.3 to \u20131.5 ppb) than in DMSO (\u0394\u03b4/\u0394K = \u20131.0 to \u20133.3 ppb K\u20131).Solvent shielded and exposed NH protons were examined by studying influences of changes in environment on the chemical shifts of their signals . Amide pn curves . Similar2 grown from DMSO (bis-DMSO solvate) highlighted the presence of only one \u03b3-turn in each of the two independent but similar peptide conformers A and B in the crystal matrix (\u03c6 and \u03c8 torsion angles of Adm(1) in the two peptide conformers were \u201375.4\u00b0, 74.8\u00b0, and 76.6\u00b0, \u201369.9\u00b0, respectively. Three intermolecular hydrogen bonds were observed between each peptide and two co-crystallized DMSO solvent molecules: one between the Adm(1) NH group and the oxygen atom of one molecule of DMSO, and the other two between the Adm(3) and tert-butyl amide NH groups together with the oxygen atom of a second DMSO molecule. In each peptide conformer, Adm(2) and Adm(3) were helical but of opposite screw sense: \u03c62, \u03c82, \u03c63, \u03c83 = 59.8\u00b0. 64.1\u00b0, \u201359.0\u00b0, \u201355.5\u00b0 (in A); \u201360.0\u00b0, \u201366.9\u00b0, 61.1\u00b0, 58.5\u00b0 (in B).Notably, an X-ray diffraction analysis of crystals of peptide l matrix and ESI\u2020\u20131), the FT-IR absorption spectra of peptides 1 and 2 in CDCl3 solution accompanied by a much broader band with maximum near 3300 cm\u20131 (hydrogen-bonded NH groups).versus free N\u2013H stretching bands were found over the concentration range 10.0 mM\u20130.1 mM is likely responsible for the outcome in the crystal states (\u03b1-turn or \u03b3-turn). An example has already been reported of two homo-peptides differing only in their C-terminal group (ethyl ester vs. tert-butyl ester) giving rise to two different conformations in the crystal state, but adopting apparently the same conformation in solution.Considering the marginal role of the crystallization solvent properties to significantly bias the conformations of peptides \u03b1,\u03b1-disubstituted glycines bearing bulky side chains using the Ugi multiple component reaction has been achieved and applied in the synthesis of N\u03b1-formyl adamantyl tripeptide amides 1 and 2. Conformational analysis has revealed the potential for the Adm residue to favor the unprecedented single \u03b1-turn with ideal \u03c6 and \u03c8 torsion angles and an incipient \u03b3-helical structure. Notably, the overwhelming majority of C\u03b1-tetrasubstituted \u03b1-amino acids prefer 310-helices, which are generated by consecutive type-III (III') \u03b2-turns, and subsequently \u03b1-helix conformers.10-helix appears to be unavailable to the Adm residue. In the \u03c6 and \u03c8 space, the most significant difference between the two conformations is the value of the \u03c8 torsion angle. For the Adm residue, typical \u03c8 values for right- and left-handed 310-helices have never been observed, likely due to a destabilizing aliphatic C\u2013H\u00b7\u00b7\u00b7O interaction between the pro-R or pro-S \u03b3-CH2 groups with the carbonyl oxygen atom, which would require an energetically disfavored H\u00b7\u00b7\u00b7O separation of the order of 2.10 \u00c5.\u03c8 values to those observed in the \u03b1-helical turn of peptide 1 (in the range \u201346.5\u00b0 to \u201359.6\u00b0) which resulted in H\u00b7\u00b7\u00b7O separations between 2.23 and 2.33 \u00c5, and to a larger extent in a \u03b3-turn conformation (peptide 2), in which the observed H\u00b7\u00b7\u00b7O separations are >2.40 \u00c5.To summarize, a novel method for assembling sterically congested peptides from C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO)\u2013 derivatives] have already found important applications in medicinal chemistry as drugs to treat parkinsonism and related syndromes, and as antiviral agents to combat type-A influenza virus in humans.26Considering the power of the Ugi multiple component method reported in this work for synthesizing sterically hindered peptides, potential now exists to harness bulky residues for various studies in peptide science. The unique \u03b3-helical folding pattern which was observed both in solution and in the crystal state, as well as the fascinating diamondoid hydrocarbon side chains may similarly lend themselves for novel applications. In this connection, adamantane-functionalized compounds [particularly its \u2013NH- and \u2013C(There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "New tris-amidinate actinide complexes containing a rare O-bound terminal phosphaethynolate (OCP\u2013) ligand were synthesized and fully characterized. tris-amidinate actinide complexes containing a rare O-bound terminal phosphaethynolate (OCP\u2013) ligand were synthesized and fully characterized. The cyanate (OCN\u2013) and thiocyanate (SCN\u2013) analogs were prepared for comparison and feature a preferential N-coordination to the actinide metals. The Th(amid)3(OCP) complex reacts with Ni(COD)2 to yield the heterobimetallic adduct (amid)3Th(\u03bc-\u03b71(O):\u03b72-OCP)Ni(COD) featuring an unprecedented reduced (OCP\u2013) bent fragment bridging the two metals.New Origtris-amidinate chloride precursors MCl(amid)3 benzamidinate) and Na(OCP)(dioxane)2.9 affords the desired phosphaethynolate complexes M(OCP)(amid)3 as block-shaped crystals in 76% and 63% isolated yields, respectively is significantly shifted downfield (\u03b4 = \u2013334 ppm) compared to that reported for Re scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO)(CO)2(triphos)\u03b4 = \u2013398 ppm) and alkali and alkaline earth phosphaethynolate salts (\u03b4(31P) range: \u2013362 to \u2013397 ppm).iv) center, the 31P NMR signal for 3 is observed at even higher frequency (\u03b4 = \u2013285 ppm). Compounds 3 and 4 feature strong IR absorption bands at almost identical wavenumbers corresponding to the C\u2013O stretching vibrational mode of the OCP\u2013 ligand. This feature appears at lower energy than that found in Re scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO)(CO)2(triphos) (1860 cm\u20131) and alkali OCP\u2013 salts (1730 to 1780 cm\u20131), which indicates weakening of the C\u2013O bond order. As evidenced both by the low wavenumber IR absorption of \u03bdC\u2013O and the downfield 31P NMR chemical shift, the OCP\u2013 moiety in 3 and 4 is best described as a phosphaalkyne-type limiting resonance structure scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO)(CO)2(triphos) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP bond upon coordination to the oxophilic actinide centers.Salt-metathesis reactions between the ectively . Both coture see in contr\u2013 fragment is confirmed by X-ray crystallography scale\" fill=\"currentColor\" stroke=\"none\">P motif pointing to two different directions in a 45\u2009:\u200955 ratio. The discussion of metrical parameters for 4 is, therefore, performed on the non-disordered molecule only. The thorium and uranium analogs adopt C3-symmetry, with the three bidentate amidinate ligands wrapping around the actinide in a propeller-like geometry, and the OCP\u2013 ligand pointing in the axial position. The O\u2013C\u2013P (179.1(4)\u00b0 in 3; 179.7(4)\u00b0 in 4) and An\u2013O\u2013C (170.9(3)\u00b0 in 3; 176.4(3)\u00b0 in 4) angles are close to linearity. The C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP (1.576(5) \u00c5 in 3; 1.561(4) \u00c5 in 4) and C\u2013O (1.219(6) \u00c5 in 3; 1.246(4) \u00c5 in 4) bond lengths are in the expected range scale\" fill=\"currentColor\" stroke=\"none\">P = 1.579(3) \u00c5; C\u2013O 1.212(4) \u00c5 in [K([18]crown-6)][PCO]), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP triple bond and a weakening of the C\u2013O bond when compared with the metrical parameters computed for the OCP\u2013 anion scale\" fill=\"currentColor\" stroke=\"none\">P = 1.625 \u00c5; C\u2013O 1.203 \u00c5).iv).amid and Th\u2013Namid bond distances average respectively 2.44(3) \u00c5 and 2.49(3) \u00c5 and compare well with related compounds.The O-coordination of the OCPlography -top. Com5\u20138 symmetric species in solution. The IR C\u2013N stretches for compounds 5\u20138 are of high intensities and fall in the range of previously reported N-bound cyanate5\u20138, (uranium derivatives shown in OCN (2.340(3) \u00c5 in 5, 2.410(2) \u00c5 in 6) and An\u2013NSCN (2.385(4) \u00c5 in 7, 2.428 (4) \u00c5 in 8) bond distances compare well with those reported for structurally characterized An(iv) cyanate and thiocyanate complexes.iv) and Th(iv). The most striking difference is the preferred O-coordination for OCP\u2013vs. N-coordination in the case of OCN\u2013 and SCN\u2013.The cyanate and thiocyanate counterparts 5\u20138 were pre\u2013 binds actinides through the N-terminus, at first glance, one could have expected OCP\u2013 to behave similarly and bind through the pnictide donor, as is the case in Re(XCO)(CO)2(triphos) .\u2013 anion (q(O) = \u20130.65; q(P) = \u20130.44) and in the OCN\u2013 anion (q(O) = \u20130.75; q(N) = \u20130.81);Two major limiting resonance structures have to 4 is 7.7 kcal mol\u20131 lower in energy than in the hypothetical P-bound analogue (\u20131 lower for the O-bound complex 4 (1666 cm\u20131) than for the P-bound (1901 cm\u20131). In the case of the NCO ligand, the computed CO stretching frequency of Th\u2013NCO (2230 cm\u20131) is 15 cm\u20131 lower than in Th\u2013OCN (2245 cm\u20131). In the same way, for SCN, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN stretch is computed to be lower by 132 cm\u20131 for Th\u2013NCS (2016 cm\u20131) over Th\u2013SCN (2148 cm\u20131). These two sets of calculations fit with the experiment.DFT calculations are in line with the experimental observations and show that the N-bound mode is preferred with cyanate and thiocyanate anions, while the O-bound one is favored for the phosphaethynolate anion. This observation contrasts with the few previous studies which reported that the P-bound products are thermodynamically preferred;analogue . IR calc4 indicates that the O-bound complex is preferred over the P-bound analog because of the donation from the lone pairs of the oxygen atom to the empty hybrid d/f orbital of the metal (Wiberg index of 0.42). It is worthy to note that there is no interaction between the C\u2013P and the C\u2013O bonds; the molecular orbitals within the OCP\u2013 unit are localized onto either one or another. Contrarily, when OCP\u2013 is coordinated through the lone pair of the phosphorus, a more covalent interaction is observed (Wiberg index of 0.90). Moreover, there is also a strong interaction between the lone pairs of the oxygen and the Th\u2013P bond, giving rise to the formation of an allylic-type interaction between the three centers . As thorium prefers to be rather ionic, the O-bound configuration is the most energetically prominent isomer.NBO analysis of \u2013 anions , the N-bound derivatives are respectively 13.4 kcal mol\u20131 and 17.5 kcal mol\u20131 lower in energy than the O- and S-bound ones for Th . The computed \u0394E are surprisingly greater for OCN\u2013 than for OCP\u2013 given that the terminus charge density difference is more pronounced in OCP\u2013 compared to OCN\u2013 and the hard/soft mismatch is stronger for An\u2013P bonding. This suggests that the P- vs. O-coordination selectivity is subtle in phosphaethynolate metal derivatives, with OCP\u2013 behaving as an ambident Lewis base depending on the nature of the metal.For the XCN4. Formation of SCP\u2013 has been observed upon reaction of alkali salts of the OCP\u2013 anion with CS2; compound 4, however, is stable with respect to [2 + 2] cycloaddition with CS2. Since the P-atom in 4 is protruding above the TMS groups, we reasoned that it could be accessible and act as a soft-donor to bind late transition metals. Accordingly, treatment of 4 with one equivalent of Ni(COD)2 results in a strong darkening of the solution and leads to the heterobimetallic adduct (amid)3Th(\u03bc-\u03b71(O):\u03b72-OCP)Ni(COD) 9 (9 is the sole product resulting from the reaction of 4 with Ni(COD)2, NMR studies performed in benzene solution show that these species are in equilibrium. Unfortunately, these compounds exhibit similar solubility in common solvents, therefore preventing the quantitative isolation of 9 in pure form. The 31P NMR spectrum of 9 shows a drastic downfield shift of the signal (\u03b4(31P) = \u20137.7 ppm) compared to 4 which is indicative of strong rearrangement of the phosphaethynolate moiety. Strong deshielding of the phosphorus atom is typically observed in related \u03b72-phosphaalkene derivatives.9 is confirmed by 1H NMR which features two vinylic resonances at \u03b4 = 6.1 and 5.5 ppm.We have carried out preliminary reactivity investigations involving i(COD) 9 . While 99 established unequivocally the formation of a three-membered nickel phosphametallacycle (C1\u2013P1\u2013Ni1 = 57.4(2)\u00b0) resulting from the addition of the Ni(0) center across the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP bond. The most striking feature of this structure (depicted in \u2013 moiety (P\u2013C\u2013O angle = 148.1(3)\u00b0; Th\u2013O\u2013C angle = 157.5(3)\u00b0) bridging the two metals in an unprecedented \u03bc-\u03b71(O):\u03b72 fashion. This is indicative of strong backbonding from the square-planar nickel center into the \u03c0* orbital of the ligated C\u2013P unit. While these structural features are reminiscent of Ni(0) activation of phosphaalkynes\u2013 moiety in 9 is unique. Electron-donation to the antibonding \u03c0* orbital results in significant elongation of the coordinated C\u2013P bond length (1.660(4) \u00c5) from the corresponding value of 1.561(4) \u00c5 found in 4 and falls in the range (1.630 to 1.694 \u00c5) of side-on coordinated phosphaalkynes to nickel2NMe)(\u03b72-(Ph3C)C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP)]4, while the Th\u2013O distance (2.279(3) \u00c5) is shortened which further indicates higher electron density on the OCP\u2013 moiety.Single-crystal X-ray diffraction analysis of 9 by DFT scale\" fill=\"currentColor\" stroke=\"none\">P orbital overlaps with a d-orbital of the nickel to give the HOMO seen in Examination of the structure of n as a salt-metathesis reagent for accessing phosphaethynolate actinide complexes. Unlike the P-bound product favored with rhenium, O-bonding is preferred with actinides while cyanate and thiocyanate anions adopt N-bonding. Actinide coordination polarizes the OCP\u2013 moiety and enhances its phosphaalkyne character. Addition of Ni(0) across the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tP bond of the Th-bound phosphaethynolate results in the formation of an unprecedented reduced OCP\u2013 moiety of bent-geometry bridging the two metals. These preliminary results pave the way towards the development of metal phosphaethynolate complexes both for reactivity purposes and to generate original heteropolymetallic architectures. Studies aiming at expanding actinide phosphaethynolate chemistry and uncovering the full range of reactivity of the metal-bound OCP\u2013 moiety are ongoing in our group.In summary, this study has proven the utility of Na(OCP)(dioxane)Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Sodium phosphaethynolate reacts with [MCl(PDI)] to give metallaphosphaketenes, which in the case of iridium rearranges into a dimetalladiphosphene. via CO migration from phosphorus to the metal. Two different bonding modes of the PCO anion to CAAC-coinage metal complexes [CAAC: cyclic (amino)(carbene)] are reported, one featuring a strong Au\u2013P bond and the other an \u03b72 coordination to copper. The gold complex appears to be mostly unreactive whereas the copper complex readily reacts with various organic substrates. A completely free PCO anion was structurally characterized as the [Cu(La)2]+ (OCP)\u2013 salt. It results from the simple displacement of the PCO unit of the cationic (CAAC)Cu(PCO) complex by a second equivalent of CAAC.Sodium phosphaethynolate reacts with [MCl(PDI)] to give metallaphosphaketenes, which in the case of iridium rearranges into a dimetalladiphosphene, NoteworD to E, and the displacement of the PCO unit of the copper complex by a CAAC, which leads to a PCO anion with no coordinating solvents or binding agents.Herein we describe salt metathesis reactions leading to both unstable and stable terminal PCO transition metal complexes, featuring different coordination modes, and reactivity. We also report the experimental demonstration of the predicted conversion of Because of the strongly reducing character of Na(OCP),14iPr)] complex 1 was reacted with Na(OCP) in THF at \u201330 \u00b0C the color changed from pink to deep purple, and a single broad resonance in the 31P NMR spectrum at \u03b4 = \u2013226 ppm [vs. \u03b4 = \u2013392 ppm for Na(OCP)] indicated quantitative conversion. The metallaphosphaketene 3 was isolated in 61% yield and fully characterized. The IR spectrum showed the asymmetric stretching frequency of the phosphaketene unit at \u03bdasym = 1851 cm\u20131, intermediate between Na(OCP) (\u03bdasym = 1755 cm\u20131) and Ph3Sn\u2013P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (\u03bdasym = 1946 cm\u20131) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO. This is confirmed by a single crystal X-ray diffraction analysis ] 2 with the less sterically encumbered PDIMe ligand reacts with Na(OCP) at low temperatures to cleanly give product 4. A 31P NMR resonance at \u03b4 = \u2013316.7 ppm indicates a metallaphosphaketene scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) featuring a highly covalent metal phosphorus bond. Complex 4 could not be isolated. Keeping a THF solution at 20 \u00b0C for about 6 h leads cleanly to complex 5 , which was isolated as red crystals. A single crystal X-ray structure analysis shows compound 5 to be a dimetalladiphosphene scale\" fill=\"currentColor\" stroke=\"none\">P\u2013R. The iridium centers are bound to a redox-inactive PDI ligand with short C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds and a carbonyl ligand. The rearrangement of 4 into 5 is the experimental confirmation of the computationally predicted transformation of D to E.3, to a transient terminal nitrido complex, Ir PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN, which could be spectroscopically characterized but also dimerizes to an Ir\u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN\u2013Ir complex.16The corresponding iridium complex and C\u2013O bond lengths are similar, and the M\u2013P\u2013C angle is slightly more acute for the copper complex 9 .Monitoring by studies . Only ve8a and 9. The NBO charges of Au and PCO in 8a are +0.39 and \u20130.56 a.u., respectively, whereas those of Cu and PCO in 9 are +0.58 and \u20130.68 a.u., suggesting that the PCO anion in 9 is more ionic and \u201cfree\u201d than that in 8a. This is in agreement with the different 31P NMR chemical shifts of 8a (\u03b4 = \u2013360 ppm) and 9 (\u03b4 = \u2013387 ppm). The NBOs corresponding to the M(PCO) (M = Au or Cu) fragments are quite different as shown in 8a forms three bonds analysis at the M06/6-311++G+SDD//M06/6-31+G(d)+LANL2DZ(+f) level of theory shows significant differences between the electronic structures of d P\u2013C \u03c0) . In cont \u03c0 bonds . Moreoveonds 3P], as determined by an X-ray diffraction study, is reminiscent of the rearrangement product of Ph3Sn(PCO), namely (Ph3Sn)3P.31P NMR spectrum displays a signal at \u03b4 = \u2013200 ppm, which is considerably high-field shifted compared to alkyl and aryl phosphines. The electron rich nature as well as the steric crowding around the P center could make 10 an interesting redox active ligand for transition metals.18The different bonding modes in perature . The tri8a,b are rather inert and do not react with heavier group 14 element halides to give R3E-PCO derivatives. Equally, no reaction with N,N\u2032-dicyclohexylcarbodiimide or with carbene La are observed. On the contrary, the copper salt 9 does react with these reagents similarly to Na(OCP) (see the ESI9 reacts with carbene La to afford the cationic bis(CAAC)Cu complex 11, in which the PCO fragment is the anionic counterpart. The 31P NMR signal appears at \u03b4 = \u2013400 ppm, which is more downfield shifted than Na(OCP) (\u03b4 = \u2013392 ppm), implying that PCO\u2013 is less coordinated. The IR spectrum showed the asymmetric stretching frequency of the PCO unit at \u03bdasym = 1791 cm\u20131, suggesting a more cumulenic nature than in the two crystalline forms of Na(OCP) (\u03bdasym = 1780 or 1755 cm\u20131).The gold complexes 8a and 9 are mainly localized on the PCO fragments (see ESI8a and \u20130.59 a.u. in 9). Thus, we were curious to see if the terminal oxygen atom could react with a Lewis acidic borane. Indeed, adding one equivalent of B(C6F5)3 to either 8b or 9 led to the same type of heterocycle 12 and 13, respectively CoCl 1,MePDI)IrCl 2,a,bAuCl 6a,baCuOtBu 71H, 13C, 11B, 19F, and 31P NMR spectra were recorded on a Varian VX 500, Bruker 300, Bruker 500 and Jeol 500 spectrometer at 25 \u00b0C. All 1H and 13C NMR chemical shifts are reported relative to SiMe4 using the 1H and 13C chemical shifts of the solvent as a secondary standard. NMR multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, sept = septet, m = multiplet, br = broad signal. Chemical shifts are given in ppm and coupling constants J are given in Hz. Peak widths at half heights (in Hz) are given for broad signals. Infrared spectra were collected on a Perkin-Elmer-Spectrum 2000 FT-IR-Raman and Bruker ALPHA FT-IR spectrometer. Elemental analyses were performed at the Mikrolabor of ETH Z\u00fcrich. Single crystals suitable for X-ray diffraction were coated with polyisobutylene oil in a dry-box, transferred to a nylon loop and then transferred to the goniometer of a Bruker X8 APEX2 diffractometer equipped with a molybdenum X-ray tube (\u03bb = 0.71073 \u00c5) or on a Bruker Apex II-CCD detector using Mo-K\u03b1 radiation (\u03bb = 0.71073 \u00c5) or Cu-K\u03b1 radiation (\u03bb = 1.54178 \u00c5). The data were processed using the Bruker SAINT+ program and corrected for absorption using SADABS. The structures were solved using direct methods (SHELXS) completed by Fourier synthesis and refined by full-matrix least-squares procedures. Mass spectra were performed at the UC San Diego Mass Spectrometry Laboratory. Melting points were measured with an electrothermal MEL-TEMP apparatus.All air- and moisture-sensitive manipulations were carried out using standard vacuum line Schlenk techniques or an MBraun dry-box under argon. THF was distilled over sodium benzophenone-ketyl before use. THF-iPrPDI)CoCl 1 and 10 mL of THF. The solution was cooled to \u201335 \u00b0C and Na(OCP) was added portion-wise over the course of 5 minutes, eliciting a color change from pink to dark purple. The reaction was placed in the freezer at \u201335 \u00b0C for one hour then filtered through Celite. The solution was concentrated, layered with hexane and placed at \u201335 \u00b0C. This gave 0.152 g (48%) of a purple crystalline solid identified as [(iPrPDI)Co(PCO)] 3. The mother liquor was placed back in the freezer to obtain another 42 mg (13%) of product. X-Ray quality crystals were grown from the second fraction. Analysis for C34H43CoN3OP, 599.64 g mol\u20131, calc.: C, 68.10; H, 7.23; N, 7.01 found: C, 66.05; H, 7.35; N, 6.85. IR (powder): \u03bd PCO = 1851 cm\u20131. 1H NMR : \u03b4 = 9.66 , 7.47 , 7.35 , 7.05 , 3.32 ), 1.13 ), \u20130.19 ; 13C NMR : \u03b4 = 181.2 , 168.1, 153.4, 150.5, 140.0, 125.1, 124.0, 116.4, 28.6 (Ar-CH3), 24.0 (Ar-CH3), 23.3, 21.8; 31P NMR : \u03b4 = \u2013225.8 ppm (lb = 634 Hz).In the glove box, a 20 mL scintillation vial was charged with 0.200 g (0.347 mmol) of (2 and 5 mL of THF and cooled in a dry-ice/acetone bath. A solution of Na(OCP) in THF (3 mL) was syringed into the stirring iridium solution, immediately causing a color change to dark purple. The reaction was warmed to room temperature, whereupon the color changed to deep pink, and stirred for an additional hour. The reaction was then filtered through Celite and then concentrated to roughly 3 mL. Storing at \u201335 \u00b0C overnight produced a solid that was collected on a glass frit and dried under reduced pressure, yielding 0.076 g (74% yield) of red crystalline solid 5. X-Ray quality crystals were grown from the slow evaporation of the mother liquor at room temperature overnight. NMR analysis was performed in CD2Cl2 due to the poor solubility of 5 in ethereal or aromatic solvents, but the compound slowly decomposed (if left overnight) in methylene chloride. Analysis for C52H55Ir2N6O2P2, calcd: C 50.27, H 4.46, N 6.76; found: C 49.96, H 4.63, N 6.31. IR (powder): \u03bd CO = 1967 cm\u20131. 1H NMR : \u03b4 = 8.12 , 7.26 , 7.07\u20136.93 , 2.3 , 1.63 , 1.43 ; 13C NMR : \u03b4 = 187.50 (CO), 152.66, 149.21, 143.12, 131.89, 130.36, 128.28 (Ar-CH), 127.96 (Ar-CH), 126.02, (Ar-CH), 123.97 (m-Py-CH), 116.16 (m-Py-CH), 20.66 (Ar-CH3), 18.31 (Ar-CH3), 15.51 (CN\u2013CH3); 31P NMR : \u03b4 = 683.2.A 20 mL Schlenk flask was charged with 0.100 g (0.167 mmol) of (MePDI)IrCl 6a and [Na(PCO)(dioxane)2.5] was cooled to \u201378 \u00b0C before THF (10 mL) was added. The mixture was stirred for 15 minutes and then warmed to room temperature. After 30 min, the solvent was removed under vacuum and the resulting brown solid was extracted with 15 mL of benzene. After removing the solvent, 8a was obtained as a light yellow solid . Colorless single crystals of 8a were obtained by vapor diffusion of pentane into a saturated benzene solution of 8a in the dark. IR (C6H6): \u03bd PCO = 1887 cm\u20131. M.P. = 193 \u00b0C (dec.). 1H NMR : \u03b4 = 7.13 , 7.00 , 2.72 , 1.63 , 1.54 , 1.42 , 1.08 , 0.85 ; 13C {1H} NMR : \u03b4 = 253.5 , 183.0 scale\" fill=\"currentColor\" stroke=\"none\">O d, JPC = 100.4 Hz), 146.1, 135.3, 130.9, 126.0, 81.0, 63.0, 43.0, 32.4, 20.1, 29.5, 27.7, 23.7, 10.3; 31P {1H} NMR \u03b4 = \u2013359.5. HRMS was attempted but a peak corresponding to M+ could not be located, probably due to the weak P metal bond.A mixture of (CAAC)AuCl 6b and [Na(PCO) (dioxane)2.5] was cooled to \u201378 \u00b0C before THF (10 mL) was added. The mixture was stirred for 15 minutes and then warmed to room temperature. After 30 min, the solvent was removed under vacuum and the resulting brown solid was extracted with 15 mL of benzene. After removing the solvent, 8b was obtained as a light yellow solid . Colorless single crystals of 8b were obtained by vapor diffusion of (TMS)2O into a saturated benzene solution of 8b in the dark. IR (C6H6): \u03bd PCO = 1889 cm\u20131. M.P. = 221 \u00b0C (dec.). 1H NMR : \u03b4 = 7.14 , 7.00 , 3.17 , 2.79 , 2.05 , 1.95 , 1.88 , 1.82 , 1.69 , 1.58 , 1.52 , 1.26 , 1.09 , 0.93 , 0.87 ; 13C {1H} NMR : \u03b4 = 253.5 , 182.5 scale\" fill=\"currentColor\" stroke=\"none\">O d, JPC = 101.1 Hz), 146.2, 145.8, 136.1, 130.6, 129.2, 125.8, 77.6, 65.4, 53.4, 52.0, 50.0, 36.4, 31.3, 30.1, 29.8, 28.8, 28.0, 27.3, 25.6, 23.8, 23.7, 23.6, 20.7; 31P {1H} NMR \u03b4 = \u2013364.2. HRMS was attempted but a peak corresponding to M+ could not be located, probably due to the weak P metal bond.A mixture of (CAAC)AuCl 7 and [Na(OCP) (dioxane)2.5] was stirred for 10 minutes in 3 mL of benzene at room temperature. The solvent was removed under vacuum and the resulting brown solid was washed with 10 mL of pentane. After drying under vacuum, 9 was obtained as a light yellow solid . Colorless single crystals of 9 were obtained were obtained by vapor diffusion of (TMS)2O into a saturated toluene solution of 9 at \u201340 \u00b0C. IR (C6H6): \u03bd PCO = 1849 cm\u20131. M.P. = 173 \u00b0C (dec.). 1H NMR : \u03b4 = 7.12 , 7.00 , 2.75 , 1.68 , 1.43 , 1.38 , 1.08 , 0.93 , 0.85 ; 13C {1H} NMR : \u03b4 = 251.8 (Ccarbene), 175.2 scale\" fill=\"currentColor\" stroke=\"none\">O d, JPC = 97.8 Hz), 145.9, 135.5, 130.7, 125.6, 81.2, 63.1, 43.1, 31.9, 29.9, 29.4, 27.9, 23.1, 10.4; 31P {1H} NMR \u03b4 = \u2013387.4. HRMS was attempted but a peak corresponding to M+ could not be located, probably due to the weak P metal bond.A mixture of (CAAC)CuOtBu 8b was left standing in 2 mL of THF for 1 week under visible light. White crystals of 10 were generated and washed with 5 mL of pentane . M. P. = 293 \u00b0C (dec.). 1H NMR : \u03b4 = 7.39 , 7.18 , 2.72 , 2.28 , 1.88 , 1.78 , 1.67 , 1.34 , 1.24 , 1.13 , 0.98 , 0.90 , 0.82 ; 13C {1H} NMR : \u03b4 = 260.3 , 146.3, 145.7, 135.3130.2, 125.5, 125.2, 79.0, 78.9, 66.5, 66.4, 52.9, 50.5, 36.5, 30.5, 30.4, 30.0, 29.9, 29.5, 29.0, 28.9, 28.5, 25.2, 25.1, 24.5, 23.3, 23.2, 21.3; 31P {1H} NMR \u03b4 = \u2013200.2. HRMS: m/z calculated for [C81H130N3Au3P]+ (M + H)+ 1766.8999; found 1766.8980.Complex 9 and carbene La was stirred for 2 min in benzene (0.5 mL). The suspension was filtered and the colorless powder was washed with benzene (1 mL), yielding 11 . Single crystals were obtained by slow evaporation of a saturated benzene solution of 11. IR : PCO \u03bd = 1791 cm\u20131. M.P. = 158 \u00b0C (dec.). 1H NMR : \u03b4 = 7.08 , 6.97 , 2.70 , 1.54 , 1.42 , 1.32 , 1.05 , 0.84 , 0.81 ; 13C {1H} NMR : \u03b4 = 253.3 (Ccarbene), 145.8, 135.3, 130.7, 125.5, 80.8, 63.0, 43.6, 31.6, 30.0, 29.4, 28.0, 23.1, 10.2; 31P {1H} NMR \u03b4 = \u2013399.5. HRMS: m/z calculated for [C44H70CuN2]+ 689.4835; found 689.4847.A mixture of 8b and B(C6F5)3 was stirred in 2 mL of benzene for 5 minutes. The resulting yellow suspension was filtered and the yellow residue was washed with benzene (0.5 mL), then dried under vacuum, yielding 61 mg (64%) of a bright-yellow powder. Yellow single crystals of 12 were obtained in the filtrate in less than 1 min. M.P. = 230 \u00b0C (dec.).A mixture of 9 and B(C6F5)3 was stirred in 1 mL of toluene for 5 minutes. The solvent was removed under reduced pressure and the residue was washed with pentane (2 mL), yielding 68 mg (62%) of a light-yellow powder. Colorless single crystals were obtained by vapor diffusion of (TMS)2O into a saturated toluene solution of 13. M.P. = 160 \u00b0C (dec.). 1H NMR : \u03b4 = 7.08 , 6.93 , 2.59 , 1.40 , 1.31 , 1.12 , 1.08 , 1.01 , 0.85 ; 13C {1H} NMR : \u03b4 = 248.8 (Ccarbene br), 149.5 , 149.0 , 145.5, 138.1 , 135.1, 131.2, 125.8, 82.5, 62.8, 43.0, 31.5, 29.7, 29.2, 27.7, 22.7, 9.9; 31P {1H} NMR \u03b4 = 260.6 (br), 136.2 (br). HRMS was attempted but a peak corresponding to M+ could not be located, probably due to the weak P metal bond.A mixture of Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Evidence for a transient, highly reactive ThNTh nitride is presented, in contrast to uranium analogues that are stable and isolable. Surprisingly, computational studies reveal a \u03c3 > \u03c0 energy ordering for all these bridging nitride bonds, a phenomenon for actinides only observed before in terminal uranium nitrides and uranyl. DMBS)(I)] 3}3\u2013) with NaN3 or KN3, respectively, affords very rare examples of actinide molecular square and triangle complexes [{M(TrenDMBS)(\u03bc-N3)}n] . Chemical reduction of 3 produces [{U(TrenDMBS)}2(\u03bc-N)][K(THF)6] (5) and [{U(TrenDMBS)}2(\u03bc-N)] (6), whereas photolysis produces exclusively 6. Complexes 5 and 6 can be reversibly inter-converted by oxidation and reduction, respectively, showing that these UNU cores are robust with no evidence for any C\u2013H bond activations being observed. In contrast, reductions of 4 in arene or ethereal solvents gives [{Th(TrenDMBS)}2(\u03bc-NH)] (7) or [{Th(TrenDMBS)}{Th(N[CH2CH2NSiMe2But]2CH2CH2NSi[\u03bc-CH2]MeBut)}(\u03bc-NH)][K(DME)4] (8), respectively, providing evidence unprecedented outside of matrix isolation for a transient dithorium-nitride. This suggests that thorium-nitrides are intrinsically much more reactive than uranium-nitrides, since they consistently activate C\u2013H bonds to form rare examples of Th\u2013N(H)\u2013Th linkages with alkyl by-products. The conversion here of a bridging thorium(iv)-nitride to imido-alkyl combination by 1,2-addition parallels the reactivity of transient terminal uranium(iv)-nitrides, but contrasts to terminal uranium(vi)-nitrides that produce alkyl-amides by 1,1-insertion, suggesting a systematic general pattern of C\u2013H activation chemistry for metal(iv)- vs. metal(vi)-nitrides. Surprisingly, computational studies reveal a \u03c3 > \u03c0 energy ordering for all these bridging nitride bonds, a phenomenon for actinides only observed before in terminal uranium nitrides and uranyl with very short U\u2013N or U\u2013O distances.Molecular uranium-nitrides are now well known, but there are no isolable molecular thorium-nitrides outside of cryogenic matrix isolation experiments. We report that treatment of [M(Tren PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPH, and bridging ThP(H)Th, ThAs(H)Th, ThAs(H)K, ThPTh and ThAsTh units.2 linkages are highly unstable and readily decompose. In contrast, most bridging UNU units seem to be relatively stable,Building on our prior work on terminal uranium-nitrides,Here, we report the synthesis and characterisation of two triamidoamine uranium- and thorium-azides. Despite marginal differences in the covalent radii of these metals, the uranium complex is a rare example of an actinide molecular square whereas the thorium analogue is a molecular triangle. Reduction of the uranium-azide complex generates diuranium-nitrides, with two charge states of a UNU core being accessible, and interchangeable, with no evidence of C\u2013H activation chemistry even under photolytic conditions. However, a ThNTh complex could not be isolated. Instead, the isolation of two ThN(H)Th complexes, which is an unprecedented linkage in thorium chemistry and rare in f-block chemistry generally,3 reduction approach using the TrenDMBS {N(CH2CH2NSiMe2But)3}3\u2013 ligand as this was anticipated to be sterically open enough to allow any nitrides to bridge, whereas the bulkier TrenTIPS {N(CH2CH2NSiPri3)3}3\u2013 variant stabilises ThPTh and ThAsTh linkages but terminal UN for uranium. Accordingly, treatment of [M(TrenDMBS)(I)] 3 or KN3 affords [{M(TrenDMBS)(\u03bc-N3)}n] as green-yellow and colourless crystalline solids after work-up in isolated yields of 35 and 86%, respectively, 3 and 4, in particular the ATR-IR spectra of 3 and 4 both exhibit strong absorptions at 2131 cm\u20131, which is characteristic of actinide-bound bridging-azide ligands.3, \u03bcB per molecule decreasing smoothly to 0.78 \u03bcB at 2 K and tending to zero as expected for a tetrametallic UIV complex, since UIV usually has a magnetic singlet ground state at low temperature.In order to prepare MNM linkages we pursued a M\u2013N3 and 4 we determined their solid-state structures, 1 and 2, and chloride analogues, are monomers, 3 and 4 are tetrameric and trimeric in the solid-state. Such molecular squares and trianglesC3v symmetry of TrenDMBS is lowered to Cs the cleft that opens up allows two azides to enter the coordination sphere of uranium in 3 at an approximate right angle (\u223c85\u00b0) whereas for the larger thorium in 4 the azides approach at a slightly more acute N\u2013Th\u2013N angle (\u223c79\u00b0), which seems to be enough to switch from tetramer to trimer. It would seem that the N\u2013Th\u2013N angle can close at the larger metal without as much inter-azide clashing due to longer Th\u2013N bonds placing the azides further apart from one another, which accounts for the aggregation states of 3 and 4. The U\u2013 and Th\u2013Nazide distances in 3 and 4 are longer than in terminal azide complexes,trans to a TrenDMBS amide centre ; 4, 2.609(8) \u00c5 av.) than amine centre ; 4, 2.478(7) \u00c5 av.), possibly implying a trans-influence. All other bond lengths are within normal ranges and do not suggest any strong activation of the azides.In order to confirm the formulations of 3 and 4 in-hand we investigated their reduction chemistries. The reaction of 3 with KC8 always produces the diuranium(iv/iv)-nitride [{U(TrenDMBS)}2(\u03bc-N)][K(THF)6] (5) and the mixed-valence diuranium(iv/v)-nitride [{U(TrenDMBS)}2(\u03bc-N)] (6) in \u223c42% overall yield , with concomitant elimination of N2 and KN3.5\u2009:\u20096 varies from 77\u2009:\u200923 to 50\u2009:\u200950 as the KC8 ratio is varied from 5 to 3 equivalents but is independent of the solvent used . Other KC8 ratios gave intractable product mixtures. Complexes 5 and 6 can be separated by fractional crystallisation, however we find that 6 can be cleanly prepared in 45% isolated crystalline yield by photolysis of 3 with a 125 W Hg-lamp for 7 hours. Gratifyingly, 6, or a known mixture of 5 and 6, can be reduced with KC8 to give solely 5, and 5 or a known mixture of 5 and 6 can be oxidised with AgBPh4 to give exclusively 6, 5 and 6 are always formed in the respective reduction and oxidation reactions, irrespective of the amounts of KC8 (2\u20138 equiv.) and AgBPh4 (2\u20133 equiv.) used, and we found no evidence for further reductions or oxidations, respectively.With 5 and 6 are distinct, reflecting their UIV/UIV and UIV/UV formulations, respectively. The 1H NMR spectra of 5 and 6 span the ranges +96 to \u201334 and +25 to \u201313 ppm, respectively, reflecting their 5f2/2vs. 5f2/1 natures. The solution Evans method (298 K) gives magnetic moments of 4.0 and 3.5 \u03bcB per molecule of 5 and 6, whereas the solid-state magnetic moments, \u03bcB, respectively. These values decrease to 1.00 and 1.07 \u03bcB at 2 K, respectively. For 5 the respective values per uranium ion are 3.39 (298 k) and 0.74 \u03bcB (2 K), which per ion are slightly higher than the corresponding values for 3 reflecting their nitride and azide formulations.6 are consistent with its UIV/UV combination,V ion has a magnetic doublet ground state at all temperatures, and anti-ferromagnetic U\u2013U coupling is suggested by a maximum at \u223c60 K in the \u03c7 vs. T plot of 5.V in 6 is unequivocally confirmed by EPR spectroscopy (S- and X-bands) at 5 K, g-values with geff = 3.13, 0.95, 0.50, and 2.70, 0.74, 0.43; these data reflect the presence of two conformational isomers in the solid-state structure of 6 due to positional disorder of three of the six SiMe2But groups, and we note that the effective g-values of spin\u2013orbit doubles are extremely sensitive to small changes in structure.E1/2 \u20131.4 V (vs. [Fc(Cp)2]0/+1) for the [UIV/UV]/[UIV/UIV]\u2013 redox couple is found, 3 and 4 which do not exhibit any electrochemical events in the solvent-accessible window of 2.5 to \u20133.0 V. The chemical inter-conversion of 5 and 6 suggests the presence of robust UNU cores, as was found for [{U3}2(\u03bc-N)]n which can exist in three charge states, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tU angles of 5 compared to 6 (see below).As expected, the characterisation data for 5 and 6 were determined, 5 resides on a crystallographic 3-fold rotation axis and therefore the U\u2013N\u2013U and Nnitride\u2013U\u2013Namine angles are rigorously 180\u00b0, however in 6 the U\u2013N\u2013U angle is bent at 161.2(2)\u00b0. In 5 the U1/2\u2013N nitride, amide, and amine distances are 2.0648(2), 2.343(3), and 2.733(5) \u00c5, respectively; these distances reflect the bridging nature of the nitride, that is consistent with other UNU distances,IV complexes, and possibly a strong trans-influence from the nitride since the amine distances are quite long like in related ThPTh and ThAsTh complexes,vi)-nitride.6 the U\u2013Nnitride distances are now inequivalent at 2.081(5) and 2.136(5) \u00c5, and the U\u2013Namide and U\u2013Namine distances (av. 2.287(5) and 2.649(5) \u00c5) are now shorter than in 5, presumably reflecting the neutral formulation of 6 and a reduced nitride trans-influence since the Nnitride\u2013U\u2013Namine angles are now \u223c159\u00b0.The solid-state structures of 4, in contrast to 3, gives two distinct products, in addition to N2 and KN3, that are exclusive to the solvent media, DMBS)}2(\u03bc-N)][K] the parent imido [{Th(TrenDMBS)}2(\u03bc-NH)] (7) is isolated in 52% crystalline yield. When ethereal solvents are used the cyclometallated tuck-in-tuck-over,DMBS)}{Th(N[CH2CH2NSiMe2But]2CH2CH2NSi[\u03bc-CH2]MeBut)}(\u03bc-NH)][K(DME)4] (8) is isolated in 46% crystalline yield. The 1H NMR spectrum of 7 reveals a resonance at 5.55 ppm that corresponds to one N\u2013H proton; this resonance disappears when the reaction is conducted in D8-toluene, suggesting the source of H is aromatic solvent with K\u2013C6H5/\u2013CH2Ph as by-products. In-line with this, 7 does not react with benzyl potassium. The presence of the N\u2013H group is confirmed by a broad absorption at 3390 cm\u20131 in the ATR-IR spectrum of 7. The 1H NMR spectrum of 8 is now more complicated due to the desymmetrisation of one of the TrenDMBS ligands, but the N\u2013H proton resonance can be observed at 5.39 ppm.The reduction of 7 and 8 were determined, 7 the Th\u2013Nimido\u2013Th angle is 145.96(19)\u00b0 and the imido adopts a trigonal planar geometry in contrast to ThP(H)Th and ThAs(H)Th linkages2-NH dianion but p-orbital-dominated bonding of PH and AsH dianions. The Th\u2013Nimido distances of 2.331(4) and 2.312(4) \u00c5 are similar to the Th\u2013Namide distances (\u223c2.330 \u00c5) and \u223c0.3 \u00c5 longer than Th PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR terminal imido bonds.8 the Th\u2013Nimido\u2013Th angle is 120.9(7)\u00b0, reflecting the presence of the tuck-in-tuck-over cyclometallate enforcing a constrained C\u2013Th\u2013N\u2013Th four-membered ring. Despite this, the Th\u2013Nimido distances of 2.309(15) and 2.264(15) \u00c5 are essentially the same as those in 7. The Th\u2013C distances of 2.88(2) and 2.78(2) \u00c5 are long, as observed in other Th\u2013TrenDMBS cyclometallates.28The molecular structures of 5 and 6, especially the latter under photolytic conditions, is significant because photolysis of terminal uranium(vi)-nitridesiv)-nitride generated transiently by reduction5 and 6 contain quite robust, redox inter-convertible UNU cores, and when N2 is eliminated from 3 the nitride secures stabilisation by two uranium Lewis acid centres rather than instigating C\u2013H activation reactions.The formation and isolation of 4 does not lead to the isolation of dithorium-nitrides, the isolation of 7 and 8 is instructive. Like 5 and 6, reduction of an azide precursor, 4, results in the formation of a ThNTh unit, except in both cases this is protonated. For 7, the potassium from reduction has been exchanged for a proton suggesting that a transient nitride [{Th(TrenDMBS)}2(\u03bc-N)]\u2013 (\u20139) has C\u2013H activated arene solvents, and we note the yield of 7 does not vary when changing the solvent from benzene to toluene. Likewise, in the formation of 8 a \u03bc-NH unit forms again, but this time in the absence of deprotonatable arene solvent, and with the potassium cation sequestered by ethereal solvent, the transient nitride has C\u2013H activated the TrenDMBS to form a tuck-in-tuck-over cyclometallate3 species that also cyclometallate Tren-ligands due to proximity and entropy effects,5 and 6. Indeed, DFT calculationsDMBS)}2(\u03bc-N)]\u2013 (\u20135) and \u20139 suggest that the latter contains more polar and ionic metal-nitride linkages, but importantly the frontier molecular orbitals that principally comprise the ThNTh bonding interactions in \u20139 are destabilised by \u223c1.1 (\u03c3) and \u223c0.4 (\u03c0) eV compared to the corresponding UNU orbitals of \u20135. This results in a more basic, effectively superbasic, nucleophilic nitride in \u20139, as experimentally inferred by the isolation of 5versus7 and 8, and shown computationally where the anion of 8 is found to be 19.8 kcal mol\u20131 more stable than \u20139 and formed via a transition state with an experimentally accessible barrier of 16.4 kcal mol\u20131.18Although reduction of 8 parallels the reactivity of a transiently formed uranium(iv)-nitride that undergoes ligand C\u2013H activation to give a cyclometallated ligand and a uranium(iv) parent imido functionality by 1,2-addition,vi)-nitridesVIvs. MIV ions in this context generally, The formation of IVNUIV and ThIVNThIV -nitrides. Attempts to prepare a dithorium-nitride complex resulted in the isolation of two parent imido complexes, in-line with the paucity of isolable molecular thorium-nitrides to date. However, the two dithorium-imido products suggest for the first time that reduction of thorium-azides can generate nitrides, and provides evidence that a transient and highly reactive dithorium-nitride is formed, but that this linkage is highly basic and nucleophilic so is capable of activation C\u2013H bonds of arene solvent or the supporting TrenDMBS ligand. The contrasting stabilities of UNU and putative ThNTh units reported here may be related to the general tendency of uranium to engage in more covalent bonding than thorium, on a like-for-like basis. The results here suggest a general pattern of actinide-nitride reactivity where metal(iv)-nitrides, bridging or terminal, activate C\u2013H bonds to produce imido-alkyl combinations, whereas metal(vi)-nitrides produce alkyl-amide linkages, which can be related to the range of accessible oxidation states of these ions during reactions. Lastly, computational studies surprisingly reveal a \u03c3 > \u03c0 energy ordering for the bridging nitride linkages in this study, a phenomenon so far only found in terminal uranium-nitrides and uranyl complexes with very short U\u2013N/\u2013O distances.In conclusion, the synthesis of two uranium- and thorium-azide complexes has provided rare examples of actinide molecular square and triangle complexes. We have prepared two diuranium-nitride complexes in different charge states; these UNU complexes are quite robust, and do not engage in C\u2013H activation chemistry, even under photolytic conditions, unlike terminal uranium(There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Stepwise reaction of an indyl-anion with organic azides initially forms the indium imide, which undergoes (2 + 3)-cycloaddition to generate the indium tetrazenide. Ar)] (NONAr = [O(SiMe2NAr)2]2\u2013, Ar = 2,6-iPr2C6H3) and its reactivity with organic azides RN3 is reported. When R = 2,6-bis(diphenylmethyl)-4-tBu-phenyl, a dianionic alkyl-amide ligand is formed via C\u2013H activation across a transient In\u2013Nimide bond. Reducing the size of the R-group to 2,4,6-trimethylphenyl enables oxidation of the indium and elimination of dinitrogen to afford the imide species, K[In(NONAr)(NMes)]. The anion contains a short In\u2013Nimide bond, shown computationally to contain appreciable multiple bond character. Reaction of isolated imides with an additional equivalent of azide generates tetrazenido-indium compounds K, shown by X-ray crystallography to contain planar InN4 heterocycles in the anion.The synthesis of a new potassium\u2013indyl complex, K[In(NON These ligands are typically bulky, a requirement to limit (or prevent) aggregation and protect the metal from unwanted redox chemistry. This concept is best illustrated in the context of this work by the series M(BDIAr) ]\u2013, Ar = 2,6-iPr2C6H3), for which mono-metallic Al,The most common members of this class of compound are represented by the general formula M(X), where the charge on the metal is balanced by a mono-anionic ligand, [X]2]2\u2013 to support M(I) metal centres, generating an overall negative charge on the metal-containing species, [M(X2)]\u2013. Whilst this class of compound has been well studied for gallium,2)]\u2013 and [In(X2)]\u2013 systems indicate significant lone-pair character at the metal , with preliminary reactivity consistent with an Al(i) or In(i) nucleophile. We report in this contribution an investigation of the reducing potential of a new potassium indyl compound towards organic azides. This class of substrate was selected to target synthetically challenging indium imide species.A recent development in the chemistry of mono-valent aluminium and indium is to employ a dianionic ligand III\u2013VI was achieved through kinetic stabilization of the M\u2013Nimide bonds using sterically demanding ligands that prevent formation of ring- and cage-structures containing \u03bc2- and \u03bc3-NR ligands.imide functional group is highly reactive.15The isolation of 2 and oxidation of the metal M(III), which occurs with a concurrent increase in the coordination number of the metal. It is of note that, if insufficient steric protection is provided during synthesis, in situ addition of unreacted azide in the reaction mixture to the transient \u2018M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR\u2019 bonds can occur ,A general synthetic methodology to group 13 imides is the reduction of organic azides by a monovalent M(I) metal complexes .13b\u2013d,16an occur .17 For Aiii) imide, shown crystallographically and computationally to contain In\u2013Nimide multiple bonds. Reaction of isolated examples with additional azide proceeds via a (2 + 3)-cycloaddition pathway to generate tetrazenido-indium salts, containing the first structurally characterized examples of the InN4-heterocycle.In this contribution we report a new potassium indyl salt and its controlled (stepwise) reactivity with organic azides. The initial products are characterised as a new class of anionic indium(Ar-ligand (NONAr = [O(SiMe2NAr)2]2\u2013; Ar = 2,6-iPr2C6H3) stabilizes anionic indyl species as the indyllithium complex In(NONAr)(Li{THF}3), or in the ion-separated salt [K(crypt-222)][In(NONAr)] (crypt-222 = [2.2.2]-cryptand).The NON2[(NONAr)(THF)n] (1), is readily obtained from the reaction of KH with the ligand pre-cursor (NONAr)H2.n = 1), and the reagent can be used without further purification. However, crystallization from THF affords the Tris\u2013THF adduct (n = 3) which forms a dimer [1_{THF}3]2 in the solid-state (Et2O)2] which forms a polymer in the solid-state adduct that crystallizes as the dimer [K2{(NONAr)(18-c-6)}]2 Cl\u2019, elemental analysis was inconsistent with this formula and the compounds was therefore analysed by single-crystal X-ray diffraction (The reaction of fraction .2 contains the four-coordinate indium anion [In(NONAr)Cl2]\u2013 Cl2]\u2013 . The chaolecules .2 with two equivalents of potassium yields the new indyl compound K[In(NONAr)] (3) as a hexane soluble, yellow solid. The 1H NMR spectrum of 3 displays a single resonance for the SiMe2 substituents, indicative of a symmetrical environment for the NONAr-ligand. There are no resonances attributable to In\u2013H hydride ligands ]\u2013 anions linked by potassium cations that are involved in \u03c0\u2013aryl interactions to flanking Ar groups (C\u00b7\u00b7\u00b7K distances 3.109(4)\u20133.346(3) \u00c5). The In\u00b7\u00b7\u00b7In separation is 4.710(3) \u00c5, with In\u2013N bond lengths (2.182(3)\u20132.240(3) \u00c5) consistent with anionic In(i) metal centres.The molecular structure of 3 is remin3 was made using an equimolar amount of the sterically demanding 2,6-bis(diphenylmethyl)-4-tBu-phenyl azide and a reduction in the intensity of the CHPh2 resonance . A new peak at 3.24 ppm {C6H2(CPh2)(CHPh2)-tBu-2,6,4} ligand chelating to a four-coordinate, anionic indium(iii) centre scale\" fill=\"currentColor\" stroke=\"none\">NAr\u2021\u2019 bond of a transient indium imide.The structure of ) centre . The pot1.000000,.000000 s3) under the conditions described above (5). The 1H NMR spectrum is consistent with a symmetrical NON-backbone and a freely rotating Mes group .To mitigate complications from ligand activation, the reaction was repeated with the sterically less intrusive 2,4,6-trimethylphenyl azide \u20133.296(3) \u00c5). The indium centres are distorted trigonal planar (\u03a3angles 358.7\u00b0), with In\u2013Nimide bond lengths of 1.986(2) and 1.999(2) \u00c5 to N3 and N6, respectively. These represent an average shortening of 3.6% compared with the In\u2013N bonds in the three coordinate amide In(NHMes*)3 ,VIb (1.928(3) \u00c5)The solid-state structure of complex . The comimide bonds in 5 may be influenced by interactions with the potassium cations (N3\u2013K1 2.661(3) \u00c5, N6\u2013K2 2.646(3) \u00c5), which are located closer to the nitrogen atom than in other potassiated imides (range 2.732(3)\u20133.069(11) \u00c5).5 was crystallized in the presence of [2.2.2]-cryptand. The crystal structure of the product confirmed formation of the separated ion-pair [K(crypt-222)][In(NONAr)(NMes)] \u00c5) remains unchanged (within 3\u03c3) and the In\u2013N\u2013C angle is still bent (In\u2013N3\u2013C29 127.43(14)\u00b0), suggesting that the N\u00b7\u00b7\u00b7K interactions in 5 have little effect on the structural component of the indium\u2013nitrogen bond.The length of the In\u2013NMes)] 6, . Interesimide unit in 5 and the isolated anion [In(NONAr)(NMes)]\u2013 from compound 6 ([6]\u2013) that are substantially higher than the In\u2013N bonds to the NONAr-ligand .Optimisation and subsequent analysis using density functional theory confirmed the multiple-bond character of the In\u2013N) see ESI. This isVIb,A\u2013D, C did not yield a viable solution by this method. However, structures A (triple bond), B (double bond) and D (single bond) all have a low n-L contribution to their overall NBO solution (Table S2A and B (n-L = 1.965% and 1.990% respectively), while D was only slightly less well localised (n-L = 2.094%). Although it is difficult to extract a precise numerical value for the multiplicity of the In\u2013Nimide bond from these computational data, the results confirm a strong multiple-bond component in accordance with crystallographic results, and observed reactivity (vide infra).To explore the nature of this bond in more detail, plausible resonance structures analogous to those examined for Table S2. The bes5 and [6]\u2013 has been performed. The bond critical point between the In and Nimide bonds have a low ellipiticity (\u03b5) of 0.079 and 0.072 for 5 and [6]\u2013, respectively, inconsistent with a conventional In PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN double where a larger value (>0.25) is predicted. These data suggest a non-elliptical cross-section of electron density in the In\u2013N bond vector. This is consistent with a model proposed by Power and co-workers in related gallium imides related to VIa,i) species interacts with a singlet nitrene, with incomplete donation of electron pairs (represented by dashed lines in Quantum Theory of Atoms In Molecules (QTAIM) analysis of IV\u2013VI, we wished to determine whether the In\u2013Nimide bond in 5 was available for controlled reactivity studies. Inspired by the proposed formation of metallotetrazenes from group 13 metal imides .As the imido-mesityl substituents are considerably less bulky than the terphenyl groups in l imides , we inve3 to an orange solution of 5 at room temperature resulted in decolorization over an approximate 5 minute period (7) or SiMe3 (8) groups, consistent with their incorporation in the product. In agreement with these data, the composition of the products as the first examples of indium tetrazenido compounds was confirmed by X-ray crystallography scale\" fill=\"currentColor\" stroke=\"none\">NMes\u2019, and that the formation of the unsymmetrical tetrazene 8 strongly endorses the previously assumed (2 + 3)-cycloaddition pathway of transient imides.Addition of a solution of RNe period . NMR spelography , Table 47\u00b7(toluene)]2 lies on a two-fold rotation axis that forms a dimeric unit, with K\u00b7\u00b7\u00b7\u03c0\u2013aryl interactions between Mes-groups and an incorporated toluene molecule that encapsulates the cation (C\u00b7\u00b7\u00b7K distances 3.006(5)\u20133.993(5) \u00c5). Crystallization of [7\u00b7(toluene)]2 in the presence of 18-crown-6 (18-c-6) disrupts dimer formation to afford [K(18-c-6)][In(NONAr)] (7 (18-c-6)). This salt forms a contact ion-pair linked by K\u00b7\u00b7\u00b7N interactions to the two central nitrogen atoms of the InN4-tetrazene ring (2.820(2) \u00c5 and 2.939(2) \u00c5, Fig. S27Ar)] also crystallizes as the dimer [8]2, with the potassium cations linking non-symmetry related units through a combination of K\u00b7\u00b7\u00b7N (2.641(6)\u20132.913(6) \u00c5) and K\u00b7\u00b7\u00b7\u03c0\u2013aryl (3.024(9)\u20133.264(8) \u00c5) interactions.The dimesityl derivative [VII, 7 and 8 represent the first structurally characterized indium compounds containing the tetrazenide ligand, and are unique examples where the MN4-heterocycle is a component of an anionic species.In all cases the anion comprises two approximately orthogonal rings fused at a four-coordinate indium centre. The metallotetrazene rings are essentially planar, with nitrogen\u2013nitrogen bond lengths indicating double-bond character between atoms in the 3- and 4-positions of the heterocycle see VII, . These pi) to In(iii). The isolated compounds have been structurally verified as a new class of anionic indium imide, shown computationally to contain In\u2013Nimide multiple bonds. Furthermore, we demonstrate that the reduced size of the imide-substituent in this work compared with previous examples allows access to the In\u2013Nimide bond, demonstrated by the reaction with additional equivalents of azide. The products from this (2 + 3)-cycloaddition are the first time that this reaction has been extended to indium, and crystallographic analysis confirms a planar InN4-heterocycle as a component of the anion.This work describes the first detailed reactivity study of an indyl-anion. We confirm that the negative charge associated with the indium centre does not adversely affect their ability to act as a reducing agent towards organic azides. The reactions proceed cleanly with elimination of dinitrogen and oxidation of the indium(There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A combination of MS and computation on \u03bc-nitrido bridged diiron complexes reveals H2O2 binding to the complex and generates an oxidant capable of oxidizing methane. iv)\u2013oxo species have been identified as the active intermediates in key enzymatic processes, and their catalytic properties are strongly affected by the equatorial and axial ligands bound to the metal, but details of these effects are still unresolved. In our aim to create better and more efficient oxidants of H-atom abstraction reactions, we have investigated a unique heteroleptic diiron phthalocyanine complex. We propose a novel intramolecular approach to determine the structural features that govern the catalytic activity of iron(iv)\u2013oxo sites. Heteroleptic \u03bc-nitrido diiron phthalocyanine complexes having an unsubstituted phthalocyanine (Pc1) and a phthalocyanine ligand substituted with electron-withdrawing alkylsulfonyl groups (Pc2RSO) were prepared and characterized. A reaction with terminal oxidants gives two isomeric iron(iv)\u2013oxo and iron(iii)\u2013hydroperoxo species with abundances dependent on the equatorial ligand. Cryospray ionization mass spectrometry (CSI-MS) characterized both hydroperoxo and diiron oxo species in the presence of H2O2. When m-CPBA was used as the oxidant, the formation of diiron oxo species (Pc2RSO)FeNFe(Pc1) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO was also evidenced. Sufficient amounts of these transient species were trapped in the quadrupole region of the mass-spectrometer and underwent a CID-MS/MS fragmentation. Analyses of fragmentation patterns indicated a preferential formation of hydroperoxo and oxo moieties at more electron-rich iron sites of both heteroleptic \u03bc-nitrido complexes. DFT calculations show that both isomers are close in energy. However, the analysis of the iron(iii)\u2013hydroperoxo bond strength reveals major differences for the (Pc1)FeN(Pc2RSO)FeIIIOOH system as compared to (Pc2RSO)FeN(Pc1)FeIIIOOH system, and, hence binding of a terminal oxidant will be preferentially on more electron-rich sides. Subsequent kinetics studies showed that these oxidants are able to even oxidize methane to formic acid efficiently.Iron( For instance, iron(iv)\u2013oxo intermediates contribute as the active oxidant in heme monoxygenases, like the cytochromes P450, whereas in the structurally analogous peroxidases the detoxification of hydrogen peroxide to water is catalyzed.iv)\u2013oxo active species in their catalytic cycle to transfer an oxygen atom to substrates with functions ranging from DNA base repair and the biosynthesis of antibiotics.iv)\u2013oxo species have been identified as originating from the metal-substrate orbital-interactions and the electron-transfer pathways during the chemical reaction.iv)\u2013oxo intermediates in chemistry and biology, many studies have been devoted to the preparation and spectroscopic characterization of these short-lived species using enzymesiv)\u2013oxo species on the porphyrin,10High-valent ironFeNFe(Pc)], IIIFeIV and FeIVFeIV oxidation states.2O2 and m-chloroperbenzoic acid (m-CPBA), to form a high-valent diiron\u2013oxo species, i.e. . The addition of H2O2 to \u03bc-nitrido diiron tetra-t-butylphthalocyanine 8, [(PctBu)FeNFe(PctBu)] (tBu)FeIVNFeIII(PctBu)\u2013OOH], followed by the generation of the diiron\u2013oxo species, , as identified by electrospray ionization-mass spectrometry (ESI-MS) using labelled H218O2.IVNFeIV(TPP+\u02d9) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO] with m-CPBA oxidant at \u201390 \u00b0C, and characterize it by ESI-MS, low-temperature UV-vis, electron paramagnetic resonance (EPR) and M\u00f6ssbauer spectroscopic techniques.\u03bc-Nitrido diiron phthalocyanines belong to the class of stable binuclear single atom bridged complexes that are known to bind metal ions in high oxidation states,(PctBu)] , resulteiv)\u2013nitrido group affect the catalytic functions of the iron(iv)\u2013oxo moiety and how can these be modified? In order to answer these questions, we decided to synthesize localized structures with non-equivalent iron sites, where each of the iron atoms is placed into macrocyclic ligands with very different electronic properties. Our approach opens interesting possibilities but also leads to deeper insight into the formation of the active species responsible for the catalysis. In particular, since such complexes with localized structure have two possible sites where an iron(iv)\u2013oxo species can be formed. Therefore, we designed unique chemical complexes that are based on the same phthalocyanine ligand structure, but exhibiting different electronic properties due to different substitution patterns. In particular, we created structures with one macrocyclic ligand with an electron-poor phthalocyanine group with four or eight alkylsulfonyl substituents, whereas the other macrocyclic ligand contained a more electron-rich unsubstituted phthalocyanine macrocycle. We report here the first synthesis and characterization of this series of unique heteroleptic structures scale\" fill=\"currentColor\" stroke=\"none\">O9) or hydroperoxo (9\u2013OOH) bound. The studies show that the electron-withdrawing character of the equatorial ligand, i.e. the phthalocyanine moiety, affects the strength of the iron(iii)\u2013hydroperoxo bond, and, thereby determines the site where the oxo group will bind. The work reveals the subtleties of ligand binding on the chemical and ultimately catalytic properties of metal\u2013oxo complexes. The ESI-MS and DFT results suggest the higher catalytic activity for more electron-rich iron sites. This prediction was confirmed in the catalytic heterogeneous oxidation of methane with H2O2 using three \u03bc-nitrido diiron phthalocyanine complexes with different substitution patterns.The macrocyclic \u03bc-nitrido diiron phthalocyanine provides a unique possibility to probe the differences in chemical properties of the two iron centers within the same molecule. The question, therefore, is: How do the functional properties of the ironFe(iv) unit are not necessarily inequivalent in terms of the oxidation state,i.e. with different electronic properties,iii) complexes, which are then mixed in a solution with sodium azide and \u03b1-chloronaphthalene to form the \u03bc-nitrido diiron complexes.Tetrapyrrolic ligands, such as porphyrin and phthalocyanine, can be used to form dimeric complexes.5 is prepared by a modified procedure4 with H2O2 in acetic acid at 79% yield. Iron(ii) octahexylsulfonyl phthalocyanine 6 is obtained by heating 5 in an o-dichlorobenzene\u2009:\u2009dimethylformamide (3\u2009:\u20091) mixture commonly used for alkylsulfonyl phthalonitriles2 (ii) phthalocyanine in \u03b1-chloronaphthalene in the presence of NaN3.3 and 7 were prepared by using a 10-fold excess of unsubstituted iron phthalocyanine 1 relative to the monomeric alkylsulfonyl phthalocyaninatoiron(ii) 2 or 6, respectively. These conditions allow the formation of the desired heteroleptic complexes . The lower yield of 7 with respect to 3 is attributed to a steric hindrance of the octasubstituted ligand 6.The synthesis of alkylsulfonyl substituted phthalonitriles is achieitriles2 . The preomplexes together3 and 7 was confirmed by FT-IR, UV-vis and EPR spectroscopy and ESI-MS studies. The ESI-MS spectra of these mixed ligand complexes exhibit prominent molecular peaks corresponding to the expected values of the molecular ion: m/z = 1943.4 [M]+ for 3 and m/z = 2335.6 [M]+ for 7 ] at 930 cm\u20131 and for homoleptic complex [(Pc)FeNFe(Pc)] at 915 cm\u20131.The successful preparation of 3 and homoleptic complex 8 as reference. Interestingly, the XES spectra of 3 and 8 are virtually identical in the solid phase module peaks of 3 for the first coordination shell. This is most likely due to differences in their Debye\u2013Waller factors, as a result of more position isomers for 8 as compared to 3. The effective disorder is therefore higher in 8, and manifests itself in the EXAFS spectra with increased Debye\u2013Waller parameters. Note that asymmetrization of the Fe\u2013N\u2013Fe fragment would lead to the decrease of Fe\u2013N\u2013Fe related features, as a result of weakening of the multiple scattering effects,3 and 8 reveals a symmetric Fe\u2013N\u2013Fe fragment in both complexes despite differences in the ligand properties in 3.No significant differences in the interatomic distances of the heteroleptic complex spectra in eithe3 and 8, we performed a series of XANES experiments. In contrast to the XAS, XES and EXAFS studies reported above, the XANES studies reveal a difference between the two structures \u2013oxo species readily in a reaction with active oxygen atom donors. The formation of the iron(iv)\u2013oxo species, therefore, comprises of two fundamental steps: (i) coordination of the oxygen donor to the iron and (ii) heterolytic cleavage of the O\u2013O bond of the peroxide unit. In the homoleptic complex both iron sites are identical and, as such, only one isomeric iron(iv)\u2013oxo species can be formed. In the heteroleptic complex, by contrast, there are, in principle, two isomeric iron(iv)\u2013oxo products possible (iv)\u2013oxo complex? In order to find out whether a site-specific iron(iv)\u2013oxo complex will be formed and what the properties of the ligands are that determine these issues, we performed a detailed combined ESI-MS and DFT study.Despite the initial high oxidation state of iron, the \u03bc-nitrido diiron phthalocyanine complexes form the high-valent iron(possible . The que2) was determined to be \u223c60 eV for the fragmentation of the diiron species into monomeric units without consecutive dissociation patterns. Fragmentation patterns of the heteroleptic compounds (iv)\u2013oxo species, whether it is electron-rich or electron-deficient. Indeed, the analysis of the initial fragmentation pattern provides a composition of two different phthalocyanine species with or without oxo and/or nitrogen ligands, which enables us to conclude whether the oxo species is attached to the electron-deficient Fe(Pc2RSO) ligand or to the more electron-rich Fe(Pc) fragment and the results are schematically depicted in To a \u223c103 + HOOH]+ core at m/z 582\u2013585 and 603 containing N, OH and H2O2 ligands are much larger than those with Fe(Pc2) fragments that are found in the m/z range of 1376\u20131379 and 1397. The intensity of naked [Fe(Pc1)]+ ion at m/z 568 obtained after loss of oxygen ligands is also much higher than that of protonated [Fe(Pc2)+H]+ ion at m/z 1362.The principal ions formed upon fragmentation of [+ HOOH]+ are ions3 + O]+ are identical to those theoretically predicted for the diiron\u2013oxo complex scale\" fill=\"currentColor\" stroke=\"none\">O3), which confirms its formation. Upon CID MS/MS conditions, the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO3 ion behaves very similarly to [3 + HOOH]+ FeNFe(Pc2)]+ (3) at m/z 1943.46. Importantly, the fragmentation of [3 + O]+ produces almost exclusively [Fe(Pc1)]+ ions at m/z 568, 585, 600, whereas only minor amounts of [Fe(Pc2)]+ ions are detected at m/z 1362.The exact molecular mass and isotopic distribution pattern of + and + ions on the basis of exact molecular mass and isotopic distribution of the cluster. A large signal at m/z 585 is attributed to either + or [(Pc1)(N)Fe\u2013OH]+ ion formed by hydrogen atom abstraction from organic solvent by the oxo species with strong oxidizing properties. As expected, all these Fe(Pc1) oxygen containing species lose oxygen and nitrogen ligands to form naked [Fe(Pc1)]+ ions under CID-MS/MS conditions. The analysis of the fragmentation of [3 + H2O2]+ and [3 + O]+ ions suggests that high valent diiron species containing oxo ligands preferentially bind at more electron-rich iron sites such as Fe(Pc1).It should be noted here that fragments containing oxo ligands were only detected at the unsubstituted, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO3 was also obtained using m-chloroperbenzoic acid as the oxygen donor. Importantly, the CID-MS/MS spectrum of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO3m-CPBA shows only fragments derived from the Fe(Pc1) core (1) fragments bearing an oxo-ligand at m/z 585 and 600 are much stronger scale\" fill=\"currentColor\" stroke=\"none\">O32O2H species fragments with oxo-ligands are observed core . The sigstronger compared species . This su9, which is an analogue of 3 whereby the adamantylsulfonyl groups are replaced by methylsulfonyl: [(Pc1)FeNFe(Pc2MeSO)]. In addition, we calculated the iron(iv)\u2013oxo form of 9, i.e. , and finally the iron(iii)\u2013hydroperoxo complex [9\u2013OOH]\u2013. Although we calculated all structures in the lowest lying doublet, quartet and sextet spin states, actually in all cases the doublet spin state is the ground state and well separated from the other spin states. We, therefore, will focus in the main text on the doublet spin state only; all other results can be found in the ESITo support the experimental results and gain insight into the relative stability of \u03bc-nitrido diiron phthalocyanines with different substitution patterns of the distal ligand, we performed a detailed density functional theory (DFT) study on structure 9 with UB3LYP and UBP86 methods and the structures (1) group has a spin of 0.32, whereas the other iron atom has a spin of only 0.29. This small change in radical character between the two iron atoms, due to the electron-withdrawing/donating groups attached to the phthalocyanine ligands may be responsible for the preferred site of hydrogen peroxide binding. In particular, the larger radical character of the Fe(Pc1) group will favour the binding of an active oxidant over the Fe(Pc2MeSO) group.We initially optimized the geometry of doublet spin ructures show onl9\u2013OOH]\u2013 and reoptimized all geometries in the gas phase, see 1)FeIIINFeIV(Pc2MeSO)]\u2013, designated [9\u2013OOH]A\u2013, and [(Pc1)FeIVNFeIII(Pc2MeSO)OOH]\u2013 or [9\u2013OOH]B\u2013. Similarly to previous studies on iron(iii)\u2013hydroperoxo porphyrin complexes of mononuclear iron systems, the doublet spin state is the ground state in all cases.iv)\u2013nitrido group with an unpaired electron on the iron(iii)\u2013hydroperoxo group. Although the energy gap between the two structures is small, the most stable isomer is structure [9\u2013OOH]A\u2013 by 1.8 kcal mol\u20131 over [9\u2013OOH]B\u2013. Therefore, the iron(iii)\u2013hydroperoxo is preferentially bound to the site with electron-donating substituents attached to the phthalocyanine manifold. This is a surprising result as previous computational and experimental studies found very little effect, for instance, of meso-substitution of porphyrin rings on the electron affinity of the iron(iv)\u2013oxo group.9\u2013OOH]A\u2013versus [9\u2013OOH]B\u2013 confirms the experimental MS results described above that more fragmentation is found from the [9\u2013OOH]A\u2013 isomer.Subsequently, we added a hydroperoxo group to form [9\u2013OOH]A\u2013 and [9\u2013OOH]B\u2013 show some critical differences between the two structures. Thus, the iron(iii)\u2013hydroperoxo group has larger radical character on the metal when it has a ligand with electron-donating substituents (Pc1) than one with electron-withdrawing substituents (Pc2MeSO): \u03c1Fe1 = \u20130.80 for [9\u2013OOH]A\u2013 and \u03c1Fe1 = \u20130.75 for [9\u2013OOH]B\u2013. The same is true for the iron(iv)\u2013nitrido group that sees the spin density polarize more towards the iron with the Pc1 ligand rather than the Pc2MeSO ligand. Therefore, electron-withdrawing substituents on the phthalocyanine scaffold create metal centers with lesser radical character and as such should be less reactive.The group spin densities reported in \u20131, however, it is not ruled out that a mixture of isomers will be formed in the process dependent on temperature, pressure, solvent environment etc. Indeed, the mass spectra show the presence of both type A and type B complexes as major and minor species, respectively.In summary, the computational results implicate preferential binding on the iron center with electron-donating substituents by a few kcal moli.e. FeIIIFeIV.18 On the other hand, studies on related \u03bc-oxo/\u03bc-hydroxo diiron porphyrin complexes show that they often have non-equivalent iron sites, whereby their oxidation states are very sensitive to structural and environmental perturbations.3 and reference homoleptic 8 complexes are practically the same, which indicates little or no effect of desymmetrization of the diiron unit. However, the CID-MS/MS data on clearly indicate the preferential formation of an iron(iv)\u2013oxo species at the more electron-rich, i.e. unsubstituted, phthalocyanine unit (Pc1). Noteworthy, the same trend was observed with either heteroleptic dimer 3 or 7 and too was found to be independent on the nature of the oxygen donor, i.e. H2O2 or m-CPBA.High-valent iron complexes bearing iron\u2013oxygen PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO9] isomers, namely or A and or B. The structures of A and B were calculated with B3LYP and BP86. The B3LYP and BP86 optimized structures show dramatic differences in chemical structure but follow the same trends upon adding substituents to one of the phthalocyanine scaffolds. Firstly, the iron\u2013oxo bond is short with B3LYP scale\" fill=\"currentColor\" stroke=\"none\">O9]A and 1.652 \u00c5 for structure B), which implicates an iron(iv)\u2013oxo double bond. These values match computational and experimental measurements of mononuclear iron(iv)\u2013oxo complexes of porphyrin systems excellently.iv)\u2013oxo bond length drops by 0.005/0.004 \u00c5 at B3LYP/BP86 level of theory when electron-withdrawing substituents are added at a distance of more than 8 \u00c5 from the iron center in the equatorial plane. Consequently, a significant difference in iron\u2013oxo bond length is obtained between structures A and B, which leads to stability differences and may be the primary reason for the difference in stability between doublet A and B structures. A change of this magnitude was not observed previously in meso-substituted iron porphyrins.iv)\u2013oxo species.To find out, whether there are stability differences for \u03bc-nitrido diiron\u2013oxo complexes with heteroleptic ligand systems as well, we decided to do an additional DFT study into the two [1)FeNFe(Pc2MeSO)], we decided to calculate the bond dissociation energy (BDE) of the hydroperoxo unit in [9\u2013OOH]A\u2013 and [9\u2013OOH]B\u2013 based on eqn (1). The calculated values for both complexes are given in FeOOH into different contributions as explained below. Of course, the BDEFeOOH difference between [9\u2013OOH]A\u2013 and [9\u2013OOH]B\u2013 is the same as the stability difference reported in To establish the origin of the hydroperoxo binding to A\u2013 and [9\u2013OOH]B\u2013 gives the effect of the second Pc unit on the BDE values for eqn (1), EPc, namely through \u03c0\u2013\u03c0 stacking interactions. As can be seen, the size and shape of the second Pc group has a major impact on the BDEFeOOH value, even though this bond is at a distance of well over 4 \u00c5. Thus, the BDEFeOOH is strongly increased for the (Pc2MeSO)FeOOH system as compared to the (PcH)FeOOH system by more than 20 kcal mol\u20131.Subsequently, we removed the phthalocyanine group of the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV(Pc) unit altogether and replaced it by a point charge. Again a single point calculation was performed to determine the relative BDEFeOOH values using eqn (1). These values establish the quantum mechanical effect (EQM) of the axial ligand upon the Fe\u2013OOH binding energy. Thus, the axial N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV(Pc2MeSO) group gives a quantum mechanical effect that is dominated by the presence of the Pc2MeSO interaction with the rest of the system and has little contribution from the FeIV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN moiety. By contrast, the removal of the N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tFeIV(PcH) group has a major effect on the BDEFeOOH value and the system is considerably stabilized. Clearly, the equatorial ligands have a major contribution towards the binding of hydroperoxo groups to an iron scaffold and strengthen its bonding. This further shows that electron-withdrawing and electron-donating substituents can be used to manipulate the binding site of (hydro)peroxo moieties, and affect their stability and ultimately their catalytic properties.In a final set of calculations, we removed the N2tBu)4]2N, (FePc)2N and [FePc(tBu)4]2N (8) in the oxidation of methane. The complexes were supported onto silica and the heterogeneous oxidation of methane was performed in water containing 75 mM H2SO4 at 60 \u00b0C 4]2N < (FePc)2N < [FePc(tBu)4]2N the values of total turnover numbers strongly increase: 32.1 \u2192 102.9 \u2192 223.4. These turnover numbers reflect the difference in O\u2013H bond strength of iron(iii)\u2013hydroxo complexes with different phthalocyanine groups. Thus, previously we showed that the rate constant of hydrogen atom abstraction reactions correlates linearly with the O\u2013H bond dissociation energy of the corresponding iron(iii)\u2013hydroxo complex formed.tBu)4]2N complex bearing donating alkyl substituents showed an excellent performance in the mild methane oxidation providing a very high turnover number of 223.With all the catalysts, methane was efficiently oxidized to formic acid with 88\u201397% selectivity. Methanol was detected by GC-MS in trace amounts and formaldehyde is readily oxidized under the reaction conditions. Interestingly, with growth of the electron-donating properties of phthalocyanine ligand along the series 2N,Solvents were dried and distilled according to published procedures.4) was stirred in acetic acid (50 mL) at 90 \u00b0C, and subsequently a 33% solution of hydrogen peroxide (23 mL) was added in 1 mL portions over 4 h. The resulting mixture was allowed to cool to room temperature and stirred overnight. The resulting white precipitate was collected by filtration, washed with water and crystallized from ethanol (30 mL) to give 5 as a white powder. Yield 79% (1.4 g). Mp 113\u2013114 \u00b0C. Anal. calcd for C20H28N2O4S2: C, 66.62; H, 7.83; N, 7.77; S, 17.79. Found: C, 67.20; H, 7.70; N, 7.93; S, 17.57. 1H NMR (500 MHz CDCl3): \u03b4 = 0.8 , 1.3\u20131.7 , 3.7 , 8.6 ppm. ESI-MS: m/z: 447.23 [M + Na]+; IR (KBr) \u03bd (cm\u20131): 3097, 2959, 2928, 2861, 2244, 1545, 1464, 1336, 1314, 1149, 1125, 919, 795, 728, 648, 570, 525, 512, 474.1,2-Dicyano-4,5-bis(hexylthio)benzene (n-hexylsulfonyl)benzene (5) was heated at 130 \u00b0C in a mixture of o-dichlorobenzene\u2013DMF (3\u2009:\u20091) under argon for 8 h in the presence of iron(ii) chloride (0.15 mmol). The solvent was then concentrated under reduced pressure and the resulting green solid was recovered with dichloromethane and washed with water. Phthalocyanine 6 was purified by chromatography on silica gel using a mixture of di-chloromethane\u2009:\u2009ethanol (100\u2009:\u20091) as the eluent. Yield: 23% (61 mg). ESI-MS: m/z calc. for C80H112FeN8O16S8, 1172.5; found 1753.3 [M + H]+. UV-vis (CHCl3): \u03bbmax (log\u2009\u03b5) = 670 (5.2), 354 (5.0) nm; IR (KBr) \u03bd (cm\u20131): 1310, 1100, 1070, 808, 740.A mixture of 1,2-dicyano-4,5-bis(1 (1 mmol), sodium azide (1.5 g) and alkylsulfonyl phthalocy-aninato-iron(ii) (0.1 mmol) were suspended in \u03b1-chloronaphthalene (20 mL) under argon. The mixture was heated for 24 h at 190 \u00b0C under intensive stirring. The solvent was removed under reduced pressure. The remaining blue solid was diluted in CH2Cl2 (100 mL), filtrated and concentrated to be loaded on a silica gel column first eluted with CH2Cl2 to remove impurities. Then, the desired heteroleptic dimer was collected using CH2Cl2\u2009:\u2009EtOH (10\u2009:\u20091) as the eluent. Evaporation of solvent afforded the pure heteroleptic dimer as a dark blue powder.FePcm/z calc. for C104H88Fe2N17O16S8, 1943.8; found, [M]+, dicharged species calc. for 971.2287; found 971.2332. UV-vis (CHCl3): \u03bbmax (log\u2009\u03b5) = 635 (4.5), 338 (4.3) nm. IR (KBr) \u03bd (cm\u20131): 929 scale\" fill=\"currentColor\" stroke=\"none\">N\u2013Fe).Yield: 64% (124 mg). ESI-HRMS: m/z calc. for C112H128Fe2N17O16S8, 2334.6186; found, 2334.6091 [M]+. UV-vis (CHCl3): \u03bbmax (log\u2009\u03b5) = 645 (4.3), 338 (4.1) nm. IR (KBr) \u03bd (cm\u20131): 935 scale\" fill=\"currentColor\" stroke=\"none\">N\u2013Fe).Yield: 52% (120 mg). ESI-HRMS: 2tBu)4]2N, (FePc)2N and [FePc(tBu)4]2N complexes were supported onto silica with loading of 20 \u03bcmol g\u20131 according to a published procedure.The [FePcFeIIINFeIII(Pc2MeSO)], whereby the adamantyl-sulfonyl groups were replaced by SO2CH3 as shown in iv)\u2013oxo group, namely scale\" fill=\"currentColor\" stroke=\"none\">O9A) and scale\" fill=\"currentColor\" stroke=\"none\">O9B). Furthermore, structures were generates with an iron(iii)\u2013hydroperoxo group, i.e. [(PcH)FeIIINFeIII(Pc2MeSO)OOH] (9\u2013OOHA) and [HOO(PcH)FeIIINFeIII(Pc2MeSO)] (9\u2013OOHB). All individual structures were calculated in the lowest energy doublet, quartet, and sextet spin states, but the doublet spin state is the ground state in all cases.Density functional theory (DFT) procedures were employed using previously calibrated and benchmarked methods\u03b6 type basis set on iron (LACV3P+) and 6-311+G* on the rest of the atoms: basis set BS2. Finally, solvent corrections were obtained from single point calculations in Jaguar using the polarized continuum model with a dielectric constant mimicking dichlorobenzene. However, none of these calculations changed the spin state ordering or site preference, see ESITo test the effect of the basis set on the spin state ordering and relative energies, we calculated single points with a triple-via a harmonic frequency calculation, which gave real vibrational frequencies only.These DFT methods have been extensively used in calculations of iron\u2013porphyrin complexes and were shown to reproduce experimental rate constants and spin state orderings in good agreement with experiment.Supplementary informationClick here for additional data file."}
+{"text": "PBM data was replaced with SVG by xgml2pxml:000000000000000000000000000000000000111111111111000000000000111111111111000000000000000000000000000000000000C), imine (CN), methylenephosphine (CP), iminophosphine (NP), diazene (NN), diphosphene (PP) and cyclopropane (\u0394). The data were obtained from ab initio geometric optimization and frequency calculations at HF, B3LYP, MP2 and CCSD levels of theory on 6\u2013311++G basis set. Input structures were generated by shell scripts and run by Q-Chem quantum chemical package. The output files were processed to extract geometric and energetic information by Wolfram Mathematica.This article presents theoretical data on geometric and energetic features of halogenated compounds of ethene (C The data in this paper were generated and optimized in vacuum by C), imine (CN), methylenephosphine (CP), iminophosphine (NP), diazene (NN), diphosphene (PP) and cyclopropane (\u0394) where substitutions are via halogenation with all degrees of substitution from mono- to tetra-substitution. The total numbers of all possible compounds are as follows: 175 for CC were generated partly by using a Unix shell script previously described elsewhere . The ab package to optim package to extra"}
+{"text": "Chiral C2- and C1-symmetric BINOL-derived bis(phosphoric acid) catalysts facilitated the enantioselective aza-Friedel\u2013Crafts reaction of 2-methoxyfuran with \u03b1-ketimino esters. C2- and C1-symmetric BINOL-derived bis(phosphoric acid) catalysts, which have OP scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)2/OP scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)(OR) moieties at the 2,2\u2032-positions, were developed and used for the enantioselective aza-Friedel\u2013Crafts reaction of 2-methoxyfuran with \u03b1-ketimino esters for the first time. The intramolecular conjugated double hydrogen bond network is a key to increasing the Br\u00f8nsted acidity and preventing deactivation of the catalysts. Highly functionalized \u03b1-amino acid derivatives with a chiral quaternary carbon center could be transformed into versatile optically active N- and O-heterocycles and an \u03b1-aryl-substituted serine.Chiral In such a BBA system, one hydrogen atom of an XH group might participate in an intramolecular hydrogen bond with the other XH group, which might be activated and thus used for activation of the substrate. Since 2003, when Rawal reported the first example of an intramolecular single hydrogen bonding network in chiral TADDOLs 2. In sharp contrast, we envisioned that an intramolecular double hydrogen bond network may represent a new strategy for the design of chiral Br\u00f8nsted acid catalysts. However, a simple and closed double hydrogen bond network, as seen in a dimeric structure of two molecules of carboxylic acids, would lose both the Br\u00f8nsted acid- and base-functions upon neutralization. Therefore, here we developed chiral C2-symmetric BINOL-derived bis(phosphoric acid) catalysts (R)-5 as bis(diprotic acid)s R*(XH2)2, which have two OP scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)2 moieties at the 2,2\u2032-positions of the chiral binaphthyl backbone (R)-5, chiral C1-symmetric catalysts (R)-10, which have OP scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)2/OP scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)(Oi-Pr) moieties, were also developed. Remarkably, outside of the conjugated intramolecular double hydrogen bond network, the Br\u00f8nsted acid moiety would still exist and work as an active center by the BBA methodology.The hydrogen bond network of chiral multiprotic acid catalysts plays an important role in activating Br\u00f8nsted acidity, controlling conformational flexibility, and producing high enantioselectivity.backbone . Based o2 (1a1a and particularly 2 under acidic conditions (entries 4\u20136). Fortunately, phosphoric acids could be used without the serious generation of byproducts due to their suitable Br\u00f8nsted acidity for this reaction, although the yields of product 3a were moderate (entries 7 and 8). Next, we examined conventional chiral phosphoric acid (R)-4a (entry 9), which would be less aggregatable than the less bulky achiral phosphoric acids in entries 7 and 8. As a result, although the pKa of (R)-4a would be similar to those of the achiral phosphoric acids in entries 7 and 8, the catalytic activity was greatly improved (see the ESIR)-4b with electron-withdrawing CF3 groups in its 3,3\u2032-diaryl moieties was used, the reaction was accelerated, although the enantioselectivity was still low (40% ee) (entry 10). Moreover, well-acknowledged bulky (R)-4c was much less active than (R)-4a and (R)-4b (entry 11). In contrast, chiral C2-symmetric bis(phosphoric acid) (R)-5aR)-4a\u2013c, and 3a was obtained in 82% yield with 70% ee within 5 h (entry 12).R)-5b derived from (R)-3,3\u2032-2C6H3)2-BINOL improved the enantioselectivity (76% ee) of 3a (entry 13). (R)-5c with a 5,5\u2032,6,6\u2032,7,7\u2032,8,8\u2032-H8-binaphthyl backbone showed lower catalytic activity than (R)-5a and (R)-5b, and a prolonged reaction time (24 h) was needed (entry 14). Moreover, we optimized \u03b2,\u03b3-alkynyl-\u03b1-imino esters 1 with the use of (R)-5b -3b was obtained in 83% yield with 91% ee (eqn (1)). Remarkably, we could perform a 1.89 g-scale synthesis of (S)-3b (77% yield with 91% ee), and 99% of (R)-5b could be recovered.We initially examined the aza-Friedel\u2013Crafts (FC) reaction of 2-methoxyfuran 2 with \u03b2,\u03b32 1a. As a reR)-5c\u00b7(pyridine)2 was crystallized, and the results of an X-ray analysis are shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO)(OH)2 moieties at the 2,2\u2032-positions of the H8-binaphthyl backbone coordinate with each other, and the conjugated double hydrogen bond network is unambiguously formed at the center of the monomeric molecules. Pyridines are coordinated BBA-activated protons, which would be considered to activate the substrate in a similar way. In this regard, the role of the two outside protons was next examined with the use of monomethyl-protected (R)-6a and dimethyl-protected (R)-6b (R)-6a showed almost the same catalytic activity (81% yield and 91% ee of 3b) as (R)-5b, whereas (R)-6b gave a poor result (22% yield and 34% ee of 3b) in the reaction of 2 with 1b. This result strongly suggests that two activated protons in (R)-5b should be independent of each other, although the absence of both protons results in a loss of catalytic activity. In contrast, the protons in the tight structure of a double hydrogen bond network might not be directly involved in promoting the reaction as possible Br\u00f8nsted acids.We now turn our attention to mechanistic aspects. It is important to identify the intramolecular double hydrogen bond network in the catalysts. Fortunately, (d (R)-6b . As a re2 with 1a with the use of (R)-5b or (R)-4a (R)-5c\u00b7(pyridine)2, a linear relationship was observed for (R)-5b, and the yields were almost constant (71\u201375%) (R)-4a (R)-4a unlike (R)-5b. Indeed, although both (R)-5b and (R)-4a have almost the same sterically hindered 3,3\u2032-diaryl moieties, the strongly Br\u00f8nsted basic P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO moiety is still free in (R)-4a. It is quite unlike the situation in (R)-5b, which has a core hydrogen bond network through the \u201cintramolecular dimerization\u201d of two P scale\" fill=\"currentColor\" stroke=\"none\">O)(OH)2 moieties. Thus, the much better catalytic activity of (R)-5b compared to (R)-4a might be attributed to not only the stronger acidity of (R)-5b due to a BBA system but also the monomeric active species of (R)-5b due to the closed P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO moieties.20Moreover, a non-linear effect was examined in the reaction of r (R)-4a . As expe(71\u201375%) . In cont) (R)-4a .18 This 1a and 1b. Due to their synthetic importance, we chose aryl \u03b1-ketimino esters, such as 7a (R)-5b was not effective for the reaction of less reactive 7a, unlike more reactive 1a and 1b, and (R)-8a was barely obtained with 15% ee at slightly higher temperature (\u201360 \u00b0C) (entry 3). To improve the enantioselectivity, stereocontrol by more bulky substituents at the 3,3\u2032-positions of the C2-symmetric catalysts (R)-5 should be needed. However, we could not introduce phosphoric acid moieties at the 2,2\u2032-positions of the bulky 3,3\u2032-Ar2-BINOL-skeleton . Instead, an extremely bulky C1-symmetric catalyst (R)-9c with 2,4,6-Cy3C6H2 at the 3-position could be readily prepared as well as (R)-9a and (R)-9b . However, since two different active Br\u00f8nsted acid centers would compete, the enantioselectivity was low (11\u201318% ee), as expected (entries 4\u20136). Based on the above consideration of C2-symmetric catalysts (R)-5, we designed the site-selectively mono-i-Pr-capped catalysts (R)-10.R)-10c with extremely bulky 2,4,6-Cy3C6H2 at the 3-position, the reaction proceeded smoothly, and (R)-8a was obtained in 93% yield with 95% ee (entry 9). The bulkiness of the aryl moiety at the 3-position is important, since slightly less hindered (R)-10b with 2,4,6-i-Pr3C6H2 was less effective (entry 8), and much less hindered (R)-10a with 3,5-Ph2C6H3 was entirely ineffective (entry 7). Conventional chiral phosphoric acids, such as (R)-4b and (R)-4c, were not effective . When we investigated simple o-, m-, and p-tolyl-substituted substrates (7i\u2013k), p-tolyl 8i and m-tolyl 8j were obtained in high yields with high enantioselectivities , whereas o-tolyl 8k could not be obtained probably due to steric hindrance. Indeed, less sterically hindered o-F-C6H48c and 1-naphthyl 8m were obtained with high enantioselectivities . 2-Naphthyl 8l and heteroaryl 8n were also obtained successfully . Unfortunately, however, a low-reactive aliphatic substrate 7o could not be used, and no reaction proceeded. Moreover, instead of 2-methoxyfuran 2, 2-ethoxyfuran8p was obtained in 94% yield with 94% ee.With the optimized catalyst in hand, we next examined the scope of aryl \u03b1-ketimino esters 7 . As a reC2-symmetric (R)-5b and C1-symmetric (R)-10c. As seen above, (R)-5b-catalysis of 1b and 2 provided (S)-3b, and (R)-10c-catalysis of 7a and 2 provided (R)-8a. Therefore, the observed absolute stereochemistries in 5b and 8a were opposite each other. This changeover might be caused by the geometry of \u03b1-ketimino esters (E)-1bZ)-7aS)-3b was obtained in 14% yield with 6% ee by using (R)-10c (eqn (2)), whereas (R)-8a was obtained in 66% yield with 21% ee by using (R)-5b (eqn (3)). Overall, chiral C2- and C1-symmetric bis(phosphoric acid) catalysts were complementary, and either catalyst that was suitable for one reaction would not be suitable for the other reaction from the viewpoint of yield and enantioselectivity. Although preliminary possible transition states are considered as a working model to give 11 quantitatively. Next, 11 was reduced under typical reaction conditions. Wilkinson's catalyst completely reduced the acetylene moiety of 11, and 12 was obtained quantitatively. Lindlar's catalyst facilitated the selective hydrogenation of acetylene at 0 \u00b0C to give vinyl compound 13 in 94% yield, whereas both acetylene and the Cbz moieties of 11 were reduced at room temperature and 14 was obtained quantitatively. Furthermore, the NH2 moiety of 14 was protected by di-tert-butyl dicarbonate (Boc2O) in 83% yield, and the corresponding product was consequently treated with N-bromosuccinimide (NBS) to give 1,4-dicarbonyl compound 15 in 68% yield via furan cleavage. Finally, chemoselective reduction of the keto moiety of 15 with the use of CeCl3/NaBH4 gave \u03b3-butenolide 16 in 84% yield with a diastereomeric ratio of 80\u2009:\u200920.12Since optically active l groups . First, 11 to some optically active N- and O-heterocycles. Sonogashira coupling of 11 with 2-iodophenol proceeded in the presence of Pd(PPh3)4/CuI catalysts, and novel 2-substituted benzofuran 17, which has a chiral quaternary carbon center with substitutions of furan, ester, and carbonate moieties, was obtained in 36% yield . Moreover, a Diels\u2013Alder reaction of the furan moiety of 18a with benzyne gave the corresponding adduct, which, without purification, was treated with HCl/acetic acid to give 19a in 98% yield with a catalyst loading as low as 0.2 mol%. The obtained 8e was then reduced by NaBH4, and compound 20 was obtained in 84% yield. Compound 20 was highly crystalline, and a single recrystallization increased the enantiopurity up to >99% ee. Finally, the 2-methoxyfuran moiety of 20 was oxidized by RuCl3-catalyzed NaIO4-oxidation,21 (0.89 g) was obtained in 89% yield.Since optically active \u03b1-aryl-substituted serines are synthetically useful,8e . Before C2- and C1-symmetric bis(phosphoric acid) catalysts. The conjugated double hydrogen bond network was key to increasing the Br\u00f8nsted acidity and preventing dimerization/deactivation of the catalysts. In particular, we developed a highly enantioselective aza-Friedel\u2013Crafts reaction of 2-methoxyfuran with \u03b1-ketimino esters for the first time. By taking advantage of the highly functionalized products, some transformations to versatile N- and O-heterocycles and \u03b1-aryl-substituted serine with a chiral quaternary carbon center could be achieved. The further application of these catalysts in other asymmetric catalyses is underway.In summary, we have developed chiral BINOL-derived There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Allene reacts with the strongly electrophilic halogenoboranes XB(C6F5)2 (X: Cl or Br) by forming a mixture of 1,3,5-trimethylenecyclohexane and the stoichiometric halogeno-borated tetramerization products. 6F5)2 react with allene to give a mixture of the cyclotrimer 1,3,5-trimethylenecyclohexane (1) and the related halogenoborylated cyclotetramerization products 3a and 3b. Alkyl-substituted allenes were catalytically cyclotrimerized metal-free by XB(C6F5)2 to give cis,trans-2,4,6-trialkyl-1,3,5-trimethylenecyclohexanes under mild conditions.The halogenoboranes XB(C The resulting products contained a halide substituent at one end of the oligoacetylene chain and the B(C6F5)2 functional group at the other.2a and b. We have performed these reactions and here report about their surprising outcome.Allenes serve as important organic building blocks.6F5)2 (2a) in d8-toluene in a Young NMR tube at room temperature. After 7 h reaction time we monitored the NMR features of a mixture that contained the products 1,3,5-trimethylenecyclohexane (1) and the chloroborylated allene tetramer 3a in a ca. 1\u2009:\u20091 ratio (both present in ca. 8 mol% in the mixture) plus unreacted 2a (ca. 10 mol%) and allene (ca. 75 mol%). After 24 h the amount of the pair of allene cyclooligomerization products had almost doubled and there remained only ca. 3 mol% of the chloroborane 2a. That was almost completely consumed after 48 h reaction time at room temperature. The products 1 and 3a were identified spectroscopically from the mixture . Compound 3a shows the typical olefinic exo-methylene pairs of 1H NMR resonances at \u03b4 5.08, 4.84 scale\" fill=\"currentColor\" stroke=\"none\">) and \u03b4 4.63, 4.48 scale\" fill=\"currentColor\" stroke=\"none\">) as well as the AX-spin system of the diastereotopic 3,7-CH2 pairs and the AB pattern of the 5-CH2 at \u03b4 2.58, 2.54. The 1-CH2 group at boron and the 8-CH2 unit give rise to 1H NMR signals at \u03b4 2.18 and \u03b4 2.26, respectively 2 (2b) was carried out analogously. The reaction was directly followed by NMR spectroscopy. It resulted in the formation of the products 1 and 3b in a ca. 1\u2009:\u20092 ratio . Compound 3b was characterized from the mixture by NMR spectroscopy. It shows similar spectra as its chloro-substituted analogue 3a .We prepared compound 3% yield . It was in situ prepared 3b with a slight excess of pyridine gave the adduct 4b, which we isolated in 72% yield as a white solid on a 100 mg scale. The X-ray crystal structure analysis scale\" fill=\"currentColor\" stroke=\"none\">C double bonds annulated at carbon atoms C4 and C6 and it has the CH2\u2013CBr PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 unit, derived from the fourth connected allene unit, attached at the ring carbon atom C2. This carbon atom also bears the CH2\u2013B(C6F5)2 substituent, which has the pyridine donor added to its boron atom. The central six-membered carbocycle of compound 4b features a distorted chair-like ring conformation.Treatment of analysis showed t2Cl2) compound 4b shows the 1H NMR PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 signals of the symmetry equivalent pair of exo-methylene groups at the ring carbons C4 and C6 and the pair of signals of the C9 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 moiety. The C3/C7 CH2 hydrogen atoms are pairwise diastereotopic and the C8 and C1 CH2 groups both show 1H NMR singlets. Compound 4b shows a 11B NMR resonance in the typical tetra-coordinated borane range at \u03b4 \u20131.4 .In solution 2 elimination provides an attractive pathway to the observed product 1,3,5-trimethylenecyclohexane (1). This would in principle constitute a cyclotrimerization of allene catalysed by the XB(C6F5)2 reagents. However, the intramolecular allylboration of 8, giving the other experimentally observed products 3, represents a competing stoichiometric reaction branch that eventually removes the XB(C6F5)2 reagent from the system they react by ring closure12 . Workup with pentane and dichloromethane in this case gave a ca. 79\u2009:\u200921 mixture of compound 12 (characterization see below) and the [tBu3PH+]Cl\u2013 phosphonium salt 11a .Compounds wis base they realosure12 . As a ty3b and tBu3P was carried out similarly . Workup in this case gave the pure compound 12 as a white solid, which we isolated in 65% yield. It was characterized by C, H, N elemental analysis, by spectroscopy and by X-ray diffraction . The X-ray crystal structure analysis shows the newly formed borataspiroundecene framework (tBu3P-substituent attached at the C(9) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC(10) carbon\u2013carbon double bond. The adjacent six-membered ring shows carbon atoms C4 and C6 which serve both as the ring sp2-carbons of the pair of exo-methylene C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 groups.The reaction between the more reactive borane ramework which wa2Cl2) compound 12 shows the typical 1H NMR doublet of the tBu3P-substituent. It features the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH signals of the newly formed internal olefinic moiety at \u03b4 8.21 . The BCH2 group shows up as a 1H NMR signal at \u03b4 1.20 and the C(8)H2 methylene group as a doublet at \u03b4 2.06 (3JPH = 4.5 Hz). The pair of olefinic exomethylene groups of the adjacent carbocyclic six-membered ring shows typical 1H NMR signals at \u03b4 4.61/4.41 and the resonances of the pairwise diastereotopic methylene hydrogen atoms at the C3/C7 pair and at C5 , which we prepared according to a procedure reported by Ma et al.6F5)2 (2a) in d8-toluene solution at 60 \u00b0C. Workup after 48 h reaction time involving purification by chromatography gave the cyclotrimer 14c as the major product scale\" fill=\"currentColor\" stroke=\"none\"> unit shows one 1H NMR resonance, whereas the 3,5-H2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t moieties showed two due to their stereochemically unsymmetrical environment (see the ESI6F5)2 borane is an equally efficient metal-free cyclotrimerization catalyst for the n-octylallene 13c. The catalytic reaction was carried out under analogous conditions and gave the product 14c in 46% yield after workup (some minor byproduct was isolated (ca. 20%) but not positively identified as yet). We performed the XB(C6F5)2 catalysed alkylallene cyclotrimerization reaction for a second example: the reaction of n-dodecylallene (13d) with either of the Cl/BrB(C6F5)2 borane gave the tri-substituted cyclotrimer 14d with cis,trans-attachment of the long chained alkyl groups as the major product. We isolated it as a colorless oil in 40% yield from the ClB(C6F5)2 catalysed reaction [54% with BrB(C6F5)2] (see the ESI14d).We treated product . Compoun6F5)2 serves as an efficient metal-free catalyst for the cyclotrimerization of allene to 1,3,5-trimethylenecyclohexane and of cyclohexylallene to cis,trans-2,4,6-tricyclohexyl-1,3,5-trimethylenecyclohexane.6F5)2 in principle can induce the same catalytic reaction. Both these strongly electrophilic halogeno-boranes serve as catalysts for the cyclotrimerization of long-chain n-alkylallenes 13c,d to give the respective cyclotrimers 14c,d as the major products. Ring-closure and elimination is sufficiently effective to close the catalytic cycle with liberation of the respective XB(C6F5)2 catalyst 2 catalyzed allene cyclotrimerization opens attractive pathways to the synthesis of interesting highly substituted arene products.We have started to use the allene cyclotrimerization products sitylene . We alsoThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Blue-yellow fluorescence\u2013phosphorescence dual emission from single-component white emissive W-CNQDs with a high PLQE of 25% is reported for the first time. Developing efficient single-component white light-emitting diodes (WLEDs) is extremely challenging due to the issue of Kasha's rule. Here we report the first demonstration of blue-yellow fluorescence\u2013phosphorescence dual emission from our newly minted single-component white emissive carbon nitride quantum dots (W-CNQDs). The W-CNQDs deliver an overall photoluminescence quantum efficiency of 25%, which is the highest value among white-emitting materials reported to date, based on utilizing both singlet and triplet states. Experimental and theoretical investigations reveal that the carbonyl groups at the rim of the W-CNQDs play a key role in promoting intersystem crossing and inducing intermolecular electronic coupling, affording intensive yellow phosphorescence. Efficient white emission is achieved with a phosphorescence quantum efficiency of 6% under ambient conditions. A WLED is fabricated by integrating W-CNQD phosphors into a UV-LED chip, which shows favorable white light characteristics with CIE coordinates and a CRI of and 85, respectively, demonstrating good color chromatic stability. This work opens up new opportunities for exploring dual emission mechanisms and designs to facilitate the development of efficient single-component WLEDs. Urea, which is widely used for preparing traditional g-C3N4, was selected as the precursor for synthesizing W-CNQDs.9The emerging carbon quantum dots (CQDs) have recently been demonstrated to be a superior fluorescence\u2013phosphorescence dual emitter for realizing efficient single-component WLEDs.3N4 are comparatively illustrated in 2) at the rim of the W-CNQDs under these mild reaction conditions, which plays a key role in promoting intersystem crossing (ISC) and inducing intermolecular electronic coupling, affording intense yellow phosphorescence.3N4 can be found in ESI .3N4 with its negligible oxygen content scale\" fill=\"currentColor\" stroke=\"none\">N (285.2 eV) and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (288 eV) bonds in the W-CNQDs scale\" fill=\"currentColor\" stroke=\"none\">C (399.5 eV) scale\" fill=\"currentColor\" stroke=\"none\">O scale\" fill=\"currentColor\" stroke=\"none\">C, and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, respectively. Furthermore, solid-state 13C-NMR spectra of the W-CNQDs further confirm that the carbonyl groups from the precursor were successfully produced at the rim of the W-CNQD networks. The clearly observable peak located at 210 ppm is indicative of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond, which fundamentally differs from the negligible resonance signals in the range of 160\u2013220 ppm of the previously reported g-C3N4 scale\" fill=\"currentColor\" stroke=\"none\">C bonds, while no signals from saturated sp3 carbon atoms were observed pattern, demonstrating the typical feature of CNQDs with two peaks resulting from the graphite structure and tri-t Fig. S4, as prevt Fig. S4. The XPSt Fig. S4 reveal t W-CNQDs .12 The N99.5 eV) . The O 1/svg>O .12 The p/svg>O .12 The W4 Fig. S5. And theobserved .13 The a2 \u03c0-conjugation domains and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bonds contained in the W-CNQDs, respectively of W-CNQDs are comparable to their corresponding radiative decay rates (kF = 6.6 \u00d7 107), indicating an efficient ISC process to produce sufficient triplet excitons responsible for the efficient phosphorescence with a \u03a6P of 6% under ambient conditions, which is indeed the highest reported so far, thus enabling efficient white emission. In addition, typically small singlet\u2013triplet energy gaps (\u0394EST < 0.4 eV) are required to facilitate the ISC process in phosphorescence emitters;EST as 0.30 eV, which is far less than that of traditional g-C3N4 (\u0394EST = 0.46 eV) lamp irradiation and yellectively . Fig. 3dectively . The delectively , which r Table S2. The ISC1.000000,.000000 s3N4 for comparison were performed to confirm the mechanism above , which is smaller than those of traditional g-C3N4 , which potentially enables effective ISC from S1 to T1 states of the W-CNQDs based on theoretical calculation is close to the experimental value (\u0394EST = 0.30 eV). Furthermore, for the W-CNQDs, the numbers of energy transition channels (five channels) increased in comparison to traditional g-C3N4 (three channels) , also resulting in enhanced ISC (E1S = 3.4271 eV and E1T = 3.1071 eV) compared with those of traditional g-C3N4 , also enhance the yellow phosphorescence according to the energy gap law. In addition, we analyzed the characters of the excited states using the natural transition orbitals (NTOs)3N4 and increased numbers of energy transition channels (seven channels) in contrast to the isolated W-CNQDs above (five channels), resulting in enhanced ISC 3N4 . It is w T4, T5) , suggest Fig. S11. Indeed,The highly efficient blue-yellow fluorescence\u2013phosphorescence dual emission of W-CNQDs, coupled with their low cost and environmental-friendliness are compelling for their application in high performance single-component WLEDs. Due to the poor solubility of W-CNQDs, a UV-pumped WLED was fabricated for the first time by directly coating W-CNQD phosphor with cyanoacrylate (Super Glue) onto the surface of a commercial 380 nm UV-LED . Efficievia dual emission strategies. We anticipate that further improving the \u03a6P value of yellow phosphorescence emissive CNQDs and red-shifting their emission will lead to greatly improved performance for carbon-based phosphor single-component WLEDs; this research is underway in our laboratory and will be reported in due course.In summary, we report the first successful demonstration of blue-yellow fluorescence\u2013phosphorescence dual emission for single component white light emission with an overall PLQE as high as 25% and a relatively high yellow phosphorescence quantum efficiency of 6% under ambient conditions based on W-CNQDs. The key role of the carbonyl groups at the rim of the large \u03c0-conjugated structure in W-CNQDs has been uncovered, assisting the ISC arising from carbonyl (n\u03c0*) mediated intermolecular (\u03c0\u03c0*) electronic coupling. A WLED was fabricated by integrating W-CNQD phosphors in a UV-LED chip, which showed favorable white light characteristics with CIE coordinates and a CRI of and 85, respectively. This work opens up new opportunities for designing single-component WLEDs There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The twisting of an amide bond provides a new driving force for living ring-opening metathesis polymerization through resonance destabilization. \u20131 of the overall 12.0 kcal mol\u20131 ring strain. The twisted amide polymerization is capable of preparing high molecular weight polymers rapidly at room temperature, and post-polymerization modification combined with 2D NMR spectroscopy confirms a regioirregular polymer microstructure.The living ring-opening metathesis polymerization (ROMP) of an unsaturated twisted amide using the third-generation Grubbs initiator is described. Unlike prior examples of ROMP monomers that rely on angular or steric strain for propagation, this system is driven by resonance destabilization of the amide that arises from geometric constraints of the bicyclic framework. Upon ring-opening, the amide can rotate and rehybridize to give a stabilized and planar conjugated system that promotes living propagation. The absence of other strain elements in the twisted amide is supported by the inability of a carbon analogue of the monomer to polymerize and computational studies that find resonance destabilization accounts for 11.3 kcal mol Ring-strain is a common driving force for chemical reactions in both small molecule and macromolecular synthesis. This is the origin of remarkable carbon\u2013carbon bond cleavage mechanisms of cyclopropane rings,N-to-\u03c0* PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC orbital overlap, twisting hinders this interaction and results in nominal amides with unusual reactivity profiles. Hydrolytic stability and nitrogen basicity of these amides has been directly correlated to the degree of distortion, defined by the twist angle (\u03c4) and nitrogen pyramidalization (\u03c7N) parameters introduced by Winkler and Dunitz,12Twisted amides constitute an unusual class of molecules that have distorted, nonplanar amide N\u2013C(O) bonds as a result of geometric, steric, or electronic effects.1 was explored in HaRP and only resulted in oligomers with broad molecular weight distributions .1 to polymerize under ROMP conditions, the Winkler\u2013Dunitz parameters significantly deviate from planarity.N-to-\u03c0* PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tOC overlap causes the twisted amide to be higher in energy than a planar amide, and it was proposed that 1 would be competent in ROMP through the gain of resonance energy after ring-opening and planarization of the nitrogen atom to an sp2 hybrid (1 using the 3rd generation Grubbs initiator (G3) .1 was prepared following the two-step protocol described by Grigg starting from 2-iodobenzoic acid and tetrahydropyridine.1 was performed with G3 in DCM at room temperature targeting a degree of polymerization (DP) of 100 (ROMPP1 with a number-average molecular weight (Mn) of 15.2 kg mol\u20131 and dispersity (\u00d0) of 1.20. By varying the monomer-initiator ratio, different molecular weights (DP = 10 to 500) were accurately targeted with high monomer conversions and unimodal elution peaks by size-exclusion chromatography (SEC) analysis (\u00d0 = 1.26 and 1.46) implying some secondary metathesis of the backbone olefins occurred, which was supported by experiments at extended reaction times after full conversion was reached is several orders of magnitude lower than the norbornene derivatives commonly used in ROMP (e.g. 63.2 M\u20131 s\u20131 at 25 \u00b0C for exo-butyl norbornene imide).H\u2021 = 84.0 kJ mol\u20131, and entropy of activation \u0394S\u2021 = \u201330.8 J mol\u20131 K\u20131.in situ NMR studies were unable to conclusively demonstrate the coordination state of the chain-end of 100 , entry 4analysis . Higher analysis . A singlehaviour and a liehaviour . To bett2 in which the bridgehead nitrogen of twisted amide 1 is replaced with a methine carbon , no reaction was observed after three hours at room temperature that is consistent with inability of 2 to polymerize. To separate the contribution of resonance destabilization from the overall ring strain in 1, the carbonyl substitution nitrogen atom replacement (COSNAR) method developed by Greenberg was applied.1 and ring-opened amide 3 were calculated to be 8.7 kcal mol\u20131 and 20.0 kcal mol\u20131, respectively . This indicates that resonance destabilization is responsible for over 90% of the ring strain in 1 , further supporting gain of resonance energy as the primary driving force for polymerization.Computational studies were performed at the B3LYP-D3MBJ/6-311++G level of theory to gain more insight into the differences in ring strain between monomers ethylene .21 Analoectively . The 11.1 through HaRP and ROMP should give the same polymer structure. While only oligomers formed under HaRP conditions, slight differences were noted in the 1H NMR spectra of HaRPP1 and ROMPP1 , head-to-head (HH) or tail-to-tail (TT) connectivity , unique signals at 7.0 ppm and 2.7 ppm for 2-P1ROMPH (red highlight), as well as clear differences in the 3.1\u20133.9 ppm and 7.3\u20137.5 ppm regions (ROMPP3 (blue & red) correlated to head-to-tail and tail-to-tail connectivity at the benzylic position, implying indiscriminate ring-opening of the monomer from either side of the olefin showed slightly lower thermal stability of Fig. S19, indicat1 has been described that lacks the angular and steric strain elements traditionally found in ROMP monomers. In contrast, this system leverages resonance destabilization of an amide bond to promote living polymerization to high molecular weights. This is supported by the inability of the bicyclic ketone analogue 2 to polymerize under standard ROMP conditions and computational experiments that highlight the central role of resonance destabilization in the overall monomer ring strain. The microstructure of the resultant polymer ROMPP1 was determined to be regioirregular through hydrogenation experiments coupled to 2D NMR analysis. The monomer orientation had a minimal effect on the glass transition temperature of the polymer but was found to lower overall thermal stability. Future work is underway to design new unsaturated twisted amide structures for ROMP that are promoted by resonance destabilization, as well as exploring applications of this new materials class.The ring-opening metathesis polymerization of the unsaturated twisted amide monomer There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "Acyl(chloro)phosphines RC(O)P(Cl)(t-Bu) have been prepared by formal insertion of tert-butyl phosphinidene (t-Bu\u2013P) from t-BuPA (A = C14H10 or anthracene) into the C\u2013Cl bond of acyl chlorides. t-Bu) have been prepared by formal insertion of tert-butyl phosphinidene (t-Bu\u2013P) from t-BuPA (A = C14H10 or anthracene) into the C\u2013Cl bond of acyl chlorides. We show that the under-explored acyl(chloro)phosphine functional group provides an efficient method to prepare bis(acyl)phosphines, which are important precursors to compounds used industrially as radical polymerization initiators. Experimental and computational investigations into the mechanism of formation of acyl(chloro)phosphines by our synthetic method reveal a pathway in which chloride attacks a phosphonium intermediate and leads to the reductive loss of anthracene from the phosphorus center in a P(v) to P(iii) process. The synthetic applicability of the acyl(chloro)phosphine functional group has been demonstrated by reduction to an acylphosphide anion, which can in turn be treated with an acyl chloride to furnish dissymmetric bis(acyl)phosphines.Acyl(chloro)phosphines RC(O)P(Cl)( Collectively, these data support the formulation of 1 as (tert-butylchlorophosphanyl)(phenyl)methanone, PCl(t-Bu)(C(O)Ph).Treatment of at 23 \u00b0C led to a1 could not be isolated as single crystals suitable for structural analysis, a transition metal complex of this phosphine was prepared. Treatment of 1 with half an equivalent of [Ru(p-cymene)Cl2]2 in tetrahydrofuran led to the formation of coordination complex 2. Layering the reaction mixture with pentane at 23 \u00b0C gave 2 as a red-orange crystalline material in 77% yield. Multinuclear NMR spectroscopy studies, in addition to a single crystal X-ray diffraction study confirmed the formulation of 2 as Ru(p-cymene)Cl2(PCl(t-Bu)(C(O)Ph)) , 1.875(4) and 2.3178(8) \u00c5 respectively, which are in line with the expected values.iii) ligands.As C(O)Ph)) . RacemicA compound is not \u03c0-donating.via nucleophilic attack by phosphorus at the electrophilic carbonyl group of benzoyl chloride. We envisioned that replacement of the chloride for a less nucleophilic anion may lead to the isolation of the putative cationic acylphosphonium intermediate. To this end, the reaction of equimolar solutions of t-BuPA and benzoyl triflate (PhC(O)OTf, OTf = CF3SO3\u2013)3[OTf] scale\" fill=\"currentColor\" stroke=\"none\">O absorption peak at 1636 cm\u20131. These data are consistent with the formulation of 3[OTf] as [AP(t-Bu)(C(O)Ph)][OTf].Previous studies on thermal phosphinidene transfer have established that thermal loss of a phosphinidene does not occur when the R-group of an RP\u2013)3[OTf] as a whi3[OTf] decomposes slowly in solution at ambient temperature, yielding an anthracenyl(acyl)hydridophosphonium triflate salt as the major product in chloroform at 23 \u00b0C quantitatively generated 1, [TBA][OTf] and anthracene product has previously been described in the literature.I2, see ESI3 and is the formal reverse of the McCormack reaction.I2 to be 65.0 kcal mol\u20131 which is significantly higher than either TS1 of TS2, ostensibly ruling it out as an intermediate in the reaction mechanism as determined by DFT calculations.The higher Gibbs free energy of the first transition state compared to the second is consistent with experiment, where a phosphonium intermediate is not observed when benzoyl chloride is used as the acylating reagent. Thus it is indicated that, when switching from chloride to triflate, there is a change in the rate determining step from 1 were undertaken by reduction of the P\u2013Cl bond. Treatment of compound 1 with 2 equivalents of freshly-prepared sodium naphthalenide4 as a crystalline orange powder in 49% yield. The connectivity of anion 4 as [OC(Ph)Pt-Bu]\u2013 was confirmed by a single crystal X-ray diffraction experiment scale\" fill=\"currentColor\" stroke=\"none\">O) orbital.Efforts to further derivatise periment . In the 4a, 4b, To quantify the degree of electron delocalization over the acylphosphide functional group, the electronic structure was evaluated using natural bond orbital (NBO) methods.4 and AdC(O)Cl (Ad = 1-adamantyl) in tetrahydrofuran generated 5, which was isolated as a crystalline yellow solid in 55% yield and 214 ppm (JPC = 46 Hz), which are assigned to the two acyl carbon atoms. The IR spectrum of 5 shows two C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO absorption peaks at 1665 and 1629 cm\u20131. These spectroscopic data inform our formulation of 5 as OC(Ph)P(C(O)Ad)t-Bu. Single crystals of 5 were grown from a concentrated pentane solution and analyzed by an X-ray diffraction study, which featured 5 as a single (R)-enantiomer (see ESIP21 (The combination of [Na(15-crown-5)]5% yield . In the r see ESI in the ce ESIP21 .5 from [Na(15-crown-5)]4 provides an approach for preparing dissymmetric bis(acyl)phosphines.5) P-protected acylphosphide anion describes C\u2013O instead of C\u2013P bond formation upon treatment with an acyl chloride, to give an ester-containing phosphaalkene.57The formation of t-BuPA with acyl chlorides to give acyl(chloro)phosphine-containing products, which were not accessible previously.In summary, we have described a novel reaction of There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Reaction of [3-N2-o-C2B10H11][BF4] with various kinds of nucleophiles gives a very broad spectrum of cage B(3)-substituted o-carborane derivatives, 3-X-o-C2B10H11 2, etc.), and serves as a simple and efficient method for multiple functionalization of o-carborane. o-carborane is described. Reaction of [3-N2-o-C2B10H11][BF4] with various kinds of nucleophiles gave a very broad spectrum of cage B(3)-substituted o-carborane derivatives, 3-X-o-C2B10H11 2, etc). This reaction may serve as another efficient [18F]-radiolabeling method of carborane clusters for positron emission tomography applications.A simple and efficient method for selective cage B(3) multiple functionalization of Carboranes, 3-dimensional relatives of benzenes, are a class of boron hydride clusters in which one or more BH vertices are replaced by CH units.2+X\u2013) constitute an important group of intermediates that have found wide applications in organic synthesis.o-carboranyl diazonium salts are non-isolable, can only be prepared in situ and undergo substitution reactions with the reaction solvent, usually inorganic acids, in the presence of copper salts.o-carboranyl diazonium salt, [3-N2-o-C2B10H11][BF4].o-carborane12Diazonium compounds -arylation of o-carborane can be achieved via the aromatic ene reaction of 1,3-dehydro-o-carborane or a visible-light mediated B\u2013C(sp2) coupling of a carboranyl boron-centered radical. However, the substrate scope is only limited to arenes.On the other hand, it has been reported that B(9)-carboranyl iodonium salt can react with nucleophiles.o-carboranes was prepared in 77% isolated yield, by treatment of 3-amino-o-carborane with 1.5 equivalents of nitrosonium tetrafluoroborate.1 is dependent upon the counterions used and BF4\u2013 offers the highest thermal stability of the salt among the anions examined, such as PF6\u2013 and Cl\u2013. A 1.0 g batch of carboranyl diazonium salt 1 stored at \u20135 \u00b0C showed no signs of decomposition over four months.3-Diazonium-1 reacted rapidly with various nucleophiles (2) in acetonitrile, providing the corresponding B(3)-substituted o-carboranes in good to excellent yields nucleophiles, such as halide ions, gave the corresponding halogenated carboranes in excellent yields in <5 min -functionalized o-carboranes 3\u201314 -substituted o-carboranes in moderate to good yields bonds. More importantly, various functional groups that were previously unable to be introduced into the carborane unit can now be installed in a very simple and efficient manner. For instance, common functional groups can be easily installed on the 17 were produced in 81\u201398% yield scale\" fill=\"currentColor\" stroke=\"none\">O and S PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO double bonds was also examined. For example, the reaction of dimethyl sulfoxide furnished compound 20 after hydrolysis -oxygenated carboranes 1H, 13C, and 11B NMR spectroscopy as well as HRMS spectrometry.All new compounds were fully characterized by 4 and 6 were further confirmed by single-crystal X-ray analyses.17The molecular structures of compounds 1 did not react with anhydrous ether position, was formed quantitatively (vide infra).Interestingly, precursor N1 type of mechanism carboranes are promising radiotracers in Positron Emission Tomography (PET). Previously, 18[F]-fluorination of o-carborane was achieved by nucleophilic substitution of a B(9)-carboranyl iodonium bromide.1 as the starting material. Under similar reaction conditions to those reported in the literature,3a was formed quantitatively within 1 min and it can be easily purified (eqn (5)).The present strategy provides a straightforward and practical access to cage boron functionalized o-carborane has been developed. By utilizing B-carboranyl diazonium salt as a synthon, a large class of o-carborane derivatives bearing previously inaccessible functional groups can now be efficiently prepared, which may find applications in materials sciences.A practical method for selective cage boron functionalization of o-carborane,o-carboranes.This work demonstrates that B-carboranyl diazonium salt can serve not only as a source of boron-centered radicals18F-labelled o-carborane derivatives for medical applications.21Compared to aryl diazonium salts, the exceptionally high reactivity of B-carboranyl diazonium salt may be due to the lack of conjugation between the carborane cage and the diazonium group. Such a method may find useful applications in the efficient and fast synthesis of Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Head-to-tail peptide macrocyclisations are significantly improved, as measured by isolated yields, reaction rates and product distribution, by substitution of one of the backbone amide C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds with an oxetane ring. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds with an oxetane ring. The cyclisation precursors are easily made by standard solution- or solid-phase peptide synthesis techniques. Macrocyclisations across a range of challenging ring sizes are enabled by incorporation of this turn-inducing element. Oxetane incorporation is shown to be superior to other established amino acid modifications such as N-methylation. The positional dependence of the modification on cyclisation efficiency is mapped using a cyclic peptide of sequence LAGAY. We provide the first direct experimental evidence that oxetane modification induces a turn in linear peptide backbones, through the observation of dNN and d\u03b1N NOEs, which offers an explanation for these improvements. For cyclic peptide, cLAGAY, a combination of NMR derived distance restraints and molecular dynamics simulations are used to show that this modification alters the backbone conformation in proximity to the oxetane, with the flexibility of the ring reduced and a new intramolecular H-bond established. Finally, we incorporated an oxetane into a cyclic pentapeptide inhibitor of Aminopeptidase N, a transmembrane metalloprotease overexpressed on the surface of cancer cells. The inhibitor, cCNGRC, displayed similar IC50 values in the presence or absence of an oxetane at the glycine residue, indicating that bioactivity is fully retained upon amide C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond replacement.Cyclic peptides are an important source of new drugs but are challenging to produce synthetically. We show that head-to-tail peptide macrocyclisations are greatly improved, as measured by isolated yields, reaction rates and product distribution, by substitution of one of the backbone amide C Many of the substrates were made in solution using Bn ester/Z-protection of the C- and N-termini to allow the synthesis of salt-free precursors by use of a final hydrogenolysis step. This enabled accurate comparisons in product yields to be made across different substrates without having to correct for the impact of salts on the cyclisations. The synthesis of oxetane modified peptides was also achieved using the more practical approach of solid-phase peptide synthesis (SPPS). In most cases, control peptides without the oxetane modification were made for comparison purposes see ESI.in situ coupling of the resulting amine to the next protected amino acid, preactivated as its succinyl ester.1 conjugate addition of the N-terminus of the growing peptide to 3-(nitromethylene)oxetane; (ii) nitro group reduction and ester.1 . Alternater.1 and corresponding oxetane modified WLGOxG (7) (where GOx = oxetane modified glycine) were undertaken. For this investigation, substrates containing a tryptophan residue were used to allow quantitative monitoring by UV spectroscopy. Both substrates were subjected to the DEPBT method and conversions monitored over 74 h. From these data, it is clear that the initial rate of formation of oxetane containing cyclic peptide 9 is considerably faster than 8, even though both linear precursors 6 and 7 are consumed at similar rates . In a striking illustration of the power of this new method, cyclisation to tetrapeptide 10 was achieved in 54% yield in the presence of the oxetane modification, however cyclodimerisation to octapeptide was the predominant reaction pathway (20%) for the unmodified system. The successful formation of 12 containing an alanine modified residue confirms that this methodology is not simply limited to glycine substitution. Generally, DEPBT was favoured as the activating agent as it gave efficient cyclisations and minimised formation of difficult to separate diastereomers arising from epimerisation at the C-terminus prior to cyclisation. In some instances, impurities derived from the DEPBT reagent proved hard to remove, in which case PyBOP was used as an alternative.To test the generality of these initial findings, the head-to-tail cyclisation of a variety of oxetane modified substrates was studied and the isolated yields compared with those for the unmodified systems . Oxetane18 in an impressive 39% yield from commercial H-Trp(Boc)-2-ClTrt (15) . First, approach and ESI\u20202, whose synthesis was described in 22 after reverse-phase HPLC purification. Importantly, the four-membered oxetane ring survives the strongly acid conditions required to globally deprotect the side-chains including the arginine Pbf group. Smaller 11- and 14-membered macrocycles 23 and 24 were also conveniently produced in good yields using this methodology.Macrocyclisations not involving head-to-tail ring closure have also been examined. Specifically, the formation of disulphide containing macrocycles through oxidative cyclisation of cysteine side chains has been explored . TreatmeN-Methyl glycine, 2-methylalanine (Aib), ethylenediamine, dimethylethylenediamine and \u03b2-alanine were all introduced in place of the glycine introducing a potentially beneficial Thorpe\u2013Ingold effect. In fact, only the oxetane modification led to marked improvement in isolated yield of the derived cyclic peptides, suggesting that oxetane introduction is particularly beneficial.To understand how significant these improvements are in the broader context of peptide macrocyclisation, a series of alternative modifications were made to the central G residue of LAGAY and the efficiencies of the ring closures compared. glycine . These m13 by formation of all four possible amide bonds was examined to see whether the location of the oxetane relative to the amide bond being formed is important scale\" fill=\"currentColor\" stroke=\"none\">O system leading to higher product yields. However, larger improvements are seen when the modification is more centrally located along the precursor backbone.Macrocyclisation to pentapeptide mportant . The yie1H\u20131H TOCSY and NOESY spectra were acquired as detailed in the ESI1H signals in both peptides and probe changes in conformation, especially near the site of modification. As shown in i.e. residue i to residue i + 1) and medium-range NOEs that are commonly observed in \u03b1-helices, \u03b2-sheets, and turns.d\u03b1N, dNN, d\u03b2N), medium-range NOEs are only observed in peptide LAGOxAY-OMe containing the modification. Specifically, dNN and d\u03b1N NOEs are clearly observed in the oxetane modified peptide between residues Gly3 and Tyr5 indicating their close proximity, data consistent with the formation of a turn. These NMR studies provide the first direct experimental evidence that the oxetane modification is indeed turn-inducing, and brings the peptide termini closer in space to facilitate efficient cyclisation and cLAGOxAY (13) in DMSO. 2D 1H\u20131H NOESY spectra were used to compile a set of nuclear Overhauser enhancement (NOE) \u2013 derived experimental distance restraints that were incorporated into MD simulations using the CHARMM forcefieldTo gain insights into how oxetane modification impacts the structure of the derived cyclic peptides, molecular dynamics (MD) computer simulations with distance restraints derived from NMR experiments were carried out on cLAGAY , are presented in 13 explores less of the \u03a6/\u03c6 space than 25, which supports our observation above that 13 is more rigid. The Ramachandran plots also highlight the effect of the oxetane introduction on the structure of the residues in proximity to the modification, with Gly3, Ala4 and Tyr5 shifting to different regions of \u03a6/\u03c6 space following the introduction of the oxetane, which is in agreement with the visual representation of the backbone in Cluster analysis was performed on 12\u2009500 structures extracted from the trajectories at 40 ps intervals. Five and four distinct structures were found for peptides y see ESI. Ten repAla4 see . The bac26) is known to target Aminopeptidase N (APN), a transmembrane zinc-dependent metalloprotease involved in a variety of processes, including blood pressure regulation, cell migration, viral uptake, cell survival, and angiogenesis.22 and cCNGRC (26) were examined for their inhibitory activity towards porcine APN using a spectrophotometric assay oxetane, or alternatively through coupling preformed Fmoc-protected dipeptide building blocks containing this modification. The first is convenient for the insertion of glycine modifications, whereas the second is more general, being suitable for introduction of oxetane modified derivatives of other l-amino acids was demonstrated. It can also be applied to side-chain to side-chain macrocyclisations, specifically oxidative ring closure of cysteine residues by disulphide bond formation. As a tool to improve head-to-tail macrocyclisations, our evidence suggests that oxetane incorporation is superior to a number of other common backbone modifications. Importantly, OMCPs are compatible with the harsh acidic conditions needed to deprotect amino acid side chains.Oxetane incorporation led to improvements in all the head-to-tail cyclisations studied as assessed by isolated yields, reaction rates and analysis of product distributions. The method works across a range of ring sizes and enabled the synthesis of a range of cyclic tetra-, penta-, hexa- and heptapeptides. Major improvements in yields are seen using glycine modified residues, with levels of epimerisation and dimerisation significantly reduced. The extension of this method to other modified dNN and d\u03b1N NOEs. The formation of a turn presumably helps bring the termini closer together enabling the macrocyclisation.A key question we sought to address in this study was why does oxetane introduction improve macrocyclisations? For maximum benefit, we have shown that the oxetane is best located centrally along the peptide backbone, an observation consistent with the hypothesis that this modification is turn-inducing.13. The full retention of bioactivity of 22 relative to cCNGRC suggests that the replacement of a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO amide bond by an oxetane ring has little impact on binding, making it a viable bioisosteric replacement. Next steps will involve a fuller assessment of the properties of OMCPs and their application in drug discovery programmes.To be useful in drug discovery programmes as well as being easy to make, OMCPs must also have useful properties. Intuitively, one might expect oxetane introduction to only alter the backbone configuration of the cyclic peptide close to the site of modification. Indeed, this was borne out in detailed NOE-restrained MD simulations conducted on There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "We introduce a modular synthetic procedure to produce a new class of synthetic oligomers called peptidines composed of repeating di-substituted glycine-derived amidines. N-alkyl glycine oligomers is replaced with a functionalized N-atom. Compared to peptoids or peptides, the presence of this amidine N-substituent in peptidines effectively doubles the number of diversification sites per monomeric unit, and can decrease their overall conformational flexibility. We have developed iterative solution- and solid-phase protocols for the straightforward assembly of peptidines containing diverse backbone and amidine substituents, derived from readily available primary and secondary amines. We have also performed crystallographic and computational studies, which demonstrate a strong preference for the trans (E) amidine geometry. Given their straightforward synthetic preparation and high functional group density, peptidines have the potential to serve as useful tools for library generation, peptide mimicry, and the identification of biologically active small molecules.Efforts to emulate biological oligomers have given rise to a host of useful technologies, ranging from solid-phase peptide and nucleic acid synthesis to various peptidomimetic platforms. Herein we introduce a novel class of peptide-like oligomers called \u201cpeptidines\u201d wherein each carbonyl O-atom within poly- Oligomer-based synthesis is central to all known life processes. In particular, the structural and functional variety found in proteins is derived from the assembly of only 20 amino acid building blocks. Efforts to emulate this diversity have led to a range of oligomer-based peptidomimetic strategies, including oligopeptides, peptoids, peptidosulfonamides, sulfonylpeptides, polypyrroles and others. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, with C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR thus doubling the accessible diversity for a given oligomer length. By varying the size and electronics of amidine N1 (backbone) and N2 (amidino) substituents, one can also modulate N-lone pair basicity, and backbone geometry.Herein we introduce a new class of oligomeric scaffolds that we term \u201cpeptidines\u201d. Peptidines are oligomers composed of repeating di-substituted glycine-derived amidines . AlthougN1 and N2 substituents to derive modularly from the large pool of commercially available primary amines. Using this route, we have been able to produce peptidines ranging in size from 2- to 4-mers, appended with sterically and electronically diverse substituents at both N1 and N2 positions. These syntheses proceed in short order, and with excellent yields in both solution and solid phases. Crystallographic and computational studies have demonstrated that amidines present within the peptidine scaffold prefer the trans-(E) geometry of the N1 substituent with respect to the N2 nitrogen. Peptidines therefore adopt discrete conformations as a function of both H-bonding effects and non-bonding interactions. In light of their facile preparation and high potential for chemical conformational diversification, we envision that peptidines will provide a useful scaffold for the preparation of novel and diverse structures with a range of chemical and biological applications.Thus, we have developed a concise peptidine synthesis protocol that allows both 1) with an imidoyl chloride (2) to produce an \u03b1-chloro amidine (3); second is an amination step (reaction 2), wherein the chloride atom in 3 is displaced by a primary amine (4) to form an \u03b1-amino amidine (5). Iteration of reactions 1 and 2 affords peptidine oligomers (6). In turn, the \u03b1-chloro imidoyl chlorides (2) used in reaction 1 are generated from commercially available primary amines (7), which are acylated to produce chloroamides (8), and then chlorinated to form imidoyl chlorides (2) (Our strategy for preparing peptidines is outlined in ides (2) .8a\u2013i) to the corresponding imidoyl chlorides successfully afforded sulfonyl- (3a\u2013d), aryl (3e\u2013f), carbamoyl-, and urea-derived (3g\u2013h) amidines. These yields were universally high (>70%) throughout a range of N2-substituents and as expected, reactions with sulfonamides proceeded faster (14 h versus 2 h), and in higher yields, than aryl and acyl derivatives. Furthermore, despite the possibility for reaction at the alkyl chloride position, we observed complete chemoselectivity for displacement at the acylimino carbon for all substrates examined, with no evidence of double addition. Similar chemoselectivities have been observed previously in condensation reactions between bis-electrophiles such as \u03b1-chloro-acid chlorides and secondary amines.2i did appear to provide the corresponding \u03b1-chloro-amidine (3i) following diisopropylamine treatment, attempts to purify this compound were hampered by the presence of inseparable amounts of diisopropylammonium chloride and diisopropylamine. However, by carrying out the chlorination reaction at room temperature to avoid decomposition (likely via polymerization), followed by trapping with diethylamine, we were able to access alkyl amidine 37 , we next focused our efforts on displacing the pendant chloride with amine nucleophiles (5a\u2013h) in excellent yields.p-nitrophenyl (entry 5) derivatives to give \u03b1-amino amidines (5a\u2013e) in near quantitative yields. Interestingly, the phenyl derivative 5f was found to decompose rapidly as the free base, however addition of hydrochloric acid in ether to this compound immediately after silica gel purification facilitated its isolation as the stable HCl salt. Furthermore, the reaction of 3h with benzylamine produced cyclic amidine 5h . Taken together, these results confirm that the peptidine core can be constructed through a three-step procedure involving: (1) amide chlorination, (2) amidination of a secondary amine, and (3) \u03b1-halide displacement with a primary or secondary amine.We next analyzed how varying the structure of the amine nucleophile would affect the chloride displacement process using substrate 5b, and using imidoyl chloride 2b and benzylamine as nucleophile, we were able to access 2-mers 10 and 11, and 3-mer 12 in only three steps and 80% overall yield by simply repeating chloride displacement and amidination steps. Notably, none of these transformations proceeded in lower than 90% yield. Furthermore, using this protocol, we have been able to prepare 12 in quantities greater than 1 g demonstrating the scalability of this procedure.Our next goal was to iterate the above three-step sequence to access longer oligomeric peptidines. We therefore chose to target a simple 3-mer composed of identical repeating monomeric units . Startin12 into longer oligomers gave rise to several notable findings. For example, treatment of 12 with benzylamine led exclusively to cyclic product 13 -methylbenzylamine afforded no cyclic product upon reaction with 12, but instead exclusively provided the expected linear product 14 (S)-methylbenzylamine provides sufficient steric encumbrance to prevent internal cyclization. Switching the nucleophile to Bn2NH provided linear 3-mer 15. We also succeeded in producing a linear 4-mer peptidine (16) via our two-step elongation protocol . These results demonstrate that by regulating the steric environment around backbone N1 substituents, we can access both linear and cyclic peptidines.Efforts to advance 3-mer oduct 13 , entry 1oduct 14 , entry 2protocol , entry 438) to the corresponding cyclohexylamine derivative to the synthesis of peptidines containing between one and four monomeric units .Given the suitability of oligomer-based synthetic strategies for the preparation of one-bead-one-compound libraries,ic units . After oe.g.12 \u2192 13, 24\u201326. Upon resin cleavage, however, linear intermediates underwent rapid cyclization. Compound 27 is an example of such a situation, and was initially observed as a mixture with its uncyclized counterpart 43 , and provided 228 mg of pure product, demonstrating the scalability of our solid-phase platform. N2-carbamoyl and carbonyl substituents could also be incorporated into our solid-phase platform ; however, as observed in analogous solution phase experiments, N2-carbamate derivative 34 readily underwent intramolecular cyclization to give an imidazolone substructure, similar to compound 5h. Amines containing acid-labile side-chain protecting groups, similar to those employed in Fmoc SPPS , were readily incorporated into peptidines, and unmasked after resin cleavage to give carboxylate and amine functional groups (as demonstrated by the synthesis of 35). Employing homo-\u03b2-alanine as the C-terminal group allowed us to access 2-mer 36 in good yield and purity tended to exhibit broadened peaks in 1H and 13C NMR spectra during routine characterization. This phenomenon was not surprising, as other oligomeric scaffolds, such as peptoids, can be very flexible and often exist in multiple different conformations at room temperature.12 demonstrated peak sharpening with increasing temperatures interacts with atoms at both termini of the molecule. Additionally, a hydrogen bond between the terminal ammonium N\u2013H group and the adjacent sulfonamide oxygen atom , psi (\u03c8), and omega (\u03c9) (\u03c4), referring to the position of the N2-substituent relative to the N1-nitrogen (\u03c4 angles exist in a trans conformation (\u03c4 = 180\u00b0 \u00b1 15\u00b0), despite each being in a different steric environment. This observation is consistent with previous literature reports,\u03c9 angles in 28, on the other hand, proved slightly more variable, demonstrating a preference for either cis or trans conformations , reminiscent of disubstituted amides found in peptides and peptoids.\u03c9 \u2248 180\u00b0 or 0\u00b0; \u03c4 \u2248 180\u00b0), there is a high degree of co-planarity surrounding each amidine in 28 . Additionitrogen . Perhapsne in 28 . The mosN2-substituent to prefer the trans geometry (\u03c4 = 180\u00b0 \u00b1 15\u00b0), we performed quantum chemical energy calculations and amidine (N2) nitrogen atoms. Also, we have obtained a crystal structure of 3-mer 28, which demonstrates all amidine motifs to adopt a trans geometry about the \u03c4 angle. This geometry conforms to structural constraints predicted by computational studies, and suggests that peptidines have the potential to project functionality in an ordered array. Furthermore, because peptidines possess two sites of diversity per monomeric unit (as opposed to only one present in peptides and peptoids), they may prove useful for library generation as greater diversity could be generated with shorter length oligomers. Peptidines therefore have significant potential to serve as useful tools for small molecule synthesis, peptidomimicry, and library generation.Herein we have introduced a novel class of glycine-amidine-based oligomers, which we term \u201cpeptidines\u201d readily afforded through modular synthetic approaches using both solid and solution phase chemistry. These synthetic protocols are high yielding, readily scalable, and enable straightforward installation of a variety of substituents onto backbone (Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Palladium-catalyzed direct intermolecular coupling of o-carboranes with alkynyl bromides or terminal alkynes has been achieved, for the first time, with the help of a traceless directing group \u2013COOH, leading to the synthesis of a series of new cage B(4)-alkynylated-o-carboranes in high yields with excellent regioselectivity. o-carboranes has been achieved for the first time using two different catalytic systems. In the presence of 5 mol% Pd(OAc)2 and 3 equiv. of AgOAc, the reaction of 1-COOH-2-R1-C2B10H10 with R3SiC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr in ClCH2CH2Cl gives 4- scale\" fill=\"currentColor\" stroke=\"none\">C)-2-R1-o-C2B10H10 in moderate to high yields. This reaction is compatible with alkynes possessing sterically bulky silyl groups such as iPr3Si or tBuMe2Si. Meanwhile, another catalytic system of Pd(OAc)2/AgOAc/K2HPO4 can catalyze the direct B(4)-alkynylation of 1-COOH-2-R1-C2B10H10 with terminal alkynes R2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH in moderate to high yields. The latter has a broader substrate scope from bulky silyl to aromatic to carboranyl substituents. Desilylation of the resultant products affords carboranyl acetylene 4- scale\" fill=\"currentColor\" stroke=\"none\">C)-2-R1-o-C2B10H10 which can undergo further transformations such as Sonogashira coupling, dimerization and click reactions. It is suggested that the above two catalytic systems may proceed via Pd(ii)\u2013Pd(iv)\u2013Pd(ii) and Pd(ii)\u2013Pd(0)\u2013Pd(ii) catalytic cycles, respectively. In addition, the silver salt is found to promote the decarboxylation reaction and thereby controls the mono-selectivity.Pd-catalyzed carboxylic acid guided regioselective alkynylation of cage B(4)\u2013H bonds in The development of efficient synthetic methodologies to incorporate alkyne motifs has received broad interest, as they are not only important building blocks in natural products, pharmaceuticals and materialso-carborane, followed by Pd(0)-catalyzed cross-coupling with alkynyl Grignard reagents,via cage B\u2013H activation.Though cage boron alkynylated carboranes can be prepared by two-step reactions, such as the selective iodination of an o-carboranes is very rare.23Directing groups are essential in transition metal catalyzed C\u2013H activation due to their ability to chelate the metal catalyst, position it for selective C\u2013H cleavage, and reduce activation energy by stabilizing the metallacycle intermediates.o-carboranes, in which the carboxyl group is removed in a one-pot fashion. Inspired by these results and other cage B\u2013H activation reactions,ii)\u2013Pd(iv)\u2013Pd(ii) catalytic cycle and by terminal alkynes via a Pd(ii)\u2013Pd(0)\u2013Pd(ii) catalytic cycle. These new findings are reported in this article with iPr3SiC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr in the presence of 10 mol% Pd(OAc)2 and 1 equiv. of AgOAc in toluene at 90 \u00b0C for 6 h did not give any of the desired product scale\" fill=\"currentColor\" stroke=\"none\">C)-2-CH3-o-C2B10H10 in 40% GC yield were examined under the chosen optimal reaction conditions, and the results are compiled in 3 in high isolated yields afforded the product 3l in 54% yield gave 3k in only 40% isolated yield , the scope of R2 is highly limited in such a coupling reaction. tBuMe2SiC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr worked well to give 3p in 70% isolated yield scale\" fill=\"currentColor\" stroke=\"none\">CBr was not reactive, probably due to its propensity to coordinate with a Pd center via the \u03c0 bond scale\" fill=\"currentColor\" stroke=\"none\">CBr as reagents. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr and tBuC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr were not compatible with this reaction.In contrast to R3-o-C2B10H10 (1a) with iPr3SiC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH under the aforementioned optimal reaction conditions. No reaction was observed in the absence of a base scale\" fill=\"currentColor\" stroke=\"none\">C\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCiPr3Si as the side product scale\" fill=\"currentColor\" stroke=\"none\">CH was added slowly via a syringe pump, leading to a significantly increased yield of 3a to 56% GC yield . The results are compiled in 1 = alkyl groups, the isolated yields of 3 are comparable to those observed in 1 = aryl unit such as 1g, the isolated yield of 3g is 30% and 1o (R1 = Me3Si) give 3n in 35% and 74% yields, respectively 2C6H3, 2-iPrC6H4 to 1-nC6H13-o-C2B10H10, affording the corresponding products, 3s, 3t, 3u and 3v, in 65%, 73%, 80% and 82% isolated yields, respectively to afford quantitatively the terminal alkyne 4a in 84% isolated yield. A click reaction of 4a with phenyl azide afforded carborane-functionalized 1,2,3-triazole (7a) in 95% isolated yield.To demonstrate the applications of the resultant compounds lkyne 4a . Like ot3 and 4a\u20137a were fully characterized by 1H, 13C, and 11B NMR spectroscopy as well as high-resolution mass spectrometry (HRMS).4a and 6a were further confirmed by single-crystal X-ray analyses and are shown in All new compounds 1a was treated with 1 equiv. of iPr3SiC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr in the presence of 20 mol% Pd(dba)2 (dba = dibenzylideneacetone) in DCE at 90 \u00b0C for 6 h in the absence of AgOAc. On the other hand, under the same reaction conditions, replacement of Pd(dba)2 with Pd(OAc)2 gave the alkynylation product 3a in 30% GC yield scale\" fill=\"currentColor\" stroke=\"none\">CH afforded 3a in 16% GC yield without AgOAc as the oxidant. While, no 3a was observed when 20 mol% Pd(dba)2 was used instead of Pd(OAc)2 (ii) not Pd(0).To gain some insight into the reaction mechanism, the following control experiments were carried out. No reaction was observed if GC yield . SimilarPd(OAc)2 . These r1b and 3b\u2013COOH) was also examined site can induce the decarboxylation, and the addition of a silver salt can accelerate such decarboxylation, which is crucial for controlling the mono-selectivity.Decarboxylation of carboranyl carboxylic acids (examined . Compounii)\u2013Pd(iv)\u2013Pd(ii) catalytic cycle: an exchange reaction of 1 with Pd(OAc)2, followed by regioselective electrophilic attack at the more electron-rich cage B(4) site yields the intermediate A as the charge distribution on the cage follows the trend B > B > B > B.2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCBr affords a Pd(iv) intermediate B.C, which undergoes a salt metathesis reaction, protonation and decarboxylation to give the final product 3 and regenerates the catalyst Pd(OAc)2. Meanwhile, another catalytic system involves a Pd(ii)\u2013Pd(0)\u2013Pd(ii) cycle. An acid\u2013base reaction between K2HPO4 and carboranyl carboxylic acid 1 gives the potassium salt 1\u2032.1\u2032 to the Pd(ii) center, followed by subsequent regioselective electrophilic attack at the more electron-rich cage B(4) site generates the intermediate D. Ligand exchange by acetylide gives a carboranyl-palladium acetylide intermediate E.F and Pd(0). Decarboxylation of F results in the formation of the final product 3, meanwhile Pd(0) is oxidized by AgOAc to regenerate Pd(OAc)2. It is noted that AgOAc acts as a bromide captor in the Pd(ii)\u2013Pd(iv)\u2013Pd(ii) catalytic cycle, but as an oxidant to regenerate Pd(ii) from Pd(0) in the Pd(ii)\u2013Pd(0)\u2013Pd(ii) catalytic cycle. However, in both cross-coupling reactions, AgOAc plays a crucial role in promoting decarboxylation and thereby controlling the mono-selectivity.On the basis of the aforementioned experimental data, two plausible reaction mechanisms are proposed in o-carboranes using alkynyl bromides or terminal alkynes as alkynylating agents, where \u2013COOH acts as a traceless directing group. A series of new cage B(4)-alkynylated o-carborane derivatives has been prepared for the first time, which could find many applications in the synthesis of carborane-based materials.We have developed two catalytic systems for regioselective and efficient alkynylation of cage B(4)\u2013H bonds in ii)\u2013Pd(iv)\u2013Pd(ii) cycle for using alkynyl bromides as coupling agents and a Pd(ii)\u2013Pd(0)\u2013Pd(ii) cycle for employing terminal alkynes as coupling partners. The latter has a broader substrate scope than the former. This work also gives some hints for the development of new catalytic systems for the functionalization of carboranes.On the basis of control experiments and literature work, two catalytic cycles are proposed for the above two reactions: a Pd(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We have developed a simple and versatile strategy for in situ growth of MnO2 on the surfaces of oleic acid-capped upconversion nanoparticles by optimizing the component concentrations in the Lemieux\u2013von Rudloff reagent. in situ growth of MnO2 on the surfaces of oleic acid-capped hydrophobic upconversion nanoparticles (UCNPs) by optimizing the component concentrations in the Lemieux\u2013von Rudloff reagent. The oxidation time was shortened by a factor of two compared to that of the reported method. This oxidation process has no obvious adverse effects on the phases of UCNPs. STEM, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and energy-dispersive X-ray analysis (EDX) characterization demonstrated the successful growth of MnO2 on the surfaces of UCNPs. Furthermore, when the weight ratio of MnO2/UCNPs reached (147.61 \u00b1 17.63) \u03bcg mg\u20131, 50% of the initial upconversion luminescence of UCNPs was quenched, as revealed by fluorescence and inductively coupled plasma optical emission spectrometry (ICP-OES) results. The presence of the surface MnO2 precipitate not only confers high dispersity of UCNPs in water, but also allows further activatable magnetic resonance imaging (MRI) and fluorescence multimodal imaging after reduction to Mn2+ by intracellular glutathione (GSH). A novel targeted drug carrier nanosystem was prepared to protect MnO2 from early decomposition in blood circulation by coating with mesoporous silica and capping with a gelatin nanolayer. Aptamer sgc8 was then attached to the surface of the gelatin nanolayer by covalent crosslinking to achieve targeted drug delivery. The results suggest that this nanosystem shows promise for further applications in cancer cell imaging and therapy.We have developed a simple and versatile strategy for To our knowledge, there have been no reports of MnO2 growth on the surfaces of UCNPs using the Lemieux\u2013von Rudloff reagent to achieve oxidation and MnO2 formation of UCNPs in one pot.Because OA-capped monodisperse UCNPs are synthesized in organic media, their transfer to the aqueous phase and their functionalization are challenging. To solve these problems, many researchers have focused on transferring hydrophobic nanoparticles to the aqueous phase by ligand exchange, silanization, or hydrophobic\u2013hydrophobic interactions.4 and NaIO4 in a mildly alkaline solution (pH 7.7) to accelerate the oxidation of OA, and this oxidation was accompanied by the growth of MnO2 on the surfaces of UCNPs molecules participate in many physiological processes not only in the cells, but also in blood with a concentration range from 0.8 to 15 mM.2 nanosheets can be converted to Mn2+via GSH reduction, but it is impossible for MnO2 to differentiate between the intracellular GSH and extracellular GSH in vivo. Hypothetically, MnO2 nanosheets were intravenously injected in in vivo experiments, MnO2 nanosheets may be reduced partly by GSH in blood, which would lead to false signal imaging or early cargo release before arriving at the tumor, decreased therapeutic efficiency, and side effects. So it is considerably necessary to protect MnO2 in the blood circulation, and to promise that MnO2 decomposition only happens in target cells or tissues. In the present work, a novel targeted drug carrier nanosystem was successfully fabricated to protect MnO2 from early decomposition in blood circulation by coating with mesoporous silica and capping with a gelatin nanolayer. More detailed information about this nanosystem is in the application part.Moreover, our group has reported the studies on using simple MnO4:Yb/Gd/Er UCNPs were synthesized according to a reported procedure.4 changed . Pictures of the reaction mixture at different times are shown in Fig. S3.NaYF Fig. S2a after 60 Fig. S2a. The flu2 nanosheets were prepared as a positive control according to a reported method,3/2 at 642.2 eV and 2p1/2 at 653.8 eV further indicate the presence of MnO2.2. XRD patterns of both the as-prepared and oxidized UCNPs were studied to investigate the phase effect of the oxidation process. From the XRD result shown in The identity of the precipitate formed on the surfaces of UCNPs was determined by energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). Compositional analysis by EDX indicated the presence of a new element (Mn) not observed in the EDX data for UCNPs Fig. S4. The exi2 nanosheets, the as-prepared UCNPs and oxidized UCNPs at different reaction times all exhibit a broad band at around 3430 cm\u20131, corresponding to the O\u2013H stretching vibration. A peak at 3020 cm\u20131 attributed to the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013H stretching vibration can be observed in the spectrum of UCNPs and UCNPs@MnO2 (12 h),2 (24 h), suggesting that all of the OA ligands on the surfaces of UCNPs were oxidized to azelaic acid ligands after 24 h. In addition, bands at 1557 and 1468 cm\u20131 observed in the spectrum of the UCNPs are attributed to the asymmetric and symmetric stretching vibrations of the carboxylate group of the OA ligand. However, in the two cases of the oxidized samples, bands corresponding to the carboxylate group are found at 1637 and 1563 cm\u20131, and 1632 and 1563 cm\u20131, respectively. The obvious changes of bands at around 810 cm\u20131 and 727 cm\u20131 observed in the spectrum of the as-prepared UCNPs and the oxidized UCNPs samples are associated with the external deformation vibration of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013H, which decreases in intensity with oxidation time. These results suggested the cleavage of the \u2013HC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH\u2013 group of the bound OA. The FT-IR spectrum also showed the characteristic absorbance of the Mn\u2013O stretching vibration at around 470 cm\u20131 in the spectrum of MnO2 and both of the oxidized samples,2 on the surfaces of the oxidized UCNPs. On the basis of the above FTIR results, it can be deduced that the OA ligands on the surfaces of UCNPs were oxidized to azelaic acids, and the oxidation process was accompanied by the successful growth of MnO2 on the surfaces of UCNPs.The capping ligands on the surfaces of UCNPs were identified by FTIR spectra in 2 samples, thermogravimetric analysis (TGA) was performed decreased to 7.2%, which was consistent with the calculated result (see the ESI2 (12 h) decreased to 8.7%, which was between 7.2% and 10.5%, indicating that 56.2% of OA ligands were oxidized to azelaic acid, which was consistent with the FTIR result.To evaluate the ligand content in the as-prepared UCNPs and oxidized UCNPs@MnOd Fig. S7. The oxi% Fig. S7, so we c2 growth on the surfaces of UCNPs, control group 3 , then the rapid IO4\u2013 cleavage of the hydroxyketone products (step 2), and finally MnO4\u2013 oxidation of the second stage products to carboxyl groups (step 3). In control group 1 \u03bcg mg\u20131, 50% of the initial upconversion luminescence of UCNPs was quenched. The luminescence of UCNPs was recovered in the presence of GSH characterized by TEM, EDX and FT-IR following the reported method,Kd = 0.8 \u00b1 0.09 nM),2@mSiO2@gel-sgc8) through the bifunctional cross-linker sulfosuccinimidyl 4-[N-maleimidomethyl] cyclohexane-1-carboxylate (sulfo-SMCC)A novel targeted drug carrier nanosystem Scheme S1 was succ Fig. S15.38 Then 2 from early decomposition, we tested the longitudinal relaxation rate (1/T1) of UCNPs@MnO2 and the gelatin-protected nanosystem when exposed to normal human whole blood. The results and MRI e (1/T1) of the a2 nanolayer is reduced to Mn2+ ions by intracellular GSH, which, in turn, facilitates the fluorescence recovery of UCNPs. Meanwhile, Mn2+ ions can act as the contrast agent for MRI, giving an activatable upconverted fluorescence signal and magnetic resonance signal.This protecting ability can be reversed by the acid-responsive properties of gelatin. After crosslinking, at neutral pH, the charge of the cross-linked gelatin was positive (4.7 mV) Fig. S18, and theT1-weighted MRI images compared to CEM cells alone and Ramos cells treated with the sgc8-nanosystem. The amounts of Mn2+ in each CEM cell and Ramos cell treated with 50 \u03bcg mL\u20131 sgc8-nanosystem were 0.073 and 0.009 pg, respectively, tested by ICP-OES. These results demonstrated that our designed nanosystem can be used as a luminescent probe and as an MRI contrast agent for live cell imaging. As a proof-of-delivery concept, Dox was loaded into the nanosystem (sgc8-nanosystem-Dox). To investigate the acid-induced and controlled-release properties, the sgc8-nanosystem-Dox was exposed to buffers with different pH values at 4.0, 5.0, 6.0 and 7.4, as shown in Fig. S21.CCRF-CEM cells with high membrane PTK7 expression were chosen as the target cancer cell line and Ramos cells without membrane PTK7 expression were used as a negative control cell line.2 nanolayer on the surfaces of the oxidized UCNPs. The oxidation time was shortened to half the time of the reported method. Detailed investigations confirmed the existence of the MnO2 precipitate and provided information about the degree of oxidation at different oxidation times. It should be noted that our finding on the color change when using the Lemieux\u2013von Rudloff reagent can be used as an indicator to track the oxidation process. Moreover, we believe that this MnO2 growth method is not limited to hydrophobic UCNPs. It can be a common strategy applied to other hydrophobic nanoparticles synthesized by high-temperature thermolysis, such as semiconductor and metal nanoparticles, where only the coordinating ligands will be oxidized by the Lemieux\u2013von Rudloff reagent. Coincidentally, the surface MnO2 precipitate can act as a common quencher of the fluorescence of the host nanoparticles. The fluorescence can be totally recovered by reducing agents such as GSH and DTT, indicating potential for activatable fluorescence imaging application.In conclusion, by optimizing the component concentrations in the Lemieux\u2013von Rudloff reagent, we have broadened the application of this reagent in transferring OA-capped UCNPs into an aqueous phase, to include the direct formation of a MnO2 from early reduction by GSH in blood by coating with an acid-responsive gelatin nanolayer for more accurate imaging signals. The successful growth of MnO2 on the surfaces of UCNPs and the fabrication of the targeted delivery and imaging system suggest that it is possible to expand the application of the Lemieux\u2013von Rudloff reagent and these UCNPs@MnO2 carriers as activatable luminescent labels and contrast agents to other biological fields, such as bioimaging and cancer cell therapy.Last, but also important, we provided a method to protect MnOThere are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The phosphaethynolate anion (OCP)\u2013 has three different functions in the reaction with 2,4,6-trimethylbenzoyl chloride (MesCOCl): it acts as a nucleophile, as an en-component in [2 + 2] cycloadditions and as a formal P\u2013 transfer reagent. \u2013 anion under the loss of carbon monoxide to yield a five-membered ring anion. Subsequently, the nucleophilic attack of the formed heterocyclic anion on a second acyl chloride molecule results in the 1,2,4-oxadiphosphole. The transient acyl phosphaketene is conserved during the reaction in the form of four-membered ring adducts, which act as a reservoir. Consequently, the phosphaethynolate anion has three different functions in these reactions: it acts as a nucleophile, as an en-component in [2 + 2] cycloadditions and as a formal P\u2013 transfer reagent.The reaction of Na(OCP) with mesitoyl chloride delivers an ester functionalized 1,2,4-oxadiphosphole in a clean and P-atom economic way. The reaction mechanism has been elucidated by means of detailed NMR-spectroscopic, kinetic and computational studies. The initially formed acyl phosphaketene undergoes a pseudo-coarctate cyclization with an (OCP) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO have been described.via the cleavage of the PC double bond \u2013 transient phosphinidenes or phosphinidene complexes, respectively. Recently, we reported the synthesis of several hetero-phosphaketenes employing the phosphaethynolate (OCP)\u2013 anion as a phosphorous nucleophile. Furthermore, the ambident character of this anion has been demonstrated.1b is slightly larger than that of 1a (1c contributes to the electronic ground state. It describes the (OCP)\u2013 anion as a donor\u2013acceptor complex of a P\u2013 ion and carbon monoxide. Similar to the description of a transition metal carbonyl complex, the CO unit acts as a \u03c3-donor and a \u03c0-acceptor.Decarbonylation reactions, such as the transformation of aldehydesat of 1a .7b Besid\u2013 ion, however, the contribution of the mesomeric structure 1c suggests that this anion may act as a P\u2013 transfer reagent. Indeed, we could demonstrate that the reaction of an imidazolium salt with Na(OCP) forms the adduct of the parent phosphinidene (P\u2013H) with the corresponding N-heterocyclic carbene. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) is formed as an intermediate, which delivers the PH fragment in a concerted reaction step under the extrusion of CO.\u2013 anion was found to be a useful synthon to obtain heterocycles and cages, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013CO2Et),4(COOEt)4]\u2013 was also obtained, accompanied by the loss of carbon monoxide.\u2013 and two equivalents of isocyanate formed five-membered azadiphospholides, which were found to be active catalysts for isocyanate trimerization via spiro phosphoranides.The delocalization of the negative charge hampers the spontaneous decarbonylation of the (OCP)1.000000,.000000 s\u2013 anion as both P nucleophile and P\u2013 transfer reagent.Here, we report the results of our investigations on the reactivity of Na(OCP) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO), which are the heavier analogues of acyl isocyanates. Knowing that sterically demanding groups are needed to stabilize a phosphaketene in a monomeric form,2.5 was reacted with the rather bulky 2,4,6-trimethylbenzoyl chloride, MesCOCl, in a 1\u2009:\u20091 ratio is \u2013110 ppm at the B3LYP/aug-cc-pVDZ level of theory). Instead, two doublet resonances at \u03b4 = 112 and 253 ppm with a coupling constant of JPP = 46 Hz were observed. The 13C-NMR spectrum and in addition X-ray diffraction analysis revealed the formation of the acyloxy substituted 1,2,4-oxadiphosphole 3 shows a bond critical point between P1 and O3 and double bonds (C1\u2013P1 and C2\u2013P2), some extent of bond length equalization can be observed, which indicates a moderate aromatic delocalization. This is in agreement with previous theoretical studies, which stated that the aromaticity of the parent 1,2,4-oxadiphosphole is just slightly smaller than that of furan and other phosphasubstituted furans.d O3 see . The corfour equivalents of reactants are involved [2 MesCOCl + 2 Na(OCP)], a rather complex reaction mechanism with a number of steps must be involved in the formation of 3. To explore the reaction sequence, low temperature NMR measurements were performed. At room temperature the reaction is complete within mixing time of the reagents. A THF solution containing stoichiometric amounts of the starting materials was gradually warmed from \u201350 \u00b0C to room temperature and the progress of the reaction monitored using 31P-NMR spectroscopy. At \u201335 \u00b0C the parallel formation of two intermediates A and B was observed. NMR investigations at different temperatures indicated that B is in equilibrium with A and an (OCP)\u2013 anion. Intermediates A and B, the final product 3 and Na(OCP) are the only species which can be detected using 31P-NMR spectroscopy. NMR experiments using different stoichiometric ratios of the starting materials did give the same results.Since A and dianion B were identified using GIAO chemical shift calculations, which are shown in A and B are adducts of a mesitoyl phosphaketene molecule with one and two (OCP)\u2013 ions, respectively. This indirectly indicates the initial formation of mesitoyl phosphaketene, MesCO-P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO. The common structural motif of A and B is the four-membered P(CO)2P ring, which was first described for [O2C\u2013P(CO)2P]2\u2013, the adduct of a CO2 molecule and two (OCP)\u2013 ions.31P-NMR chemical shifts of this adduct (\u03b4 = 279 and 102 ppm) are indeed very similar to those of the rings in A and B. The 31P-NMR chemical shift of the P5 (80 ppm) atom in B matches well with that of bismesitoyl phosphide [P(COMes)2]\u2013, (\u03b4 = 86 ppm).26Anion A and B are involved in the formation of 3. We therefore reacted 2,4,6-trimethylbenzothioyl chloride (4) with Na(OCP) in the hope of identifying another possible intermediate. When Na(OCP) and 4 were reacted at \u201378 \u00b0C in a ratio of 2\u2009:\u20091, again gas evolution indicated the formation of carbon monoxide. Using NMR spectroscopy we could observe the formation of the anion 5, which was isolated in low yield \u2013 ion, leading to IM2. From intermediate IM2, which was not observed experimentally, the cyclic anions A, B and IM3 can be formed. A [2 + 2] ring closure of IM2 leads to its isomer A, while a formal cycloaddition of IM2 with another equivalent of (OCP)\u2013 anion delivers intermediate B. Presumably, the reactions leading from IM1 to IM2 as well as from IM2 to the intermediates A and B are reversible. This is supported by the experimentally observed equilibrium between A, an (OCP)\u2013 anion and B (vide supra).IM2 can undergo a cyclization under the loss of CO to yield IM3. In the final step, the nucleophilic substitution on an acyl chloride with IM3 gives the final product 3.In the first step, the acyl phosphaketene forms as intermediate 31P-NMR spectroscopy and the concentrations of Na(OCP), A, B and the final product 3 were determined from the relative integrals of the corresponding peak areas (see Under the assumption that the reaction mechanism shown in reas see . Applyinreas see . As cert\u2013 in mesitoyl chloride for (OCP)\u2013 is slower than the subsequent reaction of the activated acyl phosphaketene MesCO\u2013P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO IM1 with another equivalent of (OCP)\u2013. Indeed, this reaction between IM1 and (OCP)\u2013 is the fastest of all and explains why IM1 is not observed. Intermediate IM2 \u2013 likewise not observed \u2013 is consumed by four competing reactions: the back reaction to IM1 and (OCP)\u2013, the reversible formation of A, the reversible formation of B, which is faster than that of A (i.e. k4 > k3), and the irreversible formation of IM3 which is faster than that of A (i.e. k5 > k3) but smaller than that of B (i.e. k5 < k4). That A and B are transient but observable species is due to the slow back reaction to IM2, especially for B \u2192 IM2 which has the smallest rate constant, k4r. Consequently, the concentration of B increases steeply at the beginning of the reaction (in the first ca. 15 hours) and serves as a reservoir for intermediate IM2. Similarly, A is a conserved form of IM2, however in this case the accumulation effect is much less pronounced (k3 is similar to k3r) and the concentration of A is low and remains approximately constant throughout the reaction. IM2 is consumed irreversibly under loss of CO to give IM3, which rapidly and irreversibly reacts with acyl chloride to give the final product 3.In this model, the nucleophilic substitution of ClIM2 to A and IM2 to B were not investigated computationally, since similar transformations were subjects of a previous study.IM3 from IM2, however, deserves a closer look. High-level calculations revealed that this reaction follows a concerted mechanism and the activation barrier was found to be low /aug-cc-pVDZ//B3LYP/6-31+G* level of theory). The structure of the corresponding transition state is shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond of the phosphaketene moiety occurs simultaneously with the formation of the P\u2013O bond. A continuous change in the atom distances was observed along the reaction coordinate. In this process, the starting material, which consists of a phosphaketene unit and a separate delocalized OCPCO moiety, transforms to a moderately aromatic system. The increase in aromaticity is reflected by the NICS(0) values depicted as a function of the reaction coordinate, which become continuously more negative.In the present work, the reactions leading from IM3 is stabilized by a M\u00f6bius type eight-electron interaction and the coarctation of the orbital loop is at the P atom (see (IM2\u2192IM3) is almost planar and the barrier is very small, we propose that this reaction has pseudo-coarctate character. This is further supported by the ACID (anisotropy of induced current density) plot32Since there is an exocyclic part involved in this bond transformation process, we propose that this reaction is of coarctate type. Besides classical linear and pericyclic reactions, a third group of reactions was classified by Herges as coarctate.atom see . Coarcta\u2013 anion was found to react as a nucleophile and P\u2013 transfer reagent. The stepwise reaction mechanism was deciphered using low temperature 31P-NMR spectroscopy, kinetic measurements and theoretical calculations. Several [2 + 2] cycloaddition products were observed as intermediates using 31P NMR spectroscopy and identified with the help of chemical shift calculations, which demonstrate the performance of these theoretical methods. The formation of another, not yet observed, intermediate was made plausible through the reaction of Na(OCP) with a thioacyl chloride which gave a stable sodium 1,2,4-thiadiphosphol-3-olate. As observed previously in reactions with isocyanates\u2013 salts and heterocumulenes is the equilibrium, X PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tY PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tZ + (OCP)\u2013 \u21c6 [XY(PCO)Z]\u2013, which indicates the stability of the (OCP)\u2013 anion with respect to its addition products. The final formation of the oxadiphosphole ring proceeds in a concerted, pseudo-coarctate reaction step. This transformation is reminiscent of reactions seen with \u03b1,\u03b2-unsaturated organic azides and indicates a possible resemblance between the isovalence electronic (OCP)\u2013 and (N3)\u2013 anions.In conclusion, we have presented a one-pot synthesis for substituted 1,2,4-oxadiphospholes, utilizing Na(OCP) as the phosphorous source. The reaction is remarkably selective and atom economic with respect to phosphorous and excellent yields can be obtained. The (OCP)Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Formation and mode-specific autodetachment from a dipole-bound state in a radical anion dimer is observed in the frequency and time-domains. 0 dimer radical anion and its exited state dynamics. In the ground electronic state, the excess electron is localised on one monomer with a planar para-quinone ring, which is solvated by the second monomer in which carbonyl groups are bent out of the para-quinone ring plane. Through the \u03c0-stacking interaction, the dimer anion exhibits a number of charge-transfer (intermolecular) valence-localised resonances situated in the detachment continuum that undergo efficient internal conversion to a cluster dipole-bound state (DBS) on a \u223c60 fs timescale. In turn, the DBS undergoes vibration-mediated autodetachment on a 2.0 \u00b1 0.2 ps timescale. Experimental vibrational structure and supporting calculations assign the intermolecular dynamics to be facilitated by vibrational wagging modes of the carbonyl groups on the non-planar monomer. At photon energies \u223c0.6\u20131.0 eV above the detachment threshold, a competition between photoexcitation of an intermolecular resonance leading to the DBS, and photoexcitation of an intramolecular resonance leading to monomer-like dynamics further illustrates the \u03c0-stacking specific dynamics. Overall, this study provides the first direct observation of both internal conversion of resonances into a DBS, and characterisation of a vibration-mediated autodetachment in real-time.Isolated \u03c0-stacked dimer radical anions present the simplest model of an excess electron in a \u03c0-stacked environment. Here, frequency-, angle-, and time-resolved photoelectron imaging together with electronic structure calculations have been used to characterise the \u03c0-stacked coenzyme Q These interactions govern, for example, anion-recognition processes in supramolecular assemblies,0 dimer radical anion, (CQ0)2\u2013, the calculated minimum energy structure of which is shown in 0)2\u2013 is a useful prototype system because of the strong gas phase stability of one conformer, the well-understood dynamics of the isolated monomer radical anion, CQ0\u2013,para-quinones are often considered as prototypical electron acceptors due to their ubiquity in biological and technological electron transfer systems.0 is the smallest member in the coenzyme-Q series, where the subscript in CQ0 refers to the length of an isoprenyl tail attached to the para-quinone ring that serves to enhance lipid miscibility. It is thought that the synergetic co-operation of hydrogen bonding and \u03c0-stacking of the para-quinone ring in biological systems play important roles in facilitating electron transfer.para-quinones have been proposed as possible bypasses of the inverted Marcus region,Here, we consider the coenzyme Qpara-quinone radical anions have shown that photoexcitation cross-sections to quasi-bound \u03c0*-resonances can be larger than direct photodetachment.\u201314 s lifetimes); and Feshbach resonances, in which the corresponding neutral core is predominately in an electronically excited state . We have recently shown that anion photoelectron (PE) imaging is ideally suited to probe the dynamics of anion resonances,Recent gas phase studies on a series of monomer 0)2, with an electric dipole moment, |\u03bc| > 2.5 D, can support a dipole-bound state (DBS),\u03bc. Due to the diffuse nature of a DBS, the direct photoexcitation cross-section from a valence-bound state is usually very small. In contrast, photodetachment cross-sections of a DBS can be very large and increase with decreasing photon energy.Neutral molecules or clusters, such as (CQ0)2\u2013 is presented. The frequency- and angle-resolved dimensions involve recording single-photon PE images (spectra) at many different photon energies (h\u03bd) to identify trends and fingerprints of resonances and their associated dynamics. A selected resonance can then be photoexcited and the resulting dynamics monitored in real-time using time-resolved PE imaging. Supporting ab initio calculations using multi-state XMCQDPT2 theory with a large CASSCF reference space allow clear assignment of the experimental dynamics.h\u03bd = 3.10 eV with high intermolecular charge-transfer character leads to the formation of a DBS on a \u223c60 fs timescale, which then undergoes vibration-mediated autodetachment on a 2.0 \u00b1 0.2 ps timescale. This determination represents the first direct observation of the conversion of above-threshold valence-localised population to a DBS, and the first real-time characterisation of vibration-mediated autodetachment of a DBS. At slightly higher h\u03bd, a competition between non-adiabatic dynamics leading to the DBS and autodetachment dynamics has been observed. The competition is assigned to the interplay between dimer and monomer-like dynamics, and further highlights the role of \u03c0-stacking in influencing the excited state dynamics.Here, a combined frequency-, angle-, and time-resolved photoelectron imaging (FAT-PI)0)2\u2013 are shown in h\u03bd: (a) 4.66 eV (266 nm); (b) 4.13 eV (300 nm); and (c) the average of 2.53 eV (490 nm) to 3.02 eV (405 nm). The 4.66 eV and 4.13 eV spectra are also compared with selected PE spectra of CQ0\u2013 that extend to the same maximum in electron kinetic energy (eKE).0\u2013 and (CQ0)2\u2013 of \u223c1.2 eV. The spectra for (CQ0)2\u2013 and CQ0\u2013 broadly exhibit similar spectral features, except the dimer generally shows an increased yield of low-eKE electrons. The PE spectrum in h\u03bd, all of which are identical within noise. These spectra show three (perhaps four) reproducible partially resolved features that have the appearance of vibrational structure. It is remarkable that vibrational-like structure is discernible for such a large molecular system at 300 K, and implies a mode-specific detachment process.Three example PE spectra of , all PE spectra are essentially identical in h\u03bd \u2265 4.5 eV the PE spectra resemble that of the isolated monomer (0)2\u2013 has an increased yield of PE signal in the eKE \u2264 0.2 eV range.ical see . Between monomer ,28 althoh\u03bd, while the centre of the PD feature increases linearly with h\u03bd. The relative contributions of the three channels are shown in h\u03bd = 4.66 eV PE spectrum in h\u03bd < 3.0 eV, while the PD channel becomes dominant for h\u03bd > 3.0 eV. The modulation in region (ii) is reproduced between the PD and DBD channels. For h\u03bd > 3.5 eV, the DA channel becomes available and the contribution of the DBD channel is minimal (\u223c5% at h\u03bd = 4.66 eV).To analyse the detachment channel contributions in The adiabatic detachment energy (ADE) was determined in the global fit by extrapolating the rising edge of the PD feature for all frequency resolved PE spectra. Similarly, the vertical detachment energy (VDE) was determined from the maximum of the PD feature in the global fit. These data are tabulated in \u03b22 parameter (\u20131 \u2264 \u03b22 \u2264 2),\u03b22 values of \u20131 and +2 correspond to electron ejection perpendicular and parallel to the laser polarisation, \u03b5, respectively. In contrast to CQ0\u2013,PE angular distributions associated with h\u03bd < 4.0 is given in h\u03bd \u223c 3.75 eV, with its red edge overlapping with the modulations. While the total PE yield shows some reproducible closely-spaced oscillations, their extent does not account for the observed channel modulation. Instead, the modulations appear to result from a competition between processes yielding the two detachment channels rather than any sharp changes in the total photodetachment cross-section. Hence, the presentation of normalised PE spectra in To further investigate the DBD and PD channel modulation in region (ii) , the tot0)2\u2013 is shown in para-quinone ring is 3.9 \u00c5, which is the same as the neutral \u03c0-stacked benzene dimer.0)2\u2013 equilibrium geometry scale\" fill=\"currentColor\" stroke=\"none\">O) bond lengths of \u223c1.24 \u00c5. The right monomer has a non-planar geometry, in which the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO groups are bent out of the ring plane by \u223c12\u00b0, and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond lengths are \u223c1.20 \u00c5. In contrast, both monomers are planar with all C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond lengths of \u223c1.20 \u00c5 in the optimised (CQ0)2 geometry.The calculated minimum energy geometry of support the structure shown in 490)2\u2013] \u2248 BDE[(CQ0)2\u2013] + ADE[CQ0\u2013], where ADE is the adiabatic detachment energy and ADE[CQ0\u2013] = 1.60 \u00b1 0.06 eV.28Calculated photodetachment energetics (including zero-point energy) are summarised in 0)2\u2013 are summarised in 0\u2013.h\u03bd range. The 42[F] and 82[S] resonances predominantly involve intramolecular excitation processes on the planar monomer, while the 52[F] and 72[S] have a significant intermolecular or charge-transfer character. The 12A excited state is a bound charge-resonance state, corresponding to the radical anion localised almost exclusively on the non-planar monomer.Valence-localised vertical excited states of have been excluded because they are of \u03c0* \u2190 O(p) character, are optically inactive, and played no clear role in the dynamics of CQ0\u2013.The first excited neutral state is vertically situated at 2[S] (oscillator strength \u223c 0.05) and intramolecular 82[S] (oscillator strength \u223c 0.22) resonances. The spectrum has therefore been modelled using two Gaussians, plus an underlying baseline for prompt detachment and 92[F] contributions at high h\u03bd.The resonance energetics and oscillator strengths allow the broad feature in the photodetachment yield spectrum to be as2[F] or 72[S] resonances involves high excitation of carbonyl wagging, ring puckering, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC stretching modes, which are those required to achieve approximate 52[F]/32[F] and 72[S]/52[F] conical intersection geometries scale\" fill=\"currentColor\" stroke=\"none\">C and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching modes localised on the parent planar monomer.From the CASSCF wavefunction characters see ESI, Franck\u2013s see ESI. In cont\u03bc| in the ground electronic state of (CQ0)2 are \u223c6.9 D and \u223c5.5 D at the optimised (CQ0)2\u2013 and (CQ0)2 geometries, respectively, supporting DBSs with binding energy of \u223c150 meV and \u223c50 meV. However, the oscillator strength for direct photoexcitation of the DBS is \u223c10\u20134 to 10\u20135, which is small compared with those for valence-localised resonances. \u03bc at the (CQ0)2\u2013 and (CQ0)2 geometries. At the (CQ0)2\u2013 geometry, \u03bc is oriented between the \u03c0-stacked monomers and close to parallel with the planar monomer ring and the chord joining the two carbonyl groups on the non-planar monomer. In contrast, at the (CQ0)2 geometry the orientation of \u03bc is almost orthogonal to the monomer ring planes. Calculations connecting the ground electronic state (CQ0)2\u2013 to neutral geometries reveal that changes of the carbonyl tilt angle, \u03b8, associated with wagging modes of the non-planar monomer scale\" fill=\"currentColor\" stroke=\"none\">O bonds on the planar monomer), are the principal geometrical changes responsible for the large change in orientation of \u03bc. These C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO wagging modes are also FC active following intermolecular photoexcitation.Calculated values of |0)2 state, 11A at h\u03bd \u223c 4.5 eV from each of \u0394t \u2265 0 spectra. t, which reveals two timescales. The total PE signal was fitted with two functions: a Gaussian cross-correlation convoluted with an exponential decay for the fast component; and a cross-correlation function convoluted with an exponential rise and decay for the slow component. The fast component lifetime, t1 \u223c 60 fs, is limited by the experimental cross-correlation. The slow component reaches a maximum contribution after the fast component has decayed, and subsequently decays with a lifetime of t2 = 2.0 \u00b1 0.2 ps. From t1 is associated with the development and evolution of a broad PE feature into two narrow features, peaking at low-eKE and eKE = 1.6 eV. The high eKE feature is very close to the 1.55 eV probe energy and has a highly anisotropic PE angular distribution with \u03b22 \u223c +2 (see inset). The anisotropy suggests that the outgoing photoelectron has p-wave character, and therefore that the original orbital from which the electron is detached has s-character.t2 is associated with the concerted decay of both pump-probe features.Results of the 3.10 + 1.55 eV (pump + probe) time-resolved measurements are summarised in t1) to a narrow distribution. This PE feature is again situated at the probe photon energy with \u03b22 \u223c +2 angular character, and decays on a t2 \u223c 2.0 ps timescale. These observations are in agreement with the 1.55 eV probe experiments. However, concerted with the changes at high-eKE, there is now a bleach of the eKE < 0.25 eV signal, which recovers on the same t2 \u223c 2.0 ps timescale. t.Similar time-resolved measurements were performed with a 1.05 eV probe, which are summarised in 0\u2013)CQ0, composed of a localised planar monomer anion solvated by the second non-planar monomer. The frequency-resolved PE spectra broadly support this conclusion based on the similarity with CQ0\u2013 spectra when h\u03bd is red-shifted by \u223c1.2 eV 2 optimised geometry. Thus, ideal conditions for internal conversion to a DBS are achieved: the original FC photoexcitation modes of 52[F] modulates the 32[F] state over the DBS, which facilitates a curve crossing. The subsequent t2 = 2.0 \u00b1 0.2 ps lifetime of the DBS can be assigned to its autodetachment lifetime and leads to the vibrational structure observed in the DBD channel as seen in Before the DBS is formed, the time-resolved measurements showed a transient broad PE feature that sharpens to the DBS feature on a t1 timescale corresponds to only a few vibrational periods, implying that extensive intramolecular vibrational relaxation away from FC modes is unlikely.The overall time-resolved dynamics are summarised schematically in \u03bc 2\u2013.The vibrational structure associated with the DBD channel in the frequency-resolved spectra indicate\u03bc see , which i\u03bc see have bee3CN, CH3NO2, or nucleobases.3CN (|\u03bc| \u223c 3.9 D), which does not support a valence-bound anion, exhibits DBS autodetachment on a 4\u2013900 ps timescale.3NO2 (|\u03bc| \u223c 3.5 D) converts on a \u223c400 fs timescale to a valence-bound anion situated \u223c100 meV lower in energy, which is facilitated by a similar vibrational wagging and modulation of \u03bc to that for (CQ0)2\u2013.2[F] or 52[F] resonance) can also evolve into a DBS. However, in contrast to the Neumark studies, (CQ0)2\u2013 does not undergo internal conversion from the DBS to the lower-lying 12A and X2A states, probably because any coupling would require very large geometrical distortions (that may not support a DBS), and will be unlikely on the \u223c2 ps DBS autodetachment lifetime. It can therefore be concluded that internal conversion between a valance-localised state and a DBS, in either direction, requires near degeneracy. These trends provide further confirmation that the 32[F] resonance is likely involved in formation of the DBS rather than direct internal conversion from the photoexcited 52[F] resonance.Time-resolved dynamics involving DBSs have been implicated by the Neumark group in their femtosecond PE spectroscopy experiments following photoexcitation of iodine anions coordinated to CH0)2\u2013 is evidence of the extent to which the non-adiabatic dynamics are altered by \u03c0-stacking. Specifically, although the electronic ground state of the dimer represents a localised monomer that is merely solvated, a range of new non-adiabatic dynamics in the continuum are accessed due to the availability of charge-transfer excitations and a cluster DBS. This situation is likely to be common to other cluster anions with similar chromophore/electrophore groups, and means that the general extrapolation of monomer to cluster dynamics is not trivial. Nevertheless, as will be described next, monomer-localised dynamics can be observed in some circumstances.One of the key outcomes from , there should be photoexcitation features in 2[S] and 82[S] resonances. This conclusion is supported by three additional observations. First, h\u03bd > 3.8 eV the DBD channel yield diminishes, even though 82[S] is still strongly photoexcited. Second, from 2[S] photoexcitation profile. Third, for h\u03bd > 4.0 eV, the PE spectra of (CQ0)2\u2013 have a similar appearance to those for CQ0\u2013,The modulation between the DBD and PD channels in region (ii) of 2[S] resonance at h\u03bd \u223c 3.6 eV involves similar intermolecular FC modes as the 52[F] resonance. In contrast, photoexcitation of the 82[S] resonance almost exclusively involves intramolecular population of \u03c0*CC orbitals localised on the planar monomer. A conical intersection, detailed in the ESI,2[S] and 52[F] resonances are non-adiabatically connected along the FC modes in a similar way to the 52[F] and 32[F] resonances. Thus, a fast internal conversion of 72[S] population to 52[F] could be expected. In turn, the 52[F] resonance can form the DBS as above. Interestingly, the observed modulations in \u20131.Our calculations suggest that photoexcitation of the 7h\u03bd < 3.8 eV, the 82[S] resonance is predominantly photoexcited since it has a much higher oscillator strength. As this resonance is predominantly localised on the planar monomer, photoexcitation will involve intramolecular FC modes. From 2[S] photoexcitation does not result in efficient internal conversion to the DBS, rather the PD channel dominates. For h\u03bd > 3.75 eV, in which 82[S] is exclusively photoexcited, the competition between DBD and PD channels is no longer observed. Instead, the DA feature centred at eKE = 0.22 \u00b1 0.04 eV becomes available. The DA feature energetically correlates with a delayed autodetachment from the 42[S] resonance, which is also predominantly localised on the planar monomer. The assignment of DA to the 42[S] resonance suggests an internal conversion route from 82[S] photoexcitation. Because extensive nuclear motion (or energy redistribution) cannot occur on the ultrafast lifetimes of resonances, the internal conversion will be facilitated through intramolecular FC modes. In accord, the non-planar monomer effectively acts as a spectator so the detachment dynamics are monomer-like in character.h\u03bd > 3.75 eV PE spectra, which have a similar appearance to those of CQ0\u2013,For 3.55 < h\u03bd \u2265 3.8 eV range likely results from a mode-specific competition between non-adiabatic decay pathways of the 72[S] and 82[S] resonances. Such dynamics can only be uncovered by frequency-resolved PE spectroscopy combined with relative cross-section measurements. A detailed theoretical account of such dynamics will likely be very challenging, particularly due to the participation of the continuum. However, despite the interplay and competition of multiple channels, it is remarkable and encouraging that the technique of frequency-, angle-, time-resolved imaging can provide such rich insight. Overall, to the best of our knowledge, this study presents the first characterisation of a non-adiabatic dynamics competition between resonances with varying inter- and intramolecular character.In summary, the modulation between the DBD and PD channels in the 3.4 \u2265 We have demonstrated that intermolecular or charge-transfer photoexcitation can play a significant role in the excited state non-adiabatic dynamics of a \u03c0-stacked dimer radical anion. We have provided the first direct and real-time evidence of internal conversion of above-threshold resonances into a cluster-supported DBS, and its subsequent vibration-mediated autodetachment. Formation of the DBS is facilitated through charge-transfer photoexcitation by virtue of \u03c0-stacking. However, despite the additional complexity introduced by dimerization, monomer-like dynamics can also be observed following photoexcitation of resonances primarily localised on the monomer that supports the excess electron in the dimer ground electronic state. When both inter- and intra-molecular resonance photoexcitation profiles overlap, a remarkable competition between \u2018dimer\u2019- and \u2018monomer\u2019-like non-adiabatic dynamics has been observed. Such interplays between inter- and intramolecular non-adiabatic dynamics are likely to be common in other similar \u03c0-stacked cluster anions, and further illustrate the rich dynamics that can occur in the detachment continuum.Supplementary informationClick here for additional data file."}
+{"text": "We report the first examples of 7-membered diazaphosphepines using phosphorus\u2013amine (P\u2013N) chemistry. d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond position of heteropine core allows us to effectively control the chemical and electronic structures in both the ground and excited states of these diazaphosphepines. This functionalization has led to a diverse set of crystal structures, which has in turn provided access to rich photophysical and redox properties. Of particular interest is the evidence for planar \u03c0-conjugated backbone in our non-aromatic heteropine and twisted intramolecular charge transfer, which have never been reported for heteropines. The introduction of electron-accepting substituents at [d]-position of diazaphosphepines results in heteropines that are more electron deficient than any heteropine reported to-date. As proof of concept, we have fabricated organic solar cells with heteropines as non-fullerene acceptors.We have designed and synthesized the first examples of 7-membered diazaphosphepines using phosphorus\u2013amine (P\u2013N) chemistry. Different from previous functional protocols of heteropines, the installation of \u03c0-conjugated substituents having diverse chemistries at the [ PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond in the classical six-membered benzenoid building block with isoelectronic B\u2013N fragments has generated azaborine and borazine; materials comprising these substitutions display absorption and emission at energies lower than their pure carbon counterparts and, as such, have been incorporated in optoelectronic devices.\u03c0-Conjugated cyclic building blocks that contain heteroatoms have attracted a lot of attention due to their diverse chemical and electronic structures, and tunable electronic properties.Heteroatom-containing seven-membered cycloheptatrienes, namely heteropines, have not been studied extensively. Previous studies have focused on their fundamental characteristics, including their conformational change, chemical reactivity and electronic structure.b,d,f]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds is required to stabilize the seven-membered ring scale\" fill=\"currentColor\" stroke=\"none\">C double bond position of the heteropine core scale\" fill=\"currentColor\" stroke=\"none\">C bond accordingly. We thus expect BZ, FBZ, and BTD substituents to weaken electron delocalization in BZ-P, FBZ-P, and BTD-P, while CP, MI, and AN substituents to enhance electron delocalization in CP-P, MI-P, and AN-P. Electronic structure aside, we expect sterics to play an important role as well. Compared to five-membered ring substituents, like CP and MI, six-membered ring substituents, like BZ, FBZ, and BTD, as well as naphthalene-functionalized AN should exhibit stronger steric hindrance that will induce more twist when installed at the [d]-position of the diazaphosphepine core. This steric effect can also influence electron delocalization. The combination of both offers a powerful handle to fine-tune the intramolecular electronic communication of diazaphosphepines.We have chosen to introduce six \u03c0-conjugated substituents , includiBZ-, FBZ-, BTD-, CP-, MI- and -InAN are described in ESI.BZ-, FBZ-, BTD-, CP-, MI- and -InAN with PhPCl2 in the presence of NEt3 in anhydrous acetonitrile solution, resulting in BZ-, FBZ-, BTD-, CP-, MI- and \u2013PN in 55\u201380% yields. While the compounds were all obtained at reflux conditions, the ring-closing reaction to yield BTD-P and MI-P proceeds readily even at 0 \u00b0C, an indication of the ease with which these compounds can be made. Unique to this synthetic scheme are the mild reaction conditions and the absence of reactive intermediates, thereby enabling the installation of strong electron-withdrawing substituents, such as FBZ, BTD, and MI, which were inaccessible through previous synthetic protocols of heteropines and P-containing cyclic materials.The synthesis of diazaphosphepines is summarized in iii) center.2O2 (30% in H2O), BZ-, FBZ-, BTD-, CP-, MI- and -PAN are converted to their oxide derivatives in yields of 80\u201390%. The oxidation of these diazaphosphepines requires four days for complete conversion, which suggests their resistance against oxidation under ambient conditions. That our compounds are stable against moisture is perhaps not surprising given previous studies that have shown aminophosphines having pyrrole moieties to also be stable in water and alcohols. This phenomenon was attributed to the participation of N lone-pair electrons in the ring resonance.31P NMR spectra of the diazaphosphepines confirm the presence of two distinct classes of \u03c0-substituents in these species stemming from the different electronic character of the substituents; the 31P NMR spectra of BZ-, FBZ-, -PBTDs exhibit chemical shifts in the range of 38.5\u201338.7 ppm, which are up-field shifted compared to those of CP-, MI- and -PANs (40.3\u201344.4 ppm). All diazaphosphepines have been fully characterized, the results of which are summarized in ESI.Unlike carbon-based phosphepines, these diazaphosphepines are highly air-stable because the electronegative N atoms draw electron densities away from the P scale\" fill=\"currentColor\" stroke=\"none\">C double bond of BZ and BTD that now bridges the two ortho-indole moieties. This [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond is, for example, 1.418(2) \u00c5 in BZ-P compared to 1.392 \u00c5 in free-standing benzene,BTD-P compared to 1.42 \u00c5 in free-standing benzothiadiazole.c,e]-C\u2013C single bonds that connect BT and BZ to the indole moieties in BZ-P (1.473(2) and 1.477(2) \u00c5) and BTD-P (1.468(1) and 1.471(1) \u00c5) are shorter than typical C\u2013C single bonds (1.533(3) \u00c5).BZ-P and BTD-P despite the lack of coplanarity.We were able to obtain high quality single crystals of of BZ-P and BTD-P scale\" fill=\"currentColor\" stroke=\"none\">C double bond position to be a promising route for modifying the chemical and electronic structures of heteropines.The crystal structures we have examined thus far are aligned with our expectation based on the electronics of the substituents. We are thus surprised that the crystal structure of MI-PO is substr Fig. S3, which aAN-P also reveals a twisted backbone scale\" fill=\"currentColor\" stroke=\"none\">C double bond and a shorter -C\u2013C single bond, suggesting stronger electronic communication in AN-P. These observations also imply the electronic structure of the [d]-substituents to dictate \u03c0-electron delocalization in diazaphosphepines, with sterics playing a secondary role. The crystal structure of AN-PO scale\" fill=\"currentColor\" stroke=\"none\">C double bond length and -C\u2013C single bond length with that of AN-P, suggesting oxidation of the P-center does not affect the electronic communication between AN and the indole moieties in AN-PO.The crystal structure of backbone , presumaO Fig. S2 shows coBZ-P and CP-P; these compounds comprise the simplest of the aromatic and non-aromatic substitutions, respectively. CP-P are red-shifted compared to those of BZ-P, despite the fact that BZ has the larger conjugated \u03c0-system of the two. Both the absorption and emission spectra of CP-P show strong vibronic structures; these vibronic structures are not observed in the absorption and emission spectra of BZ-P. Additionally, the spectra of CP-P (\u0394\u03bbmax = 974 cm\u20131) show a smaller Stokes shift compared to those of BZ-P (\u0394\u03bbmax = 5641 cm\u20131). The fluorescence quantum yield of CP-P (14.5%) is about three times higher than that of BZ-P (5.4%). Collectively, the photophysics data suggest CP-P to exhibit a more conjugated and rigid structure compared to BZ-P. This assertion is further consistent with our theoretical calculations that reveal CP-P to possess a smaller HOMO\u2013LUMO gap (3.52 eV) compared to BZ-P .We carried out photophysical studies to probe the electronic structures of these diazaphosphepines. We start by comparing d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond experiences strong electronic confinement. This electronic confinement prevents efficient intramolecular electronic communication between the two indole moieties. In contrast, the \u03c0-electrons of the same C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond in CP are less electronically confined and should instead allow more efficient electronic communication between its two indole moieties. This hypothesis is further supported by the comparison between their precursors BZ-In and CP-In that is detailed in Fig. S7.BZ-In is blue-shifted compared to that of CP-In. In addition to electronic effect of the [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond, the twisted structure observed in crystal of BZ-P could also limit efficient electron delocalization.Given the local aromaticity of BZ, the \u03c0-electrons of the -C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, it thus exhibits the weakest C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond character, as evidenced by its degenerate HOMO\u20131 calculations to verify the aromatic character of the central seven-membered P-ring in our diazaphosphepines at the GIAO/B3LYP/6-31+g(d) level of theory. The NICS(1) values are all near-0, implying the non-aromatic character of these P-containing seven-membered rings Table S2. This reBTD-P shows a stronger solvatochromic effect than MI-P seems counter-intuitive since MI is a stronger electron-accepting substituent than BTD.BTD-P and MI-P, we carried out theoretical calculations on their excited states. The excited-state structures were optimized by TD-DFT. Their HOMOs and LUMOs were calculated at the B3LYP/6-31+g(d) level. In MI-P shows enhanced planarization in the S\u20321 state along with an elongation of the [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond, a shortening of the -C\u2013C single bonds and a decrease in the torsion angle compared to its S0 state. This comparison suggests enhanced \u03c0-conjugation in the excited state. The S\u20321 structure of BTD-P, on the other hand, is more twisted, with a shortening of its [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond and an increase in its torsion angle compared to its S0 state. This opposite trend suggests instead decreased \u03c0-conjugation in the excited state of BTD-P. Looking more closely at BTD-P, photoexcitation leads to a conformational change from its symmetric structure in its S0 state to an asymmetric structure in its S\u20321 state. In its S\u20321 state, the HOMO of BTD-P is mainly localized on one indole moiety, while the LUMO of BTD-P is mainly localized on the BTD substituent. Accordingly, the excited-state molecular dipole moment (2.49 D) is larger than that of its S0 state (1.63 D). Both observations point to enhanced intramolecular charge separation . This difference is consistent with the stronger solvatochromic effect observed in the emission spectra of BTD-P compared to that of MI-P. Further, the excited- and ground-state oscillator strengths of BTD-P are smaller compared to those of MI-P, which is also in line with the lower fluorescence quantum yield observed in BTD-P compared to MI-P. Finally, the calculated Stokes shift of BTD-P (0.78 eV) is larger than that of MI-P (0.28 eV), which is also consistent with experimental data.That paration comparedand LUMO . These oBTD-P) and non-aromatic (MI-P) substituents, the conformation of BTD-P appears unique, even amongst the diazaphosphepines having aromatic substitutions. Whereas the conformations of the excited states of BZ-P and FBZ-P are more planar compared to their ground states scale\" fill=\"currentColor\" stroke=\"none\">C double bond character. In addition to modulating the ground-state electronic structure of diazaphosphepines, our calculations thus show that [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC engineering tunes the excited state character of these compounds.While the above comparison highlights the ground- and excited-state differences between diazaphosphepines having aromatic , CP-P shows a smaller oxidation potential at 0.65 V that is consistent with its higher theoretical HOMO energy level and stronger \u03c0-conjugation observed in our photophysical studies. Enhancing the electron-accepting characteristics by replacing BZ with FBZ and BTD reduces FBZ-P\u2019s and BTD-P\u2019s susceptibility to oxidation, with BTD-P's oxidation potential outside the scan window. Compared to BZ-P, FBZ-P, and BTD-P, the oxidation potentials of CP-P, MI-P, and AN-P show a weaker dependence on the electronic character of the substituents. In fact, the oxidation potential of MI-P is much lower than those of FBZ-P and BTD-P, despite electron-accepting character of MI is stronger than both of FBZ and BTD. Such easy oxidation of CP, MI, and AN derivatives implies that strong electron delocalization along the backbone of CP-P, MI-P, and AN-P dominates their redox character. This observation is consistent with the trend of theoretical HOMO energy levels determined for these compounds.The introduction of substituents at the -C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond, providing access to electronic properties previously inaccessible in both the ground- and excited-states of heteropines. Particularly, our strategy allows us to access heteropines having much broader absorption and emission compared to the previous protocols. The MI-substituted diazaphosphepine exhibits planar \u03c0-conjugated structure that has not been accessed in non-aromatic heteropines. Having the weakest [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond character of the current series, the BTD-substituted diazaphosphepine exhibits twisted ICT in its excited state. This excited-state conformation contrasts the planar conformations of previous heteropines in their excited states. With the same chemistry, we have introduced electron-accepting substituents at the [d]-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond, which has resulted in compounds having more electron deficient character than any previously reported heteropines. Despite their low photocurrents, the operation of devices comprising these materials demonstrates\u2014for the first time\u2014the viability of heteropines as electron acceptors for organic photovoltaics.By leveraging the versatility of P\u2013N chemistry, we demonstrated that we can engineer the [Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "This work reports new (4 + 2)-annulations of \u03b1-alkyl vinylgold carbenes with benzisoxazoles to afford 3,4-dihydroquinoline derivatives with high anti-stereoselectivity. anti-stereoselectivity. The annulations are operable with carbenes in both acyclic and cyclic forms. This reaction sequence involves an initial formation of imines from \u03b1-alkylgold carbenes and benzisoxazoles, followed by a novel carbonyl-enamine reaction to yield 3,4-dihydroquinoline derivatives. This system presents the first alkyl C\u2013H reactivity of \u03b1-alkyl gold carbenes with an external substrate.This work reports new (4 + 2)-annulations of \u03b1-alkyl vinylgold carbenes with benzisoxazoles to afford 3,4-dihydroquinoline derivatives with high D/A) types I whereas highly desirable \u03b1-alkyl metal carbenes II are less efficient because of a competitive 1,2-hydrogen shift to form olefins (eqn (2)).+ carbons are highly cationic.ii) catalysts focused on \u03b1-alkyl metal carbenes of D/A types.D/A carbenes II, aiming at two objectives: (i) suppression of a 1,2-H shift and (ii) an alkyl C\u2013H reaction with an external substrate.Metal carbenes are versatile intermediates to implement a vast number of useful reactions including cyclopropanation, X\u2013H insertion , skeletal rearrangement and annulation reactions eqn 1)).).1 Despi).).1 DesD/A-type benzyl \u03b1-oxogold carbene II\u2032 (R = Ph and EWG = CO2Et), yielding an olefin product III\u2032 efficiently (eqn (3)). We envisage that D/D type carbenes such as \u03b1-alkyl alkenylgold carbenes IV might be viable species to achieve new annulations with benzisoxazoles because their gold-stabilized allyl cation character IV is unfavorable for a 1,2-H shift. According to this hypothesis, this work reports novel intermolecular (4 + 2)-annulations between \u03b1-alkyl vinylgold carbenes and benzisoxazoles, thus manifesting an unprecedented C\u2013H reactivity of \u03b1-alkyl metal carbenes.Interest in the reactions of benzisoxazoles is rapidly growing in gold catalysis because of their various annulation modes with gold \u03c0-alkynes.A that were generated in situ from cyclopropene derivatives 1a\u20131b and gold catalysts.6, quinoline derivatives 3a and 3b were isolated in satisfactory yields (72\u201375%), together with enones 1a-O and 1b-O in minor proportions (17\u201319%). A 1,2-hydrogen shift was effectively suppressed with vinylcarbenes A, supporting our hypothetic role of gold-stabilized allyl cations A.As shown in eqn (5), we further tested the reaction of acyclic alkylgold carbenes via cascade reactions. VI-1)\u2013(VI-6) bearing a common tricyclic framework VI, which can be easily constructed from cyclopentenylgold carbene A\u2032 and benzisoxazole. Indenoquinoline (VI-1) showed antiproliferative activities against breast (MCF-7) and lung epithelial (A-549) cells.VI-2 and VI-3 served as 5HT2c agonists and CRTH2 receptor modulators, respectively.VI-4 and VI-5 were N-containing steroids found in higher plants.VI-6 is a key intermediate for the total synthesis of naturally occurring (\u2013)-isoschizogaline9Our primary interest is to construct complicated frameworks lial A-54 cells.9a4a and benzisoxazole 2a in dichloromethane (DCM) using various gold catalysts; species 4a serves as a precursor for cyclopentenylgold carbene A\u2032 ; the latter was derived from a 1,2-H shift of gold carbenes A\u2032 that was generated from cyclizations of gold-stabilized pentadienyl cation A-I. Notably, an increased gold loading (10 mol%) enhanced the yield of desired 5a up to 85%. Other gold catalysts LAuCl/AgSbF6 (L = P(OPh)3, PPh3 and P(t-Bu)2(o-biphenyl)) gave 5a in 40\u201382% yields with L = P(OPh)3 being the most effective (entries 3\u20135). For various silver salts as in IPrAuCl/AgX (X = OTf and NTf2), resulting 5a was obtained in 65% and 71% yields, respectively (entries 6\u20137). AgNTf2 was entirely inactive (entry 8). IPrAuCl/AgSbF6 in various solvents gave 5a in the following yields: DCE 70%, MeCN 20% and 1,4-dioxane 0 (entries 9\u201311). The molecular structure of compound 5a was characterized with X-ray diffraction,anti-configuration between the alcohol and phenyl groups.An initial test of IPrAuCl/AgSbF4b\u20134t catalyzed with IPrAuCl/AgSbF6 (10 mol%) in DCM. All resulting products 5b\u20135t assumed anti-configurations with the alcohol and R1 groups being mutually trans. We tested the reaction of trisubstituted vinylallenes 4b\u20134f bearing R1 = 4-MePh, 4-OMePh, 4-ClPh, 4-CF3Ph and n-Bu, yielding desired 5b\u20135f in 78\u201388% yields (entries 1\u20135). For species 4g and 4h bearing 3-phenyl substituents (X = OMe and Cl), their corresponding products 5g and 5h were obtained in 84% and 87% yields, respectively (entries 6 and 7). The reactions were extensible to other vinylallenes 4i\u20134k bearing 2-naphthyl, 2-furan and 2-thiophene, further delivering desired products 5i\u20135k in 82\u201384% yields (entries 8\u201310). We tested the reaction on vinylallene 4l bearing distinct R1 = Me and R2 = Ph, which yielded compound 5l with an anti-configuration in which the hydroxy and methyl groups are mutually trans (entry 11); this configuration was established by the 1H NOE effect. Additional alkyl-substituted vinylallenes 4m\u20134p yielded desired 5m\u20135p in satisfactory yields . Variations of the R2 group with an n-butyl group as in species 4q gave expected product 5q in 86% yield (entry 16). We prepared species 4r bearing varied R2 = Ph and R3 = n-butyl, producing compound 5r in 80% yield (entry 17). For 1,3-disubstituted vinylallenes 4s and 4t (R3 = H), their resulting compounds 5s and 5t were obtained in 82\u201383% yields (entries 18 and 19).6a\u20136g, bearing varied phenyl , 2-thienyl and isopropyl substituents; these enyne acetates can be catalyzed with the same gold catalyst to yield distinct \u03b1-alkylgold carbenes A\u2032 -annulation products 7a\u20137g in satisfactory yields (61\u201374%), further manifesting the reaction generality (entries 1\u20137). For unsubstituted propargyl acetate 6h (R = H), its reaction led to a 68% recovery of initial 6h (entry 8). Even if the reaction is successful, a dehydration of compound 7h would occur to give quinoline products. The molecular structure of compound 7a (R = Ph) was confirmed with X-ray diffraction analysis that revealed an anti-configuration (11We tested these new annulations on distinct substrates such as enynyl acetates s A\u2032 see .12 To ouguration .112b\u20132j substituted with the C(3), C(5) and C(6) carbons. Other C(5)-substituted benzisoxazoles 2b\u20132f maintained high efficiencies to deliver anti-configured products 8b\u20138f in 80\u201390% yields (entries 1\u20135). High reaction efficiencies were maintained also for C(6)-substituted benzisoxazoles 2g\u20132i that furnished products 8g\u20138i in 86\u201392% yields (entries 6\u20138). A final applicable reaction with a C(3)-substituted benzisoxazole 2j enabled the production of a tertiary alcohol 8j, reflecting the reaction feasibility (entry 9). 1H NOE spectra were recorded to verify the stereochemistry of compound 8j ).9b was characterized with X-ray diffraction.9a and 9b with a gold catalyst were unsuccessful because of the two different forms of the enol imines (eqn (6)). To rationalize the origin of the stereoselectivity, compound 5a was treated with Zn(OTf)2 (20 mol%) in refluxing DCE to examine the hydroxyl epimerization that turned out to be slow. An equilibrium, anti/syn = 4\u2009:\u20091, was attained for species 5a after reflux in DCE for 48 h (eqn (7)).Gold-catalyzed reactions of 3,5-dimethylisoxazole anti-5avia NaBH4 reductions and m-CPBA oxidations, respectively yielding compounds 5a-H and 5a-O as single diastereomeric products. The stereochemistries of compounds 5a-H and 5a-O were established with 1H NOE spectra. Likewise, the acetate species 7a was readily removed under basic conditions, yielding the enol form 7a\u2032 as shown by its NMR in CD3COCD3 and CDCl3. We also studied an O3-induced oxidative cleavage of the acetate derivative 5a-OAc to cleave the olefin group, yielding the peroxide 35a-O in 85% yield. The molecular structure of species 35a-O has been characterized by X-ray diffraction.11A and benzisoxazole, yielding 2-iminoyl benzaldehyde C. This hypothesis is supported by our observation of 3,5-dimethylisoxazole, depicted in eqn (6). A tautomerization of imine species C is expected to form enamines D bearing an NH\u00b7\u00b7\u00b7O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC hydrogen bond. We believe that this enamine form, unlike other enamine-carbonyl couplings, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond to enable a concerted process, analogous to the well-known carbonyl\u2013ene reactions. A boat-like conformation D is favorable to yield anti-5 stereoselectively.As depicted in 1.000000,.000000 s2 to form 3,4-dihydroquinoline derivatives. Gold carbenes in cyclic and acyclic forms are both applicable. In this reaction sequence, the gold complex catalyzes an initial formation of imines between alkylgold carbenesvia a hydrogen bond to induce a carbonyl-enamine reaction. Control experiments with 3,5-dimethylisoxazoles supported this postulated mechanism. This new synthetic design involving \u03b1-alkyl metal carbenes of D/D types will attract growing interest because of its distinct utility.This work reports novel gold-catalyzed (4 + 2)-annulations between alkylgold carbenes and benzisoxazoles There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "DFT study to elucidate the mechanism of Rh-catalyzed C\u2013H aminations with N-mesyloxycarbamates and the pathway by which by-products formed. N-Mesyloxycarbamates are practical nitrene precursors that undergo C\u2013H amination reactions in the presence of rhodium dimer catalysts. Under these conditions, both oxazolidinones and chiral amines have been prepared in a highly efficient manner. Given the elevated reactivity of the intermediates involved in the catalytic cycle, mechanistic details have remained hypothetical, relying on indirect experiments. Herein a density functional theory (DFT) study is presented to validate the catalytic cycle of the rhodium-catalyzed C\u2013H amination with N-mesyloxycarbamates. A concerted pathway involving Rh\u2013nitrene species that undergoes C\u2013H insertion is found to be favored over a stepwise C\u2013N bond formation manifold. Density functional calculations and kinetic studies suggest that the rate-limiting step is the C\u2013H insertion process rather than the formation of Rh\u2013nitrene species. In addition, these studies provide mechanistic details about competitive by-product formation, resulting from an intermolecular reaction between the Rh\u2013nitrene species and the N-mesyloxycarbamate anion. Due to their high reactivity, only a limited number of discrete metal\u2013nitrene intermediates have been isolated.ii) dimer complexes, such as Rh2(OAc)4, using carbamate- and sulfamate-derived iminoiodinane reagents, a concerted asynchronous insertion of a singlet Rh(ii)\u2013nitrene has been found in previous computational studies,2(esp)2, an alternative one-electron mechanism involving Rh(ii)\u2013Rh(iii) intermediates has been proposed with a concerted C\u2013H insertion step.The synthesis of sulfonyl-protected amines has also been achieved ii)\u2013porphyrinvia a concerted or a stepwise mechanism. In the case of first row metal complexes reacting with azide reagents, experimental and computational studies imply an open-shell electronic state of the metal nitrene , the resting state of the catalyst, the rate-determining step, the mechanism (stepwise or concerted) and the pathway responsible for the formation of the by-products will be addressed in this computational study.Most computational studies had focused on the structure and reactivity of the metal nitrene species. As a result, little attention has been devoted to the formation of the metal nitrene species, and the type of nitrene precursors applied in C\u2013H amination reactions. Namely, the rate-determining step is unknown for pre-oxidized metal nitrene precursors, such as 2(OAc)4 crystal structure,vide infra) (A number of approximations were tested to determine their accuracy in reproducing the Rhe infra) . The purEst) of the dirhodium\u2013nitrene species ((HO(O)C)4Rh2 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNH) was calculated to be 1.4 kcal mol\u20131 with the Coupled-cluster (with) Single (and) Double (and Perturbative) Triple (excitations) (CCSD(T)) method,\u20131, the closest among all other computational methods studied. Conversely, hybrid functional methods afforded singlet\u2013triplet energy difference values superior to 10 kcal mol\u20131.\u20131 with PBE-DKH/BS3).\u03b5 = 5.98) on the gas-phase optimized geometries.The singlet\u2013triplet energy difference (\u03942(OAc)4 was chosen as the model for dirhodiumtetracarboxylate complexes. Although experimentally it was not the most active catalyst for the C\u2013H amination reaction with N-mesyloxycarbamates due to poor solubility, the catalyst provides the desired product with acceptable yields.N-mesyloxycarbamate (A) and n-hexyl N-mesyloxycarbamate (B) as the respective substrates (eqn (3) and (4)). The formation of the primary carbamate and the corresponding carbonyl compound was also studied, as these are known by-products identified namely in reactions with secondary N-mesyloxycarbamates (vide infra). (R)-Phenyl 2,2,2-trichloroethyl N-mesyloxycarbamate (C) is known to undergo C\u2013H amination with 2-phenylethane and was selected to model the intermolecular pathway (eqn (5)).In the interest of computational tractability, RhN-mesyloxycarbamate A and potassium acetate or sodium 2-ethylhexanoate (known to be soluble in organic solvents) produced the potassium or sodium N-mesyloxycarbamate salt as a white precipitate with a small energy barrier of 0.5 to 4.0 kcal mol\u20131 , leading to the most favoured TS and stable Salt-K. Similar results were obtained with sodium acetate and A with slightly higher values for the deprotonation TS , affording the sodium salt . Of note, it is known that lithium bases afford only trace quantities of the desired amination product, likely due to the poor solubility of these reagents. In addition, DFT calculations showed that the energy barrier for the deprotonation TS with lithium acetate and A was substantially higher than that with sodium acetate , confirming the experimental observations, a 7-membered ring coordinated lithium salt was observed 4, the potassium N-mesyloxycarbamate salt first forms a coordination complex (CO-K), in which the carbonyl of the carbamate is coordinated to the apical position of the rhodium complex . The CO-K complex affords the stable nitrenoid species (NRO-K) via the transition state TSCO-K, where both carbamate carbonyl and nitrogen are coordinated to rhodium. The calculated activation barrier is lower than the one for the deprotonation transition state. NRO-K is the most stable metal intermediate, displaying a strong interaction between the nitrogen atom and the rhodium center, with the leaving group (MsOK) still bound to nitrogen. The Rh\u2013nitrogen bond length of NRO-K is calculated to be 2.17\u20132.18 \u00c5 is due to the cleavage of the N\u2013O(Ms) bond to release the mesylate salt. Consequently, the formation of NR from NRO is entropy driven and the positive \u0394G value is a consequence of an increase of the enthalpy. Experimentally, we observed the precipitation of KOMs, which prevented the reversibility of the conversion of NRO-K to NR. The rhodium nitrene derived from N-mesyloxycarbamate C is the most stable, possibly due to a positive electronic effect of the trichloromethyl group.In the presence of Rh complex .83 The s7\u20132.18 \u00c5 . Conforme NRO-KA . Such ancies NR, . The depcies NR, . All thr1NR) and triplet (3NR) rhodium nitrenes for all three models has been calculated has two singly occupied MOs and the two unpaired electrons are mainly localized on the Rh\u2013Rh\u2013N moiety and 0.778 (C), and the configuration of the carbon atom changed from a pyramidal to a planar structure to produce INT. The result of the spin-density analysis shows that INT is a diradical (INT proceeds to the recombination transition state (TSr), the spin density of C decreases to 0.671 (A) and 0.766 (C). The configuration of the C atom returns to pyramidal with a shortening of the C\u2013N interaction to produce TSr. The relative reaction rates for the singlet pathways over the triplet may be estimated according to the transition-state theory (eqn (6)).The reaction barrier for rophilic . The LUMs of 1TS . There id manner . TripletN moiety . The foriradical . As INT ksinglet/ktriplet for the amidation of benzylic intramolecular and intermolecular C\u2013H bonds are 33.7 and 8.4 \u00d7 1010, respectively. Consequently, it appears that the singlet-concerted pathway is predominant and responsible for the formation of oxazolidinone and carbamate products.The relative reaction rates A, B & C) (A & B) are more facile than the intermolecular C\u2013H bond insertion (C) by 7.6 and 4.4 kcal mol\u20131, respectively, as a result of a favourable entropy. CTS is however an early, thus accessible transition state (TSn for the benzylic C\u2013H bond insertion (A) was determined to be 3.2 kcal mol\u20131 lower than the TSn for the singlet aliphatic intramolecular C\u2013H insertion (B), in agreement with experimental results reported. The structural analysis of the corresponding transition states shows that the Rh\u2013N(R) and C\u2013H bonds are 0.04 \u00c5 and 0.23 \u00c5, respectively, longer in BTS than ATS, whereas (H)C\u2013N and N\u2013H(C) bonds are 0.03 \u00c5 and 0.18 \u00c5 shorter, respectively is the resting state of the catalyst, i.e. the turnover frequency (TOF)-determining intermediate (TDI). The energetic span model was used to assess the kinetics of the catalytic cycle.NRO-K as the TDI, the transition state of the C\u2013H insertion (TSn) was established as the TOF-determining transition state (TDTS) or the transition state involved in the rate-limiting step. An energy range of 15.8 and 18.2 kcal mol\u20131 (\u0394\u0394G = \u0394GTSn \u2013 \u0394GNRO), corresponding to the apparent activation energies of the full cycle, was determined for, respectively, the intramolecular amination of benzylic C\u2013H bonds (A) and the intermolecular amination of C\u2013H benzylic bonds (C). The experimental and calculated kinetic isotopic effect also confirms TSn as the rate limiting step . The inton state . Among tectively . TSB is ing step . The proN-sulfonyloxycarbamates derived from secondary alcohols, the corresponding primary carbamate and carbonyl derivatives became the major products. For example, the reaction with trans-4-phenylcyclohexyl-N-tosyloxycarbamate D afforded the ketone and the corresponding primary carbamate in respectively 58% and 15% yields (eqn (7)). The formation of ketones has also been observed in rhodium-catalyzed C\u2013H amination reactions using iminoiodinanes as metal nitrene precursors.in silico data are available to support this hypothesis. With orthohalogenated N-mesyloxycarbamates such as substrate E, only the corresponding primary carbamate was isolated (eqn (8)). Primary carbamates have been observed in other catalyzed C\u2013H amination reactions. Initially, it was postulated that they arose from the homolytic cleavage of the [M]\u2013N bond, as they appeared only when the metal\u2013nitrene species are not rapidly intercepted by the substrate.via hydrogen atom abstraction processes from the substrate.72With a few substrates, namely A, but also from substrates D&E.1TSD is 4.1 kcal mol\u20131 more favourable than the \u03b1-C\u2013H amination 1TSD, leading to the formation of the corresponding ketone scale\" fill=\"currentColor\" stroke=\"none\">C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNOMs to regenerate DSalt-K.D, this pathway displays an overall free activation barrier shorter than the Rh\u2013N bond (2.09 \u00c5) than the one calculated for A was calculated for a hydride transfer from ESalt-K, forming EINT\u2032 (The hydride transfer hypothesis between (2.09 \u00c5) . Donatioed for A . It was ng INT\u2032E .1NRE potential energy surface revealed an energy barrier of only +4.9 kcal mol\u20131 leading to a less stable imido intermediate EINT\u2032\u2032 with a new C\u2013I (C\u00b7\u00b7\u00b7I = 2.22 \u00c5) bond formed (via the oxygen of the carbamate moiety simultaneously with the C\u2013I cleavage (C\u00b7\u00b7\u00b7I = 2.67 \u00c5) and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC formation of the alkene.However, if such a process is operative, the aldehyde would have been isolated experimentally. Ethyl acetate (solvent) was then suspected as the hydride source. The transfer to the d formed . The proGsol for the formation of the primary carbamate from 1NRE and EtOAc is \u201323.3 kcal mol\u20131. When compared to the hydride transfer pathway with ESalt-K, the kinetic process is 3.8\u00d7 faster with EtOAc. Given that EtOAc is also the solvent of the reaction, the pathway shown in 4 experimentally.Proton tautomerization affords the primary carbamate. The overall \u0394N-mesyloxycarbamates was presented, where we consider the concerted C\u2013H amination from a closed shell singlet Rh\u2013nitrene species and a stepwise radical mechanism starting from an open-shell triplet Rh\u2013nitrene species. The overall reaction is favoured by \u2248\u201350.0 kcal mol\u20131. The coordination of the anion of the N-mesyloxycarbamate with the catalyst takes place in an associative way, chelating the carbonyl function of the substrate to the catalyst. Upon coordination, the O\u2013Rh bond is substituted by the N\u2013Rh bond through a low activation barrier. With the inner nitrenoid complex identified as the TOF-determining intermediate, potassium plays a relevant role as the coordinative cation holding together the leaving group and the nitrene moiety giving rise to a stable nitrenoid complex. The potassium mesylate leaves the imido-complex through a late transition state where the barrier is reachable at room temperature. After the loss of the salt, the two spin states of nitrene species (singlet and triplet) are both capable of performing the C\u2013H insertion through two competitive paths. A concerted insertion through a singlet rhodium\u2013nitrene species is computed to have a smaller activation barrier, rather than a H-abstraction from the triplet nitrene species, affording the amine product and releasing the catalyst. Along with the kinetic isotopic effect, this computational study has clearly identified the C\u2013H insertion transition state as the one involved in the rate-limiting step. The rhodium catalyst is qualified as a more efficient catalyst for the C\u2013H intramolecular amination reaction under these conditions with a calculated TOF value of 2.3 \u00d7 102 h\u20131 compared to a calculated TOF value of 21 h\u20131 for the analogous intermolecular C\u2013H amination.A computational study of the rhodium-catalyzed C\u2013H amination with N-sulfonyloxycarbamate anion or ethyl acetate) affording the primary carbamate with or without the corresponding carbonyl by-product. Now that the pathway leading to their formation has been established, one can envision that the control of the reaction conditions may in some cases minimize the formation of these undesired products. Given that ketones had also been identified as by-products in other rhodium-catalyzed nitrene C\u2013H insertions,Furthermore, the DFT study has ruled out homolytic cleavage of the [M]\u2013N bond and \u03b1-intramolecular C\u2013H amination as pathways responsible for the formation of ketones and primary carbamates as by-products. There is instead a competitive intermolecular reaction of the singlet rhodium nitrene species with a hydride source (either the There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The first isolable germanium chalcogenide complexes 2\u20135 representing heavier congeners of CO and CO2 were synthesised from the germylone adduct 1. 2, their heavier mono- and dichalcogenide homologues, EX and EX2 , are important support materials and/or semiconductors and exist typically as insoluble crystalline or amorphous polymers under normal conditions. Herein, we report the first successful synthesis and characterisation of an extraordinary series of isolable monomeric GeX and GeX2 complexes , representing novel classes of compounds and heavier congeners of CO and CO2. This could be achieved by solvent-dependent oxidation reactions of the new zero-valent germanium (\u2018germylone\u2019)\u2013GaCl3 precursor adduct (bis-NHC)Ge0\u2192GaCl31 (bis-NHC = H2C2, Dipp = 2,6-iPr2C6H3) with elemental chalcogens, affording the donor\u2013acceptor stabilised monomeric germanium(iv) dichalcogenide (bis-NHC)GeIV scale\" fill=\"currentColor\" stroke=\"none\">X) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX\u2192GaCl3 and germanium(ii) monochalcogenide complexes (bis-NHC)GeII PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX\u2192GaCl3 , respectively. Moreover, the reactivity of 4 and 5 towards elemental sulphur, selenium, and tellurium has been investigated. In THF, the germanium(ii) monoselenide complex 4 reacts with activated elemental selenium to afford the desired germanium(iv) diselenide complex 3. Unexpectedly, both reactions of 4 and 5 with elemental sulphur, however, lead to the formation of germanium(iv) disulfide complex 2 under liberation of elemental Se and Te as a result of further oxidation of the germanium centre and replacement of the Se and Te atoms by sulphur atoms. All novel compounds 1\u20135 have been fully characterised, including single-crystal X-ray diffraction analyses, and studied by DFT calculations.In contrast to molecular CO and CO Generally, they adopt polymeric structures owing to the relatively weak p\u03c0\u2013p\u03c0 bond between germanium and the respective chalcogen atom and the high polarity of the E\u2013X bond. It has been shown that the molecular variants of EX and EX2 can exist in condensed cryogenic matrices at very low temperature or diluted in the gas phase at high temperature. Thus they have solely been detected spectroscopically4The binary group 14\u201316 compounds, EX and EX PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX 2 are still very rare. The first examples include the Sn PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (I) and Pb PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (II) units stabilised by a benzannulated bis-stannylene reported by Hahn and co-workers scale\" fill=\"currentColor\" stroke=\"none\">Se complex in {[K(18-crown-6)]-[K(en)2]K[Rh3(CN)2(PPh3)4(\u03bc3-Se)2(\u03bc-PbSe)]}2\u00b73en (III) as another type of EX coordinating to Rh sites complexes as precursors. By employing an N-heterocyclic carbene (NHC) (NHC = C:, Dipp = 2,6-iPr2C6H3), the disilicon(0) complex (NHC)Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(NHC) was synthesised by Robinson and co-workers,2O4IV stabilised disilicon(0) complex (CAAC)Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(CAAC),2 (V) and SiSe2 (VI) complexes could be obtained (2C2) we succeeded in the synthesis of a cyclic zero-valent monosilicon complex (\u2018silylone\u2019)3, namely (bis-NHC)SiS2 and (bis-NHC)Si scale\" fill=\"currentColor\" stroke=\"none\">S)SGaCl3 scale\" fill=\"currentColor\" stroke=\"none\">X and X PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX complexes. Herein, we wish to present a series of unprecedented germanium analogues of both CO and CO2 utilizing the donor\u2013acceptor stabilisation strategy.During the last decades, the concept of kinetic and/or thermodynamic stabilisation has enabled great achievements in synthesising isolable low-coordinate group 14 element species as ligands in complexes. Several unusual compounds featuring elusive terminal E-workers .5i Very Rh sites .6g In thrs,2O4IV , a complobtained .8b,c In Cl3 VII; .11 In faB, B is sensitive not only towards air and moisture, but also to visible light. For its reactivity investigation, we introduced the Lewis acid GaCl3 to prepare the more stable germylone\u2013GaCl3 adduct 1 through a one-pot reaction, starting from the bis-NHC supported chlorogermyliumylidene chloride (bis-NHC)GeCl2A species (germylone C)GeCl2A .10 Accor work-up .1 reflects the coordination of the germanium centre via one of its lone pair of electrons to the GaCl3 moiety, thus lowering the symmetry of the molecule relative to that of its precursor germylone B. Therefore the spectrum of 1 exhibits four doublets for the methyl protons and two septets for the methine protons in the isopropyl groups. Moreover, the two geminal protons in the CH2 moiety on the backbone in 1 give two doublets with 2JHH = 13.3 Hz \u00c5 in 1 is longer than that in germylone B (Ge\u2013C 1.965(2) \u00c5). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH\u2013N(Dipp)]Ga\u2013Ge[N(Dipp)]2CN(iPr)2.12The proton NMR spectrum of ric unit . A singl1 is much more stable than its precursor B because the zero valent germanium center is coordinated to the Lewis-acid GeCl3 by donating one of the two lone pairs of electrons to the electron-deficient gallium atom. It is noteworthy that germylone B also reacts readily with other Lewis acids such as AlBr3, BCl3, but the desired products could not be isolated in pure form as yet. However, B reacts smoothly with GaCl3 to afford 1 as an isolable product. Compound 1 is soluble in THF and acetonitrile. Treatment of THF solutions of 1 with 1/4 molar equivalents of X8 leads to quantitative formation of 2 and 3, which could be isolated in excellent yields as colourless and pale yellow solids, respectively in THF or acetonitrile solutions of the respective bis(NHC) ligand in the presence of GaCl3 failed. Likewise, other alternative approaches to synthesize 2 or 3 from the respective bis(NHC)GeCl4 precursor and in situ prepared M2X salts in the presence of GaCl3 were also unsuccessful which highlights the benefit of the reported synthetic method to form isolable monomeric GeX2 complexes. Compounds 2 and 3 are insoluble in hydrocarbons and only scarcely soluble in polar organic solvents such as THF and CH3CN as shown by a series of ESI-MS experiments. Thus only their 1H NMR spectra could be recorded in solutions but their low solubility prevents VT-NMR spectroscopy at low temperature.Complex ectively . We note2 and 3 suitable for X-ray diffraction analyses were obtained in dilute THF solutions. Unexpectedly, compounds 2 and 3 exhibit higher symmetry than 1, that is, only two doublets for the methyl protons in the CH(CH3)2 groups, instead of four doublets as in 1, could be detected in their 1H NMR spectra, suggesting the statistically equal position of the GaCl3 moiety between two sulphur or selenium atoms in solution, respectively GeS2 + H]+) and at m/z = 703.08749 GeSe2 + H]+), respectively.Fortunately, single-crystals of y see ESI. The ESI2 and 3 crystallise isotypic in the monoclinic space group Cm with two lattice THF molecules in the respective asymmetric unit and the single-crystal X-ray diffraction analyses revealed them to be isostructural, with each of the germanium centres bound to two chalcogen atoms (2 and Se1\u2013Ge1\u2013Se2 angle of 115.2(1)\u00b0 in 3, respectively, are reminiscent of the corresponding S\u2013Si\u2013S value observed in (bis-NHC)Si scale\" fill=\"currentColor\" stroke=\"none\">S) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS\u2192GaCl3 (115.0(1)\u00b0).2 and 91.8(3)\u00b0 in 3 are larger than that in 1 (85.7(1)\u00b0): accordingly, the Ge\u2013C bond distances (1.998(3) \u00c5 in 2 and 1.987(5) \u00c5 in 3) are slightly shorter than that in 1 (2.038 \u00c5).Compounds en atoms . Thus th2 (2.087(1) vs. 2.198(1) \u00c5) and the two Ge\u2013Se bonds in 3 (2.214(1) vs. 2.326(1) \u00c5) show a significant difference. The Ge1\u2013S1 bond length of 2.087(1) \u00c5 in 2 is slightly longer than that in Tbt(Tip)Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS (2.049 \u00c5), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS double bonds in LGe scale\" fill=\"currentColor\" stroke=\"none\">S)SH (2.064(1) \u00c5) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS)\u2013SPh 2.071(1) \u00c5 ,3 is slightly longer than that in Tbt(Tip)Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe methyl]phenyl, Tip = 2,4,6-triisopropylphenyl), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe group in LGe scale\" fill=\"currentColor\" stroke=\"none\">Se)\u2013SePh (2.205(1) \u00c5, L = aminotroponiminato ligand),3 is only slightly shorter than the Ge\u2013Se single bond in the latter complex (2.367(1) \u00c5).2 and 3 can be understood in light of the calculations presented below.The two Ge\u2013S distances in 2 and 3 is still unknown, it is reasonable to propose that the dichalcogenide formation occurs stepwise via the respective monochalcogenides as shown in 1 by one chalcogen atom to yield the divalent GeX complex C. The subsequent GaCl3 migration from the Ge(ii) centre to the more Lewis-basic chalcogenide site affords D bearing a three-coordinate Ge(ii) centre. Subsequent oxidation of the latter from Ge(ii) to Ge(iv) by an additional chalcogen atom results in the final product 2 or 3, respectively. These suggestions are supported by results of DFT calculations.1 \u2192 2 (and 3) are shown in Fig. S7 in the ESI.3 fragment, C \u2192 D is 29.9 and 29.5 kcal mol\u20131 for X = S and X = Se, respectively, in the gas phase (see details in the ESID (X = S) to 2 is by 5.0 kcal mol\u20131 more exothermic than for D (X = Se) to 3 (gas phase). The overall reaction from 1 to 2 (X = S) is more exothermic than from 1 to 3 (X = Se) by 10.3 (gas phase) 11.3 (CH3CN), and 10.9 (THF) kcal mol\u20131, in line with the experimental observation of a faster reaction for X = S than for X = Se.14Although the mechanism of formation of t, C \u2192 D , is exotC and/or D, 1/8 equivalent of S8 and Se8 were employed for the reaction with 1 at \u201330 \u00b0C in THF solutions. However, even at low temperature, regardless of the ratio of the two reactants, the dichalcogenides 2 and 3 are the exclusive products. In contrast, by employing acetonitrile as solvent the reaction of 1 with 1/8 equivalents of S8 at room temperature became much slower than in THF, and the reaction afforded a mixture containing 2 and, presumably, C and/or D (X = S). Furthermore, the reaction of 1 with 1/8 molar equivalents of activated selenium Se8 at room temperature became so slow that the formation of the germanium(ii) monoselenide complex 4, the selenium version of D (4 could be isolated from the resulting solution as a colourless solid in moderate yield (64%). For the reaction of 1 with elemental tellurium, the reaction is even slower than that with selenium and furnishes in THF at room temperature only the germanium(ii) monotelluride complex 5 in the 1H NMR spectrum of 4 (AB-spin system). The ESI-MS spectrum of 4 (positive mode) shows an ion peak of [M \u2013 SeGaCl3 + Cl]+ at m/z = 577.21454 corresponding to the [(bis-NHC)GeCl]+ (+A) cation. Indeed, the facile formation of similar species with a [LECl]+ cation naphthalene, E = Si, Ge) have been described in our previous reports.15Compound 4, the 1H NMR spectrum of 5 exhibits four doublets for the methyl protons and two septets for the methine protons in the CHMe2 groups. Similarly, the bridging N\u2013CH2\u2013N protons are coupled with each other with 2JHH = 13.1 Hz (AB-spin system). Similar to that of 4, in the ESI-MS spectrum of 5 a signal at m/z = 577.21399 centre is stabilised by the chelating bis-NHC ligand and the Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe moiety is supported by GaCl3 coordination, leading to a Ge\u2013Se\u2013Ga angle of 110.7(1)\u00b0. The three-coordinate Ge(ii) centre features a pyramidal coordination geometry with a sum of angle of 289.5\u00b0. The average Ge\u2013C distance of 2.050(3) \u00c5 in 4 is very close to that observed in 1 (2.038(3) \u00c5). The Se1\u2013Ga1 length of 2.337(1) \u00c5 is comparable to that in 3 (2.374(1) \u00c5) with a similar coordination environment. The Ge1\u2013Se1 distance (2.438(1) \u00c5) is significantly longer than the two Ge\u2013Se bonds in the four-coordinate germanium diselenide complex 3 (2.214(1) and 2.326(1) \u00c5). It is also longer than the Se\u2013Ge length of 2.346 \u00c5 in the (CO)5W PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe(SeAr)2 germanium(ii) species with a three-coordinate planar Ge centre. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe double bond character can not be concluded from the Ge\u2013Se distance. This is also manifested in the resonance structures 4\u2032\u2032 calculated by NRT which are discussed below.Compound ric unit , left. T5 suitable for X-ray diffraction analysis were obtained from THF solutions. 5 crystallises in the triclinic space group P1[combining macron] with three lattice THF molecules in the asymmetric unit. The latter analysis revealed a similar structure to that of 4 \u00b0. The germanium centre also adopts a trigonal\u2013pyramidal coordination geometry with a sum of bond angle of 285.8\u00b0 around the germanium atom. The average Ge\u2013C bond length of 2.037(4) \u00c5 in 5 is close to those in its precursor 1 (2.038(3) \u00c5) and in 4 (2.050(2) \u00c5). The Ge1\u2013Te1 distance of 2.654(1) \u00c5 is significantly longer than that in a four-coordinate germanium(iv) species LGe(R) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tTe\u2013GeCl2 (2.461(7) \u00c5) .4, the Ge\u2013Te double bond character in 5 is rather low. It is noteworthy that the 125Te NMR resonance of 5, similar to the 77Se NMR resonances of 3 and 4, could not be observed, presumably owing to the zwitterionic nature of 3 and 4 to sulphur, spontaneously yielding F. Subsequent displacement reaction of the latter should afford 2 as the final product. The latter scenario is supported by DFT calculations. For instance, the calculated reaction free energy (at B3LYP-D3(BJ)/def2-SV using the PCM model for the solvents' effect) of 4 + 1/4 S8 \u2192 2 + 1/8 Se8 is \u201321.6 (gas phase), \u201325.2 (acetonitrile) and \u201322.6 (THF) kcal mol\u20131. The migration from E to F is nearly thermo-neutral (\u0394G = \u20130.74 (gas phase), \u20131.60 (acetonitrile), and \u20130.64 (THF) kcal mol\u20131).14Since the germanium centres in ectively . Althoug4 with activated selenium can afford compound 3 in CH3CN. However, after 24 h only 10% of 4 reacted. In contrast, in THF the reaction is complete after 2 h. This may explain why 4 could be isolated in CH3CN, whereas only 3 was isolable in THF. On the other hand, no reaction of 5 with elemental selenium in both THF and CH3CN could be detected after 24 h, confirming that 5 is less reactive than 4. Furthermore, the reactivity of 4 towards tellurium in THF at room temperature was probed, however, after three days, no reaction occurred.As expected, the reaction of 1\u20135 and for the respective model compounds 1\u2032\u20135\u2032 where the bulky Dipp groups are replaced by Ph groups.1\u20135 at B3LYP-D3(BJ)/def2-TZVPP and those of 1\u2032\u20135\u2032 optimized at B3LYP-D3(BJ)/def2-SV are in good agreement with the corresponding X-ray structures.To obtain better understanding of the electronic properties and reactions of the novel compounds described in this article we performed DFT calculations for the synthesised compounds 2\u2032, X = S, and 3\u2032, X = Se) of 2.091 \u00c5 and 2.231 \u00c5 are longer than those of Me2Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX , respectively. This trend is in line with the Ge\u2013X Wiberg Bond Indices (WBI)2Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX are larger than those of 2\u2032 (1.39) and 3\u2032 (1.36). The calculated Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX bond length and WBIs in linear X PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX are 2.016 \u00c5 and 1.79, respectively, for X = S, and 2.145 \u00c5 and 1.82, respectively, for X = Se. The significantly smaller WBIs in 2\u2032 and 3\u2032 and the longer bond distances . The NCN bonds are 3-centre 4-electron bonds. This is manifested in the resonance structures which involve these electrons, i.e., N1 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC:N2 \u2194 N1:C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN2, and which are reflected in the C\u2013N WBI of ca. 1.25, suggesting a partial double bond character. The Ge\u2013C bond length is 1.998 \u00c5 and 1.987 \u00c5 in 2 and 3, respectively. The small WBI may reflect the contribution of resonance structures in which the Ge is bound to only one carbene unit (see below). The Ge\u2013C bonds are longer than that in the germylone precursor B (average r(Ge\u2013C) = 1.963 \u00c5, exp.et al., of 1.940 \u00c5 and 1.954 \u00c5.20The calculated Ge1\u2013X1 distances , feature two resonance structure types which are responsible for ca. 75% of the total contributions scale\" fill=\"currentColor\" stroke=\"none\">Ge\u2013X\u2013GaCl3 subunit with a X1 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tGe double bond and where the Ge is bound to only one of the carbenes, accounting for 23%, for both X = S and X = Se, of the total. (b) Structures containing a X\u2013Ge\u2013X\u2013GaCl3 subunit with a bond between the Ge and each of the NHC units. These structures account for 53% (X = S) and 55% (X = Se) of the total. Many electron permutations in the NHC rings are possible for both resonance structure types and the values in The dichalcogenides ibutions : (a) str4 and 5 scale\" fill=\"currentColor\" stroke=\"none\">X double bond in 4 and 5. This is supported by the NRT calculations for 4\u2032\u2032 and 5\u2032\u2032 R = Me which show that the major contribution stems from the resonance structures shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX double bond.The relatively long Ge\u2013Se and Ge\u2013Te distances in the monochalcogenides 1\u2032\u20135\u2032 is shown in Fig. S6 in the ESI.IVX2GaCl3 and GeIIXGaCl3 fragments. The positive charge on the Ge atom decreases along the series X = S > Se > Te in 2\u2032, 3\u2032, 4\u2032 and 5\u2032, while the charge on the GaCl3 fragment increases along this series. Our results indicate that the chalcogen\u2013GaCl3 interaction is strong. In fact, attempts to remove the coordinated GaCl3 from 2\u20135 by using strong external Lewis bases such as \u2018free\u2019 NHC with methyl ligands at nitrogen or less substituted bis-NHCs or chelating bis-thiols had been performed, but no reaction could be observed. At elevated temperature decomposition occurred, leading to hitherto unidentified mixtures.The calculated Natural Population Analysis (NPA) charge distribution in compounds 1, the Ge(0) atom can be readily oxidised with elemental chalcogens to form, in solvent-dependent reactions, the first donor\u2013acceptor stabilised isolable monomeric germanium disulfide 2, diselenide 3, monoselenide 4, and monotelluride complex 5, respectively. They represent novel classes of heavier congeners of CO and CO2 complexes. Apparently, the presence of the GaCl3 Lewis acid is essential for the stabilisation of all monomeric species bearing highly polar Ge PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tX bonds. In THF, the germanium(ii) monoselenide complex 4 can further be oxidised with activated selenium to yield the corresponding germanium diselenide complex 3. Unexpectedly, both selenide and telluride compounds 4 and 5 react with elemental sulphur to produce 2 with liberation of elemental selenium and tellurium, respectively. The unusual structural, spectroscopic, and electronic properties of these novel species could be determined and analysed by combined experimental and computational investigations. One of the important lessons from the calculations is that the bonding framework in all these compounds is complex and cannot be described properly by a single valance bond structure. Currently, we continue to explore the synthesis of Lewis acid-free germanium and silicon chalcogenide complexes and to exploit their reactivity in the context of small molecule activation and ligand ability in metal coordination chemistry. The strategy of donor\u2013acceptor stabilisation is also expected to pave the way to isolable monomeric SiO and SiO2 complexes. Respective studies are currently in progress.Due to the substantial Lewis acid stabilisation of the Ge(0) atom in Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Controlled oxidation of the terminal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond using O2 (1 atm) as an oxidant and reagent. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC alkynes to \u03b1-keto esters and quinoxalines via formation of phenylglyoxals as stable intermediates, under mild conditions by using molecular O2 as a sustainable oxidant. The current copper catalysed photoredox method is simple, highly functional group compatible with a broad range of electron rich and electron poor aromatic alkynes as well as aliphatic alcohols , providing an efficient route for the preparation of \u03b1-keto esters (43 examples), quinoxaline and naphthoquinone with higher yields than those in the literature reported thermal processes. Furthermore, the synthetic utility of the products has been demonstrated in the synthesis of two biologically active molecules, an E. coli DHPS inhibitor and CFTR activator, using the current photoredox process. In addition, we applied this methodology to the one-pot synthesis of a heterocyclic compound by trapping the intermediate phenylglyoxal with O-phenylenediamine. The intermediate phenylglyoxal can also be isolated and further reacted with an internal alkyne to form naphthoquinone. This process can be readily scaled up to the gram scale.Herein, we report a facile visible light induced copper catalyzed controlled oxidation of terminal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bonds by transition metal complexes in the presence of molecular O2 plays an important role in the chemical industry. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bonds to generate over-oxidized products.i)-catalysed cross-coupling and C\u2013H annulation reactions.i) phenylacetylide is the key photocatalyst involved in these visible light induced coupling reactions.i) phenylacetylide in the presence of molecular oxygen can generate Cu(ii)-phenylacetylide and a superoxide radical anion via the single electron transfer (SET) process. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond of a terminal alkyne.via controlled oxidation. \u03b1-Keto ester analogues are considered to be valuable precursors and intermediates for various pharmaceuticals and bioactive molecules.et al. reported the photoredox catalyzed synthesis of \u03b1-keto esters via oxidation of \u03b1-aryl halo derivatives using an expensive ruthenium catalyst under sunlight irradiation controlled oxidation of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond to phenylglyoxals, and thus no formation of ester or homo-coupling byproducts, and (d) a broad substrate scope and compatibility with a wide range of aromatic alkynes and 1\u00b0, 2\u00b0, or 3\u00b0 alcohols. To the best of our knowledge, the use of terminal alkynes as a key starting material for the synthesis of \u03b1-keto esters under visible light is yet to be reported.The significance of the present work includes the following: (a) this is the first example of oxidation of terminal alkynes to \u03b1-keto esters under visible light at room temperature under mild conditions; (b) low toxic, inexpensive CuI was used as a catalyst and abundant O1a) (0.5 mmol), MeOH (2a) (2 mL), copper iodide , and 2-picolinic acid (1.0 equiv.) as a ligand in CH3CN (4 mL) in the presence of molecular O2 was irradiated under blue LEDs at room temperature for 12 h, it furnished the desired \u03b1-keto ester (3a) with a yield of 86% was low and either the reaction failed or gave trace amounts of the desired product , n-propanol (2c), n-butanol (2d) and 2-methylpropan-1-ol (2e), and the desired product (3b\u2013e) was obtained in good yields at room temperature (2f) and benzyl alcohol (2g) providing \u03b1-keto esters (3f and 3g) in good to excellent yields under similar reaction conditions and tetrahydrofurfuryl alcohol (2i) reacted well with 1a to produce 3h and 3i in 84% and 68% yields, respectively, without cyclic ring opening. Next, 1a reacts with 2\u00b0 alcohols (2j\u20132l) smoothly to afford the corresponding \u03b1-keto esters (3j\u20133l) in good yields. Slightly strained or labile alcohols worked well in this protocol, without producing any cleavage products, which is not possible using the earlier thermal processes. Besides, 1a reacts with alicyclic 2\u00b0 alcohols (2m\u20132o) to afford the desired products (3m\u20133o) in good yields (p-benzoquinones in the presence of copper and O2.1a with tertiary butanol (2p) provided \u03b1-keto ester 3p in 70% yield with equal moles of 1\u00b0, 2\u00b0 and 3\u00b0 alcohols, such as MeOH (2a), isopropanol (2j) and tertiary butanol (2p), under standard conditions was surveyed, which afforded \u03b1-keto ester 3a as a major product in 73% yield derived from the 1\u00b0 alcohol, i.e., MeOH. Product 3j derived from the 2\u00b0 alcohol was formed in trace quantities without any \u03b1-keto ester 3p resulting from tertiary butanol. For nucleophilic attack on the glyoxal aldehyde, the 3\u00b0 alcohol is expected to be better than the 2\u00b0 alcohol and 1\u00b0 alcohol. This observed result clearly indicates that steric hindrance plays a more important role than the electronic factor, which leads to a predominance of the primary alcohol in the coupling reaction.Interestingly, cyclopropanemethanol (d yields . Unfortu0% yield . It is w4b\u20134j) with good to excellent yields as depicted in 3, CN, nitro, acetyl, ester, sulfone, and methoxy) groups showed excellent tolerance in the current photoredox protocol to give the corresponding \u03b1-keto esters (4k\u20134t) in good yields in moderate to good yields. However, heterocyclic alkynes ethynyl indole and ethynyl pyrimidine failed to give the desired \u03b1-keto esters under the current protocol. This protocol was successful in producing \u03b1-keto ester 4wa in 83% yield when heteroaryl alkyne 5-ethynyl-1,3-benzodioxole was used under similar conditions. Unfortunately, aliphatic terminal alkynes did not work for this protocol and failed to produce the corresponding \u03b1-keto esters as products. The reason for the failure of the aliphatic alkynes is most probably due to the lower acidity of aliphatic terminal alkynes as compared to aromatic ones, thus making the step of formation of copper phenylacetylide from aliphatic alkynes slower than that from aromatic alkynes.Note that when tertiary butanol was coupled with 1,3-dialkyne, only mono \u03b1-keto ester i)-catalyzed strategy was demonstrated for the expedient synthesis of compounds with biological activity, such as 1-benzyl-3-(3-nitrophenyl)quinoxalin-2(1H)-one 6n (a CFTR activator)5t (an E. coli DHPS inhibitor).6n could be carried out in 3 steps in 44% overall yield after irradiation with blue LEDs for 12 h at room temperature (ESI) and we have further evaluated and compared the green chemistry metrics o-phenylenediamines.2 as an oxidant. So, under the same reaction conditions, we added 1.0 equiv. of 4,5-dimethylbenzene-1,2-diamine (7) to the reaction solution and irradiated it with visible light for 12 h at room temperature (8), which is a biologically active FLT3 inhibitor,Synthesis of quinoxaline perature . Not sur-diamine to the ri)-phenylacetylide 1a\u2032 was reacted with MeOH, in the absence of CuI under similar reaction conditions, which produced the desired \u03b1-keto ester (3a) with 40% yield after 12 h of irradiation (eqn (1), To provide detailed insights regarding the reaction mechanism, we carried out several control experiments, as shown in i)-phenylacetylide powder exists in highly aggregated forms.in situ-generated Cu(i)-phenylacetylide is most probably the key light-absorbing photocatalyst involved in this oxidative coupling reaction. Next, we performed a short-time reaction of 3 h, under the optimal conditions, and we were delighted to isolate phenylglyoxal 13 as a stable intermediate in 62% yield (eqn (2), 2 mediated oxidation of substituted methyl ketones under harsh reaction conditions.13 for better understanding of the reaction mechanism. First, the reaction of phenylglyoxal with MeOH was carried out in the presence of light and O2, but in the absence of the CuI catalyst, which led to no formation of \u03b1-keto ester 3a (eqn (3), 2, but in the absence of the 2-picolinic acid ligand, only a trace amount of 3a was formed (eqn (4), 2, and blue light irradiation, 3a was produced in 90% yield (eqn (5), 2 atmosphere, no formation of 3a was observed (eqn (6), 2, and blue light irradiation all are very crucial factors for the formation of the \u03b1-keto ester product 3a.The reduced yield can be attributed to the fact that the isolated Cu scale\" fill=\"currentColor\" stroke=\"none\">C bonds via controlled oxidation to phenylglyoxal. It is documented in the literature that nitrogen containing ligands can reduce the formation of polymeric byproducts and Glaser alkyne\u2013alkyne homocoupling products.ii) bis-picolinate ligand, instead of a catalytic amount, is required to achieve the optimal product yield. Next, phenylglyoxal 13, isolated from the current photoredox process, could readily react with an internal alkyne for the synthesis of 1,2-naphthoquinone 16, via oxidative annulation reaction13 with MeOH was carried out under O2 in the absence of light, i.e., under dark conditions, which leads to no formation of \u03b1-keto ester 3a (eqn (9) and (10), i)-phenylacetylide, and is responsible for controlled aerobic oxidation of phenyl glyoxal to \u03b1-ketoesters.Selective oxidation of terminal alkynes to glyoxal, free from the subsequent over-oxidation to glyoxalic acid, is a very challenging reaction in synthetic chemistry.18O2 (98%), instead of 16O2 air, under the standard conditions -phenylacetylide (1a\u2032) triplet excited state Cu(i)-phenylacetylide (9)via ligand to metal charge transfer (LMCT).i)-phenylacetylide then donates an electron to molecular O2 to generate a superoxide radical anion (O2\u02d9\u2013) and an electron deficient Cu(ii)-phenylacetylide (10),ii)-phenylacetylide and subsequent reaction to molecular O2 results in the formation of copper(iii)-superoxo complex 11.iii)-peroxo complex (11)occurs with concurrent formation of a C\u2013O bond to form the intermediate (12).12) produces 2-oxo-2-phenylacetaldehyde (13) and CuII(pic)2 was eliminated as a blue ppt . When 4,5-dimethylbenzene-1,2-diamine (7) was present in the reaction mixture, it trapped the in situ-generated phenylglyoxal 13via intermolecular double condensation reaction to produce 6,7-dimethyl-2-phenylquinoxaline (8) in a one-pot manner, as shown in Based on the above control experiments and our previous studies,o-phenylene diamine acts as a better nucleophile (N is less electronegative than O) to phenylglyoxal than alcohol (2), thus favouring the formation of 2-phenyl quinoxaline (8), instead of the formation of hemiacetal (14).In the presence of 4,5-dimethylbenzene-1,2-diamine, the formation of \u03b1-keto esters was suppressed, due to the fact that PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC triple bond to phenylglyoxal at room temperature, followed by esterification, for the synthesis of \u03b1-keto esters that evades the need for a base, an expensive catalyst, strong oxidants, elevated temperatures and other harsh reaction conditions. The reaction proceeds easily with excellent functional group tolerance towards the electron donating and withdrawing terminal alkynes. Moreover, it is compatible with 1\u00b0, 2\u00b0, and 3\u00b0 alcohols and slightly strained or labile alcohols, which is not possible or difficult in thermal processes. The utility of this protocol has also been successfully applied for the synthesis of two biologically active molecules, i.e., 1-benzyl-3-(3-nitrophenyl) quinoxalin-2(1H)-one (a CFTR activator) and bis oxime ester (an E. coli DHPS inhibitor) on a gram scale with fewer steps and higher total yields than those in the literature reported processes. We have also demonstrated the one-pot synthesis of a pharmacologically active heterocyclic compound, i.e., 2-phenyl quinoxaline (an FLT3 inhibitor) via an unprecedented photoredox copper catalyzed process, as well as the synthesis of naphthoquinone using phenylglyoxal isolated from the current photoredox process.In summary, we have developed an unprecedented visible light induced copper catalyzed process for the controlled aerobic oxidation of the terminal CThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A supramolecular-gel-based twenty-two-member sensor array has been created by introducing well-designed multi-competitive binding interactions into a supramolecular gel. \u2013, Cl\u2013, I\u2013, CN\u2013, HSO4\u2013, SCN\u2013, S2\u2013, OH\u2013, Al3+, Fe3+, Zn2+, Hg2+, Pb2+ and H+) in water. It's important to note that this sensor array needs only one synthesized receptor. Moreover, using this method, we also obtained a series of ion response fluorescent supramolecular materials, which could act as security display materials. Therefore, it's a novel and facile way for the design of a simple sensor array as well as ion response fluorescent supramolecular materials.Sensor arrays are a powerful tool for multianalyte sensing and the development of an efficient sensor array has become one of the most intriguing problems. However, sensor arrays often employ lots of receptors which need large amounts of work to synthesise. This study describes an efficient method for the fabrication of a simple sensor array based on the competitive binding in supramolecular gels. By rationally introducing various well-designed competitive binding interactions into the supramolecular gel, which is self-assembled from a naphthylhydrazone-based organogelator, a supramolecular gel-based twenty-two-member sensor array has been created. Interestingly, the sensor array has been shown to accurately identify fourteen kinds of important ions (F It is worth mentioning that the sensor array was constructed using only one receptor. Simply stated, in the twenty-two-member sensor array, the organogelator not only acts as a gelator, but also as a receptor. The selective sensing properties of the sensor array are accurately controlled by the various competitive binding interactions which we rationally induced in the gel.Fortunately, the rapid development of stimuli-responsive supramolecular gelsG by introducing a coordination site, multi-self-assembly driving forces, and fluorescent signal groups into the gelator molecule. For example, we introduced an acylhydrazone group and a hydroxy group as the coordination, hydrogen-bonding and recognition sites, a naphthyl group as the signal group and \u03c0\u2013\u03c0 stacking site and long alkyl chains as the strong van der Waals forces group. The gelation abilities of G were examined in various solvents by means of the \u201cstable to inversion of a test tube\u201d method (Table S1G showed excellent gelation abilities in various solvents such as dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), acetone, ethanol, n-propyl alcohol, isopropanol, n-butyl alcohol, isoamyl alcohol, n-hexanol, cyclohexanol, ethyl acetate, CCl4, petroleum ether and so on. Among these solvents, the gelator G showed the lowest critical gelation concentration (CGC) and the highest gel\u2013sol transition temperature (Tgel) in n-butyl alcohol formed in n-butyl alcohol.Firstly, as show in Table S1. As we e Table S1. TherefoOG was investigated using 1H NMR, IR, X-ray and SEM. In the concentration dependent 1H NMR , \u2013NH (Hb) and \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH (Hc) resonance signals showed obvious downfield shifts as the concentration of G rose. These results revealed that in the gelation process, these groups formed hydrogen bonds with the \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC groups on the adjacent gelators. Moreover, the IR studies also confirmed this result, as shown in Fig. S4a,G, the stretching vibration of \u2013OH and \u2013NH appeared as a broad peak at 3202 cm\u20131, while, owing to the formation of hydrogen bonds, in the organogel OG, these absorptions were shifted to 3380 and 3244 cm\u20131, respectively. On the other hand, with the gradual increase in concentration, the 1H NMR signal of the naphthyl protons showed an obvious upfield shift, indicating that the \u03c0\u2013\u03c0 stacking interactions between the naphthyl groups were involved in the gelation process.\u03b8 24.5\u00b0 (d = 3.96) also confirms the \u03c0\u2013\u03c0 stacking interactions. Thus, the gelator G self-assembled to organogel OG through the hydrogen bonds and \u03c0\u2013\u03c0 stacking as well as the vdW existing in the long alkyl chains. The morphological features of the organogel OG were studied using SEM G has no fluorescence in hot n-butyl alcohol solution (T > Tgel). However, with the temperature of hot n-butyl alcohol solution dropping below the Tgel of OG, the emission intensity at 475 nm showed a sudden increase and reached a steady state, which indicated that the turquoise fluorescence of OG was AIE. Meanwhile, this emission shows a large Stokes shift ca. 175 nm to OG generated the corresponding metallogels respectively in y Fig. S8. InteresOG-based metallogels. As shown in \u2013, Cl\u2013, Br\u2013, I\u2013, AcO\u2013, H2PO4\u2013, HSO4\u2013, N3\u2013, SCN\u2013, S2\u2013, ClO4\u2013, CN\u2013, and OH\u2013) into the metallogel FeG, only HSO4\u2013 could induce the metallogel FeG emitting a turquoise fluorescence at 470 nm immediately. While other anions such as F\u2013, Cl\u2013, Br\u2013, I\u2013, AcO\u2013, H2PO4\u2013, N3\u2013, CN\u2013, SCN\u2013, ClO4\u2013, S2\u2013 and OH\u2013 could not induce any significant emission changes. Therefore, FeG showed selective fluorescence \u201cturn-on\u201d sensing of HSO4\u2013 in water. The detection limits of FeG for HSO4\u2013 are 1.0 \u00d7 10\u20136 M in CuG, CrG, BaG, EuG, TbG and the fluorescence metallogels such as AlG, LaG and so on. From the results, CuG, CrG, BaG, EuG, and TbG could selectively fluorescence \u201cturn-on\u201d sense SCN\u2013, S2\u2013, F\u2013 and OH\u2013 into the metallogels. As a result, LaG and YG could selectively sense Hg2+ and Pb2+ in and Pb2+ while Ruand Zn2+ respecti2+, Ba2+, Fe3+, Cr3+ or Ru3+ could quench the AIE of OG while the addition of Ca2+, Al3+, La3+, and Y3+ could induce the AIE of OG taking place with obvious shifts or enhancement, we rationally induced two different kinds of metal ions into OG to control the AIE of the gel. Due to the different coordination capabilities of the bimetal ions, there is competitive coordination existing in the gelator and the two kinds of metal ions (competitive binding interaction (D) in 3+ and Fe3+ into OG, we could obtain the corresponding bimetallogel AlFeG. Using a similar method, we could obtain a series of bimetallogels such as AlHgG, AlCuG, AlCrG, BaMgG, BaCaG and so on. Interestingly, as we expected, the fluorescence properties of the bimetallogel depends on the metal ion which has the stronger coordination capability than the other metal ion. For example, because the coordination capability of Fe3+ is stronger than Al3+, the fluorescence properties of AlFeG are similar to those of FeG. Therefore, AlFeG is a no fluorescence metallogel. Similarly, AlHgG, AlCuG and AlCrG are no fluorescence metallogels while BaMgG and BaCaG are fluorescence metallogels.In light of the above results that the addition of metal ions such as CuAlFeG, AlHgG, AlCuG and AlCrG could selectively fluorescence \u201cturn-on\u201d sense CN\u2013 (by AlFeG and AlCuG), Cl\u2013 (by AlHgG) and S2\u2013 (by AlCrG) respectively; while, BaMgG and BaCaG could selectively fluorescence \u201cturn-off\u201d sense I\u2013 and HSO4\u2013 respectively.Then, we introduced competitive binding interactions among the bimetal ions, anions, and gelators (competitive binding interaction (E) in OG. As show in \u2013, Cl\u2013, Br\u2013, I\u2013, AcO\u2013, H2PO4\u2013, N3\u2013, SCN\u2013, S2\u2013, ClO4\u2013, CN\u2013, and OH\u2013) into OG respectively, only CN\u2013 could induce the AIE emission of OG to take place a significant red shift from 470 nm to 520 nm immediately. Meanwhile, turquoise fluorescence of OG changed to yellow. While other anions such as F\u2013, Cl\u2013, Br\u2013, I\u2013, AcO\u2013, H2PO4\u2013, N3\u2013, SCN\u2013, ClO4\u2013, S2\u2013 and OH\u2013 could not induce any significant emission or color changes. Therefore, OG could selectively fluorescence and colorimetric sense CN\u2013 in water.Moreover, we also introduced competitive binding interactions between the anions and gelators (competitive binding interaction (F) in OG + CN, as a result, as shown in OG + CN can selectively sense Fe3+.Finally, we introduced competitive binding interactions among the anions, metal ions and gelators (competitive binding interaction (G) in via fluorescence titrations , which is lower than the WHO guideline of 1.9 \u00d7 10\u20136 M.The detection limits of this supramolecular gel-based sensor array for the corresponding ions were investigated Fig. S11. As a revia IR and SEM. For instance, in the FT-IR of OG scale\" fill=\"currentColor\" stroke=\"none\">O and \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH\u2013 vibration absorption peaks appeared at 1641 and 1594 cm\u20131 respectively. While, with the addition of Fe3+ into OG and the formation of FeG, these two peaks shifted to 1647 and 1588 cm\u20131 respectively, which was attributed to the coordination of Fe3+ with the gelator via the acylhydrazone group of the gelator. As we expected, after the addition of HSO4\u2013 into metallogel FeG, the \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and \u2013N PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH\u2013 vibration absorption peaks returned to 1641 and 1594 cm\u20131 respectively, which indicated that the HSO4\u2013 competitively binds with Fe3+ and releases the acylhydrazone group of the gelator. This result indicated that the ion sensing mechanism of the above mentioned metallogels and bimetallogels is based on the competitive coordination which took place among the gelators, metal ions or anions in the supramolecular gel system. In the corresponding SEM scale\" fill=\"currentColor\" stroke=\"none\">CH protons on G appeared at \u03b4 9.51 ppm. After adding CN\u2013, this signal faded away, while, two new signals appeared at \u03b4 3.10 and 5.64 ppm, which were attributed to the formation of the NC\u2013CH\u2013 and \u2013NH groups, respectively. Meanwhile, in the FT-IR of OG scale\" fill=\"currentColor\" stroke=\"none\">CH vibration absorption at 1594 nm\u20131 disappeared and a new \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN vibration absorption appeared at 2176 cm\u20131. These results indicated that the CN\u2013 was added to the imines group on OGvia a nucleophilic addition reaction and formed a new organogelator OG + CN. During this process, the emission band of OG underwent a red shift, which is attributed to the ICT process.The further response mechanism of Fig. S12, the \u2013N Fig. S4c, the \u2013NFeG could selectively fluorescence \u201cturn-on\u201d sense HSO4\u2013, while, upon the addition of Fe3+ into the HSO4\u2013-containing FeG, the fluorescence of FeG was quenched, which was attributed to the Fe3+ coordination with the gelator again. These properties make FeG act as a HSO4\u2013 and Fe3+ controlled \u201cOFF\u2013ON\u2013OFF\u201d fluorescent switch. By alternating the addition of HSO4\u2013 and Fe3+, the switch could be reversibly performed for at least three cycles with little fluorescence efficiency loss (EuG and TbG could selectively fluorescence \u201cturn-on\u201d sense OH\u2013, while, upon the addition of H+ into the OH\u2013-containing EuG or TbG, the fluorescence of EuG or TbG was quenched (+ competitively binding with OH\u2013 and the Eu3+ or Tb3+ coordination with the gelator again. Meanwhile, EuG and TbG could act as H+ sensors.The competitive binding mechanism was also supported by the reversibility of the sensing process. For example, the metallogel ncy loss . MoreoveFeG film has no fluorescence emission, when writing on the film with a writing brush dipped in HSO4\u2013 water solution, a brilliant blue fluorescent writing appeared. This fluorescent image could be erased by brushing Fe3+ on the film again. Other supramolecular gels (Moreover, these supramolecular gels could act as ion response fluorescent materials. For example, by pouring a heated solution of these gels onto a clean glass surface and drying in the air, we could obtain the corresponding ion response supramolecular films. As shown in lar gels show sim\u2013, F\u2013, SCN\u2013, Hg2+, Pb2+etc. with high selectivity and sensitivity in a water solution. This sensor array needed only one synthesized receptor. Moreover, using this method, we also obtained a series of ion response fluorescent supramolecular materials, which could act as erasable security display materials. Therefore, this is an efficient and simple way to develop a sensor array as well as stimuli\u2013responsive supramolecular materials.In summary, by rationally introducing competitive binding interactions into a well designed supramolecular gel, a twenty-two member sensor array has been successfully developed. This sensor array could sense fourteen kinds of important ions such as CNSupplementary informationClick here for additional data file."}
+{"text": "Hydrogen bonding-enabled highly regio- and stereo-selective hydrocarboxylation of alkynes has been successfully developed to afford 3-hydroxy-2(E)-alkenoates with up to 97% yield. syn-hydrocarboxylation of readily available 2-alkynylic alcohols with CO in the presence of alcohols with an unprecedented regioselectivity affording 3-hydroxy-2(E)-alkenoates. The role of the hydroxy group has been carefully studied. The synthetic potential of the products has also been demonstrated.Here we present an example of utilizing hydroxy groups for regioselectivity control in the addition reaction of alkynes\u2014a highly efficient Pd-catalyzed Surprisingly, the expected syn-hydrocarboxylation product (E)-2a\u2032E)-2a was exclusively formed unexpectedly together with 25% recovery of 1a (E)-2a -2a (E)-2a with 57\u201382% yields (E)-2a was improved to 90% but-3-yn-2-ol -2a . Varioussyn-hydrocarboxylation reaction delivered 3-hydroxy-2(E)-alkenoates as the sole product for various 2-alkynylic alcohols. Substitution of the pyridine ring at different positions made no difference (E)-2d in 71% yield -2h and (E)-2i in good yields -2j in 58% yield -2k in only 35% yield (1L), more rigid or more flexible backbone structures both made the reaction slower (1k (E)-2k could be obtained with the highest yield -2q was further confirmed by its single crystal X-ray diffraction analysis (E)-2s in 87% yield (E)-2t in 86% yield and 9% recovery of 1t (E)-2l in 89% yield -1\u2009E)-alkenoates with excellent ee values and high yields.Furthermore, as shown in E)-2l, Suzuki coupling reactions could easily afford (E)-7 in 80% yield.E)-8 in 80% yield,E)-9 in 80% yield.E)-10 in 94% yieldAs we know that 2-alkenoates are important intermediates in organic synthesis, their synthetic potential has been further demonstrated for the synthesis of different stereo-defined functionalized olefins. Owing to the presence of the C\u2013Br bond in -2k])} vs. reaction time , even with 10-fold excess of MeOH to ensure pseudo zero order in MeOH, indicating first-order dependence of the reaction rate with respect to propargylic alcohol -2k])} vs. reaction time, and show significantly different reaction rates, that is, the more electron-rich the substituent is, the faster the reaction rate is -2k and regenerate the Pd0 species to finish the catalytic cycle. Of course, further studies are needed to fully verify this mechanism.Based on these studies, a plausible mechanism is proposed . HydrogeE)-alkenoates and the observed regioselectivity may arise from hydrogen bonding, which needs further investigation. Due to the versatility of the functionality in the products, the importance of the stereo-selective construction of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds, and the nature of regio-selectivity control, this method will be of high interest to organic and medicinal chemists. Further studies in this area are currently ongoing in our laboratory.In summary, we have developed hydroxy group-enabled highly regio- and stereo-selective hydrocarboxylation of 2-alkynylic alcohols, exploiting a previously unrecognized regioselectivity control strategy. The remarkable substrate scope, atom economy, and good to excellent yields make this reaction a facile synthetic method to produce highly functionalized 3-hydroxy-2(There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Computational pipeline for the accelerated discovery of organic materials with high refractive index via high-throughput screening and machine learning. The process of developing new compounds and materials is increasingly driven by computational modeling and simulation, which allow us to characterize candidates before pursuing them in the laboratory. One of the non-trivial properties of interest for organic materials is their packing in the bulk, which is highly dependent on their molecular structure. By controlling the latter, we can realize materials with a desired density (as well as other target properties). Molecular dynamics simulations are a popular and reasonably accurate way to compute the bulk density of molecules, however, since these calculations are computationally intensive, they are not a practically viable option for high-throughput screening studies that assess material candidates on a massive scale. In this work, we employ machine learning to develop a data-derived prediction model that is an alternative to physics-based simulations, and we utilize it for the hyperscreening of 1.5 million small organic molecules as well as to gain insights into the relationship between structural makeup and packing density. We also use this study to analyze the learning curve of the employed neural network approach and gain empirical data on the dependence of model performance and training data size, which will inform future investigations. I.The packing of atoms, molecules, and polymers in a given volume \u2013 either in crystalline or amorphous form \u2013 is a fundamental and long-standing issue that has been considered by various disciplines for over a century.e.g., Traditional, experimentally-driven trial-and-error searches for new compounds with desired sets of properties have proved to be time consuming and resource intensive. The advent of powerful modeling and simulation techniques as well as readily available time on high-performance computing systems have brought computational and computationally-guided studies to the forefront of the chemical and materials domain. These studies allow us to make increasingly accurate predictions for compounds of interest and uncover promising leads for experimentalist partners to follow up on via the Slonimskii method and the packing coefficient from a support vector regression machine learning model.i.e., different density regimes). We also evaluate the learning curve for the density prediction to assess the dependence of training set size and model accuracy.In this work, we develop a DNN prediction model for the packing density of small organic molecules in an amorphous bulk phase and conduct a hyperscreening of 1.5 million candidate compounds. Our interest in this target property originates from our ongoing In Sec. II, we detail the methods employed in our work. We describe the MD modeling protocol we use to compute the density values (Sec. IIA), discuss the molecular design space we consider and the application of our virtual high-throughput screening tools on the resulting compound library (Sec. IIB), introduce our DNN prediction model (Sec. IIC), and establish our pattern analysis approaches to mine the obtained results (Sec. IID). Sec. III presents and discusses the outcomes of our study, in particular the density predictions from MD and DNN (Sec. IIIA), the efficiency of the DNN approach (Sec. IIIB), and the emerging structure\u2013property relationships (Sec. IIIC). Our findings are summarized in Sec. IV.II.A.via steepest descent. We then compute the packing density with the general Amber force field (GAFF).3 simulation box and fill it with the pre-optimized target molecules. The number of molecules in the simulation box depends on the given molecule size, but a typical system contains around 1000 molecules . The system is first subjected to a minimization of the internal energy, which is associated with the relaxation of bonds, bond angles, and dihedral bond angles. This is followed by NVT and NPT equilibration steps for 100 and 240 ps, respectively. Both NVT and NPT ensembles use a Nos\u00e9\u2013Hoover thermostat at 298.15 K for temperature control. The NPT ensemble uses the Parinello\u2013Rahman barostat for pressure control. We conclude the MD protocol with a final 40 ps NPT production run. We use an MD timestep of 0.2 fs. We obtain the density by averaging the density values of the system at intervals of 0.2 ps during this final run. We note that this protocol is expected to yield kinetically stable amorphous phases rather than thermodynamically stable crystal structures or meta-stable polymorphs. GAFF is known to underestimate the density values compared to those from experiment, especially for high-density compounds.We employ the following MD modeling protocol to generate the data for the training and testing of the DNN density prediction model at the center of this work. Starting from the simplified molecular-input line-entry system (SMILES)40B.ChemLGi.e., a molecular weight within the range of 150 to 400 Dalton and limiting the number of ring-moieties to four. The hydrogen atoms in each building block are used as linker handles. Our proof-of-principle library is designed to feature different connections between simple moieties, most of which are commonly used in organic materials . We use the eToxPred software to compute the synthetic accessibility score (SAscore) of all 15 building blocksWe create a virtual library of 1.5 million small organic molecules using our library generator code via the MD modeling protocol introduced in Sec. IIA, we employ our automated virtual high-throughput screening framework ChemHTPS.ChemHTPS creates inputs for the MD simulations, executes the modeling protocol, monitors the calculations, parses and assesses the results, and extracts and processes the information of interest. Of the 1.5 million compounds in our screening library, we randomly select a subset of 100\u2009000 for study at the MD level.To facilitate the density evaluation for a large number of compounds C.ChemML,ChemML employs the scikit-learn 0.18.2 library for the multi-layer perceptron regressor 1.17.1 . We apply the bootstrapping method, i.e., for each training set size, we obtain the training set by randomly sampling the entire data set. The remaining data points serve as test set. For every training set size, we repeat the process (with replacement) 50 times, i.e., all 50 repetitions are independent of each other. We subsequently calculate statistics over the results of the 50 models that are based on these training sets for each training set size.We use the MD results for these 100,000 molecules as the ground truth for our data-derived density prediction model. For this, we pursue a DNN approach within a feature space of molecular descriptors. We build the DNN model using r 1.17.1 and 197 D.Z-scores (Zi) of each building block i used in the creation of the molecular library aswithwhere M is the total number of molecules in the entire library, m is the subset of molecules under consideration , Ki is the number of occurrences of building block i in M molecules and ki its occurrences in the subset of m molecules. A large Z-score indicates that a building block appears more frequently in that subset compared to the rest of the library (or a random sample). By applying the hypergeometric distribution analysis, we can thus identify the building blocks with the largest impact on the target property and the degree to which they correlate with desired density values. Furthermore, we identify the building blocks that are prominent in particular density regimes and assess Z-score trends in density-ordered candidate subsets across the entire density range. In addition, we compute the average density values of the candidates derived from each building block, and analyze this data for trends. We employ the ChemML package for all data mining and pattern recognition tasks.In addition to identifying candidates with particular density values from our MD screening and DNN hyperscreening studies, we mine the compiled results to better understand the correlation between molecular structure and packing density. One pattern recognition approach we pursue is the hypergeometric distribution analysis, in which we determine the R2, slopes, and offsets of linear regressions.The following metrics are used in the error analyses of our modeling approaches: mean absolute error (MAE), mean absolute percentage error (MAPE), root mean squared error (RMSE), root mean squared percentage error (RMSPE), mean error (ME), mean percentage error (MPE), maximum absolute error (MaxAE), and maximum absolute percentage error (MaxAPE). Aside from providing these direct measures, we also quantify the extent of correlations and systematic biases between results of different methods by listing the correlation coefficients III.A.\u20133. As shown in the first column of e.g., processing and ambient conditions) that are not accounted for in the simulations. We also note that the experimental data set is structurally more diverse than the screening library, i.e., it includes non-aromatic and aromatic moieties, halogens, and different functional groups such as OH, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 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0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC, C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, N PBM data was replaced with SVG by xgml2pxml: 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0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, etc. Despite this diversity, the comparison shows an R2 of 0.95, which underscores the utility of the employed MD approach. To test the accuracy of the MD density modeling protocol introduced in Sec. IIA, we compare its results against the experimentally known density values of 175 small organic molecules.R2 = 0.98, both MAPE and RMSPE are around 1%, and MaxAPE is just 5.5%. Most importantly, we find that the DNN prediction errors are significantly smaller than the intrinsic MD errors (by a factor of 4 to 6), which means that the DNN and MD results are statistically indistinguishable. The prediction quality for the MD training data set is essentially identical to the test set shown in R2 = 0.89 shows that the DNN model still captures the structure\u2013property relationships to a certain degree, and given appropriate training data, DNN should deliver predictive models for those compound pools as well.The trained DNN model mimics \u2013 by design \u2013 the MD simulations it is derived from. The second column of \u20133 with an average of 1384 kg m\u20133. The results show a t- or Gaussian-like distribution and most of the compounds in the library have density values between 1200 to 1600 kg m\u20133, with only very few examples at the extreme high and low density regime. It is worth noting that these extreme packing density values may be desirable for certain material applications . The sparsity of instances for extreme density values emphasizes the valuable role that high-throughput screening studies via physics-based modeling and/or data-derived prediction models can play in the discovery of suitable materials candidates.With the accuracy of the trained DNN model established, we apply it to the remaining 1.4 million compounds of the screening library introduced in Sec. IIB with the expectation of obtaining similar results as MD would yield. The DNN density predictions are summarized in B.ChemHTPS without manual intervention.) The demand on disk space is another issue, and we estimate a need for 120 terabytes for the entire library (15 terabytes without trajectories). The DNN prediction model produces essentially the same results in less than 10 core hours of compute time (without performance optimization), with all but 10 minutes of the time required to generate the feature matrix of the compound library. Disk use is marginal. This corresponds to a speed-up of about seven orders of magnitude, with negligible loss in accuracy. A speed-up of that magnitude allows a corresponding increase in the scale and scope that is affordable for screening studies.After confirming that the DNN prediction model can accurately reproduce MD-level results , we now investigate its efficiency, in particular relative to MD. Our MD calculations for the subset of 100\u2009000 molecules took a total of 5 million core hours of compute time on a modern high-performance computing cluster. For the entire screening library, this extrapolates to approximately 75 million core hours perform poorly. Models based on 2000 to 4000 data points offer acceptable accuracy. Those based on 4000 to 6000 data points offer very good accuracy, and at 10\u2009000 data points, the training is essentially saturated and the learning curve plateaus off. Additional training data does not lead to an improvement of the DNN model and is essentially wasted. Thus, we do not require a large data set of 100\u2009000 molecules to learn the packing density of organic molecules. We can develop an accurate model using MD data of just 5000 molecules (or more conservatively 10\u2009000). This reduces our demand of computing time from 5 million to less than 0.25 (or 0.5) million core hours , which has significant implications for the cost-benefit analysis and viability of this approach.The bottleneck of our DNN prediction model is the generation of the training data needed for its creation. It is worth noting, though, that this is a fixed cost rather than an effort that scales with the number of compounds studied. The size of the employed training set (100\u2009000 compounds corresponding to 5 million core hours) was originally chosen postmortem analysis of the learning curve as provided here, we will use an on-the-fly assessment of the learning curve combined with a just-in-time termination of the training data generation to minimize our data footprint in future studies.We stress that the data demand is highly dependent on the nature of the data and the employed machine learning approach (including the feature representation), and there are distinct limits to generalizing our findings. Instead of a C.cf.B7 and B12 have the highest average densities, while those that incorporate B1 (CH2-linker) and B9 (cyclopentane) exhibit the lowest values. Aside from the linker groups, there is a clear correlation between density value and the heteroatom type and fraction in a corresponding moiety.When considering the screening results, we are not only in a position to assess a large number of compounds, but we can also learn patterns from the data set in its entirety. Our analysis in Based on the construction of our library, more than 80% of the candidate compounds contain sulfur and more than 90% contain nitrogen. cf.Z-score analysis introduced in Sec. IID. i.e., the top 10% subset) with clear and distinct trends. Consistent with our previous analysis, we observe very large Z-score values for and thus a strong overexpression of B7 and B12. B13 (thiazole) also shows a large Z-score, and so do to a lesser extent B2 (S-linker) and B3 (O-linker) as well. These moieties are clearly favorable if high-density compounds are desired. In addition to assessing the high-density regime, we employ the hypergeometric distribution analysis to identify the prevalence of building blocks in the complete spectrum of density values. For this, we sort our virtual library by increasing density values, divide it into ten equal segments, and perform our analysis within each of these subsets as shown in Z-score of building blocks B2, B7, B12, and B13 increases with increasing density values, indicating a direct correlation, whereas it decreases for B1, B4, B9, B10, and B15, indicating an inverse correlation. The former are thus suitable to design organic molecules with higher density, and the latter could be used to achieve compounds with lower density. These findings are consistent with our prior analysis.While the average density values indicate the cumulative impact of a particular building block, we find relatively large standard deviations cf.. For a mIV.ChemLG molecular library generator code, the ChemHTPS automated high-throughput in silico screening program, and the ChemML machine learning package) in facilitating and supporting research efforts of this nature.The ability to predict the properties of novel compounds prior to synthesis, and to understand how these properties depend on their structure, is of considerable importance in materials discovery and design. In this paper, we showed that MD simulations can accurately predict experimental packing density values of small organic molecules and we provided corresponding benchmark results to quantify this finding. We conducted a high-throughput MD screening of 100\u2009000 compounds, which allowed us to train a DNN density prediction model. This DNN model accurately reproduces the MD data within the margins of MD's intrinsic error, while being nearly seven orders of magnitude faster than MD. This exceedingly efficient approach allowed us to rapidly obtain the density values of a 1.5 million compound screening library, which would have been prohibitively time consuming and well out of reach for MD. By analysing the large data set resulting from this study, we could elucidate structure\u2013property relationships that determine the density values. We identified prevalent moieties in the high and low density regime and could quantify the impact of heteroatoms (sulfur and nitrogen). Further, we evaluated the DNN learning curve for the density prediction with respect to the available training data and found a considerably lower data demand than we had anticipated. Following this lesson, we will in future studies employ an on-the-fly assessment of the learning curve and terminate the training data generation once we observe satisfactory saturation. This will allow us to alleviate the data generation bottleneck and make machine learning models an even more viable and attractive proposition. Overall, our study underscores the value of combining powerful machine learning approaches with traditional computational modeling for the generation of the necessary data. It also demonstrates the utility of our software ecosystem (including the The authors declare to have no competing financial interests.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file."}
+{"text": "Efficient removal of ammonia from air is demonstrated in a series of Br\u00f8nsted acidic porous polymers under dry and humid conditions. The impact of acidic group strength and their spatial distribution on the ammonia uptake is investigated systematically. 3) is also highly toxic and presents a substantial health and environmental hazard. The development of new materials for the effective capture and removal of ammonia is thus of significant interest. The capture of ammonia at ppm-level concentrations relies on strong interactions between the adsorbent and the gas, as demonstrated in a number of zeolites and metal\u2013organic frameworks with Lewis acidic open metal sites. However, these adsorbents typically exhibit diminished capacity for ammonia in the presence of moisture due to competitive adsorption of water and/or reduced structural stability. In an effort to overcome these challenges, we are investigating the performance of porous polymers functionalized with Br\u00f8nsted acidic groups, which should possess inherent structural stability and enhanced reactivity towards ammonia in the presence of moisture. Herein, we report the syntheses of six different Br\u00f8nsted acidic porous polymers exhibiting \u2013NH3Cl, \u2013CO2H, \u2013SO3H, and \u2013PO3H2 groups and featuring two different network structures with respect to interpenetration. We further report the low- and high-pressure NH3 uptake in these materials, as determined under dry and humid conditions using gas adsorption and breakthrough measurements. Under dry conditions, it is possible to achieve NH3 capacities as high as 2 mmol g\u20131 at 0.05 mbar (50 ppm) equilibrium pressure, while breakthrough saturation capacities of greater than 7 mmol g\u20131 are attainable under humid conditions. Chemical and structural variations deduced from these measurements also revealed an important interplay between acidic group spatial arrangement and NH3 uptake, in particular that interpenetration can promote strong adsorption even for weaker Br\u00f8nsted acidic functionalities. In situ infrared spectroscopy provided further insights into the mechanism of NH3 adsorption, revealing a proton transfer between ammonia and acidic sites as well as strong hydrogen bonding interactions in the case of the weaker carboxylic acid-functionalized polymer. These findings highlight that an increase of acidity or porosity does not necessarily correspond directly to increased NH3 capacity and advocate for the development of more fine-tuned design principles for efficient NH3 capture under a range of concentrations and conditions.Although a widely used and important industrial gas, ammonia (NH Solid-state adsorbents such as metal\u2013organic frameworks53) from air.3-based fuel cells after the gas decomposes to hydrogen.One example where this is of particular importance is in the removal of ammonia was recently investigated for NH3 capture.3 capacity was achieved using these materials, there was also a significant reduction in porosity upon functionalization with bulkier groups \u2013CO2H and \u2013SO3H, which hindered the accessibility and complete utilization of the acid sites. More recently, incorporation into a polymer membrane has been demonstrated to impart enhanced stability to the framework HKUST-1 under humid conditions, without diminishing NH3 capacity.14Ammonia can behave as both a Lewis base and a Br\u00f8nsted base, and therefore porous materials decorated with Lewis or Br\u00f8nsted acidic sites are promising targets for capture at particularly low concentrations.3 capture.\u20131 at an equilibrium concentration of \u223c500 ppm.\u20131 at \u223c900 ppm, in spite of its stronger Br\u00f8nsted acidity. This behavior was attributed to the presence of isolated and non-interacting acidic groups due to the non-interpenetrated structure of the material. Such a striking difference between these two polymers prompted us to further investigate the interplay between Br\u00f8nsted acidity and polymer structure in a systematic manner.Porous polymers have been investigated to a lesser degree in the context of low-pressure NH3Cl, \u2013CO2H, \u2013SO3H, and \u2013PO3H2 groups and P2-CO2H were recently reported,3H was achieved following a literature procedure.20The Br\u00f8nsted acidic porous polymers reported in this work were synthesized following either a postsynthetic functionalization strategy starting from PAF-1 or a 3Cl and P2-SO3H were synthesized protectiontert-butyl dicarbonate was followed by Miyaura borylation to afford 1a. The sulfonation of 1,4-dibromobenzene using chlorosulfonic acid (ClSO3H) provided 2,5-dibromobenzenesulfonyl chloride.1b. Suzuki polymerization of 1a and 1b with the tetrahedral precursor tetrakis(4-bromophenyl)methane using Buchwald's precatalyst (SPhos Pd G2) yielded polymers P2-NHBoc and P2-SO3Neo, respectively. The utilization of a 4 M HCl solution in 1,4-dioxane enabled the removal of the Boc group and protonation of the amino group simultaneously to yield the final polymer, P2-NH3Cl. In the case of P2-SO3Neo, hydrolysis of the neopentyl group was carried out using NaN3 in DMSO and subsequent acidification with 6 M HCl resulted in the polymer P2-SO3H.Porous polymers P2-NHthesized through y see ESI. The ter3Cl and P1-SO3H, the polymer P1-PO3H2 was prepared through postsynthetic modification 3, at elevated temperatures. The mild hydrolysis of the phosphonate ester groups into phosphonic acid moieties was readily accomplished using Me3SiBr, affording the polymer P1-PO3H2 in a quantitative manner.Similar to previously reported syntheses of P1-NHfication . The par1H and 13C NMR spectroscopy scale\" fill=\"currentColor\" stroke=\"none\">O and P\u2013O\u2013C stretching bands at 1240 and 960\u20131050 cm\u20131, respectively. The efficiency of this conversion was also reflected in the elemental analysis data scale\" fill=\"currentColor\" stroke=\"none\">O stretching band to 1140 cm\u20131 and the appearance of P\u2013O\u2013H bands in the range of 930\u20131000 cm\u20131. Complete hydrolysis of ester groups was also evidenced by the absence of P\u2013O\u2013C stretching bands. Similarly, complete removal of the Boc groups in P2-NH3Cl was unambiguously demonstrated by the disappearance of a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching band at 1713 cm\u20131 as well as the emergence of a broad N\u2013H band centered around 3345 cm\u20131. In the case of P2-SO3H, absorption bands at 960 cm\u20131 (S\u2013O\u2013C stretching) and at 1178 and 1350 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">O stretching) were replaced by bands at 996 and 1020 cm\u20131 (S\u2013OH) and 1150 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">O), respectively. Finally, the disappearance of C\u2013H stretching bands in the 2900\u20133000 cm\u20131 region also indicated the removal of neopentyl groups.The formation of porous polymers incorporating protected Br\u00f8nsted acidic groups and their subsequent hydrolysis was confirmed by Fourier transform infrared (FTIR) spectroscopy 1H NMR spectroscopy and cross-polarization magic angle spinning (CP/MAS) 13C NMR spectroscopy. Acidic protons appear as sharp, narrow peaks, especially in the cases of P1-PO3H2, P2-SO3H, and P2-CO2H in the solid-state MAS 1H NMR spectra, reflecting the high mobility of acidic protons in these materials was found to be 1.4 in P1-NH3Cl, while the number of \u2013SO3H and \u2013PO3H2 groups was lower in P1-SO3H (0.8) and P1-PO3H2 (0.7), respectively.Elemental analyses verified polymer conversion efficiency, with good agreement between experimental and calculated compositions in this series might be attributed to the presence of the sterically encumbering Boc groups used in the synthesis of the P2-NHBoc precursor, which could reduce the degree of interpenetration.25Surface area and porosity analyses were carried out using nitrogen gas adsorption isotherms collected at 77 K. Pore size distributions were calculated from the adsorption branch of isotherms employing a quenched solid-state DFT (QSDFT) model, which takes surface heterogeneity into account and assumes the presence of a mixture of slit, cylindrical, and spherical pores. All polymers display type I reversible isotherms, as typically observed for microporous materials are consistently higher than those for P2 polymers (<0.5 cm3 g\u20131), reflecting the influence of interpenetration in the latter frameworks. The microporosity of each sample was also further confirmed by t-plot curves , P1-NH3Cl displays an excess uptake of 0.37 mmol g\u20131 compared to 1.35 and 3.3 mmol g\u20131, for P1-SO3H and P1-PO3H2, respectively enables greater NH3 uptake at low pressures in P2-CO2H\u2014a comparison that also suggests the formation of strong binding sites with multiple weak acidic groups. At 1 bar, P2-NH3Cl and P2-CO2H display similar NH3 uptakes of 16.3 and 16.1 mmol g\u20131, respectively, whereas P2-SO3H has a lower uptake of 13.1 mmol g\u20131.Among the P1 polymers, P1-SOectively . Notably3 uptake . The NH33 concentration of 50 ppm a higher density of acidic sites, (ii) the bulkiness and flexibility of the \u2013CH2PO3H2 groups compared to \u2013SO3H groups, and/or (iii) a smaller surface area and pore volume. All of these factors render the acidic sites more proximal in P1-PO3H2 than in P1-SO3H.Perhaps more interestingly and relevant to permissible exposure limits, we now compare the uptake properties of these materials at a significantly lower NH P2-SO3H , it is c3 uptake in the cases of P1-PO3H2, P2-SO3H, and P2-CO2H can be drawn from some recent computational work.3H, it is possible that a low local polarity contributes to decreased ammonia affinity at these sites for concentrations as low as 50 ppm. Network interpenetration in the case of P2-SO3H and P2-CO2H and the reduced pore volume in P1-PO3H2 could, however, create a local dielectric polarization around each acidic site in the pores and therefore lead to stronger interactions with ammonia and enhanced capacities. Most notably, the performance of these latter materials at 50 ppm of dry ammonia is comparable to that of 5A zeolite (1.86 mmol g\u20131 at 58 ppm) and 13X zeolite (1.74 mmol g\u20131 at 41 ppm) and is significantly higher than sulfonated polymeric resin Amberlyst 15 (0.38 mmol g\u20131 at 71 ppm).26Another plausible explanation for the increased NHe.g., P1-SO3H and P2-SO3H), was compared after plotting gravimetric NH3 isotherms with respect to the number of acidic functionalities (mmol3NH mmolacid\u20131) determined by elemental analysis. The absolute pressure corresponding to the capture of one equivalent of ammonia per acid site was found to correlate well with the acid strength of functional groups within P1 and P2 was approximately 2.8 mbar.In order to gain further understanding of the NH3Cl and P2-NH3Cl, with the weakest Br\u00f8nsted acidic functionality, occurs much earlier than for the other polymers carrying sulfonic, phosphonic, or carboxylic acid groups within the same series. Also in agreement with the NH3 adsorption isotherms, P1-PO3H2 and P2-CO2H display highest uptake capacities of 5.2 and 6.7 mmol g\u20131, respectively, under dry breakthrough conditions.Under dry conditions, the trends in breakthrough saturation capacity and uptake are in excellent agreement with those obtained from gas adsorption measurements , the NH Fig. S41. Provide3H2 displays a broad desorption curve under humid conditions, the curve for P1-SO3H is rather steep ,3 uptake for these different acidic moieties. Spectral changes were also monitored upon desorption to assess the reversibility of ammonia binding.We sought to further probe the interaction of ammonia with Br\u00f8nsted acidic groups utilizing 3 adsorption the spectral changes all corresponded to those associated with the roto-vibrational profile of gaseous ammonia.We note that the parent material, PAF-1, does not exhibit any substantial spectral changes upon exposure to ammonia Fig. S37. The ini3H exhibits a series of very intense and sharp absorption bands in the 800\u20131800 cm\u20131 spectral range, which are ascribed to the vibrational modes of the aromatic structure and sulfonic acid group (\u20131 are generated by out-of-phase (\u03bdas) and in-phase (\u03bds) stretching vibrations of the SO2 group, and the OH bending mode of the S\u2013OH moiety, respectively.\u20131 region as a consequence of the formation of ammonium ions and overlaps with one of the peaks resulting from aromatic ring vibrations at 1465 cm\u20131. The absorption bands assigned to SO2 and S\u2013OH moieties in the activated material also disappear and two strong signals appear at 1035 and 1225 cm\u20131 due to \u03bds and \u03bdas modes of the newly formed sulfonate (\u2013SO3\u2013) group.3 adsorption, the sample was evacuated for 2 h at beam temperature to evaluate the reversibility of the proton transfer and \u03bds(SO2) modes of the sulfonic acid moieties could not be restored, even after prolonged outgassing.The spectrum of activated P1-SOin situ ammonia-dosed on P1-PO3H2 suggested a similar proton transfer between ammonia and phosphonic acid groups within the polymer. The activated spectrum of P1-PO3H2 exhibits typical features, in particular, strong and broad signals located at around 1000 and 1200 cm\u20131 and corresponding to P\u2013O(H) and P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching vibrations, respectively (\u03b4(NH4+) mode of the ammonium ion clearly appears as a broad component at \u223c1450 cm\u20131, while the P\u2013O and P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching modes are deeply perturbed, indicating deprotonation of one or both acidic protons scale\" fill=\"currentColor\" stroke=\"none\">O) stretching and \u03b4(C\u2013OH) bending vibrations of the carboxylic acid group, respectively (\u03b4(NH4+) mode at \u223c1458 cm\u20131 scale\" fill=\"currentColor\" stroke=\"none\">O) and \u03b4(C\u2013OH) band intensities decrease, and this change is accompanied by the appearance of two new bands at 1525 and 1378 cm\u20131 that can be ascribed to \u03bdas(OCO) and \u03bds(OCO) modes of the carboxylate (\u2013CO2\u2013) group, respectively.3H and P1-PO3H2, for P2-CO2H, the proton transfer to ammonia seems to be quite reversible (\u03b4(NH4+) and \u03bd(OCO) bands decrease dramatically and the characteristic signals of the carboxylic acid groups are partially restored.The spectrum of activated P2-CO2H upon ammonia exposure is the noticeable change in the scattering profile of the whole spectrum and one with (P2) framework interpenetration, wherein the strength of the acidic functional groups was systematically varied. Adsorption isotherms revealed that NHSupplementary informationClick here for additional data file."}
+{"text": "An efficient method for the synthesis of the NHC-stabilised Si(i) halides Si2X2(Idipp)2 was developed, which involves the oxidation of Si2(Idipp)2 (1) with 1,2-dihaloethanes. Iodide abstraction from 2-I afforded the unprecedented silicon(i) salt [Si2(I)(Idipp)2][B(C6F5)4] (3). i) halides Si2X2(Idipp)2 CH]2) was developed, which involves the oxidation of Si2(Idipp)2 (1) with 1,2-dihaloethanes. Halogenation of 1 is a diastereoselective reaction leading exclusively to a racemic mixture of the RR and SS enantiomers of 2-X. Compounds 2-Br and 2-I were characterised by single-crystal X-ray crystallography and multinuclear NMR spectroscopy, and their electronic structures were analysed by quantum chemical methods. Dynamic NMR spectroscopy unraveled a fluxional process of 2-Br and 2-I in solution, which involved a hindered rotation of the NHC groups about the Si\u2013CNHC bonds. Iodide abstraction from 2-I by [Li(Et2O)2.5][B(C6F5)4] selectively afforded the disilicon(i) salt [Si2(I)(Idipp)2][B(C6F5)4] (3). X-ray crystallography and variable-temperature NMR spectroscopy of 3 in combination with quantum chemical calculations shed light on the ground-state geometric and electronic structure of the [Si2(I)(Idipp)2]+ ion, which features a Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi bond between a trigonal planar coordinated SiII atom with a Si\u2013I bond and a two-coordinate Si0 center carrying a lone pair of electrons. The dynamics of the [Si2(I)(Idipp)2]+ ion were studied in solution by variable-temperature NMR spectroscopy and they involve a topomerisation, which proceeds according to quantum theory via a disilaiodonium intermediate (\u201c\u03c0-bonded\u201d isomer) and exchanges the two heterotopic Si sites.An efficient method for the synthesis of the NHC-stabilised Si( PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPR PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(Br)R 2}2-4-tBu) were also isolated, fortifying the binding capacity of NHCs.II halides SiX2(NHC) and SiCl(R)(NHC) CMe]2) were shown to be valuable starting materials, which paved the way to new classes of unsaturated silicon compounds, including silylidyne complexes, zwitterionic silylidene complexes, metallosilylenes and metallosilanones.11The molecular chemistry of silicon has witnessed remarkable progress in recent years following the discovery that N-heterocyclic carbenes (NHCs) are particularly suitable Lewis-bases for the thermodynamic and kinetic stabilisation of highly reactive, low-valent silicon species.i) halides (B) has not been explored so far. This can probably be attributed to the severely limited access to this very reactive class of compounds, as revealed by the very low yield synthesis (6.1%) of the only presently known example Si2Cl2(Idipp)2 (2-Cl) upon the reduction of SiCl4(Idipp) with C8K.B can be viewed as bis(NHC) adducts of the disilynes Si2R2 2 is reported, facilitating the exploration of their reactivity. Moreover, iodide abstraction from 2-I is demonstrated to provide access to an unprecedented Si(i) salt containing the NHC-trapped [Si2I]+ cation.In comparison, the chemistry of NHC-stabilised silicon scale\" fill=\"currentColor\" stroke=\"none\">Si(Idipp) (1)i) halides, analogous to the well-known olefin halogenation in carbon chemistry.2H4X2 proved to be particularly suitable reagents to accomplish this transformation. In fact, the addition of a stock solution of 1,2-C2H4X2 to a dark red solution of 1 in THF or toluene at low temperature was accompanied by a rapid color change to red-orange and gas evolution (ethene), and selectively afforded the SiI halides 2-X in moderate to very good yields compound (Idipp)Si-I: 61%) .\u2020 Precis, Br, I) , which a1 by 1,2-C2H4X2 is a highly diastereoselective cis-addition leading exclusively to a racemic mixture of the RR and SS stereoisomers of 2-X (meso diastereoisomer (trans-addition product) was found, which, according to quantum chemical calculations at the B97-D3/I level of theory,RR/SS stereoisomers by 57 kJ mol\u20131 scale\" fill=\"currentColor\" stroke=\"none\">PR (R = C(SiMe3)3) with Cl2 was reported to give exclusively the meso diastereomer.Halogenation of s of 2-X . No evidI halides 2-X was also investigated, which involved comproportionation of the Si0 compound 1 with SiX2(Idipp). Whereas no reaction between 1 and SiBr2(Idipp) was observed at room temperature, heating a 1\u2009:\u20092 mixture of 1 and SiBr2(Idipp) in toluene at 85 \u00b0C afforded the SiI bromide 2-Br, as confirmed by NMR spectroscopy. However, conversion to the comproportionation product competed with the slow decomposition of 2-Br occurring under the same conditions (vide infra), leading finally to a mixture of 2-Br, SiBr2(Idipp) and Idipp. Whereas Idipp could easily be removed, separation of 2-Br from SiBr2(Idipp) proved to be difficult due to their similar solubility preventing the isolation of 2-Br in high-yield and pure form.An alternative approach to the Sii) halides 2-X were isolated as vermillion, extremely air-sensitive solids, which immediately decolourised when in contact with air, but can be stored indefinitely at room temperature under an atmosphere of argon. Compounds 2-Br and 2-I are thermally quite robust in the solid-state and decompose upon heating at a temperature (190 \u00b0C) similar to that previously reported for 2-Cl (184 \u00b0C).2-Br starts to decompose at a much lower temperature , and the decomposition leads to Idipp, SiBr2(Idipp) and an unknown toluene-insoluble solid bromide and iodide to be reported and were comprehensively characterised by single-crystal X-ray crystallography, NMR spectroscopy and quantum chemical calculations.Compounds n-hexane semisolvates 2-Br\u00b70.5(n-C6H14) and 2-I\u00b70.5(n-C6H14) were determined by single-crystal X-ray diffraction (2-X (X = Cl\u2013I) feature two stereogenic trigonal pyramidal silicon centers of the same configuration and display similar bonding parameters \u00b0,22-Br: \u201346.81(4)\u00b0, 2-I: 50.46(3)\u00b0) and CNHC\u2013Si\u2013Si\u2013CNHC torsion angles (2-Cl: \u2013162.9(3)\u00b0,22-Br: 161.5(1)\u00b0, 2-I: \u2013160.31(9)\u00b0), respectively (DP = 70\u201378%) (2-X compared to those in SiX2(Idipp), which was confirmed by comparative NBO analyses (2(Idipp) by the more electropositive substituent SiX(Idipp).2-X (2-Cl: 2.393(3) \u00c5,22-Br: 2.385(1) \u00c5, 2-I: 2.3909(9) \u00c5) are slightly longer than that in \u03b1-Si (2.352 \u00c5)I compounds C (2.413(2) \u00c5 and 2.489(2) \u00c5)D (2.331(1) \u00c5) at the silicon atoms .20 This 2(Idipp) . These t31(1) \u00c5) .14 Remar29Si{1H} NMR spectra in C6D6, the SiI halides display a characteristic singlet signal , which appears at a lower field than that of the corresponding Si(ii) halides SiX2(Idipp) .versus the N-heterocyclic rings and 13C (75.47 MHz) NMR signals of 2-Br were sharp at 298 K, several signals of 2-I were broadened under the same conditions, suggesting a dynamic behavior = 228 K; 2-I: \u0394G\u2260 = 51 kJ mol\u20131, Tc = 248 K).In the HC atoms . The 1H ic rings , which, 2-X contain many reactive sites for further functionalisation with the most appealing ones being the displacable halide and Idipp groups, which are not available in the silicon(i) congeners C and D (2O)2.5][B(C6F5)4] to a solution of 2-I in fluorobenzene at ambient temperature was accompanied by a colour change from bright to dark red and precipitation of LiI. Iodide abstraction from 2-I selectively afforded the disilicon(i) salt [Si2(I)(Idipp)2][B(C6F5)4] (3), as evidenced by NMR spectroscopy of the crude reaction mixture ) in 62% yield, and was comprehensively characterised.Compounds C and D . First r mixture . The sal3\u00b7(C6H5F) is an extremely air-sensitive solid, which is instantly degraded by air to a colourless powder. It is stable in THF-d8 solution for several days under strict exclusion of air, and decomposes upon heating in a sealed glass capillary tube under vacuum at 208 \u00b0C.Compound 3\u00b7(C6H5F) was determined by single-crystal X-ray diffraction and it is composed of well separated [Si2(I)(Idipp)2]+ and [B(C6F5)4]\u2013 ions.2(I)(Idipp)2]+ feature a trigonal planar coordinated Si1 atom (sum of the bond angles at Si1 = 359.7(1)\u00b0) and a two-coordinate Si2 atom with V-shaped geometry (Idipp atoms (C1 and C28). The Si\u2013Si bond of 3\u00b7(C6H5F) is considerably shorter (2.1739(9) \u00c5) than the Si\u2013Si single bond of 2-I (2.3909(9) \u00c5), and also shorter than the Si\u2013Si double bond of 1 (2.229(1) \u00c5), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi bond lengths.2(I)(Idipp)2]+ (vide infra). The bulky NHC groups are trans-arranged at the Si\u2013Si double bond (torsion angles: C1\u2013Si\u2013Si2\u2013C28 = \u2013178.5(1)\u00b0 and I\u2013Si1\u2013Si2\u2013C28 = \u20136.71(9)\u00b0) and orthogonally oriented with respect to the planar core of the cation.1 (Si\u2013Si\u2013CNHC = 93.37(5)\u00b0), PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPR \u00b0) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(Br)R 2}2-4-tBu; Si\u2013Si\u2013CNHC = 97.6(1)\u00b0).2(I)(Idipp)2]+, which indicates the presence of a stereochemically active lone-pair in an orbital of high s-character (77%) and Si2 hybrid orbitals of high p-character employed for the \u03c3-bonding to the Si1 atom and the NHC group scale\" fill=\"currentColor\" stroke=\"none\">SiTip2 (2.4520(7) \u00c5, Tip = C6H2-2,4,6-iPr3),2-I (Si1\u2013I1: 2.6036(6) \u00c5; Si2\u2013I2 2.5919(6) \u00c5) compared to that in 2-I (4%), and this is also reflected in the Si\u2013I Wiberg bond indexes (3: WBI (Si\u2013I) = 0.89; 2-I: WBI (Si\u2013I) = 0.78) (see NHC bond lengths of 3\u00b7(C6H5F) (1.901(2) and 1.931(2) \u00c5) have similar values to those of 2-I (1.943(2) \u00c5 and 1.939(2) \u00c5) and 1 (1.927(2) \u00c5) (2The solid-state structure of geometry . The two19(6) \u00c5) . This tr.78) see . The Si\u201327(2) \u00c5) .2a2(I)(Idipp)2]+ with the related cations [Si2(H)(Idipp)2]+ and [Si2(Me)(Idipp)2]+, the NHC-stabilised disilavinylidenes, the NHC-stabilised disilynes and the disilenide anions scale\" fill=\"currentColor\" stroke=\"none\">Si bond lengths and similar bond angles at the two-coordinate Si atom in THF-d8 revealed an interesting dynamic process leading to an exchange of the heterotopic Si sites. The degenerate isomerisation (topomerisation)via a NHC-stabilised disilaiodonium ion at 203 K (1H NMR spectrum of 3\u00b7(C6H5F) at 203 K displays a double set of resonance signals for the chemically different Idipp groups at 203 K shows a double set of signals for the inequivalent Idipp groups , which merge into one set of signals at 298 K are compatible with the results of the single-crystal X-ray diffraction and show an averaged Cs-symmetric structure of the cation [Si2(I)(Idipp)2]+ with fast rotating NHC substituents about the respective Si\u2013CNHC bonds.33Thus, two well separated at 203 K , right, regime) , right. 98 K see . Likewis4,5-H ring protons in the temperature range of 203\u2013263 K (k/T) against 1/T afforded a linear relationship (see Section 3 in the ESIR2 = 0.9966) and were found to be \u0394H\u2260 = 47.3 (\u00b10.7) kJ mol\u20131, \u0394S\u2260 = 1.39 (\u00b13.0) J K\u20131 mol\u20131 and \u0394G\u2260 (Tc = 235 K) = 47.0 (\u00b11.4) kJ mol\u20131.The rate constants of the dynamic process were determined by full line-shape analyses of the signals of the N-heterocyclic C03\u2013263 K . An Eyri2(I)(Idipp)2]+ was studied by quantum chemical calculations at the B97-D3/I level of theory3\u00b7(C6H5F) observed in solution. Geometry optimization of [Si2(I)(Idipp)2]+ afforded a \u201c\u03c3-bonded\u201d minimum structure with an excellent agreement between the calculated and the experimental bond lengths obtained for 3\u00b7(C6H5F) by single-crystal X-ray crystallography of the cation + , which lies at an energy 37.6 kJ mol\u20131 higher than the overall minimum structure calc3 . The most striking bonding parameters of calc3\u2032 are the elongated Si\u2013Si single bond (2.463 \u00c5), which is considerably longer than the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi bond of calc3 (2.171 \u00c5), as well as the Si\u2013I bonds (2.696 \u00c5), which are longer than that of calc3 (Si\u2013I: 2.502 \u00c5). These bonding parameters suggest that calc3\u2032 can be better described as a NHC-stabilised disilaiodonium ion2(Idipp)2 (1) \u03c0-complex of I+. Notably, the structure of calc3\u2032 is reminiscent of those of the symmetrical 1,2-bridged halonium ions, which have been extensively studied in organic chemistry.35Furthermore, a \u201c\u03c0-bonded\u201d . The twore 3calc . The tra2(I)(Idipp)2]+ with those of the NHC-stabilised disilavinylidene (SIdipp)Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi(Br)R 2}2-4-tBu)4)RSi PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiR (IMe4 = C[N(Me)CMe]2, R = SiMe3)\u2013 (R = singly bonded substituent). In all cases, the HOMO is the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0-bonding orbital, which is followed by the lone-pair orbital at the two-coordinate Si atom (HOMO\u20131) (2(I)(Idipp)2]+ was analysed by the natural bond orbital (NBO) method and natural resonance theory (NRT) (see 2(I)(Idipp)2]+ scale\" fill=\"currentColor\" stroke=\"none\">Si, Si\u2013CNHC, and Si\u2013I bonds scale\" fill=\"currentColor\" stroke=\"none\">Si bond of calc3 and the high occupancies of its NBO lead to a high Wiberg bond index (WBI) of 1.81, which is twice as large as the WBI of the Si\u2013Si single bond of calc3\u2032 (0.89) and 2-I (0.96). These findings verify the presence of a Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi bond in the \u201c\u03c3-bonded\u201d isomer and a Si\u2013Si single bond in the \u201c\u03c0-bonded\u201d isomer of [Si2(I)(Idipp)2]+ or in 2-I, and are further confirmed by the NRT Si\u2013Si bond orders, which, in the case of calc3, is twice as large or 2-I (0.93) carries a lone pair of electrons in an NHO with high s-character (Idipp)2]+.A comparison of the frontier Kohn\u2013Sham orbitals of the ion +, as evidenced by the overall NPA charges of the NHCs (Si1-bonded: q(\u2211(NHC)) = 0.41; Si2-bonded: q(\u2211(NHC)) = 0.28) .i) halides Si2X2(Idipp)2 was developed, which involved a diastereoselective halogenation of Si2(Idipp)2 (1) with 1,2-dihaloethanes. This allowed the isolation of the first silicon(i) bromide (2-Br) and silicon(i) iodide (2-I) in high yield, enabling first reactivity studies of 2-I. The geometric and electronic structures of 2-Br and 2-I were comprehensively studied by experimental and theoretical methods. Iodide abstraction from 2-I selectively afforded the unprecedented disilicon(i) iodido salt [Si2(I)(Idipp)2][B(C6F5)4] (3), the geometric and electronic structure of which is isolobal to that of a NHC-stabilised disilavinylidene recently reported by our group. The topomerisation of the cation [Si2(I)(Idipp)2]+, leading to an exchange of the two heterotopic Si sites, was studied by variable-temperature NMR spectroscopy and the underlying dynamic process was analysed by quantum chemical calculations. The calculations suggest the intermediate formation of a C2-symmetric \u03c0-bonded isomer with homotopic Si sites reminiscent of the symmetrical 1,2-bridged halonium ions in organic chemistry. The present results corroborate the ability of N-heterocyclic carbenes to stabilise low-valent main-group element centers with unusual bonding features. Further studies addressing the reactivity of the NHC-stabilised Si(i) halides 2-X and the SiI salt 3 are currently underway.An efficient method for the synthesis of silicon(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The monomeric molecular aluminium(i) complex 1 [{(ArNCMe)2CH}Al] reacts with a series of terminal and strained alkenes including ethylene, propylene, allylbenzene and norbornene to form alkene bound products. i) complex 1 [{(ArNCMe)2CH}Al] reacts with a series of terminal and strained alkenes including ethylene, propylene, allylbenzene and norbornene to form alkene bound products. Remarkably all these reactions are reversible under mild conditions (298\u2013353 K) with alkene binding being disfavoured at higher temperatures due to the positive reaction entropy. Van't Hoff analyses have allowed quantification of the binding events with . Calculations and single crystal X-ray diffraction studies are consistent with the alkene bound species being metallocyclopropane complexes. Alkene binding involves a reversible redox process with changes from the +1 to +3 aluminium oxidation state. Under more forcing conditions the metallocyclopropane complexes undergo non-reversible allylic C\u2013H bond activation to generate aluminium(iii) allyl hydride complexes. This represents a rare example of redox-based main group reactivity in which reversible substrate binding is followed by a further productive bond breaking event. Analysis of the mechanism reveals a reaction network in which alkene dissociation and reformation of 1 is required for allylic C\u2013H activation, a realisation that has important implications for the long-term goal of developing redox-based catalytic cycles with main group compounds.The monomeric molecular aluminium( In 2009, following an unusual account of stannylene binding to a strained alkyne,i) reagent 1, first prepared by Roesky and co-workers,i) complex is necessary to liberate the reactive site and Frontier molecular orbitals involved in an intermolecular C\u2013H activation step. Our findings not only represent an important advance in transition metal mimetic behaviour of main group complexes, they also demonstrate the complementary mechanistic aspects of these two research fields.In this paper, we show that the aluminium(i) complex 1, known to activate a series of small molecules,2a complex and alkene binding as a redox process involving reversible oxidative addition and reductive elimination steps. In an effort to expand the scope of alkene binding the reaction of 1 with a series of simple and industrially relevant alkenes was investigated , propylene (1 bar), hex-1-ene, 3,3-dimethyl-1-butene (10 equiv.), allylbenzene (10 equiv.) and 4-allylanisole (10 equiv.) in C6D6 led to the formation of compounds 2b, 2c, 2d, 2e, 2f and 2g respectively. For example, 2b formed within 15 minutes at 298 K and the characteristic deep orange colour of 1 in benzene solution was seen to intensify upon alkene binding. In the 1H NMR spectrum, a new singlet peak is observed at \u03b4 = 0.67 ppm corresponding to the four protons of the newly formed and highly symmetric metallocyclopropane moiety of 2b. In all other cases, the 1H NMR data reflect the asymmetric nature of the metallocycle derived from substituted terminal alkenes. In 2f, magnetically and chemically inequivalent protons of the metallocyclopropane resonate at \u03b4 = 0.31 , 0.93 ppm (m) and 1.03 (m) ppm.The reaction of 1H NMR spectroscopy data on isolated samples of 2a\u2013f, remarkably in all cases alkene binding was found to be reversible. Although the metallocyclopropane is the dominant species in hydrocarbon solutions , the position of the equilibrium was found to be dependent on the nature of the alkene. At 298 K, in toluene-d8, 2a equilibrated to <1% of 1 and the non-coordinated alkene, whereas significantly more of 1 was observed to form from 2d center of 2a\u2013g compared to the Al(i) center of 1.Compounds lengths are all 1 there is an 18\u201321% increase in the C\u2013C bond length compared to the parent alkenes.3(\u03b72-CH2CH2)][K] the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond of bound ethylene elongates by 3% compared to that in free ethylene.2(\u03b72-CH2CH2)].1 and related main group systems,e.g. F, Cl, CF3, CN) to late transition metals. In these instances, back-donation from metal d-orbitals to the \u03c0*-orbital of the alkene is the dominant factor in bonding and alkene coordination can be conceptualised in terms of an oxidative addition to the transition metal.Upon ethylene or norbornene binding to 2b dimerises to form 3, a product which incorporates a bimetallocyclohexane ring confirm that 3 is thermodynamically favorable relative to 2 equiv. of 2b . The formation of 3 is non-reversible. While a series of related compounds were previously reported from the reaction of terminal alkenes with a bimetallic gallium complex, in this instance a metallocyclopropane intermediate could not be observed.2b to form 3 remains unclear and although it is tempting to suggest that this involves a simple bimolecular reaction of 2 equiv. of 2b, at this point the reversible formation of 1 as a reaction intermediate cannot be excluded (vide infra).In the presence of an excess of ethylene, ane ring . This difraction and DFT 2c, in the presence of excess alkene, at 353 K in C6D6 led to the loss of the dark orange colour and formation of the allylic C\u2013H activation product 4c and single crystal X-ray structure of 4f, which clearly showed the geometry of the double bond in the chain failed to provide any evidence for the reformation of 1.Further experiments showed that the formation of these C\u2013H activation products is non-reversible and that accessible allylic sp3 C\u2013H bonds of propene have a bond dissociation energy of 88.8 \u00b1 0.4 kcal mol\u20131 and while more reactive than those in propane, they are still challenging bonds to break with metal complexes.4 and 1 respectively has been reported and in the former case shown to be a reversible redox process.1 reacts with the C\u2013H bonds of benzene but only in the presence of a palladium catalyst.47The allylic sp1 in benzene-d6 was reacted with a 5 equiv. of allylbenzene, with full formation of 2f observed after 1 hour. The solution was heated to 343 K and monitored by 1H NMR spectroscopy over the course of 4 hours. Immediate formation of 4f was observed, along with small amounts of unreacted 1. Complex 1 remained present in low, but steady, concentration (<5%) throughout the reaction, suggesting that it may be a potential intermediate in C\u2013H activation.Kinetic data was obtained and modelled with Copasi software. These experiments were undertaken as a means to gain insight in to the reaction mechanism and establish the activation parameters for the C\u2013H activation step. A 0.018 M solution of 2f to 4f did not lead to reasonable activation parameters. The system was considered as an equilibrium between 1 and 2f, with non-reversible conversion of 1 to 4f (k\u20131/k1 = 0.056) and the irreversible C\u2013H activation (k2 = 3.0 \u00d7 10\u20133 s\u20131) at 343 K. An alternate kinetic model exists. The reaction network could also be considered as an equilibrium between 1 and 2f with non-reversible conversion of 2f to 4f. While the two kinetic scenarios involving a pre-equilibrium step cannot be differentiated from one another experimentally, calculations provide unambiguous support for the involvement of 1 as an intermediate and show that the direct conversion of 2f to 4f is in fact unfavourable (vide infra).Attempts to fit the data using pseudo-first order kinetics as a conversion from 1 to 4f . Copasi 1 to 4f, k2) yielded the activation parameters and , with a Gibbs activation energy of \u0394G\u2021298 K = 20.5 kcal mol\u20131 .Eyring analysis of the C\u2013H activation reaction over the temperature range 343\u2013363 K calculations were conducted using the hybrid basis set 6-31G**/SDD. A series of functionals were investigated and the M06L functional was found to best model the structural and thermodynamic parameters determined from experiment . At the same time the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC Wiberg bond indices decrease , while those of the Al\u2013C bonds increase . Endo-TS-1 is asymmetric being characterised by not only the displacement of the Al atom out of the plane of the \u03b2-diketiminate ligand but also two distinct Al\u00b7\u00b7\u00b7C distances which differ by \u223c0.3 \u00c5 scale\" fill=\"currentColor\" stroke=\"none\">C \u03c0-bond to the vacant p-orbital on Al with concomitant back-donation from the Al sp2 lone pair to the \u03c0* orbital of the alkene (vide infra).As the simplest substrate to undergo both binding and C\u2013H activation, propylene was made the focus of these studies. Alkene binding was determined to take place through an asynchronous concerted pathway involving two closely related transition states, ex Int-1 . NBO anay \u223c0.3 \u00c5 . Similar1. This pathway proceeds by TS-2 with an activation barrier of \u0394G\u2021 = 24.3 kcal mol\u20131. The energies of TS-1 and TS-2 are consistent with the metallocyclopropane 2c being formed as the kinetic product which ultimately converts to the thermodynamic product 4cvia reformation of 1. Formation of 4c is non-reversible and proceeds in an exergonic step, . In TS-2, propylene develops the character of an allylic ligand as it undergoes C\u2013H activation. The Al\u00b7\u00b7\u00b7H bond length (1.93 \u00c5) and C\u00b7\u00b7\u00b7H bond length (1.39 \u00c5) are consistent with a late transition state. The allylic character is evidenced by a the relatively short interaction between Al and the terminal alkene carbon of the propylene moiety (2.19 \u00c5). The NPA charge of Al increases as the C\u2013H bond breaks, consistent with an oxidative addition . IRC calculations confirm that TS-2 does not evolve from 2c, but instead is the result of C\u2013H activation directly from 1 and free propylene.A low energy activation pathway was identified involving intermolecular oxidative addition of the C\u2013H bond of propylene to iii) complex 2c could not be identified at this level of theory. This latter reaction pathway involves a \u03b2-hydride elimination step known to operate for simpler three coordinate aluminium(iii) alkyls at high temperatures,2 \u2192 4 could be identified and compared with that of 1 \u2192 4. With the \u03c9B97x functional, a hybrid basis-set adapted for solvent and dispersion (\u03c9B97xD) by single point corrections, the transition state for \u03b2-hydride elimination of 2f was located and found to be obstructively high in energy >40 kcal mol\u20131. For comparison at the same level of theory TS-2 is \u0394G\u2021 = 27.1 kcal mol\u20131. Related \u03b2-fluoride elimination pathways have been modelled in these systems and are lower in energy likely due to a large ionic component to Al\u2013F bonding and the fluorophilicity of the Al3+ ion.37A pathway for the direct intramolecular C\u2013H activation of the bound propylene of the aluminium(trans-4f was observed as the sole reaction product over a 343\u2013363 K temperature range. Comparison of the C\u2013H activation transition states explains the regioselectivity. The Gibbs free energy (at 298 K) for the transition state for the formation of trans-4f was \u223c3 kcal mol\u20131 lower in energy than the TS that leads to cis-4f, likely due to 1,3-allylic strain (A-strain) induced as the hydrogen atom is transferred to aluminium and the hydrocarbon ligand starts to adopt alkene character of 1 consist of a vacant 3p orbital (LUMO) and an orthogonal sp2-hybridised lone-pair (HOMO). Alkene binding proceeds via an asymmetric transition state that involves overlap of the fMOs of 1 with those of the unsaturated C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond reversible alkene binding to form a metallocyclopropane and (ii) direct intermolecular C\u2013H activation, C bond . The resH \u03c3-bond .i) centre, along with an extremely rare case of a reaction sequence involving reversible substrate binding and C\u2013H activation at a main group fragment. The simple realisation that the fMOs of aluminium(i) required for alkene binding are also those required for C\u2013H activation has broad implications for the development of catalytic cycles.In summary, we report the first examples of reversible alkene binding to an aluminium only allow for binding or activation of a single substrate at a time. In contrast, for transition metal catalysts often several d-orbitals of suitable energy and symmetry are unoccupied. Most transition metal based redox catalytic cycles involve the coordination or activation of two substrates , bringing them into close proximity and facilitating bond formation.Low-valent main group species with small HOMO\u2013LUMO gaps are often targeted as a first step to develop redox catalysis, but the reality is that the most common designs hemi-labile ligands to open up coordination sites on the main group fragment, or (ii) integration of redox steps with more common pathways of main group compounds such as hydroelementation, \u03c3-bond metathesis and nucleophilic addition.The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The design of novel heterogeneous catalysts with multiple adjacent functionalities is of high interest to heterogeneous catalysis. N-phenylsilanamine\u2013silanol pairs. In contrast with ammonia treated surfaces, the material is stable under air/moisture. Advanced solid state MAS NMR experiments and dynamic nuclear polarization enhanced 29Si and 15N spectra demonstrate both the close proximity between the two moieties and the formation of a covalent Si\u2013N surface bond and confirm the design of vicinal acid\u2013base pairs. This approach was successfully applied to the design of a series of aniline derivatives of bifunctional SBA15. A correlation between the substituent effects on the aromatic ring (Hammett parameters) with the kinetics of a model Knoevenagel reaction is observed.The design of novel heterogeneous catalysts with multiple adjacent functionalities is of high interest to heterogeneous catalysis. Herein, we report a method to obtain a majority of bifunctional acid\u2013base pairs on SBA15. Aniline reacts with SBA15 by opening siloxane bridges leading to One of the major current challenges in heterogeneous catalysis is the ability to develop multifunctional catalyst systems where each active site plays a distinct role in the overall catalytic process (cascade approach). To date, two main approaches to introduce functionalities into mesoporous materials exist: the soft templating strategy for the synthesis of organic\u2013inorganic hybrid materialsvia an alkyl spacer, can be randomly distributed or organized.In the soft templating method, the inorganic materials provide the surface area and the porosity. The organic active site, linked to the surface via a multistep mechanism. However, the surface\u2013complex bond is usually a \u03c3-bonded oxygen ligand, e.g., siloxy [ scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013)MLn], with M = metal and L = ligands, in the primary coordination sphere and the requirement for oxygen limits the development of SOMC methods. It would then be highly desirable to tune the coordination sphere of the metal center by designing surface ligands in close proximity to the surface to preserve the rigidity of the ensemble \u201csurface ligand/complex\u201d. By tuning the electronic and/or steric properties of the surface ligand, new catalysts and new reactions will be discovered.In the SOMC methodology,via treatment with ammonia, by analogy with the ring opening of epoxides by ammonia. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013NH2] surface groups is associated with experimental, economical and safety disadvantages, such as the need for a high flow rate (200 mL min\u20131) of pure, expensive and corrosive ammonia, and the resulting materials being moisture sensitive. Aside from that, further chemical modifications of SBA15 to offer opportunities to provide tunable steric and electronic properties were impossible without affecting the structural parameters of the materials. To face these issues, we investigate an alternative approach based on the chemisorption of dry aniline onto highly dehydroxylated SBA15 (1100 \u00b0C), which has never been reported and its large and uniform pore diameter (6 nm) and relatively thick walls (3 to 6 nm).\u20135 mbar) yields the condensation of adjacent silanols and generates a support that contains a surface of mainly strained siloxanes along with a small amount of isolated silanols (<0.4 OH per nm2).1100 with dry aniline was performed in a solution in toluene at 80 \u00b0C for 20 h. The resulting material 1 was evacuated at room temperature overnight under high vacuum (10\u20135 mbar) and characterized by FT-IR spectroscopy. Comparison of the FT-IR spectra of SBA151100 and 1 (\u03bds(OH)] band with a red shift from 3748 to 3745 cm\u20131. Additionally, the typical single sharp infrared bands characteristic of secondary amines,N-phenylsilylamine appears at 3435 and 1500 cm\u20131. They correspond to the [\u03bd(NH)] and [\u03b4(NH)], respectively. Vibrational bands of the aromatic group are clearly visible at 3089\u20133023 cm\u20131 [\u03bd(CH)], at 1606 and 1500 cm\u20131 [\u03b4 scale\" fill=\"currentColor\" stroke=\"none\">C)] (overlap a NH band). Finally, the shoulder in the range of 3690\u20133585 cm\u20131 is assigned to electronic interactions of the \u03c0 system of the aromatic group with the newly formed adjacent silanol (\u03c0\u2013OH interactions).\u20131 assigned to the N\u2013H stretching vibration of physisorbed aniline.Well-ordered hexagonal mesoporous silica, SBA15, was chosen as a support because of its high thermal stability (up to 1200 \u00b0C), its high surface area spectrum scale\" fill=\"currentColor\" stroke=\"none\">SiOH proton. Its value appears slightly downfield compared to the chemical shift of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiOH (1.7 ppm) generated by treatment with ammonia. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013NH\u2013Ph.43Solid state NMR was used to characterize the pairwise nature of the atomic-level organization of the supported organic functionalities, spectrum shows foortho (Ho) and para (Hp) positions. The proton in the meta position (Hm) appears at 7 ppm NMR spectrum scale\" fill=\"currentColor\" stroke=\"none\">SiOH at 1.9 ppm and the proton resonance of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNHPh at 3.4 ppm [5.3 ppm in F1: \u03b4H(OH) + \u03b4H(NH) = 1.9 + 3.4] scale\" fill=\"currentColor\" stroke=\"none\">SiOH and the aromatic proton resonances of the neighboring PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNHPh at 6.6 ppm [8.5 ppm in F1: \u03b4H(OH) + \u03b4H(Ho) = 1.9 + 6.6] scale\" fill=\"currentColor\" stroke=\"none\">SiNHPh at 3.4 ppm and the proton of the aromatic ring in ortho position Ho at 6.6 ppm [10 ppm in F1: \u03b4H(OH) + \u03b4H(Ho) = 3.4 + 6.6] scale\" fill=\"currentColor\" stroke=\"none\">SiOH] (1.9 \u00d7 2 = 3.8 ppm in F1) as well as between two (2 \u00d7 3.4 = 6.8 ppm in F1) are observed clearly demonstrates that the majority of sites are isolated \u201cacid\u2013base\u201d pairs : .Interestingly, the fact that no correlations between two silanols , with E = Si or H (commonly dubbed Q4 and Q3) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNHPh].52Dynamic nuclear polarization surface enhanced NMR (DNP SENS)rum of 1 displays15N DNP SENS spectrum shows a single peak at 66 ppm in the 2\u03b8 range of 0.7\u20134\u00b0. They confirm the presence of a well-ordered hexagonal mesophase with a d100 spacing of 86.28 \u00c5 , and Transmission Electronic Microscopy (TEM). The small angle X-ray diffraction patterns of 1 of approximately 512 m2 g\u20131 (versus 679 m2 g\u20131 for SBA1100) and pore volumes of 0.65 cm3 g\u20131 (versus 0.9 cm3 g\u20131 for SBA1100). Also, 1 showed type IV isotherms and the dissociative chemisorption of aniline , the mesoporous structure is still regular over the whole particle of 1.Further evidence for a well-ordered hexagonal mesostructure is provided by the TEM images , which aKa = 13) scale\" fill=\"currentColor\" stroke=\"none\">C bond forming reactions. It produces several important key intermediates such as \u03b1, \u03b2 unsaturated products widely used for the synthesis of therapeutic drugs, functional polymers and fine chemicals.A materials with atomic organization of acid\u2013base pairs should exhibit cooperative catalytic behavior for the Knoevenagel condensation of benzaldehyde with diethyl malonate (pKa = 13) .55\u201357 Thet al. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013OH are capped with trimethylsilyl group scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013OSiMe3). So, weakly acidic silanols play a vital role in the cooperative catalytic cycle as well as the spatial organisation of the acid\u2013base functionalities.In the literature, several studies have revealed an efficient catalysis by cooperative acid\u2013base pairs well organized on mesoporous silica.1H-MAS solid state NMR spectroscopy (3745 cm\u20131), \u03bd(NH) and \u03b4(NH), 3435 and 1500 cm\u20131 respectively. Vibrational bands of the aromatic group are still present at 3089\u20133023 cm\u20131 [\u03bd(CH)], at 1606 and 1500 cm\u20131 [\u03b4 scale\" fill=\"currentColor\" stroke=\"none\">C)] (overlapping a NH band). The shoulder characteristic of the electronic interactions of the \u03c0 system of the aromatic group with the newly formed adjacent silanol (\u03c0\u2013OH interactions) in the range of 3690\u20133585 cm\u20131 is again observed for all catalysts .All the FT-IR spectra of catalysts 1H NMR spectra feature the characteristic signal of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiOH and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNH at around 2 ppm and 3.5\u20133.9 ppm, respectively. As expected, the protons in ortho and meta position to electron donating (OMe) and electron withdrawing substituents show distinct upfield and downfield shifts is a weaker base than catalyst (1). A chloro group in the para position is a slightly EWG, so catalyst (3) exhibits better activity than (2) and is slightly less active than (1). Introducing an electron-donating group (EDG) as a p-methoxy group in the catalyst (4) enhances the catalytic performance in the Knoevenagel reaction. Among all these catalysts, (4) exhibits the best performance whereas (5) exhibits the lowest due to the base weakening effect.Their catalytic performance were tested (6), SBA15 where primary amine and silanol groups are proximal (7).6) shows no activity as no basic sites are present. (7) contains primary amines which are supposed to be the strongest base; yet it gives only 18% conversion after 24 h. (1) and (4) yield better conversion although their basicity is lower than that of (7). These results are explained by the higher stability of these catalysts under the experimental conditions (ethanol is the solvent and water is produced during the Knoevenagel reaction). Indeed, the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNH2 group is well-known to be easily hydrolyzed.Besides this, the catalytic results of this series of acid\u2013base paired catalysts (7) and (1) towards ethanol was monitored by FT-IR spectroscopy. After 5 min in contact with ethanol, the FT-IR spectrum shows complete disappearance of the characteristic bands of the PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSiNH2 group . However the FT-IR spectrum of (1) shows the characteristic bands of PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi\u2013NHPh, [\u03bd(NH) = 3435 cm\u20131] even after 1 h in contact with dry ethanol. In addition, during the catalytic test with catalyst 1, no leaching of aniline was detected by both GC-FID and GC-MD scale\" fill=\"currentColor\" stroke=\"none\">Si\u2013O\u2013Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t) of mesoporous SBA151100. The generation of well-defined adjacent N-phenylsilanamine\u2013silanol pairs was unambiguously determined through FTIR, 2D solid state NMR, XRD, nitrogen sorption and TEM. This way to design bi-functionalized mesoporous surface offers new opportunities to modify the electronic and steric properties of mesoporous silica useful for heterogeneous catalysis.The opening siloxane bridges approach was successfully established to create an atomic organization of well-defined bi-functional acid\u2013base pairs on mesoporous SBA15. This approach is based on an analogy between organic epoxides and strained siloxanes (Supplementary informationClick here for additional data file."}
+{"text": "The \u03b2-diketiminato magnesium hydride, [(BDI)MgH]]2, reacts with alkenes and catalyses their hydrosilylation with PhSiH3. 2, reacts at 80 \u00b0C with the terminal alkenes, 1-hexene, 1-octene, 3-phenyl-1-propene and 3,3-dimethyl-butene to provide the respective n-hexyl, n-octyl, 3-phenylpropyl and 3,3-dimethyl-butyl magnesium organometallics. The facility for and the regiodiscrimination of these reactions are profoundly affected by the steric demands of the alkene reagent. Reactions with the phenyl-substituted alkenes, styrene and 1,1-diphenylethene, require a more elevated temperature of 100 \u00b0C with styrene providing a mixture of the 2-phenylethyl and 1-phenylethyl products over 7 days. Although the reaction with 1,1-diphenylethene yields the magnesium 1,1-diphenylethyl derivative as the sole reaction product, only 64% conversion was achieved over a 21 day timeframe. Reactions with the \u03b1,\u03c9-dienes, 1,5-hexadiene and 1,7-octadiene, provided divergent results. The initial 5-alkenyl magnesium reaction product of the shorter chain diene undergoes 5-exo-trig cyclisation via intramolecular carbomagnesiation to provide a cyclopentylmethyl derivative, which was shown by X-ray diffraction analysis to exist as a three-coordinate monomer. In contrast, 1,7-octadiene provided a mixture of two compounds, a magnesium oct-7-en-1-yl derivative and a dimagnesium-octane-1,4-diide, as a result of single or two-fold activation of the terminal C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bonds. The magnesium hydride was unreactive towards internal alkenes apart from the strained bicycle, norbornene, allowing the characterisation of the resultant three-coordinate magnesium norbornyl derivative by X-ray diffraction analysis. Computational analysis of the reaction between [(BDI)MgH]2 and 1-hexene using density functional theory (DFT) indicated that the initial Mg\u2013H/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion process is rate determining and takes place at the intact magnesium hydride dimer. This exothermic reaction traverses a barrier of 18.9 kcal mol\u20131 and results in the rupture of the dinuclear structure into magnesium alkyl and hydride species. Although the latter three-coordinate hydride derivative may be prone to redimerisation, it can also provide a further pathway to magnesium alkyl species through its direct reaction with a further equivalent of 1-hexene, which occurs via a lower barrier of 15.1 kcal mol\u20131. This Mg\u2013H/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion reactivity provides the basis for the catalytic hydrosilylation of terminal alkenes with PhSiH3, which proceeds with a preference for the formation of the anti-Markovnikov organosilane product. Further DFT calculations reveal that the catalytic reaction is predicated on a sequence of Mg\u2013H/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion and classical Si\u2013H/Mg\u2013C \u03c3-bond metathesis reactions, the latter of which, with a barrier height of 24.9 kcal mol\u20131, is found to be rate determining.The dimeric \u03b2-diketiminato magnesium hydride, [(BDI)MgH] Compoun2 , reacts as a dimer via highly polarised pathways, even with unactivated terminal alkenes, to provide exceptionally potent calcium alkyl nucleophiles, [(BDI)CaR]2. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE scale\" fill=\"currentColor\" stroke=\"none\">E , PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonded small molecule appears to have been described.28It has previously been shown that the \u03b2-diketiminato calcium hydride, [(BDI)CaH]E E = O, NR19\u201322 E E = O, NR26 bonNotwithstanding impressive recent advances in first row transition metal chemistry,3,6F5)3,3Si(C6H6)][B(C6F5)3],2][B(C6F5)4]\u2013 via silane hydride abstraction by the potent Lewis acid centre and sequential delivery of the silylium cation and hydride to the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC double bond.+[B(C6F5)4]\u2013 (5) as a catalyst for the hydrosilylation of alkenes and alkynes.5 is strictly isoelectronic to a monomeric unit of 4 and, although the exact details could not be elucidated, the authors suggested that the most likely mechanism involves alkene attack on an incipient silylium ion generated through hydride abstraction by the highly Lewis acidic aluminium cation scale\" fill=\"currentColor\" stroke=\"none\">C insertion into the M\u2013Si bond of a metal silanide, which is apparently formed by M\u2013C/silane metathesis in competition with the expected hydride intermediates. This supposition was vindicated by Okuda's subsequent development of several group 1 and calcium silanide and hydridosilicate species, which also yield the anti-Markovnikov products for the hydrosilylation of 1,1-diphenylethylene and similarly activated alkenes.e.g.3) may be converted to n-alkyl species by their reaction with unactivated alkenes.4 and that subsequent silane metathesis of the resultant organomagnesium species provides a basis for the hydrosilylation of C\u2013C unsaturated substrates.Hydrosilylation mediated by s-block centres was pioneered by Harder and co-workers who employed highly polar potassium, calcium and strontium benzyl species as pre-catalysts for the silane reduction of conjugated 1,1-diphenylethylene, styrene and diene substrates.1.000000,.000000 s4) and two molar equivalents of 1-hexene at 80 \u00b0C. Monitoring by 1H NMR spectroscopy over a period of 4 hours evidenced complete consumption of the starting materials and the production of a single new base-free \u03b2-diketiminato n-hexyl magnesium derivative , similar thermal treatment of both 3-phenyl-1-propene and 3,3-dimethyl-1-butene indicated that the facility of these C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion reactions is significantly perturbed by the relative steric demands of the alkene substrate. In these latter cases, reactions at 80 \u00b0C between compound 4 and the unsaturated organic reagents required 2 days and 21 days to achieve complete conversion to the respective magnesium 3-phenyl-propyl (8) and 3,3-dimethyl-1-butyl (9) complexes, which were nevertheless isolated in analytically pure form.The successful synthesis of compound alkenes . Althoug4 with both styrene and 1,1-diphenylethene. Whereas the terminal hydride derivative 1 was reported to react readily with styrene within 2 hours at room temperature to yield compound 2 and 1-phenylethyl (10B) complexes, resulting from either 1,2- or 2,1-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion, respectively. This noteworthy kinetic effect was exacerbated by the introduction of additional phenyl substitution. Despite benefitting from the benzhydrylic substitution pattern that has previously been observed to greatly facilitate analogous reactions with molecular calcium hydrides,4, requiring 6 weeks at 100 \u00b0C to achieve 64% conversion to the 1,1-diphenylethyl complex (11). Although pure bulk samples of compounds 10A/B and 11 could not be isolated, the structures of these organomagnesium derivatives were assigned with a high degree of certainty by in situ studies of the two reactions by 1H and 13C{1H} NMR spectroscopy.These observations were underscored by the reactions of mpound 2 ,11 a sim3) with both 1,5-hexadiene and 1,7-octadiene proceed via initial formation of the respective open chain 5-alkenyl and 7-en-1-yl derivatives. The shorter chain species is rapidly consumed, however, through an intramolecular carbocalciation reaction to provide an isolable calcium cyclopentylmethyl derivative.4 at 80 \u00b0C similarly resulted in complete and selective conversion to a single new compound, which was identified as the magnesium cyclopentylmethyl derivative (12) resulting from facile 5-exo-trig cyclization and the dimagnesio-octane-1,4-diide (14) were formed in effectively equimolar quantities through complete consumption of the hydride reagent at 80 \u00b0C over the course of 5 hours. Although compounds 13 and 14 proved to be inseparable, irrespective of variations in the reaction stoichiometry, the compounds could be readily discriminated by both 1H and 13C NMR spectroscopy.A similar reaction performed between compound closure . Rather,3),4 was found to be completely unreactive towards the internal alkenes, 2,3-dimethyl-2-butene, cyclopentene and cyclohexene but to react smoothly, albeit slowly, with both the strained bicyclic alkene, norbornene (3 days at 80 \u00b0C) and the internal alkyne, diphenylacetylene (6 days at 80 \u00b0C), to provide the magnesium norbornyl (15) and (E)- (16) derivatives. Although monitoring of the reaction with norbornene revealed tentative evidence that the production of 15 occurs via the formation of a dinuclear hydridonorbornyl-dimagnesium intermediate and norbornene,15) was found to be thermally stable allowing its isolation in high (>90%) yield. The formation of compound 15 was signified in its 1H NMR spectrum by a new BDI methine singlet at \u03b4 4.93 ppm and a characteristic upfield doublet of doublets of doublets signal at \u03b4 \u20131.31 ppm, which emerged in a 1\u2009:\u20091 ratio by integration. The constitution of compound 16 was readily established by 1H NMR spectroscopy through the appearance of new BDI methine and vinylic C\u2013H singlet resonances, each of which developed simultaneously and with identical 1H integrals at \u03b4 4.93 and 5.85 ppm. Compound 15 was also characterised by single crystal X-ray diffraction analysis scale\" fill=\"currentColor\" stroke=\"none\">C insertion mechanism was provided by density functional theory (DFT) calculations carried out with the same computational approach scale\" fill=\"currentColor\" stroke=\"none\">C insertion profile shown in H = \u201314.1 kcal mol\u20131) 1-hexene insertion takes place into the dimeric magnesium hydride, 4(A), via an accessible barrier of 18.9 kcal mol\u20131. For comparison, we also computed an initial insertion step on the mononuclear magnesium compound (C) to form a proximal but non-bonding pair of dissimilar three-coordinate magnesium alkyl and hydrido complexes (D) is significantly exothermic . Although the hydridic component may redimerise to 4(A), the low coordinate magnesium hydride also holds the potential to undergo a second 1-hexene insertion via an accessible barrier of 15.1 kcal mol\u20131 scale\" fill=\"currentColor\" stroke=\"none\">C insertion at 4(A) and the three-coordinate hydride generated by its monomerisation, respectively. Although this latter observation appears somewhat surprising, it is possibly ascribed to a stabilising interaction between the hexyl and hydrido complexes at the transition state (TS-EF). A transition state corresponding to the second 1-hexene insertion into the dinuclear magnesium hydride complex C could be also located led us to discard this possible pathway. The dimerisation of complex F, yielding complex F1, was computed to be endothermic by 17.0 kcal mol\u20131 allowing us to also discount this possibility. Consistent with the experimental results, therefore, the overall result of Mg\u2013H/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion may be assessed to be a facile process affording three-coordinated, mononuclear alkyl species (F).Further insight into the Mg\u2013H/Ccompound , that isal mol\u20131 . This va Fig. S36, althoug4 with C\u2013C multiple bonds, we next turned our attention to its potential to mediate catalytic hydrosilylation of alkenyl substrates with phenylsilane. An initial reaction was performed in C6D6 between 1-hexene and PhSiH3 in the presence of 5 mol% 4. Monitoring of the reaction performed at 60 \u00b0C by 1H NMR spectroscopy indicated that, although somewhat sluggish, the reaction proceeded with complete conversion to the product of anti-Markovnikov silane addition, n-hexyl(phenyl)silane, over the course of one week. An otherwise identical reaction performed at 80 \u00b0C provided similar observations but in the shorter timeframe of 4 days. We suggest that the observation of the anti-Markovnikov product is consistent with both the high regioselectivity of the stoichiometric insertion reaction to provide the terminal n-hexylmagnesium product (6) and the operation of a mechanism dependent upon a sequence of Mg\u2013H/C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion and Mg\u2013C/Si\u2013H metathesis events, which is broadly analogous to that envisioned for organolanthanide-based hydrosilylation catalysis (vide infra).Given the unexpectedly broad reactivity of compound 3 and a range of alkene substrates (3 and vinylsilanes (entries 4 and 5) were less successful, providing, at best, only stoichiometric (based on Mg) conversion to the unsymmetrical \u03b1,\u03c9-disilane product for the Ph3Si-substituted substrate (entry 4) and no evidence of any reaction for Me3Si scale\" fill=\"currentColor\" stroke=\"none\">CH2) (entry 5). In line with the expectation provided by the synthesis of compound 8, allylbenzene yielded, primarily, the anti-Markovnikov product (entry 6), while only the Markovnikov product was observed for the catalysis performed with 1,1-diphenylethene (entry 7). The observation of this latter product indicates that the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC insertion reaction is likely to be dictated by similar stereoelectronic considerations to those operant during Parkin and co-workers synthesis of compound 2 bias toward the production of the Markovnikov product, phenyl(1-phenylethyl)silane (entry 8).These deductions were borne out by a subsequent assessment of a series of catalytic hydrosilylation reactions performed with PhSiHbstrates . Consistmpound 2 . In the 3 provided an approximate 1\u2009:\u20093\u2009:\u20096 distribution of the open chain alkenylsilane, the symmetrical \u03b1,\u03c9-disilane and cyclised cyclopentylmethylsilane products (entry 9). Underlining the ease of formation of compound 12, the preponderance of this latter compound suggests that intramolecular carbomagnesiation is competitive with Mg\u2013C/Si\u2013H metathesis under the conditions of the catalysis. Similarly, although dimagnesiation of 1,7-octadiene to form compound 14 was competitive with its monomagnesiation under stoichiometric conditions, the product of its monohydrosilylation was found to predominate under the conditions of the catalysis (entry 10).The reaction of equimolar quantities of 1,5-hexadiene and PhSiH15, norbornene was the only internal alkene (entries 11\u201313) to undergo catalytic hydrosilylation in the presence of compound 4, providing the racemic exo-2-(silyl)norbornane product. The likely operation of an insertion-metathesis mechanism similar to that depicted in E)-(phenyl)silane as the sole reaction product.Consistent with the successful synthesis of compound 3 was studied by density functional theory calculations. i.e. from complex F. The associated transition state displays a classical Mg\u2013C/Si\u2013H metathesis arrangement, via a barrier of 24.9 kcal mol\u20131 (TS-GH). In accordance with the experimental observations, the hydrosilylation step is the rate determining process affording, in the case of 1-hexene, the experimentally observed anti-Markovnikov n-hexyl(phenyl)silane product exclusively. For completeness, we also computed the hydrosilylation reaction subsequent to the first 1-hexene insertion from the n-hexyl hydrido complex D and 35.4 kcal mol\u20131 (TS-F2F3), the magnitude of (TS-F2F3) allows us to discount the latter pathway. While (TS-D1D2) is competitive with that computed for (TS-GH), the barrier found for the subsequent necessary 1-hexene insertion is considerably lower than that associated with the Si\u2013H/Mg\u2013C metathesis reaction , suggesting that the latter step is rate determining and that the hydrosilylation process is, in any case, more likely to occur from F after complete alkylation of complex 4.The hydrosilylation of 1-hexene in the presence of PhSiH Fig. S37 and from Fig. S38. Althoug4) derivative reacts directly with terminal alkenes, the strained internal alkene, norbornene, and diphenylacetylene to provide the corresponding organomagnesium derivatives. Although the dinuclear structure of the magnesium hydride is retained during its initial reaction with 1-hexene, which occurs via a kinetic barrier comparable to that deduced for the analogous reaction of the hydridocalcium compound (3),via rate determining Si\u2013H/Mg\u2013C metathesis of the three-coordinate organomagnesium derivative.A dimeric \u03b2-diketiminato magnesium hydride (1) and compound 4 with styrene, however, hints that even more expansive substrate scope and catalytic activity may be achievable through the adoption of more sophisticated ligand design. Although not a central focus of our own research, we hope that our observations will prompt others toward a more wide-ranging and sustainable future.These observations reveal that hydridomagnesium compounds may display a much broader reactivity with alkenyl substrates than previously appreciated. The comparable reactivity of Parkin's terminal magnesium hydride (There are no conflicts of interest to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Owing to the increased proton affinity that results from additional negative charges, multiply-charged anions are shown as a route to preparing powerful \u2018superbases\u2019. ortho-diethynylbenzene dianion (ortho-DEB2\u2013) and present observations of this novel species undergoing gas-phase proton-abstraction reactions. Using a theoretical model based on Marcus\u2013Hush theory, we attribute the stability of ortho-DEB2\u2013 to the presence of a barrier that prevents spontaneous electron detachment. The proton affinity of 1843 kJ mol\u20131 calculated for this dianion superbase using high-level quantum chemistry calculations significantly exceeds that of the lithium monoxide anion, the most basic system previously prepared. The ortho-diethynylbenzene dianion is therefore the strongest base that has been experimentally observed to date.Owing to the increased proton affinity that results from additional negative charges, multiply-charged anions have been proposed as one route to prepare and access a range of new and powerful \u201csuperbases\u201d. Paradoxically, while the additional electrons in polyanions increase basicity they serve to diminish the electron binding energy and thus, it had been thought, hinder experimental synthesis. We report the synthesis and isolation of the The strongest base prepared to date is the lithium monoxide anion (LiO\u2013).\u20131, LiO\u2013 supplanted the methide anion (CH3\u2013) at the top of the basicity scale in 2008, exceeding the proton affinity of the carbanion by approximately 40 kJ mol\u20131.3O\u2013.\u2013 and CH3\u2013 necessarily satisfy two essential requirements: they are the conjugate bases of very weak gas-phase acids and their neutral radicals have low electron affinities (EAs). Multiply-charged anions can also fulfil these thermochemical requirements, as the gas-phase acidity of an anion is inherently low while the electron affinity of an anion can be low or even negative. Despite their potential instability, such dianion systems have been observed because of a repulsive Coulomb barrier (RCB) that arises from the interaction between the local bound-potential of the functional group carrying the charge and the repulsive Coulomb potential between like charges.meta-DEB2\u2013) was postulated to be a gas-phase superbase with a calculated PA of 1796.6 kJ mol\u20131, approximately 15 kJ mol\u20131 greater than that of the lithium monoxide anion.In the gas phase, the proton affinity of an anion is equivalent to the enthalpy of deprotonation \u0394acidH29 of the cmeta-DEB2\u2013 in the gas phase along with the isomeric 1,2- and 1,4-diethynylbenzene dianions . Observation of proton-transfer reactions between these dianions and a number of weak acids demonstrates their behaviour as gas-phase bases. The calculated proton affinity of each of the DEB2\u2013 isomers exceeds that of the lithium monoxide anion, with ortho-DEB2\u2013 representing the strongest gas-phase base synthesised to date.In this article, we outline the synthesis of ortho-DEB2\u2013 dianion at a mass-to-charge ratio (m/z) of 62 was performed using tandem mass spectrometry in a linear quadrupole and followed the process outlined in m/z 106), which was mass-selected and subjected to successive collisional activation steps to remove the carboxylate groups while retaining both charges. Such decarboxylation processes that are accompanied by retention of charge have previously been noted for several organolithium compounds.meta- and para-DEB2\u2013, using the appropriate isomeric diacid precursor. In addition to the DEB2\u2013 dianion (m/z 62) and its associated proton-transfer product (m/z 125) observed in 2 and loss of an electron from m/z 84 (m/z 124), accompanied by a small amount of C2 loss from this ion (m/z 100).Synthesis of the m/z 62 dianions is retained from their precursor diacids . This is strongly supported by the differences in product ions and product ion abundances observed in the mass spectra at each step of the gas-phase preparation is diagnostic of deuteron abstraction from the heavy water. Because the performance of the ion-trap mass spectrometer is diminished at very low m/z (i.e. m/z < 20), the intensity of the m/z 18 peak appears artificially reduced compared with the intensity of m/z 126 and consequently a robust comparison of the product ion abundances is not possible. The presence of the m/z 125 ion in all spectra is evidence of proton abstraction from unlabelled water and other background gases present in the instrument.Mass selection allowed isolation of the m/z 125 . This prortho- and meta-DEB2\u2013 and adiabatic electron affinities of the corresponding singly-charged radical anions . Using a relation derived from Marcus\u2013Hush theory, the RCB height can be estimated from the calculated AEA and VDE values according to eqn (1).18For ta-DEB2\u2013 , proton ra-DEB2\u2013 , a produG* as the energy barrier for electron detachment, the reorganisation energy \u03bb as the energy difference between the VDE and AEA, and \u0394G\u00b0 as the AEA, an estimate of the RCB height can be ascertained from the computed minimum energy structures of diethynylbenzene as both singly- and doubly-charged anions. The results, compiled in ortho- and para-DEB\u02d9\u2013, suggesting that only the meta-DEB2\u2013 dianion is thermodynamically stable with respect to electron detachment. For the three dianions, however, electron ejection is inhibited by RCBs of 11.1 (ortho), 52.7 (meta) and 1.9 (para) kJ mol\u20131. These barrier heights, calculated from eqn (1), are consistent with the analytical determination of barrier heights obtained using a rectilinear projection of the singly- and doubly-charged anion geometries . These results provide experimental evidence that the DEB2\u2013 isomers are capable of deprotonating benzene and thus have proton affinities in excess of PA[C6H5\u2013] = 1678.7 \u00b1 2.1 kJ mol\u20131.2O and C6H6, the reactivity observed for ortho-DEB2\u2013 far exceeds that of the other two isomers, reinforcing the heightened basicity of this species compared with meta- and para-DEB2\u2013, which are essentially the same at this level of ion signal. No proton-transfer reactions were observed between DEB2\u2013 isomers and either dihydrogen or methane despite favourable thermodynamics for these processes, which may be attributed to the presence of a substantial barrier for proton abstraction from these acids and benchmark calculations show good agreement in the case of strong gas-phase bases for which experimental PA data exist calculated at the same level of theory. Most significantly, ortho-DEB2\u2013 has a computed proton affinity of 1843.3 kJ mol\u20131, making it the strongest base synthesised to date by some 65 kJ mol\u20131.The G4(MP2)-6X method has been shown to have good performance for computing PAs shows that the proton affinity of acetylide anions can be related to the homolytic bond dissociation enthalpy (BDE) of the C\u2013H bond and the AEA of the corresponding radical by the ionisation energy of a hydrogen atom (IE[H]).21 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013(CH2)n\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC]2\u2013 (n = 1\u20134) scale\" fill=\"currentColor\" stroke=\"none\">C\u2013(CH2)n\u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC]\u02d9\u2013 radical anions decrease from +86.1 kJ mol\u20131 (n = 4) to +1.4 kJ mol\u20131 (n = 2) before returning large negative values when only a single methylene separates the two acetylide groups: \u201377.1 kJ mol\u20131 (n = 1). The decrease in AEA is accompanied by a concomitant increase in the proton affinity for the 2\u2013 dianion from 1775.4 (n = 4) through to 1888.1 kJ mol\u20131 (n = 1). While the proton affinity can be enhanced by bringing the like charges together, synthesis and isolation of a dianion superbase requires an RCB sufficient to prevent electron detachment. The simple formalism of eqn (1) predicts that when n = 1 the RCB is very low (4.2 kJ mol\u20131), suggesting that, like para-DEB2\u2013 to yield the doubly-decarboxylated dianion at m/z 62 along with the singly-charged CO2 loss ion m/z 124 and a proton-transfer product (m/z 125). This protocol was used for all three isomers. A minor product at m/z 100, most likely C2 loss from m/z 124, was observed for ortho-DEB2\u2013 only.The dianions were synthesised by electrospray ionisation of a methanolic solution of 3,3\u2032-(phenylene)dipropiolic acid, basified with aqueous ammonia to aid deprotonation. Mass spectra were acquired using a dual linear quadrupole ion-trap mass spectrometer . Precursor dianions at 2O and C6H6). The vapour pressure of the neutral reagent at room temperature was sufficient to seed the helium buffer gas and was delivered to the high-pressure cell of the dual ion trap through the unmodified buffer gas inlet and split flow in the mass spectrometer. Reactions with gaseous reagents (D2 and CD4) were performed using a pre-made mixture of the deuterated reagents in UHP helium and delivered into the ion trap through the ion trap buffer gas He inlet. The proportions of each gas mixture were 1.6% by volume in helium for D2 and 0.14% by volume in helium for CD4, yielding estimated number densities of 1.42 \u00d7 1012 molecules per cm3 and 1.24 \u00d7 1011 molecules per cm3, respectively, at the \u223c2.5 mTorr pressure within the ion trap.2O, D2 and CD4 was necessitated by the presence of adventitious protonation reagents (such as H2O and CH3OH) in the vacuum system.Ion\u2013molecule experiments were conducted by passing the ion-trap He buffer gas over a small amount of the neutral reagent for the fully-optimised structures, we used BMK/6-31+G harmonic vibrational frequencies and appropriate literature scale factors .ortho-, meta- and para-diethynylbenzene, we have examined the potential energy surfaces for the mono- and di-anionic species along the path that connects the geometries of the two ions. This is accomplished using structures obtained through a linear combination of the optimised structures for the mono- and di-anions (see \u20131. Cartesian coordinates for all structures calculated are provided in the ESI as Table S4.Standard ions see . ImproveSupplementary informationClick here for additional data file."}
+{"text": "A comprehensive experimental and quantum chemical study of the open-shell mixed valent disilicon hydride Si2(H)(Idipp)2 CH]2) is reported. II PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi0(Idipp)][B(ArF)4] (1H[B(ArF)4], Idipp = C[NCH]2, ArF = C6H3-3,5-(CF3)2) reveal a reversible one-electron reduction at a low redox potential (E1/2 = \u20132.15 V vs. Fc+/Fc). Chemical reduction of 1H[B(ArF)4] with KC8 affords selectively the green, room-temperature stable mixed-valent disilicon hydride Si2(H)(Idipp)2 (1H), in which the highly reactive Si2H molecule is trapped between two N-heterocyclic carbenes (NHCs). The molecular and electronic structure of 1H was investigated by a combination of experimental and theoretical methods and reveals the presence of a \u03c0-type radical featuring a terminal bonded H atom at a flattened trigonal pyramidal coordinated Si center, that is connected via a Si\u2013Si bond to a bent two-coordinated Si center carrying a lone pair of electrons. The unpaired electron occupies the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital leading to a formal Si\u2013Si bond order of 1.5. Extensive delocalization of the spin density occurs via conjugation with the coplanar arranged NHC rings with the higher spin density lying on the site of the two-coordinated silicon atom.Cyclic voltammetric studies of the hydridodisilicon borate [(Idipp)(H)Si Quantum chemical studies revealed the same sequence of frontier orbitals in +1H and its isolobal phosphorus counterpart +, according to which the HOMO\u20131 corresponds to the lone-pair orbital at the two-coordinated E atom , the HOMO is the E PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE \u03c0-bonding orbital and the LUMO is the E PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE \u03c0* orbital.+1H might be also reversibly reducible as the phosphanylphosphenium cation + .1H[B(ArF)4] in fluorobenzene at room temperature revealed a reversible one-electron reduction at a rather low half-wave potential (E1/2) of \u20131.63 V as well as an irreversible oxidation at +0.67 V versus the [Fe(\u03b75-C5Me5)2]+1/0 reference electrode scale\" fill=\"currentColor\" stroke=\"none\">Si0(Idipp)][B(ArF)4] (1Me[B(ArF)4])E1/2 = \u20131.85 V) than 1H[B(ArF)4]. Notably, reduction of +1H and +1Me occurs at much lower potentials than that of the cation + (E1/2 = \u20130.48 V).9The hydridodisilicon salt [(Idipp)(H)Silectrode and ESI\u20201H[B(ArF)4]. Indeed, vacuum transfer of THF to a 1\u2009:\u20091 stoichiometric mixture of 1H[B(ArF)4] and KC8 at \u2013196 \u00b0C followed by warming to \u201340 \u00b0C resulted in a distinct color change of the dark red solution of 1H[B(ArF)4] to give an intensely dark green solution, which after work-up and crystallization from n-hexane at \u201360 \u00b0C afforded Si2(H)(Idipp)2 (1H) as a dark green, almost black crystalline solid in 55% yield and 1 (5%).The CV results prompted us to attempt a chemical one-electron reduction of 5% yield (see ESI5% yield . Compoun1H [E1/2 in C6H5F = \u20132.15 V vs. [Fe(\u03b75-C5H5)2]+1/0 (Fc+/Fc)]E1/2 in THF = \u20132.30 V vs. Fc+/Fc)5-C5Me5)2] (E1/2 in MeCN = \u20131.91 V vs. Fc+/Fc),1H is a very strong one-electron reducing agent. Consequently, the radical 1H is selectively oxidized back to 1H[B(ArF)4] upon treatment with one equivalent of [Fe(\u03b75-C5Me5)2][B(ArF)4] in THF-d8 . The UV-Vis-NIR spectrum was also analyzed by time-dependent density functional theory (TdDFT) calculations against the absolute temperature (T) showed a linear correlation from which the effective magnetic moment \u03bceff was calculated after linear regression and found to be 1.68 \u03bcB (\u03bceff = 1.73 \u03bcB).Magnetic susceptibility measurements of solid 1.68 \u03bcB . This va1H was determined by single crystal X-ray crystallography. The radical features a crystallographically imposed inversion symmetry (space group: P21/c) in marked contrast to the C1-symmetric structure of +1H in 1H[B(ArF)4].R2 values. 1H features as 1H[B(ArF)4] and 1 a trans-bent planar CNHC\u2013Si\u2013Si\u2013CNHC core (1H (2.281(3) \u00c5) is considerably longer than that in 1H[B(ArF)4] (2.1873(8) \u00c5)1 (2.229(1) \u00c5) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi double bond (2.20 \u00c5)e.g. 2.352 \u00c5 in \u03b1-Si).NHC bonds in 1H (1.873(4) \u00c5) are shorter than the Si\u2013CNHC bonds of the dicoordinated Si atoms in 1H[B(ArF)4] (1.940(2) \u00c5)1 (1.927(1) \u00c5)1H[B(ArF)4] (1.882(2) \u00c5).+1H results also in a distinct change of the conformation of the NHC substituents. Thus, both N-heterocyclic rings in 1H are arranged coplanar with the trans-bent CNHC\u2013Si\u2013Si\u2013CNHC core as evidenced by the dihedral angle \u03c6NHC of 3.3(2)\u00b0 (+1H one of the two N-heterocyclic rings (bonded to the two-coordinated Si atom) adopts an almost orthogonal orientation (vide infra). Thus, reduction of +1H leads to a population of the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital with one electron, reducing thereby the formal Si\u2013Si bond order from 2 in +1H to 1.5 in 1H as nicely reflected in the computed Si\u2013Si Wiberg bond indexes of +1H = 1.70; WBI(Si\u2013Si) of 1H = 1.17) scale\" fill=\"currentColor\" stroke=\"none\">Si \u03c0* orbital with \u03c0*(CN2) orbitals of the NHC substituents in the SOMO of 1H (NHC bonds and the concomitant elongation of the CNHC\u2013NNHC bonds of 1Hversus+1H (The molecular structure of NHC core . However 3.3(2)\u00b0 , whereasentation . All theMO of 1H , providiersus1H+ .1H displayed a \u03bd(Si\u2013H) absorption band at 2089 cm\u20131, which is characteristic for stretching vibrations of terminal Si\u2013H bonds band of Si2H is predicted at significantly lower wavenumbers (1592 cm\u20131 (2A1 state); 1491 cm\u20131 (2B1 state)),\u03bd(Si\u2013H\u2013Si) absorption bands of H-bridged silylium ions are shifted to much lower wavenumbers compared with the \u03bd(Si\u2013H) bands of the corresponding silanes (ca. 2150 cm\u20131).\u03bd(Si\u2013H) absorption band of 1H appears in-between that of 1H[B(ArF)4] containing a trigonal planar coordinated Si atom (\u03bd(Si\u2013H) = 2142 cm\u20131),ii)-hydride (IMe4)SiH(SitBu3) containing a strongly pyramidal bonded Si atom (IMe4 = C[N(Me)CMe]2: \u03bd(Si\u2013H) in KBr = 1984 cm\u20131).\u03bd(Si\u2013H) frequency decreases with increasing pyramidalization of the Si atom, which according to the quantum chemical calculations can be traced back to the decreasing s-character of the Si hybrid orbital in the Si\u2013H bond com1H was provided by continuous wave (cw) EPR spectroscopy at X-band frequencies. Spectra with a nicely resolved hyperfine coupling pattern could be obtained from samples of 1H in n-hexane solution at 336 K nucleus, two different 29Si (I = 1/2) and two pairs of two magnetically equivalent 14N (I = 1) nuclei, respectively hyperfine coupling constants (1.725 and 0.431 mT) were found, indicating an asymmetric spin density distribution over the Si atoms. Both values are smaller than those of other Si-based \u03c0 type radicals, such as the disilene radical cation [Si2(SitBu2Me)4]+ (2.30 mT)2R4]\u2013 1[B(ArF)4] (5.99 mT),vide infra). The two a(14N) hfcc's (0.246 and 0.100 mT) suggest a fast rotation of the magnetically different NHC substituents about the Si\u2013CNHC bonds on the EPR timescale occurring even at low temperature , whereas two almost degenerate minimum structures were obtained at the B97-D3/II level of theory contain a trigonal-pyramidal coordinated Si1 atom with a sum of angles of 335.51\u00b0 (B3LYP/I) and 342.58\u00b0 (B97-D3/II), respectively. Remarkably, the calculated structure of the diphosphanyl radical P2(Me)Mes*2, which is isolobal to 1H, displays a trigonal pyramidal geometry at the three-coordinated P atom (sum of angles: 337.5\u00b0),calc1H. In comparison, the second minimum structure obtained at the B97-D3/II level of theory is only 5.5 kJ mol\u20131 higher in energy than calc1H and contains the Si1 atom in a trigonal planar environment (sum of angles: 359.61\u00b0). A comparison of the structural parameters of calc1H and calc1H\u2032 with those obtained by single crystal X-ray diffraction reveals a good agreement of the calculated Si\u2013Si, Si\u2013CNHC and CNHC\u2013NNHC bond lengths of both minimum structures . All caldentical . These sructures . While tcalc1H at the B3LYP/I level of theory and of calc1H and calc1H\u2032 at the B97-D3/II level of theory are almost identical scale\" fill=\"currentColor\" stroke=\"none\">Si \u03c0* orbital, confirming that reduction of +1H leads to a population of the empty Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital of +1H with one electron scale\" fill=\"currentColor\" stroke=\"none\">Si \u03c0 and the n(Si) lone pair orbital, respectively.The calculated quasi-restricted orbitals (QROs) of dentical . The SOMcalc1H revealed that the overall wave function is described by a major ground state configuration of [2-1-0] of the DOMO, SOMO and LUMO with 96% contribution, suggesting that static correlation can be neglected in the electronic description of 1H /def2-TZVP calculationsH see ESI.calc1H and calc1H\u2032 at the B97-D3/II level of theory are depicted in calc1H, 29% in calc1H\u2032), whereas the spin density at the Si1 atom is quite small , which is in full agreement with the observation of one large and one small a(29Si) hfcc in the experimental EPR spectrum of 1H (vide supra) and Si2-bonded NHC substituents, which explains the EPR-spectroscopic detection of two a(14N) hfcc's. The calculated giso values of calc1H (2.00483) and calc1H\u2032 (2.00454) agree well with the experimentally obtained giso value (2.00562).The calculated spin densities of 1H was provided by a natural bond orbital (NBO) analysis at the B3LYP/I level of theory scale\" fill=\"currentColor\" stroke=\"none\">Si \u03c0 bond with an occupancy of 1.95 and 0.82 electrons, respectively, which indicates indirectly a population of the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital with one electron leading thereby to a decrease of the formal Si\u2013Si bond order from 2 in +1H to 1.5 in 1H (vide supra). The Si2 atom in calc1H bears a lone pair of high s-character (72%) as similarly found for +calc1H (75%). Remarkably, both Si\u2013CNHC bonds in calc1H are composed of one doubly occupied Si\u2013CNHC \u03c3 NBO and one singly occupied Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCNHC \u03c0 NBO, of which the latter is absent in +calc1H. These additional Si\u2013CNHC \u03c0 contributions rationalize the shortening and strengthening of the Si\u2013CNHC bonds in 1H, which is also reflected in the higher Si\u2013CNHC WBI indexes (1H: WBI(Si\u2013CNHC) = 1.01 and 0.95; +1H: WBI(Si\u2013CNHC) = 0.86 and 0.74).Further insight into the electronic structure of calc1H and +calc1H at the B3LYP/I level of theory reveal that the positive partial charges at the Si atoms of +calc1H (q(Si1) = 0.27e, q(Si2) = 0.21e) are decreased by the reduction (1H: q(Si1) = 0.14e, q(Si2) = 0.03e) = 0.36e, q(NHC2) = 0.30e; 1H: q(NHC1) = 0.05e, q(NHC2) = \u20130.04e), whereas the hydridic character of the Si1-bonded H atom is retained = \u20130.14e; 1H: q(H) = \u20130.18e).Comparative analyses of the charge by natural population analyses (NPA) of 3.2H (1H) can be considered as a major advance in low-valent silicon hydride chemistry, given the intermediacy of Si2H in the chemical vapor deposition of amorphous hydrogenated silicon that is widely used in solar cell and thin film transistors technology. Whereas Si2H features a C2v-symmetric H-bridged ground state structure and is a \u03c3-type radical with a symmetric distribution of the spin density over the two silicon atoms, its NHC-trapped counterpart Si2(H)(Idipp)2 (1H) features a terminal Si\u2013H bond and is a \u03c0-type radical, in which the unpaired electron occupies the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital (SOMO), leading to a formal Si\u2013Si bond order of 1.5. Significant delocalization of the spin density into the NHC substituents occurs via \u03c0-conjugation of the Si PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSi \u03c0* orbital with the \u03c0* orbitals of the coplanar arranged N-heterocyclic rings leading to a stabilization of the radical, in which the spin density is higher at the two-coordinated Si site. The mixed valent disilicon hydride 1H can be alternatively regarded as a H atom trapped in the closed shell compound Si2(Idipp)2. Implications of this view in hydrogen atom transfer chemistryThe isolation and full characterization of NHC-trapped SiSupplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "A reverse polarity photocatalysed Povarov reaction of imines and electron deficient alkenes is described. via a putative nucleophilic \u03b1-amino radical, generated by a proton coupled electron transfer process, addition to a range of conjugated electron deficient alkene substrates affords substituted tetrahydroquinoline products in high yields and with typically good to excellent diastereoselectivity in favor of the trans diastereoisomer. Sub-stoichiometric quantities of Hantzsch ester were found to be key to initiate the overall redox-neutral, free radical cyclization cascade. This new reaction complements existing two electron Lewis acid mediated variants and expands the capabilities of imine umpolung chemistry to synthetically relevant cyclisation methodology.A visible light mediated iridium photocatalysed reverse polarity Povarov reaction of aryl imines and electron deficient alkenes is described. Operating Photoredox catalysis, through its ability to generate reactive radical intermediates under mild yet highly tunable reaction conditions and experimental set-ups,7via the SET reduction of imine derivatives.15Photocatalytic approaches to the synthesis and functionalisation of amines and their derivatives \u2013 with direct impact on medicinal chemistry programmesin situ generated \u03b1-amino radicals from imines. Such a reversal of the natural imine polarity via the PCET manifold establishes a new umpolung approach for the synthesis of \u03b1-functionalised amines for the generation of \u03b1-heteroatom radicals,d amines , and creN,N-dimethylaniline and maleimide derivatives provided some precedent for the cyclisation pathway , phenyl vinyl sulfone as the Michael acceptor, (Ir[dF(CF3)ppy]2(dtbbpy))PF6 as photocatalyst and the commercial Hantzsch ester as a stoichiometric reductant, in DMSO, under blue LED light irradiation. Pleasingly, good reactivity was identified early and importantly cyclised product 3a \u2013 a reverse polarity Povarov productHE1. This was largely due to suppression of over-reduction and aza-pinacol side products (entry 2) and the use of substituted Hantzsch esters further suppressed their formation.Preliminary studies were carried out using fluorine tagged aldimine (3b\u2013d). Good reaction efficiency and excellent diastereoselectivity towards the trans diastereoisomeric product was noted in all cases.cis-configured stereoisomeric products often predominate.3e\u2013g, 3j\u2013n) whereas electron poor aromatics led to longer reaction times (3h) and even complete nullification of reactivity (3i). 3-Fluoro and 2-fluoro-substituted aldimines were tolerated in this chemistry however longer reaction times were required and yields diminished with proximity to the imine C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond (3p\u2013r). A substituted pyridyl substrate was also shown to be effective in the reaction mixture leading to an excellent yield of product (3s).With optimal conditions established, we looked to probe the scope of the photocatalytic reverse polarity Povarov reaction . Initial3t) even after prolonged reaction times. 4-Chlorophenyl vinyl sulfone was found to be an excellent electrophile (3ab). Similarly, maleimide and N-phenylmaleimide electrophiles were shown to be excellent coupling partners in the new cyclisation methodology, however diastereoselectivity was respectively reduced or absent in the reaction products (3ac\u2013ae). The chemistry was extendable to a three component one-pot process was resubmitted to the reaction conditions. Pleasingly an increase to 18\u2009:\u20091 was observed and mass balance was maintained ,4a, via initial reduction of the imine. This reinforces the proposal of PCET construction of the key \u03b1-amino radical.Recent investigations have shown that imines was replaced with 3a ppy]2(dtbbpy)PF6 (E01/2 = \u20131.37 V vs. SCE in CH3CN)A. As this methodology only requires sub-stoichiometric quantities of the substituted Hantzsch ester (HE4), we suggest this Povarov radical intermediate A can lose a proton to form radical anion intermediate B, in a base assisted homolytic aromatic substitution-type mechanism.1a and 2a, to be 18.3a) and regenerating the key \u03b1-amino radical.From these insights, we propose that PCET would enable Ir[dF(CFvia the PCET of imine derivatives. 10 mol% of a Hantzsch ester was found to be optimal as a reductive initiator, a feature which has not previously been disclosed in photoredox catalysis. Further investigations are ongoing to establish further coupling partners and scaffolds for this reverse polarity platform for the synthesis of \u03b1-functionalised amines.In conclusion we have developed a new photocatalytic reverse polarity Povarov reaction to construct decorated tetrahydroquinolines in high yield and diastereoselectivity. This polarity reversal was postulated to stem from an \u03b1-amino radical formed There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The deselenization of selenocysteine selectively removes the selenol group to give alanine under anaerobic conditions or serine under aerobic conditions (oxygen saturation). The development of native chemical ligation coupled with desulfurization has allowed ligation at several new ligation junctions. However, desulfurization also converts all cysteine residues in the protein sequence into alanine. Deselenization of selenocysteine, in contrast, selectively removes the selenol group to give alanine in the presence of unprotected cysteines. In this study we shed more light onto the deselenization mechanism of selenocysteine to alanine and provide optimized conditions for the reaction. The deselenization can be accomplished in one minute under anaerobic conditions to give alanine. Under aerobic conditions (oxygen saturation), selenocysteine is converted into serine. First, TCEP reduces selenocystine into selenocysteine, followed by deselenization with \u223c90% conversion after 24 hours. The slow rate of the reaction can be attributed to the acidic conditions (pH\u223c1). The observed 1H-NMR shift confirms both the conversion of selenocysteine to mono-deuterated Ala scale\" fill=\"currentColor\" stroke=\"none\">Se and TCEP PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO scale\" fill=\"currentColor\" stroke=\"none\">Se, and TCEP PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO , featuring a single Sec residue, was chosen as our control. Our starting conditions were phosphate buffer at room temperature, as previously reported.Following our initial investigation, we synthesized a series of peptides 1\u20138, and test1 led to a faster reaction where with 200 equiv. TCEP we observed complete deselenization within 1 min over peptide in 1 min and S13\u2020tBuSH) but was not completely eliminated. We therefore omitted any thiol additives from the following experiments.Under these ambient aerobic conditions, the Ser product was observed in significant amounts (20%) .33,51 Ine.g. temperature) play a more significant role in enhancing this reaction.Irradiation could in principle enhance the deselenization reaction by enhancing selenenyl radical formation, as suggested earlier for desulfurization reactions.1 increased significantly in the presence of the radical initiator VA-044, even when using a lower concentration of TCEP, and was completed within 1 min was almost completely halted even after 12 h scale\" fill=\"currentColor\" stroke=\"none\">Se (a product of the deselenization reaction) completely inhibits the deselenization reaction. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe the reaction proceeded smoothly, and the deselenized Ala product formed within 30 min was slowed due to the low redox potential of the diselenide bond in the UXXU motif.7, the Cys analog of 3, required 200 equiv. TCEP and 10 equiv. VA-044 at 37 \u00b0C to give the doubly desulfurized product after 8 h in which Cys5 is substituted with Sec (BPTI(1\u201358)(C5U), peptide 1 was treated with TCEP at 0 \u00b0C in oxygen-saturated buffer, the Ser product was observed as the major product within 5 min was prepared together with the two possible products containing l-Ser 8a and d-Ser 8b leads to the formation of an alkyl radical on the \u03b2-carbon III, which abstracts a hydrogen to form the Ala product.The proposed radical deselenization mechanism is shown in II) becomes more favored. On the other hand, decreasing the temperature could slow the C\u2013Se bond cleavage and allow other reactions, such as the attack of the diradical oxygen molecule (if present), to take precedence. The inability of peptide 5 to form the Ser product, even under oxygen-saturated conditions, is consistent with our proposed mechanism, in which molecular oxygen is converted to a radical species via direct contact with the seleno-phoshoranyl radical II. This radical intermediate gives the peroxy-radical IV, which is reduced by TCEP to give Ser. In contrast, the alkyl radical on the \u03b2-carbon III (a common species in desulfurization and deselenization reactions) has little or no effect on molecular oxygen, thus no Cys to Ser conversion is observed with peptide 5. The driving force of the deselenization reactions is the formation of a strong P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe bond in TCEP PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSe.The formation of the Ser product is interesting, as this product can be completely eliminated under anaerobic conditions or selectively formed under oxygen-saturated conditions. As we noted initially, the deselenization rate of Sec to Ala increases with increasing the temperature of the reaction, suggesting that the homolytic C\u2013Se bond cleavage in the seleno-phosphoranyl radical (In this work, we have optimized both the selective deselenization reaction and provided considerable experimental evidence to support the previously suggested radical mechanism.We envision that selenocysteine modification reactions such as the deselenization reactions presented in this study will find future utility in chemical protein synthesis. This will enable the use of native cysteines for some ligation sites and selenocysteines at sites in which a non-chalcogen containing amino acid is desired.Supplementary informationClick here for additional data file."}
+{"text": "We report the straight forward synthesis of a series of arene-borazine hybrids (BN-PAHs) called borazatruxenes; the DFT, solid state and solution characterisation are reported along with the separation and chiroptical studies of four optical isomers. We report the synthesis and characterization of a series of arene-borazine hybrids called borazatruxenes. These molecules are BN-isosteres of truxene whereby the central benzene core has been replaced by a borazine ring. The straightforward three step synthesis, stability and their chiroptical and electronic properties recommend them as new scaffolds for BN\u2013carbon hybrid materials. Computational studies at DFT level, closely matching the experimental data, provided insights in the electronic structure of these molecules. The interest in polycyclic aromatic hydrocarbons (PAHs) has grown over the past decade due to their stability, tuneable properties and versatility.3-symmetric PAH that has been intensively studied for the past 15\u201320 years.Truxene is a C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC with a B\u2013N in a PAH will lead to quasi-identical geometries but drastically different electronic structures.The B\u2013N bond is quasi-isosteric and isoelectronic with the C2 in close capped vials; they are stable in solution for at least two weeks with minimal decomposition.\u00a7The borazatruxenes are stable in solid state for at least one year if kept under N and easy to synthesise. Borazatruxenes are truxene analogues in which the central benzene core has been replaced by borazine. The B atom is directly linked to the phenylene rings which are connected via a methylene bridge to the N atom of the borazine core. This particular arrangement is responsible for the borazatruxenes' hydrolytic stability. Borazatruxenes 1\u20133 were synthesised according to the synthetic pathway illustrated in Herein we introduce a new class of borazine-PAHs that are moisture stablemeta- and para- substituted 2-formylbenzeneboronic acids were reacted with methoxyamine hydrochloride under refluxing conditions for 15 minutes in water (pH 7) to produce compounds 8\u201310 in high yields (70\u201390%). LiAlH4 in THF was added dropwise to a solution of phenylboronic acid derivatives 8\u201310 in THF at \u201378 \u00b0C, the mixture was allowed to warm to room temperature followed by heating to reflux for 3 hours. In all cases, the amine-borane11\u201313, a BN analogue of indane, was isolated in excellent yields (85\u201390%). Trimerisation11\u201313 under microwave-assisted conditions afforded the desired borazatruxenes 1\u20133 in 56\u201365% yields as white solids after a simple filtration/washing protocol.Commercially available 14\u201317 were synthesised from meta- and para- substituted benzonitriles. The benzonitriles were reacted with lithium tetramethylpiperidine (LTMP) and B(OiPr)3 at \u201378 \u00b0C, followed by slow warming to room temperature (20 \u00b0C) overnight to afford the respective ortho- substituted 2-cyanophenylboronic acid. The reaction was quenched using AcOH (2.2 equiv.) followed by an in situ protection of the boronic acid with 1,3-propanediol. The use of a protecting group is key for isolation of 14\u201317, and the choice of 1,3-propanediol allows the reduction to the corresponding amine-borane products 18\u201321 in very good yields (65\u201395%), without requiring a further deprotection step , respectively.Due to the limited number of commercially available 2-formylphenylboronic acids and their relatively lengthy syntheses, a second pathway was devised in order to obtain functionalised borazatruxenes . 2-Cyanoion step and ESI\u2020 8 and 9 , have be1 is soluble in organic solvents of medium polarity. This is in stark contrast to the parent truxene, which has very poor solubility in most common solvents.1, which is likely due to their increased molecular weight. The 1H-NMR of 1 indicates that the aromatic protons closest to the borazine rings are most deshielded (8.03\u20138.05 ppm) while the external ones experience a lower influence of the BN anisotropy with chemical shifts in the range of 7.42\u20137.59 ppm. The 11B NMR spectrum displays a peak resonating at 37.2 ppm which is in good agreement with a typical 11B chemical shift of a substituted borazine. The UV-vis spectrum of 1 shows a very intense and broad absorbance centered at 250 nm followed by three distinct peaks of lower intensity at 279.5, 272.0 and 265.0 nm. These peaks are blue shifted compared to corresponding truxene ones, thus highlighting that introducing BN bonds into the all-carbon system increases the HOMO\u2013LUMO gap isomer identical with the and isomers. Therefore, the only possible isomers are the enantiomeric pairs syn: and with all three methyl groups located on the same side of the borazatruxenes plane, and anti: and , where one methyl is on the opposite side of the plane with respect to the other two while the anti enantiomers are separated with a selectivity factor of 1.17 . The Circular Dichroism (CD) spectra of the two enantiomeric pairs syn and anti of chiral derivative 9 display strong Cotton effects on both the arene and borazine absorbance. The identification of all four isomers was possible by comparing the experimental (vide infra) CD spectra.There are four possible optical isomers of borazatruxene ther two . The synrimental with the11 (P2n1/ with four molecule units per unit cell packed in staggered array motif.The molecular structure of BN-indane 11 was obtaThe distance between boron and nitrogen atom is 1.637 \u00c5 consistent with an N \u2192 B Lewis-type interaction. There are two weak NH\u00b7\u00b7\u00b7\u03c0 intermolecular interactions between the amine group with the aromatic rings of two neighbouring molecules: N\u00b7\u00b7\u00b7Ph(C2\u2013C7) distance of 3.239 \u00c5 and N\u00b7\u00b7\u00b7Ph distance of 3.339 \u00c5.1 came from an X-ray diffraction analysis of single crystals grown by slow evaporation from a CH2Cl2 solution. 1, which crystallises in a P21/c space group. This compound forms a staggered L-shaped configuration in the unit cell -9 and -9 co-crystallised in the R3[combining macron] space group. In this structure the two enantiomers adopt a 60\u00b0 rotated face-on stacked arrangement with an intermolecular B\u2013N distance of 3.749 \u00c5 and the Me groups pointing outwards overlay of the experimentally determined (X-ray diffraction) co-ordinates and the computed ones. Geometry optimisations were performed using M06-2X,Gaussian 16 software. Also, TD-DFTversus the agreement to experimental X-ray data (Table S10, Fig. S20The X-ray determined structure of In summary, we have developed the synthesis of a new class of BN-PAHs that incorporate a borazine unit in place of the central benzene core of a truxene. These derivatives have higher solubilities than the parent all-carbon derivatives and can be synthesised in three steps from commercially available starting materials. These derivatives are air and moisture stable which is in contrast to the majority of non-sterically hindered borazines. We have synthesised and separated the first chiral derivatives of these molecules which also represents a premiere in the larger truxene family. The borazatruxenes molecules are likely to become important materials in molecular electronic devices due to their unique structure which combines areas of electron-conductance with electron-insulating domains. Further investigations into the synthesis of new borazatruxenes analogues are currently in progress in our group.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Against expectations the covalency in a cerium(iv)\u2013carbon multiple bond interaction is essentially as covalent as the uranium(iv) analogue. TMS)(ODipp)2] whereas for M = Th the M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond interaction is much more ionic. On the basis of single crystal X-ray diffraction, NMR, IR, EPR, and XANES spectroscopies, and SQUID magnetometry complexes 1\u20133 are confirmed formally as bona fide metal(iv) complexes. In order to avoid the deficiencies of orbital-based theoretical analysis approaches we probed the bonding of 1\u20133via analysis of RASSCF- and CASSCF-derived densities that explicitly treats the orbital energy near-degeneracy and overlap contributions to covalency. For these complexes similar levels of covalency are found for cerium(iv) and uranium(iv), whereas thorium(iv) is found to be more ionic, and this trend is independently found in all computational methods employed. The computationally determined trends in covalency of these systems of Ce \u223c U > Th are also reproduced in experimental exchange reactions of 1\u20133 with MCl4 salts where 1 and 2 do not exchange with ThCl4, but 3 does exchange with MCl4 and 1 and 2 react with UCl4 and CeCl4, respectively, to establish equilibria. This study therefore provides complementary theoretical and experimental evidence that contrasts to the accepted description that generally lanthanide\u2013ligand bonding in non-zero oxidation state complexes is overwhelmingly ionic but that of uranium is more covalent.We report comparable levels of covalency in cerium\u2013 and uranium\u2013carbon multiple bonds in the iso-structural carbene complexes [M(BIPM Nature of the Chemical Bond over 75 years ago, chemists have vigorously debated the nature of chemical bonding.4Ever since the publication of vs. 0.89 \u00c5 and 1.01 vs. 1.03 \u00c5 for the +IV and +III oxidation states, respectively);iii) complexes is generally described as being independent of the ligand environment and \u2018free-ion-like\u2019.iii) the [Xe]4f1 \u2192 [Xe]4f05d1 transition is found to depend strongly on the ligand field, varying from 49\u2009737 cm\u20131 for gaseous Ce3+, to 22\u2009000 cm\u20131 for Ce3+ doped into Y3Al5O12, to 17\u2009650 cm\u20131 for [Ce{\u03b75-C5H3(SiMe3)2}3].vs. 5f elements. Overall, for an isostructural pair of tetravalent uranium and cerium complexes, the order of covalency involving those metal centres would normally be expected to be uranium significantly greater than cerium. This is important to understand, from a fundamental perspective, but there are also practical implications; these three elements can be found in the presence of one another in spent nuclear fuel and future strategies to separate them might depend on exploiting differences in their covalent chemical bonding.A comparison of chemical bonding that is often made is between 4f cerium and 5f uranium, since according to Shannon their ionic radii are very similar carbene diaryloxide complex [Ce(BIPMTMS)(ODipp)2] .1 is notable for being a cerium(iv) organometallic and containing a Ce PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC multiple bonding interaction. Whilst dominated by electrostatics, this bond exhibits covalency according to NBO analysis of DFT-derived densities. There is reason to have confidence in such analysis as SAOP/ZORA/TZP TD-DFT calculations at the same level of theory reproduce very well the experimentally observed UV/Vis/NIR spectrum. NBO analysis identifies \u223c13% cerium character in each of two Ce\u2013C bonding interactions (\u03c3 + \u03c0). Non-aqueous cerium(iv)th ionisation energy of cerium is greater than the sum of the first three;1 in-hand, we surmised that as uranium(iv) and thorium(iv) are robust oxidation states, the synthesis of 1 presents an opportunity to directly compare the nature of the chemical bonding of cerium, uranium, and thorium. Here, we report the synthesis and characterisation of [M(BIPMTMS)(ODipp)2] ; the synthesis of 2 and 3 are straightforward, but importantly permit a comparison of the bonding of three isostructural complexes. Surprisingly, both DFT and CASSCF/RASSCF methods suggest that the covalency and f-orbital interactions for the cerium and uranium complexes are essentially the same, in contrast to the thorium complex that is essentially ionic. The emergence of these results is in contrast to almost all other examples of comparative studies of 4f and 5f covalency,iv) and uranium(iv) hexachloride dianion salts, where on the basis of orbital energy near-degeneracy similar levels of covalency between cerium(iv) and uranium(iv) have been proposed.1\u20133 are also consistent with experimental exchange reactions with metal tetrahalide salts of cerium, uranium, and thorium, further supporting our findings.Recently, as part of a wider effort to prepare lanthanide\u2013carbon multiple bonds,1, which required a multi-step preparation,2 and 3 was straightforwardly accomplished by installation of the BIPMTMS carbene then the two aryloxides onto uranium or thorium by sequential salt elimination reactions, 2 and 3 were isolated as brown and colourless crystals in 56 and 61% yield, respectively. The 1H NMR spectrum of 2 spans the range \u201319 to +17 ppm and the 31P NMR spectrum exhibits a broad resonance at \u2013293 ppm, consistent with the uranium(iv) formulation that is supported by a solution magnetic moment of 2.75 \u03bcB at 298 K. In contrast, the 1H NMR spectrum of 3 spans the range 0 to +8 ppm and the 31P NMR resonance appears at +4.7 ppm. The electronic absorption spectrum of 2 (see ESI\u03b5 < 80 M\u20131 cm\u20131) absorptions over the range 500\u20131900 nm that are characteristic of Laporte forbidden f\u2013f transitions for the 3H4 electronic manifold of the 5f2 uranium ion3 the spectrum is featureless over 400\u20132000 nm as expected for its colourless 6d05f0 nature. As reported previously, the electronic absorption spectrum of 1 exhibits two broad absorptions in the visible region , the broadness and resulting purple colour of which is a defining feature of many cerium(iv) complexes.23In contrast to 2 see ESI is chara2 and 3 were determined by single crystal X-ray crystallography, 1\u20133 is a monomeric formulation with terminal M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. The remaining coordination sphere of each metal is completed by two BIPMTMS imino chelate arms and the two aryloxide oxygen centres which enforce a pseudo square-based pyramidal geometry. We found a Ce PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC distance of 2.441(5) \u00c5 in 1; PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds reported in the theoretical models of CeCH2+ and Cp2CeCH2 complexes,2+ and Cp2CeCH2 are experimentally unknown, sterically unimpeded and, in the case of the former, benefit from the reduced electronic repulsion associated with a net positive charge. For experimentally realised compounds, the Ce PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC distance of 1 is amongst the shortest ever reported, except for the special case of fullerene encapsulated Ce2. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and Th PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC distances in 2 and 3 were determined to be 2.414(3) and 2.508(5) \u00c5, respectively; on the basis of Shannon's ionic radii PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and Th PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds in BIPMTMS complexes.26The molecular structures of 1\u20133 are also consistent with solid state magnetic measurements, 2 has a room temperature \u03c7T of 0.93 cm3 K mol\u20131 and decreases rapidly on cooling tending to zero, which is typical for 5f2 uranium(iv) that is a magnetic singlet at low temperature.3 is diamagnetic, consistent with closed-shell thorium(iv). Studies of 1 give a very small magnetic moment (0.02\u20130.1 cm3 K mol\u20131 depending on temperature and diamagnetic corrections) that varies from batch to batch nor the difference between the 4f (Ce) and 5f (Th) ion diamagnetism. Because measured samples of 1 have a very weak paramagnetism, the precise nature of the \u03c7T(T) plot or other diamagnetic configurations (admixtures of cerium(iv) with singlet cerium(iii) + radical ligand configurations have been proposed for cerocene).ca. 5\u201315% of values expected for f1 cerium(iii) .1 decomposes to give cerium(iii) \u2013 we note the related complex [Ce(BIPMTMS)(ODipp)(THF)]geff,\u2225 = 3.7 and geff,\u22a5 = 0.85 , and therefore that comparisons to 2 and 3 are valid, we recorded the XANES spectrum of 1.The weak paramagnetic response from samples of 5 see ESI. That thIII-edge spectrum of 0.01 M Ce(NO3)3 in water, the cerium(iii) precursor to 1 [Ce(BIPMTMS)(ODipp)2K(THF)], CeO2, and 1 are illustrated in iii) complexes, the LIII-edge spectra of aqueous Ce(NO3)3 and [Ce(BIPMTMS)(ODipp)2K(THF)] both consist of a single peak, just above the absorption threshold, at \u223c5725.7 eV that is characteristic of cerium(iii).III-edge spectra of CeO2 and 1 both exhibit the characteristic double absorption features of cerium(iv) at \u223c5727.2 and \u223c5736.7 eV, that are similar to those of CeF4, Ce(SO4)2\u00b74H2O, and CeCl62\u2013.III-edge E1 absorption for 1 is \u223c1.5 eV higher in energy than the corresponding [Ce(BIPMTMS)(ODipp)2K(THF)] LIII-edge absorption, as found generally for cerium(iv) complexes.2 and 1 are both essentially 1\u2009:\u20091, as has been found for CeCl62\u2013 and CeF4,1 L\u20131 contribution to a multiconfigurational ground state,i.e. a multiconfigurational excited state.iv) complexes with oxide and halide ligands is due to final state effects,1 is certainly much more like that of CeO2, CeF4, Ce(SO4)2\u00b74H2O, and CeCl62\u2013 than cerocene; this observation is consistent with the premise that an open-shell singlet or triplet formulation of 1 should be regarded as less likely than a closed-shell singlet and so we conclude that the presence of cerium(iii) character in 1 can be excluded.The cerium L1 possesses formal cerium(iv) character, it can legitimately be compared to 2 and 3. We previously reported Natural Bond Orbital (NBO) data for 1 which returned \u03c3- and \u03c0-bonds composed of \u223c13% Ce and \u223c87% C character.2 by NBO, a similar breakdown is returned. Specifically, the \u03c3-bond is composed of 16% U and 84% C and the \u03c0-bond is made up of 14% U and 86% C character. The U contributions to the \u03c3- and \u03c0-bonds are 5f (87%) and 6d (12%), and 5f (77%) and 6d (22%), respectively. In contrast, the NBO data for 3 return ionic interactions with localised carbene lone pairs with no Th character as the contribution of the latter falls below the default cut-off of 5% in the NBO code. These calculations suggest that, whilst the bonding between cerium\u2013, uranium\u2013, and thorium\u2013carbon centres in 1\u20133 are dominated by ionic interactions, a modest and surprisingly comparable covalent contribution to the bonding is evident in 1 and 2 despite the commonly held view that lanthanide\u2013ligand chemical bonding is purely ionic.Since the XANES data suggest that PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC units in 1\u20133. These calculations employed the restricted-active-space self-consistent field (RASSCF) theory,via a configuration interaction approach. Whilst RASSCF is a powerful technique for elucidating the nature of metal\u2013ligand interactions in complexes such as those considered here, it is limited in the size of systems to which it can be applied. For this reason, complexes 1\u20133 were truncated in order to render RASSCF calculations computationally tractable by replacing P-phenyls with H, silyl-methyls with H, and the bulky Dipp groups by Me. This truncation retains the coordination environment of all atoms directly bonded to the metal: where hydrogen termination was employed, only the positions of the terminating hydrogens were optimised.Although the NBO calculations are internally consistent and well suited to describing covalency in molecules,iv) complexes have shown density-based analysis methods provide unambiguous electronic structure interpretations.\u03b4), a quantitative measure of the degree of electron sharing between two atomic centres, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond critical point (\u03c1), an accepted measure of covalency. These two measures, while complementary, are not equivalent: \u03c1 provides a quantitative measure of charge accumulation in the bonding region, which is related to spatial overlap, whereas the delocalisation index, \u03b4, between two bonded atoms is maximised when electrons are shared equally which, in a monodeterminantal framework, is a manifestation of orbital degeneracy. This analysis therefore allows us to determine the variation in both of these phenomena when the metal centre is varied and has previously been reported in several studies of cerium and uranium complexes.\u03c1 and <3% in \u03b4 are observed when comparing full and truncated complexes, demonstrating that the quantitative bonding characteristics of the full complexes 1\u20133 is retained.In order to assess any truncation effects on the electronic structures, ground state electron densities were calculated at the PBE/TZVP level of theory. These densities were probed with the quantum theory of atoms in molecules (QTAIM) approachTMS favour f- over d-orbital participation in the bonding of this ligand to f-elements generally, but further studies will be required to confirm this. This definition of the active subspaces resulted in RASSCF calculations. The number of explicitly correlated electrons, n, was 22 for complexes 1 and 3 and 24 for complex 2. In all cases, calculations were performed in Cs symmetry.The electronic structures of the truncated complexes were then evaluated using the RASSCF methodology. These calculations employed three active spaces: RAS1, containing only occupied orbitals from the monodeterminantal reference wavefunction, RAS2, containing both occupied and virtual orbitals, and RAS3, containing only virtual orbitals. Full configuration interaction (CI) was performed in RAS2, while truncated CI, considering only singly and doubly excited configurations, was performed between the RAS1, RAS2 and RAS3 subspaces. All active space orbitals were optimised. Due to the large computational costs of such calculations, the RAS1, RAS2 and RAS3 subspaces were restricted to 11, 7 and 11 orbitals, respectively: the 7 RAS2 orbitals incorporated the 4f/5f manifold, whereas the RAS1 and RAS3 subspaces included all orbitals with significant carbon and nitrogen 2s and 2p character. The oxygen 2s and 2p orbitals could not be included in the active subspaces, since attempts resulted in the intrusion of phosphorus-based orbitals. It was observed, however, that oxygen 2s and 2p orbitals that were successfully stabilised in the active subspaces exhibited occupation numbers extremely close to integer values. Similarly, occupation numbers of formally unoccupied d-orbitals was effectively 0, indicating that the inclusion of these orbitals in the active subspaces is not required. It may be that the geometric constraints of BIPMiv) centres, in agreement with our experimental measurements, and these configurations contribute 89.0, 89.5 and 89.3% to the ground state RASSCF wavefunctions of 1\u20133 , respectively. Maximum deviations from integer values in natural orbital occupations were 0.032, 0.033, and 0.025, respectively, indicating rather weak multi-configurational character.2 configuration of the uranium compound) should be sufficient to accurately describe the M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonding interaction. Subsequent analysis of CASSCF-derived densities revealed them to be extremely similar to their RASSCF counterparts N-heterocyclic carbene complex [Ce(L){N(SiMe3)2}2F] [L = OCMe2CH2(CNCH2CH2N-Dipp)] a \u03c1 of 0.045 a.u. is found,\u03c1 was found to be 84.9% of the \u03c1 value. Similarly, calculations on cerocene\u03c1 to be 0.0395, which is 83.0% of the analogous value calculated for uranocene.\u03c1 for 1 to be 91.3% of the corresponding U value in 2. Comparison of \u03b4 can also be made with that in cerocene, where it was found to be 83.2% of the \u03b4 value in uranocene; here, we calculate \u03b4 for 1 to be 99.1% of the corresponding \u03b4 value in 2.The RASSCF-calculated wavefunctions were used to obtain explicitly correlated electron densities for subsequent QTAIM analysis. Metal charges are all significantly higher than those found using DFT, increasing by 0.68, 0.59 and 0.49 to give absolute values of +2.84, +2.89 and +3.02 a.u. for 1\u20133 and calibrate the above calculations, we investigated the exchange reaction chemistry of 1\u20133 since it is well known that covalency can drive exchange reactions. For example, rare earth tris-cyclopentadienyl complexes readily react with iron halides to afford ferrocene and rare earth halides and this reactivity, whilst undoubtedly reflecting the favourable formation of lanthanide\u2013halide bonds, is driven by the formation of highly covalent iron\u2013cyclopentadienyl bonding.43In order to experimentally probe the relative levels of covalency in 1, which is known to be unstable in solution, no reaction between 1 and [ThCl4(THF)3.5] is observed in benzene after a 24 hour stir (eqn (1)). After a 5 day stir 1 is completely decomposed to yield a species that exhibits a resonance at \u201334 ppm in the 31P NMR spectrum. Although we have not been able to isolate and identify this species its 31P NMR chemical shift is in the region where related cerium(iii) BIPMTMS complexes exhibit 31P NMR resonances.1 does not react with thorium tetrachloride and instead decomposes before any reactivity can occur. In the reverse scenario, eqn (2), treatment of 3 with [CeCl4(HMPA)] [HMPA = OP(NMe2)3] results in the loss of 1H NMR resonances attributable to 3 and evolution of the characteristic purple colour of 1 in the first 15 minutes. After 15 minutes the purple colour fades and an intractable mixture of products is formed. Given that the preparation of 1 is not straightforward it is not surprising that if formed under these less than optimal conditions it would decompose given its instability in solution, but the purple colour is certainly consistent with the exchange of BIPMTMS from thorium(iv) to cerium(iv) and in-line with the proposed differences in covalency.Apart from the onset of decomposition of 1 and [ThCl4(THF)3.5], eqn (1), we find that there is also no reaction of 2 with [ThCl4(THF)3.5], eqn (3). In the reverse situation, eqn (4), 3 does react with [UCl4(THF)3]. Unfortunately, an intractable product mixture is obtained, likely due to ligand scrambling under conditions that are by definition less controlled than the usual route to prepare 2. However, it is clear that 1H NMR resonances attributable to 3 are lost so the implication is that the BIPMTMS ligand is transferred to uranium. Irrespective of the precise outcomes, these reactions are consistent with uranium being more covalent than thorium.As with the absence of reaction between 1 is treated with [UCl4(THF)3], eqn (5), the intense purple colour of 1 fades within 30 minutes and is replaced by a green colour which is then replaced by a brown colour consistent with the formation of 2. In the reverse situation, eqn (6), 1H NMR resonances attributable to 2 are lost; no purple colour was observed, but it is clear that ligand exchange has occurred, and we note that after a 5 day stir the mixture exhibits a 31P NMR resonance at \u201334 ppm, which is indicative of a cerium(iii) BIPMTMS derivative.2 with neat HMPA in a control experiment and found that no reaction occurs. The uranium\u2013cerium exchange reactions are not clean, but it is evident that ligand exchange occurs to some extent. Although equilibria are to some extent established, 1 is not stable in solution for extended periods and the evidence suggests that eventually the cerium decomposes to the trivalent state, which then degrades the equilibria.When Hrxn) for the full, balanced versions of eqn (1)\u2013(6), eqn (7)\u2013(12), by calculating the gas phase geometry optimised structures of all the constituent components. A solvent continuum was not applied since the solvent for eqn (1)\u2013(6) was benzene, which could reasonably be expected to have systematically minimal interactions with the electropositive species in solution. Experimentally, [ThCl4(THF)3.5] is most likely a separated ion pair formula like related lanthanide triiodides,4(THF)3]. The calculations most likely carry absolute errors of 5\u201310 kcal mol\u20131, but, assuming that this is to some extent systematic, the relative errors will reduce to \u223c2\u20135 kcal mol\u20131. The calculations are thus clear-cut as they independently and correctly reproduce the experimental outcome in every case.To further support the above findings, we determined the theoretical bond enthalpy changes (\u0394iv) does not displace BIPMTMS from cerium(iv) or uranium(iv) whereas the latter pair do displace BIPMTMS from the former. When cerium(iv) or uranium(iv) derivatives are mixed it is evident that equilibria are established, but the reactions are not clean and the equilibria are disrupted due to the instability of 1. Although some of the products of these reactions are not known, the key point is whether a reaction occurs at all or not. The fact that distinct colour changes are observed, or not, suggests that the carbenes are, or not, transferred since it is the M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds that contribute to absorptions in the visible part of the optical spectra for 1 and 2 and the M\u2013ODipp linkages absorb well into the UV-region. Therefore, the conclusion is that thorium(iv) is the most ionic in this context, whereas cerium(iv) and uranium(iv) do exhibit comparable covalency and these observations experimentally support the same theoretical proposition.Overall, these exchange reactions demonstrate that thorium scale\" fill=\"currentColor\" stroke=\"none\">C units in these complexes is predominantly ionic, we note a significant covalent contribution to these linkages for cerium and uranium. Significantly, the levels of covalency and f-orbital participation in the M PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds are remarkably similar for cerium and uranium, but different from thorium which is ionic. Importantly, the similar levels of covalency in the cerium(iv)\u2013 and uranium(iv)\u2013carbon multiple bonds in 1 and 2 manifests in more than one type of theoretical treatment , and most compellingly is supported by experimental exchange reactions that proceed as predicted from the above covalency arguments. It may be that the similar levels of covalency of cerium(iv) and uranium(iv) is a more general effect than currently recognised, but one that is relatively small and so has eluded detection in systems that exhibit minimal covalency. Since the synthesis of cerium(iv) complexes that go beyond simple salts is still in its infancy, and is experimentally challenging, it may be that more examples of cerium(iv) and uranium(iv) complexes containing similar levels of covalency await discovery. At the very least the results presented here provide a basis to question the established exclusive ionic bonding textbook description of the lanthanides in non-zero oxidation states, especially with reference to certain 5f metals.In summary, we have reported the synthesis of TMS)(ODipp)2] (1),3(BIPMTMS)Li(THF)2], and [Th(Cl)2(BIPMTMS)] were prepared by published methods.1H, 13C, 29Si, and 31P NMR spectra were recorded on a Bruker 400 spectrometer operating at 400.2, 100.6, 79.5, and 162.0 MHz respectively; chemical shifts are quoted in ppm and are relative to TMS and 85% H3PO4 (31P). FTIR spectra were recorded on a Bruker Tensor 27 spectrometer. UV/Vis/NIR spectra were recorded on a Perkin Elmer Lambda 750 spectrometer. Data were collected in 1 mm path length cuvettes loaded in an MBraun UniLab glovebox and were run versus the appropriate reference solvent. Solution magnetic moments were recorded at room temperature using the Evans method. Static variable-temperature magnetic moment data were recorded in an applied dc field of 0.1 T on a Quantum Design MPMS XL7 superconducting quantum interference device (SQUID) magnetometer using doubly recrystallised powdered samples. Care was taken to ensure complete thermalisation of the sample before each data point was measured and samples were immobilised in an eicosane matrix to prevent sample reorientation during measurements. Diamagnetic corrections were applied for using tabulated Pascal constants and measurements were corrected for the effect of the blank sample holders and eicosane matrix. Variable temperature (300\u20135 K) EPR spectra were measured at X-band on a Bruker Elexsys E580 spectrometer. Polycrystalline samples were sealed under vacuum in 1 mm i.d. silica tubing, and double-contained for EPR by insertion into an X-band silica tube or PTFE sleeve. CHN microanalyses were carried out by Tong Liu at the University of Nottingham. Cerium LIII-edge XANES measurements were performed using a Si(111) double-crystal monochromator on the Rossendorf Beamline at the European Synchrotron Radiation Facility . Higher harmonics were rejected by two Si coated mirrors. The spectra were collected using ionisation chambers filled with nitrogen and a 13-element Ge fluorescence detector. The samples were measured at 15 K in a closed-cycle He cryostat. The reference samples spectra of 0.01 M Ce(iii) nitrate in H2O and solid CeO2 were measured at room temperature in transmission mode.All manipulations were carried out using Schlenk techniques, or an MBraun UniLab glovebox, under an atmosphere of dry nitrogen. Solvents were dried by passage through activated alumina towers and degassed before use or were distilled from calcium hydride. All solvents were stored over potassium mirrors, except for ethers that were stored over activated 4 \u00c5 sieves. Deuterated solvent was distilled from potassium, degassed by three freeze\u2013pump\u2013thaw cycles and stored under nitrogen. [Ce(BIPMTMS)(Cl)3(Li)(THF)2] and [K(ODipp)] . The resulting brown suspension was allowed to warm to room temperature with stirring over 16 h to afford a brown solution. Volatiles were removed in vacuo and the resulting solid was extracted into toluene. Volatiles were removed in vacuo to afford a brown solid which upon recrystallisation from Et2O (2 ml) at \u201330 \u00b0C afforded 2\u00b7Et2O as brown crystals. Yield: 0.69 g, 56%. Anal. calcd for C59H82N2O3P2Si2U: C, 57.91; H, 6.76; N, 2.29%. Found: C, 57.76; H, 6.66; N, 2.33%. 1H NMR (C6D6): \u03b4 \u201318.94 3), \u20133.43 2), \u20133.25 2), 1.23 , 3.34 , 6.70 , 8.17 , 13.40 , 16.07 , 16.48 (Ar-H). 31P{1H} NMR (C6D6): \u03b4 \u2013293.42 (UCP2). FTIR \u03bd/cm\u20131 (Nujol): 1590 (w), 1539 (w), 1403 (w), 1330 (w), 1200 (s), 918 (w), 887 (w), 857 (s), 838 (s), 748 (w), 694 (w), 661 (w). Magnetic moment : \u03bceff = 2.75 \u03bcB.THF (15 ml) was added to a precooled (\u201378 \u00b0C) mixture of [U(BIPM2(BIPMTMS)] in THF (5 ml) was added to a solution of [ThCl4(THF)3.5] in THF (5 ml) at \u201378 \u00b0C. The pale yellow mixture was stirred at \u201378 \u00b0C for 30 minutes, then was allowed to warm to room temperature with stirring for 2 h. Volatiles were removed in vacuo and DippOK was added. Toluene (10 ml) was added slowly to the cold (\u201330 \u00b0C) stirring mixture, the resultant mixture was allowed to warm to room temperature with stirring for 1 h. After this time the mixture was filtered, and all volatiles were removed in vacuo. The product was recrystallised from a toluene/hexane mixture to yield 3\u00b70.5(toluene) as colourless crystals. Yield: 0.69 g, 61%. Anal. calcd for C62H80N2O2P2Si2Th: C, 60.27; H, 6.53; N, 2.27%. Found: C, 59.96; H, 6.64; N, 2.45%. 1H NMR (C6D6): \u03b4 0.14 3), 1.35 2), 3.74 2), 6.97\u20137.04 , 7.21 , 7.55\u20137.61 . 13C{1H} NMR (C6D6): \u03b4 3.18 3), 24.45 2), 28.14 , 67.04 scale\" fill=\"currentColor\" stroke=\"none\">CP2), 120.15, 123.26, 125.66, 128.53, 129.29, 130.11 (ArC), 131.36 , 131.43 , 136.94 , 139.01 , 139.49 , 161.26 . 31P{1H} NMR (C6D6) \u03b4 4.65 (s). 29Si{1H} NMR (C6D6) \u03b4 \u20137.20 , \u20137.24 . FTIR \u03bd/cm\u20131 (Nujol): 1589 (w), 1325 (w), 1260 (s), 1197 (m), 1100 , 1095 , 1042 (m), 1023 (m), 887 (w), 856 (m), 800 (m), 726 (m), 609 (m).A solution of [Li1, 2, and 3 and the components of the exchange reactions using coordinates derived from their X-ray crystal structures. No constraints were imposed on the structures during the geometry optimisations. The calculations were performed using the Amsterdam Density Functional (ADF) suite version 2010.01.et al.via single point energy (SPE) calculations, replacing the basis sets of the metal ions with the segmented all-electron relativistically contracted (SARC) basis sets,via the 2nd order Douglas\u2013Kroll\u2013Hess Hamiltonian.via the 2nd order Douglas\u2013Kroll\u2013Hess Hamiltonian. Topological and integrated atomic properties, obtained using the quantum theory of atoms in molecules (QTAIM), were performed using version 13.11.04 of the AIMAll software package.65Unrestricted and restricted geometry optimisations were performed as appropriate for full models of Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Computations on the heavier group 14 dimetallenes [E{CH(SiMe3)2}2]2 and [E{N(SiMe3)2}2]2 and their respective monomers indicated that empirically observed dimerization is principally driven by attractive dispersion forces. 3)2}2]2 and [E{N(SiMe3)2}2]2 and their dissociation into :E{CH(SiMe3)2}2 and :E{N(SiMe3)2}2 monomers were studied computationally using hybrid density functional theory (DFT) at the B3PW91 with basis set superposition error and zero point energy corrections. The structures were reoptimized with the dispersion-corrected B3PW91-D3 method to yield dispersion force effects. The calculations generally reproduced the experimental structural data for the tetraalkyls with a few angular exceptions. For the alkyls, without the dispersion corrections, dissociation energies of \u20132.3 (Ge), +2.1 (Sn), and \u20130.6 (Pb) kcal mol\u20131 were calculated, indicating that the dimeric E\u2013E bonded structure is favored only for tin. However, when dispersion force effects are included, much higher dissociation energies of 28.7 (Ge), 26.3 (Sn), and 15.2 (Pb) kcal mol\u20131 were calculated, indicating that all three E\u2013E bonded dimers are favored. Calculated thermodynamic data at 25 \u00b0C and 1 atm for the dissociation of the alkyls yield \u0394G values of 9.4 (Ge), 7.1 (Sn), and \u20131.7 (Pb) kcal mol\u20131, indicating that the dimers of Ge and Sn, but not Pb, are favored. These results are in harmony with experimental data. The dissociation energies for the putative isoelectronic tetraamido-substituted dimers [E{N(SiMe3)2}2]2 without dispersion correction are \u20137.0 (Ge), \u20137.4 (Sn), and \u20134.8 (Pb) kcal mol\u20131, showing that the monomers are favored in all cases. Inclusion of the dispersion correction yields the values 3.6 (Ge), 11.7 (Sn), and 11.8 (Pb) kcal mol\u20131, showing that dimerization is favored but less strongly so than in the alkyls. The calculated thermodynamic data for the amido germanium, tin, and lead dissociation yield \u0394G values of \u201312.2, \u20133.7, and \u20133.6 kcal mol\u20131 at 25 \u00b0C and 1 atm, consistent with the observation of monomeric structures. Overall, these data indicate that, in these sterically-encumbered molecules, dispersion force attraction between the ligands is of greater importance than group 14 element\u2013element bonding, and is mainly responsible for the dimerization of the metallanediyls species to give the dimetallenes. In addition, calculations on the non-dissociating distannene [Sn{SiMetBu2}2]2 show that the attractive dispersion forces are key to its stability.The structures and bonding in the heavier group 14 element olefin analogues [E{CH(SiMe The mixing of a bonding and antibonding orbital generates a molecular orbital with lone-pair character, and hence a pyramidalized coordination for E. This interaction takes place more readily in the heavier main group element derivatives because the bonds become increasingly long (weaker) as a result of larger Pauli repulsions between core electrons as the group is descended. Consequently, the energy difference between the \u03c3* and \u03c0 orbitals also decreases, and hence the extent of their interaction increases. The trans-folding, which weakens the E\u2013E bond, is often sufficient to cause dissociation of the double bond of the heaviest tin and lead species to two monomeric metallanediyls. However, dissociation is less common in their germanium analogues and for the iconic disilenes, first reported in 1981,19The synthesis of the lower valent group 14 element dialkyls :E{CHSiMe2}2 3}2, which has a long central single C\u2013C bond of 1.67 \u00c5 and is stabilized via dispersion force interactions between the But groups, whereas the corresponding C\u2013C bonded, less hindered, unsubstituted species (CPh3)2 is unknown.26The investigation and rationalization of bonding in these and related multiple-bonded compounds has been a topic of broad interest3)2}2 and E{N(SiMe3)2}2 as well as the corresponding E\u2013E bonded dimers. The calculations without the inclusion of dispersion force effects revealed that the E\u2013E bonding energies are low for the tetraalkyls, and insufficient to stabilize their dimeric structures under ambient conditions. In contrast, the inclusion of dispersion force resulted in large increases in the binding energies. Application of the same protocols to the amido compounds also afforded lower binding energies that are insufficient to sustain the dimeric structures under ambient conditions.Despite these developments, the realization of importance of the dispersion interactions between the C\u2013H moieties of substituent ligands to the stability of inorganic and organometallic compounds is not widespread. However, several reports have shown that such forces are very important for the bonding and structure of a variety of species.H), entropy (S), and free energies (G) as well as zero point energies (ZPE) were estimated using calculated harmonic vibrational frequencies and BSSE corrected energies.All calculations were carried out using the Gaussian 09 program.3)2}2 (E = Ge or Sn) monomers have the syn, syn orientation of the \u2013CH(SiMe3)2 alkyl groups in the gas phase, as shown in 3)2}2 monomer. However, in 3)2}2, derived from a syn, syn Pb{CH(SiMe3)2}2 unit within the [Pb{CH(SiMe3)2}2]2 (3)2}2 (E = Ge or Sn)syn, anti conformation, as shown in 3)2}2 units within the lead \u2018dimer\u2019 have the aforementioned syn, syn configuration, as shown in i.e. the same configuration as those experimentally observed for the germanium and tin dialkyl monomers in the gas phase.9; Sn\u2013Sn = 2.768(1) \u00c510) are reproduced with good accuracy. Exceptions to this generalization involve the calculated torsion angles between the methane C\u2013H bonds and the central EC2 (E = Ge or Sn) plane in the germanium and tin monomers, and the C\u2013Ge\u2013C angle in the germanium monomer, which is somewhat high. For the torsion angle in the germanium and tin monomers, the discrepancy is almost 20\u00b0 in the germanium and 6\u20138\u00b0 in the tin monomer. Unfortunately, in the monomeric structures which are measured from GED (gas electron diffraction) data, no standard deviations were given. However, standard deviations of 2\u00b0 were listed for the EC2 angle, and it is reasonable to suppose the standard deviation for the torsion angle for the methane C\u2013H bonds would be larger than this value. We replicated the optimization with the HCECH torsion angles fixed at the experimental values of 2\u00b0 (E = Ge) and 15\u00b0 (E = Sn). As shown in Table S1,\u20131 for Ge, but only 2.5 kcal mol\u20131 for tin. Thus, the HCECH torsion angle has significantly larger effect in the germanium dimer, consistent with its more sterically-congested structure. It is worthwhile to recall that the calculations on the dimers are for the molecules in isolation (i.e. in the gas phase), and take no account of the effects of neighboring molecules (i.e. packing forces), which can also be expected to exert some effect on their structure.The calculated structural parameters at various levels of optimization for the alkyl-substituted germanium, tin, and lead monomers and dimers are presented in e3)2}2]2 \u2018dimer\u2019.3)2}2 dimer3)2}2 units in the crystal structure. Nevertheless, long interactions of this type between the heavier main group elements can be significant.3)2}2 units within the lead dimer are syn, syn monomers, that is to say the long Pb\u2013Pb interaction is ignored, the structural parameters given for Pb{CH(SiMe3)2}2 in 3)2}2 monomer (cf. C\u2013Sn\u2013C = 97(2)\u00b0 by GED). In effect, the data suggest that the Pb{CH(SiMe3)2}2 units within the lead dimer are behaving essentially as weakly interacting plumbylene monomers, rather than as a Pb\u2013Pb multiple bonded diplumbene.The calculated Pb\u2013Pb separation and C\u2013Pb\u2013C angle in the dimeric lead structure differ considerably from the experimentally measured values. The experimental Pb\u2013Pb distance of 4.129(1) \u00c5 in the crystal structure of the 2 \u2192 2P{CH(SiMe3)2}2 process upon relaxation of the configurations from syn, anti to syn, syn.3)2}2 unit steric crowding because of the larger sizes of germanium and tin in comparison to that of phosphorus.It was noted above that the experimentally-determined orientation of the \u2013CHSiMe2 groups 3)2 groups of the [Pb{CH(SiMe3)2}]2 dimer to the syn, anti orientation observed for the lighter congeners; the data in Table S4syn, syn orientation; the dispersion corrected distance of 2.956 \u00c5 (B3PW91-D3) approaches the sum of the covalent radii indicating a significant degree of Pb\u2013Pb bonding. Also noteworthy is the effect upon the C\u2013Pb\u2013C angle which is calculated to widen significantly (91.3 versus 106.6\u00b0 at the B3PW91-D3 level); likely a consequence of steric clash between the SiMe3 groups of the ligand. Such an angle, however, would also optimize Pb\u2013Pb bonding by increasing the p-character of the Pb lone pair. That the Pb{CH(SiMe3)2} dimer does not adopt such a conformation must suggest the nature of the Pb{CH(SiMe3)2}2 dimer is that of two weakly interacting plumbylene monomers wherein significant s-character of the lone pair enforced by the narrow C\u2013Pb\u2013C angles (93.4(2)\u00b0) lead to \u201cclosed-shell\u201d interactions between the Pb atoms.It is also informative to consider the effect of altering the orientation of the CH(SiMe3)2}2]2 to two E{CH(SiMe3)2}2 monomers are summarized in \u20131 for the germanium, tin, and lead dimers with BSSE and ZPE corrections. The low values result from steric repulsion between the \u2013CH(SiMe3)2 groups. However, inclusion of dispersion effects using the B3PW91-D3 approach dramatically increases the binding energies to 28.7, 26.3, and 15.2 kcal mol\u20131, respectively. With the B97-D3 method, the calculated energies are 33.9, 33.3, and 20.2 kcal mol\u20131. Single-point MP2-based calculations afford energies of 41.2, 41.5, and 10.3 kcal mol\u20131. Taken together, the calculated energies strongly suggest that the major portion of the binding energy for the germanium, tin, and lead dimetallenes are a result of attractive dispersion forces between the \u2013CH(SiMe3)2 ligands. Calculation of the free energy changes (\u0394G) at 25 \u00b0C and 1 atm for the dissociation of the dimers, without dispersion force correction, affords values of \u201317.8, \u201314.8, and \u20139.9 kcal mol\u20131 for the germanium, tin, and lead derivatives respectively. In other words, dissociation is favored in all cases. Application of the dispersion-corrected B3PW91-D3 method changes these \u0394G values to +9.4, +7.1, and \u20131.7 kcal mol\u20131. Thus, the dimeric structures become favored for the germanium and tin species, but remains slightly disfavored for lead. These findings are in accord with the relatively long element\u2013element distances experimentally observed for the germanium and tin dimers, and the very weak interaction in the case of the lead species. The \u0394G energies calculated for the dissociation of germanium and tin alkyls at the temperatures and pressures at which the GED data sets were collected, i.e. 428 K and 0.1 Torr for the germanium dialkyl and 393 K and 0.1 Torr for the tin dialkyl, were \u20137.2 and \u20136.1 kcal mol\u20131. These negative values are consistent with the monomeric structures observed in the vapor phase.The data for the dissociation of the dimeric [E{CH2) series.3)2}2]2 and the behavior of the 13C shifts for the methine carbons in the monomers and dimers. This allowed calculation of \u0394H = 12.8 kcal mol\u20131 and \u0394S = 33 cal K\u20131 mol\u20131 for the dissociation. These experimental values differ considerably from those calculated . At present, the reason for the discrepancy between the experimental and calculated values is unclear, and more data will be required to establish the expected values for similarly-substituted monomer\u2013dimer equilibria. For example, significantly higher \u0394S values of 75 and 66 cal mol\u20131 K\u20131 have been determined for the dissociation of the [M{N(SiMe3)2}2]2 (M = Fe or Co), which carry \u2013N(SiMe3)2 substituents that are isoelectronic to CH(SiMe3)2.6H2-2,4,6-Me3){C6H2-2,4,6-(CH(SiMe3)2)3}]2 was studied by electronic spectroscopy which revealed a \u0394H value of 14.7(2) kcal mol\u20131 and a \u0394S value of 42.4 cal mol\u20131 K\u20131.49There has been only one report of an experimental determination of energies associated with the monomer\u2013dimer equilibrium of the E3)2}2]2 dimers. The syn, anti conformation adopted by germanium and tin yields an increased interligand steric congestion,syn, syn orientation and consequent attenuation of metal\u2013metal bonding. This conclusion is supported by the fact that the seven-membered ring dialkyl lead(ii) species PBM data was replaced with SVG by xgml2pxml: 1111111111111111111111111111111111 1111111111111111111111111111111111 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tPbC(SiMe3)2SiMe2CH2CH2SiMe2C PBM data was replaced with SVG by xgml2pxml: 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t(SiMe3)2,3)2}2]2 and a C\u2013Pb\u2013C angle of 117.1(2)\u00b0, has no Pb\u2013Pb contact shorter than 8.911 \u00c5. Furthermore, the Sn(ii) dialkyl PBM data was replaced with SVG by xgml2pxml: 1111111111111111111111111111111111 1111111111111111111111111111111111 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 1100000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tSnC(SiMe3)2(CH2)2C PBM data was replaced with SVG by xgml2pxml: 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000011 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t(SiMe3)2,3)2 moieties have a syn, syn-like conformation analogous to the vapor phase structure of Sn{CH(SiMe3)2}2 and the lead congener in all cases. These data suggest that a syn, syn orientation precludes strong M\u2013M contact and thus any dimerisation must emerge principally from dispersion interactions.A rationalization for the observed congeneric variation can thus be constructed wherein the interplay between the effects of dispersion interactions, steric congestion and metal\u2013metal bond strength define the observed structures of the 2 dimers at various levels of optimization are given in 3)2}2 units within the dimers are close to those calculated for the monomeric structures which match those experimentally determined by X-ray crystallography. The E\u2013E distances undergo large contractions when dispersion force corrections are included. However, the shortest distances calculated for the germanium and tin amido dimers, even with the inclusion of such forces at the B3PW91-D3 level, are significantly longer (by ca. 1.4 and 0.7 \u00c5) than the measured values and the values calculated at the same level for the alkyl dimers. The metal\u2013metal distance calculated for the amide-ligated lead dimer (3.714 \u00c5) by the B3PW91-D3 method is ca. 0.5 \u00c5 longer than the corresponding calculated distance (3.241 \u00c5) in the dialkyl lead dimer. These distances indicate considerably weaker interactions between the group 14 elements for the amido derivatives. Thermodynamic data 2 ligands. Further calculations on the thermodynamics of dissociation show that the \u0394G energies for the process are \u201316.4, \u201318.0, and \u201310.8 kcal mol\u20131 at 25 \u00b0C and 1 atm, so that dissociation and monomeric structures are favored under these conditions. These findings are, of course, consistent with the structural and physical data. The much weaker E\u2013E interactions in the amides in comparison with the alkyls is probably a result of electronic and steric factors. The more electronegative \u2013N(SiMe3)2 ligand causes a larger HOMO\u2013LUMO separation on the E atom, which would lower the extent of orbital interaction between the monomers. Also, the configurational differences between the \u2013CH(SiMe3)2 and \u2013N(SiMe3)2 may lead to greater steric hindrance, and hinder the association of the two monomeric fragments in the case of the amido ligand.The calculated structural parameters and dissociation energies of the putative [E{N4. While no full molecule calculations have been reported for [Sn{SiMetBu2}2]2 to investigate dispersion force contributions, a qualitative assessment can be made. One notable feature of dispersion force interactions is their dependence on length-scale and they are thought to be highly attenuated beyond the sum of the van der Waals radii of the interacting atoms.With these analyses in hand, it is informative to consider other stannylenes in the literature. Whilst a plethora of such species have been reported, the vast majority are monomeric in solution, and many with extremely sterically demanding ligands remain monomeric in the solid state.3)2}2]2 and [Sn{SiMetBu2}2]2 is informative 2}2 unit indicating that such a sterically unfavourable conformation is partly stabilised by dispersion interactions.As shown, analysis of the crystallographically defined structures of [Sn{CH2}2]2 species. Whilst the reporttBu3}2]2 provides an extensive electronic rationale for Sn\u2013Sn interactions being responsible for its observed dimeric structure and short Sn\u2013Sn distance, it is likely that dispersion forces are also of importance in stabilising the persistent dimeric nature of this compound.In the case of [Sn{SiMetBu2}2]2 confirm the presence of a shorter tin\u2013tin bond (2.647 \u00c5) than that in [Sn{CH(SiMe3)2}2]2. However, the calculations show that the binding energy increases from 25.8 to 46.8 kcal mol\u20131 with inclusion of dispersion effects, and that the \u0394G of dissociation at 25 \u00b0C and 1 atm is increased from 8.3 to a value of 26.5 kcal mol\u20131 upon inclusion of the dispersion correction, indicating that the dispersion force attraction is of key importance in maintaining the dimeric structure.To check this hypothesis, our initial full molecule calculations which are notable particularly for the \u2013CH(SiMe3)2 ligand. A similar analysis for the non-dissociating distannene [Sn{SiMetBu2}2]2 shows that in this molecule also, the dispersion forces are of key importance in its stabilization. These studies provide an initial framework for the analysis of metal\u2013metal bonding which takes into account these more subtle effects. Although much effort has been expended in development of bonding models for the multiple bonds between heavier main group elements, it seems both probable and ironic that the dispersion force attraction forces exceed those of the multiple bonds in many instances and that a variety of more subtle interactions including packing effects are of key importance for the understanding of their bonding.The calculations have shown that the interplay between dispersion force attraction, steric repulsion and element\u2013element bonding stabilize the dimeric structures. Although the E\u2013E distances indicate E\u2013E bonding is present in the germanium and tin dimers, and possibly the lead dimer, the bonding is weak, and represents a relatively small fraction of the binding energy. The results emphasize the importance of including attractive dispersion force interactions in consideration of multiple bonded heavier main group element species where sterically encumbering ligands are employed in their stabilization.Supplementary informationClick here for additional data file."}
+{"text": "A new, highly active Ir catalyst for dehydrogenative borylation of terminal alkynes (DHBTA) has been identified. via the changes in the substitution at phosphorus led to the discovery of a catalyst whose activity, longevity, and scope far exceeded that of the original SiNN archetype. Several Ir complexes were prepared in a model PNP system and evaluated as potential intermediates in the catalytic cycle. Among them, the (PNP)Ir diboryl complex and the borylvinylidene complex were shown to be less competent in catalysis and thus likely not part of the catalytic cycle.Following the report on the successful use of SiNN pincer complexes of iridium as catalysts for dehydrogenative borylation of terminal alkynes (DHBTA) to alkynylboronates, this work examined a wide variety of related pincer ligands in the supporting role in DHBTA. The ligand selection included both new and previously reported ligands and was developed to explore systematic changes to the SiNN framework (the 8-(2-diisopropylsilylphenyl)aminoquinoline). Surprisingly, only the diarylamido/bis(phosphine) PNP system showed any DHBTA reactivity. The specific PNP ligand (bearing two diisopropylphosphino side donors) used in the screen showed DHBTA activity inferior to SiNN. However, taking advantage of the ligand optimization opportunities presented by the PNP system The products of dehydrogenative borylation of terminal alkynes (DHBTA), alkynylboronates, are versatile building blocks in synthetic chemistry. Their synthetic value derives not just from the direct use in C\u2013Cet al.: deprotonation of alkyne by n-BuLi, followed by reaction with a boric ester and quench with anhydrous acid.et al.et al. also recently demonstrated that certain borenium cations can react with terminal alkynes to give alkynylboronates.2 and sp3 C\u2013H bonds, catalysis of direct coupling of a C\u2013H bond with a B\u2013H bond (2)\u2013H and C(sp3)\u2013H bonds, for the relatively acidic C(sp)\u2013H bonds (pKa \u223c 25) of terminal alkynes, the C\u2013H activation itself is generally not a difficult task and C\u2013H bond selectivity would not typically be an issue. On the other hand, in contrast to the non-olefinic C(sp2)\u2013H and C(sp3)\u2013H substrates, a combination of a triple C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, a B\u2013H bond and a metal catalyst is very likely to lead to hydroboration.2 (the by-product of DHBTA) may also be a concern.The classical synthesis of alkynylboronates was developed by Brown 1-Ir-COE and 21-Ir-Bpin, ca. 10 turnovers per min) with a variety of alkyl-, aryl- and silyl- terminal alkynes in high yield. However, the catalyst longevity was limited to ca. 100 turnovers. Very recently, Tsuchimoto et al. described DHBTA catalysis by Zn(OTf)2/pyridine using 1,8-nathpthalenediamidoborane.ca. 1 turnover per hour) even at 100 \u00b0C. Our group also reported that (POCOP)Pd complexes are modest DHBTA catalysts for some substrates.42In 2013, we reported the first example of catalytic DHBTA performed by Ir complexes of a SiNN pincerThe discovery of the prowess of the SiNN ligand in DHBTA was rather serendipitous, and we sought to explore the associated ligand space in a more systematic fashion. Here we report the exploration of a series of Ir complexes of related ligands as potential catalysts in DHBTA that has led to the discovery of a new highly active, much more long-lived catalyst with a broader scope, as well as to the insight into the role of possible intermediates in DHBTA.1-Ir-COE in DHBTA, we decided to examine a series of ligands that systematically explored variations of the SiNN ligand features or replaced it with hemilabile donors (3-H to 7-H). For 8-H and 9-H, the silane segment and the central amido donor were maintained while the quinoline moiety was eliminated (8-H) or substituted with a phosphine donor (9-H). We also included the PNP ligand (10-H) and the PCP/POCOP ligands (11-H to 14-H) because these are commonly used pincer ligands with a rich history of C\u2013H activation chemistry with Ir.In light of the success of features . From 2-i.e.2-H,473-H, 4-H, 5-H, 6-H,487-Hvia Buchwald\u2013Hartwig coupling of 8-bromoquinoline with various anilines or 8-aminoquinoline with various bromoarenes. 8-H was prepared via the intermediate S1. The synthesis of S1 relied on the same selective dilithiation of bis(2-bromo-4-methylphenyl)amine we previously used in the synthesis of S2,S1 was isolated in 86% yield by column chromatography. Treatment of S1 with n-BuLi, followed by addition of iPr2SiHCl and workup gave 8-H in 73% yield. The new SiNP ligand 9-H was prepared from S2 through a similar protocol.The syntheses of ligands used in the screening of DHBTA are shown in 1-Ir-COE precatalyst in situ from 1-Na and [(COE)2IrCl]2 . They were deprotonated with 1 equiv. of NaN(SiMe3)2in situ, allowed to react with 0.5 equiv. of [(COE)2IrCl]2 in C6D6 and the resultant solutions were tested for catalytic DHBTA activity. In the case of PCP/POCOP ligands 11\u201314, we isolated dihydride complexes (211-Ir-H212-Ir-H2H413-Ir-C and 14-Ir-COE) to be used in DHBTA testing.In our original DHBTA report,)2IrCl]2 produced2H413-Ir-C was obtained after modification of previously reported procedures for related compounds (13-H with [(COE)2IrCl]2 at 80 \u00b0C overnight in toluene resulted in a dark red solution that contained ca. 85% of the desired product (31P NMR evidence). Column chromatography allowed for the collection of 99% pure 13-Ir-HCl in 22% yield. This portion of 13-Ir-HCl was then treated with a slight excess of NaOtBu in toluene, degassed, and then stirred under an atmosphere of ethylene for 30 min. After filtration and removal of volatiles under vacuum, analytically pure 2H413-Ir-C was obtained as a dark brown solid in 66% isolated yield (based on 13-Ir-HCl). 14-Ir-COE was synthesized by reacting the previously reported 14-Ir-HCltBu and COE in C6D6 was selected as the alkyne for testing. We mimicked the conditions that were successful for the SiNN ligand 1, with 1 mol% Ir loading and 2 equiv. of HBpin used at ambient temperature in C6D6 solvent. The results are summarized in 10-H showed any DHBTA reactivity. In all other cases, no evidence for the DHBTA product A1-Bpin was visible by 1H NMR spectroscopy after 1 h. In general, sluggish and nonselective hydrogenation and hydroboration was observed for 2-H to 9-H, and for the iso-propyl PCP/POCOP iridium complexes (2H413-Ir-C and 14-Ir-COE). For tert-butyl PCP/POCOP iridium complexes (211-Ir-H and 212-Ir-H), a mixture of trans-alkenylboronate (A1-1) and cis-alkenylboronate (A1-2) were observed as major products. The use of 10-H resulted in 76% A1-Bpin after 10 min and 90% (NMR evidence) after 1 h, with about 3% of 4-ethyltoluene . We also tested one of the most active arene borylation catalyst systems ([(COD)Ir(OMe)]2 + 4,4\u2032-di-tert-butyl-bipyridine)4-Ethynyltoluene (210-Ir-HA1-H), trimethylsilylacetylene (A2-H), and 1-hexyne (A3-H) (210-Ir-H in the DHBTA of 4-ethynyltoluene (A1-H) was similar to the catalyst generated from 10-Hin situ. DHBTA of trimethylsilylacetylene (A2-H) was finished in 1 h and gave an excellent yield of A2-Bpin. The catalytic activity of 210-Ir-H towards A3-H was significantly lower than towards A1-H and A2-H and only 50% yield was achieved after 3 h. A small amount of the hydrogenation product A1-3 was observed in DHBTA of A1-H, but no hydrogenation products were detected in the reactions of A2-H and A3-H.With this lead in hand, we tested isolated e (A3-H) . The eff210-Ir-H fell somewhat short of the SiNN-based catalysis, where >95% yield of A1/2/3-Bpin was obtained in <10 min and without any hydrogenation side products. Nonetheless, we were encouraged by the results because the PNP framework offers facile opportunities for optimization of the ligand via substituent variation. We selected previously reported PNP ligands 15-H,5016-H,17-H15-H is an oil that is difficult to purify; however, the Li derivative (15-Li) could be isolated in in 56% yield as a pure solid. 15-Li was then reacted with 0.5 equiv. of [(COE)2IrCl]2 to yield 15-Ir-COE. 16-Ir-COE17-Ir-COE were synthesized via one-pot reactions by deprotonation of the neutral ligands in situ and treatment with [(COE)2IrCl]2.The effectiveness of 15-Ir-COE, 16-Ir-COE, 17-Ir-COE), 210-Ir-H, and the previously reported 1-Ir-COE were all tested in DHBTA by using A1-H as the substrate with 2 equiv. of HBpin at ambient temperature in C6D6 solvent. The results are summarized in 15-Ir-COE, 17-Ir-COE, 210-Ir-H, as well as 1-Ir-COE gave excellent yields of A1-Bpin at ambient temperature, whereas 16-Ir-COE did not (entry 4) and was eliminated from further consideration. At 0.25% Ir, 17-Ir-COE showed superior reactivity to 1-Ir-COE, 210-Ir-H, and 15-Ir-COE by producing 92% A1-Bpin in 10 min. 1-Ir-COE gave 43% yield after 1 h (entry 6) and the yield did not increase with longer reaction times, suggesting faster catalyst decomposition for the SiNN-based catalyst. 17-Ir-COE was able to effect 100% conversion of A-1H and 85% yield of A1-Bpin (NMR evidence) even at 0.025% loading in only hours at ambient temperature. The reaction rate was higher at 60 \u00b0C (entry 12) without loss in yield. The 84% yield of A1-Bpin at 0.025 mol% catalyst loading (entry 12) corresponds, impressively, to 3400 turnovers. Under incomplete conversion with 0.01 mol% loading (entry 13), a turnover number of 6500 was achieved after 2 h at 60 \u00b0C. In terms of chemoselectivity, 1-Ir-COE is superior in DHBTA of A1-H as it gave A1-Bpin as the product exclusively; 2\u201310% of hydrogenation product A1-3 was observed in all reactions catalyzed by the (PNP)Ir complexes Ir(COE) complexes , as well as 3-methyl-3-trimethylsiloxy-1-butyne (A5-H), trimethylsilyl propargyl ether (A6-H), 4-dimethylamino-phenylacetylene (A7-H), N-tosylated allyl propargyl amine (A8-H), and dimethyl 2-allyl-2-(prop-2-yn-1-yl)malonate (A9-H) were chosen as representative substrates for aromatic, silyl, aliphatic terminal alkynes, propargyl derivatives and 1,6-enynes, respectively and comparable yields/side product (A6-1 for A6-H) were obtained. No DHBTA products were observed for phenyl propargyl sulfide, 3-ethynylpyridine, 4-cyano-1-butyne, 3,3-diethoxy-1-propyne, and methyl propiolate with 0.1 mol% 17-Ir-COE. A1-Bpin, A5-Bpin and A8-Bpin could be easily purified by recrystallization and were isolated in good yields in preparative-scale reactions. In contrast, 1-Ir-COE requires 1% loading for high yields of A1-, A2-, A4-, and A5-Bpin, and is altogether ineffective for the synthesis of propargyl derivatives A6- and A8-Bpin . A mercury drop test17-Ir-COE loading and A1-H as substrate. No significant yield changes were observed for either A1-Bpin or the major side-product A1-3 which suggested that the catalysis is homogeneous.To further explore the catalytic reactivity of ectively . For A1-C2v-symmetric structure, and because a number of its iridium complexes are already known,10 for this study. We were particularly interested in determining the possible products arising from combining the 10-Ir fragment with HBpin, terminal alkynes, and alkynylboronates and their catalytic competence.In order to gain new insight into the reaction mechanism, we set out to examine conceivable intermediates in DHBTA. Because of its NMR-friendly 21-Ir-Bpin can be synthesized by reacting 1-Ir-COE with 5 equivalents of HBpin,21-Ir-Bpin exhibited the same catalytic activity as 1-Ir-COE. Treating 210-Ir-H with 5 equivalents of HBpin, however, led to a mixture of 3Bpin10-Ir-H and 10-Ir-HBpin in equilibrium with free H2 in its 1H NMR spectrum, and the peak sharpened upon 11B decoupling and \u201312.4 ppm in the 1H NMR spectrum at ambient temperature. The resonance at \u20135.3 ppm (\u03c91/2 = 35 Hz) sharpened upon 11B decoupling level of theory, see details in ESI10-Ir-p-tol; the vinylidene complex 10-Ir-v-tol; and the alkynyl boryl complex 10-Ir-ynlBpin-tol and 25.6 (11%) ppm respectively in the 31P{1H} NMR spectrum Ir precursor was reacted with A1-Bpin under milder conditions. We first attempted to mix 210-Ir-H with A1-Bpin with subsequent rapid removal of volatiles. The residue was redissolved in C6D6 and analyzed by 1H and 31P NMR spectroscopy. The major product was assigned as the alkynylboronate \u03c0-complex 10-Ir-p-tol of the 1H NMR resonances of the ortho-hydrogens of the p-tolyl group in the coordinated A1-Bpin. Such downfield chemical shift is characteristic of internal aromatic alkyne \u03c0-complexes.10-Ir-p-tol to 10-Ir-v-tol proceeded at an appreciable rate at ambient temperature (about 50% after 15 h) and precluded the isolation of pure 10-Ir-p-tol. We surmised that a more electron-poor alkyne should be thermodynamically less predisposed to form a vinylidene,A1-Bpin with A10-Bpin as the reactant than the analogous transformation of 10-Ir-p-tol. Similarly to 10-Ir-p-tol, the aromatic proton signals of the 2,6-positions on A10-Bpin in 3tol10-Ir-p-F were shifted downfield to 8.22 ppm in the 1H NMR spectrum. In the 13C NMR spectrum, the carbon signal of alkynyl\u2013C scale\" fill=\"currentColor\" stroke=\"none\">C\u2013B) in 3tol10-Ir-p-F (\u03b4 105.7) was slightly downfield of that in free A10-Bpin, as expectedEsteruelas and L\u00f3pezIr-p-tol , and itsreactant and mixe10-Ir-HBpin, 210-Ir-Bpin, 10-Ir-v-tol, and 3tol10-Ir-p-F in the solid state by X-ray diffractometry on corresponding single crystals. The structure of 10-Ir-HBpin analysis of 10-Ir-HBpin and 12-Ir-HBpin in the gas phase using the M06 functional was also performed. DFT calculations show 10-Ir-HBpin possesses shorter Ir\u2013B and Ir\u2013H bond distances and a B\u2013H bond distance 0.2 \u00c5 longer than 12-Ir-HBpin which was judged to be a \u03c3-borane complex, suggesting greater degree of B\u2013H bond activation in 10-Ir-HBpin. The structure of 210-Ir-Bpin ((amido) and the two boryls with an acute B\u2013Ir\u2013B angle (68.2\u00b0). The Y-shaped geometry is expected for a five-coordinate d6 complex(amido)) and two strong \u03c3-donors (two boryls). The two Ir-bound Bpin fragments display essentially the same metrics, and the associated Ir\u2013B distances are similar to the analogous Ir\u2013Bpin distances reported in the literature (2.02\u20132.07 \u00c5).2 plane are very close to the previously reported 21-Ir-Bpin (210-Ir-Bpin should be unambiguously viewed as an Ir(iii) diboryl complex.We were able to determine molecular structures of 10-Ir-v-tol and 3tol10-Ir-p-F 2N]Ir PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH2 vinylidene complex reported by Fryzuk.3tol10-Ir-p-F, A10-Bpin is bound to iridium in an \u03b72 fashion (Ir\u2013C1: 2.165(11) \u00c5, Ir\u2013C2: 2.101(12) \u00c5) and the Ir\u2013C distances are within the range of other square planar Ir(i) alkyne complexes. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond (1.304 \u00c5) and the bending of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013Cipso (147.5(11)\u00b0) and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013B (161.9(11)\u00b0) away from 180\u00b0 indicate back-donation from the iridium center to the \u03c0* orbitals of C PBM data was replaced with SVG by xgml2pxml: 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0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond.The coordination environment about Ir in the structures of -p-F3tol can be dMePNPiPr)Ir complexes played in DHBTA, these compounds were examined in reactions with the three components in DHBTA: a terminal alkyne (substrate), HBpin (substrate), and H2 (by-product). 10-Ir-HBpin was reacted with three different terminal alkynes to study the boryl transfer ability: A1-H, A2-H and A10-H and unidentified iridium compounds in 1 h at ambient temperature. After overnight, 210-Ir-H was the only observable species by 31P NMR spectroscopic analysis. Lack of observation of A1-4 in catalytic reaction mixtures suggested that 10-Ir-v-tol is not present in significant concentrations during catalysis. Treating 3tol10-Ir-p-F with 1 equivalent of HBpin at ambient temperature cleanly led to 83% 10-Ir-HBpin formation after 3 h was also observed.perature , top. Onfter 3 h , bottom;MePNPiPr)Ir compounds as pre-catalysts. The catalytic reactions were carried out in the fashion consistent with our other studies \u2013 the Ir compound was treated with 200 equiv. of HBpin, followed by 100 equiv. of the terminal alkyne . When 210-Ir-H was treated with excess HBpin, a yellow mixture of 10-Ir-HBpin and 3Bpin10-Ir-H immediately formed before the addition of alkyne. Not surprisingly, essentially identical yields of A1-Bpin and hydrogenation side-product A1-3 was observed when using 10-Ir-HBpin and 210-Ir-H as pre-catalysts. The use of 10-Ir-v-tol did lead to the formation of A1-Bpin, but in a significantly smaller yield than with 10-Ir-HBpin and 210-Ir-H. In contrast, 210-Ir-Bpin showed no DHBTA at all after the first 10 min and only gave 37% A1-Bpin after 3 h. The inertness of 210-Ir-Bpin in the DHBTA correlated with its lack of reactivity in the stoichiometric reactions described above. In the two reactions with A10-H, 210-Ir-H and 3tol10-Ir-p-F led to the same yield of A10-Bpin and the hydrogenation side-product A10-1 (4-CF3-C6H4-C2H5) at the 10 min and the 1 h mark.210-Ir-Bpin and the vinylidene complexes analogous to 10-Ir-v-tol can be firmly ruled out as intermediates in the DHBTA catalysis by (PNP)Ir complexes. Interestingly, this raises the question of whether the previously reported (SiNN)Ir catalysis actually requires 21-Ir-Bpin as an intermediate or if it is merely an off-cycle precursor that can access the catalytic cycle rapidly enough.On the basis of the stoichiometric and catalytic experiments the diboryl complexes analogous to 17-Ir-COE, useful yields were obtained with 0.025% loading of catalyst, corresponding to thousands of turnovers. Good to excellent yields were obtained under mild conditions for aryl-, silyl-, and alkyl-substituted terminal alkynes, even propargyl derivatives and 1,6-enynes. Unlike the strict chemoselectivity in the (SiNN)Ir system, <10% hydrogenation products were observed as the main side-products in all the (PNP)Ir systems with arylacetylene substrates. This has not precluded isolation of alkynylboronate products in 70\u201382% yields on preparative scale.Building on a recent report of successful dehydrogenative borylation of terminal alkynes (DHBTA) with a pincer iridium catalyst,10 were synthesized and examined as potential intermediates in the catalytic cycle via testing in stoichiometric and catalytic reactions. The vinylidene (10-Ir-v-tol) and diboryl (210-Ir-Bpin) complexes reacted too slowly with either terminal alkynes or HBpin under the conditions of catalysis, which ruled them out of the catalytic cycle of the 10-Ir system. The inactivity of 210-Ir-Bpin is in contrast to the analogous 21-Ir-Bpin10-Ir-HBpin) and the alkynylboronate \u03c0-complex (3tol10-Ir-p-F) showed nearly identical performance to 210-Ir-H indicating that they either are intermediates in the catalytic cycle or are connected to such via a low-barrier pathway. Although the full mechanistic picture remains uncertain, the presently reported results strongly suggest that a pincer ligand containing an amido donor is key to an active DHBTA catalyst with iridium. An intriguing possibility is that this is related to the facile migration of boryl from the metal to the amido nitrogen we recently discovered for 21-Ir-Bpin and 21-Rh-Bpin.80Several iridium complexes of the symmetric PNP ligand Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file.Supplementary movieClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Controlling the steric environment in U2)(\u03b75-Cp*)] enables selective formation of either mononuclear U(v) or dinuclear U(iv) oxo and nitrido complexes. v) neutral terminal oxo complex and a U(v) sodium uranium nitride contact ion pair are described. The synthesis of the former is achieved by the use of tBuNCO as a mild oxygen transfer reagent, whilst that of the latter is via the reduction of NaN3. Both mono-uranium complexes are stabilised by the presence of bulky silyl substituents on the ligand framework that facilitate a 2e\u2013 oxidation of a single U(iii) centre. In contrast, when steric hindrance around the metal centre is reduced by the use of less bulky silyl groups, the products are di-uranium, U(iv) bridging oxo and (anionic) nitride complexes, resulting from 1e\u2013 oxidations of two U(iii) centres. SQUID magnetometry supports the formal oxidation states of the reported complexes. Electrochemical studies show that the U(v) terminal oxo complex can be reduced and the [U(iv)O]\u2013 anion was accessed via reduction with K/Hg, and structurally characterised. Both the nitride complexes display complex electrochemical behaviour but each exhibits a quasi-reversible oxidation at ca. \u20131.6 V vs. Fc+/0.The synthesis and molecular structures of a U( U(ii) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO complexes requires the use of bulky supporting ligands.in situ generation and involvement in C\u2013H activation had been proposed and studied computationally.17The study of well-defined molecular complexes of uranium is a thriving field of research,1.000000,.000000 s2iii) mixed sandwich complexes of the general type [U{\u03b78-C8H6-2}(\u03b75-CpR\u2032\u2032)THF] (R = iPr (1), Me (2)). In particular, the reductive transformations of CO2 using the complexes [U{\u03b78-C8H6-2}(\u03b75-Cp4R\u2032Me)THF] (A) can be largely controlled by varying the size of R\u2032 .A that exhibit a clear trend between the effect of steric environment and the outcome of the possible reductive transformations, when the analogous complexes in which the SiMe3 group had been replaced by the bulkier SiiPr3 group were reacted with CO2, either intractable reaction mixtures were obtained or the reductive disproportionation of CO2 was promoted exclusively.e.g. RN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 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0000000000000000000000000000000000 0000000000000000000000000000000000\tO) as model substrates for CO2 might be informative.20We have previously demonstrated the significance of the steric environment around the uranium centre in controlling the reductive coupling of CO6D6 solution of [U{\u03b78-C8H6-2}(\u03b75-Cp*)THF] (1) with a slight excess (1.05\u20131.1 eq.) of tBuN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO under an Ar atmosphere resulted in an immediate colour change to brown red. 1H-NMR spectroscopy showed complete consumption of (1) and the formation of a new uranium species and free tBuNC (further confirmed by GC-MS of the trapped volatiles of the reaction mixture). The 29Si{1H}-NMR spectrum of the product displayed a single resonance at \u201373 ppm, shifted downfield from \u2013129 ppm in (1) suggesting that a change in the formal oxidation state of the uranium centre of (III) to (V) had taken place, in accordance with the general trend observed by Evans et al.v) terminal oxo complex {U[\u03b78-C8H62](\u03b75-Cp*)O} (3), and was confirmed by X-ray crystallography (Reaction of a brown-olive green Clography .3) (1.826(3) \u00c5) is shorter than that found in the U(v) terminal oxo complex [Ph3PMe][U(O)(CH2SiMe2NR\u2032)(NR\u20322)2] (1.847(2) \u00c5),v) complexes [U(O)(NR\u20322)3] (1.817(1) \u00c5),TIPS(O)] (1.856(6) \u00c5, TRENTIPS = [N(CH2CH2NSiiPr3)3]3),RArO)tacn)U(O)] (1.848(8) \u00c5; R = tBu, Ad; tacn = triazacyclononane),2U(O)(ODipp) (1.859(6) \u00c5, Dipp = 2,6-iPr2-C6H3),tBu)3}4K] (1.825(2) \u00c5)4][trans-U(NR2\u2032)3(O)CN].iv) (137\u2013140\u00b0) and U(iii) (150\u2013155\u00b0) mixed sandwich complexes supported by these ligands;3) was further characterised by spectroscopic7D8) gave an effective magnetic moment (\u03bceff) of 2.49 \u03bcB, very close to the theoretical value of 2.54 \u03bcB for an f1 system (see below for further details and SQUID magnetometry).The U\u2013O bond length in (3) was repeated on a larger scale, a second species co-crystallised with (3), and fractional crystallisation produced a small crop of crystals suitable for single crystal X-ray diffraction. The latter revealed the product to be the tBuNC adduct of (3) [U(\u03b75-Cp*)O(\u03b71-CNtBu)] (4), and the molecular structure is shown in When the synthesis of (4) is the elongation of the U\u2013O bond by almost 0.1 \u00c5 as compared with that in (3), and also with the U(V) PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds compared above, with the exception of that in [U(O)(NR\u20322)3] (R\u2032 = SiMe3).vide infra) revealed \u03bdNC at 2179 cm\u20131 for the isocyanide ligand in (4), a value very close to those observed in [UCp*2(NMe2)(tBuNC)2]BPh4 (3(CNC6H11)(NCMe)]+ cation;4) is also comparable (within esd's) to those in the latter complexes, while the small deviation of the C\u2013N\u2013C(tBu) from linearity presumably alleviates steric congestion around the metal centre. The Ct(COT)\u2013U1\u2013Ct(Cp*) angle is slightly more obtuse (ca. 2\u00b0) than that in (3), while the Ct(Cp*)\u2013U1 and Ct(COT)\u2013U1 distances are slightly elongated but within the range observed for previously reported complexes supported by these ligands.The most salient feature of (C)2]BPh4 and the 4) in better yields from the reaction of (1) with tBuNCO were unsuccessful, leading to mixtures of (3) and (4), and indeed the tBuNC ligand in (4) is very labile and any attempted isolation or manipulation of (4) via operations in vacuo invariably again led to mixtures of (3) and (4). In order to isolate (3) free from (4), the best route involved the reaction of (1) with tBuNCO followed by repeated dissolution in pentane and subsequent evaporation, a method used by Andersen and Evans et al. to obtain base-free Cp* lanthanide complexes,3) in 55% yield. Reaction of a C6D6 solution of the resultant microanalytically pure (3) with one equivalent of tBuNC resulted in small but discernible shifts of the resonances due to (3) in the 1H-NMR spectrum and which we ascribe to the formation of (4). Similarly, in situ IR spectroscopy showed that, upon reaction of (3) with 1 equivalent of tBuNC in methyl\u2013cyclohexane, two new peaks appeared, one at 2134 cm\u20131 (\u03bdNC in free tBuNC) and one at 2179 cm\u20131 assigned to \u03bdNC in (4).Attempts to isolate (v) terminal oxo complex (3) proceeds via the isocyanide adduct (4): the use of tBuNCO as an efficient oxygen transfer reagent1) and the formation of tBuNC and hence (4) (probably via a concerted reaction), and ultimately (3) after work-up (The above data suggest that the synthesis of the novel U( work-up .iv) complex {U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-O) (5) from the reaction of (1) with a mixture of NO/CO.5), the isolation of the mononuclear terminal oxo U(v) complex (3) would appear surprising. We therefore decided to investigate whether (3) could be prepared using alternative oxygen transfer reagents. Reaction of (1) with exactly 0.5 equivalents of N2O (administered accurately via a T\u00f6epler line) in C7D8 at \u201378 \u00b0C resulted in an immediate colour change to bright red, leading to the clean formation of (5) as evidenced by 1H and 29Si{1H}-NMR spectroscopy, and the \u03bc-oxo complex was isolated as the sole product in very good yields terminal oxo complex (3) and the U(iii) precursor (1) were mixed in C7D8, no reaction was observed at RT and conversion to the \u03bc-oxo complex (5) (ca. 25% spectroscopic yield relative to (1)) was observed only after heating at 45 \u00b0C over three days.4) indicate that these two reactions most likely proceed via different mechanisms. The case of N2O would be consistent with a concerted mechanism involving a dinuclear intermediate in which N2O bridges, and then eliminates N2 leading to a dinuclear \u03bc-oxo product. However for tBuNCO, the formation of mononuclear (4) after the oxo transfer step, stops any further reaction with (1) that could lead to (5), due to the steric congestion imposed by both the TIPS groups and the tBuNC ligand. To further test this hypothesis, the less sterically hindered homologue of (1), [U{\u03b78-C8H6-2}(\u03b75-Cp*)THF] (2) was reacted with tBuNCO. In this case the reaction furnished cleanly the dinuclear \u03bc-oxo U(iv) complex {U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-O) (6) as evidenced by its NMR spectroscopic data that were in excellent agreement with those previously reported.1) and (2) have very similar [U(III)] \u2194 [U(IV)] redox potentials highlights the importance of the steric hindrance imposed by the silyl substituents on the 8-membered ring in dictating the outcome of the reactions of (1) and (2) with tBuNCO. In the case of (1), reaction with tBuNCO results in a single 2e\u2013 oxidation of the metal centre leading to the U(v) complex (4), and hence (3), whereas in the case of (2) this reaction results in two 1e\u2013 oxidations leading to the dinuclear U(iv)\u2013U(iv) complex (6) .3) using other isocyanates or oxo transfer reagents were uniformly unsuccessful leading to intractable reaction mixtures. Interestingly when Me3SiNCO was reacted with (1), the U(iv) complex {U[\u03b78-C8H63)2](\u03b75-Cp*)(OSiMe3)} (7) was isolated as the sole product of the reaction.7) can reasonably be explained by the formation of a short-lived complex which, due to the oxophilicity of the SiMe3 group, undergoes a formal reduction to produce the observed U(iv) complex (7) and presumably cyanogen (CN)2 . Similar reactivity of U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds towards silicon electrophiles has been observed by Andersen et al.8Attempts to generate (3) suggested that the steric protection afforded by the U[\u03b78-C8H62](\u03b75-Cp*) mixed sandwich framework might be exploited to access the analogous uranium nitride. The highly reducing nature of (1) (UIII/UIV \u20132.13 V vs. Fc+/0), suggested reduction of N3\u2013 as a possible method for installing the nitride ligand.13Given the similarities between nitride and oxo ligands,1) with NaN3 were isolated in moderate yield (ca. 30%), together with other product(s) which could not be unambiguously characterised despite repeated attempts. X-ray diffraction studies showed (9) to be the nitride complex [U{\u03b78-C8H6-2}(\u03b75-Cp*)(\u03bc-N)(\u03bc-Na{OEt2}2)], best described as a sodium uranium nitride contact ion pair terminal nitride anion supported by the TRENTIPS ligand, as well as its U(vi) neutral analogue.9) is comparable to that in the U(v) nitride complex [U(TRENTIPS)N]\u2013[Na(12-c-4)2]+ (1.825(15) \u00c5) where the two ions are separated, but is shorter than the one found in [U(TRENTIPS)(\u03bc-N)(\u03bc-Na)]2 (1.883(4) \u00c5) where a N\u2013Na interaction is also present.6F5)3BNU(V)(NMestBu)3][NnBu] (1.916(4) \u00c5) and [(C6F5)3BNU(VI)(NMestBu)3] (1.880(4) \u00c5)vi) complex [U(TRENTIPS)N] the U\u2013N bond in (9) is similar within esd's.9) is shorter than the ones found in [U(TRENTIPS)(\u03bc-N)(\u03bc-Na)]2 (2.308(5) \u00c5)TIPS)(\u03bc-N)(\u03bc-Na{15-c-5})] (2.291(5) \u00c5),9) is elongated compared to (3) and (4) while the Ct(COT)\u2013U1\u2013N1 and Ct(Cp*)\u2013U1\u2013N1 angles are significantly more acute than the ones found for the corresponding angles Ct\u2013U1\u2013O1 angles in (3). The reason for these differences is unclear.Liddle 9) was further characterised by spectroscopic\u03bceff (Evans method) was determined to be 2.21 \u03bcB , which is in reasonable agreement with the value of 1.99 \u03bcB for [U(TRENTIPS)N]\u2013,v) complexes.36Complex (23Na NMR spectrum of (9) in THF revealed a single, very broad (\u0394\u03bd1/2 = 8300 Hz) resonance centred at ca. \u03b4 200 ppm suggesting that the interaction of the sodium cation with the paramagnetic uranium centre is maintained in solution (cf. (10), vide infra).The iii) complex [U{\u03b78-C8H6-2}(\u03b75-Cp*)THF] (2) affords the bridging \u03bc-oxo complex (6), the reaction of (2) with a slight excess of NaN3 (1.5 mol eq.) in a C7H8/THF solvent mixture (ca. 2\u2009:\u20091) was explored. Indeed, after work-up and re-crystallisation from THF/Et2O, brown-red crystals of the bridging nitride complex [{U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-N)]\u2013[Na(THF)6]+ (10) suitable for X-ray diffraction studies were isolated in 81% yield (\u03bc-N3)UCp*2]4,2(\u03bc-I)2}3(\u03bc3-N)] (2.152(3)\u20132.138(3) \u00c5). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tU bonding interactions (1.95\u20132.12 \u00c5).9), that in (10) is significantly elongated as expected. The U\u2013N\u2013U bond in (10) has significantly deviated from linearity, which is a common structural motif for many bridging U nitride complexes(IV)\u2013N\u2013U(IV)]\u2013, [U(IV)\u2013N\u2013U(V)] and [U(IV)\u2013N\u2013U(VI)(O)]\u2013 complexes supported by bulky silyl amide ligands,tBu)3)]2 (106.1(2)\u00b0),10) is identical to the U\u2013O\u2013U bond angle found in the \u03bc-oxo complex {U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-O) (6)6) and that shortening might account for the slightly more acute Ct(COT)\u2013U\u2013Ct(Cp*) angles in (10) compared to the ones found in (6) (139.7(16)\u00b0 and 140.0(16)\u00b0).18The two U\u2013N bond lengths (N1\u2013U1 2.063(5) \u00c5, U2\u2013N1 2.066(5) \u00c5) in the anionic dimer are essentially the same, suggesting a delocalised [U \u2243 N \u2243 U] bonding interaction as in [Cp*10) readily loses its crystallinity due to loss of coordinated THF to yield [{U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-N)]\u2013[Na(THF)2]+ (10\u2032) as a well-defined product, as evidenced by microanalysis. As in the case of its \u03bc-oxo analogue [{U[\u03b78-C8H62](\u03b75-Cp*)}2(\u03bc-O)] (6), the 1H-NMR (C4D8O2) spectrum of (10\u2032) is consistent with a C2-symmetric structure that is retained in solution. In marked contrast to (9), the 23Na NMR spectrum of (10) in THF exhibited a sharp resonance (\u0394\u03bd1/2 = 78 Hz) at \u03b4 \u20137.94 ppm, parameters suggesting no interaction of the [Na(THF)6]+ counterion with the paramagnetic uranium anion.38Complex (2) with tBuNCO that yields the \u03bc-oxo complex (6), the bridging nitride complex (10) can be seen as the product of two 1e oxidations of the U(iii) precursor (vs. the one 2e oxidation that produces (9) in the case of the bulkier COT substituents), since the formal oxidation state of the uranium centres in (10) is +4. The \u03bceff for 10\u2032 was determined to be 3.64 \u03bcB for the dimer or 2.57 \u03bcB per uranium centre, a value consistent with a U(iv) ion (further details including SQUID magnetometry below).Similarly to the reaction of (\u03bceff for complexes (3), (9) and (10\u2032) at 300 K as determined in solution (Evans method), and in the solid state (SQUID under an applied field of 0.1 tesla); the values determined by these two methods are in fair agreement.3) exhibits a steady decline from the value of 2.16 \u03bcB at 300 K to 1.54 \u03bcB at 5 K terminal oxo complexes .The effective magnetic moment of (B at 5 K . This be9), its effective magnetic moment was found to be 2.00 \u03bcB at 300 K and 1.35 \u03bcB at 5 K (TIPS)][Na(12-crown-4)2] ,v) complexes more generally\u03c7m/T, \u03c7mT/T and \u03c7m\u20131/T).In the case of the nitride complex (B at 5 K . These v10\u2032) measured for zero-field cooled and field cooled samples coincided exactly, indicating the absence of long\u2013range interactions between spins on the two U(iv) centres. At 300 K the effective magnetic moment per U is 2.53 \u03bcB, and decreases to 0.69 \u03bcB at 2 K dianion [{3tacn)U}2(\u03bc-O)2]2\u2013 by Meyer et al. showed a \u03bceff per U of 2.73 \u03bcB at 300 K.\u03c7m) that obeys the Curie\u2013Weiss law, \u03c7m = C/(T \u2013 \u0398), where C is the Curie constant and \u0398 is the Weiss constant. The plot of \u03c7m\u20131vs. T 2](\u03b75-Cp*)}2(\u03bc-N)]\u2013 anion behaves as two non-interacting U(IV) centres. Furthermore, there is no maximum observed in the \u03c7mvs. T plot ((IV) ion (3H4 ground term) typically has minimal covalency, hence the two metal centres in 10\u2032 do not participate in exchange coupling.Magnetic susceptibility data sets for , (9) and (10\u2032) are presented in Finally, magnetic data for all three compounds (vi) complexes, the redox properties of (3), (9) and (10) were studied by cyclic voltammetry (C.V.).In order to gauge the potential for accessing terminal oxo and nitrido uranium(tBuArO)tacn)U(O)] complex reported by Meyer et al. that features a reversible oxidation,3) revealed only a quasi-reversible reduction process at \u20131.77 V vs. Fc+/0 did not alter the shape of the observed wave and no other processes were found to occur over the solvent window. This process is assigned to the [U(V)] \u2194 [U(IV)] couple, and based on this voltammogram, the reduction of (3) should be a chemically accessible process. Indeed, (3) can be chemically reduced with a slight excess of K/Hg (0.5% w/w) in the presence of 18-crown-6 in n-pentane/Et2O. The almost instantaneous reaction produced a red-pink solid that, after work-up and re-crystallisation from toluene, gave dark red rods suitable for X-ray diffraction studies which showed the product to be the U(iv) complex [U{\u03b78-C8H6-2}(\u03b75-Cp*)(\u03bc-O)K(18-c-6)] (11) (Changing the scan rate (50\u2013300 mV s6)] (11) .11) is longer than that in the U(v) complexes (3) (1.826(3) \u00c5) and [U(NR2\u2032)3O]iv) complex (4) (1.916(8) \u00c5). The K1\u2013O1 bond length is as expected shorter than the O PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tU PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u00b7\u00b7\u00b7K bonds (2.60\u20132.9 \u00c5)The U\u2013O bond length (1.891(4) \u00c5) in (11) was fully characterised by spectroscopic and analytical methods ), a value that is even more upfield than that for the U(iii) complex (1) (\u2013129 ppm), probably due to the anionic nature of (11).Complex in the anodic direction over several cycles revealed the existence of several processes in the accessible solvent window ] \u2194 [U(V)] couple. As can be seen from ca. \u20131.8 V vs. Fc+/0) is also present, which features an asymmetric current response that leads us to conclude that this is probably related to a short lived electrochemically generated species. The shape of the wave at \u20131.63 V did not change by variation of the scan rate (50\u2013350 mV s\u20131).C.V. scans of the nitride complex (s. Fc+/0 which we9) exhibits also another two irreversible processes: one anodic at 0.7 V and a cathodic one at \u20132.8 V (both vs. Fc+/0). The nature of these two irreversible processes cannot be unambiguously assigned, but they could be due to ligand activation involving the nitride moiety. Attempts to chemically oxidise (9) by reaction with mild oxidants such as I2 and AgBPh4 have thus far resulted in intractable mixtures from which only ligand decomposition could be observed spectroscopically (1H-NMR).In addition to this process, the (full) voltammogram of (10) revealed a quasi-reversible process (peak separation 87 mV) centred at \u20131.46 V vs. Fc+/0 (9) as well as for the {[U(IV)] PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t[U(IV)]}\u2013 \u2194 {[U(V)] PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t[U(IV)]} couple ([U] = U(NMestBu)3) reported by Cummins et al.(IV)]\u2013N\u2013[U(V)]} \u2194 {[U(IV)]\u2013N\u2013[U(IV)]} redox pair.Similarly, anodic scans of the bridging nitride ]\u2013N\u2013[U(V)]}, {[U(VI)]\u2013N\u2013[U(V)]} etc.), although other reasons (e.g. ligand activation) cannot be excluded. As in the case of (9) an irreversible reduction is also observed at ca. \u20132.5 V vs. Fc+/0 that as above could correspond to a mixed valence species (i.e. {[U(III)]\u2013N\u2013[U(V)]}) or arise from a ligand activation process. Given that similar processes appear in the case of (9), we envisage that they are more likely due to the latter rather than the former.Apart from this process, the voltammogram also displayed additional irreversible processes centred at anodic voltages or dinuclear U(iv) nitrido/oxo complexes depending on the size of the silyl substituents on the supporting ligands. This has led to the preparation of an anionic uranium(v) nitride complex (9) featuring a U\u2013N triple bond, as well as a neutral U(v) terminal oxo complex (3). Magnetic studies corroborate the formal oxidation states of these complexes further confirming that the 2e\u2013 oxidation leads to products featuring either one U(v) or two U(iv) metal centres depending on steric hindrance at the uranium centre. Cyclic voltammetry studies of complex (3) show that it can be readily reduced to the \u2013 anion (11), which has also been achieved chemically. Unlike (3), cyclic voltammetry studies have shown that the nitride complex (9) might be amenable to oxidation to the U(vi) species although initial attempts to do so have been unsuccessful thus far.In summary we have described how the steric environment around the metal centre can manipulate redox events at a uranium centre. This has been demonstrated by the isolation of either mononuclear U(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Polar and apolar boron-based triple bonds promote the single and double C\u2013H activation of acetone following similar coordination-deprotonation mechanisms. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB triple bonds induce C\u2013H activation of acetone to yield a (2-propenyloxy)aminoborane and an unsymmetrical 1-(2-propenyloxy)-2-hydrodiborene, respectively. DFT calculations showed that, despite their stark electronic differences, both the B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN and B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB triple bonds activate acetone via a similar coordination-deprotonation mechanism. In contrast, the reaction of acetone with a cAAC-supported diboracumulene yielded a unique 1,2,3-oxadiborole, which according to DFT calculations also proceeds via an unsymmetrical diborene, followed by intramolecular hydride migration and a second C\u2013H activation of the enolate ligand.B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR\u2032 , PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN bond enables their participation in a vast array of spontaneous [2 + 2] cycloaddition6Due to their intrinsic electron deficiency, linear compounds containing a multiply bonded, sp-hybridised boron atom are far more reactive and difficult to isolate than isolobal carbon-based compounds. Owing to their ease of derivatisation, monomeric iminoboranes of the form RB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR\u2032 compounds have been studied for over 30 years, isolobal LB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tBL compounds displaying two dicoordinate, zero-valent boron atoms long eluded isolation. Since our report of the first stable diboryne, (IDip)B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB(IDip) -imidazolidin-2-ylidene),I are inert towards H2, PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB(SIDep) -4,5-(dihydro)imidazolidin-2-ylidene), which is supported by saturated NHCs of intermediate \u03c0 acidity,2 at 80 \u00b0C to yield a 1,2-dihydrodiborene.MecAAC)\u00b7\u00b7\u00b7B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tB\u00b7\u00b7\u00b7(MecAAC) -3,3,5,5-tetramethyl-pyrrolidin-2-ylidene),I and II, activates H2 at room temperature14While linear RB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNR\u2032 and LB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tBL species B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tNAr* 2-4-tBuC6H2); TMP = 2,6-tetramethylpiperidyl), towards acetone and show that, despite their marked electronic differences, compounds II and IV activate acetone following a similar mechanism, whereas cumulene II promotes an unprecedented spontaneous double activation of acetone.Intrigued by the seeming lack of reactivity overlap between isolobal linear RB species , we wereIV in hexanes with excess acetone overnight at 70 \u00b0C resulted in clean formation of the (2-propenyloxy)aminoborane 1 = 359.9(18)\u00b0) and N1 (B1\u2013N1\u2013C4 126.92(16)\u00b0) as well as the elongation of B1\u2013N1 to a single bond (1.424(3) \u00c5). The 2-propenyloxide ligand coordinated to B1 displays a C1\u2013O1 single bond (1.343(2) \u00c5) and a terminal C1 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC2 double bond (1.320(3) \u00c5). Formally, compound 1 results from the addition of 2-propenol, the enol form of acetone, across the polar B PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tN triple bond of iminoborane IV. While there is, to our knowledge, no literature precedent for the reactivity of monomeric iminoboranes with enolisable ketones, the dimeric iminoborane 2 has been shown to undergo 1,4-enol addition to the ring-opened iminoborane dimer with acetone, acetophenone and 3,3-dimethylbutan-2-one.2,X-Ray crystallographic analysis of 1 confirms1.000000,.000000 sI proved unreactive towards acetone even under forcing conditions, diboryne II reacted rapidly with excess acetone in benzene at room temperature to yield the green-coloured 1,2-enol addition product 2 \u00c5 similar to that of its dihydrodiborene relative, (SIDep)HB PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tBH(SIDep) (1.589(4) \u00c5).3H5 moiety is twisted ca. 35.5\u00b0 out of the diborene plane and displays a pure \u03c3-donor interaction (B1\u2013C4 1.574(4) \u00c5). The planar 2-propenyloxide ligand lies at a ca. 58\u00b0 angle with respect to the diborene plane, and its bond lengths (O1\u2013C1 1.352(3), C1 PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC2 1.316(4) \u00c5) are similar to those of 1. With Kinjo and co-workers recently reporting the first diborene with two different donor ligands2 is only the second unsymmetrical diborene with respect to the anionic substituents.Whereas diboryne roduct 2 . Compoun2 at the (smd: n-pentane)lc-\u03c9PBE/6-311+g(d) level of theory provided a maximum UV-vis absorbance at 592 nm scale\" fill=\"currentColor\" stroke=\"none\">B double bond into the empty pz orbital of the carbene carbon of the SIDep ligand supporting the BOC3H5 moiety, and is responsible for the blue-green color of the compound.TDDFT calculations performed upon the optimised geometry of III with acetone did not yield the expected cAAC analogue of 2. Instead, 11B NMR data revealed a 92\u2009:\u20098 mixture of two sp2\u2013sp3 diborane products, the major one (3a) showing two broad singlets at 42.8 and \u20131.9 ppm (fwhm \u2248 130 Hz), and the minor (3b) presenting a very broad resonance at 63.0 ppm (fwhm \u2248 630 Hz) and a broad BH doublet at \u201315.0 ppm (1JB\u2013H = 50.8 Hz), suggesting a non-bridging hydride. The 1H NMR spectrum of the mixture showed very similar sets of resonances for 3a and 3b, which strongly suggests an isomeric relationship. Both compounds display one neutral cAAC ligand and one C1-protonated cAAC ligand as well as a single 1H alkene resonance . PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC2 double bond (1.3301(18) \u00c5, 2-bridged by a hydride (B1\u2013B2 B1\u2013H1 1.213(16), B2\u2013H1 1.485(17) \u00c5) positioned orthogonally to the B2C2O heterocycle 105.7(9)\u00b0) and shows a bond length of 1.721(2) \u00c5 typical of a diborane (5). The alkenylborane moiety around B1 is supported by a neutral cAAC ligand with a relatively short B1\u2013C4 bond (1.5295(19) \u00c5) and forms an angle of only ca. 19\u00b0 with the plane of the B2C2O heterocycle 14.4(2)\u00b0), which is indicative of \u03c0 conjugation. The enoxyborane moiety around B2 bears a protonated cAAC ligand displaying clear sp3-hybridisation at C24 (B2\u2013C2 4 1.6045(18), C24\u2013N2 1.4878(16) \u00c5). The structure of 3a is reminiscent of the products obtained from the reduction of (SIMes)BBr2BAr2 diborane (5) precursors . These display a central, \u03bc2-hydride-bridged, planar B2C5 heterocycle, resulting from the C\u2013H activation of one aryl substituent by an intermediate boraborylene, and coordinated on one side by a neutral SIMes ligand and on the other by the second aryl substituent.Single-crystal X-ray crystallography revealed a unique planar 2,3-dihydro-5-methyl-1,2,3-oxadiborole heterocycle displaying an endocyclic C1d do not fit the experimental data . Since 3a presents two stereocentres, one at B2, which is locked by the B2C2O ring and the asymmetrically bridging hydride, and one at the protonated cAAC carbon atom, the other possibility is that 3a and 3b could be diastereomers. This would also fit the observation that they do not exchange in solution even at high temperatures. To test this, the geometries and 11B NMR chemical shifts of the possible diastereomeric pairs derived from 3a were computed /-3a pair adequately match the experimentally-observed shifts \u2248 \u00b12 ppm). Calculations on the diastereomeric pair showed that a form with a non-bridging hydride is the most likely. This also correlates well with the observation that, unlike 3a, which shows two very broad 11B NMR resonances typical for a \u03bc2-hydride-bridged diborane, 3b shows a doublet at \u201315.0 ppm (1J11B\u20131H = 50.8 Hz), indicating a terminal hydride rather than a bridging one. The predicted 11B NMR chemical shifts for the /-3b pair are comparable to the experimental ones \u2248 \u00b13 ppm). The relative energy of /-3b, at 3.1 kcal mol\u20131 above /-3a, is consistent with the experimentally observed ratio of 92\u2009:\u20098.The predicted 3a/b is particularly remarkable in view of the fact that there is seemingly no literature precedent for a one-step, uncatalysed, 100% atom-efficient double C\u2013H activation of acetone or other enolisable ketones. We were therefore keen to investigate the mechanism of the formation of 3a/b and compare it to that of the boron enolates 1 and 2. While the reaction of dimeric iminoboranes with enolisable ketones always yielded the 1,4-enol addition products, Paetzold and co-workers showed that with acetophenone, which is less prone to enolisation, a [2 + 4] cycloaddition product can also be isolated.IV and diboryne II with acetone showed no evidence of [2 + 2] cycloaddition products or intermediates.The spontaneous formation of IV and at the ONIOM(M06-2X/6-311+G(d):PM6) level for II and III showed that acetone activation does not proceed via 1,2-enol addition, as the enol form of acetone lies 15.3 kcal mol\u20131 higher than the reactants, well above the activation energy for direct acetone addition level for IV two plausible mechanisms were investigated, the first via a 4,4-dimethyl-1,3,2-oxaboretidine [2 + 2] cycloaddition product (A), the second via concerted acetone coordination-deprotonation , 20.6 (II), 10.1 (III) kcal mol\u20131), respectively (IV) or the electron-rich, second boron centre (for II and III), to yield the cis-aminoborane 1I2, and the SIDep- and cAAC-supported cis-diborenes 2I2 and 3I2, respectively (\u0394G\u20212 = 4.0 (IV), 14.1 (II), 14.9 (III) kcal mol\u20131). Finally, the trans-aminoborane 1 and the trans-diborenes 2 and 3I4 are obtained by rotation around the B\u2013N and B\u2013B bond, respectively. Overall, the formation of 2 presents the highest energy barrier and is also the most exergonic , followed by that of 1 and 3I4 .Instead, for compounds ectively and 5. Tcis-diborenes 2I2 and 3I2 to the trans-diborenes 2 and 3I4, respectively, was further investigated to determine the rotation barrier in each case. Interestingly, DFT calculations showed two distinct mechanisms at work for the SIDep-stabilised and the cAAC-stabilised diborene, respectively scale\" fill=\"currentColor\" stroke=\"none\">B double bond into the \u03c0 backbonding to the unsaturated carbene ligands. The resulting transition state 2TS3 now displays a B\u2013B single bond, which allows facile rotation. The isomerisation process from 2I2 to 2 occurs with a low barrier of 9.7 kcal mol\u20131. In contrast, the lowest energy pathway for the cAAC analogue 3I2 proceeds via a 1,2-hydride shift from boron to the adjacent cAAC carbene carbon to yield the intermediate diborene 3I3 , in which the boron bearing the now protonated cAAC ligand is sp-hybridised. Rotation about this B\u2013CcAACH single bond and a second 1,2-hydride shift back to the boron centre then yield the trans-diborene 3I4 with a low barrier of 9.3 kcal mol\u20131. This pathway is assisted on the one hand by the facile 1,2-hydride shuttling chemistry displayed by cAAC hydroboron compounds3I3.The exergonic isomerisation step leading from the ectively . For theIII, however, the reaction does not stop at trans-diborene 3I4 . Coordination of the pendant terminal alkene to the two-coordinate boron yields adduct 3I5, which is 6.6 kcal mol\u20131 more stable. Subsequent C\u2013H activation of the methylidene moiety yields the bis(cAAC)-stabilised 1,2,3-oxadiborole 3I6 . This is the highest energy barrier in the entire reaction mechanism. 3I6 then tautomerises to compound 3a by concomitant migration of the hydride on B1 to the adjacent cAAC carbene centre and bridging of the hydride on B2 . Overall the formation of 3a from III and acetone is exergonic by 61.7 kcal mol\u20131, which explains why the intermediate diborene cannot be isolated.For cumulene rene I43 . The latIV, diboryne II and cumulene III, all activate acetone via a similar acetone coordination-deprotonation mechanism, regardless of their polar or nonpolar nature. For the iminoborane-based reaction, an enol addition mechanism and a mechanism proceeding via a [2 + 2] cycloaddition intermediate, as would normally be expected for such a polar compound, were both ruled out. For diboron compounds II and III the addition of acetone first yields a cis-diborene intermediate which isomerises to the thermodynamic trans-diborene product through a low energy barrier. Calculations showed that this isomerisation process heavily relies on the \u03c0-accepting nature of the carbene ligands, coupled, in the case of the cAAC-supported diborene, with a hydride shuttling mechanism from boron to the carbene carbon and back. These cAAC-specific properties also enable an unprecedented second C\u2013H activation of the enolate ligand to yield a novel 1,2,3-oxadiborole heterocycle, demonstrating once again the unique reactivity of cAAC-supported low-valent boron compounds.To conclude, we have shown that three linear, isolobal, multiply bonded boron compounds, iminoborane Overall this study should act as a reminder that the parallels all too eagerly drawn between organic compounds and their isoelectronic/isolobal inorganic p-block counterparts only rarely translate into actual organomimetic behaviour when it comes to reactivity or reaction mechanisms. Furthermore, this first example of reactivity overlap between polar and nonpolar boron-based triple bonds opens up new avenues for attempting reactions that may have been previously disregarded, such as the addition of nonpolar small molecules to iminoboranes or, alternatively, of polar molecules to diborynes.There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "We report the synthesis and characterization of terminal uranium(iv) hydrosulfido and sulfido complexes, supported by the hexadentate, tacn-based ligand 3tacn3\u2013. iv) hydrosulfido and sulfido complexes, supported by the hexadentate, tacn-based ligand framework 3tacn3\u2013 -5-methyl-2-hydroxybenzyl)-1,4,7-triazacyclononane). The hydrosulfido complex [3tacn)U\u2013SH] (2) is obtained from the reaction of H2S with the uranium(iii) starting material [3tacn)U] (1) in THF. Subsequent deprotonation with potassium bis(trimethylsilyl)amide yields the mononuclear uranium(iv) sulfido species in good yields. With the aid of dibenzo-18-crown-6 and 2.2.2-cryptand, it was possible to isolate a terminal sulfido species, capped by the potassium counter ion, and a \u201cfree\u201d terminal sulfido species with a well separated cation/anion pair. Spectroscopic and computational analyses provided insights into the nature of the uranium\u2013sulfur bond in these complexes.Herein, we report the synthesis and characterization of a series of terminal uranium( PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tE compounds , enabling a more detailed insight into the electronic structure and degree of covalency in this structural motif.The anhydrous coordination chemistry of the light actinides has become an active field of research since the discovery of suitable starting materials.iii) to undergo one electron oxidation resulting in dinuclear, sulfido-bridged diuranium(iv/iv) complexes rather than stabilizing the terminal sulfido ligand, S2\u2013.iv) hydrochalcogenido complexes employing H2E as the chalcogenido ligand source.Ad,MeArO)3N)U\u2013SH(DME)] 3N3\u2013 = trianion of tris(2-hydroxy-3-(1-adamantyl)-5-methylbenzyl)amine). Due to their potential application as catalysts, transition metal hydrochalcogenido complexes have received considerable interest in recent years.iv) hydroxo complex, namely [3mes)-U\u2013OH], was found to be the key intermediate in the electrocatalytic production of dihydrogen from water.9In contrast to the rapidly increasing number of reported terminal uranium oxo complexes,iii) complexes [3tacn)U] 3tacn3\u2013 = trianion of 1,4,7-tris--1,4,7-triazacyclononane) and [3N)U(DME)] 3N3\u2013 = trianion of tris(2-hydroxy-3-(1-adamantyl)-5-methylbenzyl)amine) efficiently activate the elemental chalcogens 2E.via (poly-)chalcogenido as well as bis-hydrochalcogenido bridges was observed.Ad,RArO)3tacn)3\u2013 .iii) precursor [3tacn)U] (1) 3tacn3\u2013 = trianion of 1,4,7-tris(3-(1-adamantyl)-5-methyl-2-hydroxybenzyl)-1,4,7-triazacyclononane) allowed for synthesis of the here reported monomeric uranium (hydro-) chalcogenido complexes. More importantly, the bulky adamantyl groups effectively prevent dimerization upon deprotonation of the SH\u2013 ligand; thus, yielding the targeted uranium terminal sulfido complex for direct comparison to the bonding situation in U complexes with \u03b71-SH and \u03b71-S ligands. The presence of crown ethers or cryptands in the deprotonation step not only increases the solubility of the formed metal salts, but additionally allows for the quantitative evaluation of the bonding situation in a U\u2013S\u2013H versus a U\u2013S\u00b7\u00b7\u00b7K complex.We previously demonstrated that the uranium(iii) complex [3tacn)U] (1) with various S atom transfer reagents, such as Ph3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS or elemental sulfur, does not yield terminal U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS complexes. Either a reaction was not observed at all or an intractable mixture of compounds without any isolable product was received. Finally, the synthesis of terminal uranium(iv) hydrosulfido and sulfido complexes was successfully achieved by treatment of complex 1 with one equivalent of H2S. The dropwise addition of 0.8 M H2S in THF to a red-brown solution of 1 in THF reproducibly affords the uranium(iv) hydrosulfido complex [3tacn)U\u2013SH] (2) in excellent yields with concomitant evolution of H2 gas . The mononuclear complex [3tacn)U\u2013SH] exhibits a seven-coordinate uranium ion in a face-capped octahedral coordination environment (2 were determined to be 2.844(4) and 2.775(2) \u00c5, respectively. This is in good agreement with other reported uranium\u2013sulfur single bonds (2.588(1)\u20132.907(3) \u00c5)\u2013 ligand is situated on the C3 axis of the molecule in the axial position, trans to the tacn anchor. Since the chalcogen-bound H atom could be located in the difference Fourier map, the U\u2013S\u2013H angle was determined to be 152\u00b0 and 156\u00b0, respectively. The U\u2013Oaryloxide distances are 2.152(4) \u00c5 and 2.188(3) \u00c5, respectively, and the U\u2013Ntacn bond lengths are 2.680(5) \u00c5 and 2.650(4) \u00c5. The uranium out-of-plane shift (Uoop), defined by the displacement of the uranium ion below the plane of the three aryloxide oxygen atoms, was measured to be \u20130.282 and \u20130.268 \u00c5, respectively. All these parameters are in good agreement with other uranium(iv) complexes supported by the 3tacn3\u2013 ligand system .Complex ironment .47 The Uiv) sulfido species, complex 2 was treated with potassium bis(trimethylsilyl)amide in THF to deprotonate the \u2013SH moiety. In order to encapsulate the potassium counterion, the reaction was performed in the presence of either dibenzo-18-crown-6 or 2.2.2-cryptand 3tacn)U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS\u00b7\u00b7\u00b7K(db-18-c-6)] (3) and [K(2.2.2-crypt)] (4) were carried out. The uranium(iv) sulfido complex 3\u00b70.62 benzene\u00b70.38 Et2O crystallizes in the monoclinic space group P21/c with one molecule per asymmetric unit, whereas 4 crystallizes in the chiral, hexagonal space group P63 with a third of one independent molecules per asymmetric unit. Both the uranium complex and the [K(2.2.2-crypt)] moiety were found on a crystallographic threefold axes. As anticipated, the sulfido ligand of the uranium(iv) complex (3) is capped by the [K(db-18-c-6)]+ cation, whereas complex [K(2.2.2-crypt)] (4) features a genuine terminal sulfido ligand with the [K(2.2.2-crypt)]+ cation in the outer coordination sphere of the complex anion . Single-ex anion .2, UIV complex 3 features a seven-coordinate uranium ion with the sulfido ligand occupying the axial position. The S\u2013K distance is 3.136(1) \u00c5, demonstrating a bonding interaction between the S2\u2013 ligand and the K+ counter ion 3tacn)U\u2013SH] av = 2.810(4) \u00c5), but slightly longer than those of other reported uranium(iv) sulfido complexes (2.442(2)\u20132.4805(5) \u00c5).1H NMR spectrum of 3 reveals a C3-symmetrical molecule in solution (vide infra), coordination of the [K(db-18-c-6)]+ crown ether leads to a loss of C3 symmetry in the crystal structure. The average U\u2013Oaryloxide distance of 2.219 \u00c5 and the mean U\u2013Ntacn bond length of 2.819 \u00c5 are slightly longer compared to UIV hydrosulfido complex 2. Interestingly, the U out-of-plane shift (Uoop) significantly decreases from \u20130.275 in 2 to \u20130.055 \u00c5 in 3; hence, the uranium center is positioned almost perfectly in the plane of the three oxygen donors. This observation is quite unusual for uranium(iv) ions in the tacn-based ligand system, and is typically only seen for high-valent UV and UVI complexes with strong \u03c0-donor ligands, such as the oxo and isoelectronic imido functionality.3 (vide infra).Like complex nter ion , left. T3O3S ligand donor set in the anionic complex \u2013 (4)\u2013 is analogous to that found for complex 3. In the case of 4, however, the potassium cation is encapsulated by the sterically encumbered 2.2.2-cryptand and located in the outer coordination sphere of the anionic UIV complex, leading to a discrete ion pair with isolated [K(2.2.2-crypt)]+ cations and \u2013 anions (4 exhibits a slightly longer uranium\u2013sulfido distance of 2.536(2) \u00c5 and\u2014along with the longer U\u2013S distance\u2014a slightly but noticeably larger Uoop of \u20130.086 \u00c5 compared to 3 (d(U\u2013S)av = 2.507(1) and Uoop = \u20130.055 \u00c5). It is suggested that the diphenyl-18-crown-6 moiety exerts a considerable steric strain that might push the sulfur atom slightly deeper into the cavity of the [((AdArO)3tacn)U] moiety, while at the same time, the uranium reduces its negative out-of-plane shift and moves closer to the sulfur atom in order to accommodate the sterically demanding potassium diphenyl-18-crown-6 moiety in the complex periphery. In addition, the seven-coordinate uranium center is chiral with an idealized C3 symmetry, affording a racemate of complex 4. After crystallization, a conglomerate of enantiomerically pure crystals was found for 4 with an A-configuration of the uranium center in the analyzed crystal.2\u20134 are stable in the solid form or in THF solution for at least 3 weeks without any notable decomposition.The connectivity of the N\u2013 anions , right. 1H NMR spectroscopy shows that compounds 2\u20134 possess C3 symmetry in solution, induced by coordination of the tacn ligand to the metal center with the hydrosulfido/sulfido ligand situated in the axial position on the C3 axis in order to investigate the complexes' symmetry at low temperatures. Upon cooling the 1H-NMR signals broaden and shift, but coalescence is not observed. The VT-NMR experiments thus suggest that, in solution, the crown ether complexated potassium ion remains in the vicinity of the paramagnetic uranium complex anion. It is further suggested that the potassium crown ether moiety fluctuates around the anion's threefold axis faster than the NMR timescale; even at very low temperatures. As a consequence, the U\u2013S bond distance of 3 relaxes in solution, leading to a weaker uranium\u2013sulfur bonding interaction .s see ESI. Hence, 2\u20134 was studied by UV/vis near-infrared spectroscopy. In the high-energy region (\u03bb < 600 nm) broad and rather intense ligand-based absorption bands as well as charge-transfer transitions are observed. In the UV region of the spectra, all three complexes exhibit an absorption band at 298 nm with an extremely high extinction coefficient ; 300 M\u20131 cm\u20131 (4)), absent in 2. This absorption band is most likely due to a metal to ligand charge-transfer transition (MLCT) of a metal-centered 5f electron into a sulfido-based orbital.3 and 4 compared to the pale blue-green color of 2. The visible near-IR electronic absorption spectra of complexes 2\u20134 in pyridine (5 mM) are shown in iv) complexes possess a 5f2 electron configuration, and therefore display rather complicated electronic absorption spectra with multiple low-intensity absorption bands and fine structure in the vis/NIR region.\u03b5 = 6\u2013116 M\u20131 cm\u20131) give rise to signature absorption bands characteristic of tetravalent uranium complexes. This is particularly true for a series of complexes, in which the symmetry around the metal center remains constant and the core structure is dominated by the ((ArO)3tacn)3\u2013 chelate, and thus, quite similar.3 and 4 exhibit 10 absorption bands with nearly identical absorption patterns in the vis/NIR region between 540 and 2100 nm, with three relatively strong absorption peaks at around 990, 1111, and 1990 nm. Noticeably, the molar extinction coefficients observed in the spectra of the separate ion pair 4 are consistently larger than those of complex 3, with the capped terminal sulfido ligand. The NIR spectra have been reproduced multiple times and the differences in extinction coefficient are significantly larger than the experimental error. Further inspection of the NIR spectra reveals approximately equal line width for the absorption bands in complexes 3 and 4; thus, excluding an intensity stealing mechanism.3: FWHM994 nm = 26 nm, FWHM1111 nm = 40 nm, FWHM1998 nm = 106 nm; complex 4: FWHM991 nm = 24 nm, FWHM1111 nm = 38 nm, FWHM1990 nm = 76 nm.\u2021Complex A reduced symmetry also cannot account for different extinction coefficients in 3 and 4, since both possess C3 symmetry in solution (as established by (VT) 1H NMR spectroscopy, vide supra). However, it is worth noting that the timescale of electronic absorption spectroscopy is significantly shorter compared to proton NMR spectroscopy, therefore complex 3 could lose its C3 symmetry. Regardless, in the latter case, absorption bands of complex 3 should be more intense than those of complex 4. Since the intensity of an electronic absorption band in the NIR region is considered indicative of the degree of covalency of the uranium ligand multiple bond in a conserved ligand field,iv) sulfido complex, 3. This is in contrast to the shorter U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS bond observed in the solid-state structure of 3 implying a stronger, more covalent bond compared to 4. Therefore, one can only conclude\u2014and reiterate\u2014that the mere bond distance is not a valid measure of covalency.The electronic structure of complexes Fig. S14. This spgion \u03bb < 0 nm broa2 shows about the same number of absorption bands as 3 and 4, but the f\u2013f transitions occur at slightly different energies and a charge-transfer transition is not observed. Additionally, the intensities of the bands are significantly lower (\u03b5 = 6\u201348 M\u20131 cm\u20131) and, in accordance with the lack of charge-transfer transitions, indicate the presence of a ligand with predominantly \u03c3-donor character.Hydrosulfido complex 1 and tetravalent 2\u20134 from 2 to 300 K (\u03bcS) and total angular momentum approximations (\u03bcJ), respectively, there is currently no approximation to predict the magnetic moment for actinide coordination complexes, since ligand-field effects cannot be ignored and spin\u2013orbit coupling is large.2 valence electron configuration, which results in a non-magnetic ground state at very low temperatures; and consequently, strongly temperature-dependent magnetic moments, \u03bceff, with values typically ranging from 0.3 \u03bcB at 2 K to 2.8 \u03bcB at room temperature.SQUID magnetization measurements were carried out to study the temperature behavior of trivalent to 300 K bottom. III ions (f3) possess a half integer spin with a doublet, EPR-active ground state , but the low temperature effective magnetic moment together with an EPR signal confirms a trivalent uranium ion in complex 1 andomplex 1 top.2\u20134 possess nearly the same magnetic moment with 2.85 \u03bcB, 2.90 \u03bcB, and 2.87 \u03bcB, respectively, but show significantly different temperature-dependent behavior. These results support the notion that the room temperature magnetic moments cannot be used to determine the oxidation state of the uranium ion, since trivalent 1 at room temperature shows nearly the same (or even slightly lower) magnetic moment as tetravalent 2\u20134. At 2 K, however, uranium(iv) complexes with the f2 ion typically show distinctively lower magnetic moments, which are due to the ions' non-magnetic singlet ground state.2 exhibits temperature-dependency overall typical for a uranium(iv) compound. The low magnetic moment, \u03bceff, of 1.03 \u03bcB at 2 K continually increases with increasing temperature. On the contrary, sulfido complexes 3 and 4 reveal an unusually strong temperature-dependency in the range of 2 to 50 K, with a subsequent moderate increase from 50 to 300 K. Notably, complex 3 shows a typically low magnetic moment of 0.84 \u03bcB at 2 K, whereas complex 4 possesses an unusually high \u03bceff value of 1.84 \u03bcB. Despite this high magnetic moment, complex 4 is EPR silent . Similar high magnetic moments have been observed for UIV complexes with separate ion pairs like [Cp*2Co]-[U(O)(N(SiMe3)2)3],5H10)5],4]-[U(CH2tBu)5], and [Li(DME)3]-[U(CH2SiMe3)5].67At room temperature, complexes 2 possesses a more isolated magnetic ground state, where the higher magnetic states slowly become thermally accessible with increasing temperature. Hence, the low-lying magnetic states of complexes 3 and 4 appear to be closer in energy, and are already thermally accessible at temperatures below 50 K. Consequently, the magnetic moment increases rapidly from 2 to 50 K, and merely increases with increasing temperatures above 50 K. The intriguing difference in the temperature dependency of the magnetic moments of complexes 2\u20134 is due to the different crystal-field-splitting caused by the purely \u03c3-type SH\u2013versus the \u03c3- and \u03c0-type S2\u2013 ligands.67On the other hand, complex 3 in THF in the presence of \u223c0.1 M [N(n-Bu)4][BPh4] electrolyte and the ferrocenium/ferrocene redox couple (Fc+/Fc) acting as internal standard. The cyclic voltammogram of 3 reveals a quasi-reversible redox process at a half-step potential, E1/2, of \u20131.494 V (iv/v) redox couple, with the half-step potential in the range of other published UIV/V couples (\u20131.81 to 0.12 V vs. Fc+/Fc).nP,MeArO)3tacn)U}2(\u03bc-O)2] (nP = neopentyl) shows a comparable UIV/V couple at a half-step potential of \u20131.55 V (vs. Fc+/Fc).50Cyclic and linear sweep voltammetry were performed on \u20131.494 V . A posit\u20131.494 V . Accordi2 and 4 in polar solvents, such as THF, cyclic voltammetry experiments could not be performed with these complexes. Given the lack of characterized terminal uranium(v) sulfido complexes in the literature, and the expectation that the covalency of the uranium\u2013chalcogenide bond increases with increasing valence,3 is desirable. Unfortunately, all attempts to chemically oxidize 3 and 4 have not yet been met with success and resulted in decomposition of the compounds.Due to the poor solubility of 2\u20134. Geometry optimizations were conducted on [3tacn)U\u2013SH] (2), (3), and [K(2.2.2-crypt)] (4) at the DFT level without any symmetry constraints. Subsequently, molecular orbital (MO) and natural bond orbital (NBO) analyses were performed.In order to gain further insight into the nature of the U\u2013S bond, theoretical investigations were carried out on complexes 2. The NBO analysis of 2 clearly indicates a single bond between U and S and a single bond between S and H (Wiberg bond indices (WBI) of 0.77 and 0.92, respectively). Accordingly, the molecular orbitals are consistent with a single U\u2013S bond (iv) hydrochalcogenido complex, namely [((tBuO)3SiO)4U(SH)]\u2013 obtained by Andrez et al., exhibits significant double bond character of the uranium sulfur interaction (determined by MO and WBI).2 and [((tBuO)3SiO)4U(SH)]\u2013, these two complexes were analyzed in more detail.Initially, bond analysis was carried out on the hydrosulfido species U\u2013S bond , reveali2 is strongly polarized with 10% uranium and 90% sulfur orbital character. The metal orbital is a hybrid sdf orbital with 12% 7s, 38% 6d, and 50% 5f contribution. This is comparable to the hybrid orbital composition of the hydrosulfido complex [((tBuO)3SiO)4U(SH)]\u2013 exhibiting a \u03c3 (and \u03c0) orbital with 14% uranium character (12% for the \u03c0) and a strongly hybridized orbital . As evidenced by the X-ray structure, the geometry of 2 differs significantly from the trigonal bipyramidal complex [((tBuO)3SiO)4U(SH)]\u2013. The computational analysis suggests that the pyramidalized uranium ion of 2 has an efficient overlap with the N donor atoms of the tacn ring. This, in turn, results in a trans-effect reducing the U\u2013SH bond strength, which is rather unusual for uranium complexes. In order to emphasize the importance of the trans-influence of the tacn ligand, a hypothetical tris(aryloxide) complex, 2* (without the triazacyclononane ligand) was also computed. Interestingly, this model complex adopts a tetrahedral geometry at the uranium center, and a U\u2013S double bond character is found (see ESIThe U\u2013S \u03c3-bond of complex iv) complex 3 clearly reveals a formal U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS triple bond with one \u03c3 and two \u03c0-type interactions (3 (and 4) illustrates that the uranium ion is situated almost perfectly in the trigonal plane of the three aryloxides with a weaker U\u2013Ntacn interaction and more efficient uranium\u2013sulfur orbital interaction resulting in the observed U\u2013S multiple bond. NBO analysis shows that the U\u2013S bond is strongly polarized with more than 75% charge on the sulfur. A \u03c3-bond is formed by an sp orbital of sulfur (77%) and a dz2/fz3 hybrid orbital of uranium (23%), and two \u03c0 orbitals are formed by the interaction of a p lone pair of sulfur and a hybrid d\u03c0/f\u03c0 orbital of uranium (23%). This formal uranium sulfur triple bond is virtually unaffected by the minor interaction of the sulfido ligand with the potassium counterion (WBI of 0.1). To further substantiate the effect of the weakly associated K+ ion in 3, the bonding analysis of 4 with an encrypted and well-isolated potassium ion was carried out. As expected, a triple bond between uranium and the sulfido ligand was found with the orbitals closely resembling those of 3 . The experimentally determined U\u2013S bond length of 4 (without the S\u00b7\u00b7\u00b7K interaction) is elongated compared to 3. However, this result is not reproduced by the calculations that show the bond in 3 to be slightly longer (0.02 \u00c5) than in 4 in 3 leads to a stronger negative charge on the sulfido ligand (\u20130.1 unit difference), which is formally interacting with two positively charged ions. Since the charge at the uranium ion is the same for 3 and 4, the coordination of the potassium ion leads to a higher negative charge on the sulfido ligand in 3, counterbalancing the charge. Consequently, a higher charge on the sulfido ligand in complex 3 leads to a smaller orbital overlap, and therefore less covalent interaction. In order to determine the nature of this discrepancy between experiment and theory, calculations were carried out on the putative anionic complex [3tacn)U(S)]\u2013 (4\u2013). The bonding analysis confirmed the negligible influence of the K+ ion on the electronic structure of the U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS bond of 3 and 4, but not on the U\u2013S bond length . Complex 4\u2013 possesses the shortest U\u2013S distance, in line with the influence of the K+ bonding, but contrary to the bond lengths observed in the solid state . Perrin et al. reported a similar effect for the distorted geometry of an amido lanthanide complex.71In the calculation, a weak S\u00b7\u00b7\u00b7K interaction scale\" fill=\"currentColor\" stroke=\"none\">S bond is obtained, which is strongly polarized towards S (between 70 and 75%) with hybrid s/d orbital involvement of the metal (roughly 80% 6d). Interestingly, the nature of the U PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS bond of complexes 3 and 4 appears to be quite similar to other computed uranium(iv) chalcogenido complexes with different supporting ligand systems. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS entity, regardless of whether aryl-oxide, siloxide, or supporting amide ligands are applied. In all reported complexes, the geometries at the uranium center are either distorted tetrahedral or trigonal pyramidal. Quite surprisingly, the atomic 5f and 6d orbitals experience a very similar ligand field effect in all complexes.Based on all of these results, we assign a significant degree of covalency to the U\u2013S bond of complexes 3 and 4\u2013 were carried out. Based on the report by Andersen on a Cp*2UO compound, a more ionic bonding description can be expected for the oxo complex.\u20131, in line with a strong agostic interaction, see Table S4 ESIIn order to investigate the possible influence of the chalcogenido ligand, the bonding analyses of the oxo-homologs of 2\u20134, supported by the 3tacn3\u2013 ligand system. Proton NMR spectroscopy reveals C3 symmetry of the complexes in solution, and the vis/NIR electronic absorption spectroscopy, together with the SQUID magnetization measurements, allow for the unambiguous assignment of the uranium ion to the +IV oxidation state. The differences in temperature-dependency of complexes 3 and 4 at low temperatures (T < 50 K) also suggest a significant influence of the potassium counter ion on the crystal field splitting of the terminal sulfido complexes as well as the nature of the U\u2013S bond. DFT computational analyses further provided detailed insight into the bonding properties of complexes 2\u20134, and reveal a non-negligible degree of covalency in the uranium\u2013sulfur bond of 3 and 4. This is supported by the complexes\u2019 structural parameters, vis/NIR electronic absorption spectroscopy, and SQUID magnetometry. The electrochemical studies show that complex 3 can be electrochemically oxidized, most likely to a UV PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tS species, which is expected to exhibit an even greater degree of covalency of the uranium sulfur bond.v) sulfido complex led to decomposition products.In summary, we here present a new and high-yield synthetic protocol and the characterization of the terminal uranium hydrosulfido and sulfido complexes iv) complexes with terminal hydrochalcogenido and chalcogenido ligands is part of our on-going studies.The synthesis of a complete series of uranium(Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The electronic effects induced by the synergy of stable C12A7:e\u2013 electride and bimetallic Ru\u2013Fe nanoparticles efficiently control the chemoselective reduction reaction. 24Al28O64]4+\u00b7(e\u2013)4, with extremely low work function, promotes the superior activity and selectivity of a Ru\u2013Fe nano-alloy for the conversion of \u03b1,\u03b2-unsaturated aldehydes to unsaturated alcohols in a solvent-free system. The catalyst is easily separable from the product solution and reusable without notable deactivation. Mechanistic studies demonstrate that electron injection from the electride to the Ru\u2013Fe bimetallic nanoparticles promotes H2 dissociation on the highly charged active metal and preferential adsorption of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds over C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCs bond of the unsaturated aldehydes, to obtain the thermodynamically unfavorable but industrially important product.Controlling the electronic structure of heterogeneous metal catalysts is considered an efficient method to optimize catalytic activity. Here, we introduce a new electronic effect induced by the synergy of a stable electride and bimetallic nanoparticles for a chemoselective reduction reaction. The electride [Ca Numerous efforts have been devoted to achieving a high yield of required chemicals without any byproduct using a heterogeneous catalyst.24Al28O64]4+\u00b7(e\u2013)4 (C12A7:e\u2013) is an inorganic electride with anionic electrons in the positively charged framework ([Ca24Al28O64]4+) that was created in 2003.\u2013 electride is its low work function (2.4 eV), comparable to that of alkali metals, but with higher chemical inertness, which makes this material a promising electron donor in chemical reactions.\u2013 alone, or in combination with Ru, functions as an effective catalyst in chemical reactions, such as ammonia synthesis and decomposition, and CO2 splitting.\u2013 as a catalyst for liquid phase reactions because they are chemically unstable in aqueous media and tend to release electrons into the solvent or moist environment. The C12A7:e\u2013 electride has recently been used as an electron generator in aqueous solution to facilitate the pinacol coupling reaction of aldehydes, and the chemoselective reduction and oxidation of ketones.Electrides are ionic crystals with cavity-trapped electrons that act as anions. Ca24Al28O44+\u00b7(e\u2013)4e\u2013)4 C12A:e\u2013 is an PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond over the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond is both thermodynamically and kinetically favored.e.g., the adsorption of a polar reactant is enhanced by a non-polar solvent, and vice versa.16Chemoselective hydrogenation of \u03b1,\u03b2-unsaturated aldehydes to the corresponding unsaturated alcohols is difficult but fundamentally important in both chemical research and industry.1.000000,.000000 s\u2013 electride-supported Ru\u2013Fe alloy nanoparticles (Ru\u2013Fe/C12A7:e\u2013) can act as a highly efficient and selective heterogeneous catalyst for the liquid phase chemoselective hydrogenation of \u03b1,\u03b2-unsaturated aldehydes under solvent-free conditions. After reaction completion, the solid Ru\u2013Fe/C12A7:e\u2013 can be easily separated from the reaction mixture and reused without decrease in catalytic efficiency. Detailed characterization indicates that the electronic effect induced by the electron donation of the C12A7:e\u2013 electride support and the charge transfer between nano-alloy particles is responsible for the superior catalytic performance for chemoselective hydrogenation. To the best of our knowledge, this is the first report on an electride-based heterogeneous catalyst in a liquid catalytic reaction with a solvent-free system.In this work we demonstrate that C12A7:e\u2013 catalysts were fabricated initially by conventional solid-phase reaction and subsequent chemical vapor deposition (CVD) of metal carbonyl complexes in a vacuum patterns .\u2013. X-ray photoelectron spectroscopy and Ru/C12A7:e\u2013 exhibited poor activity and selectivity for cinnamyl alcohol of C12A7:e\u2013 as a support . As expected, all substrates were quantitatively reduced to their corresponding alcohols under optimized catalytic conditions. The reaction was sensitive to steric hindrance of the substituents on the alpha sites, and as a result trans-2-methyl-2-pentenal and trans-2-methyl-2-butenal exhibited relatively low conversion under relatively rigorous conditions , but still with high selectivity. In contrast, the activity of the \u03b1,\u03b2-unsaturated ketone hydrogenation reaction was quite poor due to steric hindrance from the methyl group in the carbonyl component high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). \u2013 electride, which is consistent with scanning electron microscopy (SEM) analysis , which is consistent with the results of XRD measurement to understand the interaction between Ru and Fe in the alloy. As shown in ca. 140 \u00b0C, which is assigned to the reduction of RuO2.x species.2 into C12A7:e\u2013 cages as H\u2013 ions during the high temperature stage.8The reducibility of the catalysts was investigated at various metal weight ratios using hydrogen temperature-programmed reduction (H\u2013 electride was examined by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy using CO as a probe molecule. As shown in 2\u2013 exhibits main peaks at around 2100\u20132000 cm\u20131, which can be assigned to the C\u2013O stretching vibration of linearly adsorbed CO on Ru0 sites, indicating that there is no electron transfer from C12A7:O2\u2013 to the Ru metal nanoparticles. This is due to the fact that C12A7:O2\u2013 is a typical insulator material, in which O2\u2013 ions are incorporated as counter anions to the positively charged [Ca24Al28O64]4+ lattice framework composed of subnanometer-sized cages.\u20131 corresponds to tricarbonyl species on partially oxidized Ru sites.2\u2013 has no adsorption peaks, which indicates that the interaction between CO molecules and Fe is quite weak after Fe addition. The red-shift of the CO signal is clear evidence of the electronic interaction between Ru and Fe species. Electropositive Fe metal generally acts as an electron-donating ligand that increases the electron density of Ru, thereby favoring the back-donation of electrons to the 2\u03c0* antibonding orbitals of CO, which accounts for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond weakening (red-shift of the CO stretching band). In contrast, the electron density of Fe atoms decreases due to the electron transfer from Fe to Ru. A similar electron transfer effect is demonstrated on a model surface of Pt80Fe20(111) by H\u00fcckel calculations. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond weakening on both Ru/C12A7:e\u2013 and Ru\u2013Fe/C12A7:e\u2013. Compared to Ru/C12A7:O2\u2013 and Ru\u2013Fe/C12A7:O2\u2013, a clear red-shift is observed for the linear Ru0\u2013CO peak (2030 cm\u20131) of Ru/C12A7:e\u2013 and for that (2020 cm\u20131) of Ru\u2013Fe/C12A7:e\u2013, respectively scale\" fill=\"currentColor\" stroke=\"none\">O bond of a CO molecule adsorbed on Ru/C12A7:e\u2013 and Ru\u2013Fe/C12A7:e\u2013 is weakened by the electrons encaged in C12A7:e\u2013, which has an extremely low work function and metallic conductivity.\u2013 electride.The electron donation capabilities of Ru\u2013Fe nanoparticles on the C12A7:eharged CaAl28O644+ Fig. S10. Notablyectively , which i\u2013 is shown in PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds can interact with the metal surface and the adsorption mode is strongly dependent on the surface of the metal catalyst. In our case, the electronic nature of the metal nanoparticles can be modified by the electron donation from C12A7:e\u2013, leading to the marked increase in the hydrogenation selectivity. The electron enrichment of the metal surface decreases the binding energy of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond via increased repulsive interaction between metal d-orbitals and the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond, favoring a vertical adsorption configuration via the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond scale\" fill=\"currentColor\" stroke=\"none\">O bond. Additionally, electropositive Fe sites are formed in the Ru\u2013Fe bimetallic system as demonstrated in FT-IR analysis scale\" fill=\"currentColor\" stroke=\"none\">O bond via the lone electron pair of the oxygen atom, which leads to a weakening of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds is thus enhanced compared with the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bonds. There are two possible routes to cleave H2. H2 dissociation occurs preferentially on the Ru surface due to the low dissociation barrier of H2 on Ru, which results in the formation of nonpolar hydrogen species via homolytic cleavage of H2 scale\" fill=\"currentColor\" stroke=\"none\">C and C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bonds, with the hydrogenation of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond being thermodynamically favorable. However, the hydrogenation of C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond selectively occurs over Ru\u2013Fe/C12A7:e\u2013 because the unsaturated aldehyde molecules are adsorbed on the catalyst surface via the vertical configuration.The proposed reaction mechanism for the chemoselective hydrogenation of \u03b1,\u03b2-unsaturated aldehydes over Ru\u2013Fe/C12A7:eO bond .28 This O bond . Zero oranalysis . The Fe ge of H2 , Route 12 dissociation (H2 \u2192 H\u2013 + H+) at the interface between a metal and basic support, which would subsequently enhance selective hydrogenation reactions.4 and LiAlH4via nucleophilic attack by H\u2013 species to the positively charged carbon of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond.\u2013, it can be expected that H\u2013 species are formed on electron-rich metal sites and H+ is simultaneously formed on a framework oxygen at the surface of C12A7:e\u2013. The resulting H\u2013 and H+ species react with the carbon and oxygen sites of C\u03b4+ PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO\u03b4\u2013 bonds, respectively scale\" fill=\"currentColor\" stroke=\"none\">C bonds. Although the detailed mechanism remains to be clarified at this stage, it is important to emphasize that electron transfer between electride and metal nanoparticles could be the key factor in the chemoselective reduction of unsaturated aldehydes.Another possibility is heterolytic Hectively , Route 2\u2013 electride were constructed to achieve highly efficient solvent-free hydrogenation of \u03b1,\u03b2-unsaturated aldehydes. The intrinsically low work function C12A7:e\u2013 injects electrons into the active Ru\u2013Fe nanoparticles, which leads to the formation of the unsaturated alcohol with outstanding catalytic activity and high selectivity, without the need for basic additives in the reaction solution. The synergistic effect of the alloy metal Ru and Fe offers atom-scale electron transfer to activate Ru and induces electrophilic activation towards C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, both favoring chemoselective hydrogenation. The electride-based catalyst also exhibited excellent sustainability and superior chemoselectivity of over 95% during long-term cycling. These results could serve as inspiration for the further exploitation of electride-based metal or alloy catalyst interactions in the design and synthesis of novel heterogeneous catalysts. We consider that a family of electrides with high electron donation ability could find wide application in different fields of catalysis.In summary, Ru\u2013Fe alloy nanoparticles deposited on C12A7:eSupplementary informationClick here for additional data file."}
+{"text": "The synthesis and catalytic reactivity of a class of water-tolerant cationic phosphorus-based Lewis acids is reported. v) cations of the type [ArP(cor)][B(C6F5)4] 2C6H3; cor = 5,10,15-(C6H5)3corrolato3\u2013, 5,10,15-(C6F5)3corrolato3\u2013) were synthesized and characterized by NMR and X-ray diffraction. The visible electronic absorption spectra of these cationic phosphacorroles depend strongly on the coordination environment at phosphorus, and their Lewis acidities are quantified by spectrophotometric titrations. DFT analyses establish that the character of the P-acceptor orbital comprises P\u2013N antibonding interactions in the basal plane of the phosphacorrole. Consequently, the cationic phosphacorroles display unprecedented stability to water and alcohols while remaining highly active and robust Lewis acid catalysts for carbonyl hydrosilylation, C3sp\u2013H bond functionalization, and carbohydrate deoxygenation reactions.The synthesis and catalytic reactivity of a class of water-tolerant cationic phosphorus-based Lewis acids is reported. Corrole-based phosphorus( A nontrigonal substitution at phosphorus. Specifically, we envisioned that a tetragonal substituent field would be less conducive to formation of a formal P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO multiple bond, diminishing the propensity for phosphine oxide formation and thereby preserving the Lewis acidity at the cationic phosphorus center (v) corroles readily undergo apical halide/alkoxide exchange11We considered that an alternate approach to robust phosphorus-based Lewis acids might be accessible by deliberate alteration of the molecular geometry. Having previously demonstrated that molecular deformation of neutral phosphorus compounds allows for novel bond activation reactions and catalytic transformations,s center , bottom.v) cations are robust, tunable, and catalytically-active Lewis acids. We find that the rigid tetragonal geometry imparts stability to water and alcohols while maintaining Lewis acidity, enabling these compounds to effect transformations which were previously inaccessible to phosphonium catalysts. This desirable superposition of properties is rationalized within an electronic structure argument that advances our ongoing program to establish new reactivity for p-block elements by imposition of underexplored molecular geometries.We demonstrate here that square pyramidal corrole-based phosphorus(4) in the presence of triethylamine furnished an unstable intermediate, which upon the addition of [Bu4N][BH(OAc)3] yielded hexacoordinate 1\u00b7H as a chromatographically stable green solid (31P{1H} NMR spectrum of 1\u00b7H showed a resonance at high field (\u03b4 \u2013 231.3 ppm), consistent with compositionally similar hexacoordinate phosphorus compounds reported previously.31P NMR resonance evolves into a doublet of triplets, with coupling constants evidencing a direct P\u2013H bond (1JP\u2013H = 928.0 Hz) as well as longer range coupling to the ortho protons of the apical P-aryl moiety (3JP\u2013H = 25.1 Hz).1H NMR channel, the P\u2013H unit was observed with complementary coupling ; the rather high-field chemical shift of this 1H nucleus is attributed to shielding from the diamagnetic ring current of the corrole system,1\u00b7H as in Synthesis of the target cations was achieved in two steps from the freebase corrole. First, treatment of 5,10,15-triphenylcorrole with 1 equiv. of phenyl tetrachlorophosphorane 4] immediately produced a red solution, from which a new phosphorus-containing product was obtained by precipitation via slow addition of pentane. A 31P NMR spectrum of the resulting maroon solid displayed a single new triplet resonance downfield of the starting compound . This chemical shift is indicative of a pentacoordinate phosphorus center shielded by diamagnetic ring current;1JP\u2013H coupling and concomitant formation of triphenylmethane further evidence the formation of the hydride abstraction product +1. Related phosphacorroles +\u20134+2 were synthesized analogously from the corresponding triarylcorrole and aryl phosphorane as depicted in The apical hydride of hexacoordinate compound +1 was revealed by X-ray diffraction experiments (\u03c4 = 0.09),+4 (\u03c4 = 0.05)P center protrudes less from the binding pocket relative to +1 (\u0394d = 0.023 \u00c5). In both instances, the overall geometry imposed by the corrole ligand may be viewed as a monovacant octahedron about phosphorus. In conjunction with structural data for known hexacoordinate phosphorus corrole compounds ,4+ similarl+\u20134+1 for Lewis bases was initially assayed by recording 31P NMR chemical shift differences (\u0394\u03b4) for a phosphine oxide ((n-octyl)3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) probe upon binding according to a modification of the Gutmann\u2013Beckett method.\u03b4 values (+1 < +2 < +3 < +4) as a function of increasing modular fluorination. A direct comparison of the Lewis acidity of +\u20134+1 to other Lewis acids on the basis of these \u0394\u03b4 values is tempting, but we caution against such a potentially specious interpretation in the present circumstance. In view of the diamagnetic ring current of the corrole moiety,\u03b4 values. Other NMR-based methods for the determination of Lewis acidity . The marked difference in color between cationic five-coordinate phosphacorroles (red) and neutral six-coordinate congeners (green) provided a convenient colorimetric method for measuring equilibrium binding in +\u20134+1. The sensitivity of the color dependence to the concentration of an exogenous Lewis base was demonstrated by titrating cationic phosphacorrole +4 with varying amounts of (n-octyl)3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (e.g. \u03bb = 566 nm) confirms adduct formation free of decomposition or other deleterious reactivity.A unbiased quantification of Lewis acidity for /svg>O , top. Thn-octyl)3P PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO were fitted to the Hill equationKd //B3LYP/def2-TZVP leveliii) corroles,+\u20134+1 correspond to the corrole \u03c0 manifold, and are apparently not responsible for the experimentally observed Lewis acidity of cationic phosphacorroles.To further understand the varying Lewis acidities of +4, e.g. \u20132.31 eV for +4, see +\u20134+1 correlate with the experimental dissociation constants Kd for phosphine oxide binding, implying that Lewis acid/base interactions are hosted by this orbital cleanly gives P-hydroxide 3\u00b7OH (\u03b4 \u2013 200.2 ppm) in quantitative fashion as in +3 but instead gives an adduct that we formulate as +\u00b7OH23 via 1,5-hydride shift from a N,N-dialkylaniline donor to a malonate alkylidene acceptor followed by intramolecular cyclization to give 6 in good isolated yield (13C6-d-glucose (7) is exhaustively deoxygenated by a catalytic amount of +4 (5 mol%) in the presence of an excess of H2SiEt2 at room temperature to give a mixture of hexanes and hexenes (67% total yield, +4 is not degraded; instead, an approximately equimolar amount of 4\u00b7H and +4 were observed spectroscopically as the only 31P NMR resonances. The lack of reaction between +4 and H2SiEt2 in a control experiment further indicated that +4 is a true catalyst for this reaction. The persistence of +4 with respect to a substrate that under these conditions presents a 100\u2009:\u20091 ratio of free hydroxyl moieties to catalyst confirms the noteworthy chemical robustness inherent to tetragonal cationic phosphorus-based Lewis acids.The phosphacorrole cations ed yield .31 Furth+\u20134+1 as enforced by the tetraazamacrocycle, which produces an acceptor orbital that is distinct in character from prior trigonal electrophilic phosphonium cations and prohibits irreversible decomposition to phosphine oxides. The modularity of the corrole supporting framework allows the Lewis acidities of these electrophilic phosphorus species to be readily tuned. Together, these results establish within the family of designer main group Lewis acids a new structural type that extends the range of potential applications for this valuable class of compounds.In summary, we have shown that cationic phosphacorroles are potent Lewis acids that exhibit marked tolerance toward hydroxylic functionality including water. We propose that this useful property arises from the tetragonal geometry of There are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "Post synthetic linker exchange can be combined with Cu-catalyzed alkyne/azide click chemistry to enable orthogonal modification of known metal organic frameworks. via post synthetic linker exchange. Sequential and orthogonal click reactions could be performed on these modified MOFs by incubating the crystals with small molecule substrates bearing azide or acetylene groups in the presence of a copper catalyst. 1H NMR of digested MOF samples showed that up to 50% of the incorporated linkers could be converted to their \u201cclicked\u201d triazole products. Powder X-ray diffraction confirmed that the UiO-67 structure was maintained throughout all transformations. The click reaction efficiency is discussed in context of MOF crystallite size and pore size. As the incorporation of clicked linkers could be controlled by post synthetic exchange, this work introduces a powerful method of quickly introducing orthogonal modifications into known MOF architectures.Biphenyl-4,4\u2032-dicarboxylic acid derivatives containing either azide or acetylene functional groups were inserted into UiO-67 metal organic frameworks (MOFs) Metal organic frameworks (MOFs) have moved beyond \u2018simple\u2019 homogeneous materials into complex multiple-domain structures.orthogonal MOF modification. Orthogonal linker modification via a selective and stepwise tuning of specific subsets of linkers within a MOF would rapidly permit the construction of multi-functional MOFs. The vast majority of post synthetic MOF modifications methods do not discriminate within the target. For example, post synthetic metal ion exchangeOne desirable route for rapidly adding functionality is by coupling known MOF syntheses with unrelated yet well-established synthetic paradigms. We envisioned that post synthetic exchangeOrthogonal click chemistry is generally not possible through routine solution chemistry. If a mixture of substrates containing either acetylene or azide groups is exposed to catalytic conditions and a click reaction partner, the expected result is a statistical mixture of product and substrate cross-coupling. We expect that if two different click substrates are immobilized within the same MOF framework this unproductive cross-reaction can be avoided and so allow selective stepwise click reactions on the same material.i)-catalyzed azide\u2013alkyne cycloaddition (CuAAC) click chemistry within a MOF has been shown using a MOF built entirely of linkers bearing azide and acetylene functional groups. After synthesis, this UiO-68 (UiO = University of Oslo) type MOF could undergo sequential click reactions within the solid crystals in quantitative yield.Very recently orthogonal copper control over the final fraction of modified \u2013 and so clicked \u2013 linkers, (2) permitting the use of known MOFs, and (3) providing a way to introduce reactive sites that would not survive the initial MOF solvothermal synthesis. The last point is especially important, as it has been shown that the azide-functionalized linker we used here does not survive typical UiO-67 solvothermal conditions.26UiO-67 was chosen for this study due to its good bulk structural stability, relatively large pore size, and proven ability to engage in post synthetic linker exchange reactions.2O were prepared. To these were added -4,4\u2032-dicarboxylic acid functionalized with either an azide or acetylene group scale\" fill=\"currentColor\" stroke=\"none\">C respectively, as shown in 6-DMSO with aqueous HF for 1H NMR quantification scale\" fill=\"currentColor\" stroke=\"none\">C. Increasing the temperature to 40 \u00b0C did not appreciably change the incorporation yield for the azide linker. No thermocyclization of the azide linker, as seen for solvothermal synthesis of UiO-67 containing L-N3,3 and L-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC were 33% and 26%, respectively. These exchange yields track with the lower incorporation of L-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC observed in the single substitution experiment. 1H NMR of UiO-67 digested after simultaneous post synthetic exchange with both L-N3 and L-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC.Crucially, both linkers could be introduced into the same UiO-67 material through this post synthetic exchange strategy . With 13ca. 10% modified linkers with either L-N3 or L-C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC. UiO-67 containing ca. 10% of modified linkers were used in subsequent click reaction experiments.As a MOF containing large numbers of modified linkers may result in excessive steric crowding during subsequent click reactions, we sought to generate UiO-67 with fewer substituted linkers. Indeed, a straightforward decrease in the net equivalents of both linkers present during exchange yielded UiO-67 with 3CN)4]PF6 and the fluorine-labeled substrates 1-ethynyl-4-(trifluoromethyl)benzene and 4-azido-1,1,1-trifluorobutane. 19F NMR was used to confirm that the MOF material after the click reactions contained the corresponding triazole products 4]PF6 in 1.5 ml THF and degassed for 5 minutes prior to the addition of the fluorinated click partners .Click reactions were performed under inert atmosphere at 50 \u00b0C in freshly distilled THF for 24 hours. In general, 20 mg of functionalized UiO-67 was mixed with 0.5 molar equivalent of PF6 catalyst, and 2 equivalents of click partners; in Zhang's work the reaction was carried out at 60 \u00b0C in DMF with CuI catalyst for 24 hours and unknown click partner stoichiometry.The difference in click conversion yields between this work and that of Zhang d4-1,4-dicarboxylic acid (H2BDC-d4) into ca. 100 \u03bcm crystals of UiO-66 was examined and a pronounced core\u2013shell structure was found, with exchange only occurring in the outer layers.33Individual crystallite size also matters: smaller crystals should facilitate access to interior click reaction sites. To our knowledge, there is no rigorous study available comparing post synthetic exchange into different sized crystals. However, one comparison can be made between two papers that both used UiO-66. In one study, the incorporation of benzene-2,3,5,6-ca. 1\u20133 \u03bcm across (via SEM, see Fig. S13\u2013S20The difference in crystallite size for this study and Zhang's UiO-68 work is not so pronounced. Here, crystals were Given these differences, a quantitative comparison is not straightforward; however, we suspect that the larger pore sizes of UiO-68 were the primary factor contributing to the reported quantitative click yields. Future studies comparing identical click reaction conditions using UiO-67 and UiO-68 crystals of similar size could address this question.known MOF materials are of special interest.MOFs have the potential to revolutionize industrial material science; as such, interest in new methods of functionalizing MOFs remains high. As there are thousands of MOF architectures to choose from, methods to easily modify Via the combination of these two methods, this work demonstrates a new approach to orthogonally modify MOFs. First, post synthetic exchange reactions showed that the native linkers in UiO-67 could be replaced with linkers bearing azide or acetylene groups. Stepwise incubation with a copper catalyst and small molecule click partners allowed the formation of two different triazole click products in a selective and orthogonal manner.Post synthetic exchange is firmly established as a reliable method of tuning known MOFs,via1H NMR revealed that up to 50% of the modified linkers could be converted to their clicked partners. PXRD analysis confirmed that the parent UiO-67 structure was maintained throughout all transformations.Control reactions established unambiguously that no click reactions occur if either the click partner or Cu catalyst is omitted. Quantification of click reaction yields Given the versatility of post synthetic exchange and power of click chemistry, we expect that this method of modifying MOFs in a stepwise and orthogonal fashion will be broadly useful. The ability to selectively change two different subsets of linkers within a MOF opens new avenues for rapid construction of complex functionality. From a fundamental perspective, the ability to selectively perform click chemistry on only one substrate while both azide and acetylene substrates are present is not normally possible in solution chemistry \u2013 it is through immobilization within a MOF framework that selective and non-statistical products can be obtained. Interesting questions remain regarding optimization of the click reaction efficiency, especially for MOFs with small pore diameters.UF performed research; UF and SO designed research and analysed data; BDM, UF, and SO wrote the paper.There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "This paper presents a comparison of a graph-based genetic algorithm (GB-GA) and machine learning (ML) results for the optimization of log\u2009P values with a constraint for synthetic accessibility and shows that the GA is as good as or better than the ML approaches for this particular property. P values with a constraint for synthetic accessibility and shows that the GA is as good as or better than the ML approaches for this particular property. The molecules found by the GB-GA bear little resemblance to the molecules used to construct the initial mating pool, indicating that the GB-GA approach can traverse a relatively large distance in chemical space using relatively few (50) generations. The paper also introduces a new non-ML graph-based generative model (GB-GM) that can be parameterized using very small data sets and combined with a Monte Carlo tree search (MCTS) algorithm. The results are comparable to previously published results using a recurrent neural network (RNN) generative model, and the GB-GM-based method is several orders of magnitude faster. The MCTS results seem more dependent on the composition of the training set than the GA approach for this particular property. Our results suggest that the performance of new ML-based generative models should be compared to that of more traditional, and often simpler, approaches such a GA.This paper presents a comparison of a graph-based genetic algorithm (GB-GA) and machine learning (ML) results for the optimization of log\u2009 Within the past few years several papers have been published on using machine learning (ML) to generate molecules with the aim of optimizing their properties.P values with a constraint for synthetic accessibility and show that the GA is as good as or better than the ML approaches for this particular property. I also introduce a new non-ML graph-based generative model that can be parameterized using very small data sets and combined with a Monte Carlo tree search algorithm. The implementation of both methods relies on the open source RDKit cheminformatics package and the codes are made freely available.In this paper I present a comparison of graph-based GA and ML results for the optimization of log\u2009et al.et al.et al.et al.P scores.The graph-based genetic algorithm (GB-GA) combines the ideas from the algorithm developed by Brown et al.et al.X \u223c Y \u2192 X1 \u223c Z \u223c Y1 where \u201c1\u201d indicates that X and Y are bonded and \u201c\u223c\u201d indicates an arbitrary bond order.Tsuda and coworkers PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C, which accounts for 45% of all 3-atom combinations in rings scale\" fill=\"currentColor\" stroke=\"none\">C\u2013C mutation is chosen 45% of the time, and similarly for the 34 other X \u223c Y \u223c Z combinations found in the data set. The site of insertion/creation is chosen randomly and excludes aromatic and six-membered rings. Similarly, for addition the most common bond involving at least one non-ring atom is C\u2013C, so a C \u2192 C\u2013C mutation is chosen more often scale\" fill=\"currentColor\" stroke=\"none\">C vs. C\u2013C, was considered but then the most probable bonding patterns are often not found in the early stages of molecule growth and the growth process effectively stops.In order to create realistic looking molecules, such as those in the ZINC data set, the mutations and choice of element are chosen with probabilities obtained by an analysis of a subset of the molecules in the ZINC dataset. An analysis of first 1000 molecules in the ZINC dataset shows that 63% of the atoms are ring atoms, so the ring-creation or ring-insertion mutation is chosen 63% of the time. The most common 3-atom combination in rings is Cin rings , so a C and rollout is terminated if the molecule exceeds the target size as described for the GB-GA. Any three- or four-membered alkene rings are subsequently expanded to five-membered rings by inserting C atoms. The reward function is 1 if the predicted J(m) value (see below) is larger than the largest value found so far and 0 otherwise. This reward function was found to work slightly better than the one used by Yang et al.2The GB-GM-MCTS code is a modified version of the mcts.py codeet al.et al.J(m):P(m) is the octanol\u2013water partition coefficient for a molecule (m) as predicted by RDKit, SA(m) is a synthetic accessibility score,Following G\u00f3mez-Bombarelli J(m) depends both on the number and types of atoms and can be made arbitrarily large by increasing the molecular size. Therefore it is important to limit the molecular size in order to make a fair comparison to previous studies. Yang et al.et al.J(m) scores for each simulation are averaged. The population size is 20 and 50 generations are used (i.e. 1000 J(m) evaluations per run). The initial mating pool is 20 random molecules sampled from the first 1000 molecules in the ZINC data set. The mean J(m)-score for this set is 0.2 and the maximum value is 3.6.Ten GA simulations are performed and the maximum J(m)-score for the GA is 6.8 \u00b1 0.7 and 7.4 \u00b1 0.9 using a 50% and 1% mutation rate, respectively -score evaluations. The latter took 8 hours each, while the GB-GA calculations took 30 seconds each on a laptop. These J(m)-scores are also significantly larger than those of the other ML-based methods tried by Yang et al.The average maximum ectively . For comJ(m)-scores found by the GB-GA. These scores, 8.8 and 8.5, are slightly larger than the three largest values (7.8\u20138.0) obtained by You et al.J(m) values of 0.9 and \u20132.4 value evolves with each generation for 10 different GB-GA runs. While most of the runs have mostly peaked after about 20 generations the three best performing runs show significant improvements between 30 and 40 generations, so running fewer than 50 generations cannot be recommended for J(m) maximisation. None of the runs increased J(m) significantly after periods of 20 generations with no or little change in J(m) (with the possible exception of run 7). So a good strategy may be to terminate the GB-GA run if the J(m) value has not changed for more than 20 generations (at least for J(m) maximisation). PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C, which is reasonably close to the 45% in the reference set scale\" fill=\"currentColor\" stroke=\"none\">C\u2013\u201d atom will be added. It is thus a little bit more likely that a \u201c\u2013C\u2013\u201d atom will be \u201caccepted\u201d, compared to a \u201c PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013\u201d atom.As described in the Computational methodology section, the GB-GM method grows a molecule one atom at a time where the choice of bond order and atom type is chosen probabilistically based on a bonding analysis of the first 1000 molecules in the ZINC dataset (referred to hereafter as the reference set). The GB-GM model is tested by generating 1000 molecules using ethane as the \u201cseed\u201d molecule (which takes about 30 seconds on a laptop) and repeating the statistical bonding analysis. The average molecular size in the new data set is 23.2 \u00b1 4.1 atoms, which is nearly identical to that of the training set: 23.2 \u00b1 4.4 atoms. There are 2498 rings compared to 2768 in the reference set and 59% of the atoms are in rings, which also is close to the 63% in the reference set. 41% of the 3-atom combinations in rings is Cence set . This di PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t[*]\u2013[*] PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t[*]\u2013[*] PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\t[*]1) as well as cyclopentane ([*]1\u2013[*]\u2013[*]\u2013[*]\u2013[*]1) and cyclohexane ([*]1\u2013[*]\u2013[*]\u2013[*]\u2013[*]\u2013[*]1) type rings, while there are more of most of the other types compared to the reference set. The reason is that the molecules in the ZINC data set are not made by randomly adding atoms, but by assembling larger functional groups such as aliphatic and aromatic rings. As a result the average ring composition does not reflect the most likely ring compositions. It is possible to scale the probabilities to skew the results towards one or the other ring-type. For example in the last column the probabilities are scaled such that the probability of X = Z\u2013Y is 80% rather than the 62% in the reference set, which increases the number of benzene-like rings from 479 to 850 at the expense of the aliphatic rings.Not surprisingly, there are bigger differences for the larger scale features not specifically encoded in the rules such as the type of ring . For exaJ(m)-scores for each simulation are averaged. The tree is traversed 1000 times, i.e. there are 1000 J(m) evaluations per run. For GB-GM-MCTS the average maximum J(m)-score value is 2.6 \u00b1 0.6, which is significantly lower than the lowest value in the study of Yang et al.et al. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC\u2013C containing rings is increased from 62% to 80% then the average maximum J(m)-score increases to 3.4 \u00b1 0.6. Increasing the number of tree traversals to 5000 increases the value to 4.3 \u00b1 0.6, which is similar to the 4.9 \u00b1 0.4 obtained by Yang et al.et al.Ten GB-GM-MCTS simulations are performed using ethane as a seed molecule and the maximum et al.J(m)-scores can be obtained using long aliphatic chains, but this structural motif is relatively rare in the ZINC data set and therefore rarely suggested by the generative models.et al.,P values with a constraint for synthetic accessibility (J(m)) and shows that the GA is as good as or better than the ML-based approaches for this particular property. The GB-GA predicts maximum J(m)-values that, on average, are 1.3\u20131.8 units higher than the best ML-based results reported by Yang et al.,J(m)-scores that, depending on the method, often are several units larger than those found with ML-based approaches. These molecules bear little resemblance to the molecules used to construct the initial mating pool, indicating that the GB-GA approach can traverse a relatively large distance in chemical space using relatively few (50) generations.This paper presents a comparison of a graph-based genetic algorithm (GB-GA) and machine learning (ML) results, compiled by Yang et al.et al.J(m)-values of 4.3 \u00b1 0.6 compared to 4.9 \u00b1 0.6 found using 5000 property evaluations. While the results are slightly worse than the RNN results, the GB-GM-based method is several orders of magnitude faster. In both cases the MCTS approach essentially extracts the main hydrophobic structural motif (a benzene ring) found in the training set. The MCTS results thus seem more dependent on the composition of the training set than the GA approach for this particular property.The paper also introduces a new non-ML graph-based generative model (GB-GM) that can be parameterized using very small data sets and combined with a Monte Carlo tree search (MCTS) algorithm such as the one used by Yang et al.While the results are quite encouraging, it is important to perform similar comparisons for other properties before drawing general conclusions. In a very recent study Brown There are no conflicts to declare.Supplementary informationClick here for additional data file."}
+{"text": "The synthesis and characterisation of a 1-titanacyclobuta-2,3-diene complex, an organometallic analog of elusive 1,2-cyclobutadiene, is presented. rac-(ebthi)Ti(Me3SiC3SiMe3)] ), a formal metallacyclic analogue of a non-existent four-membered 1,2-cyclobutadiene, is described. By variation of the cyclopentadienyl ligand of the titanocene precursor it was possible to stabilise this highly exotic compound which selectively reacts with ketones and aldehydes to yield enynes by oxygen transfer to titanium. Analysis of the bonding and electronic structure of the metallacycle shows that the complex is best described as an unusual antiferromagnetically coupled biradicaloid system, possessing a formal Ti(iii) centre coordinated with a monoanionic radical ligand.The synthesis of an unusual 1-metalla-2,3-cyclobutadiene complex [ Later, 2SiMe3 and \u03b1-CH2N(SiMe3)2 substituted titanocene alkyne complexes was found to be unsuccessful.3 framework prior to coordination to the metal. We have thus revisited and optimised the synthesis of a previously reported 1,3-dilithioallene precursor [Li2(Me3SiC3SiMe3)]2ZrCl2]. To our surprise, we obtained two unusual allenediide bridged dizirconocene complexes [Cp2Zr(RC3R)2ZrCp2] and [Cp2Zr(Cl)RC3R(Cl)ZrCp2] (R = SiMe3),2Zr(RC3R)2ZrCp2] degrades under mass spectrometry conditions into the desired mononuclear 1-zirconacyclobuta-2,3-diene compound. In this contribution, we report on the synthesis and characterisation of the first 1-metalla-2,3-cyclobutadiene complex of a group 4 metal as well as the reactivity of this unusual complex.To further explore the frontiers of the chemistry of group 4 metallacycles Jemmis, Schulz and Rosenthal have computationally investigated the possibilities to stabilise planar 1-metalla-2,3-cyclobutadienes and found that the incorporation of electron-donating substituents at \u03b1-carbon atoms could be beneficial.2TiCl2] with [Li2(Me3SiC3SiMe3)]. 1H NMR analysis of an aliquot taken after a reaction time of 16 hours at room temperature shows the formation of several Cp containing products along with a large number of resonances in the SiMe3 region of the spectrum, out of which we identified the coupling product 1 and observed a slow colour change from red to brown. NMR analysis of the reaction mixture shows the formation of unidentified titanocene species along with the coupling product 1 as the main species, which can be isolated after column chromatographic workup in 90% yield allenes supports this proposal.21To evaluate the influence of the metal centre we first adapted our previously reported procedure0% yield . The for and the allene precursor Me(Me3Si)C3(SiMe3)Me to form the desired four-membered metallacycle and ethane. This reaction is slightly exergonic and thus in principle feasible ] at low temperature we proposed formation of a 1-titana-2,3-cyclobutadiene (vide supra), which is in accordance with the computed exergonic reaction of Cp2TiMe2 and Me(Me3Si)C3(SiMe3)Me . The fact that a coupling reaction leading to 1 was observed in reactions with Cp and Cp* complexes indicates that at some stage of the reaction the interaction of an intermediately formed C3 framework with the Ti centre occurred. ansa-Cp complexes in many cases show reactivities that are comparable to Cp analogues and furthermore exhibit additional stabilisation of the metallocene through the bridging unit. Subtle differences in reactivity (e.g. formation of different products or faster conversion) are often referred to as the ansa effect.rac-(ebthi)TiMe2] and Me(Me3Si)C3(SiMe3)Me is even more thermodynamically favourable .In a previous study we had computed the isodesmic exchange reaction of rac-(ebthi)TiCl2] and [Li2(Me3SiC3SiMe3)] at room temperature in pentane can be explained by the formation of 1 as a byproduct which was identified by NMR spectroscopy and this nicely demonstrates the subtle differences in reactivity along the series Cp\u2013rac-(ebthi)\u2013Cp*. Single crystals suitable for X-ray analysis were obtained from a saturated pentane solution at room temperature.We have thus next reacted complex we have performed stability tests. Therefore, we exposed solutions of 2 to air and moisture and found that, in both cases, slow formation of the propyne Me3SiC2CH2SiMe3 takes place (see ESIiii) species takes place.To gain first insights into the reactivity of the isolable and unusual biradical coupling with formal insertion of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond into the M\u2013C bond being the first step of the reaction. Further studies to understand the structural principles as well as further investigations regarding the reactivity of 2 and related complexes will be done in our lab in the future.For the first time, we have shown that through combination of suitable metal centre, cyclopentadienyl ligand and substituents at the CThere are no conflicts to declare.Supplementary informationClick here for additional data file.Crystal structure dataClick here for additional data file."}
+{"text": "The spectroscopic data base for cis-formic acid is considerably extended to make it fit for experimental benchmarking of vibrational calculation tools. cis\u2013trans isomerism of formic acid. It quintuples the previously available gas phase vibrational data base on this excited form of a strongly anharmonic planar molecule despite its limited spectral resolution. The newly determined cis-formic acid fundamentals allow for a balanced vibrational benchmark on both rotamers of formic acid. Assuming the adequacy of vibrational perturbation theory, it reveals weaknesses of standard methods for these systems like B3LYP-D3(BJ)/aVQZ VPT2 or PBE0-D3(BJ)/aVQZ VPT2. The functionals \u03c9B97-XD and M06-2X additionally suffer from severe integration grid size and symmetry dependencies. The vibrational benchmark suggests B2PLYP-D3(BJ)/aVQZ VPT2 and MP2/aVQZ VPT2 as partially competitive and in any case efficient alternatives to computationally demanding coupled cluster vibrational configuration interaction calculations. Whether this is due to fortuitous compensation between electronic structure and vibrational perturbation error remains to be explored.A new technique to rotationally simplify and Raman-probe conformationally and vibrationally excited small molecules is applied to the These have been surprisingly scarce until very recently, with a single exception.5Vibrational spectra of small molecules effectively probe the quality of potential energy hypersurface (PES) predictions, when combined with accurate anharmonic calculations.trans-form to the higher-energy cis-form has been of particular interest,cis-formic acid, matrix isolation has been the method of choice thus far, because the possibility of long irradiation times allows for a significant formation via laser excitation of the trans-form.cis-isomer thus suffer from a lack of gas phase experimental reference data. Two recent studies where this applies are by Tew and MizukamiAs the smallest carboxylic acid, the formic acid monomer has been addressed by a plethora of theoretical\u20131 between both rotamers of formic acid,cis-form are rare. The first gas phase band position of cis-formic acid has been published in 2006 by Baskakov and co-workers, who studied the out-of-plane bending vibration with high resolution FTIR spectroscopy. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretch coupling in jet-cooled carboxylic acid dimers.cis-formic acid. It is based on a powerful new Raman scattering approach of thermally populated and rapidly re-cooled molecules. Instead of conserving the conformational excitation by cryogenic matrix trapping,trans-form is also not an issue on the time scale of the jet expansion, making it an \u201ceasy\u201d experiment.cis-formic acid vibrational frequencies after a decade of stagnation, we provide the first systematic access to the performance of quantum chemical methods towards this model system. This decreases the likelihood of accidental error compensation between electronic structure, vibrational treatment, and matrix shifts for cis-formic acid by orders of magnitude.Due to the fairly large energy difference of 1365 \u00b1 30 cmcis-formic acid were recorded, followed by a detailed analysis of the spectra and a first benchmark of vibrational perturbation theory and literature variational data against the experimental data. It is hoped that this progress will trigger further growth in the experimental data base and its use in benchmarking the global PES of formic acid and pentatomic vibrational treatments.The structure of this paper is as follows: we briefly illustrate the general approach of how the spectra of 22.1cis-Formic acid was formed in small quantities from the trans-rotamer by heating the nozzle and its feed line to temperatures between 100\u2013190 \u00b0C.A detailed description of the experimental set-up can be found in previous publications.2.2The quantum chemical calculations shown in this work were performed with the Gaussian 09 program package (revision E.01)cis-formic acid fundamentals has been supported by scaled, harmonic frequency calculations at the B3LYP-D3(BJ)/aVTZ level, which have proven to yield sufficient agreement in a previous study.The assignment of Cs symmetry as well as a finer integration grid (pruned super fine integration grid (150\u2009974)Additionally, exploratory VPT2 calculations utilising the 33.1cis-rotamer detection, the band positions and Raman scattering cross-sections have been predicted using B3LYP-D3(BJ)/aVTZ alongside those of the trans-form. The results are displayed in cis-formic acid vibrations with the largest scattering cross-sections are \u03bd1, \u03bd2, \u03bd3, and \u03bd6, namely the O\u2013H, the C\u2013H, the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO, and the C\u2013O stretching vibration. In fact, \u03bd6 is the only stretching vibration with a distinctly larger scattering cross-section compared to trans-formic acid.To choose suitable spectral regions for trans-monomer band of lowest intensity amongst the four. Consequently, any hot band, i.e., cis-formic acid or a non-isomeric hot band originating from thermally populated low-lying energy levels of trans-formic acid, should increase in intensity with nozzle temperature, whereas any formic acid cluster band will decrease due to thermal dissociation.The experimental spectra of these four vibrational modes of both rotamers can be found in \u20131. The band position is in good agreement with the harmonically calculated, \u03bd1(F)-scaled band position of cF with a deviation of only 5 cm\u20131. Either the anharmonicity of F and cF is similar or there is error compensation with the density functional used. Another way of validating this assignment is to compare the intensity ratio of the cF (3637 cm\u20131) and F (3570 cm\u20131) bands with the energy difference of both forms. The harmonically calculated energy difference of 15.9 kJ mol\u20131 (B3LYP-D3(BJ)/aVTZ with zero point energy correction) is just below the error bounds of the only experimental value of 1365 \u00b1 30 cm\u20131 by W. Hocking.cis-formic acid at 190 \u00b0C. After correction by the theoretical cross-section ratio, the ratio of the experimental band integrals provides a cis-abundance of 2%, thus reaffirming the cF assignment. The additional bands downshifted compared to the O\u2013H stretching vibration of trans-formic acid at 3560 cm\u20131 and 3566 cm\u20131 are most likely trans-formic acid combination bands of \u03bd2 with the lowest frequency vibrations \u03bd7 (3560 cm\u20131) and \u03bd9 (3566 cm\u20131), which benefit from the large Raman scattering cross-section of the C\u2013H stretching vibration. The former is in good agreement with the predicted values of Tew and Mizukami (3566 cm\u20131)\u20131)\u03bd2 + \u03bd9) in Fermi resonance with (\u03bd3 + 3\u03bd9) at 3571 cm\u20131 and 3579 cm\u20131.The spectra in the O\u2013H stretching region show one band that increases in intensity with temperature at 3637 cm\u03bd2 region is spectrally more congested due to its low sensitivity to hydrogen bonding. In the spectral windows 2970\u20132945 cm\u20131 and 2935\u20132925 cm\u20131, there are several bands that decrease in intensity with temperature, i.e., cluster bands. The broad underlying signal is due to rovibrational O and S branches of \u03bd2. As opposed to the O\u2013H stretching region, there are two distinct bands increasing in intensity with temperature at 2925 cm\u20131 and 2873 cm\u20131. The latter deviates from the predicted band position of cis-formic acid by 14 cm\u20131. The amount of cis-formic acid at 190 \u00b0C deduced from the integrated intensities of the bands amounts to 1%, which fits the energy difference, as detailed above. Therefore, the band at 2873 cm\u20131 can be assigned to cF. The second hot band at 2925 cm\u20131 is shifted by \u201317 cm\u20131 from the fundamental of F (2942 cm\u20131). For an assignment to F, two things need to be considered: firstly, the shift directly yields the off-diagonal anharmonicity constant xi2 between \u03bd2 and a low-lying energy level vi that is thermally populated. Secondly, the intensity ratio is dependent on the Boltzmann population of that level and yields the excitation energy of the latter. Hence, the assignment can be checked by comparing the experimentally determined anharmonicity constant and intensity with the calculated values for the lowest-lying energy levels of trans-formic acid. From the anharmonicity matrix elements in \u03bd7 will most likely overlap with the fundamental, whereas the hot band originating from \u03bd9 (and \u03bd6) could overlap with a cluster band at 2938 cm\u20131 causing the highest nozzle temperature spectrum (red) and the lowest nozzle temperature spectrum (black) to have similar intensities. However, due to the spectral congestion in this area, reliable assignments are not feasible. Additional depolarisation measurements to subtract the O and S branches from the sharp Q peak are currently ongoing and will be addressed in detail in a subsequent publication. Here we focus on the straightforward assignment of the 2925 cm\u20131 band. Its observed shift of \u201317 cm\u20131 perfectly matches the calculated anharmonicity constant x28. The expected intensity ratio at 190 \u00b0C of around 4% approaches the observed ratio of 3%, so that it can be assigned to \u03bd2 + \u03bd8 \u2013 \u03bd8.The \u03bd3 spectral region at nozzle temperatures of 23 \u00b0C, 110 \u00b0C, 140 \u00b0C, and 170 \u00b0C can be found in a previous publication.\u03bd3 region. Briefly, the cis-formic acid band can be seen at 1818 cm\u20131, which deviates from the calculated, \u03bd3(F)-scaled band position by 3 cm\u20131. The hot band downshifted by 7 cm\u20131 from F can most likely be attributed to \u03bd3 + \u03bd7 \u2013 \u03bd7, with a negligible (1 cm\u20131) deviation of the calculated anharmonicity constant x37 compared to the experimentally observed value and a reasonable Boltzmann population match (14% from the level energy and 10% from the Raman spectrum). The hot band intensity qualitatively rules out major contributions from higher energy levels such as \u03bd8. There are two weaker potential hot bands shifted from F by +6 cm\u20131 and \u201313 cm\u20131 with intensities of around 1\u20132% compared to F. An assignment is not possible since the shifts do not match the predicted anharmonicity constants scale\" fill=\"currentColor\" stroke=\"none\">O stretching vibration.A first analysis of the \u03bd6 of trans-formic acid at 1105 cm\u20131. The shifts amount to \u20134 cm\u20131, \u20137 cm\u20131, and \u201311 cm\u20131 with intensities of around 7%, 3%, and 7% of \u03bd6 at 190 \u00b0C. To assign \u03bd6 of cis-formic acid, the shifts are compared to the calculated anharmonicity constants xi6 in x67 and x68 agree (\u20133.7 cm\u20131). In addition, x69 and x66 are very similar (\u20135.6 cm\u20131 and \u20136.2 cm\u20131). Therefore, it seems likely that the bands at 1101 cm\u20131 and 1097 cm\u20131 are a result of overlapping hot bands. The slightly higher intensity of the former is a result of the greater overlap with the fundamental and the lower energy of \u03bd7 and \u03bd8 compared to \u03bd9 and \u03bd6. The next higher energy level is \u03bd5 with a predicted band position of 1219 cm\u20131. A hot band originating from \u03bd5 is expected to be shifted by \u201314.3 cm\u20131 from \u03bd6 of trans-formic acid -scaled harmonic B3LYP-D3(BJ)/aVTZ calculations. Additionally, the observed intensity matches the calculated energy difference between both rotamers, considering the four times larger predicted scattering cross-section of \u03bd6 of cis-formic acid compared to the trans-form determined from high resolution FTIR measurements\u20131 or +23 to \u201321 cm\u20131, dependent on the matrix site. This scatter is of a similar order of magnitude as the cis\u2013trans spectral differences themselves, which are also listed in 15The band positions of all stretching vibrations of 3.2cis-formic acid have been compared to vi(F)-scaled harmonic band positions calculated at the B3LYP-D3(BJ)/aVTZ level, which has shown to be quite valuable in supporting the assignment. The small size of the formic acid monomer and its structural rigidity enable anharmonic vibrational perturbation theory calculations (VPT2),trans-formic acid monomer at various levels of theory in a study of the trans-formic and -acetic acid monomers and their nitrogen clusters.trans-acetic acid monomer, where the presence of the floppy methyl groups resulted in instabilities such as a wavenumber increase of the lowest frequency vibration compared to the harmonic case. The newly determined band positions of cis-formic acid thus enable a significantly extended VPT2 benchmark involving both rotamers, which should not suffer from such methyl torsion instabilities.So far, the band positions of cis-formic acid as well as the band position difference between the cis- and trans-fundamentals. The methods tested are the same as in \u20131 . All other methods fail to predict the cis-formic acid band positions correctly despite generous experimental error bars for the stretching vibrations. An accurate prediction of \u03bd9 (and the respective shift) is evidently unrealistic due to the high accuracy of the high resolution measurements. The lower resolution Raman spectra are seen to be fully adequate to challenge theory on an absolute wavenumber scale. The vibrations where the shift is predicted within the experimental error for most methods are the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO and C\u2013O stretching vibrations, whereas the largest divergence is observed for the C\u2013H stretching vibration. This is not surprising as the C\u2013H stretching vibration is prone to stretch-bend Fermi resonance, although the VPT2 code employedcis-formic acid, which is amplified by Fermi resonance. If the band labels are switched, the agreement increases significantly \u2013 the severe underestimation of the band position of \u2013142 cm\u20131 and \u0394\u03bd\u0303i(cF\u2013F) clearly illustrates that there are few reliable methods. In case of PM3, this is not surprising. It is the only method that fails to predict the energetic order of the vibrations correctly with \u03bd4 and \u03bd6 switched. Other methods with particularly severe deviations from experiment are \u03c9B97-XD (cf. \u03bd1 and \u03bd9) and M06-2X . The large underestimation of \u03bd\u03032(cF) and \u0394\u03bd\u03032(cF\u2013F) of M06-2X is enhanced by a level switch between resonance partners, as discussed above. All other methods predict the correct sequence of fundamental and overtone. Another numerical or fundamental deficiency of M06-2X/aVQZ VPT2 is the incorrect sign of the total anharmonicity of \u03bd9 of cis-formic acid, which gives rise to a large overestimation of the anharmonic band position (+163 cm\u20131). In combination with an overestimation of the negative anharmonicity of \u03bd9 of trans-formic acid, this results in a severe overestimation of the shift (+308 cm\u20131) between both rotamers. As such, this data point has been omitted from \u03bd3 and \u03bd6), whereas B3LYP-D3(BJ) predicts the shifts correctly in three of the five cases . Both exhibit similar deviations with respect to the band positions. Since the rotational constant prediction of B3LYP-D3(BJ) is also more accurate, it is the overall better choice. MP2 is particularly good for the description of the lower frequency modes \u03bd6 and \u03bd9 and overshoots for \u03bd1 and \u03bd2. For \u03bd3, an agreement with the shift is reached with the largest basis set aVQZ. It is generally rewarding that basis set sensitive methods tend to move towards the experimental region with increasing basis set size and shows only small deviations for the other two. The band positions are slightly, but consistently underestimated, apart from \u03bd2, where a small overestimation occurs for the larger basis sets, and \u03bd9, which is slightly overestimated for all basis set sizes.A comparison of the individual performance of the methods for the determination of size cf.. Another\u03bd9 differs solely by \u20131 cm\u20131. With regard to the shifts, only one is predicted within the experimental uncertainty (\u03bd3), but the shift of \u03bd9 differs solely by about 1 cm\u20131. Deviations are generally small and on the same order as for B2PLYP-D3(BJ)/aVQZ VPT2 or MP2/aVQZ VPT2. The agreement of the MCTDH calculations of Richter and Carbonni\u00e8re\u03bd3, where the value is with 36 cm\u20131 just outside the experimental confidence interval (41 \u00b1 4 cm\u20131). The band position of the C\u2013H stretching vibration is predicted within the experimental accuracy and the \u03bd9 prediction deviates only by 2 cm\u20131. However, the latter gas phase value was the only band position of formic acid known in the gas phase before cis-values were true predictions for the isolated molecule.The band positions and shifts obtained from the VCI calculations of Tew and Mizukamicis-formic acid band position (ci) and the band position shift between cis and trans (\u0394i). The size of the deviation from experiment is encoded in the octagon size. A point on a node with the smallest octagon translates into theoretical agreement within the experimental error bars (\u00b12 cm\u20131 for the band position and \u00b14 cm\u20131 for the shifts). Correspondingly, a point on a node with the nth octagon implies a deviation of that value by up to n confidence intervals from experiment. The predicted band position for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching vibration of cis-formic acid by Tew and Mizukami (1824 cm\u20131)\u20131 from the Raman jet value of 1818 cm\u20131. Considering the experimental confidence interval of \u00b12 cm\u20131, the prediction for c3 lies on the third octagon, or in other words, three nodes away from the origin on the c3 axis. Note that the origin in these diagrams cannot be met due to the experimental uncertainty. The sign of the deviation is illustrated by the colour shade of the symbol, whereby a dark colour shows over- and a light colour underestimation. The intermediate shade represents an indeterminate sign of the deviation, which can be seen for the shift of the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO stretching vibration \u03943 of Tew and Mizukami. The aforementioned consistent overestimation of the VCI calculations of Tew and Mizukami (T & M) (apart from \u03943) can thus be directly seen by the otherwise dark-coloured symbols. The MCTDH method of Richter and Carbonni\u00e8re falls closer to the origin and varies more in sign. Therefore, it shows superior agreement with experiment compared to the results of Tew and Mizukami. The tendency of the B2PLYP-D3(BJ)/aVQZ VPT2 calculations to underestimate the band position ci as well as its ability to predict most shifts within the experimental accuracy is illustrated. Altogether, et al.trans-formic acid only improves slightly when moving from a matrix to the gas phase. PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO) stretching vibrations in an Ar matrix, which mimic the underestimation of these vibrations by the B2PLYP functional in the gas phase. Such good agreements for the wrong reason must be avoided in proper benchmarking. Only the gas phase comparison can provide a realistic picture of the electronic structure performance.Another way of visualising the agreement of the theoretical predictions of Tew and Mizukami, Richter and Carbonni\u00e8re, and results obtained with vibrational perturbation theory (B2PLYP-D3(BJ)/aVQZ VPT2) with experiment is shown in trans-formic acid, the coupling constants to levels with significant thermal population at 190 \u00b0C predicted with B3LYP-D3(BJ)/aVTZ (see \u20131 (x36), which is below the spectral resolution of the Raman experiment.With regard to the previous assignment of hot bands of aVTZ see are in g3.3Cs symmetry and a finer integration grid ).i.e., 10 values.As previously mentioned in Section 2.2, all production calculations have been carried out without the use of symmetry using the pruned ultra fine integration grid of Gaussian 09.\u20131) dependence on symmetry. The size of the deviation depends largely on the density functional theory method used as well as on the vibration. The most sensitive vibrations of the fundamentals discussed in this work are the O\u2013H stretching (\u03bd1) and out-of-plane bending vibration (\u03bd9), while the smallest deviations are observed for the C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO (\u03bd3) and C\u2013O stretching vibrations (\u03bd6). For B3LYP-D3(BJ), B2PLYP-D3(BJ), and PBE0-D3(BJ), these deviations are below \u00b110 cm\u20131, with mean absolute deviations of 2.5 cm\u20131, 1.7 cm\u20131, and 2.1 cm\u20131 for the ultra fine integration grid, respectively. Particularly severe divergence is observed for \u03c9B97-XD and M06-2X with discrepancies of up to \u201396 cm\u20131 and 133 cm\u20131, respectively. The mean absolute deviations for these methods are as large as 30.2 cm\u20131 (\u03c9B97-XD) and 59.5 cm\u20131 (M06-2X). These can be reduced by using the finer integration grid (super fine integration grid). This is illustrated in C1 and Cs symmetry is plotted for both grid sizes (black and blue squares). This decrease in divergence, however, occurs at the expense of distinctly higher computational costs. In case of \u03c9B97-XD and M06-2X, this leads to an mean absolute deviation of 2.8 cm\u20131 and 48.0 cm\u20131. The large value for M06-2X is caused by outliers where the deviation between calculations with Cs and C1 symmetry is enhanced by using the finer grid and \u03bd6(cF)).All density functional theory methods show deviations for anharmonic frequency (VPT2) calculations with and without the use of symmetry when the integration grid size is kept constant, whereas the results obtained with PM3 and MP2 have a negligible (\u22640.2 cmC1 or Cs), the band positions vary on average between 1\u20132 cm\u20131 for B3LYP-D3(BJ), B2PLYP-D3(BJ), and PBE0-D3(BJ). This is on the same order of magnitude as the symmetry effects discussed above. Again, a huge impact of the integration grid size is seen for \u03c9B97-XD and M06-2X, where mean absolute deviations of 28.6 cm\u20131 and up to 63.5 cm\u20131 are observed , B2PLYP-D3(BJ), and PBE0-D3(BJ). Nonetheless, one should keep in mind that individual outliers are slightly larger. Anharmonic frequency calculations with \u03c9B97-XD and M06-2X on the other hand, show substantial differences with regard to the symmetry and integration grid chosen, so that these results must be viewed with caution, as has been discussed before.Cs symmetry and the finer integration grid. Since the improvement of the accuracy is below the experimental confidence interval for the more reliable DFT methods, if present at all, Altogether, these symmetry and integration grid size dependent variations in anharmonic band positions of the fundamentals of 4cis-formic acid in a perturbation-free environment. These reference data points are essential for the validation and comparison of modern quantum chemical methods towards a more global description of this model system. Recent examples are VCI calculations of Tew and Mizukamicis- and trans-vibrations. A benchmark examining various levels of theory revealed the failure of methods like M06-2X/aVQZ VPT2 or \u03c9B97-XD/aVQZ VPT2 to give consistent results, partly due to numerical grid size and symmetry sensitivity. With the single gas phase value from 2006 compare223 cm\u20131 ), makingThere are no conflicts to declare."}
+{"text": "The first catalytic \u03b1-alkynylation of cyclic amines with the help of the N-propargylic group with an exclusive high E-stereoselectivity has been realized. N-propargylic group to afford 2- N-allylic cyclic amines with an exclusive E-stereoselectivity for the in situ formed C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond has been realized. Based on mechanistic studies, it is proven that the reaction proceeds through metal-mediated anti-1,5-hydride transfer forming an iminonium intermediate, which accepts the addition of the in situ generated 1-alkynyl metal species. The synthetic application has also been demonstrated.The first catalytic \u03b1-alkynylation of cyclic amines with the help of the N-protected cyclic amines with terminal alkynes or 1-alkynyl trifluoroborate in the presence of a stoichiometric amount of an oxidant -allylic 2-alkynyl cyclic amines by using CdBr2 (or ZnI2) as the catalyst scale\" fill=\"currentColor\" stroke=\"none\">C bond , 2a (2 equiv.), and CdBr2 (10 mol%) in tBuOMe at 120 \u00b0C were defined as the optimized reaction conditions for further study of this reaction.Then solvents were screened: when 1a. Terminal aryl acetylenes bearing electron-donating p-Me and p-MeO, and electron-withdrawing and synthetically attractive p-F, p-Cl, m-Cl, p-NO2, p-EtOOC, p-CN and p-Ac groups on the aryl ring could all afford the corresponding product 3 in moderate yields (2k) and cyclohexylacetylene (2l), were found to be sluggish affording the corresponding products in 31% and 40% yields, respectively and 1-hexyne (2n) are also compatible of 2 may coordinate better with the C\u2013C triple bond to trigger the 1,5-H transfer reaction.Based on the above deuterium labeling experiments and the products in the amine 3 . In addi3ee and 3am 8 and 10 equiv. of DMSO afforded the Pauson\u2013Khand reaction product 8 in 45% yield.19Furthermore, diversified synthetic utilities of these two products were demonstrated. Suzuki coupling between 1% yield . Deprote diyne 7 . SequentN-propargylic cyclic amines, providing 1-(2(E)-alkenyl) 2- cyclic amines highly stereoselectively. Further studies on identifying the chiral catalyst, the scope of nucleophiles, and their applications to natural products are being actively pursued in the laboratory.In conclusion, we have succeeded in developing a catalytic \u03b1-alkynylation of There are no conflicts to declare.Supplementary informationClick here for additional data file.Supplementary informationClick here for additional data file."}
+{"text": "Aza-analogues of carbocations inhibit \u03b4-cadinene synthase: 1,6-cyclisation. E,E)-FDP. Previous work with this enzyme using substrate analogues revealed the ability of DCS to catalyse both 1,10- and 1,6-cyclisations of substrate analogues. To test whether this apparent promiscuity was an artefact of alternate substrate use or an inherent property of the enzyme, aza analogues of the proposed \u03b1-bisabolyl cation intermediate were prepared since this cation would be formed after an initial 1,6-cyclisation of FDP. In the presence of 250 \u03bcM inorganic disphosphate both (R)- and (S)-aza-bisaboyl cations were potent competitive inhibitors of DCS . These compounds were also shown to be potent inhibitors of the 1,6-cyclase amorpha-4,11-diene synthase but not of the 1,10-cyclase aristolochene synthase from Penicillium roquefortii, demonstrating that the 1,6-cyclase activity of DCS is most likely an inherent property of the enzyme even when the natural substrate is used and not an artefact of the use of substrate analogues.\u03b4-Cadinene synthase (DCS) is a high-fidelity sesquiterpene synthase that generates \u03b4-cadinene as the sole detectable organic product from its natural substrate ( Terpene synthases catalyse some of the most complex reactions in the natural world. From a small pool of isoprenyl diphosphates they generate a myriad of hydrocarbons and alcohols that are often processed into thousands of terpenoids with diverse biological activities with many potential applications for instance as agrochemicals or therapeutic agents.1Aspergillus terreus in both closed and open conformations along with complexes containing the complete substrate , diphosphate anion and/or Mg2+ co-factors2+-ion is followed by coordination of the prenyl diphosphate substrate and a second Mg2+ ion; coordination of a third Mg2+ ion triggers active site closure to form the Michaelis complex.Abies grandis generate 34 and 52 products from farnesyl diphosphate (1), respectively.Gossypium arboreum is a high-fidelity sesquiterpene synthase that catalyses the formation of the bicyclic hydrocarbon (+)-\u03b4-cadinene (7),307DTYD311 on helix D, but instead of the usual characteristic NSE/DTE Mg2+ binding motif, DCS has a second aspartate rich motif D451DVAE455 on helix H.vide infra).R)-nerolidyl diphosphate ((3R)-NDP, (2)) as an enzyme-bound intermediate. In pathway (a), a 1,10-macrocyclisation occurs to generate cis-germacradienyl cation (4). A subsequent -hydride shift is followed by a 1,6-electrophilic ring closure to cadinenyl cation (6), from which \u03b4-cadinene (7) is formed after proton loss from C6. In pathway (b), a 1,6 ring-closure of 2 is followed by a -hydride shift from C1 to C7; subsequently a second ring closure and a -hydride shift lead to cadinenyl cation, an intermediate common to both pathways. In previous work, using substrate analogues we were unable to definitively rule out pathway (b) and indeed when 6-fluorofarnesyl diphosphate (6F-FDP) was used as a substrate analogue it proved to be a potent inhibitor (Ki = 2.4 \u03bcM), giving no detectable pentane-extractable products when incubated with DCS. This result is consistent with an initial 1,6-cyclisation pathway since it would be expected to undergo 1,10-ring closure and give an abortive product rather than inhibit the enzyme in the latter scenario. On the other hand, 2-fluorofarnesyl diphosphates (2F-FDP) and 10-fluorofarnesyl diphosphate (10F-FDP) gave products arising from 1,10- and 1,11 ring-closures, respectively, consistent with an initial 1,10-ring closure mechanism.12The details of terpene synthase chemistry2 hybridised carbocationic carbon of a given intermediate with an sp3 hybridised nitrogen in an amine analogue or with a sp2 hybridised nitrogen in an iminium ion. Although the tetrahedral tertiary ammonium ions inherently are imperfect geometric analogues of the planar carbocations, these aza-terpenoids are thought to mimic the topological and electrostatic properties of carbocations generated by these enzymes.Hence examination of the catalytic mechanism of DCS using FDP analogues has led to inconclusive, yet intriguing results, showing that this enzyme has the potential to use alternative reaction pathways. Yet the question arises, is this simply an artefact of the substrate used or is this an inherent property of the enzyme? The work described here provides alternative mechanistic data for the DCS-catalysed transformation of FDP to \u03b4-cadinene using aza-analogues of putative carbocation intermediates. Although the highly unstable carbocationic intermediates formed during terpene synthase catalysis, cannot be isolated, it is possible to replace the spS. Comparison of their effect upon catalysis by AS and amporpha-4,11-diene synthase (ADS), enzymes that follow 1,10- and 1,6-ring-closure mechanisms, validate the result that DCS has inherent 1,6- as well as 1,10 ring closure activity.Hence, the use of strategically designed aza-analogues may enable the disentanglement of the possible reaction mechanisms catalysed by DCS. Here we report the stereoselective synthesis of the two enantiomers of aza-bisabolyl cation and their kinetic evaluation as inhibitors of DC8 is a reaction intermediate on the pathway to \u03b4-cadinene (7), one or both of enantiomeric aza-analogues of 11 as a chiral auxiliary.3 as the base in CH2Cl2, diester 16 was isolated in 60% yield. Again, an asymmetric Diels\u2013Alder reaction with 2-methylbutadiene was carried out, this time at \u201310 \u00b0C in CH2Cl2 using TiCl4 as a Lewis acid catalyst yielding the R ester in 84% yield (ee = 92% and de = 97%).l-pantolactone not used for bulk preparation for the R-enantiomer of 18. Optical purity of all subsequent compounds was checked using chiral GC, HPLC and/or polarimetry and in all cases no loss of optical purity was detected in later synthetic steps.Both enantiomers of pared.18 . This waolactone as a chiS-enantiomer of 11. Hydrolysis of 14 using LiOH in an equivolume mixture of THF, water and methanol for 1 h at 50 \u00b0C gave carboxylic acid 18 in near quantitative yield. 18 was converted to p-methoxybenzyl urethane derivative 19 by treatment with diphenylphosphorylazide (DPPA) followed by a Curtius rearrangement in the presence of p-methoxybenzyl alcohol, which proceeded with strict retention of stereochemistry.19 was 60% over the two steps. Final conversion to (S)-11 was achieved first through reduction with LiAlH4 in anhydrous Et2O (50%) then HBTU mediated coupling to 4-methypent-3-enoic acid (70%) followed by a second reduction with LiAlH4 in Et2O. To prevent air oxidation upon storage the product was converted to its hydrochloride salt with HCl in ether, yielding (S)-11\u00b7HCl in 55% yield over the final two steps. The optical purity of (S)-11 was estimated to be \u226598% by comparison with previously reported data.R)-11.Both syntheses now proceeded in identical manner and Penicillium roqueforti (AS) and amorpha-4,11-diene synthase (ADS). These two enzymes are known to proceed via 1,10- and 1,6-cyclisations of the initial carbocation during their catalytic cycle -11 and (S)-11 were tested as inhibitors using a standard radiolabelled assay involving conversion of tritium labelled FDP by each enzyme and scintillation counting of the pentane extractable products.i pairs and inhibition was assessed both in the presence and absence of 250 \u03bcM diphosphate (11 with diphosphate has been observed previously for a variety of other terpene synthases.Recombinant AS and ADS were prepared and purified according to previously published procedureshosphate . Synergiv0 = kcat[E][S]/(KM + [S]). The mode of inhibition was determined by inspection of double reciprocal plots and observed to be competitive in all cases where inhibition was significant at low concentrations of 11. KI was determined from a plot of inhibitor concentration versus K\u2032M/(kcat[E]) where K\u2032M = KM(1 + [I]/KI).Kinetic data were fitted by non-linear regression to the Michaelis\u2013Menten equation (i had little effect on the ability to inhibit AS (KI > 200 \u03bcM in both the presence and absence of PPi for AS). Both enantiomers of 11 acted as competitive inhibitor of ADS, showing that they are able to compete effectively with the natural substrate FDP at the active site. As these aza-compounds cannot be turned over by ADS, these result support the intermediacy of an \u03b1-bisabolyl cation in the biosynthesis of amorpha-4,11-diene, in agreement with the findings of Picaud et al.R-enantiomer of the \u03b1-bisabolyl cation is the sole intermediate formed in the biosynthesis of amorpha-4,11-diene. Therefore, only the R enantiomer of 11 would be expected inhibit ADS; however, if the S-enantiomer was a slightly more potent inhibitor (Ki = 50 \u03bcM for (R)-11versus 25 \u03bcM for (S)-11) et al. showed that both enantiomers of the aza-analogue 11 were equally effective inhibitors of trichodiene synthase.i enhanced inhibition of ADS by both enantiomers, improving the Ki approximately 20-fold (Ki = 1.5 and 3.7 \u03bcM for the S and R enantiomers respectively) demonstrating that the active site of ADS prefers a cation\u2013anion pair in its active site.The inhibition data for AS and ADS validate both of these compounds as valuable mechanistic probes for the present investigation since they are poor inhibitors of AS and potent inhibitors of ADS. PP6) as previously described.6 in the presence of PPi but only poor inhibitors in its absence -\u03b4-cadinene (7), which would only be expected if DCS had a 1,6-cyclase activity. The use of a variety of substrate analogues possessing different stereochemistry and heteroatoms did not lead to clear results regarding whether DCS follow a 1,6 or 1,10 pathway.2) was suppressed using a fluorine atom at C2 then a 1,10 cyclisation was observed (25) was the DCS catalysed product from the transoid -2-fluorofarnesyl diphosphate (24) while the cisoid substrate analogue 26 gave the cisoid product 2F-helminthogermacrene A (27).7 along two distinct reaction paths.11 acts as a competitive inhibitor of the DCS catalysed conversion of FDP provides strong evidence that DCS can efficiently use a 1,6-cyclisation pathway.The aza-bisabolyl cations observed . 2-FluorR)-11 acts as a weak inhibitor in the absence of PPi is more difficult to explain. It was previously suggested that, in the DCS active site pocket, the alkenyl chain of (3R)-nerolidyl diphosphate (2) is ideally positioned to ensure the formation of the \u03b1-bisabolyl cation with an R configuration at C6 -9 formation is expected (R)-11 should mimic better the \u03b1-bisabolyl cation generated by this enzyme, and therefore act as competitive inhibitor with higher binding affinity when compared with the S-enantiomer. The evidence that both enantiomers of 11 are equally as effective in the presence of PPi is consistent with a permissive model of the active site structure, according to which an active site should accommodate a variety of rearranged intermediates of different shape and charge distribution without being rigidly complementary to a single intermediate. On the other hand, their lack of inhibitory effects on the 1,10-cyclase PR-AS shows that a major difference in the connectivity of the aza-analogue compared to the carbocation intermediate (i.e. bisabolyl cation rather than the 10-membered ring containing germacrenyl cation) renders them ineffective as inhibitors; hence the 1,6-cyclase activity of DCS postulated previouslyThe fact that inorganic diphosphate led to a more tightly bound active site carbocation/diphosphate ion pair is consistent with previous work where often the active site recognises a cation-PPi pair more effectively than the cation alone.on at C6 .12 The Cexpected . Hence tTerpene synthases can generate great structural and stereochemical complexity in one synthetic step and have therefore potential as powerful synthetic biocatalysts for the generation of many bioactive compounds.General experimental procedures, enzyme preparation and purification are described in ESIR)-pantolactone and Et3N in anhydrous CH2Cl2 (10 mL) at \u201324 \u00b0C. The resulting mixture was stirred for 5 h at \u201324 \u00b0C, and subsequently washed with aqueous 1 M HCl (10 mL). The aqueous phase was then extracted with CH2Cl2 (3 \u00d7 20 mL). The combined organic phases were washed with saturated NaHCO3 solution (3 \u00d7 20 mL), water (3 \u00d7 20 mL) and brine (3 \u00d7 20 mL). The organic phase was dried over MgSO4, concentrated under reduced pressure and the residue was purified by flash chromatography on silica (EtOAc\u2009:\u2009hexane 4\u2009:\u20096) to yield the pure compound as a yellow oil . \u03b4H 6.48 scale\" fill=\"currentColor\" stroke=\"none\">C), 6.18 scale\" fill=\"currentColor\" stroke=\"none\">CH2), 5.93 scale\" fill=\"currentColor\" stroke=\"none\">C), 5.40 scale\" fill=\"currentColor\" stroke=\"none\">OCH\u2013O), 4.03 scale\" fill=\"currentColor\" stroke=\"none\">O), 1.17 , 1.08 ; \u03b4C 174.7 scale\" fill=\"currentColor\" stroke=\"none\">OCHO), 172.5 scale\" fill=\"currentColor\" stroke=\"none\">OC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tH2), 134.0 scale\" fill=\"currentColor\" stroke=\"none\">CHC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO), 118.7 scale\" fill=\"currentColor\" stroke=\"none\">CHC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO), 76.1 scale\" fill=\"currentColor\" stroke=\"none\">OCHO), 74.6 (OCH2CH), 40.2 (C\u2013(CH3)2), 23.4 (CH3), 23.0 (CH3). \u03b1D +10\u00b0 . Data are in agreement with previous work.Freshly distilled propenoyl chloride was added over 1 h to a stirred solution of in anhydrous CH2Cl2 (5 mL) at \u201310 \u00b0C, TiCl4 was added, and the resulting solution was stirred under argon at \u201310 \u00b0C for 1 h. 2-Methylbutadiene was then added over 5 min and the mixture was left stirring for 3 h at \u201310 \u00b0C. The reaction was quenched by addition of 10% Na2CO3 in water (5 mL). The aqueous phase was then extracted with CH2Cl2 (3 \u00d7 20 mL). The organic layers were combined, washed with H2O (3 \u00d7 10 mL), brine (3 \u00d7 10 mL), dried over anhydrous MgSO4, filtered and concentrated under reduced pressure. The residue was purified by flash chromatography on silica (EtOAc\u2009:\u2009hexane 2\u2009:\u20098) to yield pure 17 as a colourless oil . \u03b4H 5.32 scale\" fill=\"currentColor\" stroke=\"none\">O,) and scale\" fill=\"currentColor\" stroke=\"none\">), 3.98 , 2.69\u20132.51 scale\" fill=\"currentColor\" stroke=\"none\">O), 2.19 scale\" fill=\"currentColor\" stroke=\"none\">), 1.98 , 1.73 , 1.58 scale\" fill=\"currentColor\" stroke=\"none\">), 1.13 , 1.04 . \u03b4C 174.7 scale\" fill=\"currentColor\" stroke=\"none\">OCHO), 172.5 scale\" fill=\"currentColor\" stroke=\"none\">OC PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tH2), 134.0 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 118.7 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 76.1 scale\" fill=\"currentColor\" stroke=\"none\">OCHO), 74.6 (OCH2C), 40.2 (C\u2013(CH3)2), 38.9 scale\" fill=\"currentColor\" stroke=\"none\">O), 28.9 scale\" fill=\"currentColor\" stroke=\"none\">CCH2), 27.7 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2), 25.2 scale\" fill=\"currentColor\" stroke=\"none\">CCH2CH2), 23.4 (CCH3), 23.0 (CCH3), 19.8 scale\" fill=\"currentColor\" stroke=\"none\">CH). LRMS (EI+) m/z: 252.13 (50%), 122.07 (20), 94.08 (100), 79.05 (30), 67.05 (10). \u03b1D \u201351.3 . Data are in agreement with previous work.16To a solution of S)-4-benzyloxazolidin-2-one in anhydrous THF (12 mL) at \u201378 \u00b0C, n-BuLi was added dropwise over 30 minutes and the mixture stirred for a further 3 h at \u201378 \u00b0C. Freshly distilled acryloyl chloride was added dropwise over 20 minutes and the reaction stirred for 2 h at \u201378 \u00b0C. The reaction was then allowed to warm to room temperature overnight. The reaction was quenched with sat. NH4Cl (20 mL) and extracted with diethyl ether (3 \u00d7 30 mL). The organic layer was washed with water (3 \u00d7 40 mL), saturated aqueous NaHCO3 (3 \u00d7 40 mL), dried (MgSO4), filtered, and concentrated under reduced pressure. Flash chromatography on silica gel (hexane\u2009:\u2009ethyl acetate 6\u2009:\u20094) afforded 13 as a colorless solid . \u03b4H 7.45 scale\" fill=\"currentColor\" stroke=\"none\">CH2), 7.23 , 6.54 scale\" fill=\"currentColor\" stroke=\"none\">CH2), 5.87 scale\" fill=\"currentColor\" stroke=\"none\">C), 4.68 , 4.14 , 3.29 scale\" fill=\"currentColor\" stroke=\"none\">CHHPh), 2.74 \u03b1D \u201386\u00b0 . Data are in agreement with previous work.14To a solution of at \u2013100 \u00b0C, were added 2-methylbutadiene in anhydrous CH2Cl2 (5.0 mL) and Et2AlCl . The reaction was stirred at \u2013100 \u00b0C for 30 min then the mixture was poured into ice cold aqueous hydrochloric acid . The mixture was extracted with CH2Cl2 (2 \u00d7 10 mL). The combined organic layers were dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure. The product was purified by flash chromatography on silica (EtOAc\u2009:\u2009hexane\u2009:\u2009Et3N 92\u2009:\u20097\u2009:\u20091) to yield the Diels Alder adduct (14) as a white crystalline solid . \u03b4H 7.34\u20137.10 , 5.36 scale\" fill=\"currentColor\" stroke=\"none\">C), 4.63 , 4.23\u20133.95 , 3.60 scale\" fill=\"currentColor\" stroke=\"none\">O), 3.20 , 2.70 , 2.20\u20131.6 scale\" fill=\"currentColor\" stroke=\"none\">C), 1.64 \u03b1D +79 . LR-MS (EI+) m/z: 299.15 (100% M+), 300.16 (15), 269.06 (18), 267.07 (50), 232.10 (20), 178.08 (100), 146.07 (30), 140.03 (55), 122.07 (20), 91.00 (65), 63.00 (30). Data are in agreement with previous work.To a stirred solution of r adduct as a whi14 or 17 (0.32 mmol) in THF\u2009:\u2009MeOH\u2009:\u2009H2O , LiOH was added, and the resulting mixture was vigorously stirred for 1 h at 50 \u00b0C. The reaction was then cooled to room temperature and concentrated under reduced pressure. The resulting slurry was dissolved in H2O (10 mL) and extracted with CH2Cl2 (3 \u00d7 5 mL). The resulting aqueous phase was acidified to pH = 2 at 0 \u00b0C with 15% HCl, extracted with a mixture of n-pentane\u2009:\u2009CH2Cl2 (98\u2009:\u20092 3 \u00d7 10 mL), dried over anhydrous Na2SO4, and concentrated under reduced pressure to give 18 as a white powder . \u03b4H \u03b4 5.32 scale\" fill=\"currentColor\" stroke=\"none\">), 2.54\u20132.39 , 2.17 scale\" fill=\"currentColor\" stroke=\"none\">C), 1.93 , 1.69 , 1.59 . \u03b4C \u03b4 182.3 scale\" fill=\"currentColor\" stroke=\"none\">O), 133.8 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 119.0 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 39.0 (HC\u2013COOH), 29.13 scale\" fill=\"currentColor\" stroke=\"none\">CH3), 27.3 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 25.5 scale\" fill=\"currentColor\" stroke=\"none\">CH), 23.5 (CH3). (S)-18: \u03b1D \u201380.6 ; \u2013106.4 . (R)-18: \u03b1D +93 ; +105.5 . M.p. 82\u201392 \u00b0C. LRMS (EI+) m/z 140.06 , 136.06 (15), 125.05 (40), 122.06 (100), 95.87 (100), 94.06 (100), 93.07 (80), 79.04 (100), 77.03 (100), 68.06 (90), 67.04 (100) Data are in agreement with previous work.To a solution of 18 in anhydrous toluene (20 mL) at 0 \u00b0C, diphenylphosphoryl azide and Et3N were added. The resulting mixture was left stirring for 3 h at 100 \u00b0C before 4-methoxybenzyl alcohol was added, and the reaction was left to stir for 16 h at 100 \u00b0C. The reaction was then allowed to cool to room temperature and the solution was concentrated under reduced pressure. The residue was the purified by flash chromatography on silica gel (EtOAc\u2009:\u2009n-hexane 1\u2009:\u20099) to yield 19 as a yellow crystalline solid . \u03b4H \u03b4 7.23 , 6.81 , 5.21 scale\" fill=\"currentColor\" stroke=\"none\">C), 4.95 , 4.67\u2013460 , 3.74 , 2.29\u20132.20 , 1.93 , 2.01\u20131.86 , 1.55 scale\" fill=\"currentColor\" stroke=\"none\">CH). \u03b4C \u03b4 159.5 scale\" fill=\"currentColor\" stroke=\"none\">CO\u2013CH3), 155.8 scale\" fill=\"currentColor\" stroke=\"none\">O), 134.1 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 130.0 scale\" fill=\"currentColor\" stroke=\"none\">C aromatic), 128.7 (CCH2O), 118.3 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 113.9 scale\" fill=\"currentColor\" stroke=\"none\">C aromatic), 66.3 (CCH2O), 62.8 (CHN), 55.3 (OCH3), 31.9 (CH2CHN), 28.4 scale\" fill=\"currentColor\" stroke=\"none\">C), 28.0 scale\" fill=\"currentColor\" stroke=\"none\">C), 23.4 scale\" fill=\"currentColor\" stroke=\"none\">CCH3). \u03bdmax 3300 (N\u2013H stretch), 2900\u20132700 (C\u2013H stretch), 1650 scale\" fill=\"currentColor\" stroke=\"none\">O ester stretch), 1250 (C\u2013N stretch), 830 (aromatic CH bending); (S)-19: \u03b1D \u20139.3, (R)-19: \u03b1D +12 m.p. 69\u201371 \u00b0C LRMS (EI+) m/z: 275.15 (100% M+), 276.15 (20), 259.12 (18), 258.12 (60), 231.12 (25), 228.1128(12), 214.16 (100). HRMS (EI+) 275.1522; C16H21NO3 requires 275.1521.To a solution of 19 in anhydrous diethyl ether (7 mL) at 0 \u00b0C, was added LiAlH4 . The mixture was then heated to reflux for 5 h. The reaction was cooled to 0 \u00b0C before it was quenched by the addition of water (6 mL) and an excess of 15% NaOH solution (6 mL). The resulting mixture was left to stir at 0 \u00b0C for 1 h and the precipitate was removed by filtration through a Celite pad. The organic phase was extracted with water (2 \u00d7 10 mL) and the pooled organic layers were then washed with 10% HCl (2 \u00d7 10 mL) and the organic fraction was discarded. The combined aqueous layers were adjusted to pH 12 by dropwise addition of 10% NaOH (15 mL). The product was extracted with diethyl ether (4 \u00d7 15 mL), then dried over anhydrous MgSO4, and filtered. The product was then concentrated carefully under reduced pressure to give 20 as a volatile colorless oil . \u03b4H 5.24 scale\" fill=\"currentColor\" stroke=\"none\">C), 2.55 , 2.37 , 2.25\u20132.10 , 1.99\u20131.87 scale\" fill=\"currentColor\" stroke=\"none\">C), 1.87\u20131.66 scale\" fill=\"currentColor\" stroke=\"none\">CH), 1.61 scale\" fill=\"currentColor\" stroke=\"none\">CH), 1.60 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 1.45\u20131.26 scale\" fill=\"currentColor\" stroke=\"none\">CH). \u03b4C 134.0 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 119.1 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 54.8 (CHNH), 32.7 (CH2CHNH), 32.1 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2CH), 29.7 (CH3N), 29.0 scale\" fill=\"currentColor\" stroke=\"none\">), 23.4 scale\" fill=\"currentColor\" stroke=\"none\">) (S)-20: \u03b1D \u201379 (R)-20: \u03b1D +84 Data in agreement with previous work.14To a stirred solution of carbamate 20 and DIPEA in anhydrous DMF (6 mL), HBTU was added and the resulting mixture was stirred at room temperature for 20 min before 20 was added. The reaction was then stirred for 24 h at room temperature. The mixture was concentrated under reduced pressure and the residue was dissolved in diethyl ether (20 mL). The solution was washed with water (2 \u00d7 25 mL), 10% NaHCO3 (2 \u00d7 25 mL), 10% HCl (2 \u00d7 10 mL), and brine (25 mL) before it was dried over anhydrous MgSO4 and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel (EtOAc\u2009:\u2009hexane 4\u2009:\u20096) yielding 21 as a colorless oil . \u03b4H 5.24 scale\" fill=\"currentColor\" stroke=\"none\"> and PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCHCH2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO), 4.70\u20134.54 , 3.75 , 3.01 scale\" fill=\"currentColor\" stroke=\"none\">O), 2.75 , 2.72 , 2.20\u20131.86 , 1.71\u20131.88 , 1.75 scale\" fill=\"currentColor\" stroke=\"none\">CHCH3), 1.68 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 1.66 scale\" fill=\"currentColor\" stroke=\"none\">CCH3). (S)-21: \u03b1D \u20139.5, (R)-21: \u03b1D +10, HRMS (EI+) 221.1779; C14H23NO requires 221.1780. Data are in agreement with previous work.14To a stirred solution of 21 in anhydrous diethyl ether at 0 \u00b0C, was added LiAlH4 . The mixture was heated to reflux for 6 h then allowed to cool to room temperature and stirred for a further 12 h. The reaction was quenched by the addition of water (6 mL) and 15% NaOH (6 mL) at 0 \u00b0C and stirred for 1 h at 0 \u00b0C. The white precipitate was removed by filtration on Celite and the filtrate was extracted with diethyl ether (2 \u00d7 25 mL). The combined organic layers were dried over anhydrous Na2SO4, concentrated under reduced pressure, and the residue was purified by flash chromatography on silica (Et2O\u2009:\u2009MeOH 1\u2009:\u20099) to yield the amine as a yellow oil . \u03b4H 5.27 scale\" fill=\"currentColor\" stroke=\"none\">CH), 5.03 2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH), 2.64\u20132.44 , 2.38 , 2.23 , 2.08 , 2.04\u20131.85 , 1.85\u20131.67 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2CHN), 1.62 scale\" fill=\"currentColor\" stroke=\"none\">CH), 1.55 and 1.57 2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH). \u03b4C \u03b4 133.9 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 132.6 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 122.1 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 120.0 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 58.9 (CHN), 53.5 (CH2N), 37.9 (CH2CH2CHN), 30.8 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2N), 27.2 (CH2CCH3), 26.5 (CH3N), 25.7(CH2CH2N), 25.6 (CH3CCH3), 23.2 (CH3CCH3), 17.8 scale\" fill=\"currentColor\" stroke=\"none\">). HRMS (EI+) 207.1990; C14H25N requires 207.1987. (S)-11: \u03b1D \u201361 (R)-11\u03b1D +63 . Data are in agreement with previous work.2O (1 mL) and HCl (1 M in anhydrous Et2O) was added slowly. A light yellow precipitate was formed. The ether was concentrated under reduced pressure and the salt stored in 1.2 mL of deionised water. \u03b4H 5.38 scale\" fill=\"currentColor\" stroke=\"none\">CH), 5.14 2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH), 3.58\u20133.42 , 3.32 , 3.25\u20132.97 , 2.85 , 2.59\u20132.39 , 2.39\u20132.26 , 2.26\u20132.05 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2CH2N), 1.84 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2), 1.76 scale\" fill=\"currentColor\" stroke=\"none\">CH), 1.72 2C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tCH). \u03b4C \u03b4 136.1 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 134.3 scale\" fill=\"currentColor\" stroke=\"none\">C(CH3)2) 117.6 scale\" fill=\"currentColor\" stroke=\"none\">CCH3) 116.5 scale\" fill=\"currentColor\" stroke=\"none\">CCH3), 61.8, 61.5 (CHN), 53.0, 52.5 (CH2N), 35.9, 35.2 (CH3N) 29.1, 29.0 (CH2CH2CHN), 25.7 scale\" fill=\"currentColor\" stroke=\"none\">CHCH2N), 24.5 (CH2CCH3), 24.2, 24.0 (NCH2CH2), 23.25, 22.64 scale\" fill=\"currentColor\" stroke=\"none\">), 21.64 (CH3CCH3), 16.65 (CH3CCH3). \u03bdmax 2972 , 1379 (C\u2013N stretch), 1161, 1051 and 1022 (C\u2013N stretch), 950, 879, 815; HRMS (APCI+) 208.2057, C14H26N requires 208.2065; m.p. 131\u2013133 \u00b0C, (S)-11\u03b1D \u201362.2 , (R)-11\u03b1D +57.1 . Data are in agreement with previous work.14To a stirred solution of There are on conflicts of interest to declare.Supplementary informationClick here for additional data file."}
+{"text": "Ultra-permeable and robust membranes are prepared by creating a gradient nanoporous structure in low-cost phenolics, enabled by the spontaneous assembly of gradually enlarged phenolic nanoparticles. 2-accelerated thermopolymerization of resol in the progressive downward gelating polymer. Subsequent removal of the gelated polymer and ZnCl2 exposes the gradient nanopores. The gradient nanopores endow the phenolic structures with unprecedented permselectivity when used in membrane separation, totally rejecting fine particulates down to 5 nm dispersed in water or aggressive solvents while allowing water to permeate up to two orders of magnitude faster than other membranes with similar rejections. Our work opens up an avenue for the rational design and affordable synthesis of ultrafast membranes.Membrane technology is playing a pivotal role in providing potable water to our thirsty planet. However, the strong demand for highly permeable and durable membranes with affordable costs remains. Such membranes are synthesized herein by designing gradient nanopores in low-cost phenolics. The gradient nanopores are achieved by spontaneous assembly of phenolic nanoparticles with gradually enlarged sizes. These particles nucleate and grow as a result of ZnCl However, the selective layer also needs to be mechanically robust to withstand the pressure that drives the separation across the membrane. Therefore, asymmetric structures with a thin selective layer on top of a mechanically strong substrate are predominantly applied for membrane separation.From the Hagen\u2013Poiseuille equation which correlates the structural parameters of porous membranes with permeability (in situ performed on the surface of the polysulfone ultrafiltration (UF) membrane, producing a tight polyamide layer with a thickness of \u223c100\u2013400 nm on the UF substrate.3N4,Thin-film composite reverse osmosis (RO) membranes are best known for their asymmetric structures.via conventional methods. Alternatively, in precipitation polymerization, phenolic particles are precipitated from solution and form aggregates with certain porosity depending on the polymerization conditions. We expect that if the precipitation of phenolic particles occurs in a suitably controlled way, there might be a chance to have a well-organized assembly of phenolics with tunable porosity favoring fast mass transfer. Moreover, composite structures with a thin layer on top of a macroporous substrate have been widely used to improve the membrane permeance. And these composite structures frequently suffer from complicated preparation processes and poor interfacial adhesion between the two layers.To meet this demand, attention should also be paid to low-cost and easily available materials. Phenolic resins have long been used in many different fields because of their low cost and superior chemical, thermal, and mechanical robustness.2 and is coupled with the gelation of Pluronic polymer (PEO-block-PPO-block-PEO block copolymer) with the fast evaporation of the solvent. Under these conditions, phenolic nanoparticles nucleate and grow with gradually increased sizes from the top to the bottom and spontaneously assemble to form membranes with a gradient porous structure. Remarkably, the thus-produced phenolic membranes outperform not only commercial membranes (by a factor of 20\u201380 in terms of permeance) but also newly developed advanced membranes based on costly 2D materials. Also importantly, the phenolic membranes are selective and robust enough to completely reject fine particulates with a size down to a few nanometers dispersed either in water or in aggressive solvents. The aim of this work is to report an ultrafast membrane for water purification and also to demonstrate the unlimited potentials of low-cost materials in developing ultrafast membranes.Based on these considerations, we demonstrate herein the design and synthesis of phenolic-based advanced membranes by establishing a highly gradient nanoporous structure in phenolics. The precipitation polymerization of phenolics is accelerated by ZnCl2 was cast on the surface of a flat substrate and evaporated at 100 \u00b0C to produce a thin film supported on the substrate , Pluronic polymer (P123) and ZnCle Fig. S1. During Fig. S2a. Interes Fig. S2a. We thena. 67 nm . The pora. 67 nm . Spherica. 67 nm , formingd Fig. S3. This meWe tried to directly characterize the pore sizes. However, in the gradient structures, the pores are defined as gaps formed by stacking phenolic particles. These pores are interconnected with each other and do not have a measurable profile. Therefore, the sizes of such highly irregular pores cannot be estimated. Instead, the sizes of spherical phenolic particles from the top to the bottom of the membranes can be relatively easily measured, and the gaps between them are highly related to the particle sizes.2SO4 or water. As shown in \u20131 originate from hydroxyl groups,2.\u20131 in the spectrum of the as-synthesized phenolic film, which can be attributed to the interaction between ZnCl2 and phenolic group. With the introduction of ZnCl2, the aromatic C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tC bond in the phenolic film at 1605 cm\u20131 is enhanced due to the facilitated aromatization of the phenolic film by ZnCl2 while the deoxygenation effect of ZnCl2 weakens the characteristic \u2013C PBM data was replaced with SVG by xgml2pxml: 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000\tO bond of the phenolic film at 1648 cm\u20131.\u20131. After the removal of ZnCl2 by water or H2SO4, the merged peak is decomposed to the initial two isolated peaks at 1605 cm\u20131 and 1648 cm\u20131. The peak of C\u2013O stretching of P123 was reported to be located at 1100 cm\u20131.\u20131 as a result of the complexation of Zn2+ to P123.2 by water, the peak recovers from 1075 cm\u20131 to 1100 cm\u20131. Moreover, a peak at 1100 cm\u20131 shows up with a weaker intensity for the water-soaked sample, indicating that P123 was only partially removed by water. In contrast, after soaking in H2SO4, the peak disappears, indicating the complete removal of P123.Infrared (IR) spectroscopy was applied to reveal the change in the chemical composition of the phenolic film before and after soaking in H2SO4 are able to completely remove ZnCl2 from the phenolic films. The peak around 533 eV originates from C\u2013OH of phenolic and ether groups of P1232, releasing some coordinated \u2013OH groups. The strong peak of this group is also achieved for the H2SO4-soaked film scale\" fill=\"currentColor\" stroke=\"none\">O) of the phenolic film2SO4 is capable of removing the oligomeric phenolic group and further facilitating the crosslinking of phenolics at 100 \u00b0C, the H2SO4-soaked film exhibits the strongest peak around 284.8 eV among all the samples. Meanwhile, the degradation of ester bonds takes place in H2SO4 at high temperature, resulting in the lowest peak intensity of around 286.5 eV for the H2SO4-soaked film.X-ray photoelectron spectroscopy (XPS) was further used to analyze the phenolic films before and after soaking. Zinc and chlorine elements are distributed on the surface of the as-synthesized phenolic film but absent in the water- and acid-treated films , confirmked film . However2 was not included in the simulation systems, and this simplification does not influence the reliability of the simulated results because ZnCl2, as a small molecule, would not evidently change the relative diffusivity and collision of solute molecules.We carried out molecular dynamics (MD) simulations to investigate the diffusion and reactions of resol molecules under fast evaporation conditions. We changed the concentrations of solutes (P123 and resol with a fixed molar ratio) to describe the progressive evaporation of ethanol. The concentration of solutes was progressively decreased from the top surface to the bottom with the top surface having a 100% concentration. 2SO4, both P123 and ZnCl2 are removed, leaving behind the network composed of interconnected phenolic particles as a nanoporous membrane with gaps among the particles as the pores tapered from the bottom side to the top side and cytochrome C were measured to be 96% and 95%, respectively .2, and MXene, our phenolic membranes with gradient porosities also show \u223c1.5\u20136 times higher permeabilities and similar rejections . The gol2SO4 soaking was a homogenous film composed of small phenolic particles without a noticeable gradient porous structure . For instance, the thickness is increased to 4.7 and 12.0 \u03bcm at a molar ratio of 70 and 280, respectively. Considering that the increase in thickness is caused by the formation of pores in the phenolic structure with the introduction of ZnCl2, we can easily estimate the porosity of the phenolic membranes by comparing their thicknesses with that of the phenolic structure produced in the absence of ZnCl2.2 dosages lead to larger porosities. Cross-sectional SEM examinations confirm that the phenolic membrane prepared at the molar ratio of 70 exhibits a relatively dense morphology while the membrane prepared at the molar ratio of 280 is highly porous .2. With the fast evaporation of the solvent, the ZnCl2-accelerated thermopolymerization of resol induces the nucleation of phenolics as nanoparticles. They continue to grow until the gelating P123 terminates the supply of resol, thus forming phenolic nanoparticles with increasing sizes from the top to the bottom. These phenolic particles further assemble to form a network with the stabilization effect of P123 and ZnCl2. After removal of P123 and ZnCl2, phenolics with a gradient nanoporous structure are formed. The thus-produced phenolic structures exhibit unprecedented separation performances when used as membranes. They show \u223c20\u201380 times higher water permeance than commercial membranes with similar rejections. Impressively, they also greatly outperform membranes based on expensive 2D materials by a factor of \u223c1.5\u20136 in terms of water permeance while their selectivities being comparable. Furthermore, the phenolic membranes are robust enough to operate in aggressive organic solvents. Such a gradient nanoporous structure combined with excellent chemical and thermal stability makes the thus-produced phenolic superstructures an exciting candidate for applications in other areas including batteries, supercapacitors, catalysis, etc.In summary, gradient nanopores are produced by controlling the thermopolymerization of resol in the mixture of Pluronic polymer (P123) and ZnClThere are no conflicts to declare.Supplementary informationClick here for additional data file."}