Methyl peroxy, a key radical in tropospheric chemistry, was recently shown to react with the hydroxyl radical at an unexpectedly high rate. Here, the molecular reaction mechanisms are elucidated using high-level quantum chemical methodologies and statistical rate theory. Formation of activated methylhydrotrioxide, followed by dissociation into methoxy and hydroperoxy radicals, is found to be the main reaction pathway, whereas methylhydrotrioxide stabilization and methanol formation (from activated and stabilized methylhydrotrioxide) are viable minor channels. Criegee intermediate formation is found to be negligible. Given the theoretical uncertainties, useful constraints on the yields are provided by atmospheric methanol measurements. Using a global chemistry-transport model, we show that the only explanation for the high observed methanol abundances over remote oceans is the title reaction with an overall methanol yield of ∼30%, consistent with the theoretical estimates given their uncertainties. This makes the title reaction a major methanol source (115 Tg per year), comparable to global terrestrial emissions. The high observed abundance of atmospheric methanol over remote oceans is still not well-explained. Here the authors use quantum calculations and atmospheric modelling to show the reaction of methyl peroxy and hydroxyl radicals is a major methanol source (115 Tg/yr), comparable to global terrestrial emissions. Under pristine conditions, CH3O2 reacts chiefly with hydroperoxy radicals HO2 to form methyl hydroperoxide CH3OOH, depleting odd hydrogen radicals (HOx≡OH+HO2) directly and through the further reaction of CH3OOH with OH. The reaction of CH3O2 with organic peroxy radicals (RO2) is only a minor sinket al.Methyl peroxy radical CH3O is the m3O2 with OH was previously considered7et al.−10 cm3 molecule−1 s−1. This unexpectedly high value makes this reaction a major sink of CH3O2 in pristine conditions. Using campaign data in Cape Verde, Fittschen et al.3O2 sink at that remote site, rivalling the reaction with HO2. Its impact on atmospheric chemistry is however critically dependent on the nature and yields of the products. Three exothermic overall reaction channels were envisagedAlthough the possibility of a reaction of CH2O2 the singlet Criegee intermediate, H2C=O(+)−O(−). The Criegee channel (1) has been invoked as the possible source of a missing oxidant of SO2 inferred from observations at a coastal site2O2 with water8142 radicals and formaldehyde, which is the end product of both CH3O2+NO and (through CH3OOH) CH3O2+HO2. The methanol channel (2) was noted to be a potentially very significant source of methanol8with CH3O2+OH by Bian et al.3OOOH (TRIOX), followed by direct dissociation into CH3O and HO2, which are about 4 kcal mol−1 more stable than the reactant radicals. Another recent theoretical study by Nguyen et al.3OOOH, whereas production of Criegee is negligible.A recent quantum chemical study of CHab initio methodologies for the singlet and triplet  intermediates; (ii) identify the kinetically viable reaction channels and distinguish between the major and minor product routes using appropriate statistical rate theories; (iii) use a global chemistry-transport model, the Intermediate Model for the Annual and Global Evolution of Species , to assess the impact of the reaction and constrain the yields through comparisons with atmospheric measurements. For those readers most interested in the implications for atmospheric chemistry, the results relating to goals (i) and (ii) are succinctly summed up before the section on atmospheric modelling, and we invite such readers to move directly to this summary.In view of the likely major importance of the title reaction for key oxygenated organic compounds and its potentially large impact on HOx radicals in the remote troposphere, this work proposes to: (i) elucidate the molecular mechanisms of the reaction by constructing detailed potential energy surfaces, using suitable high-level density functional theory (DFT) and We characterized all three exothermic overall reaction channels (reactions (1), (2), (3)) and all other relevant pathways of the title reaction using quantum chemical methods. Structures and vibrational frequencies were computed with DFT, at the M06-2X-D3/6-311++G level of theory . More ac3OO with OH starts by the barrier-less formation of singlet reactant complex 1RC and triplet reactant complex 3RC, in which OH donates a hydrogen bond to CH3OO, and in which the singlet and triplet states are near degenerate. Hydrogen abstraction starting from 1RC and 3RC to form the Criegee intermediate 1CH2OO and the triplet biradical 3CH2OO via TS2 and TS3, respectively, involve significant barriers. In absence of intersystem crossing (ISC) 3RC→1RC, the reaction CH3O2+OH ↔ 3RC will be quasi-equilibrated such that the bimolecular rate constant for the overall triplet channel CH3O2+OH→3CH2O2+H2O can be found from transition state theory (TST)18193kbi,3(298 K)=2.6 × 10−15 cm3 molecule−1 s−1. This channel is therefore entirely negligible, as are the other triplet entrance routes described by Bian et al.3RC to the nearly-degenerate 1RC could channel much of the triplet entrance flux also towards the singlet surface and hence to TRIOX (see below), rationalizing the high measured overall rate constant−10 cm3 molecule−1 s−1.The reaction of CH1RC is the formation of the stable methylhydrotrioxide TRIOX over the very low-energy TS1. Direct dissociation of TRIOX into CH3O and HO2 is not a minimum energy pathway; instead, the energetically favoured decomposition route passes through the singlet product complex 1PC over TS4, which involves concerted CH3O–OOH bond-breaking and formation of a CH3O–HOO hydrogen bond. The relative energy and vibrational properties of saddle-point TS4 play an important role in determining selectivity, but this point is also very difficult to characterize accurately. As explained below, the best results are obtained by using a structure optimized with the M06-D3 DFT method, rather than M06-2X-D3 as used for the other stationary points. Like the reactant complex, the hydrogen-bonded PC has near-degenerate singlet and triplet states. From 1PC, CH2O+HOOH can be formed through TS5, or CH3OH+1O2 can be obtained through TS7. Equally, 1PC can convert to triplet product complex 3PC, and 3PC can form CH3OH+3O2 through the very low TS6.The favoured reaction channel of the chemically activated TS2, TS3, TS5, TS6 and TS7 corresponding to the abstraction or transfer of a hydrogen atom are straightforward and their identity has been carefully confirmed using intrinsic reaction coordinate (IRC) calculations. The coupled-cluster relative energies agree well with those from DFT, supporting the use of the M06-2X-D3 functional for geometry optimization. However, TS1 and TS4 are more problematic and need further discussion, in particular as these crucial transition states (TSs) largely determine the dominant reactant pathways. Both TSs can be considered to correspond to breaking of one of the O–O bonds in TRIOX. However, this step does not proceed with monotonously increasing energy towards the fragments, due to the existence of the hydrogen-bonded RC and PC. As the relative orientation of the fragments in the complexes differs from that in TRIOX, the TSs have combined O–O bond breaking and fragment reorientation character. Also, TRIOX has a closed-shell singlet electronic structure, with the transition to the open-shell radical pair nature of PC or RC occurring in the region near the TSs. For open-shell singlets with completely uncoupled electrons, singlet and triplet states are near-degenerate (as in RC and PC). Unrestricted DFT calculations and coupled-cluster calculations based on unrestricted Hartree-Fock reference wavefunctions are reasonably accurate in this case. However, for partially uncoupled electrons, the triplet is significantly higher in energy, and unrestricted approaches are less accurate, introducing artefacts in the shape of the energy curve. For TS1, we are able to locate two saddle points, TS1 and TS1′, with the M06-2X-D3 functional. The first one corresponds mostly to reorientation of the OH fragment, while TS1′ has essentially only O–O bond stretching character. Large-active-space CASSCF (complete active space self-consistent field) and CASPT2 (complete active space perturbation theory 2) calculations  whereas the M06-D3 TS4 has an O–O distance of 2.447 Å. Accordingly, we have used the TS4 structure in this study. For the other stationary points, the CCSD(T)-F12  total energies at the M06-D3 and M06-2X-D3 structures differ by <0.2 kcal mol−1, and the vibrational frequencies are very similar also.For 1RC, with average vibrational energy <Ev>=4.8 kcal mol−1, including an average 2.1 kcal mol−1 thermal energy at 298 K inherited from the reactants (see the ‘Methods section'), reacts nearly barrier-free (TS1) to form the closed-shell CH3OOOH molecule, TRIOX, much faster than forming Criegee 1CH2O2 and H2O over a barrier of 3.7 kcal mol−1 (TS2). The RRKM-based 21F (see the ‘Methods section') are <k1>=1.8 × 1013 s−1 and <k2>=3.4 × 1010 s−1, respectively. The k-subscripts refer to the TS numbering in F-averaged rate coefficients of the activated reaction steps given in this subsection are for 298 K and 1,013 hPa (air). They are listed also in 1CH2O2+H2O theoretically characterized by Bian et al.et al.−1 above the initial reactants, it is clear that Criegee formation contributes not more than ∼1% overall.The chemically activated singlet reactant complex TRIOX, with average chemical activation energy <Ev> of 31.1 kcal mol−1 (at 298 K) converts rapidly to the product complex 1PC over the low-lying and very loose TS4, characterized above, far outrunning the other isomerization/decomposition reactions through high-lying transition statesF is evaluated at <k4>=2.4 × 1010 s−1, implying a TRIOX lifetime of ∼40 ps during which it should lose ∼0.45 kcal mol−1 by collisions at 298 K and 1,013 hPa (see below), shifting down also the energy distribution F for 1PC. The CH3O·HO2 complex 1PC has a decisive role in our system; the ∼7 kcal mol−1 strong CH3O–HOO hydrogen bond explains why the minimum energy pathway of CH3OOOH to CH3O+HO2 passes through it. The fastest reaction of 1PC, with <Ev>(1PC)≈12.4 kcal mol−1, is dissociation into these radicals by breaking the H-bond without exit barrier. The F- averaged <kdiss> was estimated by variational RRKM21Gvar(Ev—Evar) were computed for a series of structures with increasing H-bond length, using the unprojected vibrational frequencies, as listed in 2324kdiss> and <3kdiss>, with a minor effect on the overall product yields (see Gvar(Ev—Evar), shown in −1 below the separated CH3O+HO2, giving <kdiss>≈2.4 × 1012 s−1.elds see . The var1PC into CH2O+H2O2 over the fairly high TS5, with RRKM-calculated rate of only <k5>=9.7 × 109 s−1 is negligibly slow, whereas decomposition into CH3OH+O2(1Δ) over TS7, at averaged rate <k7>=1.2 × 1011 s−1, is a channel of atmospheric relevance. Importantly, conversion of the initially formed 1PC to 3PC will affect the relative yields of the different products. Spin–orbit coupling between the lowest singlet and triplet states in PC is very small, but the spin–orbit coupling between the lowest singlet state and the second-lowest triplet state (or between the second-lowest singlet and the lowest triplet) is much larger, as there is now an orbital angular momentum difference, and we calculate a root-mean-square coupling matrix element of 58 cm−1 in both cases. Simply assuming Rabi cycling between the two states, a ‘rate constant' for singlet-triplet conversion of 1.7 × 1012 s−1 is estimated. Using a more rigorous statistical rate theory for reactions with spin-state change26kISC>=3.5 × 1012 s−1, while the reverse <k−ISC>=1.9 × 1012 s−1. The reverse reaction 1PC→TRIOX occurs with an average rate <k−4> of 1.3 × 1011 s−1, which is ∼3% of the total 1PC removal rate, such that the net TRIOX→1PC conversion rate k4n(Ev)=0.97 × k4(Ev).The decomposition of 3PC decomposes into CH3OH and ground state 3O2 over a very low barrier (TS6), with RRKM-calculated average <3k6> of 4.1 × 1011 s−1, faster than the singlet 1PC reaction to CH3OH, above. It must compete with the reverse ISC, above and also with the fast dissociation of 3PC into CH3O+HO2 at variational-RRKM rate <3kdiss>≈3.4 × 1012 s−1  transition states of the PC dissociations, and taking into account also a likely error of a factor of ∼2 on the ratio of kISC/kdiss, we estimate an uncertainty margin on the CH3OH yield of a factor of ∼3.5. Note that about 45% of the products of activated TRIOX arise via ISC of 1PC to 3PC. Of major importance is that TRIOX does not decompose directly but via the complex 1PC, which enables production of CH3OH, while direct methanol formation from CH3OOOH would face a quasi-unsurmountable barrierTRIOX will suffer energy loss by successive collisions with air molecules to yield thermalized CH3OOOH, of which the subsequent fates are discussed in E>all of −0.9 kcal mol−1—fairly high because TRIOX has several low-frequency vibration modes—and taking into account the distribution function F of the activated TRIOX, the fraction of stabilization at a collision frequency of 1.2 × 1010 s−1 at 298 K and 1,013 hPa was evaluated (see the ‘Methods section') to be fstab≈10.7%. However, this result is quite uncertain, first of all because it is very sensitive to the assumed value of <ΔE>all: doubling it increases fstab nearly threefold while halving it reduces fstab to <2%. Moreover, the calculated fstab depends also strongly on k4(Ev), which itself bears a possible error of a factor ∼1.5–2. We therefore estimate a stabilized CH3OOOH yield at 298 K and 1 atm in the range 0–35%. The much higher fstab of ∼90% predicted by Nguyen et al.TRIOX→1PC conversion being our artefactual TS4′, which on account of its far higher rigidity than TS4 leads to a much lower calculated rate of TRIOX→1PC and hence much more TRIOX stabilization.A (minor) fraction of the activated 3O+HO2, whereas the suggested channel (1)82O2 is found to be entirely negligible. On the other hand, we find that the title reaction yields a sizable fraction of collisionally thermalized  CH3OOOH, of order of 10% at 1 atm and 298 K, while we also uncovered two parallel pathways leading directly to CH3OH+O2 with overall yield around 7% in the same conditions. No evidence could be found for any other significant product routes. It must be stressed that the yield estimates of CH3OOOH and CH3OH given above and listed in The theoretical investigation above predicts that the dominant product route of the title reaction is channel (2) yielding the radicals CH3OOOH stabilization fraction should show a considerable pressure and temperature dependence, and a minor temperature dependence is also expected for other pathways (see the ‘Methods section') we have evaluated the CH3OOOH and CH3OH yields also for the ‘median' conditions 750 hPa and 285 K, and for the ‘limit' conditions 400 hPa and 256 K, above. The results, together with those for 1,013 hPa and 298 K, are listed in 3OOOH stabilization fraction can be expressed within a few per cent by the power function fstab=0.107 × 2.0 × (298 K/T)5.0.As detailed in the next subsection, the title reaction is most important above the tropical oceans, where NO levels are low but OH concentrations moderate to high. The rate of the reaction as a function of decreasing pressure  and as a function of latitude is depicted in 3O2+OH, the reaction accounts for 20% of the global CH3O2 sink according to IMAGES simulations. The global flux through that reaction is considerable: ∼11 Tmoles per year, comparable to, for example, the global source of isoprene3O2 at high latitudes and over polluted continental regions .Adopting the measured rate regions  where th regions , the rea3OH yield and the TRIOX stabilization fraction. Relative to a simulation neglecting the title reaction, the HO2 radical abundances are increased by 10–20% over tropical oceans (2 yield is highest (run D). The changes are negligible or even negative in high-NOx areas.l oceans . Unsurpr2, reaching up to −7% over remote oceans. Loss of OH due to reaction with CH3O2 and the products CH3OOH and CH3OH is partially offset by OH recycled from enhanced HO2. The globally averaged OH concentration decreases by 1.5–3.2% depending on the simulation, increasing the methane lifetime by up to 0.3 years in run C. The largest OH changes are calculated in run C, due to its lower HO2 yield and higher OH loss through reaction with CH3OOOH and CH3OH. Surface ozone is decreased due to the CH3O2+OH reaction, by up to 6% over remote oceans, and by 1–2% (<1 ppbv) over Europe, North America and East Asia in July (2O2) is strongly impacted, owing to the quadratic dependence of its production on HO2 levels. Its concentrations increase by up to 30% in run C . Formaldehyde is almost unaffected, being an end product to all CH3O2 sink pathways. Methanol, however, shows drastic differences among the simulations: whereas its concentrations increase or decrease by ∼20% at most in runs B and D, the global methanol burden is increased by 60% in run C, with concentration increases reaching 30–100% over remote oceans (3O2+OH is largely due to the direct pathway to CH3OH+O2 (56%), but indirect formation through stabilized TRIOX is significant (44%). Reaction on aerosols is calculated to be the largest TRIOX sink globally, followed by reaction with OH and reaction with (H2O)2 2 . The cal2O2 agree generally fairly well with the observations from aircraft and ship campaigns  of airborne measurements, but it improves significantly the model agreement with ship measurements , while it nearly vanishes in run C, with an overall yield of 32%. Both the average concentration and vertical profile shape are greatly improved in this case.In agreement with previous studies4534 Pacific . When inper year  due to i3O2+OH. Nevertheless, including the reaction improves the model performance against airborne measurement at mid-latitudes (−1) close to the corresponding model value (0.63 cm s−1). Suppressing oceanic emissions in the model (run C_NO) leads to a much closer agreement with the latitudinal profile of AMT-22 data. That this setting leads however to large underestimations at other sites  is negligible in atmospheric conditions, that is, CH Pacific  where me3OOOH intermediate decomposes indirectly through the CH3O·HO2 complex. The share of each of the two minor channels likely does not exceed ∼20% of the total reaction rate. Theory alone cannot provide precise yield estimates, due to uncertainties in key parameters, that is, precise barrier heights, average energy losses per collision, and the singlet ↔ triplet ISC rate that impacts methanol production.The theoretical calculations further inform us that the methoxy pathway (2) is expected to dominate, whereas both methanol formation (3) and stabilization of the trioxide are viable, but likely minor. Of fundamental interest is that significant direct methanol production can occur only because the activated CH3OH measurements over the remote Pacific45343O2+RO2 reactions, could be underestimated. But since it is largely dominated by the CH3O2 self-reaction of which the methanol yield (∼0.63) cannot be much underestimated, and since CH3O2 production from CH4+OH is also well constrained, only a large production of organic peroxy radicals from non-methane organic precursors could boost this source of methanol. High observed acetaldehyde over oceans363CHO or of its precursors. However, besides the noted inconsistency2O with observations over oceans  in the total rate constant of the reactionet al.3O2+OH  is comparable in magnitude to the total terrestrial emission source. Further work will be needed to evaluate how this source will impact our understanding of the methanol budget. Clearly, a better understanding of ocean-atmosphere exchanges is required to refine the top–down yield estimation presented above. It is not currently possible to determine which of the direct methanol formation channel or indirect pathway through the stabilised TRIOX is dominant. A more direct experimental determination is obviously needed. Hopefully TRIOX can be measured, although loss to walls might prove challenging, and atmospheric concentrations should be very low, a few pptv at most.The only viable candidate for the missing remote source of methanol is therefore CH†, conversion to a complex RO—HO2 and eventual dissociation to RO+HO2 will be substantially slower than for CH3OOOH†, such that collisional stabilisation of ROOOH† should be a major if not dominant product route. However, the global relevance for large peroxys formed from biogenic terpenoids is expected to be lower compared with CH3O2+OH, because OH levels are generally lower in the boundary layer over forests than in the oceanic lower troposphere, and because the reaction of HO2 with large peroxys is considerably faster than the reaction of CH3O2 with HO2  level of theory in Gaussian 09 version D.01 ref. , except oose TSs .Various single-point calculations were carried out using CASSCF, CASPT2 and CCSD(T)-F12. The CASSCF and CASPT2 calculations were performed with Molpro 2012.1 refs , 44 withExplicitly correlated CCSD(T)-F12 energies were obtained with the ORCA 3.03 packageThe statistical-kinetics rates for thermal as well as chemically activated reactions were estimated using the energies obtained at our highest level and including the ZPVE  as statAs detailed in the Results section, the only thermal bimolecular reaction that needs to be considered was found to be unimportant if not negligible. Its thermal rate coefficient at 298 K was computed using conventional transition state theory491RC, (ii) the closed-shell singlet intermediate TRIOX and (iii) the resulting product complexes 1PC and 3PC. We employed RRKM theory21The majority of the relevant reaction steps are chemically activated unimolecular reactions of (i) the initial singlet reactant complex α is the reaction path degeneracy, h Planck's constant, E≠ the TS energy, Ev the vibration energy of the reacting activated intermediate, N(Ev) its density of vibration states and G≠(Ev−E≠) the sum of accessible vibration states of the TS; both the latter were evaluated by exact count1RC, adopting the quasi-diatom approximation . Tunnelling corrections for all relevant activated reactions were found negligible because of the relatively high excess vibration energies (Ev–E≠) and low imaginary frequencies . The rate constant for ISC of 1PC to 3PC was calculated based on locating the minimum energy crossing point using the code developed by Harvey and Aschi51in which tion see . The chacies see . The ratEv, we duly include the thermal vibration energy Eth,v that the intermediates inherit from the thermal reactants CH3O2+OH, and for each step the rates k(Ev) were averaged over the thermal distribution function F of formation. As the lifetime of the initial complex 1RC is <1 ps, the original thermal distribution F remains conserved up to the TRIOX intermediate, but it shifts down for 1PC and 3PC by ∼0.45 kcal mol−1 at 298 K/1,013 hPa, ∼0.35 kcal mol−1 at 285 K/750 hPa and ∼0.25 kcal mol−1 at 256 K/400 hPa, respectively, due to the average of ∼0.5, 0.4 and 0.3 collisions, respectively, that TRIOX suffers in the atmosphere during its lifetime , of ∼2 kcal mol−1, is much less than the average excess energy (Ev−E≠) for most reaction steps, and the k(Ev) are generally not far from their high-energy asymptotes, such that the F-averaged <k(Ev)> differ only 1–20% from k(<Ev>). The only exception is the 1PC reaction through TS2, which anyway is negligibly slow compared with the competing reaction through TS1. As a result, the precise shape of F is of little importance for the overall kinetics of the chemically activated unimolecular reactions of our system, though the average value of the thermal <Eth,v> is of some significance. As there is no entrance barrier and the entrance transition state TSin is variational  cannot be evaluated in the usual wayEth,v>, of ∼2.1, 2.0 and 1.75 kcal mol−1 at 298, 285 and 256 K, respectively, could be estimated with sufficient accuracy for our purpose and a reasonable F could be derived accordingly as detailed in In the total distributable energy onal see , the forfstab of the activated TRIOX that becomes collisionally stabilized depends markedly on the vibration energy of the activated TRIOX and is therefore quite sensitive to F. The stabilization competes with the much faster rearrangement TRIOX→1PC through TS4 at net rate kn4(Ev) (≈0.97 × k4(Ev) due to the reverse reaction). The Lennard-Jones collision frequency of CH3OOOH with air molecules, kcoll=ZLJ[M], is estimated10 s−1 at 298 K/1,013 hPa, 285 K/750 hPa and 256 K/400 hPa, respectively. The bi-exponential energy transfer model of Troefstab but highly uncertain, was assumed to be <ΔE>all=−0.9 kcal mol−1, amounting at 298 K to an average energy lost per down-collision α≈1.34 kcal mol−1 and average energy gained per up-collision β≈0.44 . For a given initial energy Ev,in of TRIOX, the stabilization fraction was found as the repetitive product of the successive, increasing probabilities of a (new) jth collision at constant rate kcoll in competition with TRIOX→1PC rearrangement at net rate kn4(Ej−1) that decreases on average after each collision:Different from the effective rates of the unimolecular reactions, the (minor) fraction TS4 of ∼7 kcal mol−1, this product converges rapidly after some 8–10 collisions for the adopted <ΔE>all. The overall fstab was finally found by integrating over the distribution function F. As the net TRIOX conversion rate kn4(Ev) at the initial energies is relatively high, fstab is small and depends strongly on <ΔE>all but also markedly on kn4(Ev) itself. Obviously, at higher altitudes in the troposphere, fstab decreases with decreasing pressures, but this is partially offset by the pronounced, multiple effect of the simultaneous temperature decrease: through the lower kn4(Ev), the lower average Eth,v to be lost for stabilization, the effect on the number density of N2/O2 and the higher Ω2,2 collision integral. Thus, the combined effects of the decreasing pressure P and temperature T in the troposphere above tropical oceans result in a dependence fstab∼P2 × T−5.Given the initial excess energy of Overall and net reaction rates and end-product yields were obtained in a straightforward way by duly considering the fractional contribution of each competing reaction for each intermediate in the complete scheme.www.globalfiredata.org). Isoprene fluxes are based on the Model of Emissions of Gases and Aerosols from Nature (MEGAN)5961et al.2O2 surface resistance becomes negligible after this adjustment.IMAGES541PC; reaction with OH; reaction with the water dimer; and reactive uptake on aqueous aerosols. Aerosol uptake is calculatedAs detailed in The authors declare that the data supporting the findings of this study are available within the article and its How to cite this article: Müller, J.-F. et al. The reaction of methyl peroxy and hydroxyl radicals as a major source of atmospheric methanol. Nat. Commun.7, 13213 doi: 10.1038/ncomms13213 (2016).Supplementary Figures 1-18, Supplementary Tables 1-7, Supplementary Notes 1-6 and Supplementary References


Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature TC is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO6 sample as a function of the magnetic applied field, the associated magnetic entropy change |−ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of TC, |−ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg−1 K−1. Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A2FeMoO6  double-perovskite system.Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO Their properties include colossal magnetoresistance [Perovskite and double-perovskites oxides with general formula ABOsistance –7, largesistance –12, multsistance , magnetosistance ,15 and lsistance . In doubsistance .et al. [2B′B′′O6. The most ordered double perovskite studied to date is Sr2FeMoO6 [6 and MoO6 octahedra are alternately ordered in a rock-salt lattice and the angle of the Fe–O–Mo chain is nearly 180°. This oxide is a half metal and shows a ferrimagnetic ordering behaviour at low temperature with a high ordering temperature TC ∼ 420 K, in which spins at the Fe3+(3d5) and Mo5+(4d1) ions are aligned in the opposite direction. However, this homologous manganese double-perovskite Sr2MnMoO6 with Mn2+(3d5) and Mo6+(4d0) ions has been known to be either a paramagnetic (PM) or antiferromagnetic insulator [2(Fe/Mn)MoO6. The same result has been observed recently in an NaLaB′B′′O6  double-perovskite system [2B′B′′O6  would be a good reference to those NaLaB′B′′O6 compounds, and indeed, in other words, the short-range order of Na and La in A site has no/slight effect on the magnetism, in comparison to the perovskites with Ca and Sr in the A site.Recently, Kobayashi et al.  reportedr2FeMoO6 –23. It insulator . Hence, e system . The mag6 opens the door to the design of magnetic materials with novel topologies. Furthermore, compounds with this ordered double-perovskite-type show the potential for multiferroic behaviour. However, few of the compounds reported in the literature have not been thoroughly examined, and it was partially the purpose of this work to find a novel compound with useful properties.The availability of four distinct cation sites in A′A′′B′B′′O6 family, the LaNaMnMoO6 double-perovskite oxide. Then we report a giant magnetoresistance and moderate MCE over a broad temperature range.In the present work, we have prepared, to our knowledge for the first time, and characterized a new member of the Mn-based materials A′A′′MnMoO2.6 were prepared using the standard ceramic processing technique by mixing La2O3, Na2CO3, MnO2 and MoO3 up to 99.9% purity in the desired proportion according to the following reaction:Powder samples of LaNaMnMoOPhase purity, homogeneity and cell dimensions were determined by powder X-ray diffraction  at room temperature using Fe radiation. The structure refinement was carried out using the Rietveld technique . The ene3.3.1.6 sample is single phase. No impurity has been detected. Structure refinements using the Rietveld method have been achieved with the Fullprof program [Figure 1a shows the XRD patterns  at room temperature for LaNaMnMoO6. A good fit between the observed and the calculated profiles was obtained (as indicated in figure 1b). All the peaks are indexed in the orthorhombic system with Pnma space group. The structural parameters obtained from the Rietveld refinement of the XRD pattern at room temperature and the selected bond distances with angles of the LaNaMnMoO6 sample are listed in tables ap × 2ap × √2ap, where ap is the unit cell parameter of the parent perovskite aristotype. The same symmetry and the same order of magnitude for the volume of the elementary cell were obtained for its homologous oxides LaNaB′B′′O6  by Dachraoui et al. [6 structure is because of the cooperative coupling of the MnO6 and MoO6 Jahn–Teller distorted octahedral B sites.Powder XRD patterns indicate that our synthesized LaNaMnMoO program . Figure i et al. . Moreovec shows the orthorhombic structure of LaNaMnMoO6 projected along the (101) direction, where the (Mn/Mo)O6 octahedra are apparent. A typical feature of the crystal structure of these double-perovskite oxides is the presence of a superlattice owing to the ordered arrangement of the cations in the oxygen octahedral nodes (B sites). The superlattice formation owing to displacement of the anions from their ideal sites may be also considered as another cause.Figure 16 ceramic is presented in figure 1d. A larger grain (≈3.5 µm) with well-defined boundaries, which coexist with smaller ones, was noted for the LaNaMnMoO6 ceramic. The average crystallite size can be evaluated from the width of diffraction peaks using Scherrer formula [K is the grain shape factor, λ is the X-ray wave length, and θ and β are the Bragg angle and the width at half maximum of the XRD peak, respectively. The CXRD of LaNaMnMoO6 powder is found to be 41.57 nm. Obviously, the grain sizes observed by SEM are several times larger than those calculated by XRD, which indicates that each grain observed by SEM is composed of several crystallites.The SEM image of the LaNaMnMoO formula :3.1CXRDt of the single perovskite [2B′B′′O6, the tolerance factor can be written as [rA, rB and rO are the average ionic radii of the A site, B site and oxygen, respectively. The closer to t = 1, the more the structure corresponds to ideal cubic. Therefore, except in rare cases, one can consider the following rule for the double-perovskite family: for 1.05 > t > 1.00, a cubic structure is adopted within the space group; for 1.00 > t > 0.97, the most likely structure corresponds to the I 4/m tetragonal space group and if t < 0.97, the compound becomes either monoclinic (P21/n) or orthorhombic [6 and of its homologous double-perovskite oxide LaNaB′B′′O6/A2MnMoO6 with different symmetry. These values are in good agreement with those mentioned below. Our crystallographic data were used to also calculate this tolerance factor for LaNaMnMoO6 such asThe ideal structure of the double perovskites is based on the adapted tolerance factor rovskite . In geneitten as  follows:orhombic . Table 3This factor is 0.956 which is close to the Goldschmidt one (equation (3.2)).3.2.6 compound exhibits an FM behaviour at low temperature. The Curie temperature TC is 180 K [6 sample are plotted in 6 exhibits a PM to FM transition at TC = 320 K with decreasing temperature. TC has been determined from the peak position of the dM/dT curve, as shown in 6 compound at low temperature; however, it induces an increase in the Curie temperature TC from 180 K for LaKMnMoO6 to 320 K for LaNaMnMoO6. This result can be explained by the decrease of the average ionic radius 6 double-perovskite samples and/or the distortion of the octahedral MnO6 and MoO6 as observed in the Pr0.7Ba0.3−xMnO3 perovskite sample [TC = 180 K for the LaKMnMoO6 double-perovskite sample to 1.375 Å with TC = 320 K for LaNaMnMoO6.A previous study shows that LaKMnMoOis 180 K . Magnetie sample . The FM 2MnMoO6 sample [Our oxide is FM at low temperature. Such FM behaviour has not been observed in this homologous Sr6 sample .6 was modelled using a phenomenological model given by Hamad [Mi/Mf is an initial/final value of magnetization at an FM–PM transition;— B is the magnetization sensitivity dM/dt at FM state before transition;— A = 2*(B − SC)/(Mi − Mf);— SC is the magnetization sensitivity dM/dT at Curie temperature TC; and— C = (Mi − Mf)/2 − B*TC.— FM–PM transition of LaNaMnMoOby Hamad . The depM(T) measurements of our powder LaNaMnMoO6 by the expression (3.4) based on this phenomenological model shows a good concordance between theoretical and experimental study  curves for LaNaMnMoO6 compound. The magnetization rises sharply for low magnetic applied field and then saturates for µ0H higher than 1 T. The saturation magnetization at 10 K and 5 T, deduced from the M (μ0H) curve, is 2.1 µB/mole. The LaNaMnMoO6 compound reaches approximately 50% of the theoretical saturation of Mn3+ (4 µB for S = 2).In order to confirm the FM behaviour at low temperatures of our sample, we performed magnetization versus magnetic applied field up to 8 T at several temperatures. We plot in M (μ0H) curves can be simulated by the law-approach to saturation n) indicates the deviation of magnetization from saturation and the factor n changes with respect to the origin of deviation. The a-factor correlates with the FM correlation length. The values of a, n and Ms are given in n factor and the small a factor for the compound should be associated with the long-range spin order of magnetic moment.The turation  in the tM2 versus μ0H/M for the LaNaMnMoO6 sample. All the M2 versus μ0H/M curves clearly show a positive slope for the complete temperature range, which means that a second-order FM to PM phase transition occurs  curve (TC = 320 K).We report in Banerjee ). The TCa shows the temperature dependence of the spontaneous magnetization and the inverse of the magnetic susceptibility evolution versus temperature for LaNaMnMoO6 compound.Figure 7We have simulated our experimental measurements of spontaneous magnetization and the inverse of susceptibility versus temperature by theoretical expression based on Bloch's Law and Curie Weiss Law, respectively. We have obtained a best fit between experimental and theoretical study. Parameters fit are listed in The effective magnetic moment (fexp)2/8 .C) parameter, we have deduced the experimental effective moment: 3+ (3d4) and Mo5+ (4d1) ions contribute to the PM behaviour and the effective magnetic moment of the compounds, (From the determined (β is obtained from fitting Ln(Msp) versus Ln((TC − T)/TC) plot to a be straight line (b). Similarly, Ln (1/χ) versus Ln ((T − TC)/TC) plot allows the determination of ϒ (c). The β and ϒ values are 0.237(2) and 0.850(2), respectively. Using these critical exponents, we have represented the modified Arrott plots for LaNaMnMoO6 compound, as shown in figure 8a. These values are close to those expected for the tricritical mean-field theory model  [δ exponent can be determined by fitting the Ln–Ln plot of M (μ0H) curve at TC . The determined value of δ = 3.61 for the LaNaMnMoO6 sample is smaller than is calculated from the Widom relation [δ = 1 + (ϒ/β) = 4.586; this difference is related to the existence of the magnetic inhomogeneity (Griffiths Clusters) in the vicinity of the transition temperature.The calculated value of the critical exponent ght line b. Similaion of ϒ c. The β , ϒ = 1) . Moreoverelation : δ = 1 +3.3.iM and iM+1 are the experimental values of the magnetization measured at temperatures iT and iT+1, respectively, under an applied magnetic field H. The magnetic entropy change can be measured through either the adiabatic change of temperature by the application of a magnetic field, or through the measurements of classical M(H) isotherms at different temperatures [Figure 9a shows the behaviour of the magnetic entropy change as a function of temperature under several values of external magnetic field for our double-perovskite sample.A giant field-induced entropy change is one of the important criteria for magnetocaloric materials. In fact, the isothermal measurements of magnetization allow us to determine the magnetic entropy change of the sample under an applied magnetic field, according to the classical thermodynamic theory based on Maxwell's relations using the following equation:eratures . In our Hmax is available byAccording to the phenomenological model , the magSM) depending on the temperature of our sample (b). The theoretical and experimental results are illustrated in Using the above equation, we numerically calculated the variation of the magnetic entropy  for ΔH = 2 T [6 sample can be considered as a potential candidate for magnetic refrigeration.Under an applied magnetic field of 2 T, the absolute value of ΔΔH = 2 T  considerδFWHM is full width at half maximum of ΔS(T) curve [-1 under an applied magnetic field of 8 T. These results are interesting, compared with those of materials considered as good for applications in magnetic refrigerators. Our sample undergoes a large MCE above room temperature.In order to confirm the important MCE of our specimens, it is interesting to consider the relative cooling power (RCP) which can be determined from the following relation:T) curve . The RCPn depends on the magnetic state of the sample and it is obtained from the fit plot of µ0H via equation (3.8)  (inset of n = 0.29(8)). This difference shows the signature of magnetic inhomogeneities in our sample.The magnetic field dependence of the magnetic entropy change of materials with a second-order phase transition can be expressed as :3.10ΔSMon (3.8) . The valinset of . This va+β−1β+γ,  below:6 sample are shown in Figure 11b, a good agreement is observed between experiment and calculation, showing the ability of the phenomenological model in the ordered double-perovskite single-crystal LaNaMnMoO6, particularly for low magnetic fields.Based on figure 113.4.ρ(T) without and for an applied magnetic field of 3 T and 6 T are plotted in 6 powder attains 1533 Ω cm at 70 K. Then it passes a maximum at ρT = 180 K and drops down to 1018.93 Ω cm at room temperature. The magnitude of resistivity is markedly higher than found for Ba2YIrO6 single crystal (ρ (300 K) = 40 mΩ cm) [The temperature dependence of the resistivity 0 mΩ cm) .Figure T < ρT), whereas his homologous Sr2MnMoO6 sample is an insulator [For comparison, our compound shows that it is metallic at low temperatures (nsulator .ρT = 180 K) and magnetic (TC = 320 K) transition temperature values. The significant difference between ρT and TC values may be owing to several factors: (i) smaller crystallite size of sample than that measured using XRD, (ii) influence of extrinsic contributions such as a large number of grain boundaries, and (iii) spin-polarized tunnelling between FM grains through an insulating grain boundary layer, and so on. The discrepancy of the grain size may be that the size measured using SEM is for grains consisting of more than one crystallite [It should be noted here that there is a large difference between the electric ; f) is the volume concentration of the PM phase.Based on the phase segregation mechanism (percolation model), the total resistance of the system could be visualized as the sum of the resistivity of the phase separated FM–metallic and PM-insulator: 6, we have fitted the experimental resistivity data (f is shown in f (T) remains equal to 1 below the metal–semiconductor transition temperature, which confirms the strong dominance of the FM fraction in this range.In order to see the correlation between the magnetic and electrical properties in our sample LaNaMnMoOity data  using thρ/ρ = ((ρ(0) − ρ(H))/ρ(0))*100; where ρ(H) and ρ(0) are the resistivity in a magnetic applied field H and in a zero field, respectively. The magnetoresistance evolution versus temperature at the applied magnetic field (6 T) is illustrated in 6 double-perovskite sample. It is found to be approximately 30% at room temperature and approximately 50% at 70 K at 6 T for our synthesized sample. We thus obtain a large magnetoresistance in the LaNaMnMoO6 sample as that observed in the Sr2FeMoO6 compound by Yuan et al. [2FeMoO6 compound by Kobayashi et al. [The coexistence of ferromagnetism and metallic conductivity at low temperatures provides evidence of the existence of magnetoresistance MR. Defining the MR at a given temperature as MR = Δn et al. . This rei et al. .Figure 4.6 double-perovskite sample. Structure analysis reveals that our sample crystallizes according to the orthorhombic structure with Pnma space group. Magnetic measurements show a PM–FM transition with decreasing temperature. This new double perovskite exhibits an MCE and a large magnetoresistance near room temperature. A combination of both MCE and large MR in LaNaMnMoO6 material makes the appropriate substance for magnetic refrigeration applications at room temperature.We have investigated structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO


Histone lysine demethylases (KDMs) are of critical importance in the epigenetic regulation of gene expression, yet there are few selective, cell‐permeable inhibitors or suitable tool compounds for these enzymes. We describe the discovery of a new class of inhibitor that is highly potent towards the histone lysine demethylases KDM2A/7A. A modular synthetic approach was used to explore the chemical space and accelerate the investigation of key structure–activity relationships, leading to the development of a small molecule with around 75‐fold selectivity towards KDM2A/7A versus other KDMs, as well as cellular activity at low micromolar concentrations. Chemical modifications of DNA and its associated histones regulate gene expression across the entire genome, and therefore have a profound impact on a number of fundamental biological processes.II ion in the active site and require a 2‐oxoglutarate (2‐OG) cofactor for demethylation in the catalytic JmjC domain.The majority of KDMs belong to the Jumonji C (JmjC) family of enzymes, which contain a catalytically‐active FeKDM2A catalyses the demethylation of mono‐ and dimethylated lysine 36 on histone H3 (H3K36).1, which was prepared as a putative methyllysine binding domain inhibitor,1 was shown to be critical for potency, which we postulated was due to its role as a H3K36me2 mimic. Preliminary docking studies of 1 with KDM2A  indicated a potential for occupancy of the peptide binding site on the enzyme. Based on this initial model, we subsequently hypothesized that inhibitory activity towards KDM2A might be improved by replacing the original indole scaffold with a saturated indoline ring system. We envisioned an exploration of three‐dimensional chemical space around this core, with the aim of augmenting selectivity through increasing complexity.To identify a starting point, a library of known binders to methyllysine reader domains and histone methyl transferases was screened for inhibitory activity against a panel of KDMs, since we reasoned that such a specialized library would be more likely to contain molecules that also interact with demethylases. Compound endo‐trig cyclization of a C‐2‐substituted aromatic imine afforded the racemic indoline core with two adjacent stereocenters. Subsequent acylation of the indoline ring system conferred stability towards oxidation and provided a handle for modulating polarity. Finally, metal‐catalysed cross‐coupling of the aryl bromide provided access to a variety of linkers between the indoline core and pyrrolidine capping group. In total, 45 racemic compounds were synthesized, and IC50 values for inhibition of KDM2A were determined using two orthogonal enzyme activity assays: AlphaScreen2–12). We examined different linkers and found that triazole (2), ether (3), and alkyne (4) linkers were well tolerated, with significantly lower IC50 values than the original hit. Reduction of the alkyne functional group in 4 to an alkene (5) or an alkane (6) also improved potency. Molecules containing a pyridine ring at the indoline C‐2 position were marginally more active than analogues bearing other aromatic groups such as furan (7 or 8) and significantly more active than a substituted benzene (9). In addition, pyridine‐containing compounds displayed the highest selectivity towards KDM2A (Section S3.1). Exploration of substituents at the all‐carbon quaternary stereocenter as in 10 and 11 demonstrated that a Ph,CN combination gave rise to the most potent series of compounds. Unfortunately, 12, the most potent inhibitor identified, was found to be reactive in aqueous solution due to the susceptibility of the α‐aminoacetyl group to hydrolysis. However, the N‐acetyl group present in compounds 2–10 proved inert to hydrolytic cleavage. The optimal length of the linker connecting the indoline core to the pyrrolidine capping group was found to be 7–8 atoms, and replacing pyrrolidine with other secondary amines or a cyclopentyl ring led to a significant drop in potency (Section S3.1).A base‐mediated 5‐3 and 6 using a counterion‐mediated strategy ‐15 as the major product (10:1 d.r.) with 88:12 e.r. The OBn substituent on the pyridine ring was found to be crucial for attaining good levels of stereoselectivity. Pseudoenantiomeric ammonium salt 16 afforded ‐15 as the major product (7:1 d.r.) with acceptable e.r. (17:83). Enantiopurity was subsequently augmented (to >99:1 e.r.) by preparative HPLC. N‐Acetylation and hydrogenolysis of the benzyl group afforded common intermediate 17, which could be converted into ‐ and ‐3 through alkylation with 1,7‐dibromoheptane and subsequent treatment with pyrrolidine. Alternatively, ‐ and ‐6 could be synthesized through O‐triflation, Sonogashira coupling (with 1‐(6‐heptyn)‐pyrrolidine), and reduction of the resulting alkyne.Having succeeded in augmenting the potency of our initial hit compound, we focused on the development of enantioselective syntheses of y Scheme  C.27 CycS,S) enantiomers of 3 and 6 were found to be slightly more potent than their respective  analogues, and ‐6 (IC50: 0.16 μm) was assessed further in a variety of biological assays. In immunofluorescence assays using HeLa cells ectopically expressing catalytically active KDM2A, a dose‐dependent increase in H3K36me2 staining was observed upon incubation with ‐6, reflecting augmented cellular H3K36me2 levels , and ‐6 showed a similar effect on the viability of human fibroblasts  to GSK‐J4, a well‐characterized chemical probe for KDM5/6S,S)‐6 was tested for inhibitory activity against a panel of KDMs, methyllysine binding motifs, and epigenetic enzymes. It was found to be remarkably selective towards KDM2A (≥100‐fold) relative to representatives of the other KDM sub‐families, except closely related KDM7A (H3K9/K27me2/me1 demethylase),S,S)‐6 was inactive towards a representative panel of methyllysine binding domains, methyl transferases, and histone acetyl transferases (Section S3.2). To our knowledge, this is the first time a KDM2A/7A‐selective small molecule has been shown to inhibit demethylation in cells, with a significant reduction in demethylation achievable at low μm concentrations. To explore its cellular activity further, the effect of ‐6 on gene expression in HAP1 cells was monitored using a highly multiplexed 3′ mRNA sequencing method.S,S)‐6 and the less active close analogue 18 ‐6 had a significant effect on expression levels ‐6 and 18 is depicted in Figure When dosed at a concentration of 10 μS,S)‐6 bound to KDM2A proved challenging, and hence, non‐denaturing mass spectrometry (MS) experiments were performed to determine the binding stoichiometry of ‐6 to KDM2A. KDM2A was incubated with ‐6 and subsequently introduced into a mass spectrometer under conditions optimized for the preservation of noncovalent interactions.S,S)‐6 to KDM2A. To verify the identity of bound ‐6, we performed tandem‐MS on the 14+ charge state, resulting in the removal of ‐6 as a singly charged species ‐6 does not display competitive inhibition kinetics with respect to either 2‐OG or the peptide substrate (Section S6), thus suggesting a different mode of inhibition to the majority of previously discovered KDM inhibitors.S,S)‐6 did not displace fluorescent methylstat  in fluorescence polarisation assays. To probe the ‐6 binding site further, KDM2A was subjected to a photoaffinity labelling profile with a diazirine‐containing analogue of ‐6, and LC‐MS/MS experiments were conducted (Section S7). The majority of covalently modified residues were found to be either aspartic or glutamic acids, thus suggesting the formation of a relatively long‐lived electrophilic intermediate following photo‐induced isomerization of the diazirine to a diazo compound.Kinetic analyses subsequently revealed that ‐6 displays more than 75 fold selectivity towards KDM2A/7A versus other JmjC lysine demethylases and is, to our knowledge, the first reported selective KDM2A/7A inhibitor that has been demonstrated to reduce H3K36me2 demethylation within cells. This study demonstrates how the generation of three‐dimensional scaffolds bearing significant saturation and multiple chiral centres can lead to the discovery of selective compounds that may be useful in the study of a challenging epigenetic target.In conclusion, we have developed a potent and selective first‐in‐class inhibitor of the histone lysine demethylases KDM2A/7A. Compound  should be addressed to the authors.SupplementaryClick here for additional data file.


However, a number of challenging issues remain regarding its rate capability and cycle life, which must be addressed to enable greater application compatibility. Here, a facile and effective approach that can be used to overcome these disadvantages by introducing an aqueous carboxymethyl cellulose (CMC) binder is reported. The resulting conductive network serves to accelerate the diffusion of Na+ ions across the interface as well as in the bulk. The strong binding force of the CMC and stable solid permeable interface protect the electrode from degradation, leading to an excellent capacity of 75 mA h g−1 at an ultrahigh rate of 70 C (1 C = 128 mA g−1) and a long lifespan of 3500 cycles at 30 C while sustaining 79% of the initial capacity value. A full cell based on this electrode material delivers an impressive energy density as high as 216 W h kg−1, indicating the potential for application of this straightforward and cost‐effective route for the future development of advanced battery technologies.Polyanionic Na The past two decades have witnessed considerable technological advancements for rechargeable lithium‐ion batteries (LIBs), which are currently the storage technology of choice for portable electronic devices and electric vehicles; however, cost and safety issues remain two major obstacles that limit the use of LIBs in the smart grid. Taking into account the raw material abundance and battery cost as well as the similar electrochemical storage mechanism, room‐temperature sodium‐ion batteries (SIBs) based on Na‐ion shuttling between positive and negative electrodes are generally regarded as a promising choice for grid storage.[[qv: 1a–d]] Nevertheless, SIB technology must be further explored to obtain batteries that are more economical, safer, and show a high‐rate capability and longer durable life.[[qv: 2a–c]]3V2(PO4)2F3 (NVPF) is of particular interest because of its high theoretical energy density of nearly 500 Wh kg−1, approaching that of LiFePO4 used in LIBs.The robust 3D crystal structure and rapid Na‐ion insertion/extraction reaction in NASICON‐type phosphates afford a family of favorable electrode materials for SIB applications.[[qv: 3a–e]] Among the existing NASICON‐type materials, Na3V2PO2F3 (NVPFN‐methyl‐2‐pyrrolidone (NMP), which calls for a low processing humidity and poses a serious pollution threat to the environment. In addition to its insulating property, PVDF suffers from swelling and softening in ester‐based electrolytes due to the interactions between the polymer and electrolyte.Though numerous efforts have been dedicated to the development of active materials, comparatively little attention has been paid to the optimization of binders. In fact, as one of the most important and indispensable components of a battery, the binder plays a crucial role in realizing a high‐rate capability and long‐term cycle life, especially for the negative electrodes.] Up to now, poly(vinylidene difluoride) (PVDF) has been the most widely used binder; however, PVDF is usually dissolved in volatile, flammable, and explosive −1 at 70 C (1 C = 128 mA g−1) and a long lifespan of 3500 cycles at 30 C with a capacity retention of 79%. Further investigation shows that CMC is beneficial to the formation of a conductive network, protecting the structural and electrical integrity of the electrode as well as ameliorating the surface/interface property between the electrode and electrolyte.Herein, we demonstrate a facile and effective method for improving the rate capability and long‐term cycling stability of a NASICON‐structured cathode material utilizing CMC as a binder. By using this binder, we determine that the NVPF cathode can be used to realize a remarkable charging capability of 75 mA h g22.1a = b = 9.04 Å and c = 10.75 Å, consistent with previous reported values.The phase purity of pristine NVPF was first examined by powder X‐ray diffraction followed by a Rietveld refinement analysis, as shown in Figure S1 (Supporting Information). The data show sharp and well‐defined reflections that suggest a highly crystalline sample with no detectable impurities. The refined lattice parameters are FigureIn addition to the physical properties of the pristine materials, the composition and architecture of the working electrode can also affect the electrochemical performance, such as the rate capability and long‐term stability. Therefore, SEM and TEM were used to observe the morphologies of different NVPF electrodes prepared by mixing together the active material, conductive carbon, and CMC or PVDF binders . The NVPF–CMC electrode shows a loose and porous structure Figure1a, whi2.2+ insertion reaction on the Na(2) site; the higher plateau is mainly due to the ion insertion/extraction of the second Na+ on the Na(1) site.Figure−1 obtained at 70 C rate, which is almost 4 times higher than that of NVPF–PVDF. This is one of the highest rate performances reported for state‐of‐the‐art Na3V2(PO4)2F3 materials (see Table S1 in the Supporting Information). The corresponding discharge/charge profiles of NVPF–CMC show a long platform of 50 mA h g−1 at 3.25 V, which is in sharp contrast to the significantly polarized curves of the NVPF–PVDF electrode. These data clearly indicate that the CMC–Super P network greatly accelerates the charge/electron transfer and improves the rate capability.[[qv: 8a]] To gain further insight into the mechanism governing the sodium charge storage performance in the presence of the CMC binder, the electrochemical impedance spectra (EIS) were recorded at varying temperatures to calculate the activation energies for the working electrodes . Based on the fits of the Arrhenius plots, the activation energies were calculated to be 46.7 and 51.5 kJ mol−1 for NVPF–CMC and NVPF–PVDF, respectively  were recorded at different scan rates from 0.05 to 3.0 mV s−1 to obtain the Na+ diffusion coefficient. As shown in Figure ,f, three pairs of symmetrical redox peaks were observed for both binder systems, which was consistent with the working plateaus observed in the charge–discharge profiles. It is worth noting that the redox polarization of NVPF–CMC is much lower than that of NVPF–PVDF, suggesting better electronic and ionic transport kinetics. The linear fit of the relationship between the peak currents and the square root of the scanning rates can be used to calculate the Na+ diffusion coefficient, DNa, on the basis of the Randles–Sevcik equation .DNa based on all the oxidation/reduction peaks observed for the NVPF–CMC electrode resulted in values that are larger than those calculated for NVPF–PVDF, which indicates the improved transportation of Na+ ions in the cathode and leads to the observed enhancement in the high‐rate charge–discharge capability.The galvanostatic charge–discharge profiles of NVPF–CMC and NVPF–PVDF were recorded in the voltage range between 2.0 and 4.3 V at a 0.5 C rate. As shown in Figure S4 (Supporting Information), three working plateaus were observed at ≈3.4, 3.7, and 4.2 V. The lower two plateaus can be attributed to the two‐step Na4 or LiCoO2 cathodes, it has not been utilized before for SIBs.] Encouragingly, the NVPF–CMC electrode demonstrates an outstanding rate performance, i.e., a reversible capacity of 91 and 38 mA h g−1 at 10 C and 70 C, respectively . These data highlight the potential for practical applications of the CMC binder in commercial SIBs. Moreover, the enhancement in the rate capacity using CMC as a binder was also confirmed for another NASICON‐type cathode, Na3V2(PO4)3/C (X‐ray diffraction (XRD) pattern in Figure S10 in the Supporting Information). As shown in Figures S11 and S12 (Supporting Information), the Na3V2(PO4)3/C cathode using a CMC binder delivers a significantly improved rate capability and cycle stability compared to that with PVDF as the binder, which further demonstrates the beneficial utilization of the CMC binder in SIBs.To further verify the practical validity of the CMC binder in commercial SIBs, the weight ratio of the active materials, NVPF:Super P:binder, was increased from 7:2:1 to 9:0.5:0.5. It is important to note that although such a high weight ratio  is similar to the value used for commercial LIBs based on LiFePO2.3Figure,d). This thickness change can be attributed to a swelling effect due to the PVDF.,f and Videos S1 and S2 (Supporting Information)). Consequently, an ex situ SEM image of the NVPF–CMC electrode taken after 100 cycles showed perfect integrity, while the image for NVPF–PVDF clearly showed cracks that can be attributed to either the weaker adhesion force or degeneration of the PVDF , the surface film is supposed to prevent further electrolyte degradation and corrosion of the cathode materials.] Indeed, the XPS data show that the SPI film is very stable after 100 cycles, without any obvious increase in content. Moreover, an SPI film can also ameliorate the kinetic property at the surface/interface between electrode and electrolyte. In Figure In terms of the conspicuously enhanced high‐rate capability, the long‐term durability of the two different working electrodes was also examined at 10 C ; the data show that the NVPF–CMC shows a higher capacity and better stability than NVPF–PVDF. The difference between the two electrodes increases once the current density is increased to 30 C. The NVPF–CMC electrode maintains 79% of its initial capacity following cycling, which is superior to the value of 61% for the NVPF–PVDF electrode Figure g. The im2.4Figure−1. The full cell can be used to deliver a large capacity of 124.8 mA h g−1 between 2.0 and 4.3 V with the energy density of the cell calculated to be ≈216 Wh kg−1 on the basis of the total cathode and anode mass, as shown in Figure A full Na‐ion battery with a high energy density was constructed by combining an NVPF–CMC cathode with a hard carbon (HC) anode for operation in the voltage ranges of 2.2–3.9 V  and 2.0–4.3 V Figure5. To e3−1 at an ultrahigh rate of 70 C (1 C = 128 mA g−1) and a long lifespan of 3500 cycles at 30 C rate with capacity retention of 79%. Finally, a full battery cell assembly using hard carbon as the anode exhibits an energy density of 216 Wh kg−1, which suggests the potential for application in future scalable energy storage systems. The strategy we have proposed here is believed to be widely applicable to other cathode materials for sodium‐ion batteries.We have demonstrated a facile and effective route to improve both the rate capability and cycle stability of NVPF by using an aqueous CMC binder. A conductive network consisting of CMC–Super P chains provides long‐range charge transfer pathways and a porous architecture. The electrochemical characterizations showed that Na‐ion diffusion in the bulk material and at the interface is accelerated due to improved electrochemical kinetics. Furthermore, the SPI interfacial film induced by the CMC binder limits the resistance increase and maintains the integrity of the electrode. Thus, the electrode enables an excellent capacity of 75 mA h g4Material Synthesis: The Na3V2(PO4)2F3@C nanocomposite was prepared by a facile sol–gel method following the previous work.4VO3, NaF, and NH4H2PO4  with a molar ratio of 2:3:2 were dissolved in deionized water. Then, a saturated citric acid [HOC(COOH)(CH2COOH)2] solution was added into the above solution until the ratio of vanadium:citric acid equaled 5:4. Next, the obtained solution was evaporated at 80 °C, dried at 120 °C for 12 h, and ground to form a precursor. Finally, the precursor was preheated at 300 °C for 4 h and sintered at 650 °C for 8 h under a nitrogen atmosphere with intermediate grinding to obtain the NVPF@C nanocomposite.e Na3V2PO2F3@C nanMaterial Characterization: The phase purity of the obtained samples was examined by XRD using a RigaKu D/max‐2550 diffractometer with Cu Kα source in the 2θ range of 10°–80° at a scanning rate of 1.7° min−1. Rietveld refinement was used to confirm the phase purity. The morphological features were observed by a Hitachi SU8020 scanning electron microscope and an FEI Tecnai G2 transmission electron microscope. Raman spectroscopy was carried out using a Renishaw in Via Raman system with an Ar‐ion laser excitation (λ = 514.5 nm). The samples for the swelling test were observed under a Hitachi SU8020 SEM. The NVPF–CMC and NVPF–PVDF electrodes were cut into two parts: one part was maintained in a dry condition and the other wetted in the electrolyte for the same time. Then, the thicknesses of the two electrodes for both the dry and wet conditions were measured by SEM of the cut section. The adhesion forces were measured by a peel‐test experiment. A piece of stainless‐steel foil was attached to another piece of stainless‐steel foil using either the CMC binder or PVDF binder in equal amounts; then, one of the stainless‐steel foils was fixed to a wall. Next, weights were added onto the free end of the stainless‐steel foil to draw it downward. The weights were added gradually and measured by a spring‐loaded thrust meter until the stainless‐steel foil completely peeled off from the other foil. Finally, the reading from the spring‐loaded thrust meter was taken. X‐ray photoelectron spectra were measured using a VG scientific ESCALAB‐250 spectrometer.Electrochemical Measurements: All the electrochemical tests were carried out using coin‐type cells (CR2032). Sodium half cells were assembled using sodium foil as the counter electrode. The working electrodes were fabricated by coating a slurry prepared from a mixture of the active material, Super P conductive additive, and binder (sodium CMC dissolved in water or PVDF binder dissolved in NMP) in a weight ratio of 7:2:1, respectively, on an aluminum‐foil current collector. The electrode films were successively dried in a vacuum oven at 120 °C for 12 h. After patterning the electrode film into a square of area 0.8 × 0.8 cm2, the coin cells were assembled in a glove box. The loading mass of the materials was 1.1–1.6 mg cm−2. Glass fiber filters (Whatman GF/C) were used as separators for the cells. The electrolyte solution was prepared from 1 m NaClO4 dissolved in ethylene carbonate and propylene carbonate (1:1 v/v) with the addition of 5% fluoroethylene carbonate. Galvanostatic charge–discharge tests were carried out over a voltage range of 2.0–4.3 V at room temperature using a Land‐2001A  automatic battery tester. The specific capacities were calculated based on the Na3V2(PO4)2F3 mass. CV and electrochemical impedance spectra (EIS) were carried out using a VSP multichannel potentiostatic–galvanostatic system . CV curves were collected at different scanning rates ranging from 0.05 to 3.0 mV s−1. The EIS were measured in the frequency range from 1 MHz to 1 mHz. Sodium‐ion full cells were assembled in the same manner as the half cells except with hard carbon as the anode. Sodium‐ion full cells were cycled over different voltages ranging between 2.2–3.9 and 2.0–4.3 V.The authors declare no conflict of interest.SupplementaryClick here for additional data file.SupplementaryClick here for additional data file.SupplementaryClick here for additional data file.


So far only a very limited number of STSs have been characterized. The discovery of three new plant STSs is reported that produce a suite of sesterterpenes with unprecedented 6/11/5 and 6/6/7/5 fused ring systems when transiently co‐expressed with a GFPP synthase in Nicotiana benthamiana. Structural elucidation, feeding experiments, and quantum chemical calculations suggest that these STSs catalyze an unusual cyclization path involving reprotonation, intramolecular 1,6 proton transfer, and concerted but asynchronous bicyclization events. The cyclization is diverted from those catalyzed by the characterized plant STSs by forming unified 15/5 bicyclic sesterterpene intermediates. Mutagenesis further revealed a conserved amino acid residue implicated in reprotonation.Sesterterpenoids are a relatively rare class of plant terpenes. Sesterterpene synthase (STS)‐mediated cyclization of the linear C TPSs can be categorized into two classes (I and II) depending on the mode of initiation of cyclization of the linear precursor substrates. Class I TPSs are metal‐dependent enzymes that initiate cyclization of linear isoprenoid diphosphates via abstraction of the diphosphates for carbocation generation, whilst class II TPSs initiate catalysis by protonation of a C=C bond or epoxide group in an isoprenoid substrate.Terpenoids are the largest class of natural products, with over 80 000 molecular structures discovered to date.5 isoprene units, constitute a relatively rare subclass of terpenes. The majority characterized to date are from marine sponges and terrestrial fungi, with only about 80 structures reported from the plant kingdom so far.trans‐prenytransferase (PT) domain; the latter synthesizes geranylfarnesyl diphosphate (GFPP), the substrate for TPS‐mediated cyclization, from dimethyl allyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP).12 carbocation (A1), for example, (+)‐quiannulatene by fungal EvQS and (−)‐ent‐quiannulatene by plant AtTPS25 , belonging to an unexplored clade (clade IV) that has diverged from the three other plant STS clades , were functionally characterized and their dominant products shown to be “fungal‐type” sesterterpenes  carrying the expression constructs were infiltrated into the undersides of leaves of N. benthamiana, resulted in the production of multiple peaks. These peaks, including (2–8), all have a characteristic m/z=340 [M]+ fragment, suggesting the formation of sesterterpenes ‐2 a and ‐2 b, respectively . In the cyclization paths catalyzed by the Clade I, II, and III STSs, the C19 carbocation (A) undergoes a 1,5 hydride shift to form the unified C12 bicyclic carbocation (A1) that leads to formation of one group of dominant end products ‐brassitetraene A and B, respectively.Transient expression of individual STS with a GFPPS gene by “agro‐infiltration”,ncluding –8, all hncluding –8, all hncluding –8, all h3 a and 3 b were inseparable by silica chromatography, and attempts to separate them on an alumina column resulted in recovery of 3 b only, suggesting that 3 a might be isomerized to 3 b during chromatography. Compound 3 b was isolated as a white solid and a crystal structure obtained. NMR and X‐ray diffraction analysis of 3 b  established its scaffold as an unprecedented 6/11/5 tricyclic fused ring, with relative stereochemistry ‐3 b  ‐caprutriene B and (+)‐caprutriene C, respectively.Compounds 4–8 were all tetracyclic sesterterpenes having two C=C bonds, evident by the four olefinic signals in their 13C NMR spectra. Further analysis of their 2D NMR spectra, including HSQC and HMBC, established the nature of the novel 6/6/7/5 fused ring system shared by these five compounds, with variation of the position of one endo C=C bond . NOESY spectra revealed differences in stereochemistry mainly at the C6 and C7 positions, with 4, 5, 6, 7 and 8 having relative stereochemistry as ‐4, ‐5, ‐6, ‐7 and ‐8, respectively. Compounds 4–8 were named (−)‐caprudiene A, (+)‐brarapadiene A, (−)‐brarapadiene B, (−)‐arathanadiene A, and (−)‐arathanadiene B, respectively.Compounds 2–8, we then sought to establish the absolute configurations of these compounds by constructing a conjugated system in the molecule to allow for measurement of ECD spectra in the near UV to visible wavelength range, followed by comparison with ECD spectra predicted by quantum chemical calculations. We successfully installed an enone moiety into compound 6 to form compound 9 via metal‐mediated allylic oxidation using pyridinium dichromate coupled with tert‐butyl hydroperoxide ‐9 established its absolute structure as ‐9 . The absolute structure of its precursor compound 6 is assigned as ‐6. Although the absolute configurations of other compounds are yet to be established, the fact that compounds 2–5 and 7–8 share the same relative stereochemistry with 9 at C14 and C15 as well as the communal precursors 2 a and 2 b strongly suggests that their absolute structures are as depicted in Figure Having determined the relative stereochemistry of structures e Figure . Compari2–8 include bi‐, tri‐, and tetracyclic scaffolds that are derived from the corresponding carbocation intermediates during cyclization, and reflect a unified cyclization path towards the formation of the 6/6/7/5 scaffold catalyzed by the three TPSs investigated herein. Based on the structures, we propose a cyclization path that involves a second‐stage reprotonation at C10=C11 of the common substrate 2 a/b to generate a tertiary C11 carbocation B, which may then undergo either direct C6–C11 ring closure followed by deprotonation to form tricyclic caprutriene B and C, or (H12‐C2) intramolecular 1,6‐proton transfer (B→D) resulting in net double bond migration (C10=C11 in 2 a to C11=C12 in D). Subsequent ring closure events  followed by 1,2‐hydride and 1,2 methyl shifts and deprotonation then yield compounds 4–8, each with a 6/6/7/5 fused ring system.Interestingly, the isolated compounds N. benthamiana leaves expressing the plant STS genes at different time points  after watering the plant with pure D2O for seven days, starting from the third day post‐infiltration,2 a versus products 5–8 or 2 b versus 3 a and 3 b decreased significantly over time. In sharp contrast, the abundance ratio of the MS fragment 341/340 increased correspondingly for Br580, AtTPS17 and Cr089 . This suggests that intermediate 2 a/2 b, once formed, might either reside in or released and rebound to the active site for reprotonation by D2O. Since this new unified cyclization path is diverted from cyclization paths catalyzed by plant STSs from Clades I, II, and III, finding conserved amino acid sites in clade IV STS that are different from other clades could potentially unveil the key amino acids that reroute the cyclization path from cation A. Sequence comparison of the characterized plant STSs with the Clade IV STSs identified two conserved amino acid sites (N354 and K424 in AtTPS17) in the active site regions of Clade IV STSs that differed from those of other STSs , but its product profile was altered; it showed a significant reduction in the formation of tetracyclic compounds 7 and 8, as evident by the decreased area ratio of 7 and 8 versus 2 a in the mutant (1.3) compared to that in the wild‐type , and more recently for fungal STS astellifadiene synthase).2 a to 7 and 8 by mutant AtTPS17K424I, which is in stark contrast to the complete consumption of 2 a by the wild‐type AtTPS17 after 10 days post infiltration, further suggesting that this site might be involved in the reprotonation process and that lysine424 might be serving as a general acid/base aiding in reprotonation.Moreover, prolonged reaction time (10 days) did not lead to significant further conversion of D was shown to be energetically viable.  in the mass spectra of products in our D2O feeding experiments exclude this possibility . There are precedents for intramolecular proton transfer in terpene forming reactions, but not all such proposed transformations are energetically viable.D to prepare for the subsequent ring closure event. Cation E is found not to be a minimum ; instead a concerted bicyclization, in which the C−C bond formation events occur asynchronously, is found for the conversion of cation D to F.B to the transition state structure for the D→F conversion is about 18 kcal mol−1 . The D→F reaction sets the relative stereochemistry of C3, C6, C11 and C12. Cation F, once generated, can undergo low barrier 1,2 hydride and methyl shifts to form cation G, which, upon deprotonation, leads to compounds 4, 5, 6, and 7. Further 1,2 hydride and methyl shifts of cation H followed by deprotonation furnish (−)‐arathanadiene B (8).Quantum chemical computations //B3LYP/6–31+G; see Supporting Information for details) were carried out to assess the viability of our proposed mechanism. An intramolecular 1,6‐proton transfer event for the generation of carbocation . Figure . Althoug3 a) and C (3 b) and 6/6/7/5 tetracyclic (−)‐caprudiene (4), brarapadiene A (5) and B (6) and arathanadiene A (7) and B (8) via a new unified cyclization path. Sequence analysis and site‐directed mutagenesis further identified a key amino acid site (Lys424 in AtTPS17) implicated in mediating the reprotonation of compounds 2 a/b. Although we have not yet determined the exact mechanism by which Lys424 may participate and mediate the reprotonation reaction due to the lack of an accurate plant STS crystal structure as a template for modeling ,2O in position as a proton donor. Having the crystal structure of a STS in complex with relative substrates will be key to understanding the mechanisms. Our findings pave the way for further mechanistic studies and for protein engineering experiments aimed at understanding and generating sesterterpene diversity. Moreover, together with quantum chemical calculations, we demonstrate that a carbocation cyclization/rearrangement path that involves intramolecular 1,6 proton transfer and concerted but asynchronous double cyclization is energetically viable. This diverted cyclization path underscores the phylogenetic divergence of the plant STSs and the tremendous chemical engineering potential harbored within the plant kingdom. Our work also demonstrates the power of evolutionary genomics‐based approaches for unlocking this potential for natural product discovery.To summarize, we have discovered and functionally characterized a phylogenetically diverged clade of plant STSs that catalyze the formation of unprecedented 6/11/5 tricyclic caprutriene B  should be addressed to the authors.SupplementaryClick here for additional data file.


Two isomers, different only by bond angles, are discovered for Au2I3–, due to competition between aurophilic interactions and covalent bonding. 2I3– cluster, which is found to exhibit two types of isomers due to competition between Au–I covalent bonding and Au–Au aurophilic interactions. The covalent bonding favors a bent IAuIAuI– structure with an obtuse Au–I–Au angle (100.7°), while aurophilic interactions pull the two Au atoms much closer, leading to an acutely bent structure (72.0°) with an Au–Au distance of 3.08 Å. The two isomers are separated by a small barrier and are nearly degenerate with the obtuse isomer being slightly more stable. At low temperature, only the obtuse isomer is observed; distinct experimental evidence is observed for the co-existence of a combination of isomers with both acute and obtuse bending angles at room temperature. The two bond-bending isomers of Au2I3– reveal a unique example of one molecule being able to oscillate between different structures as a result of two competing chemical forces.We report a joint photoelectron spectroscopy and theoretical investigation of the gaseous Au The chemical and physical properties of chemical compounds are dictated by their molecular structures.I centers.I compounds. Strong relativistic effects and dispersion-type electron correlations were found to be the major driving forces of aurophilicity.In addition to the strong chemical bonding that determines molecular structures, weaker aurophilic interactions have been found in gold systems due to attractions between closed-shell Au2I3– cluster, in which aurophilic interactions turn out to play a key role. This anion is found to have a C2v bent geometric configuration of I–Au–I–Au–I– and exhibit two near-degenerate isomers that we name as “bond-bending isomers (BBIs)”, similar to BSI, which has not been experimentally established heretofore.2I3– reported here differ only in geometry by the bending angle  and quantum chemical study on the gaseous Aung angle , owing tn] type unit could form polyhedra, due to strong aurophilic interactions,2I3–. Both isomers of Au2I3– are in singlet spin-states and can inter-convert easily at elevated temperatures because of the low energy barrier between them.Schmidbaur and Schier predicted that the  for Au and [1s2–4d10] for I. The scalar relativistic (SR) and spin orbit (SO) effects were taken into account by the zero-order-regular approximation (ZORA).64For chemical bonding analyses, we used the energy decomposition approach (EDA),via natural population analyses (NPA)In order to obtain multi-center localized orbitals, we used the Multiwfn2I3– anion was produced using two different methods and the experiments were carried out using two separate magnetic-bottle PES apparatuses, one equipped with an electrospray ionization (ESI) sourcevide infra).The Au2I3– anions were selected and decelerated before being photodetached by the 193 nm (6.424 eV) radiation from an ArF excimer laser at several experimental conditions, as shown in In order to have a better understanding of the congested PES features, temperature-dependent experiments were carried out using a laser vaporization supersonic cluster source.193 nm 6.4 eV radi193 nm 6.4 eV radiPhotoelectron spectra taken at 193 nm were designated as ‘hot’, ‘warm’, and ‘cold’ in ab initio wave function theory (WFT) at different levels  calculations, as shown previously.71We used both density functional theory (DFT) and  Table S2 show thaab initio coupled-cluster method. Thus, high-level quantum chemical methods are crucial in accurately characterizing these nearly degenerate isomers. The full computational results for the energy difference between the acute and obtuse isomers (ΔEA–O) are given in Table S3.–1 higher in energy than the two BBIs. Preliminary calculations with the SO-ZORA approach show that SO effects are important for all these species, whereas the relative energies are not affected. –1 at CCSD(T) level. Such a low barrier suggests that the two BBIs can easily inter-convert. Hence, at elevated temperatures many different configurations are expected to co-exist along the bending angle, in excellent agreement with the experimental results, as shown in Table S1vide infra). The SCS-MP2/AVTZ calculations gave a bending angle of 80.1° for the transition state between the two BBIs. It is interesting to compare the bonding between I5– with an apical angle of 94° and the obtuse Au2I3– isomer,2I3–.Because of the inherent aurophilic interactions between the two Au atoms, calculated results from the long-range corrected functionals agree with those from the –1, we estimated a lifetime of about 104 ns for the acute BBI, which is sufficiently long-lived to be observed in the photodetachment experiments  escape probability.eriments  and 3a. 2I3– in 2I3– cluster resides in its electronic and vibrational ground state with the obtuse structure, giving rise to the intense PES features . Under the hot and warm conditions .The photoelectron spectra of Aunditions , the Au2Because the barrier between the two BBIs is low, the broad part of the potential energy curve will be accessed at high vibrational levels or high temperatures, resulting in new spectral features, in remarkable agreement with the experiment. The diffuse X′ low binding energy feature appearing in the hot spectrum by laser vaporization  or the r1, 3a1 and 2a1 MOs of the acute isomer represent Au–Au interactions that are not present in the obtuse case. The 1b1 MOs in both isomers are dominated by Au1(5d)–Ic(5p)–Au2(5d) π-type bonding and have comparable orbital energies, as shown in Fig. S2 and S3.g and σu for the linear configuration, a1 and b2 for the bent obtuse or acute structures –1a1(A) orbital is considerably stabilized in the acute isomer, whereas the 1σu–1b2(O)–1b2(A) orbital is significantly destabilized in the acute isomer. The different stabilities of the 1a1 and 1b2 orbitals probably play a key role in the near degeneracy of the two isomers.We performed various chemical bonding analyses to elucidate the electronic structures of the two BBIs. The chemical bonding can be glimpsed from the electron localization functions (ELFs) shown in s Fig. S4. The 1σg1 and 1b2 MOs in the acute isomer seem to form two types of three-center two-electron (3c–2e) bonds; one is along the C2 axis while the other is perpendicular to the C2 axis, as shown more clearly in the bonding analysis in Fig. S5c′ and d′.– or the Au2I42– complex.c interactions, resulting in the more acute angle for Au1–Ic–Au2 and elongated Au1,2–Ic bond length. However, the 1a1 and 1b2 MOs in the obtuse isomer simply represent two two-center two-electron (2c–2e) Au1,2–Ic bonds, as shown in Fig. S5c and d.As shown in Fig. S4,i)···Au(i) aurophilic attraction becomes stronger at the cost of weakening the covalent bonding between the central I and the adjacent Au in the acute isomer. All methods give a larger Au–Au bond order and a smaller Au–Ic bond order in the acute isomer relative to the obtuse isomer. The Au–Au and Au–Ic stretching frequencies show a similar trend. 2 MOs in the obtuse isomer are 1.15 eV stronger than that in the acute isomer. On the other hand, the orbital interactions of the a1 MOs in the acute isomer are 1.04 eV more stable than the obtuse isomer, suggesting that the energy difference of these two isomers is mainly due to the energy competition between the b2 and a1 orbitals. It is also shown that the contribution of the SO coupling effect to the total bonding energy is significant (6.40 eV), but the correction is the same for the isomers with different bending angles (The calculated bond orders based on various theoretical schemes and adiabatic stretching force constants in both the acute and obtuse conformers are given in Table S4.g angles . Accordi2I3–, which are only different by the IAu–I–AuI bond bending angles as a result of the competition between Au–I covalent bonding and Au–Au aurophilic interactions. High-level theoretical calculations showed that the acute and obtuse isomers are nearly degenerate in energy and separated by a small energy barrier with the obtuse isomer slightly lower in energy. Temperature-dependent photoelectron spectra were obtained for Au2I3–, which was produced with two completely different experimental methods, with clear evidence for the presence of these isomers. Systematic chemical bonding analyses revealed the subtle differences in the bonding interactions of the two types of structural isomers. The current finding presents a rare example of structural isomerism, akin to the long proposed concept of bond-stretching isomers.In summary, we have observed two bond-bending isomers for gaseous AuSupplementary informationClick here for additional data file.


Diverse advanced logic circuits are fabricated to implement arithmetic functions based on a simple and single molecular beacon platform, including half adder, half subtractor, full adder, full subtractor, and a digital comparator. Dual fluorescence outputs are generated in parallel and a constant threshold value is set to build all the logic circuits. The developed enzyme‐free DNA system provides a novel prototype for the design of high‐level molecular logic circuits on a biomolecular platform. Looking through the history of humanity with respect to count and computing, electronic computers appeared just about 60 years ago, exhibiting unprecedented performance and thus revolutionizing computation. However, electronic computers mark neither the beginning nor the end of the history of computation due to its limits. Molecular computing is a fascinating area of research that involves molecular‐level data processing and has projected chemistry onto the forefront of information and technology.To make further advancements in molecular computation, we constructed a series of advanced logic circuits in proof‐of‐principle experiments using DNA to execute multiple arithmetic functions, including half adder, half subtractor, full adder, full subtractor, and digital comparator.FigureN‐Methylmesoporphyrin IX (NMM) is used as a second fluorescent reporter, generating enhanced fluorescence upon formation of a G‐4 (G‐quadruplex)/NMM complex.A half adder is an essential component of a digital signal processor to add two binary digits (bits) and can be implemented by integrating an AND and an XOR (XOR: exclusive OR) logic gate in parallel.FigureA half‐subtractor operation was also pursued based on the same MB platform and two new designed inputs (HS‐IN 1 and HS‐IN 2). The principle is illustrated in FigureCin]). NMM and FAM fluorescence were also utilized as output signals, corresponding to CARRY OUT (Cout) and SUM OUT (Sout), respectively.Because all arithmetic functions, such as division, multiplication, exponentiation, can be implemented through integration of individual adders,Cin), is able to open the MB hairpin. When any two of the three inputs are present at the same time, their mutual hybridization dominates the interactions in the system, inhibiting the hybridization of either input to MB, resulting in a weak FAM signal. Meanwhile, the hybridization of any two inputs can produce a G‐quadruplex from the respective G‐rich segments, resulting in a strongly fluorescent G‐4/NMM complex. In the presence of all three inputs, FA‐IN 2–3 hybridization is designed to dominate the reactions in the system and FA‐IN 1 is left free to hybridize with MB. The FAM and NMM fluorescence emission spectra in the presence of different input combinations are shown in Figure Cin): 0 + 0 + 0 = 0 (00), 0 + 1 + 0 = 1 (01), 1 + 0 + 0 = 1 (01), 1 + 1 + 0 = 2 (10), 0 + 0 + 1 = 1 (01), 0 + 1 + 1 = 2 (10), 1 + 0 + 1 = 2 (10), and 1 + 1 + 1 = 3 (11). Only the last operation is different from that for a half adder, where Cout = Sout = 1, corresponding to 1 + 1 + 1 = 3.To construct a full adder, in general, each DNA strand input includes three functions; two functions are related to the generation of the two readout signals and the third function mediates the hybridization of DNA strands, favoring desired interactions while suppressing undesirable side reactions. To mediate the complicated interactions among the three inputs and the MB platform, a two‐base mismatch strategy was used to control hybridization energy and decrease secondary structure of the DNA input, directing the desired hybridization in a complex system. In brief, a two‐base mismatch was embedded in the sequence in each input that hybridizes to MB, which facilitates subsequent interaction in the presence of additional inputs through fully complementary hybridization. As shown in Figure FigureBin]), NMM and FAM fluorescence were again employed as the two output signals, serving as BORROW OUT (Bout) and DIFFERENCE OUT (Dout) digits, respectively. The complex logic circuit is shown in Figure Dout takes into account an addition of 2 to the first input under conditions of a high borrow (Bout = 1), akin to a half subtractor. The detailed arithmetic operations (FS‐IN 1 – FS‐IN 2 – Bin) are: (1) 0 – 0 – 0 = 0; (2) 0 – 1 – 0 = (‐1), which becomes 2 – 1 – 0 = 1 in the case of high borrow; (3) 1 – 0 – 0 = 1; (4) 1 – 1 – 0 = 0; (5) 0 – 0 – 1 = (‐1), it becomes 2 – 0 – 1 = 1 in the case of high borrow; (6) 0 – 1 – 1 = (‐2), changing into 2 – 1 – 1 = 0 in the case of high borrow; (7) 1 – 0 – 1 = 0; and finally, (8) 1 – 1 – 1 = (‐1), which becomes 3 – 1 – 1 = 1 in the case of high borrow.To further demonstrate the reconfigurability and scalability of the present system, a full subtractor was developed based on the same MB platform with stimulation by three newly designed inputs. Full subtractor is another logic circuit of the highest complexityFor the sake of completeness, binary multiplication may be achieved because it follows the same rules as the truth of an AND gate. This is similar to binary division, which is the result of repeated subtraction .In summary, a series of DNA‐based comprehensive logic circuits has been generated to perform arithmetic functions, including half adder, half subtractor, full adder, full subtractor, and a digital comparator. In comparison with previous studies,As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.SupplementaryClick here for additional data file.