High‐resolution magnetic resonance imaging (MRI) of the cervical spinal cord is important to provide accurate diagnosis and pathological assessment of injuries. MEDIC (Multiple Echo Data Image Combination) sequences have been used in clinical MRI; however, a comparison of the performance of 2D and 3D MEDIC for cervical spinal cord imaging has not been reported. The aim of this study is to compare axial 2D and 3D MEDIC for the visualisation of the grey matter (GM) and white matter (WM) of the human cervical spinal cord.fit 3T MRI. T2*‐weighted gradient spoiled 2D and 3D MEDIC sequences were acquired at 0.4 × 0.4 × 3.0 and 0.3 × 0.3 × 3.0 mm resolutions, with the acquisition times of 6 and 7 min, respectively. Quantitative analyses of the images were made based on the image signal‐to‐noise ratio (SNR), contrast‐to‐noise ratio (CNR) and non‐uniformity (NU). Two independent radiologists (CS and FN), each provided Likert scoring assessments of anatomical visibility of the GM and WM structures and image clarity for all samples.Eight healthy participants were scanned using Siemens PrismaQuantitative evaluation showed that 3D MEDIC provided higher SNR, higher CNR and lower NU than 2D MEDIC. However, 2D MEDIC provided better anatomical visibility for the GM, WM and CSF, and higher image clarity (lower artefacts) compared to 3D MEDIC.2D MEDIC provides better information for depicting the internal structures of the cervical spinal cord compared to 3D MEDIC. 2D MEDIC provided better quality images for depicting the cervical spinal cord's white and grey matter structures with reduced artefacts and superior clarity compared to the 3D MEDIC. This paper showed that the 2D MEDIC can potentially be used to obtain reliable measurements of atrophy and lesions in the internal spinal cord structures, which is important for diagnosis in diseases such as multiple sclerosis and spinal cord injury.  MRI has been widely used as a non‐invasive tool to assess cervical spine pathology as it demonstrates high resolution of the bone structure and soft tissue in multiple planes.2D T1‐ and T2‐weighted fast spin echo (FSE) sequences at 3T have been shown to produce better visualisation of the cervical spinal cord than those at 1.5T.New gradient technology (80mT/m gradients with >200mT/m/s slew rates), allows further development of spoiled T2* gradient combined echo sequences  or multi‐echo fast field echo (M‐FFE)) to achieve high image resolution and short acquisition times.MEDIC refers to a T2*‐ spoiled gradient echo sequence consisting of a single radiofrequency excitation followed by multiple bipolar gradient echoes that are combined to form an image.This study compared the performance of 2D and 3D MEDIC sequences acquired with comparable scan times at 3T to obtain the best image quality for delineating the human cervical spinal cord structures. Our hypothesis was that 3D MEDIC could provide higher image resolution and quality for the delineation of the grey and white matter structures compared to 2D MEDIC. The MRI protocol included the anterior and posterior aspects of spinal roots and evaluated the GM and WM tissue contrast, SNR, image artefacts and anatomical structure visibility. A further aim of this study was to facilitate improvements in the quality of cervical spinal cord imaging for a wide range of clinical diagnoses.fit  at the Centre for Advanced Imaging. A 64‐channel head‐and‐neck coil was used for imaging. The participants had a mean age of 30.25 ± 6.52 years (mean ± SD). Each participant gave written consent, and the study was approved by The University of Queensland Human Ethics Committee. All data was de‐identified on the scanner.Eight healthy volunteers  were recruited and underwent MRI cervical spine scans on a 3T PrismaThe scan protocol consisted of a sagittal T2‐weighted FSE localiser, an axial 2D MEDIC and an axial 3D MEDIC. The MRI sequence parameters are shown in Table The axial 2D MEDIC used a multi slice package mode, where each slice package was positioned in the centre of each cervical level. The first slice was positioned on the superior surface of the body of the vertebra (C1 to C7), and the group slices were set perpendicular to the spinal cord in the anterior/posterior (A/P) and left/right (L/R) directions. An anterior saturation band was used to diminish swallowing movement artefacts. The axial 3D MEDIC parameters were optimised from a study of cervical spondylotic myelopathy.The 2D and 3D MEDIC parameters were chosen to obtain the best image quality whilst maintaining similar in‐plane resolutions and acquisition times. The 2D and 3D MEDIC had a similar T2* contrast based on the range of the TEs used. Minimum TR was selected for the number of slices. Compared to the 3D MEDIC, the 2D MEDIC required a longer TR to accommodate the number of slices. An Ernst angle calculation indicated that the 3D MEDIC would have a stronger T1‐weighting than the 2D MEDIC.Axial images C1‐C7 were compared side by side between the 2D and the 3D MEDIC. To ensure that the spinal cord visualisation was done at the same level from C1 to C7, RadiAnt Digital Imaging Communication in Medicine (DICOM) viewer Software  was utilised to view the positions 2D and 3D MEDIC axial slices using the sagittal image localiser as a reference.2) for the GM, WM and CSF were the same for the equivalent cervical level in each patient. They were anatomically constrained to patients cord structure and size. The entire anatomical region is used for the calculation of the SNR and CNR. For the measurement of the background signal, circular ROIs with 20 mm diameter were placed in the area outside the image, away from ghosting artefacts  measurement was performed using ITK‐SNAP (itksnap.org) to calculate the mean and standard deviation (SD) of signal intensities in the GM, WM, CSF and background noise of each cervical level of each participant. The polygon inspector and the brush tools were used to manually segment each anatomical ROI. The size of the ROIs , contrast‐to‐noise ratio (CNR) and non‐uniformity (NU).SNR measures the differences in signal intensities between the tissue of interest and the background noise. The ROIs used to measure the background noise were placed in similar location in each dataset to avoid any phase or ghosting artefacts. Higher SNR is desired as it will diminish the grainy appearance of the image.SNRtissuex=meanSItissuex‐meanSIbackgroundairStandarddeviationofbackgroundair where, x = a given tissue, SI = Signal Intensity.CNR refers to the differences in signal intensities between two anatomical regions. An increase of CNR will improve the ability to delineate two different regions of interest.NU refers to the presence of irrelevant intensity variation in the field of view.The mean signal intensity and the standard deviation of signal intensity were measured using the same ROI tissue area used in the CNR and SNR calculations.Two experienced neuro‐radiologists (CS and FN) assisted this study as independent blinded observers to evaluate anatomical visibility and image clarity of all images of the cervical spinal cord.Anatomical Visibility. Evaluation of the anatomical structures of the cervical spinal cord involved the identification of WM and GM structures, especially for the configuration of the H or butterfly shapes. For this assessment, a Likert scoring scale 1–5Image clarity. This includes detection of movement artefact, CSF pulsation or aliasing artefact that affected image quality. To evaluate the presence of artefacts on the images, a‐three‐point scoring scale was used as follows: 1 = extensive artefacts, therefore cannot be used for clinical diagnosis; 2 = moderate artefacts, can be used partially for diagnosis; 3 = minimum or no artefact, excellent use for diagnosis.P‐value < 0.05 was considered statistically significant.Mean and standard deviations were calculated within each cervical level, across all participants from the 2D and 3D MEDIC datasets. Each cervical slice was treated as paired variables during the analyses. Non‐parametric, paired sample t‐tests were employed to evaluate differences in SNR, CNR, NU, anatomical visibility of GM, WM, CSF structures and image clarity. Statistical analyses were performed using Microsoft Excel. A Correlation analyses of image quality assessments. Two‐tailed Pearson’s correlation tests (R) were used to measure the correlations of 2D and 3D MEDIC image parameters  to the visibility of the GM structure. The statistical tests were performed using SPSS, and normality tests were used to confirm the type of data distribution.Cervical spine MRI of both axial 2D and axially resliced 3D images were arranged for each participant and the cervical spine levels. An example of participants’ cervical spine image portfolio can be seen on Figure P = 0.50), but their average signal intensities are significantly different: 211.77 ± 49.61 and 450.02 ± 123.20 for the 2D and 3D MEDIC respectively (P < 0.01). The averaged GM SNR of the 3D MEDIC (69.23 ± 13.10) was higher than that of the 2D MEDIC (26.75 ± 5.93) (p < 0.01). A similar SNR was observed at C1, but the SNR of the 2D were significantly lower at the lower levels of the spine  and 3D MEDIC . The CNR profile along the length of the cord parallels that of the SNR. A similar CNR was observed at C1 and the largest difference was found at C7  compared to 2D MEDIC  and the CSF (P < 0.01), but not for the grey matter (P = 0.72). Overall, 3D MEDIC showed a lower NU value (better image homogeneity) compared to the 2D MEDIC . From C2 to C7, the visibility of the grey matter for 3D and 2D decreased steadily across the C2 to C7. A pairwise statistical t‐test performed for the whole cervical levels showed that there was a significant difference between 3D and 2D MEDIC for grey and white matter visibility (P = 0.03). 2D MEDIC showed a higher CSF visibility score compared to the 3D . The visibility and statistical test results are shown in Table The visibility scores of the grey and white matter structures from C2 to C7 were similar Fig. A and B,  3D Fig. C. The CSP < 0.01). The graph indicates that 3D MEDIC produces more artefacts than 2D MEDIC across all slices. The type of artefact seen on the images was motion artefact.The image clarity scores of the 2D and 3D MEDIC are shown in Figure R = 0.834, P = 0.02), vs GM SNR  and vs WM SNR . A strong correlation was also observed between the visibility of GM and 2D image quality . For 3D MEDIC, such correlations were not statistically significant. A medium strength correlation was found between the visibility of GM and the image quality . These figures are summarised in Table Positive and strong correlations were found between the visibility of the GM in 2D MEDIC vs GM/WM CNR  of acquisition time.The characterisation of 2D/3D MEDIC sequences is important for selecting the correct protocol for measuring the internal cord structures enabling accurate diagnosis, prognosis and monitoring of therapy.2D and 3D MEDIC data showed that the SNR, CNR and visual anatomical structure clarity parameters decreased from the superior to inferior of cervical spinal cord (C1‐C7) levels. These global changes may be related to the decrease of the volume of the spinal canal and increased partial volume effect from the upper cervical segments towards C7‐T1.It is important to note that image quality depends not only on high SNR and CNR but also on the visibility of the regions of interest and the absence of image artefacts. Overall, the 3D MEDIC has a lower image quality, a lower Non‐Uniformity and higher variabilities in the SNR and CNR levels (higher standard deviation) compared to the 2D MEDIC. The quantitative SNR and CNR parameters both showed strong correlations with the visibility of the GM structure in the 2D MEDIC, but not in the 3D MEDIC. There were strong correlations between the image quality (the absence of image artefacts) and the visibility of the GM structures in both 3D and 3D MEDIC. This data indicates that although 3D MEDIC can produce high SNR and CNR, it could not sufficiently provide clear visualisation of the spinal cord GM structures.3D MEDIC images contained more motion artefacts than the 2D. The physiological movement in the spinal cord imaging is typically more problematic compared to brain imaging. The cord’s proximity to the lungs, throat and oesophagus is the major contributing factor. Further, motion artefacts are exacerbated in 3D datasets due to sensitivity to phase encoding errors, in addition to a typically longer acquisition time compared with 2D.Further improvements of the 3D MEDIC are required to reduce artefacts and scan time. These may include obtaining a smaller slab for specific levels of cervical imaging and applying a gating image technique ; using non‐Cartesian k‐space ordering, spiral or blade; or using a parallel imaging with a neck coil.2D MEDIC produced superior images for visualising the internal architecture of the cervical spinal cord compared to 3D MEDIC, as the latter was more prone to movement artefacts. Further development of 3D MEDIC is required before it can be used for routine clinical imaging in the cervical spinal cord.The authors declare no conflict of interest.Supporting Information: Planning for 2D and 3D MEDIC; Image Portfolio.Click here for additional data file.


Three structure‐types of interest for (Sn5Sb3)3− were identified by DFT calculations: one that matched the X‐ray diffraction data, and two that that were reminiscent of fragments of known clusters. A study on the isoelectronic series of clusters, (SnxSb8−x)2−x (x=0–8), showed that the relative energies of these three isomers vary significantly with composition (independent of electron count) and that each is the global minimum at least once within the series.The pseudo‐element concept, in its most general formulation, states that isoelectronic atoms form equal numbers of bonds. Hence, clusters such as Zintl ions usually retain their structure upon isoelectronic replacement of some or all atoms. Here, a deviation from this common observation is presented, namely the formation of 3− (1), was synthesized as its [nBu4P]+ salt. Calculations on the isoelectronic series (SnxSbx8−)x2− (x=0–8) were performed to investigate possible alternative structures of 1, which revealed that the preferred structures of the isomers vary significantly with composition, independent of electron count. The investigation of metal clusters provides a window into the initial steps in the formation of metal nanoparticles or even bulk metal in general. Even though the molecular scale does not inform exactly about the metallic state, the formation of first bonds and the structures of seed clusters play a crucial role for the subsequent growth of a particle. As such, the isolation and thorough analysis of different types of metal clusters has been a very active field over the years.closo, nido, arachno, and hypho are given to clusters with 0, 1, 2, and 3 missing vertices and cluster skeletal electron (SE) counts of 2n+2, 2n+4, 2n+6, and 2n+8, where n is the number of actual cluster vertices. Thus far, deltahedral Zintl ions with 4–7, 9, 10, and 12 vertices have been crystallized and structurally characterized as their respective salts from ethylenediamine (en) or liquid ammonia solutions 5−, which was synthesized in liquid ammonia and its high charge density compensated for by close contacts with Rb+ cations.arachno.Most of Zintl clusters isolated by solution means are of the 3Bi5)3− and (Sn4Bi4)4− were synthesized by extraction of “RbSnBi” in liquid ammonia.73− , but they are bimetallic (Sn/Bi) and exhibit an additional tin atom capping one side  Zintl phases contain {Sn86−} subunits with square antiprism structures, which are capped on either side by Li+ cations , and two missing vertices relative to the parent deltahedron (discounting the Li+ cations). A hypothetical closo‐type Zintl cluster with 8 atoms would have 18 SEs and adopt a trigonal dodecahedral structure. While there are no such homoatomic examples, the heterometallic cluster [Bi4Ni4(CO)6]2− was shown to have this structure, and indeed comprises 18 SEs 3} fragments, and 2 from the charge).There are published examples of non‐deltahedral Zintl ions, clusters within Zintl phases obtained by solid state approaches, and heterometallic anions with 8 atoms. The non‐deltahedral anions 3− (1), which is rare example of an 8‐vertex Zintl ion. A quantum chemical investigation confirmed the heretofore unknown structure of 1 to be the global minimum. The study identified two additional local minimum structure types of higher total energies that correlate to 8‐atom fragments in known, larger intermetalloid clusters. The different architectures of species with the same composition in different chemical environments prompted us to perform an expanded quantum chemical investigation of the isoelectronic series (SnxSbx8−)x2−. It revealed that the energies of these three structure types relative to each other vary greatly with stoichiometry, and that each structure type is the global minimum at least once in the series. Hence, the strict connection of valence electron count of main‐group metal clusters with their structure seems to require refinement.However, our results reveal that structural trends within isoelectronic anions of Zintl compounds can be influenced predominantly by the actual composition, independent of electron count. In this work, we present the X‐ray crystallographic and spectroscopic characterization of 1 was isolated as a component of the highly air and moisture sensitive salt [nBu4P]31, which crystallized in low yield from a concentrated mixture of [nBu4P]Br and K2SnSb in en (see the Supporting Information for details). Analysis by single crystal X‐ray diffraction (SCXRD) revealed a salt comprising three tetrabutylphosphonium cations and an anion comprising eight tin or antimony atoms that formed a cluster with seven 3‐atom faces and adjacent 4‐ and 5‐atom faces 3− for the anion was further supported by the number of SEs  matching that of an arachno classification, and thus the observed structure.The binary Zintl anion 5Sb3)3−, but rather a mixture of anions of lower charge. Mass spectral characterization of a 2:1 mixture of [nBu4P]Br and K2SnSb in en revealed the presence of (Sn3Sb5)1− and (Sn4Sb4)2−, both of which are isoelectronic with 1, in addition to (Sn2Sb2)2− and (Sn6Sb3)1− 3− composition for 1, as well as to determine its global minimum structure, we conducted a quantum chemical study using a genetic algorithm (GA) extended by reassignment of atom‐type positions by first‐order perturbation theory in the nuclear charge (RP), denominated as GA‐RP in this combination (see methods section for details).7Sb1)3−, (Sn5Sb3)3−, and (Sn3Sb5)3−. The global minima identified for (Sn7Sb1)3− and (Sn3Sb5)3− resemble distorted deltahedra and capped nortricyclane structures, respectively . The latter structure is known from the bismuth analogue, (Sn3Bi5)3−.5Sb3)3− that closely matched the crystallographic data 3− occupy the positions with contacts to only three other atoms, as expected for pnictogens. Thus, the quantum chemical calculations, crystallographic data, and X‐ray fluorescence spectroscopic data all support a formulation of [nBu4P]3(Sn5Sb3) for the isolated red crystals.To further corroborate the evidence for a Sn5Sb3− compos1, the GA‐RP study also identified two other STs as local minima. The second most stable ST according to the GA‐RP analysis , comprises five 3‐atom and two 4‐atom faces, as well as one 5‐atom face  was a square antiprism }]2−,8}2+ in (CuBi8)[AlCl4]3,8}6− in Rb4Li2Sn8,4Sb4}2− in [Co@Sn6Sb6]3− 2]2− has a remarkably similar 8‐vertex core.− moieties as 2−e− donors leads to the expected SE count of 22. Most notably, however, the global minimum isomer of the heterometallic dimer, [Cu2Sn10Sb6]4−  isoelectronic and structurally related moieties. Square anti‐prism motifs (ST3) are found in a number of related compounds, such as {Tl1 (ST1). Instead, the square anti‐prism (ST3) is the most commonly observed motif for such moieties with 22 SEs, but this structure type is significantly less stable than ST1 for the (Sn5Sb3)3− anion (30.4 kJ mol−1). We suspected that the relative stability of the ST1 structure type was related to its heteroatomic composition. We therefore carried out a comprehensive GA‐RP investigation to determine the relative energies of ST1, ST2, and ST3 for a series of molecules, (SnxSbx8−)x2− (x=0–8), all of which are isoelectronic with 1.In contrast to the above‐mentioned compounds, we know of no corresponding examples of 8‐vertex cluster moieties that resemble xSbx8−)x2− . These energies were plotted relative to ST3, as this structure type was both present and undistorted for all eight stoichiometries. ST1 was also identified for all stoichiometries; however, in four instances the most stable isomer was distorted from the ideal structure x2−, independent of the number of valence electrons (in this case 38). There are three important features of these results: 1) each of the three structure types is the most stable in at least one instance, 2) ST3 is only the most stable structure type for the homoatomic ions (Sn86− and Sb82+), and 3) the energies of the most stable versions of ST1 converge on the stoichiometry of 1. Therefore, while all three isomers are arachno‐type structures, the structure that presents for (SnxSbx8−)x2−  is a function of composition. In ST3, all atom positions are equivalent, possibly explaining its favorability for the homoatomic compositions (Sb82+ and Sn86−). In contrast, ST1 has five unique atomic environments, which explains why heteroatomic effects can override the valence electron count under certain circumstances. These findings add a hitherto undefined dimension to the relationship between structure and composition for Zintl ions. We note in passing that we also tested other electron counts  by the same method, the results of which are not detailed here, as they exceed the scope of this work. However, it is briefly stated here that our findings are consistent in the sense that there is no single global minimum structure across these isoelectronic series.Figure arachno‐type Zintl anion obtained from solution synthesis, which is also a rare example of such a cluster having 8‐vertices. Quantum chemical considerations of all potential compositions (SnxSbx8−)x2− (x=0–8) not only supported the composition of 1 to be (Sn5Sb3)3−, but also indicated that isoelectronic anions in this case do not prefer the same architectures, but rather exhibit different minimum structures. This is a new facet of the pseudo‐element concept, which usually suggests equivalent structures for isoelectronic molecules.In conclusion, we report the synthesis and characterization of a phosphonium salt of the first The authors declare no conflict of interest.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.


In the Abstract, the change in hemoglobin A1c in the placebo group should have been 0.04 percentage points. In Table 2, the P value for the Matsuda index should have been .10. The first paragraph of the Discussion should have referred to a 0.5% decrease in body fat mass and a 0.04–percentage increase in hemoglobin A1c in the group that received placebo and lifestyle intervention. This article has been corrected.1In the Original Investigation titled “Effect of Bimagrumab vs Placebo on Body Fat Mass Among Adults With Type 2 Diabetes and Obesity: A Phase 2 Randomized Clinical Trial,”


Myelodysplastic syndrome (MDS) is a heterogeneous clonal disease originated from hematopoietic stem cells. Epigenetic studies had demonstrated that DNA methylation and histone acetylation were abnormal in MDS. Azacitidine is an effective drug in the treatment of demethylation.RT‐PCR was performed to determine GADD45γ in 15 MDS clinical samples. Myelodysplastic syndrome cell lines SKM‐1 and HS‐5 were transfected with GADD45γ eukaryotic expression vector and/or GADD45γ shRNA interference plasmid, and treated with azacitidine. Proliferation and apoptosis were examined by CCK‐8 and Western blot analysis to confirm the function role of GADD45γ and azacitidine. The methylation level of GADD45γ gene was detected by bisulfite conversion and PCR.This study found that GADD45γ gene was down‐expressed in MDS patients' bone marrow and MDS cell lines, and the down‐regulation of GADD45γ in MDS could inhibit MDS cell apoptosis and promote proliferation. Azacitidine, a demethylation drug, could restore the expression of GADD45γ in MDS cells and inhibit the proliferation of MDS cells by inducing apoptosis, which was related to prognosis and transformation.This study indicated that GADD45γ was expected to become a new target of MDS‐targeted therapy. The findings of this study provided a new direction for the research and development of new MDS clinical drugs, and gave a new idea for the development of MDS demethylation drug to realize precise treatment. Azacitidine Induce MDS cell apoptosis. Myelodysplastic syndrome is a heterogeneous clonal stem cell disease of blood and bone marrow characterized by low hematopoietic function, which can lead to lethality or acute myeloid leukemia (AML). Its clinical manifestations were peripheral blood cell decrease, peripheral blood and bone marrow dysplasia/fibroblast, and clonal cytogenetic abnormality. The typical diagnosis was based on the presence of persistent cytopenia, dysplastic cells, and genetic markers. Common clinical problems included the diagnosis of MDS, the lack of new MDS drugs confirmation methods, and the lack of long‐term prospective randomized MDS clinical control to guide allogeneic blood and bone marrow transplantation.DNA methylation, or the covalent addition of a methyl group to cytosine within the context of the CpG dinucleotide, had been widely found in mammalian genome. These effects included transcriptional repression and chromatin remodeling, X chromosome inactivation, and parasitic DNA suppression. Normal methylation patterns were frequently disrupted in tumor cells, and the promoter of a tumor suppressor gene was hypermethylation within gene silence and cell deletions or mutations.Azacitidine (AZA) was the first drug approved by the US Food and Drug Administration (FDA) (May 2004) for the treatment of MDS, and had been granted the status of orphan drug. Azacitidine (Vidaza) had been approved by the European Union for use in patients with high‐risk MDS and AML.Based on the representative difference analysis of methylation sensitivity and 5‐aza‐2v‐deoxycytidine demethylation, CpG island of GADD45γ (Growth Arrest and DNA Damage 45γ) was the target sequence of hypermethylation gene. Like other GADD45 members, GADD45γ was widely expressed in all normal adult and fetal tissues. GADD45γ could inhibit cell growth and induce apoptosis in shock. The results showed that the ectopic expression of GADD45γ strongly inhibited the growth and colony formation of tumor cells in silenced cell lines.The molecular mechanism of 5‐aza‐2‐deoxycytidine (5‐aza‐2‐deoxycytidine) in multiple myeloma (MM) was to upregulate a large number of tumor‐related genes silenced by epigenetic genes.In this study, the expression of GADD45γ in MDS clinical samples was detected. We constructed GADD45γ eukaryotic expression vector and GADD45γ shRNA interference plasmid, and transfected MDS cell line SKM‐1 and American ATCC mouse normal bone marrow cell line (class B) HS‐5, respectively, to study the effect of GADD45γ on cell proliferation and apoptosis. Using tetracycline on gene expression system, the MDS cell line SKM‐1 was induced to overexpress GADD45γ by azacitidine. The effect of overexpression of GADD45γ on the proliferation of MDS cells in vitro was observed. In order to further understand the role of GADD45γ in MDS, to explore whether the gene can be a biomarker for predicting MDS demethylation drug treatment, and to provide new ideas for the research and development of MDS clinical new drugs and promoting the development of MDS precise treatment.22.1Sample collection: A total of 15 bone marrow samples from patients with MDS diagnosed for the first time at The First Affiliated Hospital of Bengbu Medical College from March 2018 to March 2019 were enrolled into this study. There are 8 men and 7 women with the mean age of 58.2 ± 9.7 years. Refer to the standard of diagnosis and curative effect of hematopathy for the diagnosis standard, and take 10 ml of bone marrow samples. This study was approved by the Human Ethics Committees Review Board at the The First Affiliated Hospital of Bengbu Medical College (S2018071).Cell lines and reagents: MDS cell line SKM‐1 and human normal bone marrow cell line HS‐5 were purchased from ATCC (USA).2.22 saturated humidity until the logarithmic growth period.The cells were cultured in RPMI 1640 medium containing 10% fetal bovine serum and placed in a cell incubator at 37°C and 5% CO2.3Referring to the GADD45γ base sequence of GenBank mice, the GADD45γ primer (F forward: 5′‐TCTACGAGTCCGCCAAAGTC‐3′ and R forward: 5′‐GCACTTGCCACTGGTGTAGA‐3′) was designed by using primer premier 5.0. The total RNA of HS‐5 was extracted by Trizol method, took the oligo d(T) 18 as the reverse primer, took the extracted total RNA as the template, and reversed recorded the cDNA. Taking 1 μL DNA as template, the target gene was amplified by TaKaRa Ex TaqDNA polymerase. The PCR product was electrophoretic in 1.5% agarose gel, and the recovery procedure was purified according to TaKaRa gel recovery and Purification Kit. The fragments of GADD45γ coding region and the vector were digested with Kpn I and BamH I, respectively, and the fragments of gelled harvest vector and GADD45γ were digested with T4 DNA ligase. The products were transformed into DH5a‐sensitive cells, coated with plates (resistant to ampicillin), and grown at 37°C for 16‐24 hours, and about 500 spots were grown. Four spots were picked out and dissolved in 1ml LB medium with resistance to ampicillin for 3‐4 hours. one μl of bacterial solution was taken as culture medium Four clones amplified GADD45γ fragment for PCR. The positive bacterial solution was shaken in 4 mL ampicillin resistant LB liquid medium, 37°C overnight. According to the operating procedures of the kit, p3XFLAG‐GADD45γ was extracted and purified, and the plasmids were digested by enzyme, identified by electrophoresis, and then extracted and sequenced.2.4http://www.sigmaaldrich.com/, and the GFP shRNA oligos included the sequence of sh‐GADD45γ in the experimental group and the sequence of shGFP in the control group. The sequence was synthesized by Shanghai biotechnology. The plasmid pLKO.1‐TRC was digested by EcoR I and Age I, the digested plasmid was recovered, and the double‐stranded interference sequence formed by annealing was linked by T4 DNA ligase and then transferred into human Stbl3 supersensitive cells for bacterial liquid PCR screening. The positive bacterial liquid was taken and then expanded for culture. Plasmid extraction was used to obtain a pure lentivirus plasmid.The GADD45γ shRNA compatible with pLKO.1 plasmid was searched at 2.5TM 2000. After incubation for 6 hours, the protein and RNA were extracted, respectively. LipofectamineTM 2000 was replaced by DMEM containing 10% fetal bovine serum for further culture.The MDS cell line SKM‐1 was inoculated into a 6‐well plate for cell culture. When the cell fusion rate reached 70%‐80% in 24 hours, the cells were transfected with p3XFLAG‐GADD45γ, p3XFLAG (as negative control), pLKO.1‐shRNA, and pLKO.1‐shGFP at a concentration of 2.5:1 by Lipofectamine2.6TM 2000, and the cells were cultured for 72 hours. The third‐generation HS‐5 cells were inoculated on the 6‐well plate, and the cell fusion rate reached 60%‐70%. The qPCR primer sequences were listed in Table MDS cells were inoculated on the 6‐well plate. When the cell fusion rate reached 70%‐80%, p3XFLAG‐GADD45γ plasmid and p3XFLAG plasmid were transfected with Lipofectamine2.7TM 2000. Seventy‐two hours later, the third‐generation FDC‐P1 was inoculated on the 6‐well plate, and the fusion degree of the cells was 60%‐70%. When the lentivirus was infected, the culture medium containing polyamine was changed, and 500 μL lentivirus solution was added into each hole, so that the final concentration of polyamine was 8 μg/mL, 48 hours, and the minimum killing concentration of puromycin was selected to stabilize the interfering cell lines. The 2nd generation was continuously cultured, and the protein lysate was dissolved in 30 minutes by ice bath and centrifugated, and then, the 50 g protein thereof was extracted by dodecyl sulfonate‐polyacrylamide gel electrophoresis. The wet spinning method was transferred to the polyvinylidene fluoride membrane. The 5% skimmed milk powder was sealed at room temperature, and the 1H was added at room temperature . Caspase‐3, Caspase‐7, and Caspase‐9 were diluted with 1:1000 and incubated overnight at 4°C. After TBST washing, HRP‐labeled second antibody (diluted with 1:5000) was added. After incubation for 1H at room temperature, TBST membrane was rinsed for three times, the positive bands were displayed with chemiluminescent reagent, and the images were processed and analyzed with gray‐scale analysis software.The MDS cell line SKM‐1 was inoculated on the 6‐well plate. When the cell confluence was 70%‐80%, the p3XFLAG‐GADD45γ plasmid and p3XFLAG plasmid were transfected with Lipofectamine2.83 cells/mL. the control group was set up with 5 multiple wells in each group. After incubation for 48 hours, CCK‐8 of 10 μL was added to continue incubation for 2 hours. The absorbance (a) value of each hole was measured at 450 nm of enzyme‐linked immunosorbent assay. Calculate the survival rate of those cells.CCK‐8 method was used to detect the cell survival rate. SKM‐1 cell line transfected with 24‐hours MDS and FDC‐P1 cell infected with virus were inoculated into 96‐well plate (100 μL/well) with a density of approximate 5 × 102.9The experiment was divided into 6 groups. The final concentration of azacitidine in each experimental group was set as 0, 0.25, 0.5, 0.75, 1, and 5 μmol\L, respectively. After 24 hours, the expression of Turbo RFP was observed under the inverted fluorescence microscope (Zeiss). After determining the optimal concentration of azacitidine, Western blot was used to detect the expression of GADD45γ induced by azacitidine.2.10Genomic DNA isolated from SKM‐1 cells and three controls with AZA was used for analysis of the methylation. Referring to previous literature,2.11t test or one‐way ANOVA was used to compare the groups. P < .05 means significant difference.SPSS 22.0 software was used to statistical analyze all data. All data were expressed as mean ± SD of at least three separate experiments. For the RT‐PCR or Western blot analyses, the mean ± SD was derived from triplicate measurements of one experiment. A 33.1Based on the fact that GADD45γ could inhibit tumor growth by promoting apoptosis, and it had been reported that GADD45γ has biological activity in AML treatment, this study first analyzed the expression level of GADD45γ in MDS patients' bone marrow cells. Compared the expression level of GADD45γ in human acute myeloid leukemia cells SKM‐1 and human bone marrow stromal cell line HS‐5, it was found that the expression level of GADD45γ in SKM‐1 cell line had no significant difference between bone marrow cells in MDS patients, while the expression level of GADD45γ in HS‐5 cell line was significantly higher than the former two. The results showed that the expression level of GADD45γ was not high in MDS patients (Figure 3.2After that, we studied the biological activity of GADD45γ in MDS by transient expression of GADD45γ in SKM‐1 cells or inhibition of GADD45γ protein expression by shRNA in FDC‐P1 cells. The results showed that GADD45γ was successfully expressed in SKM‐1 cell line, and the expression level was significantly higher than that in the control group. The expression of GADD45γ was successfully inhibited in FDC‐P1 cells Figure . The exp3.3Azacitidine was the first drug to treat MDS, but its mechanism needed further study. After confirming the effect of GADD45γ on MDS cell line by inducing apoptosis, we began to try to detect the change of GADD45γ protein expression level in MDS cell line affected by azacitidine. After treatment of SKM‐1 cell line with different concentration of azacitidine, we found that the proliferation of SKM‐1 cell line was significantly inhibited with the increase of azacitidine concentration, which was in direct proportion to the concentration of azacitidine. To detect the expression level of GADD45γ in SKM‐1 cell line after azacitidine treatment, we were surprised to find that with the increase of azacitidine concentration, the expression level of GADD45γ protein in the cell line also changed Figure . When th3.4In order to study how azacitidine acted on MDS cell line through GADD45γ, we further overexpressed GADD45γ in SKM‐1 cell line. The results showed that GADD45γ was overexpressed in SKM‐1 cell line, and with the increase of GADD45γ expression level, the protein expression level related to apoptosis was also increased, and the proliferation of SKM‐1 cell line was significantly inhibited (Figure Azacitidine is a classical demethylation drug. GADD45γ DNA was extracted from the experimental group and the control group. Compared with the control group, the methylation level of GADD45γ in the experimental group with azacitidine was significantly lower. So far, azacitidine can improve the expression level of GADD45γ by changing the methylation level of GADD45γ gene, promote cell apoptosis, promote MDS cell line apoptosis, and finally achieve the effect of MDS disease treatment. GADD45γ can be used as a target and biomarker for the treatment of MDS.4Through the analysis and comparison of MDS patients' bone marrow cell samples and SKM‐1 cell lines, we found that the expression level of GADD45γ protein in MDS patients was significantly lower than that of HS‐5. It was probably related to the occurrence, development, and transformation of MDS. If the bone marrow samples of healthy people could be obtained in the follow‐up study, compared with the expression level of GADD45γ in MDS patients, the role of GADD45γ in the occurrence and development of MDS could be further confirmed. In order to further analyze the role and influence of GADD45γ in the pathological process of MDS, the expression of GADD45γ in FDC‐P1 was silenced, resulting in accelerated cell proliferation and reduced apoptosis. The recombinant expression of GADD45γ in SKM‐1 cells showed that the increase of GADD45γ expression level could promote the apoptosis of SKM‐1 cells, inhibit the proliferation of SKM‐1 cells, and have certain value for the malignant transformation and prognosis of MDS. In later research, we could investigate whether GADD45γ could participate in autophagy of MDS‐related cell lines, and the application of GADD45γ in the treatment of MDS diseases.In this study, we found that the expression of GADD45γ in MDS cell line was significantly increased when azacitidine was used as demethylation drug, and the dose of azacitidine was related to the apoptosis of MDS cell line and the expression of GADD45γ in MDS cell line. Furthermore, the overexpression of GADD45γ in SKM‐1 cell line was studied. The results showed that GADD45γ could induce the apoptosis of SKM‐1 cell line through caspase signaling pathway. When azacitidine was added, the expression level of GADD45γ in SKM‐1 cell line continued to increase, and the apoptosis was more obvious. Methylation analysis showed that the DNA methylation level of GADD45γ in SKM‐1 cell line was significantly higher than that in SKM‐1 control group with azacitidine added, while the expression level of GADD45γ in SKM‐1 cell line was significantly lower than that in SKM‐1 control group with azacitidine added, which was also confirmed in the GADD45γ overexpression system of SKM‐1 cell line, indicating that azacitidine can promote the expression of GADD45γ in MDS cell line, and the demethylation of GADD45γ could improve the expression level of GADD45γ. GADD45γ could further induce the apoptosis of MDS cell line through caspase signal pathway and finally achieve the effect of MDS treatment. Although azacitidine targeting GADD45γ had been proposed in this study to promote the apoptosis of MDS cell line through demethylation, more detailed apoptosis mechanism needs to be further studied, especially the specific cytokines involved in apoptosis signal pathway.In summary, we found the apoptosis promoting effect of GADD45γ in MDS cell line and proposed the more detailed mechanism of azacitidine increasing the expression level of GADD45γ through demethylation to inhibit MDS cell proliferation and promote apoptosis. This provides a new perspective for MDS‐targeted therapy and proposes a new potential biomarker for MDS demethylation drug therapy. In addition, the overexpression of GADD45γ is expected to become a new method for MDS‐targeted therapy.The authors declare no competing financial interests.DL conceived and supervised the research. YY designed and performed the experiments, analyzed the data, and wrote the manuscript. JL, YG, and LL analyzed the data.


Here, we describe a method using p‐H2 to hyperpolarize 29Si. The observed signal enhancements, approaching 3000‐fold at 11.7 T, would take many days of measurement for comparable results under Boltzmann conditions. The resulting signals were exploited to monitor the rapid reaction of tris(tert‐butoxy)silanol with triflic anhydride in a T1‐corrected process that allows for rapid quantification. These results demonstrate a novel route to quantify dynamic processes and intermediates in the synthesis of silicon materials.Silanols and silanes are key precursors and intermediates for the synthesis of silicon‐based materials. While their characterization and quantification by  The hyperpolarization of silanols and silanes was achieved using parahydrogen and an iridium catalyst. The resulting 29Si NMR signal gains approach a factor of 3000 and were harnessed for the quantitative monitoring of a substitution reaction. Its wide chemical shift dispersion makes it highly diagnostic for characterization purposes and allows the examination of dynamic processes in solution and the solid state.29Si NMR spectroscopy has limitations that reduce its potential use,29Si NMR signal reflects just 1 in 125 500 of these nuclei at 11.7 T. Its 4.7 % natural abundance and typically long T1 values also hinder detection.Silicon is one of the most abundant elements known to man. Silicon‐based materials find use in a wide range of applications, from the synthesis of bulk materials through to roles in molecular transformations. Of its three naturally occurring isotopes, only 29Si, a number of hyperpolarized magnetic resonance applications using dynamic nuclear polarization (DNP) have been reported.2)1H and a number of heteronuclei, including 29Si.Hyperpolarization is a route to overcome this insensitivity and refers to a situation whereby the spin energy level populations are perturbed from Boltzmann equilibrium conditions. These techniques have been utilized in both medical and analytical science, and with respect to 2‐based hyperpolarization has been greatly expanded.2(NHC)(RNH2)3]Cl as depicted in Scheme 2 and direct silane polarization by SABRE.The SABRE‐Relay techniquetert‐butoxy)silanol (IMes)] , benzylamine‐d7 , and TtBOS (50 mm) in CD2Cl2 (0.6 mL) was placed under a 3 bar atmosphere of H2. After 1 h at 298 K, the resulting 1H NMR spectrum showed clean conversion into [Ir(H)2(IMes)(BnNH2‐d7)3]Cl.tBOS binding to this iridium center was observed by NMR or MS methods. After shaking this sample under 3 bar p‐H2 for 10 s at 298 K at 70 G, it was rapidly transferred into an 11.7 T spectrometer for interrogation by 29Si NMR spectroscopy. A 29Si signal that was 82±5‐fold more intense than that in the corresponding thermally equilibrated control spectrum was detected. The transfer of hyperpolarization from the silanol 1H to the 29Si is likely to occur through both low‐field thermal mixing29Si NMR signal gain to enable in situ reaction monitoring.The Stöber process2H labeling of the NHC can result in increased levels of polarization because of reduced spin dilution and longer T1 relaxation times.d22‐1. After SABRE‐Relay transfer, an improved silanol signal gain of 92±4‐fold was observed 2(IMes)(BnNH2‐d7)3]Cl is 3.33 s−1 and therefore lower than predicted to be optimal.2, furnished with tert‐butyl groups, increases the signal gain to 128±11‐fold whereas its isotopologue, d34‐2, gave a 150±9‐fold gain. Catalyst 3, which bears the even more bulky SIMes ligand, also improved the 29Si signal gain compared to 1. Continuing with this trend, we were able to further increase the steric effects of the NHC through the use of catalysts 4 (IPr) and 5 (SIPr), which gave signal enhancements of 157±15 and 310±22, respectively. We would expect these signal enhancements to be further improved by the use of the deuterated isotopologues and are currently exploring routes to their synthesis.We began by varying the identity of the catalyst's N‐heterocyclic carbene (NHC) ligand as it has been shown to affect the observed polarization level. The selective G≠298 value of ligand dissociation for equatorially bound BnNH2 and H2 loss for the active complexes. These values were calculated as described in the Supporting Information. The barrier to H2 loss is consistently higher than that of BnNH2 dissociation for each catalyst, which is consistent with the expected dissociative mechanism 2(IMes)(BnNH2)3]Cl, gave ΔG≠298 values of 66.79 and 68.81 kJ mol−1 for BnNH2 and H2 loss, respectively. These ΔG≠298 values decrease when the steric bulk of the NHC ligand is increased across the series of catalysts 1–5. For catalyst 2, they are 66.16 and 68.56 kJ mol−1, respectively. Catalyst 5, which gave the largest 29Si signal enhancements after 10 s polarization transfer, has the lowest values of ΔG≠298 . These data confirm that lower barriers to ligand loss promote more effective SABRE‐Relay transfer. This effect is likely to be attenuated by relaxation of the NH protons of BnNH2‐d7 in the presence of [Ir(H)2(SIPr)(BnNH2‐d7)3]Cl whose T1 was now just 0.8 s at 11.7 T. Thus, rapid ligand exchange allows for the effective replenishment of the polarized transfer agent; however, if this exchange is too fast, rapid relaxation will limit hyperpolarization buildup whilst depleting the p‐H2.In order to rationalize these differences in polarization level, we calculated the Δm Figure  C. The c29Si signal lifetime of TtBOS was 138.4 s as measured by a variable flip angle pulse sequence (see the Supporting Information). As the decay of the created 29Si magnetization is slow, we postulated that the NMR signal gains could be increased if the SABRE‐Relay time was extended beyond 10 s. Consequently, an increase in signal gain to 625±34‐fold was obtained using 5 when the polarization time was extended to 50 s . We suggest that this is due to inefficient mixing of p‐H2 in solution.The polarization times were extended further by evacuating and refilling the NMR tubes containing the SABRE‐Relay solutions with p‐HtBOS are d34‐2 (5 mm), BnNH2‐d7 (50 mm), and TtBOS (30 mm) in CD2Cl2 (0.6 mL) and exposure to p‐H2 at 5 bar for 300 s at 70 G with refreshing the p‐H2 atmosphere every 60 s. This yields a total signal gain of 2852±112‐fold (2.3 %) in the 29Si NMR spectrum  with TtBOS was chosen as it has been reported as a method for functionalization of silica surfaces.T1 relaxation during the reaction and to give an immediate concentration profile as detailed in the Supporting Information.tBOS was conducted using our previously optimized conditions, prior to the introduction of a solution of Tf2O (10 equiv) and pyridine (10 equiv) in CD2Cl2 (0.1 mL). Subsequent rapid sample insertion into an 11.7 T magnetic field prior to acquisition of a 29Si spectrum every 5 s for a duration of 60 s  into its triflate derivative (δSi=−102.7 ppm). The identity of these signals was unequivocally confirmed by independent synthesis (see the Supporting Information). After an induction period of 10 s, which we attribute to diffusion of the Tf2O into the NMR detection region, the expected pseudo‐first‐order consumption of the starting silanol and the corresponding production of its triflate product was observed. The rate constant for this was determined to be 0.070±0.001 s−1 and is not affected by changing the concentration of the SABRE catalyst, which confirms that the catalyst does not participate in the nucleophilic reaction. This data would not be possible to collect using 29Si NMR spectroscopy under Boltzmann conditions because of the requirement for signal averaging and long T1 values; the speed of this reaction means that it would be complete before the first measurement could be made. When the reaction was repeated with substoichiometric quantities of Tf2O, a new resonance at δSi=−93.2 ppm was observed, which we attribute to the product of dimerization (see the Supporting Information). It is formed by reaction of TtBOS with its triflate intermediate in a two‐step process. The same signal is present in the 29Si NMR spectrum when the reaction was repeated with tris(tert‐butoxy)silyl chloride; however, the reaction is now too rapid to derive any kinetic data. As the oligomerization of silanols is a key step in the synthesis of silica materials, the result demonstrates that it may be possible to detect and quantify intermediates in the sol–gel process.DNP has previously been used for quantitative reaction rate determination using 29Si NMR spectroscopy, we also discovered a method to hyperpolarize important silanes via SABRE. When a sample containing d22‐1 (5 mm), dimethylethoxysilane (50 mm), and BnNH2‐d7 (50 mm) in CD2Cl2 (0.6 mL) was shaken at 70 G for 10 s, a hyperpolarized signal gain of 206±24‐fold was observed in the 29Si NMR spectrum as an antiphase doublet 2(d22‐IMes)(BnNH2)3]Cl,2‐derived hydride ligands, and dihydride‐η2‐silane complexes have been exemplified elsewhere.2‐silane complex could be detected.During the course of our investigation into hyperpolarized 1H–29Si INEPT based transfer sequence was utilized at 11.7 T to create the same antiphase signal as that of Figure d6 and CD3CN, did not increase the signal gains when compared to those with BnNH2‐d7. Additionally, when the sample is placed under a D2 atmosphere (3 bar) at room temperature for 24 h, a 60 % reduction in the Si−H signal was observed in the 1H NMR spectrum, thus indicating that while H/D exchange occurs, it is slow. No Si−H site exchange was observed by EXSY methods on the timescale of relaxation, which further suggests that the key intermediate is of an η2‐silane type rather than an oxidative silyl hydride, which would undergo rapid Si−H scrambling.After SABRE catalysis at 70 G, a 29Si signal gain of 252±22 in the 1H–29Si INEPT spectrum. However, a number of other silanes, such as triethoxysilane and triphenylsilane, yielded no SABRE catalysis and therefore highlight the sensitivity of this approach to the steric and electronic properties of the silane. Work is now ongoing to further characterize the intermediates involved in this process in order to broaden scope and applicability.Changing the silane to pentamethyldisiloxane gave a 2. Development of the SABRE‐Relay method29Si signal gains that approach 3000‐fold. The effects of catalyst structure and their influence on ligand exchange processes were determined through calculation of ΔG≠298 values and the influence on carrier amine T1 relaxation rates. The large polarization levels attained and the long T1 values were exploited using a relaxation‐corrected variable flip angle pulse sequence to measure kinetic data for the reaction of a silanol and Tf2O through a 29Si NMR response. Finally, silanes have been shown to be amenable to SABRE‐based polarization transfer when BnNH2‐d7 was used as a co‐ligand to give 29Si signal gains of 772±56‐fold. We propose that an iridium dihydride‐η2‐silane is the active catalyst in this process,29Si will extend more generally to other slow‐relaxing heteronuclei such that intermediate characterization by NMR spectroscopy is widely supported.In summary, we have demonstrated the hyperpolarization of silanols and silanes using p‐HThe authors declare no conflict of interest.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.


In fact, Bi14Rh3I9 is the first experimentally supported weak 3D TI. Both structures are composed of well‐defined intermetallic layers of ∞2[(Bi4Rh)3I]2+ with topologically protected electronic edge‐states. The fundamental difference between Bi14Rh3I9 and Bi12Rh3Sn3I9 lies in the composition and the arrangement of the anionic spacer. While the intermetallic 2D TI layers in Bi14Rh3I9 are isolated by ∞1[Bi2I8]2− chains, the isoelectronic substitution of bismuth(III) with tin(II) leads to ∞2[Sn3I8]2− layers as anionic spacers. First transport experiments support the 2D character of this material class and revealed metallic conductivity.Topological insulators (TIs) gained high interest due to their protected electronic surface states that allow dissipation‐free electron and information transport. In consequence, TIs are recommended as materials for spintronics and quantum computing. Yet, the number of well‐characterized TIs is rather limited. To contribute to this field of research, we focused on new bismuth‐based subiodides and recently succeeded in synthesizing a new compound Bi Insulating: Bi12Rh3Sn3I9, a weak 3D topological insulator (TI) is derived from Bi14Rh3I9, which was the first weakly coupling (“weak”) 3D TI; a bulk semiconductor that hosts protected electronic surface states that allow dissipation‐free electron and information transport due to the specific symmetries of its electronic band structure. In consequence of their topological properties, TIs are envisioned as promising candidates for high‐performance spin field‐effect transistors and quantum bits. Large efforts have been devoted to the synthesis and to the physical fundamentals of topological insulators (TIs) to investigate their intriguing physical properties.1, 2 W14Rh3I9,2+ intermetallic layer. Each of these layers was characterized as a 2D TI, if appropriate charge compensation is applied.∞1[Bi2I8]2− iodide‐bismuthate chains form an alternating stack that is weakly coupling, exhibiting a weak 3D topological character.In the recent past, our group has pursued research in TIs and has contributed to the synthesis and characterization of, for example, Bi14Rh3I9,12, 1314Rh3I9 are Bi38Pt9I14, Bi13Pt3I7 and Bi12Pt3I5.2+ intermetallic layer was considered in the calculation to reduce the structural complexity. In the case of TM=Rh, two non‐trivial energy gaps can be found near the Fermi‐energy, hence supporting the 2D TI state. Furthermore, ∞2[(Bi4X)3I]2+ layers with X=Ru, Pd, Os, Ir and Pt instead of Rh were studied theoretically, showing topologically non‐trivial energy gaps for Ir‐, Pt‐ and Pd‐based layers, while layers substituted with Os and Ru remain trivial. This prediction has triggered the research interest in further weak 3D TIs.Remarkably, the intermetallic networks of several bismuth subhalides are tolerant to electronic alterations and flexible enough to provide diffusion paths for excessive mass transports. For example, single‐crystals of the metallic subiodide Bi14Rh3I9. In particular, the new phase Bi12Rh3Sn3I9 is experimentally obtained by formal substitution of bismuth by tin in the anionic spacer of Bi14Rh3I9. By doing so, central questions arise: Does a substitution influence the band structure drastically? Will the topological character persist? If so, we might be able to achieve tuneable compositions and topological band gaps. Moreover, this could open a pathway for the inclusion of magnetic ions and thereby contribute to the current quest for magnetic topological insulators. For a proper answer to those questions, the electronic properties of Bi12Rh3Sn3I9 were studied by density‐functional theory (DFT) based calculations. Moreover, we performed first temperature‐dependent transport experiments in order to underline the high conductivity within this layered material.Herein, we focus on compositional and structural manipulation of Bi14Rh3I9 with respect to phase purity and crystal growth conditions.3 in a molar ratio of 12:3:3:9 in a fused silica ampule under vacuum. The DSC data shows five significant signals  is reached, the decomposition of Bi12Rh3Sn3I9 starts gradually.The signals were interpreted based on published data,14Rh3I9. By‐products such as BiI3 and Bi4I4 are formed as well . Bi12Rh3Sn3I9 is not perceptively sensitive to air, but should be stored under inert gas.After the DSC experiments the resulting solid shows a diffraction pattern similar to Bi3 with the composition of the title compound was ground in a ball mill, pressed to a pill, sintered at 310 °C for several days and subsequently quenched to room temperature. This treatment lead to a substantial volume increase and porosity of the pill. The chemical composition was determined by EDX which confirmed the composition Bi12Rh3Sn3I9 for microcrystalline powder as well as single crystals, except for a minor tin deficiency  with tin(II) in the anionic spacer  cation. The sum formula can be structured as follows  [Eq. The crystal structure of Bi12Rh3Sn3I9 is an iodido‐stannate layer ∞2[Sn3□I8]2− =2.99–3.04 for Bi14Rh3I9, and υ(Snspacer)=1.89–1.99 for Bi12Rh3Sn3I9 (Supporting Information Table 3). The cross‐check with opposite assignments yields no meaningful results (Supporting Information Table 4).The substitution of two bismuth(III) cations by three tin(II) cations is isoelectronic and does not change the layer charges. The assigned oxidation states are supported by the valence sums occ(Sn1)=83.6(1) %≈5/6 and occ(Sn2)=66.4(1) %≈2/3. A reasonable explanation is the following:In the crystal structure determination, the tin atoms appear to be disordered over all octahedral voids, yet not statistically with 75 % occupancy for all position. Instead, the occupancies are rather different and specialized with P6/mmm. Within the accuracy of the lattice parameters, |c. cosß|/a=1/6, that is, in orthogonal projection on the (0 0 1) plane, every sixth unit cell exactly matches. Nonetheless, the symmetry of the structure is neither trigonal nor orthorhombic, because the position of the symmetry elements of the individual layers do not match in space. Thus, a larger unit cell with c’=6c. sinß is not appropriate.The structure shows a high degree of pseudo‐symmetry. The layer symmetry of the intermetallic layer is ∞2[Sn3I8]2− spacer layer has a corrugated surface with I4 protruding by 0.29 Å from a plane defined by I2 and I3. I4 is positioned directly above and below I1, which resides in the hexagonal prismatic voids of the intermetallic network and corresponds to a “dent” in the surface of the latter (I1⋅⋅⋅I4=4.34 Å). Thereby the two types of layers interlock.The P6mm. However, this does not match the occupancies of 5/6 for Sn1 and 2/3 for Sn2. A kagome‐type spacer layer with long‐range translational order along the stacking direction would correspond to occ(Sn1)=100 % and occ(Sn2)=50 %. Kagome‐type spacer layers that are ordered within each layer but show statistical disorder along the stacking direction would correspond to occ(Sn1)=occ(Sn2)=75 %. However, another cation distribution within the iodido‐stannate layer is consistent with the refinement results: the 2‐isogonal tiling with Schläfli symbol  and rectangular plane‐group symmetry P2mm. Assuming ordered cation distribution in each layer but rotational disorder (120° and 240°) in the sequence of spacer layers, average occupancies of (100 %+75 %+75 %)/3=5/6 for Sn1 and (50 %+75 %+75 %)/3=2/3 for Sn2 result  and Sn2 (4i), respectively, providing in the mean 1.67 and 1.33 valence electrons at the respective position. Using VCA, Sn1 is replaced by the tin‐like pseudo‐atom 49.67Sn, and Sn2 by 49.33Sn. Here, the notation ZSn means that the pseudo‐atom carries the nuclear charge Z and the same number of electrons, thus guaranteeing overall charge neutrality. The advantage of this model is that it allows the use of the experimental crystal structure of Bi12Sn3Rh3I9. Its disadvantage consists in ignoring any subtle effect of disordered vacancies at the Sn positions.Model B: In this model, half of the Sn2 sites are left empty, according to a  net of tin(II) cations. All other Sn positions are completely occupied. In this way, the model contains the correct number of Sn atoms and, thus, implies a decent description of interlayer bonding. The likely present local order of the material is described correctly but is supplemented by an ordered arrangement of the vacancies that is only indirectly supported by the X‐ray data. This causes a reduction of crystal symmetry, which is now described by the space group C1m1 (no. 8). An advantage of Model B is the possibility to account for local atomic relaxation, which is expected to be of importance in the neighborhood of the vacancy. The structure details of Model B without and with relaxation are shown in the Supporting Information (Supporting Table 5), where the latter was performed without any symmetry constraint (space group P1) but under preservation of size and shape of the unit cell. The largest shift, by about 0.25 Å, is observed for I7, which is one of the atoms next to the Sn‐vacancy.DFT calculations were performed for both described structure models. Figure EF) originate from the Bi 6p and Rh 4d states of the 2D TI layer, as had been found for Bi14Rh3I9. The spacer layer provides essential contributions to the total DOS of the valence band only below −0.5 eV and to the conduction band above +1.5 eV.For the latter, only results obtained after relaxation of the atomic positions are shown here and in the following. The overall DOS of both models agree well in the whole presented energy range (main figure), while differences are visible around the top of valence band/bottom of conduction band (inset). In particular, the size of the gap amounts to about 40 meV in Model A and to about 210 meV in Model B, while the relative positions and the shapes of the conduction bands up to 1 eV are similar in both models. Relaxation of the atomic positions of Model B has only a marginal effect on the gap size, which is enhanced by 10 meV compared with the unrelaxed structure. The dominant contributions to the total DOS at and around the Fermi level /3, resemble symmetry points of a 2D hexagonal lattice but are not points of high symmetry in the present monoclinic (Model A) or triclinic (Model B) lattices. This is visible in Figure Related band structures are presented in Figure s Figure . We denoAs anticipated from the very similar DOS of both models, their band structures only differ in subtle details in the considered energy window close to the Fermi level. In particular, the four lowest conduction bands show almost the same dispersion in both models. The bands of Model A are two‐fold degenerate due to inversion symmetry, while related bands of Model B show small splitting. All bands close to the Fermi level show very small overall dispersion (<0.5 eV).We conclude this section by stating that the electronic structures provided by Model A and Model B are qualitatively the same and both models undoubtedly yield an insulating ground state. The essential quantitative difference between both models consists in the size of the gap.Z2 invariants were calculated through Fu–Kane indices.ν0; ν1, ν2, ν3)=, that is, the title compound is categorized as a weak topological insulator with the same invariants as the parent compound Bi14Rh3I9.ν0; ν1, ν2, ν3)=. We confirmed the automatized calculation of these invariants for the case of Model B by visual inspection of the Wannier centres.For the considered structure model with centres of inversion, Model A, The observed robustness of electronic structure with respect to structural details, together with the identification of identical sets of invariants in both models, provides confidence in the validity of the structure models for the determination of the topological properties.UI‐curve clearly indicates metallic behaviour  resistivity of the material measured at 300 K is as low as 2.3 Ω □14Rh3I9 leads to the new weak 3D TI Bi12Rh3Sn3I9. Thereby, the iodido‐bismuthate chains are replaced by iodido‐stannate layers [Sn3I8]2− while the intermetallic [(Bi4Rh)3I]2+ layers (2D TIs) are not subject to any modifications. DFT calculations also show a weak 3D TI character of the novel tin‐containing phase with a topological band gap of maximally 210 meV for a cation‐ordered model. The tin substitution leads to a slightly enlarged molar volume, but decreases the size of the topological band gap compared to Bi14Rh3I9. Nonetheless, layers with divalent cations are suitable spacers that efficiently prevent electronic coupling between the 2D TI layers. A thorough understanding of the crystal growth has benefited the synthesis of single crystals, which may be used for further physical studies, for example, ARPES. Furthermore, the results hitherto have shown that the composition of Bi14Rh3I9 can be altered not only theoretically,The exchange of bismuth(III) by tin(II) in the anionic spacer layer of Bip(O2)/p0<1 ppm, p(H2O)/p0 <1 ppm). Rhodium  and bismuth  were purchased from Merck. Bismuth was treated at 220 °C in a hydrogen flow to remove oxygen impurities. Bismuth(III)‐iodide  was bought from Sigma Aldrich and sublimated at 200 °C. Tin  was purchased from Merck Millipore and used without further treatment. The quality of the starting materials was evaluated by X‐ray diffraction and EDX studies.All starting materials and products were handled in an argon‐filled glove box , pressed to pellets  to ensure maximum homogeneity, and sealed in a 3 mL evacuated silica ampule. After the heat treatment, the ampule was cooled to room temperature at a rate of −5 K min−1. The growth of larger Bi12Rh3Sn3I9 crystals was carried out in analogy to the procedure used for Bi14Rh3I9.−1. The sample was held at 720 °C for at least 10 minutes, followed by cooling to 420 °C at the rate of −2 K min−1, where the temperature was kept for further 20 minutes. The process was continued by cooling to 310 °C at the rate of −1 K h−1 and annealing at this temperature for approximately 7 days. In the end, the ampule was quenched in cold water.Thermal analysis: Differential Scanning Calorimetry (DSC) was performed to investigate formation and decomposition processes in the quaternary Bi‐Rh‐Sn‐I system. The starting materials in the desired ratio were sealed in a tiny silica ampule. The measurements were conducted with this ampule under equilibrium pressure using a DTA‐DSC Labsys TMA System (Setaram). The mixture was heated up to 800 °C and cooled down to room temperature with a rate of 2 or 5 K min−1.Powder and single‐crystal X‐ray diffraction: Powder X‐ray diffraction (PXRD) data  K) were collected using either an X'Pert Pro diffractometer  hybrid monochromator, fixed divergence slits, PIXcel detector) or a Stadi P diffractometer  monochromator, Dectris Mythen 1 K strip detector). The samples for PXRD measurements were ground and fixed on a single‐crystal silicon sample holder. The Rietveld‐refinement was performed with the program TOPAS[Kα radiation, λ=0.71073 Å, T=170(2) K. Numerical absorption corrections were applied based on optimized crystal descriptions. The structure was solved with direct methods and subsequent refinements against Fo2. Graphics of the crystal structures were developed with Diamond.Deposition Number 1989503 contains the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe Access Structures service www.ccdc.cam.ac.uk/structures.Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy: Scanning electron microscopy (SEM) (Ua=5–15 kV) was performed using a SU8020 electron microscope (Hitachi) equipped with multi detector system for secondary and low‐energy backscattered electrons, while an Oxford Silicon Drift Detector X‐MaxN was used for the semi‐quantitative energy‐dispersive X‐ray spectroscopyUa=20 kV). To acquire electron images, the powders were fixed on a carbon pad settled on an aluminum sample holder. To obtain the average composition by EDX, pellets of the powder (6–8 mm in diameter) were pressed and embedded into EpoThinTM2 epoxy resin (Buehler) and epoxy hardener (Buehler) under vacuum. After grinding the embedded pellets with a MetaServ 250  and subsequent polishing with a VibroMet2 , the surfaces were coated with carbon in an automatic rotary‐pump coating system (Quorum Q150R ES). To collect EDX data of a single crystal, crystals were fixed directly on a carbon film.In‐situ surface transport experiments: Four‐point probe transport experiments were performed under ultra‐high vacuum conditions at room temperature and 120 K (liquid nitrogen) by means of a four‐tip scanning tunnelling microscope (STM) system (Omicron nanoprobe system) using NaOH‐etched W tips with typical radii of 100 nm. Flakes of the samples (about 200 μm thickness) were mounted on a transferable sample plate. The W tips were navigated and positioned individually in the field of view of a SEM across the sample. This allows various probe geometries and defined probe spacings. The resistance values were corrected to calculate the conductivity of the sample. The resistivity was measured at various positions and probe currents (1—100 μA) in order to average out the effect of chemical inhomogeneities, which were partly seen in SEM. More details about surface sensitive four‐point probe measurements can be found in Ref. Computational methods: DFT based calculations were performed with the full‐potential local‐orbital (FPLO) code,−1. The final self‐consistent calculations of the charge density were carried out using the four‐component full‐relativistic mode of FPLO. This effort is necessary due to the sizable spin‐orbit coupling of all elements of the considered compound. The following basis states were treated as valence states (default FPLO basis set): Bi: 5s, 5p, 5d, 6s, 7s, 6p, 7p, 6d; Rh: 4s, 4p, 5s, 6s, 4d, 5d, 5p; Sn and I: 4s, 4p, 4d, 5s, 6s, 5p, 6p, 5d. The k‐space integrals were evaluated with the linear tetrahedron method using a k‐mesh with 12×12×7 intervals in the full Brillouin zone for all calculations.The authors declare no conflict of interest.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.


The absorbance, photoluminescence (PL) and photoluminescence excitation (PLE) spectra of CH3NH3PbI3 and PbI2 solutions were measured in various solvents and a broad concentration range. Both CH3NH3PbI3 and PbI2 solutions exhibit absorption features attributed to [PbI3]1− and [PbI4]2− complexes. Therefore, we propose a new mechanism for the formation of polymeric polyiodide plumbates in solutions of pristine PbI2. For the first time, we show that the [PbI2+n]n− species in both solutions of CH3NH3PbI3 and PbI2 exhibit a photoluminescence peak at about 760 nm. Our findings prove that the spectroscopic properties of both CH3NH3PbI3 and PbI2 solutions are dominated by coordination complexes between Pb2+ and I−. Finally, the impact of these complexes on the properties of solid‐state perovskite semiconductors is discussed in terms of defect formation and defect tolerance.In this work, we present a detailed investigation of the optical properties of hybrid perovskite building blocks, [PbI The optical properties of hybrid perovskite „building blocks” – polyiodide plumbates ([PbI2+n]n−) – formed in solutions of CH3NH3PbI3 and lead iodide are studied. This study provides a deep insight into the fundamental driving forces for [PbI2+n]n− formation in both solutions and a better understanding of the role of [PbI2+n]n− solution complexes in „defect tolerance” of hybrid perovskites. These lead‐halide‐solvent complexes act as building blocks for perovskite crystals and layers. Hence, understanding the formation mechanism of these building blocks and their properties is of key scientific interest.Stamplecoskie et al.2+n]n−. The formation of [PbI3]1− and [PbI4]2− complexes is demonstrated in solutions of CH3NH3PbI3 and pure PbI2 independent of the presence of the organic cation (CH3NH3I) and nature of the solvent. In addition, we here suggest the formation of polymeric polyiodide plumbates in solutions with high concentration of PbI2. For the first time, we report the photoluminescence (PL) and photoluminescence excitation (PLE) spectra of polyiodide plumbate solution species. Both solutions of CH3NH3PbI3 and PbI2 exhibit an emission peak at 760 nm. The emission of [PbI2+n]n− complexes exhibits a large Stokes shift compared to absorption bands, while it occurs at a similar wavelength as solid CH3NH3PbI3 thin films. This may have important implications on the defect tolerance of metal‐halide perovskite semiconductors.In this work, we present a study of the optical properties of polyiodide plumbate complexes, 1+ and [PbI2]0, respectively.excλ=300 or 320 nm that correspond to the absorption bands of these species, does not yield a significant PL, while excitation with excλ=360 nm that corresponds to the absorption band of the [PbI3]1− species, leads to the photoluminescence peak at λ=760 nm (blue dash‐dotted line). The PLE spectrum of the 0.25 mM PbI2 solution exhibits a maximum intensity at 376 nm, matching the position of the absorption bands of [PbI3]1− species in solution . Adding more MAI leads to a further increase in the intensity of the absorption band at 420 nm. This increase indicates a shift of the equilibrium towards the formation of [PbI4]2− species in the solution. Similarly to absorption, the PLE spectrum of the solution with 1 : 130 of PbI2 : MAI exhibits an increase in the PLE intensity in the long‐wavelength part of the spectrum due to the increase in [PbI4]2− concentration  was excited with excλ=470 nm into the tail of absorption band of [PbI4]2− species. The PL spectrum of the solution exhibited the PL peak at 755 nm, with only a slight broadening of the peak in the blue part of the spectrum. However, due to a significant spectral overlap of PL peaks of [PbI3]− and [PbI4]2− species, the exact deconvolution of the PL spectra is difficult. The comparison between the normalized PL, scaled PLE, and absorption spectra of 0.25 mM of PbI2 and 1 : 130 of PbI2 : MAI solutions excited with excλ=360 and 470 nm respectively is shown in Figure S2 (b).When adding methylammonium iodide (MAI) in a stoichiometric ratio of 1 : 26 relative to the 0.25 mM PbI2]0 solution species are not responsible for the emissive properties of the solutions. On the contrary, the PL peak at 760 nm at low concentrations stems mainly from [PbI3]− solution species with a contribution of [PbI4]2− species at high concentration of added I−.Based on these observations, the absorption bands related to the presence of lower coordinated 1− can be detected in the absorption spectrum. Thus, the formation of high‐order polyiodide plumbates can be expected in solutions of pure PbI2 as well as in the presence of MAI. In Figure 2 solutions in DMF are shown for different solution concentrations of 0.1, 1, 10, and 100 mM. The solution containing 0.1 mM of PbI2 in DMF showed similar optical properties as the 0.25 mM solution of PbI2  causes parasitic absorption that leads to asymmetric PLE spectra that are cut‐off at their blue edge . A further increase of the concentration leads to an increase of the absorption tail at wavelengths larger than 400 nm. This is due to the formation of [PbI4]2−. As parasitic absorption from non‐emissive solution species increases the inner filter effect, thus, only the tail of PLE spectra can be considered in the analysis of spectra evolution.Interestingly, the solution of pure lead iodide in sub‐millimolar concentrations exhibits luminescence at es of PbI1− can bees of PbI1− can bees of PbI1− can be2+n]n− solution species derived from the absorption and emission spectra investigated here are summarized in Table 1 (see Table Characteristic absorption and emission features attributed to different 0 ]0) as shown on the left side of Figure −).− ions are added to the PbI2 solution, a competitive binding can be observed between I− ions and solvent molecules (L) towards the Pb2+ ions. Even a small amount of I− ions is sufficient to replace solvent molecules and to induce the formation of polyiodide plumbate species [PbI3L3]1− in the first and [PbI4L2]2− species in the second equilibrium. This is illustrated at the top of Figure +. As a result, the evolution of spectroscopic features of the PbI2 solution with increasing MAI content can be attributed to the species [PbI2L4]0, [PbI3L3]1− and [PbI4L2]2− n. As a result, we propose the formation of polymeric polyiodide plumbates to occur in lead‐iodide precursor solutions at high concentrations, as indicated at the bottom of Figure Since the distinct absorption bands correlated with the presence of the lead‐iodide‐solvent complexes are also observed in the solutions of PbI− and PbI2− comple2L4 species. In the first equilibrium, coordination between two PbI2L4 species leads to the formation of dimers (PbI2L3)2. Polymeric (PbI2L2)n species can be formed when more PbI2L4 species are added (2nd equilibrium). The exact geometry and electronic structure of the polymeric (PbI2L2)n species is currently under intense investigation.Polymeric‐like lead‐halide‐solvent complexes can be formed through the interaction of two or more PbI2L3)2 and polymers (PbI2L2)n contain PbI3L3 and PbI4L2 structural motifs, indicated by the green shaded areas in Figure − ions PbBr3) and di‐tetraethylamine‐lead‐tetrabromide ((NEt4)2PbBr4). Yoon et al.3]1− and [PbBr4]2− complexes in solution by changing the chemical equilibrium through MABr addition to a 2.7 mM PbBr2 solution in DMF. This is similar to the experiments described above  in halide complexes of s2 metals.To unveil the origin of the emission band of species in PbIπ and pσ orbitals of a ligand (e. g. Br− or I− ions) to unoccupied antibonding pσ orbitals of the metal (here: Pb). The bromide derivatives exhibit mixing of s→p and LMCT transitions, while destabilization of sσ orbitals of the I atom likely leads to an increased contribution of LMCT transition in the emission spectrum of [PbI2+n]n−. Thus, [PbI2+n]n− complexes demonstrate strongly red‐shifted emission with the large Stokes shift. Similarly, large Stokes shifts of several 100 nm have also been observed for [PbCl3]1− and [PbCl4]2−. It has been suggested that larger complex distortion (due to the s2 lone pair) of the ground state in comparison to the excited state, where the distortion is no longer favored induces Stokes shift of up to about 200 nm.Typically, LMCT transitions involve the promotion of an electron from filled p3NH3PbI3 semiconductor. Intriguingly, in contrast to polybromide and polychloride, polyiodide plumbates actually exhibit emission features that are only about 52 meV higher in energy compared to their solid‐state CH3NH3PbX3 semiconductors . The solutions were heated at 60 °C and stirred for 12 h before measurements. Solutions of CH3NH3PbI3 precursor solutions were prepared by mixing and dissolving 1 to 1 molar ratio of methylammonium iodide (MAI) and lead iodide in DMSO. Similarly, the solutions were stirred and heated at 60 °C for 12 h before use. Solutions of PbI2 in DMF, NMP, GBL, and ACN were prepared using anhydrous solvents as described above. Thin films were deposited by spin‐coating of the precursor solution on a glass substrate at 1000 rpm for 30 s and 5000 rpm for 10 s. At the latest step of the spin‐coating, 100 μL of toluene was dropped on the spinning sample. The same procedure was used for the deposition of PbI2 thin films. All precursor solutions and films were prepared in N2 atmosphere. The PL spectra in Figure exλ=365 nm and 400 nm long‐pass filter. The PL spectra in Figure exλ=300, 320, 380, 395, and 425 nm, Δλ=5 nm by means of xenon lamp and double monochromators. To acquire the PLE spectra, the PL intensity was detected at the fixed value (755 nm) as a function of the excitation wavelength.Lead iodide solutions with different concentrations were prepared by dissolving an appropriate amount of PbIThe authors declare no conflict of interest.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.


The mechanism of this reaction is discussed and elucidated with DFT calculations. The results underline the fascinating similarity between phosphorus‐rich and isolobal carbon compounds. The new bicyclic octaphosphane 2 shows a dynamic behavior in solution and reacts with [AuCl(tht)] (tht=tetrahydrothiophene) to give a mono‐ ([AuCl(2‐κP3)], 3) and a dinuclear complex ([(AuCl)2], 4). With cis‐[PdCl2(cod)] , the chelate complex ], 5) with a different coordination mode of the ligand was obtained.Octaphosphane { The octaphosphane {cyclo‐(P4tBu3)}2 unexpectedly isomerizes to a new constitutional isomer in the presence of Lewis acidic metal salts. The mechanism of this reaction was elucidated and furthermore compared with the isolobal organic compounds (see scheme). This new octaphosphane 2,2′,2′′,2′′′,3,3′‐hexa‐tert‐butyl‐bicyclo[3.3.0]octaphosphane can coordinate up to two gold(I) chloride fragments, whereas a tricyclic complex was formed with palladium(II). Since the discovery of “Phosphabenzol”tert‐butyl‐octaphosphane (1), which reacted with [AuCl(tht)] (tht=tetrahydrothiophene) yielding mono‐, di‐, and trinuclear complexes, in which up to four phosphorus atoms of the ligand are involved in coordinating gold(I) atoms.1. Instead of coordination, the constitutional isomer octaphosphane 2 was formed upon reaction with a large variety of Lewis acidic metal salts and complexes, such as MX2 or [MX2(L)] }2 spontaneously isomerizes in solution at room temperature to the homologue of 2.3 with formation of bicyclo[3.2.1]octane as the final product  was monitored by 31P{1H} NMR spectroscopy. In each case, the conversion stopped at approximately 90 %, and no complete conversion of 1 to 2 was observed. The amount of the salt merely influenced the time until this state was reached . Conversely, under the same conditions the conversion of octaphosphane 2 stops at 10 %. These observations thus imply an equilibrium between octaphosphanes 1 and 2 in the presence of a Lewis acidic metal salt. Accordingly, octaphosphane 2 was also obtained as a side product in the synthesis of 1, which involves the two metal salts SnCl2 and MgCl2.In the case of the octaphosphane 1 and 2. Firstly, a monometallic complex (i1) is formed, in which the metal cation is coordinated by a bridge P atom and one of the tBu carrying P atoms usually involved in coordination (β‐P).tBu carrying P atom thus facilitating bond cleavage and formation to give the spirocyclic intermediate i2. In this intermediate, cleavage of the conceivable P−P bonds would either lead to a diastereomer with wrong configuration ,2 fragment showed that the reaction energies  confirms the proposed connectivity of the P8 skeleton in a C2‐symmetrical octaphosphane. All structural parameters including the P−P bond lengths between the bridgehead phosphorus atoms are in the expected range. The structure is furthermore analogous to As8tBu6 with respect to configuration and conformation. The 31P{1H} NMR spectrum of octaphosphane 2 shows three symmetrical multiplets, which could be successfully simulated as an AA′A′′A′′′BB′CC′ spin system assuming Cv2 symmetry  is large and positive indicating lone pairs of electrons directed towards each other,endo configuration of the molecule. Finally, the values are also similar to the respective ethyl‐substituted oligophosphane.δ(PA) and δ(PB) are similar to the analogues, the signal PC appears at higher field. This matches the trend for Me, Et, and iPr, in which an increasing steric demand of the substituent causes a growing shielding of this signal.The analogues of octaphosphane Cv2) compared to the solid state (C2). This was confirmed by VT NMR measurements, which showed that upon cooling, the signal of PA in the 31P{1H} NMR spectrum  appears to lose its mirror symmetry resulting in two partially overlapping multiplets. The situation is much clearer in the 1H{31P} NMR spectra , in which a proper decoalescence of the singlet of the tBu group attached to PA  was observed at −75 °C. The resulting pattern at lower temperatures is thus consistent with an AA′BB′CC′DD′ spin system (C2) matching the molecular structure in the solid state. The molecular motion responsible for the process is the libration around the bond between the bridgehead atoms (Scheme λ) by using DFT calculations . The profile  indeed shows that the molecular structure in the solid state (λ=40.6°) presents a minimum on the energy‐surface potential, whereas the Cv2‐symmetrical transition state (λ=0°) matches the average structure in solution. Furthermore, the respective activation energy of +32.6 kJ mol−1 agrees well with the experiment according to the temperature range, in which the coalescence is observed.Clearly, there is a molecular process, which causes a higher effective symmetry in solution  changes the order of relative energies, which is due to phosphorus preferring smaller bond angles than carbon. Replacing the hydrogen atom with tBu groups changes the order once again for the organophosphanes. Structure A is usually considerably less stable than the other ones due to the higher strain of the four‐membered ring. However, attractive dispersion interactions between the tBu groups stabilize this structure for the organophosphane 1. For P8tBu6 thus type A (ΔErel=28.2 kJ mol−1) and B  are the most stable structures. Nevertheless, structures D and F are only slightly higher in energy (ΔErel=41.1 and 60.4 kJ mol−1) and hence they are expected to be isolable compounds.In view of the discovery of octaphosphane 2 is able to coordinate gold(I). When 2 was reacted with one or two equivalents of [AuCl(tht)], a mononuclear complex [AuCl(2)] (3) or a dinuclear complex [(AuCl)2(2)] (4) was obtained, respectively (Scheme P3/κP3′ binding mode) resulting in a linear coordination environment with Au−P bond lengths as observed for similar complexes.3 and 4 are not significantly different from the free octaphosphane 2 besides a slightly larger dihedral angle λ, which seems to be increasing with the number of AuCl fragments (44.8° for 3 and 50.69° for 4). Mass spectrometry and elemental analysis confirm the composition of the proposed complexes.Like its constitutional isomer, octaphosphane y Scheme . The mol31P{1H} NMR spectroscopy indicates a more complex situation in solution. Thus, for 3, five multiplets with a relative intensity (Irel) of 1:2:2:2:1 were observed, whereas the spectrum of 4 showed three multiplets with Irel of 4:2:2. This is consistent with the respective solid‐state structure assuming the same libration motion as for the free octaphosphane equally causing a higher effective symmetry. Furthermore, in the 31P{1H} NMR spectrum of 3  additional signals corresponding to the free octaphosphane 2 and the bimetallic complex 4 were observed. This indicates an equilibrium in solution (Eq. (1), Scheme 1.2 was reacted with the dinuclear complex 4, the resulting NMR spectrum is identical to the one of complex 3. Furthermore, this is also supported by the crystal structure of 3, which co‐crystallized with 4 % of complex 4 (details in the Supporting Information). The situation is different for complex 4. In the 31P{1H} NMR spectrum , in addition to the signals which match the solid‐state structure, a second signal set was observed, for which we propose a constitutional isomer (Eq. (2), Scheme 4 matches well the theoretical pattern calculated from its single crystal structure data, it appears that the second isomer is only formed in solution.However, 2 with an excess of [AuCl(tht)] gave an insoluble substance, presumably, a coordination polymer. Elemental analysis indicates the formation of a tetranuclear complex [(AuCl)4(2)], and the IR spectrum showed the same characteristic vibrations of the tBu group that were observed for 2–5.The reaction of octaphosphane 2 was reacted with an excess of cis‐[PdCl2(cod)] , the chelate complex [PdCl2] (5) was obtained (Scheme A) adjacent to the bridgehead atoms in coordination , as well as a significantly shorter bond between the bridgehead phosphorus atoms. The pattern of the 31P{1H} NMR spectrum of 5  agrees well with the expected AA′BB′CC′DD′ spin system (C2 symmetry). Remarkably, the change in the chemical shift induced by coordination is enormous. Thus, the coordinating atoms (PA) are deshielded by 90.1 ppm, whereas all other nuclei experience a high‐field shift by 45.1 (PB), 39.1 (PC), and even 89.0 ppm (PD) for the bridgehead atoms. All other analytical data, namely mass spectrometry, IR spectroscopy (characteristic tBu vibrations), elemental analysis as well as 1H{31P} NMR (3 singlets) and 13C{1H,31P} NMR spectroscopy (6 singlets), are in excellent agreement with the observed structure.When octaphosphane d Scheme . The lig2 exhibits a variety of different coordination modes, as shown in complexes 3–5. The peripheral P atoms  seem to be slightly better donors. However, chelation of a metal requires the coordination of the P atoms adjacent to the bridgehead atoms . Discovery of additional coordination modes in the future are very likely. Further insights might also be gained preparing complexes with NMR‐active metals, such as 103Rh and 195Pt. These results once again show how complex the coordination chemistry of an apparently simple phosphane molecule can be.In conclusion, octaphosphane The authors declare no conflict of interest.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.


CircPRTM5 is associated with cell proliferation and migration in many kinds of malignancies. However, the functions and mechanisms of CircPRTM5 in CRC progression remain unclear. We explored the role and the mechanisms of CircPRTM5 in the development of CRC. Tissues of CRC patients and matched adjacent non‐tumour tissues were collected to evaluate the expression of CircPRTM5. The expression of CircPRTM5 in CRC tissues was significantly higher than that in adjacent tissues. The biological functions of CircPRTM5 in CRC were determined by overexpression and down‐regulation of CircPRTM5 in CRC cells in vitro and in vivo. The results indicate that knockdown of CircPRTM5 can significantly inhibit the proliferation of CRC cells. The potential mechanisms of CircPRTM5 in CRC development were identified by RT‐qPCR, Western blotting analysis and luciferase reporter assay. CircPRTM5 competitively regulates the expression of E2F3 by capillary adsorption of miR‐377. CircPRMT5 regulates CRC proliferation by regulating the expression of E2F3, which affects the expression of the cell cycle‐associated proteins cyclinD1 and CDK2. CircPRTM5 exerts critical regulatory role in CRC progression by sponging miR‐377 to induce E2F3 expression. The mortality of CRC ranks the third highest in all types of cancer, bringing a great burden to humans.Circular RNAs (circRNAs) have been known as a class of widespread and diverse endogenous small RNAs with multiple regulatory roles. CircRNAs are possessed with covalently closed loop structure that are formed from Exon ‘skipping’ and ‘direct back‐splicing’ of pre‐mRNA transcripts.In this study, we identified that circPRTM5 was frequently up‐regulated in CRC tissues and patients with higher circPRTM5 levels showed a poorer overall survival. CircPRTM5 exerts critical role in CRC by sponging miR‐377 to induce E2F3 expression and promoting cyclinD1 and CDK2 expression, which opens up a new insight into the potential treatment methods of CRC in humans.22.1Colorectal cancer samples and matched adjacent non‐tumour samples were gained from surgery patients of the Fourth Hospital of Western China. H&E stained slides were analysed in blind by pathologists. All patients were signed with written informed consent according to the Clinical Research Ethics Committee of the Fourth Hospital of Western China.2.26 cells in 0.2 mL PBS. Tumour volume and tumour weight were measured. Tumours were collected and prepared for histological examination.All procedures of animal models were approved by the Institutional Animal Care and Use of Fourth Hospital of Western China. Each group of nude mice  was injected subcutaneously with 5 × 102.32.Human CRC cell lines HCT‐116, LoVo, SW‐480, SW‐620, HT‐29 and immortalized colon epithelial cell line FHC were purchased from Cell bank of Chinese Academy of Sciences. All the cells were cultured in a DMEM medium  supplemented with 10% foetal bovine serum (Gibco) and 100 U/mL penicillin/streptomycin at 37°C in a humidified incubator containing 5% CO2.4t test was used to explain differences between two groups, and all the quantitative data were indicated as mean ± SD. For a single comparison, two‐sided P < .05 was considered as statistically significant.Statistical assay was performed by using SPSS 20.0 software (SPSS). All the experiment was performed in triplicate. Student's 33.1To investigate the expression level and location of CircPRMT5 in CRC tissues, we analysed CRC tissue samples and their matched non‐tumour tissue samples (n = 30) by using RT‐qPCR, and validated that the level of circPRMT5 was frequently elevated in CRC tissues compared with paired non‐tumour tissues Figure A. Moreov3.2We thus evaluated the biological functions of circPRMT5 in CRC by generating SW‐620‐shcircPRMT5 cells (Figure 3.3CyclinD1 and CDK2 expression when the cells overexpressed circPRMT5 (Figure CyclinD1 and CDK2 are involved in the oncogenic process of circPRMT5 in CRC.To deeply investigate the mechanism of circPRMT5 on cell growth in CRC, we examined the cell cycle‐associated proteins known to up‐regulated in CRC progression. RT‐PCR and Western bolt results showed that there was increase in 5 Figure A,B, sugg3.4CyclinD1 and CDK2 of CRC was dependent on the sponge activity of miR‐377 (Figure Evidence suggested that circPRMT5 usually act as miRNA sponge to exert its function in tumorigenesis.3.5It is reported that miR‐377 targets E2F3 in malignant tumours.4cyclinD1 and CDK2 expression.This study demonstrated that circPRMT5 was an important up‐regulation circRNA in CRC, and higher expression of circPRMT5 showed poorer survival of CRC patients. CircPRTM5 exerts critical oncogenic role in CRC by sponging miR‐377 to induce E2F3 expression and promoting cell cycle‐associated proteins cyclinD1 and CDK2. Cyclin D1 is an important cyclin to be elevated by growth factors during G1 phase of cell cycle and is considered to be a key mediator of extracellular signals that regulate cell growth.cyclin D1 and CDK2 are the key cell cycle‐related genes controlling cell proliferation, our results confirmed that circPRMT5 could promote cell proliferation of CRC via regulating cyclin D1 and CDK2 expression.Emerging evidence suggests that dysregulation of circRNAs plays a pivotal role in the development of malignancies.CyclinD1 and CDK2 of CRC was partly dependent on the sponge activity of miR‐377. These data confirmed that circPRMT5 can effectively extinguish function of miR‐377 to promote CRC progression. It is reported that miR‐377 can also directly target certain oncogenes to affect cell migration and invasion.It is well characterized that circRNAs function as miRNA sponges in the progression of tumorigenicity. To better understand the regulatory mechanism of circPRMT5 in CRC, we analysed the miRNAs known to be bound by circPRMT5, and found that miR‐377 could able to interact with circPRMT5 in CRC progression. MiR‐377 belongs to a large miRNA cluster whose expression is frequently silenced in human malignancies, such as neuroblastoma, ependymoma, gastro‐intestinal stromal tumours, osteosarcoma and prostate cancer.cyclinD1 and CDK2 expression, which opens up new insight into the potential treatment of CRC in humans.In conclusion, our study demonstrated that circPRTM5 was frequently up‐regulated in CRC tissues and patients with higher circPRTM5 levels showed a poorer overall survival. CircPRTM5 exerts critical regulatory role in CRC by sponging miR‐377 to induce E2F3 expression and promoting cell cycle‐associated proteins The authors have no conflicts of interest to disclose.BRY, KD and CHY contributed equally. WNL designed the study. SJW, KD, YX and CHY performed the in vitro experiments. KD, LLX and CC performed the in vivo experiments. SJW and JHZ analysed the data and wrote the manuscript. KD and CC evaluated the histological features. WNL supervised the study.