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  • NLM标题： Acta Crystallogr B Struct Sci Cryst Eng Mater
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  • 1.

    【2hr】Insight into the role of pre-assembly and desolvation in crystal nucleation: a case of p-nitro­benzoic acid

    包量

    机译 洞察预组装和去溶剂化在晶体成核中的作用：以对硝基­苯甲酸为例
    摘要：As one of the most important phenomena in crystallization, the crystal nucleation process has always been the focus of research. In this work, influences of pre-assembly species and the desolvation process on the crystal nucleation process were studied. p-Nitro­benzoic acid (PNBA) was taken as a model compound to investigate the relationship between solution chemistry and nucleation kinetics in seven different solvents. One unsolvated form and four solvates of PNBA were obtained and one of the solvates was newly discovered. The nucleation behaviours and nucleation kinetics of PNBA in the seven solvents were studied and analyzed. Density functional theory (DFT) and solvation energy calculation were adopted to evaluate the strength of solute–solvent interactions. Vibrational spectroscopy combined with molecular simulation was applied to reveal the pre-assembly species in the solution. Based on these results, a comprehensive understanding of the relationship between molecular structure, crystal structure, solution chemistry and nucleation dynamics was proposed and discussed. It was found that the structural similarity between solution chemistry and crystal structure, the interaction between specific sites and the overall strength of solvation will jointly affect the nucleation process.
  • 2.

    【2hr】Automated electron diffraction tomography – development and applications

    包量

    机译 自动化电子衍射层析成像技术的开发与应用
    摘要：Electron diffraction tomography (EDT) has gained increasing interest, starting with the development of automated electron diffraction tomography (ADT) which enables the collection of three-dimensional electron diffraction data from nano-sized crystals suitable for ab initio structure analysis. A basic description of the ADT method, nowadays recognized as a reliable and established method, as well as its special features and general applicability to different transmission electron microscopes is provided. In addition, the usability of ADT for crystal structure analysis of single nano-sized crystals with and without special crystallographic features, such as twinning, modulations and disorder is demonstrated.
  • 3.

    【2hr】Three differently coloured polymorphs of 36-bis­(4-chloro­phenyl)-25-di­propyl-25-di­hydro­pyrrolo­34-cpyrrole-14-dione

    包量

    机译 36-双­（4-氯­苯基）-25-二­丙基-25-二­氢吡咯并34-c吡咯-14-二酮的三种不同颜色的多晶型物
    • 作者：Hee-Soo SoShinya Matsumoto
    • 刊名：Acta Crystallographica Section B Structural Science Crystal Engineering and Materials
    • -1年第Pt 3期
    摘要：In this paper, the conformational polymorphism of a chlorinated diketo­pyrrolo­pyrrole (DPP) dye having flexible substituents in a non-hydrogen-bonding system is reported. The propyl-substituted DPP derivative (PR3C) has three polymorphic forms, each showing a different colour (red, orange and yellow). All polymorphs could be obtained concomitantly under various crystallization conditions. The results of the crystal structure analysis indicate that PR3C adopts different conformations in each polymorph. The packing effect caused by the difference in the arrangement of neighbouring molecules was found to play an important role in the occurrence of the observed polymorphism. The thermodynamic stability relationship between the three polymorphs was identified by thermal analysis and indicates that the yellow polymorph is the thermally stable form. The results indicate that the yellow form and orange form are enantiotropically related, and the other polymorph is monotropically related to the others.
  • 4.

    【2hr】Pressure-induced transformation of CH3NH3PbI3: the role of the noble-gas pressure transmitting media

    包量

    机译 压力诱导的CH3NH3PbI3转化：稀有气体压力传递介质的作用
    摘要：The photovoltaic perovskite, methyl­ammonium lead triiodide [CH3NH3PbI3 (MAPbI3)], is one of the most efficient materials for solar energy conversion. Various kinds of chemical and physical modifications have been applied to MAPbI3 towards better understanding of the relation between composition, structure, electronic properties and energy conversion efficiency of this material. Pressure is a particularly useful tool, as it can substantially reduce the interatomic spacing in this relatively soft material and cause significant modifications to the electronic structure. Application of high pressure induces changes in the crystal symmetry up to a threshold level above which it leads to amorphization. Here, a detailed structural study of MAPbI3 at high hydro­static pressures using Ne and Ar as pressure transmitting media is reported. Single-crystal X-ray diffraction experiments with synchrotron radiation at room temperature in the 0–20 GPa pressure range show that atoms of both gaseous media, Ne and Ar, are gradually incorporated into MAPbI3, thus leading to marked structural changes of the material. Specifically, Ne stabilizes the high-pressure phase of NexMAPbI3 and prevents amorphization up to 20 GPa. After releasing the pressure, the crystal has the composition of Ne0.97MAPbI3, which remains stable under ambient conditions. In contrast, above 2.4 GPa, Ar accelerates an irreversible amorphization. The distinct impacts of Ne and Ar are attributed to differences in their chemical reactivity under pressure inside the restricted space between the PbI6 octahedra.
  • 5.

    【2hr】Accurate geometrical restraints for Watson–Crick base pairs

    包量

    机译 沃森-克里克碱基对的精确几何约束
    摘要：Geometrical restraints provide key structural information for the determination of biomolecular structures at lower resolution by experimental methods such as crystallography or cryo-electron microscopy. In this work, restraint targets for nucleic acids bases are derived from three different sources and compared: small-molecule crystal structures in the Cambridge Structural Database (CSD), ultrahigh-resolution structures in the Protein Data Bank (PDB) and quantum-mechanical (QM) calculations. The best parameters are those based on CSD structures. After over two decades, the standard library of Parkinson et al. [(1996), Acta Cryst. D>52, 57–64] is still valid, but improvements are possible with the use of the current CSD database. The CSD-derived geometry is fully compatible with Watson–Crick base pairs, as comparisons with QM results for isolated and paired bases clearly show that the CSD targets closely correspond to proper base pairing. While the QM results are capable of distinguishing between single and paired bases, their level of accuracy is, on average, nearly two times lower than for the CSD-derived targets when gauged by root-mean-square deviations from ultrahigh-resolution structures in the PDB. Nevertheless, the accuracy of QM results appears sufficient to provide stereochemical targets for synthetic base pairs where no reliable experimental structural information is available. To enable future tests for this approach, QM calculations are provided for isocytosine, isoguanine and the iCiG base pair.
  • 6.

    【2hr】Nollmotzite MgUV(UVIO2)2O4F3·4H2O the first natural uranium oxide containing fluorine

    包量

    机译 斜长石Mg UV（UVIO2）2O4F3·4H2O第一种含氟的天然铀氧化物
    摘要：Nollmotzite (IMA2017-100), Mg[UV(UVIO2)2F3O4](H2O)4, is a new uranium oxide fluoride mineral found in the Clara mine, Black Forest Mountains, Germany. Electron microprobe analysis provided the empirical formula (Mg1.06Cu0.02)Σ1.08[UV(UVIO2)2O3.85F3.15][(H2O)3.69(OH)0.31]Σ4.00 based on three U and 15 O + F atoms per formula unit. Nollmotzite is monoclinic, space group Cm, with a = 7.1015 (12) Å, b = 11.7489 (17) Å, c = 8.1954 (14) Å, β = 98.087 (14)°, V = 676.98 (19) Å3 and Z = 2. The crystal structure [twinned by reticular merohedry; refined to R = 0.0369 with GoF = 1.09 for 1527 unique observed reflections, I > 3σ(I)] is based upon [UV(UVIO2)2F3O4]2– sheets of β-U3O8 topology and contains an interlayer with MgF2(H2O)4 octahedra. Adjacent sheets are linked through F–Mg–F bonds, as well as via hydrogen bonds. The presence of fluorine and pentavalent uranium in the structure of nollmotzite has potentially important implications for the safe disposal of nuclear waste.
  • 7.

    【2hr】Bond-length distributions for ions bonded to oxygen: metalloids and post-transition metals

    包量

    机译 与氧键合的离子的键长分布：准金属和过渡金属
    摘要：Bond-length distributions have been examined for 33 configurations of the metalloid ions and 56 configurations of the post-transition metal ions bonded to oxygen, for 5279 coordination polyhedra and 21 761 bond distances for the metalloid ions, and 1821 coordination polyhedra and 10 723 bond distances for the post-transition metal ions. For the metalloid and post-transition elements with lone-pair electrons, the more common oxidation state between n versus n+2 is n for Sn, Te, Tl, Pb and Bi and n+2 for As and Sb. There is no correlation between bond-valence sum and coordination number for cations with stereoactive lone-pair electrons when including secondary bonds, and both intermediate states of lone-pair stereoactivity and inert lone pairs may occur for any coordination number > [4]. Variations in mean bond length are ∼0.06–0.09 Å for strongly bonded oxyanions of metalloid and post-transition metal ions, and ∼0.1–0.3 Å for ions showing lone-pair stereoactivity. Bond-length distortion is confirmed to be a leading cause of variation in mean bond lengths for ions with stereoactive lone-pair electrons. For strongly bonded cations (i.e. oxyanions), the causes of mean bond-length variation are unclear; the most plausible cause of mean bond-length variation for these ions is the effect of structure type, i.e. stress resulting from the inability of a structure to adopt its characteristic a priori bond lengths.
  • 8.

    【2hr】Solid-state structure of cyclic dipeptides: an X-ray and computational study of cis- and trans-diketopiperazines of N-methyl-phenyl­alanine with the thia-pipecolic acids and thia-prolines

    包量

    机译 环状二肽的固态结构：N-甲基-苯基­丙氨酸的顺式和反式二酮哌嗪与硫代哌酸和硫代脯氨酸的X射线和计算研究
    摘要：Ten new crystal structures of cis and trans bicyclic diketopiperazines (DKPs) of thia-pipecolic acid (with sulfur in the β, γ or δ position) or thia-proline (with sulfur in the β or γ position) and N-methyl phenyl­alanine [(NMe)Phe]: cyclo[(β-S)Pip-(NMe)Phe], cyclo[(γ-S)Pip-(NMe)Phe], cyclo[(δ-S)Pip-(NMe)Phe], cyclo[(β-S)Pro-(NMe)Phe] and cyclo[(γ-S)Pro-(NMe)Phe] were determined with X-ray crystallography. Density functional theory calculations of these molecules in the gas phase succeed in reproducing the observed molecular conformations in the crystal remarkably well. This illustrates the weak to moderate impact of intermolecular packing forces in the absence of classical N—H⋯O hydrogen bonds. The effect of sulfur on the geometry of the DKP ring and details of amide bond non-planarity are discussed. Molecular flexibility of the DKP ring, as estimated from the calculated deformation energies of its endocyclic ring torsion angles, is not in general the decisive factor for the occurrence of multiple symmetry independent molecules in the unit cell (Z′ > 1), though in some cases a correlation is observed.
  • 9.

    【2hr】Phase transition and proton ordering at 50 K in 3-(pyridin-4-yl)pentane-24-dione

    包量

    机译 3-（吡啶-4-基）戊烷-24-二酮在50 K下的相变和质子有序化
    摘要：Single-crystal neutron diffraction experiments at 100 and 2.5 K have been performed to determine the structure of 3-(pyridin-4-yl)pentane-2,4-dione (HacacPy) with respect to its protonation pattern and to monitor a low-temperature phase transition. Solid HacacPy exists as the enol tautomer with a short intramolecular hydrogen bond. At 100 K, its donor···acceptor distance is 2.450 (8) Å and the compound adopts space group C2/c, with the N and para-C atoms of the pyridyl ring and the central C of the acetyl­acetone substituent on the twofold crystallographic axis. As a consequence of the axial symmetry, the bridging hydrogen is disordered over two symmetrically equivalent positions, and the carbon–oxygen bond distances adopt intermediate values between single and double bonds. Upon cooling, a structural phase transition to the t 2 subgroup P occurs; the resulting twins show an ordered acetyl­acetone moiety. The phase transition is fully reversible but associated with an appreciable hysteresis in the large single crystal under study: transition to the low-temperature phase requires several hours at 2.5 K and heating to 80 K is required to revert the transformation. No significant hysteresis is observed in a powder sample, in agreement with the second-order nature of the phase transition.
  • 10.

    【2hr】Mean bond-length variations in crystals for ions bonded to oxygen

    包量

    机译 与氧键合的离子的晶体平均键长变化
    摘要：Variations in mean bond length are examined in oxide and oxysalt crystals for 55 cation configurations bonded to O2−. Stepwise multiple regression analysis shows that mean bond length is correlated to bond-length distortion in 42 ion configurations at the 95% confidence level, with a mean coefficient of determination (〈R 2〉) of 0.35. Previously published correlations between mean bond length and mean coordination number of the bonded anions are found not to be of general applicability to inorganic oxide and oxysalt structures. For two of 11 ions tested for the 95% confidence level, mean bond lengths predicted using a fixed radius for O2− are significantly more accurate as those predicted using an O2− radius dependent on coordination number, and are statistically identical otherwise. As a result, the currently accepted ionic radii for O2− in different coordinations are not justified by experimental data. Previously reported correlation between mean bond length and the mean electronegativity of the cations bonded to the oxygen atoms of the coordination polyhedron is shown to be statistically insignificant; similar results are obtained with regard to ionization energy. It is shown that a priori bond lengths calculated for many ion configurations in a single structure-type leads to a high correlation between a priori and observed mean bond lengths, but a priori bond lengths calculated for a single ion configuration in many different structure-types leads to negligible correlation between a priori and observed mean bond lengths. This indicates that structure type has a major effect on mean bond length, the magnitude of which goes beyond that of the other variables analyzed here.
  • 11.

    【2hr】Intelligent Materials and Structures.

    包量

    机译 智能材料和结构。
    • 作者：Gertjan Koster
    • 刊名：Acta Crystallographica Section B Structural Science Crystal Engineering and Materials
    • -1年第Pt 6期
    摘要：
  • 12.

    【2hr】Compression of glycolide-h4 to 6 GPa

    包量

    机译 乙交酯-h4压缩至6 GPa
    摘要：This study details the structural characterization of glycolide-h4 as a function of pressure to 6 GPa using neutron powder diffraction on the PEARL instrument at ISIS Neutron and Muon source. Glycolide-h4, rather than its deuterated isotopologue, was used in this study due to the difficulty of deuteration. The low background afforded by zirconia-toughened alumina anvils nevertheless enabled the collection of data suitable for structural analysis to be obtained to a pressure of 5 GPa. Glycolide-h4 undergoes a reconstructive phase transition at 0.15 GPa to a previously identified form (II), which is stable to 6 GPa.
  • 13.

    【2hr】Atomic structures of ternary Yb–Cd–Mg icosahedral quasicrystals and a 1/1 approximant

    包量

    机译 Yb–Cd–Mg三面体二十面体准晶体的原子结构和1/1近似值
    摘要：Atomic structures of ternary icosahedral (i) Yb–Cd–Mg quasicrystals (QCs) with five different Mg contents up to 46.4 at.% and a corresponding 1/1 approximant (AP), which has a composition of Yb13.3Cd70.3Mg16.5, have been analysed by single-crystal X-ray diffraction. The structures of the iQCs were found to be isostructural to the parent i-YbCd5.7, which consists of a so-called Tsai-type rhombic triacontahedron (RTH) cluster and double Friauf polyhedron, and that of the 1/1 AP was found to be isostructural to YbCd6, which is described by a body-centred packing of the same type of RTH cluster. In the iQCs, it was found that there are three types of Cd/Mg occupation, namely, Cd preferential site, Mg preferential site and Cd/Mg mixed site, and the occupation probabilities of Mg atoms at the Mg preferential site show a saturation behaviour around the Mg content of 20 at.%. This selective Mg occupation is identified as a cause of the non-linear increase in the icosahedral lattice constant with increasing Mg content. The 1/1 AP has a similar selective Mg occupation to that of the iQCs in terms of the shell structures of the Tsai-type RTH cluster. In both iQCs and the 1/1 AP, the Mg preferential sites have a smaller number of Yb atoms among their coordination numbers. Moreover, short-range order (s.r.o.) diffuse scattering was observed on the diffraction patterns of the iQCs at the positions corresponding to a face-centred-type (F-type) icosahedral superlattice. The F-type s.r.o. was found to result from the Mg substitution.
  • 14.

    【2hr】Migrating hydrogen in 246-tri­amino­pyrimidin­ium(1+)x hydrogen trioxo­fluoro­phosphate(−)x monohydrate/246-tri­amino­pyrimidinium(2+)1–x trioxo­fluoro­phosphate(2–)1–x monohydrate (0.0 x 0.73) with changing temperature

    包量

    机译 在246-三氨基嘧啶（1+）x三氧氟磷酸盐（-）x一水合物/ 246-三氨基嘧啶（2+）1-x三氟氟磷酸盐（2-）1-x一水合物中迁移氢（0.0 x 0.73）随着温度变化
    摘要：The data of the title structure of 2,4,6-tri­amino­pyrimidinium(1+)x hydrogen trioxo­fluoro­phosphate(1−)x monohydrate/2,4,6-tri­amino­pyrimidinium(2+)1−x tri­oxo­fluoro­phosphate(2−)1−x monohydrate (0.0 < x < 0.73), with the sum formula C4H11FN5O4P, were collected in 10 K inter­vals between 290 and 150 K, as well as at 100 K. The most inter­esting feature is the presence of a moderate though still strong O—H⋯N/O⋯H—N hydrogen bond. Its bridging H atom was found to be disordered over two positions in the temperature inter­val 290–220 K, with the larger occupation towards the O atom. The occupation in the latter position decreased with decreasing temperature, though not monotonously. At 210 K and below, the difference electron-density maps showed just one maximum which was closer to the N atom. Though difference scanning calorimetry (DSC) revealed no anomaly in the inter­val 303–93 K, the dependence of the length of the unit-cell axes b and c on temperature showed a kink in the slope at about 190 K. The N⋯O distance of the mentioned hydrogen bond or the occupational parameter of the electron density of the disordered H atom indicate less pronounced anomalies for the temperatures 270 and 230 K. The cation and the anion, as well as the water mol­ecules, form layers which are parallel to (10) and which are inter­connected by O—H⋯N (in the inter­val 290–220 K), N—H⋯O and O—H⋯O hydrogen bonds of moderate strength. The layers are arranged into centrosymmetric double layers in which the F atoms are directed outwards. The layers are inter­connected by water–acid O—H⋯O hydrogen bonds, weak N—H⋯F inter­actions and π-electron ring⋯π-electron ring inter­actions. The dependence of P—F bond lengths on bonding properties of the trioxo­fluoro­phosphate or hydrogen trioxo­fluoro­phosphate anions is discussed. It has been recognized that a carbon-bonded F atom avoids participation in a hydrogen-bond pattern; however, this property seems to be also common to fluorine bonded to P, As and S, especially if an oxygen ligand is also present in a mol­ecule. The contains an overview of the determined structures with trioxo­fluoro­phosphate or hydrogen trioxo­fluoro­phosphate anions.
  • 15.

    【2hr】Effect of processing parameters on microstructural properties of lead magnesium niobates

    包量

    机译 工艺参数对铌酸铅镁微结构性能的影响
    摘要：The synchrotron powder X-ray diffraction (XRD) and subsequent detailed Rietveld analysis of lead magnesium niobate (PMN) samples were performed to study the microstructural properties of polar nanoregions (PNRs) of the R3m phase. PMN samples were synthesized under different sample processing conditions. The line profile broadening analysis of room-temperature synchrotron powder XRD patterns was performed using the multi-phase Rietveld refinement method for isotropic microstructural evaluation of different PMN samples. The two phases of perovskite PMN considered in the Rietveld refinement approach for satisfactorily fitting the XRD patterns are the paraelectric cubic phase (Pm m) and the local rhombohedral phase (R3m) which corresponds to the PNRs. It is observed that the contributions of the Gaussian component of size broadening of the polar rhombohedral phase (R3m) and the Lorentzian component of strain broadening of the paraelectric cubic phase (Pm m) are apposite for satisfactory Rietveld refinement of the synchrotron XRD data for all PMN samples. The volume-average crystallite size of PNRs (R3m phase) is almost invariant (approximately 12 nm) with increasing processing temperature while their weight percentage increases. The values of the apparent microstrain in the paraelectric cubic phase (Pm m) are larger for hot-pressed samples.
  • 16.

    【2hr】Intermetallics. Structures Properties and Statistics.

    包量

    机译 金属间化合物。结构属性和统计信息。
    • 作者：Livio Battezzati
    • 刊名：Acta Crystallographica Section B Structural Science Crystal Engineering and Materials
    • -1年第Pt 6期
    摘要：
  • 17.

    【2hr】The extended Zintl–Klemm concept ionic strength I and assessment of the relative stability of lattices using the stability enhancement ratio S

    包量

    机译 扩展的Zintl–Klemm概念离子强度I和使用稳定性增强比S评估晶格的相对稳定性
    摘要：This article examines the comparison between the classical formulations used to describe silicates and that derived from the application of the extended Zintl–Klemm concept (EZKC). The ionic strength, I, for 25 silicate lattices is calculated taking into account both formulations, and the results show that, in every single one of the examples, the ionic strength of the Zintl polyanion is higher than that of the classical model which assigns a formal charge of 4+ for silicon. Our earlier study, firstly applied to the germanate (NH4)2Ge[6][Ge[4] 6O15] [Vegas & Jenkins (2017). Acta Cryst. B>73, 94–100] and to the polyanion [Ge[4] 6O15]6− equivalent to the pseudo-As2O5 derived from it, explained satisfactorily the charge transfer that takes place in the Zintl compounds. The value of I = ½∑nizi 2 for the Zintl polyanion was greater than for the compound as formulated in the classical way. In that article, a meaningful relationship was found between the electron transfers as defined by the EZKC and the ionic strength I of the anion [Ge[4] 6O15]6− ≡ Ψ-As2O5. Because the ionic strength, I, of a lattice is directly proportional to the lattice potential energy, U POT, the higher the I the greater the U POT; thus it is harder to break up the lattice into its constituent ions and hence the lattice itself is more stable, giving support to the idea that the application of the EZKC and the resulting electron shifts yields structures which are inherently thermodynamically more stable than the starting configuration.
  • 18.

    【2hr】Orientational order-disorder γ ↔ β ↔ α′ ↔ α phase transitions in Sr2B2O5 pyroborate and crystal structures of β and α phases

    包量

    机译 Sr2B2O5焦硼酸盐中的有序无序γ↔β↔α′↔α相变和β和α相的晶体结构
    摘要：Crystal structures of γ-, β- and α-Sr2B2O5 polymorphs resulting from the γ ↔ (at 565 K) β ↔ (at 637 K) α′ ↔ (at 651 K) α sequence of reversible first-order phase transitions are studied by high-temperature single-crystal X-ray diffraction, high-temperature X-ray powder diffraction, differential scanning calorimetry and impedance spectroscopy. Out of these phases, the structure of γ-Sr2B2O5 was already known whereas the structures of β- and α-Sr2B2O5 were determined for the first time. The sequence of phase transitions is associated with an unusual change of symmetry, with triclinic intermediate β-Sr2B2O5 phase and monoclinic low-temperature γ-Sr2B2O5 as well as high-temperature α-Sr2B2O5 phase. Taking the α-Sr2B2O5 phase with space group P21/c as a parent structure, the γ-Sr2B2O5 phase was refined as a twofold superstructure with symmetry P21/c, whereas the β-Sr2B2O5 phase was a sixfold superstructure with symmetry P . To construct a unified structure model for all Sr2B2O5 modifications, phases of γ- and β-Sr2B2O5 were also refined as commensurately modulated structures using the basic unit cell of the parent α-Sr2B2O5. The phase transitions are related to the orientational order–disorder arrangement of B2O5 pyroborate groups, where the degree of disorder grows towards the high-temperature phase. Thermal expansion is strongly anisotropic and dictated by preferable orientations of BO3 triangles in the structure. The intermediate phase α′-Sr2B2O5, stable over a narrow temperature range (637–651 K), features the largest anisotropy of expansion for the known borates: α11 = 205, α22 = 57, α33 = −81 × 10−6 K−1.
  • 19.

    【2hr】A review of the oxidation–pressure concept (OPC) and extended Zintl–Klemm concept (EZKC) and the emergence of the high-pressure Ni2In-type phase of lithium sulfide (Li2S) rationalized by reference to a newly defined stability enhancement ratio (S)

    包量

    机译 回顾了氧化压力概念（OPC）和扩展的Zintl–Klemm概念（EZKC）以及通过参考新定义的稳定性增强比合理化的高压硫化锂（Li2S）Ni2In型相的出现（ S）
    摘要：Taking into account new experimental data [Barkalov et al. (2016). Solid State Sci. >61, 220–224] on the pressure-induced Ni2In phase of Li2S, at 30 GPa, three concepts related to high-pressure phase transitions are reviewed here. This paper firstly reviews evidence that chemical oxidation (by inclusion of oxygen atoms) can produce a similar effect to the application of physical high pressure and temperature, in an effect labelled as the oxidation–pressure concept. Secondly, the pressure-induced Ni2In phase of Li2S is the final phase in the double transition antifluorite → anticotunnite → Ni2In, as is observed in other alkali metal sulfides. This new phase for Li2S could be expected after knowledge of the high-pressure Cmcm phase of Li2SO4, which is a distortion of the hexagonal I-Na2SO4 phase, both having M 2S subarrays of the Ni2In-type. Thirdly, in order to clarify these links, a simple methodology is proposed for gauging the level of increased stability (by defining a stability enhancement ratio, S) when the extended Zintl–Klemm concept (EZKC) has been applied. The method uses relative values of the lattice potential energies estimated for Li2S and for the pseudo-lattice Ψ-BeS derived by applying the EZKC to Li2S, after which, Li2S can be reformulated as Li+[LiS]− ≡ Li+[Ψ-BeS].
  • 20.

    【2hr】Conformational and structural diversity of iridium di­methyl sulfoxide complexes

    包量

    机译 铱二­甲基亚砜配合物的构象和结构多样性
    摘要：Transition metal complexes containing dimethyl sulfoxide (DMSO) are important precursors in catalysis and metallodrugs. Understanding the solid-state supramolecular structure is crucial for predicting the properties and biological activity of the material. Several crystalline phases of DMSO-coordinated iridium anions with different cations, potassium (1a) and n-butyl­ammonium (1b), were obtained and their structures determined by X-ray crystallography. Compound (1a) is present in two solvatomorphic forms: α and β; the β form contains disordered solvent water. In addition, the structures exhibit different rotamers of the trans-[IrCl4(DMSO)2]− anion with the trans-DMSO ligands being oriented in anti and gauche conformations. In consideration of these various conformers, the effects of the crystallized solvent and intermolecular interactions on the conformational preferences of the anion are discussed. In addition, density functional theory calculations were used to investigate the energies of the anions in the different conformations. It was found that hydrogen bonds between water and the DMSO complex stabilize the gauche conformation which is the least stable form of the trans-DMSO complex. Consequently, by controlling the number of hydrogen-bond donors and acceptors and the amount of water, it may be possible to obtain different solvatomorphs of clinically significant metallodrugs.
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