Acta crystallographica Section B, Structural science, crystal engineering and materials最新文献

We report the structural and dielectric characterization of anilinium tetrafluoroborate (AnBF₄), a molecular crystal identified as a candidate for symmetry-raising phase transitions using the FERROSCOPE routine. Variable-temperature powder X-ray diffraction and differential scanning calorimetry revealed a sequence of three structural phase transitions between room temperature and 490 K, yielding four polymorphs (A-D), three of which are previously unreported. All structures were solved either by single-crystal X-ray diffraction or ab initio from powder diffraction data. Single crystal experiments indicate diffuse scatter in polymorph C which can be related to the structural changes between the different polymorphs. The structural transitions have been rationalized using group-subgroup relationships. Dielectric measurements show a temperature-dependent response consistent with the structural changes, with the A to B transitions associated with a peak in the dielectric constant.

Flocculosin A is a strong antifungal metabolite secreted by the Basidiomycota fungus Anthracocystis flocculosa (formerly Pseudozyma flocculosa). It crystallizes in the form of long, soft cotton-wool-like needles, usually observed together with the mycelium in liquid culture conditions. Many crystallization tests were carried out. Among them, only a very slow cooling technique was able to yield suitable crystals, which were needle-like with a maximum thickness of 5 µm and several millimetres long. These crystals permitted us to record single-crystal X-ray diffraction data and solve the crystal structure as well as to determine the absolute configurations of the three chiral centres present in the two lipid chains.

The interaction of silicene with MoS₂ surfaces has an important role in determining many properties of these systems. However, the intricate nature of silicene-based systems presents significant challenges for both experimental and computational investigations, often resulting in conflicting reports in the literature. Using molecular dynamics simulations with hybrid potentials, this work investigates the epitaxial growth of silicene on an MoS₂ substrate using a vapor-deposition-like method. The findings reveal that silicene can achieve stability on an MoS₂ substrate in an AB low-buckled configuration when both van der Waals and covalent interactions are considered. In this configuration, the silicene layer exhibits numerous defects, which can be significantly reduced by increasing the substrate temperature. In contrast, when only van der Waals interactions are accounted for, the system becomes unstable, leading to the collapse of the silicene structure into a three-dimensional disordered arrangement of Si atoms. A similar instability is observed in a heterostructure where a silicene sheet is intercalated between two MoS₂ layers. These results, combined with the lattice mismatch observed between silicene and MoS₂, suggest that van der Waals interactions alone are insufficient to ensure the mechanical stability of silicene.

Three novel Schiff base ligands were synthesized through the condensation reaction of 2-(methylamino) or 2-(ethylamino)benzaldehyde with ethylenediamine and 4-nitro-1,2-phenylenediamine, respectively. The resulting Schiff bases were thoroughly characterized using FTIR, ¹H NMR and UV-vis spectroscopies, and their crystal structures were elucidated through single-crystal X-ray diffraction. Additionally, computational methods based on noncovalent interaction index and quantum theory of atoms in molecules were employed to investigate the intra- and intermolecular interactions in the molecular structure and crystal packing. The origin of the electronic transitions in UV-vis spectra of the Schiff base ligands were also investigated using time-dependent density functional theory along with the electron density difference map. Furthermore, energy decomposition analysis combined with natural orbitals for chemical valence theory has been performed to estimate the pairwise interaction energies in the dimer associates aggregated by the intermolecular interactions in the Schiff base ligands.

High-resolution synchrotron X-ray diffraction data confirm the stabilization of the average structure at ambient temperatures as a defect fluorite structure in ternary and quaternary oxides of Bi₂O₃, where some Bi cations are replaced with Dy³⁺ and/or Er³⁺, Nb⁵⁺ and W⁶⁺. Rietveld refinement of the diffraction data indicates that when the larger cation Er³⁺ (0.89 Å) is replaced with smaller cations W⁶⁺ (0.42 Å) and/or Nb⁵⁺ (0.48 Å), the unit-cell parameter a, based on the relative ionic radii of the substituents, counterintuitively increases. Total scattering data show that the identity of the cation substituent is important in determining the positions of some Bi cations in the defect fluorite structure. Er³⁺ and Dy³⁺ cations induce monoclinic-like distortions that extend only locally in the Bi³⁺ sublattice. X-ray absorption spectroscopy provides evidence that some Dy cations, in the δ phases, prefer to keep a similar local environment to that in the parent Dy₂O₃. W cations are found to be predominantly tetrahedrally coordinated in the δ phases explored in this work.

tert-Butylcalix[6]arene (TBC6) exhibits a rich crystal energy landscape, with structural diversity driven by macrocycle conformation, guest inclusion and self-assembly. Using multicomponent crystallization mixtures containing DMSO and additional solvents (e.g. DMF, chlorobenzene, 1,2-dichlorobenzene, anisole, THF), we obtained seven new TBC6 solvates. One structure, crystallized in the presence of pyridine, adopts a winged-cone conformation with a bilayer arrangement in the crystal. The remaining six are isostructural and feature a columnar packing of TBC6 in a 1,2,3-alternate conformation stabilized by four strong interactions with DMSO: two hydrogen bonds and two C-H...π interactions. Notably, DMSO in the TBC6 cavity is released at elevated temperatures (∼200°C), consistent with its stronger binding energy as calculated using DFT methods. TBC6-TBC6 interactions, both within and between columns, dominate the crystal packing, with intracolumnar contacts contributing twice as much stabilization as intercolumnar ones, where additional solvent guests are located. Hirshfeld surface analysis supports these findings, highlighting extensive contact areas between TBC6 molecules. This study contributes to understanding how solvent properties, interaction energies, and packing preferences drive the solid-state organization of calixarenes-molecules with broad applications in separation, recognition, and supramolecular chemistry.

Lake and Von Dreele [Acta Cryst. (2025), B81, 572-581] provide an informative look at the current state of the art in powder diffraction, and subtleties that can be revealed through its careful application.

The crystal structure of CuVP₂S₆ is investigated by transmission electron microscopy (TEM) and single-crystal X-ray diffraction. Cu, V and dimerized P₂ are each octahedrally coordinated by S atoms. Each metal ion species forms a triangular lattice, which is interdigitated to form a two-dimensional sheet. Each sheet forms a layered structure with van der Waals gaps between them. The crystal has a rotational twin structure, which is manifested in the form of stacking disorder. Refined structure analysis reveals characteristic rotational distortion of the octahedra. The existence of Cu sites protruding into the van der Waals gap is directly shown by high-resolution scanning TEM.

The virtual special issue on Magnetic Structures is introduced. The articles included here were originally published in recent regular issues of Acta Crystallographica Section B.

2,3-Dihydroxy-1,3,4-trimethyl-6-oxo-1,4-cyclohexadiene-1-carboxylic acid crystallizes in an order-disorder (OD) structure with a high stacking fault probability. The diffraction pattern features diffuse scattering and broad peaks, which can be attributed to fragments of two polytypes of a maximum degree of order (MDO). Additional weak peaks indicate existence of a non-MDO polytype. A detailed step-by-step instruction is given on how to develop an OD description and interpret the diffuse scattering using a stochastic growth model.