Zero-dimensional (0D) perovskites are promising materials due to their structures comprising isolated metal halide octahedra or clusters, which impart remarkable optoelectronic properties. The synthesis, crystal structure and Hirshfeld surface analysis of the title compound, 1,4-diazoniabicyclo[2.2.2]octane hexabromidostannate(IV) hemihydrate, (C6H14N2)[SnBr6]·0.5H2O or (DABCO)[SnBr6]·0.5H2O, are reported. The compound crystallizes in the monoclinic space group P21/n. Dominant H...Br/Br...H interactions (90.5%) are observed, with smaller contributions from H...H (5.1%), Br...Br (4.2%) and O...Br/Br...O (0.1%) contacts. These structural features underline the role of hydrogen bonding in stabilizing the 0D framework, highlighting its potential for light-emitting and photonic applications.

Treating the thioamide 1-(2,6-dimethylphenyl)thiourea (C9H12N2S, DMPT) with concentrated aqueous strong acids gave three salt forms with protonation at the thioamide S atom. The structures of 1-(2,6-dimethylphenyl)thiouronium chloride, C9H13N2S+·Cl- or [DMPT(H)][Cl], 1-(2,6-dimethylphenyl)thiouronium bromide, C9H13N2S+·Br- or [DMPT(H)][Br], and 1-(2,6-dimethylphenyl)thiouronium hydrogen sulfate, C9H13N2S+·HSO4- or [DMPT(H)][HSO4], are compared with that of neutral DMPT. Protonation at the S atom results in a systematic lengthening of the C=S bond and a shortening of the C-N bonds, with a larger effect found for the bonds involving the secondary amine rather than the primary amine function. The [DMPT(H)]+ cations are found to adopt one of two possible conformations, with the halide species having secondary N-H syn to S-H, whilst in the hydrogen sulfate structure, this relationship is anti. The change in cation conformation is related to a change in the hydrogen-bonding motif, but all three salt forms form layered structures with two-dimensional hydrogen-bonded units separated by layers of hydrophobic arene rings. An alternative product type was isolated on adding DMPT to concentrated sulfuric or tetrafluoroboric acid. Structures of the dicarbocationic disulfide species (disulfane-1,2-diyl)bis[N-(2,6-dimethylphenyl)methanediaminium] bis(tetrafluoroborate), C18H24N4S22+·2BF4- or [Dimer][BF4]2, and (disulfane-1,2-diyl)bis[N-(2,6-dimethylphenyl)methanediaminium] bis(hydrogen sulfate) monohydrate, C18H24N4S22+·2HSO4-·H2O or [Dimer][HSO4]2·H2O, are also described.

A new combination of molecules that form a solid solution is reported. The 2,4,6-tris(4-tert-butylphenyl)phenoxyl radical, C36H41O (1M), formed two solid solutions (α and β) with its methoxy analogue 1,3,5-tris(4-tert-butylphenyl)-2-methoxybenzene, C37H44O (1OMe). According to single-crystal X-ray analysis, the crystal structure of each solid solution is thought to be dominated by the characters of the main components. The β crystal (1M:1OMe = 0.002:0.998) is isomorphic to the crystal composed solely of 1OMe and the molecules in the β crystal adopt the most preferred conformation for 1OMe. In contrast, in the α crystal (1M:1OMe = 0.80:0.20), the molecules adopt the most preferred conformation for 1M. However, since a crystal composed solely of 1M has not been obtained (1M always precipitates as a σ-dimer formed by a covalent C-O bond between the phenoxyl O atom of one molecule and the para-C atom of the central phenyl ring of another molecule), it is unclear whether it is isomorphic with the α crystal.

Recrystallization of pazufloxacinium mesylate from HCl solutions yielded two previously unknown salts of pazufloxacin. These were characterized by X-ray diffraction and are bis(oxidanium) pentakis[(2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.05,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid] heptachloride decahydrate, 2H3O+·5C16H16FN2O4+·7Cl-·10H2O (1), and (2S)-6-(1-azaniumylcyclopropyl)-7-fluoro-2-methyl-10-oxo-4-oxa-1-azatricyclo[7.3.1.05,13]trideca-5(13),6,8,11-tetraene-11-carboxylic acid chloride ethanol hemisolvate 1.75-hydrate, C16H16FN2O4+·Cl-·0.5C2H6O·1.75H2O (2), which were obtained from acetonitrile and ethanol, respectively. The compounds crystallize in the noncentrosymmetric triclinic space group P1. Salt 1 contains five independent cations and seven chloride anions, while compound 2 contains eight independent cations and anions. In both, an intramolecular COOH...O=C hydrogen bond is present and the amino group is protonated. The cations, anions and solvent molecules form extensive hydrogen-bonded frameworks. In addition, in both structures, the cations are packed into infinite stacks via π-π interactions, with interplanar distances of approximately 3.2 Å.

The ternary boride MgNi2B6 (magnesium dinickel hexaboride) crystallizes as a new representative of the CeCr2B6 structure type. The Mg and Ni atoms occupy sites with mmm and mm2 symmetry, respectively. The B atoms occupy two sites with m.. and m2m symmetry. The 14-membered polyhedron around the Mg atom is a hexagonal prism, with two adjacent lateral faces centred by Mg atoms. The Ni atoms are encapsulated in 10-vertex polyhedra. The trigonal prismatic coordination is typical for both B atoms. The electronic structure was calculated by the tight-binding linear muffin-tin orbital atomic spheres approximation (TB-LMTO-ASA) method. The electron concentration is higher around the B atoms, which form eight-membered channels along b, which are filled with Mg and Ni atoms. The maximum hydrogen absorption is up to 2.38 wt% H2.

Bis[bis(ethylenedithio)tetraselenafulvalene(0.5+)] dibromidoaurate(I) and its chloride analogue, (C10H8S4Se4)2[AuX2] or BETS2AuX2 (X= Cl and Br), were synthesized to examine their crystal and band structures. The crystal structures are new in that they have both structural features of different types of organic Dirac electron systems (ODES), i.e. α- and α'-type iodine-centred trihalide (IX2-) salts of BETS-related electron-donor molecules. The former often produces zero-gap semiconductors, while the latter is related to nodal-line semimetals, i.e. classes of ODES different from each other. The band structure calculation suggests that BETS2AuX2 are close to zero-gap semiconductors, indicating that the α-type structural feature governs the band structures in these salts. Although the dimensions and geometries of the constituents are close to each other between BETS2IX2 and BETS2AuX2, the strength of the BETS-anion interaction resulted in a difference in the crystal structures between the α- and α'-type molecular arrangements. Our findings show that the crystal and band structures are affected by the electronic states of the constituents sometimes more than one would expect based on their geometrical features.

Two 1:1 cocrystals of imidazo[1,2-a]pyridine-3-carbonitrile (IPC) with 4-nitrobenzoic acid (4-NBA) and 4-nitrophenol (4-NP), namely, imidazo[1,2-a]pyridine-3-carbonitrile-4-nitrobenzoic acid (1/1), C8H5N3·C7H5NO4 or (IPC)·(4-NBA) (I), and imidazo[1,2-a]pyridine-3-carbonitrile-4-nitrophenol (1/1), C8H5N3·C6H5NO3 or (IPC)·(4-NP) (II), were obtained and their crystal structures determined by single-crystal X-ray diffraction. Molecules of I and II are both linked by O-H...N, C-H...O and C-H...N hydrogen bonds to form two-dimensional planes, which are further connected into three-dimensional frameworks by C-H...π interactions (in I) and π-π interactions (in II).

Stimuli-responsive crystalline materials have demonstrated significant potential for developing multifunctional systems. Achieving precise structural modulation in non-porous crystalline phases remains a critical challenge, particularly in correlating molecular-level conformational changes with macroscopic properties. Here, we report a solvatomorphic crystalline system, (1-azabicyclo[2.2.2]octane-κN){4,4',6,6'-tetra-tert-butyl-2,2'-[1,2-phenylenebis(nitrilomethylidyne)]diphenolato-κ4O,N,N',O'}zinc(II) acetonitrile monosolvate, [Zn(C36H46N2O2)(C7H13N)]·CH3CN or [Zn(saloph)](quinuclidine)](acetonitrile) (1·solvent), which exhibits a reversible single-crystal-to-single-crystal transformation during acetonitrile adsorption/desorption. Structure analysis reveals that solvation dynamics induce a pronounced variation in the dihedral angle of the [Zn(saloph)] coordination centre, accompanied by a luminescence red shift of approximately 10 nm. This work establishes a strategy for modulating optoelectronic properties in non-porous crystalline materials through solvent-mediated structural reorganization, advancing the development of stimuli-responsive functional materials.

An overview of the development of electron diffraction and an introduction to the special issue Advances in Electron Diffraction for Structural Determination.

3D electron crystallography has emerged as a method with great potential for the structure determination of small molecules and macromolecules complementing traditional single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). It offers the unique capability of determining the structures of small molecules and macromolecules from micro- and nanocrystals. In this study, using 3D electron diffraction (3DED), we determined the single-crystal structure of commercially sourced arginine directly from its bottle. The 3DED analysis of micro-sized single crystals identified two distinct forms: the L-arginine enantiomer and the racemic mixture DL-arginine. At the time of writing, neither the Cambridge Structural Database nor the Crystallographic Open Database contain a single-crystal structure of isolated L-arginine (sum formula C6H14N4O2), which has been solved in this work by 3DED. We also present a comparison of the structures of these molecules solved by 3DED and PXRD.