Several fluoride compounds containing divalent tin that have a fluorite (CaF2-type) unit cell have been prepared and studied. Some are stoichiometric compounds while others are solid solutions. The cubic symmetry of the unit-cell (no lattice distortion and no superstructure) and the unique metal ion site of the fluorite structure make it that tin and the other metal have to be disordered on the normal metal site of the fluorite unit-cell. However, that site has the m3m-Oh point symmetry, and the metal ion is located in the center of a cube having fluoride ions in all its corners. Therefore, the same coordination should apply to tin. However, tin(II) possesses a non-bonding pair of electrons called a “lone pair”, and in order for tin(II) to have a cubic symmetry, its lone pair has to be located on the unhybridized 5s orbital, that is spherical and thus does not distort the coordination. In such a case, the lone pair is said to be “non-stereoactive”. This would make tin present in the form of the Sn2+ stannous ion, and therefore Sn−F bonding must be ionic. However, tin(II) fluorides are known to be always covalent with a hybridized lone pair on tin, which has therefore a reduced coordination number and therefore a highly distorted polyhedron of coordination. Such a hybridized lone pair is said to be “stereoactive”. Tin−119 Mössbauer spectroscopy was used to probe the bonding type and it showed that bonding is covalent, the lone pair is hybridized and the tin coordination is dramatically distorted. A model based on a double disorder was made that accounts for the apparent contradiction between the crystallographic and the Mössbauer results.

In the title molecular salt, (C₅H₇N₂)₂[SnCl₆], the cation is protonated at the pyridine N atom and the complete dianion is generated by a crystallographic centre of symmetry. In the crystal, N—H...Cl hydrogen bonds link the components into a three-dimensional network built up from the stacking of alternate cationic and anionic layers. The nature of the intermolecular interactions has been analysed in terms of the Hirshfeld surfaces of the cations and the anions. The thermal behaviour and the Raman spectrum of the title compound are reported.

In this study, we report the synthesis of two new copper complexes: [Cu(C₁₁H₇O₂)(SCN)(C₁₀H₈N₂)], denoted as (C-1), and [Cu(C₁₁H₇O₂) (C₁₂H₈N₂) Cl]·H₂O, denoted as (C-2). They are based on 2,2′-bipyridine or 1,10-phenanthroline and 2-hydroxy-1-naphtaldehyde ligands. The obtained complexes were characterized by FT-IR, UV-visible spectroscopy, and single-crystal X-ray diffraction analysis. Molecular docking was employed to predict the binding mode involved in the interaction between the two synthetic copper (II) complexes and HIV-1 protease enzyme. The X-ray structural analysis revealed that the crystal structures of both complexes are mainly stabilized by several intra- and intermolecular hydrogen bonds. The fingerprint plots associated with the Hirshfeld surfaces of both complexes clearly show that H···H interactions provide the largest contributions. According to the docking results, the synthesized complexes exhibit promising features which enable them to be bound to the HIV-protease enzyme.

The title benzimidazole compounds, namely, 2-(4-methoxynaphthalen-1-yl)-1H-benzo[d]imidazole, C₁₈H₁₄N₂O (I) and 2-(4-methoxynaphthalen-1-yl)-1-[(4-methoxynaphthalen-1-yl)methyl]-1H-benzo[d]imidazole ethanol monosolvate, C₃₀H₂₄N₂O₂·C₂H₆O (II), were synthesized by the condensation reaction of benzene-1,2-diamine with 4-methoxynaphthalene-1-carbaldehyde in the ratios 1:1 and 1:2, respectively. In I, the mean plane of the naphthalene ring system is inclined to that of the benzimidazole ring by 39.22 (8)°, while in II, the corresponding dihedral angle is 64.76 (6)°. This difference is probably influenced by the position of the second naphthalene ring system in II; it is inclined to the benzimidazole ring mean plane by 77.68 (6)°. The two naphthalene ring systems in II are inclined to one another by 75.58 (6)°. In the crystal of I, molecules are linked by N—H...N hydrogen bonds to form chains propagating along the a-axis direction. Inversion-related molecules are also linked by a C—H...π interaction linking the chains to form layers lying parallel to the ac plane. In the crystal of II, the disordered ethanol molecule is linked to the molecule of II by an O—H...N hydrogen bond. There are a number of C—H...π interactions present, both intra- and intermolecular. Molecules related by an inversion centre are linked by C—H...π interactions, forming a dimer. The dimers are linked by further C—H...π interactions, forming ribbons propagating along the b-axis direction. The interatomic contacts in the crystal structures of both compounds were explored using Hirshfeld surface analysis. The molecular structures of I and II were determined by density functional theory (DFT) calculations at the M062X/6-311+g(d) level of theory and compared with the experimentally determined molecular structures in the solid state. Local and global reactivity descriptors were computed to predict the reactivity of the title compounds. Both compounds were shown to exhibit significant anticorrosion properties with respect to iron and copper.