Volume 231, Issue 6

The gallides Ca 3 Ni 4 Ga 4 and Sr 3 Ni 3 Ga 4 were synthesized from arc-melted Ni x Ga y precursor alloys and the respective alkaline earth metal in sealed niobium tubes in an induction furnace. Redetermination of the Ca 3 Ni 4 Ga 4 structure from X-ray single crystal diffractometer data confirmed the X-ray powder data: Na 3 Pt 4 Ge 4 type, I 4̅3 m , a =740.6(1) pm, wR 2=0.0245, 169 F 2 values, 9 variables. The nickel atoms build tetrahedral Ni 4 clusters (256 pm Ni–Ni) that are end-on coordinated by gallium atoms (234 pm Ni–Ga). These [Ni 4 Ga 4 ] units show a bcc packing and leave cavities Ca@Ga 4 Ni 4 Ga 4 for the calcium atoms. Sr 3 Ni 3 Ga 4 crystallizes with a new structure type: R 3 m , a =1039.8(2), c =698.2(1) pm, wR 2=0.1048, 636 F 2 values, 23 variables. The structure shows twinning by inversion with a domain ratio of 79/21. The structures of Sr 3 Ni 3 Ga 4 and Ca 3 Ni 4 Ga 4 are related by a group–subgroup scheme ( R 3 m is a translationengleiche subgroup of I 4̅3 m ). The 8 c Ni and Ga subcell sites split into site 3 a and 9 b each. This allows formation of ordered Ni 3 Ga tetrahedra (264 pm Ni–Ga) along with ordered gallium vacancies.

Some biologically active organotellurium compounds exhibit inhibitory potency against cathepsin B. In this study, an alkyl derivative, viz. [CH 3 (CH 2 ) 2 C(I)=C(H)](nBu)TeI 2 , 1 , has been structurally characterised by X-ray crystallography and shown to be coordinated within a C 2 I 2 donor set. When the stereochemically active lone pair of electrons is taken into account, a distorted trigonal bipyramidal geometry results with the iodide atoms in axial positions. Both intra- and inter-molecular Te···I interactions are also noted. If all interactions are considered, the coordination geometry is based on a Ψ-pentagonal bipyramidal geometry. An unusual feature of the structure is the curving of the functionalised C 5 chain. This feature has been explored by DFT methods and shown to arise as a result of close C–H···I interactions. A docking study (cathepsin B) was performed to understand the inhibition mechanism and to compare the new results with previous observations. Notably, 1 has the same pose exhibited by analogous biologically active compounds with aryl groups. Thus, the present study suggests that (alkyl) 2 TeX 2 compounds should also be evaluated for biological activity.

The crystal structure analysis of three aryl-1,3-dithiane derivatives, with aryl=4-methylphenyl ( 1 ), 4-chlorophenyl ( 2 ) and 2,4-dichlorophenyl ( 3 ), shows the three molecules to have very similar conformations, with the aryl ring lying on an approximate mirror plane that bisects the dithiane ring which adopts a chair conformation; the energy-minimised structures are consistent with the experimental structures. The greater barrier to rotation about the methine-C–C(ipso) bond in 3 , cf. 1 and 2 , is related to unfavourable intramolecular S···Cl interactions in the putative transition state. The molecular packing in 1 – 3 , while globally similar, are distinct, being based on combinations of identifiable C–H···π(arene), C–H···S and C–Cl···π(arene) interactions. The lack of isostructural relationships points to the significance of the identified intermolecular interactions to direct molecular packing.

The crystal and molecular structures of (Ph 3 P) 2 M[S 2 CN(Me)CH 2 CH 2 OH], M=Cu, isolated as a 1:1 dichloromethane solvate ( 1 ·CH 2 Cl 2 ), and M=Ag ( 4 ) show the central metal atom to be coordinated by a symmetrically ( 1 ·CH 2 Cl 2 ) and asymmetrically chelating ( 4 ) dithiocarbamate ligand. The distorted tetrahedral geometries are completed by two PPh 3 ligands. The presence of hydroxyl-O–H···S(dithiocarbamate) hydrogen bonds leads to centrosymmetric dimeric aggregates in each crystal structure. In the molecular packing of 1 ·CH 2 Cl 2 , channels comprising 1 are formed via aryl-C–H···O interactions with the solvent molecules associated with the walls of the channels via methylene-C–H···S, π(aryl) interactions. For 4 , the dimeric aggregates are connected via a network of aryl-C–H···π(aryl) interactions. Preliminary screening for anti-microbial activity was conducted. The compounds were only potent against Gram-positive bacteria. Some further selectivity in activity was noted. Most notably, all compounds were active against methicillin resistant Staphylococcus aureus .

A specimen of high-carbon nitrogen-doped steel has been synthesized to supplement previous studies on wootz-like steels. A comparison of different states of material as well as one of distinct methods of hardness testing has been performed. Electron microscopy of the specimens’ microstructure revealed nano-structuring similar to that observed with ancient sabers. Part of them was annealed so that the nano-structures dissolved. Nano-hardness values derived under ambient conditions from indentation as well as from scratch tests were determined and related to the microstructure prior to and after annealing. The disappearance of nanostructuring led to a significant drop of hardness. The ratio of indentation to scratch hardness proved a suitable indicator of hardening. From hardness as function of penetration depth and from friction as function of time and normal load various quantitative features of the mechanical properties and of the deformation process have been evaluated. When modeling friction, sliding and plowing parts have been distinguished quantitatively. Enhanced adhesion forces were attributed to surface layers.

The crystal structure analysis of a 2,6-diaryl 4-piperidone derivative, isolated as a mono-methanol solvate, reveals that both the piperidone and the methanol molecule lie on a crystallographic mirror plane. A chair conformation is found for the piperidone ring with the aryl and methyl groups in equatorial positions. The most prominent feature of the molecular packing is the formation of supramolecular zigzag chains mediated by amine-N–H···O(methanol) and hydroxyl-O–H···N(amine) hydrogen bonds, i.e. the methanol molecule serves as a bridge between piperidone molecules. The molecular structure is compared with that determined in an unsolvated form and the gas-phase equilibrium structure, obtained using density-functional theory (DFT); differences relate, in the main, to the relative dispositions of the aryl rings. An analysis of the Hirshfeld surfaces of the experimental structures indicates very similar relative contributions with the notable exception being the contribution by O···H/H···O which at 13.7% in the methanol solvate is >8.5% in the unsolvated form.

The investigation of the crystal structures of three closely related sulfonamides, namely N-(2-fluorobenzoyl)-2-methylbenzenesulfonamide (I), N-(2-fluorobenzoyl)-4-methylbenzenesulfonamide (II) and N-(2-fluorobenzoyl)-2-chlorobenzenesulfonamide (III) by analysing intermolecular interactions and the packing patterns, and also by Hirshfeld surface analyses is presented. Compound (I) has a three-dimensional (3D) network, in which N–H···O and C–H···F chains build up two-dimensional (2D) arrays, which are extended into a 3D network through C–H···π interactions. In (II), alternating N–H···O and C–H···O rings form one-dimensional (1D) ribbons, which are interconnected by C–H···π interactions to build a 2D network. In (III), 2D sheets comprising N–H···O rings, C–H···π chains, Cl···F and F···F contacts are stacked by π···π interactions to form a 3D network. Hirshfeld surface analyses, comprising d norm surfaces, curvedness and 2D fingerprint (FP) plots, for all three molecules were also conducted to verify the importance of the different intermolecular interactions.