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Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

October 2014 issue

Highlighted illustration

Cover illustration: Neutron diffraction data have been collected at 12, 50, 150 and 295 K for the dipeptide glycyl-L-alanine in order to obtain accurate positional and anisotropic displacement parameters for the H atoms. The values of these parameters serve as a benchmark for assessing the equivalent parameters obtained from a so-called Hirshfeld-atom refinement of X-ray diffraction data. See Capelli, Bürgi, Mason & Jayatilaka [Acta Cryst. (2014), C70, 949-952].

research papers


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In 2-amino-1,3,4-thiadiazolium hydrogen oxalate, 2-amino-1,3,4-thiadiazole–glutaric acid (1/1) and 2-amino-1,3,4-thiadiazole–adipic acid (1/1), the graph-set motifs R_{2}^{2}(8), with N—H⋯O and O—H⋯N hydrogen bonds of moderate strength, are the most prominent features (N—H⋯O hydrogen bonds are present only in 2-amino-1,3,4-thiadiazolium hydrogen oxalate). The hydrogen-bond pattern of 2-amino-1,3,4-thiadiazole–succinic acid (1/2) differs considerably from the other title structures, though N—H⋯O and O—H⋯N hydrogen bonds of moderate strength are also present. There are nonbonding S⋯O interactions in all four structures, however, the packing patterns are quite different.

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A three-dimensional coordination polymer was synthesized by hydro­thermal reaction of Pb(OAc)2·3H2O (OAc is acetate), 2,2′-(diazene-1,2-di­yl)dibenzoic acid (H2L) and 1,2-bis­(pyridin-4-yl)ethyl­ene (bpe), displaying a 41263 topology network in which bpe mol­ecules act as noncoordinating guests. Inter­molecular hydrogen bonds and π–π stacking inter­actions further strengthen the three-dimensional framework.

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Triethyl 4,4′,4′′-[benzene-1,3,5-triyltris(ethyne-2,1-di­yl)]tribenzoate is a propeller-shaped mol­ecule of particular inter­est in the field of metal–organic frameworks (MOFs), where its hydrolyzed analogue forms MOF structures with high surface areas. Centrosymmetric dimers formed by π–π inter­actions are inter­connected by inter­molecular C—H⋯π inter­actions.

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The structures of two BICP complexes of rhodium(I) show a strong deviation in their backbones from the expected skew conformation. These compounds are applied as precatalysts in asymmetric homogeneous hydrogenation.

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The structures of the ternary compounds RE7Zn21+xSi2−x [RE = Ce, Pr, and Nd; 0.09 (1) < x < 0.95 (1)] are reported. Important structural features in these compounds are the large polyhedral cages made up of Zn atoms and the Si atoms in trigonal planar coordination. A small occupational Zn–Si disorder is found at the Si site.

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Neutron diffraction data have been collected at 12, 50, 150 and 295 K for the dipeptide glycyl-L-alanine in order to obtain accurate positional and anisotropic displacement parameters for the H atoms. The values of these parameters serve as a benchmark for assessing the equivalent parameters obtained from a so-called Hirshfeld-atom refinement of X-ray diffraction data.

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Three highly substituted cyclo­hexa­nols were prepared in satisfactory yield and with good stereospecificity by reaction of 4-halogenobenzaldehydes with 2-acetyl­pyridine under mild conditions. The mol­ecular structures of the cyclo­hexa­nols are very similar, but the crystal structures, particularly the space groups and the supra­molecular assemblies, are all different.

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In three differently solvated Cu2+ complexes of 1,3-bis­(penta­fluoro­phen­yl)propane-1,3-dionate, the p-xylene solvent mol­ecules are involved in arene–perfluoro­arene inter­actions with the penta­fluoro­phenyl groups. In a tetra­solvate, two of the p-xylene mol­ecules are located on the coordination CuO4 plane forming a uniform cavity produced by metal⋯π inter­actions.

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The structures and chemical properties of a new class of conjugated buta-1,3-dienes were studied by NMR, MS, X-ray analysis and quantum chemical calculations. The compounds can be used as dyes and pigments due to their long-range conjugated systems.

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Solvent-free single crystals of octa­phenyl-POSS were obtained by dehydration/condensation of the tetrol Si4O4(Ph)4(OH)4. The powder pattern matches well with the experimentally measured powder pattern of commercial octa­phenyl-POSS. The geometry of the crystal is compared with that in the gas phase, and has shorter Si—O bond lengths and a broader range of Si—O—Si bond angles.

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The structures of methyl para­thion and its 2-chloro derivative, dicapthon, are observed to have a few dissimilar features. These are notably around the C atoms to which the thio­phosphate and nitro groups are attached and those involving the phenolic O versus the –OMe groups.

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{[Co(pht)(bpy)(H2O)2]·2H2O}n (P2/n) single crystals (where pht is phthalate and bpy is 4,4′-bi­pyridine) dehydrate in a topotactic fashion into an anhydrate formulated as [Co(pht)(bpy)(H2O)2]n, which organizes in the ortho­rhom­bic system (Pmn21) in a disordered fashion, where two mirror-related 0.50:0.50 occupancy two-dimensional planar substructures are mirrored in a plane perpendicular to [100]. These two-dimensional substructures are also present in the parent hydrate, and have been found in topologically related structures with different anions and cations.

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In a pillared three-dimensional CdII coordination polymer incorporating isonicotinate, 5-aminotetrazolate, chloride and hydroxide ligands, Cd33-OH) units are laced around with a belt of chloride ligands. The belts are further connected into undulating layers via weak inter-belt Cd—Cl bonds.

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The crystal and mol­ecular structures of substituted carbazoles with π-electron-withdrawing –NO2 groups are reported, and the effects of these substituents on the aromaticity of the arene and pyrrole rings are assessed by means of HOMA indices. Density functional theory (DFT) calculations were performed to analyse the differences in the geometries of the studied compounds between the crystalline state and isolated mol­ecules.

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The one- and two-dimensional polymorphic cadmium polycarboxyl­ate coordination polymers catena-poly[bis[μ2-2-(2-methyl-1H-benzimidazol-1-yl)acetato]cadmium(II)] and poly[bis[μ2-2-(2-methyl-1H-benzimidazol-1-yl)acetato]cadmium(II)] were prepared under similar solvothermal conditions. Alternating layers of chains in the former are perpendicular to one another, while the latter contains (4,4)-connected nodes yielding square-grid layers.

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The crystal structures of three new phospho­ric tri­amides with a [C(O)NH]P(O)[N(C)(C)]2 skeleton are discussed. The C—N—C and P—N—C bond angles in these structures and analogous structures deposited in the Cambridge Structural Database are analysed.

Special and virtual issues

Acta Crystallographica Section C is planning special issues on

The Structural Chemistry of Homogeneous and Heterogeneous Catalysts

NMR Crystallography

Full details are available on the special issues page.

The latest virtual issue, featuring Coordination polymers and with an introduction by Len Barbour, was published in July 2014.

What are the 'most read' articles from the recent special issues?

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