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Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

September 2014 issue

Highlighted illustration

Cover illustration: Water-rich aluminium halide hydrate structures are not known in the literature. The highest known water content per Al atom is nine for the perchlorate and fluoride. The nona­hydrate of aluminium bromide, stable penta­deca­hydrates of aluminium chloride, bromide and iodide, and a metastable hepta­deca­hydrate of the iodide have now been crystallized from low-temperature solutions. The cover image shows the second coordination spheres in AlI3·17H2O linked via edge sharing to form zigzag chains. This happens for both Al atoms in the same way. See Schmidt, Hennings & Voigt [Acta Cryst. (2014), C70, 882-888].

scientific comment


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A survey of approximately 100 000 entries in recent releases of the Cambridge Structural Database (CSD) from May 2010 to February 2013 has uncovered 156 crystal structures that were apparently described in inappropriate space groups.

research papers


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The title substituted pyrazolone compounds, one of them presenting two mol­ecules in the asymmetric unit, differ in the substituents on two terminal benzene rings. The three-dimensional supra­molecular structure is achieved in both cases via a number of C—H⋯O, C—H⋯π and π–π weak inter­actions, linking the mol­ecules into more or less compact supra­molecular structures.

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In a one-dimensional coordination polymer prepared from the direct reaction of 2-(hy­droxy­methyl)pyridine with Cu(OAc)2·H2O (OAc is acetate), four Cu centres are bridged by four O atoms from discrete (pyridin-2-yl)methanol­ate ligands and two acetate groups, forming a capped [Cu4O4] cubane core. Each core is doubly bridged to each of two adjacent cores by [N(CN)2] anions, resulting in one-dimensional chains.

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The lupane triterpenoid betulonic aldehyde (also known as betulonal) is a product of betulin oxidation. Crystals of two ortho­rhom­bic polymorphs were obtained from hexane and dimethyl sulfoxide solutions. The molecular geometric parameters in the two forms are similar, but the structures are different with respect to the crystal packing. The mol­ecular structures of both polymorphs are stabilized by weak inter­molecular C—H⋯O and van der Waals inter­actions.

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The structures of the two new pyroxene-type compounds, NaGaGe2O6 and NaInGe2O6, have been determined, and new data for NaMnGe2O6 and NaScGe2O6 are reported. The compounds adopt the high-temperature structure of the pyroxene-type chain germanates, with monoclinic symmetry and space group C2/c. The lattice parameters, the individual and average bond lengths involving M1, and the distortion parameters scale well with the ionic radius of the M1 cation.

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The heteroleptic cuprous complex [Cu(POP)(CH3CN)(4-PBO)]PF6, where POP is the diphosphane ligand {2-[2-(di­phenyl­phosphan­yl)phen­oxy]phen­yl}di­phenyl­phosphane and 4-PBO is the N-containing ligand 2-(pyridin-4-yl)-1,3-benzoxazole, displays a CuP2N2 distorted tetra­hedral coordination geometry. The electronic absorption, photoluminescence and thermal stability properties of this complex have been studied. A yellow emission band is attributed to an excited state resulting from metal–ligand charge transfer.

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The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM) by diffusion in silica gel at ambient temperature and the structural determination of this phase are reported. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetra­hydrated calcium pyrophosphate β phase (CPPT-β) is discussed.

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The reaction of (2RS,3SR)-2,3-di­bromo-1,3-bis­(4-fluoro­phenyl)propan-1-one with phenylhydrazine gave a pyrazole exhibiting some aromatic-type delocalization in the pyrazole ring and with mol­ecules that are linked into simple chains by a single C—H⋯π(arene) hydrogen bond. The same reaction with 4-hy­droxy­benzo­hydrazide instead of phenylhydrazine gave a solvated oxa­diazine, with the oxa­diazine mol­ecules linked by a combination of N—H⋯N and C—H⋯O hydrogen bonds to form complex sheets and with the solvent mol­ecules attached at the outer faces by O—H⋯O hydrogen bonds.

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The crystal structures of 1,2-dimethyl-3-nitro­benzene and 2,4-dimethyl-1-nitro­benzene, which are liquids at room temperature, have been obtained through in-situ cryocrystallization. Weak C—H⋯O and π–π inter­actions have been identified in both compounds.

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In each of the crystal structures of four different calcium halide hydrates, calcium is coordinated by eight water mol­ecules. In the case of calcium bromide enneahydrate, the highest stage of hydration of a calcium salt was observed. For calcium iodide hepta- and octa­hydrate, two new structures are discussed. These structures are built up of dimers with a connection type unknown for other calcium salt hydrates. A peculiar feature of the higher hydrates of bromide and iodide salts is the dimerization of aqua complexes.

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From low-temperature solutions of aluminium halides, the water-rich hydrates AlCl3·15H2O, AlBr3·15H2O, AlI3·15H2O, AlI3·17H2O and AlBr3·9H2O were crystallized and their crystal structures determined. The structures are discussed in terms of primary and secondary hydration of Al3+ and are of interets with respect to the chemistry of Mars.

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In four halogenated N,2-diaryl­acetamides, two are isostructural in the space group P\overline{1}, with mol­ecules linked into chains of rings by a combination of N—H⋯O and C—H⋯π(arene) hydrogen bonds. Mol­ecules of the other two acetamides are linked into simple C(4) chains by N—H⋯O hydrogen bonds, but significant C—H⋯π(arene) inter­actions are absent.

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The crystal structures of three 5-alkenyl-2-aryl­thieno[3,2-b]thio­phenes have been determined in order to evaluate the planarity and geometry of the mol­ecules. The crystal packings are characterized by π–π stacking and C—Br⋯π inter­actions.

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Eight crystal structures of protonated forms of the sulfa drug sulfadiazine are presented. Sulfonate-containing anions support a different tautomeric form of the sulfadiazine cation than that supported by other anions.

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In a substituted pyrazolo­[1,5-a][1,3,5]triazine, centrosymmetric dimers generated by C—H⋯O hydrogen bonds are linked into chains by a π–π stacking inter­action.

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The structures of eight benzoyl­hydrazones show similar conformations and hydrogen-bonding patterns. In most cases, the phenyl ring of the benzoyl group is rotated by about 30° with respect to the keto group. Only one of the amide groups exhibits the syn conformation.

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Four imidazo[2,1-b][1,3,4]thia­diazo­les display similar mol­ecular constitutions and exhibit a wide variety of supra­molecular structures. The mol­ecular skeletons are all nearly planar. Two of the structures exhibit C—H⋯N hydrogen bonding, forming ribbons in one and dimers in the other, while hydrogen bonding is absent in the remaining two structures.

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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