issue contents

Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

August 2013 issue

Highlighted illustration

Cover illustration: A positive deformation density isosurface (0.009 e Å-3) for methyl (±)-(1S,2S,3R)-2-methyl-1,3-diphenylcyclo­propanecarboxylate, viewed in the plane of the ring. See Bacsa & Briones [Acta Cryst. (2013), C69, 910-914].

scientific comment


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A detailed analysis of the reporting of absolute structure has been undertaken on all the non-centrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012.

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Some reported structures fail to include all possible donor–acceptor close contacts, or to seek H-atom electron densities associated with apparent D—H⋯A trios. The relevant issues are illustrated with three published examples in the hope of slowing the proliferation of these problems, with the scientifically desirable goal of improving the accuracy of crystallographic models while also providing improved search keys for information retrieval.

metal-organic compounds


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The structure of the anion is a novel chloride-bridged penta­nuclear cluster. The five unique CdII centres have quite different coordination environments.

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The central Na+ cation exhibits distorted octa­hedral coordination geometry involving two deprotonated O atoms, two hy­droxy O atoms and two double-bonded O atoms of the bis­phosphon­ate anion. Pairs of sodium-centred octa­hedra share edges and the pairs are in turn connected to each other by the biphosphon­ate anion to form a two-dimensional network parallel to the (001) plane.

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Reaction of a newly synthesized 3-(3,5-dicarboxybenzyloxy)benzoic acid ligand with zinc ions yielded a single-framework metal–organic coordination polymer (MOF) of attractive architecture.

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The coordinating properties of the novel ligand 4′-[4-(pyrimidin-5-yl)phenyl]-2,2′:6′,2′′-terpyridine were tested by reacting it with cadmium(II) nitrate. The resulting title complex presents a supramolecular motif dominated by a significant number of π–π interactions involving all the aromatic rings.

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In the title coordination polymer, each AgI cation has a distorted tetra­hedral geometry coordinated by three of the four carboxyl­ate O atoms and the S atom from symmetry-related sulfane­di­yl­di­acetate ligands. The bridging sulfane­di­yl­di­acetate groups lead to a two-dimensional layer structure and the layers are interconnected via Ag—S bonds.

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The title structure con­tains two kinds of independent one-dimensional chain, viz. {[Cd(C8H15N2O2)Cl2]+}n and {[CdCl3(H2O)]}n, and uncoordinated water mol­ecules. Each CdII cation in the former chain is octa­hedrally coordinated by two pairs of bridging chloride ligands and two O atoms from different bridging carboxyl­ate groups, while CdII cations in the latter chain are octa­hedrally surrounded by four bridging chloride ligands, one terminal chloride ligand and one coordinated water mol­ecule.

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The structural unit consists of one C2-symmetric [NbOF4] anion, where the NbV centre is five-coordinated by four F atoms and one O atom in the first coordination shell, forming a square-pyramidal coordination geometry, and of one centrosymmetric coordinated [Cu2(obpy)2]+ cation (obpy is 2,2′-bipyridin-6-olate), in which the oxidation state of each Cu site is disordered, which is confirmed by XPS results.

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Transmetallation of a barium [2+2] Schiff base macrocycle with copper(II) results in three successive ring contractions, reducing the ring size from 20 to 16 members. Unusually, the contraction does not appear to result in an improved `fit' for the copper(II) ion.

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The Rb+ cation is surrounded by nine O atoms from Hpht anions and water mol­ecules, with a strongly deformed penta­gonal–bipyramidal geometry and one apex split into three positions. The crystal packing is governed by numerous hydrogen bonds involving all water mol­ecules and Hpht anions.

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This paper gives an account of a procedure to establish the identity of a ligand in an Ru complex and to refine two instances of positional and compositional disorder in the ligand and a counter-ion.

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The title complex is composed of two deprotonated N,N′-bidentate 2-[(phenyl­imino)­ethyl]-1H-pyrrol-1-ide ligands around a central NiII cation, with the pyrrolide rings and imine groups lying trans to each other. Mol­ecules are linked into simple chains by two C—H⋯π hydrogen bonds, one of which is inter­molecular with a phenyl β-C atom as donor, while the other is intra­molecular with a pyrrole β-C atom as donor.

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Two polymorphs contain octa­hedral [Co(en)3]3+ cations (en is ethyl­ene­diamine) and tetra­hedral [SbS4]3− anions, which are inter­connected via various N—H⋯S hydrogen bonds to form two different types of three-dimensional network.

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The crystal structure determination of this complex revealed the presence of two different anionic species which other spectroscopic methods failed to characterize. The reduced catalytic activity was not fully understood until the crystallographic data provided evidence for the mixed anionic species. The crystal structure of this RuII complex clearly shows that the majority of the synthesized material has a chloride anion present.

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The three title transition-metal complexes display a distorted 4+2 octahedral environment for the cation, with the macrocycle defining the base. The effect of the different axial ligands in the intra- and intermolecular hydrogen bonding is discussed.

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A structure evaluation is presented of a known structure from a merohedrally twinned crystal, together with a re-examination of the previously published models.

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In the title compound, the Pb atom sits on a crystallographic C2 axis and is six-coordinate, ligated by two chelating carboxyl­ate groups from two 3-(pyridin-4-yl)benzoate ligands and by two N atoms from another two benzoate ligands. Each ligand is conformationally chiral and bridges two PbII centres, extending the structure into a corrugated two-dimensional (4,4) net.

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The title AgI coordination polymer is a novel three-dimensional framework involving mixed naphthalene-1,5-disulfonate and aminoacetate ligands. In the crystal structure, each of the three different functional groups (carboxylate, amino and sulfonate) is coordinated to the AgI atoms.

organic compounds


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Mol­ecules of the title compound are linked into chains by inter­molecular C=O⋯H—N hydrogen bonds and the chains are weakly inter­connected by π–π stacking inter­actions. A comparison of the geometric parameters of the title mol­ecule and several related benzimid­azoles and pyrrolidones is presented.

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The molecules contain an intramolecular π–π stacking interaction, and C—H⋯O and C—H⋯N hydrogen bonds link the molecules to form a bilayer having tert-butyl groups on both faces.

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The title dipeptide, incorporating the nonproteinogenic amino acid residue L-2-aminobutyric acid, forms an extensively disordered, compact crystal packing arrangement in the tetragonal space group I4.

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In the title nucleoside, the N-glycosylic bond exhibits a syn conformation and the pento­furanosyl residue adopts a C2′-endo envelope conformation. The orientation of the exocyclic C4′—C5′ bond is +sc (gauche, gauche). The nucleoside forms an ordered and stacked three-dimensional network.

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A new polymorph of bis(2-aminopyridinium) fumarate–fumaric acid (1/1), determined using powder X-ray diffraction data, is described. The similarities and differences in hydrogen bonds between the new and previous polymorph are discussed in order to understand the polymorphism of the title salt.

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The conformation of a new TXA2 receptor antagonist, mainly determined by an intramolecular N—H⋯O hydrogen bond, is further explored using the Cambridge Structural Database.

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The crystal structures of three fumarate salts with different substituted anilines are reported. 3-Methyl­anilinium hydrogen fumarate and 4-chloro­anilinium hydrogen fumarate are isostructural resulting in the formation of similar supramolecular architectures.

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The electron density in the title substituted cyclo­propane has been determined by refining single-crystal X-ray data using scattering factors derived from quantum mechanical calculations. Topological analysis of the electron densities in the three cyclo­propane C—C bonds was carried out and shows the effects of substitution on these C—C bonds.

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Two very closely related pyrrolo[3,4-c]pyrrole derivatives form hydrogen-bonded sheets using a different combination of C—H⋯N, C—H⋯O and C—H⋯π interactions.

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The structures of (E)-2-(2-(phenylidene)hydrazinyl)quinoxaline and six Cl and Br derivatives have similar supramolecular structures involving an N—H⋯N hydrogen bond and π–π stacking interactions.

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Two polymorphs of N-(2-meth­oxy­phen­yl)-4-oxo-4H-chromone-3-car­box­amide crystallise in the monoclinic space group P21/c, each with two molecules in the asymmetric unit. The conformations of all four molecules are similar, the main differences being in their supramolecular interactions.

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The title compound exists in a zwitterionic form. There is a strong intra­molecular N—H⋯O hydrogen bond, an intra­molecular O—H⋯O hydrogen bond, an inter­molecular C—H⋯O contact and π–π stacking inter­actions, resulting in a three-dimensional network.

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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