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Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

November 2017 issue

Highlighted illustration

Cover illustration: Structure factors representing disordered regions of a crystal structure can be modified to account for resonant scattering, improving the chances of successful absolute structure determination. See Cooper, Flack & Watkin [Acta Cryst. (2017), C73, 845-853].

feature articles


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Structure factors representing disordered regions of a crystal structure can be modified to account for resonant scattering, improving the chances of successful absolute structure determination.

research papers


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2,6-Di-tert-butyl-4-methyl­phenoxide (BHT) magnesium complexes exhibit a variety of crystal structure motifs. The X-ray structures of the bi-, tri- and tetranuclear BHT–Mg complexes have been established, viz. [(BHT)(DME)Mg(μ-OBn)2Mg(THF)(BHT)], {[(BHT)(THF)Mg]2Mg(μ-OC6H4-2-Me)4} and Mg4(BHT)2(OCH2CH2NH2)6 (DME is 1,2-di­meth­oxy­ethane and THF is tetrahydrofuran), respectively. The various types of polynuclear MgxOy cores for known ArO–Mg complexes are discussed.

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Two forms, i.e. triclinic and monoclinic, of 4-amino-5-chloro-2,6-di­methyl­pyrimidinium 5-chloro-2-hy­droxy­benzoate contain tautomeric forms of the cation, both of which exhibit quinonoid-type bond fixation, and the monoclinic form also exhibits both merohedral twinning and disorder. The ionic components in the triclinic form are linked by hydrogen bonds into finite four-ion aggregates, but those in the monoclinic form are linked into a three-dimensional framework structure.

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A three-dimensional cadmium(II) supra­molecular framework was prepared by the hydro­thermal reaction between Cd(NO3)2·4H2O, 1,4-bis­(pyridin-4-yl)buta-1,3-diene and adipic acid. This supra­molecular architecture is formed by the inter­linkage of a threefold inter­penetrating diamondoid coordination network through O—H⋯O hydrogen-bonding inter­actions.

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Each of three adducts of a series of di­bromo­perfluoro­alkyl compounds, BrCF2(CF2)nCF2Br (n = 2, 4, 6), and 1,4-di­aza­bicyclo­[2.2.2]octane (DABCO) displays a one-dimensional halogen-bonded network. All three adducts exhibit N⋯Br distances less than the sum of the van der Waals radii, with one adduct showing the shortest N⋯Br halogen-bond distances yet reported between a bromo­perfluoro­carbon and a nitro­gen base.

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The crystal structure of a hybrid imidazolyl­idene/imidazolium nickel N-heterocyclic carbene (NHC) complex is reported, which can be understood as a rare example of an isolated inter­mediate.

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In a new cadmium–dicyanamide (dca) complex, each CdII cation is coordinated by six nitrile N atoms from six anionic dca ligands to furnish a slightly distorted octa­hedral geometry. Neighbouring CdII cations are linked by dicyanamide bridges to construct a two-dimensional anionic layer coordination polymer.

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A novel cocrystal of 3,4,5-trifluoro­phenyl­boronic acid with urea has been synthesized and structurally characterized. The preference of formation of possible supra­molecular synthons has been verified by DFT calculations.

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A new arsenate, NaCa0.77Ni2.54Al0.46(AsO4)3, was synthesized using a flux method and it appears closely related to the α-CrPO4-structure type. The proposed structural model was validated by bond-valence-sum and charge-distribution analyses.

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The copper(II)- and gold(III)-mediated cyclizations of thio­urea derivatives to substituted 2-amino­benzo­thia­zoles are reported. The study provides mechanistic insight into the role of the metal cations in these transformations.

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The crystal structures of the novel γ-modification of anhydrous oxalates have been determined from powder diffraction data for MnC2O4 and CdC2O4 obtained during thermal decomposition of the corresponding hydrates. The distinctive features of this modification are loose packing and low densities compared with the known α- and β-modifications of anhydrous transition metal oxalates.

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In the isostructural tetra­hedral Fe and Co complexes of the multidentate PPN ligand 2-[bis­(diiso­propyl­phosphanyl)methyl]-6-methyl­pyridine, the ligand adopts a bidentate P,N-coordination, whereas in the case of the octa­hedral Mn complex, the ligand coordinates via both P atoms to the metal centre.

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Three rhenium(I) carbonyl-based photoCORMs have been synthesized and structurally characterized. All three complexes are highly luminescent and exhibit variable apparent CO release rates upon expousre to low-power UV light.

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The structures of the palladium and platinum complexes of 4,4′-bis­[(2,2-di­fluoro­eth­oxy)meth­yl]-2,2′-bi­pyridine are isomorphous and have –C(Hα)2OC(Hβ)2CF2H side chains with H-atom donors at the α and β sites. Mol­ecules are associated into dimers and the dimers form columns, with alternating dimers reinforced by C—H⋯Cl hydrogen bonds and C—Hβ⋯F(—C) inter­actions.

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In the structure of adipo­nitrile, a key inter­mediate in the synthesis of the polyamide Nylon 66, at 100 K, the mol­ecule adopts an exact Ci-symmetric gaucheantigauche conformation of the C—C—C—C skeleton about an inversion centre. The mol­ecules are densely packed, with short contacts between the α-H and nitrile N atoms.

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The energetic ionic salt bis­(1-amino­guanidin-2-ium) 5,5′-[1,2,4,5-tetra­zine-3,6-diylbis(aza­nedi­yl)]bis­(1H-1,2,3,4-tetra­zol-1-ide) dihydrate has a high nitro­gen content and exhibits good thermal stability. The crystal structure reveals a three-dimensional network of N—H⋯N, N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds.

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Cs3LiZn2(WO4)4 and Rb3Li2Ga(MoO4)4 represent two distinct series of filled derivatives of the cation-deficient Cs6Zn5(MoO4)8 structure with three-dimensional tetra­hedral frameworks related to that of mayenite 12CaO·7Al2O3. The series of tetra­gonal A3Li2R(MoO4)4 compounds exhibits second harmonic generation effects compatible with that of β′-Gd2(MoO4)3.

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Three new crystal structures of N-substituted cinnamamide derivatives, which were screened for anti­convulsant activity, are stabilized by inter­molecular O—H⋯O hydrogen bonds and additionally by N—H⋯O hydrogen bonds in two of the structures. The compounds possess fragments that are considered as beneficial for anti­convulsant activity. The conformations of these compounds were analyzed in comparison with the characteristic features of the proposed pharmacophore model of the anti­convulsants active in the maximal electroshock test.

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The influence of tautomeric forms and different coordination modes has been studied with respect to the formation of hydrogen-bonded networks in (4,4,4-tri­fluoro-1-phenyl­butane-1,3-dionato)copper(II) moieties in the presence of pyridin-2-one, 3-hy­droxy­pyridine and 3-hy­droxy­pyridin-2-one.

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A tetra­zolate- and cyanide-bridged CuII–CoIII bimetallic coordination polymer is the first example of a trinodal (6,8,8)-connected three-dimensional network and is constructed from anionic [Co(CN)6]3− and cationic [(Cu1)2(tta)2]2+ and [(Cu2Cu3)(tta)3]+ units. A magnetic investigation shows anti­ferromagnetic inter­actions between the paramagnetic CuII ions.

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In many cases, complexes of platinum and other metals have a symmetrical structure. In contrast, in the platinum(II) complex with pyridine and N-(9-anthracenylmeth­yl)-1,2-ethanedi­amine as ligands, the molecular structure is asymmetric. Only one of the two pyridine rings is π-stacked with the anthracene ligand enhancing the asymmetry.

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An extension of the study of the coordination capability of the (4-fluoro­phen­oxy)acetate ligand in the generation of metal complexes and, in particular, coordination polymeric supra­molecular structures with the alkali metal complex salts.

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The crystal structure of the hexgonal ternary borocarbide LiBC3 has been determined by the single-crystal method. LiBC3 represents the stucture family based on the graphene and heterographene networks.

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Sublimation yielded a new polymorph of 2,6-di­amino­pyridine, a common ingredient in and a synthetic precursor to many colorants.

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The structure of a three-component cocrystal of natural products contained extensive positional disorder in one of the mol­ecules. The identity of the disordered mol­ecule was established by 2D NMR and MS thereby making disorder modelling and structural refinement possible.

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Four 3,4-di­hydro-1-benzoxepin-5(2H)-one derivatives have been synthesized and the structure of 4-[3-(5-bromo-2-hy­droxy­phen­yl)allylidene]-3,4-di­hydro-1-benzoxepin-5(2H)-one was confirmed by single-crystal X-ray analysis. The inhibitory activities of these compounds against protein–tyrosine kinases (PTKs) were evaluated.

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The structures of a dimeric nickel(II) complex and a polymeric copper(II) complex supported by 1,2,4-triazole-3-carboxylate ligands, and a dimeric cobalt(III) complex supported by 3-amino-1,2,4-triazole-5-carboxylate ligands are reported.

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Two coordination polymers with distinct structures have been prepared under hydro­thermal conditions, based on mixtures of benzene-1,3,5-tri­carb­oxy­lic acid and trans-1-(pyridin-3-yl)-2-(pyridin-4-yl)ethene, together with two different d10 metal ions. Both compounds exhibit good photocatalytic properties in the decomposition of the organic dye contaminant of rhodamine B.

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Copper complexes ligated by benzyl­dipicolyl­amine (BDPA) are described. Inter­molecular O—H⋯O(tri­flate), O—H⋯O(tetrahydrofuran), C—H⋯F(tri­flate) and C—H⋯O(tri­flate) hydrogen bonds stabilize the crystal lattice of both structures.

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Three new platinum(II) complexes of the type [PtCl(R-OQ)(Eug)], containing eugenol (Eug) and a quinolin-8-ol derivative (R-OQ), show promising in vitro cytotoxicity on four human cancer cell lines.

Special and virtual issues

Acta Crystallographica Section C has recently published special issues on

NMR Crystallography (March 2017)

Scorpionates: a golden anniversary (November 2016)

Full details are available on the special issues page.

The latest virtual issue features Coordination polymers, with an introduction by Len Barbour.

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