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Acta Crystallographica. Section B, Structural Science

Vasyl Sidey
For the crystal structures of oxoborates, the value of ~1.2 Å can be regarded as the lower physical limit for B(III)-O bond lengths. The oxoborate crystal structures with B(III)-O bond lengths shorter than ~1.2 Å have been found to be either doubtful or clearly erroneous.
February 2013: Acta Crystallographica. Section B, Structural Science
Yury V Seryotkin, Tatiana N Drebushchak, Elena V Boldyreva
The crystal structure of the high-pressure polymorph (α') of an antidiabetic drug, chlorpropamide [4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, C(10)H(13)ClN(2)O(3)S], which is formed at ~2.8 GPa from the α-polymorph (P2(1)2(1)2(1)) on hydrostatic compression in saturated ethanol solution, has been determined. As a result of the phase transition, the a, c and α parameters change jumpwise, whereas the changes in b parameter are continuous through the phase transition point. The high-pressure form is monoclinic (P2(1)11) and has Z' equal to 2, the two independent molecules differing in their conformations...
February 2013: Acta Crystallographica. Section B, Structural Science
Christian Näther, Cindy Döring, Inke Jess, Peter G Jones, Christina Taouss
The title compound exists as polymorph (I), Fdd2 with Z = 8 [Pérez-Folch et al. (1997). J. Chem. Cryst. 27, 367-369; Marsh (2004). Acta Cryst. B60, 252-253], and as polymorph (II), P2(1)2(1)2 with Z = 2 [Martins et al. (2009). J. Phys. Chem. A, 113, 5998-6003]. We have redetermined both structures at somewhat lower temperatures [(I) at 180 K rather than room temperature; (II) at 100 K rather than 150 K]. For polymorph (I) the space group Fdd2 is confirmed rather than the original choice of Cc. The molecular structures of both polymorphs are essentially identical, with exact crystallographic twofold symmetry, approximate C(2v) symmetry, and a trans orientation of the H-N-C=O moiety...
February 2013: Acta Crystallographica. Section B, Structural Science
Pavle Mocilac, John F Gallagher
The one-step reaction of isophthaloyl dichloride with the 2-aminopyridine derivative (methyl 6-aminonicotinate) yields (i) a trimer-based macrocycle (EsIO)(3) and (ii) a tetramer-based macrocycle (EsIO)(4) in modest isolated synthetic yields (total of 25%), together with (iii) longer open-chain oligomers. The macrocyclization relies on the semi-flexible imide hinge formed by reaction of the 2-amino(pyridine) functional group with two acyl chloride functional groups. The determining factors in macrocycle synthesis are: (a) imide formation using the heteroaromatic ortho-N functionality; (b) the inherent ability of the imide to twist by 85-115° from planarity (as measured by the CO···CO imide torsion angles), thereby providing a hinge for macrocyclic ring closure or potentially (non)helical assembly in oligomer/polymer formation; (c) the conformational flexibility of the isophthaloyl group with meta-related carbonyl groups to twist and adopt either syn or anti conformations, although the syn conformation is observed structurally for all isophthaloyl groups in both (EsIO)(3) (trezimide) and (EsIO)(4) (tennimide) macrocycles...
February 2013: Acta Crystallographica. Section B, Structural Science
Khodayar Gholivand, Ali A Ebrahimi Valmoozi, Hamid R Mahzouni
The bisphosphoramidate (C(6)H(5)O)(2)P(O)NH(CH(2))(4)NHP(O)(OC(6)H(5))(2) crystallizes in two polymorphs, one (ndl) with a needle habit from tetrahydrofuran (THF)/ethanol and another (prm) which forms prisms from H(2)O/ethanol. The molecules in the two forms differ from each other in some torsion angles and the orientation of the diaminobutane bridge, although the differences between the similar bond lengths are not significant for the two polymorphs. The geometry optimizations at the B3LYP/6-31+G* level for isolated molecules show that the two conformers which exist in the crystalline state also represent local gas-phase energy minima...
February 2013: Acta Crystallographica. Section B, Structural Science
Florina Dumitru, Yves-Marie Legrand, Mihail Barboiu, Arie van der Lee
The synthesis and characterization of a series of halogen-substituted pseudoterpyridine Zn(II) homoleptic mononuclear complexes, based on ligands L(11)-L(44) [2,6-pyridinedicarboxaldehydebis(p-R-phenylimines), R = F, Cl, Br, I] are reported. Neither of the structures contain relatively strong classical hydrogen bonds (OH···O, NH···O, OH···N, NH···N) and the structure packing is thus determined by a subtle interplay of weaker interactions. Isostructurality of the four halogen analogues is very rare, and in this study -Br, -Cl and -F are found to be isostructural in different degrees, whereas -I is not...
February 2013: Acta Crystallographica. Section B, Structural Science
Tania N Hill, Andreas Roodt, Gideon Steyl
A range of single-crystal structures of the type [Pd(cod)(LL'-Bid)]A, where LL'-Bid = acetylacetonato (acac), thenoyltrifluoroactetonato (thtfac) and hexafluoroacetylacetonato (hfacac), and A = tetrafluoroborate (BF(4)(-)) and hexafluorophosphate (PF(6)(-)), are reported. The complexes [Pd(cod)(acac)]PF(6) (I), [Pd(cod)(thtfac)]PF(6) (III), [Pd(cod)(thtfac)]BF(4) (IV) and [Pd(cod)(hfacac)]PF(6) (V) are isostructural in the monoclinic space group P2(1)/c. The influence of the variation of the β-diketonato-type ligands on the coordination geometry of cis,cis-1,5-cycloocta-1,5-diene (cod) was investigated and found that no significant changes to the Pd-C and C=C bond distances were observed...
February 2013: Acta Crystallographica. Section B, Structural Science
M V Baidakova, N A Bert, V V Chaldyshev, V N Nevedomsky, M A Yagovkina, V V Preobrazhenskii, M A Putyato, B R Semyagin
The structure of low-temperature grown GaAs with equidistant δ-layers of Sb and P was studied by analysis of the X-ray curves, which was supported by optical absorption measurements and transmission electron microscopy. The simultaneous fitting of the X-ray reflectivity curve and diffraction ones for GaAs (004) and GaAs (115) crystallographic planes provided reliable information about the period of δ-layer superlattice, thickness of the Sb and P δ-layers, and amount of excess As. Variation of these parameters was documented when excess As precipitated into As nanoinclusions upon annealing...
February 2013: Acta Crystallographica. Section B, Structural Science
D J M Bevan, Lisandra L Martin, Raymond L Martin
The various superstructure phases that occur with the anion-deficient compositions of binary oxides MO(2-x) with the fluorite structure as parent are explored here in terms of the original 'coordination defect' (or CD) concept in which each vacant oxygen site, □, is 'coordinated' by six O atoms thereby creating the octahedral 'structure-determining' entity [M(3.5)□O(6)]. It emerges that the structure and composition of each anion-deficient (polymorph) phase can be described in terms of crystallographic `motifs' which comprise sets of parallel coplanar polygons based on ½<210>(F) and ½<111>(F) CD linkages...
February 2013: Acta Crystallographica. Section B, Structural Science
Lukáš Palatinus
The charge-flipping algorithm (CFA) is a member of the diverse family of dual-space iterative phasing algorithms. These algorithms use alternating modifications in direct and reciprocal space to find a solution to the phase problem. The current state-of-the-art CFA is reviewed and it is put in the context of related dual-space algorithms with relevance for crystallography. The CFA has found applications in many crystallographic problems. The principal applications in various fields are described with sections devoted to routine structure solution, the solution of complex structures from powder diffraction data, the solution of incommensurately modulated crystals and quasicrystals, macromolecular crystallography and single-particle imaging...
February 2013: Acta Crystallographica. Section B, Structural Science
Manolis Vasileiadis, Andrei V Kazantsev, Panagiotis G Karamertzanis, Claire S Adjiman, Constantinos C Pantelides
We investigate the ability of current ab initio crystal structure prediction techniques to identify the polymorphs of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, also known as ROY because of the red, orange and yellow colours of its polymorphs. We use a methodology combining the generation of a large number of structures based on a computationally inexpensive model using the CrystalPredictor global search algorithm, and the further minimization of the most promising of these structures using the CrystalOptimizer local minimization algorithm which employs an accurate, yet efficiently constructed, model based on isolated-molecule quantum-mechanical calculations...
December 2012: Acta Crystallographica. Section B, Structural Science
Berthold Stöger, Paul Kautny, Daniel Lumpi, Erich Zobetz, Johannes Fröhlich
During a systematic investigation of the crystallization behaviour of 9,9'-[1,3,4-thiadiazole-2,5-diylbis(2,3-thiophendiyl-4,1-phenylene)]bis[9H-carbazole] (I), six single crystalline solvates were obtained and characterized by X-ray diffraction at 100 K. The structure of the hemi-2-butanone (MEK) solvate contains two crystallographically independent molecules of (I) related by pseudo-inversion symmetry. The structure is polytypic and composed of non-polar (I) layers and polar solvent layers. It can be described according to an extended order-disorder (OD) theory with relaxed vicinity condition...
December 2012: Acta Crystallographica. Section B, Structural Science
Ivan Halasz, Robert Dinnebier, Tiziana Chiodo, Heidi Saxell
The crystal structures of four polymorphs of the pesticide dithianon (5,10-dihydro-5,10-dioxonaphtho[2,3-b]-1,4-dithiine-2,3-dicarbonitrile) have been solved from powder diffraction data and refined using the Rietveld method. Three polymorphs crystallize in non-centrosymmetric space groups. Two polymorphs have Z' > 1. The structures are assembled via interactions between carbonyl groups of quinoid fragments into layers which further interact only by weak interactions.
December 2012: Acta Crystallographica. Section B, Structural Science
Yvon Bibila Mayaya Bisseyou, Nouhza Bouhmaida, Benoit Guillot, Claude Lecomte, Noel Lugan, Noureddine Ghermani, Christian Jelsch
The electron-density distribution of a new crystal form of coumarin-102, a laser dye, has been investigated using the Hansen-Coppens multipolar atom model. The charge density was refined versus high-resolution X-ray diffraction data collected at 100 K and was also constructed by transferring the charge density from the Experimental Library of Multipolar Atom Model (ELMAM2). The topology of the refined charge density has been analysed within the Bader `Atoms In Molecules' theory framework. Deformation electron-density peak heights and topological features indicate that the chromen-2-one ring system has a delocalized π-electron cloud in resonance with the N (amino) atom...
December 2012: Acta Crystallographica. Section B, Structural Science
Mabel V Fulford, Alan John Lough, Timothy P Bender
The first instance of the solvent-free X-ray determined single-crystal structure of the oxygen-bridged boron subphthalocyanine dimer [μ-oxo-(BsubPc)(2), C(48)H(24)B(2)N(12)O] is reported. Single crystals obtained by train sublimation were found to have μ-oxo-(BsubPc)(2) organized into a C2/c space group. The crystal structure obtained by sublimation is of particular interest as it is highly symmetric and also of notably high density when compared with other BsubPc crystals. The acquisition of this crystal structure came about from the direct chemical synthesis of μ-oxo-(BsubPc)(2) followed by a work-up which culminated in obtaining the single crystals by sublimation...
December 2012: Acta Crystallographica. Section B, Structural Science
Adrian Mermer, Przemysław Starynowicz
Analysis of the experimental and theoretical charge-density distribution in potassium dihydrogen phosphoglycolate has been performed. The P-O bonds in the phosphate group are more polarized and the P atom is more positively charged than in phosphonate groups. The P-O bonds belong to a transit closed-shell (or polar covalent) class, while the ester C-O bond is a covalent (or shared-shell) bond. The coordination of potassium exerts a small effect on the phosphate group, whereas more pronounced changes, e.g. concerning the ellipticities of the C-O bonds, may be observed...
December 2012: Acta Crystallographica. Section B, Structural Science
Sumit Sanotra, Rimpy Gupta, Haq Nawaz Sheikh, Bansi Lal Kalsotra, Vivek K Gupta, Rajnikant
The synthesis and crystal structure of the compound bis(6-carboxypyridine-2-carboxylato-κ(3)O(2),N,O(6))nickel(II) trihydrate, Ni(Hpydc)(2)·3H(2)O, with a supramolecular network is reported (H(2)pydc is pyridine-2,6-dicarboxylic acid). The compound has been prepared by hydrothermal methods. The crystal structure has been solved by direct methods using single-crystal X-ray diffraction data collected at 293 K and refined by full-matrix least-squares procedures to a final R value of 0.0323 for 2779 observed reflections...
December 2012: Acta Crystallographica. Section B, Structural Science
Kevin Lamberts, Ulli Englert
Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions...
December 2012: Acta Crystallographica. Section B, Structural Science
Anatoly A Udovenko, Natalia M Laptash
Five isomorphous d(0) transition metal oxofluoride compounds A(3)[M(2)O(x)F(11-x)]·(AF)(0.333) (A = K, Rb, NH(4); M = Nb, Mo, W; x = 2, 4) have been synthesized from acid fluoride solutions, and their crystal structures have been determined by single-crystal X-ray diffraction. The basic structural building units are dinuclear M(2)X(11) (dimers) formed from NbOF(5) or Mo(W)O(2)F(4) octahedra connected by the fluorine bridging atom. In the Nb(2)O(2)F(9) dimer, the O atoms occupy apical corners. In the M(2)O(4)F(7) (M = Mo, W) dimers two O atoms are also apically placed, whereas the other two O atoms are statistically disordered in equatorial planes...
December 2012: Acta Crystallographica. Section B, Structural Science
E Iturbe-Zabalo, O Fabelo, M Gateshki, J M Igartua
The crystal and magnetic structures of SrLnFeRuO(6) (Ln = La, Pr, Nd) double perovskites have been investigated. All compounds crystallize with an orthorhombic Pbnm structure at room temperature. These materials show complete chemical disorder of Fe and Ru cations for all compounds. The distortion of the structure, relative to the ideal cubic perovskite, has been decomposed into distortion modes. It has been found that the primary modes of the distortion are octahedral tilting modes: R(4)(+) and M(3)(+). The crystal structure of SrPrFeRuO(6) has been studied from room temperature up to 1200 K by neutron powder diffraction...
December 2012: Acta Crystallographica. Section B, Structural Science
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