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Internal Symmetry (internal + symmetry)
Selected AbstractsN -(3- tert -Butyl-1-phenyl-1H -pyrazol-5-yl)- N -(4-methoxybenzyl)acetamide: a hydrogen-bonded chain of centrosymmetric ringsACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Juan C. Castillo The molecule of the title compound, C23H27N3O2, adopts a conformation having no internal symmetry so that the compound exhibits conformational chirality. The molecules are linked by a combination of C,H...O and C,H...,(arene) hydrogen bonds into a chain of rings in which two types of centrosymmetric ring alternate. [source] 5-Nitro- N4,N6 -diphenylpyrimidine-4,6-diamine: polarized molecules linked into ,-stacked chains via three-centre C,H...(O)2 hydrogen bondsACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2009Ricaurte Rodríguez Molecules of the title compound, C16H13N5O2, have no internal symmetry despite the symmetric pattern of substitution in the pyrimidine ring. The intramolecular distances indicate polarization of the electronic structure. There are two intramolecular N,H...O hydrogen bonds and molecules are linked into centrosymmetric dimers by pairs of three-centre C,H...(O)2 hydrogen bonds. These dimers are linked into chains by means of a ,,, stacking interaction. [source] Three lanthanide complexes derived from itaconic acid and 2,2,-bipyridineACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Juan Carlos Muñoz The structures of three new polymeric lanthanide complexes, poly[[bis(2,2,-bipyridine)-,4 -itaconato-di-,3 -itaconato-digadolinium(III)] tetrahydrate], {[Gd2(C5H4O4)3(C10H8N2)2]·4H2O}n, (I), poly[diaqua(2,2,-bipyridine)di-,3 -itaconato-,2 -itaconato-digadolinium(III)], [Gd2(C5H4O4)3(C10H8N2)(H2O)2]n, (II), and poly[[bis(2,2,-bipyridine)-,4 -itaconato-di-,3 -itaconato-diholmium(III)] dihydrate], {[Ho2(C5H4O4)3(C10H8N2)2]·2H2O}n, (III), have been solved from twinned specimens. Compound (I) presents a two-dimensional polymeric structure parallel to (011) built up around two independent nine-coordinated Gd centres displaying similar GdO7N2 environments, with both N-donor atoms in each provided by a chelating 2,2,-bipyridine (bpy) unit. The coordinating O atoms are from three different itaconate (ita) anions (itaconic acid is 2-methylidenebutanedioic acid). Compound (II) also presents two independent Gd centres (one ten- and the other eight-coordinated), but the overall formula and individual coordinations are different from those of (I). The chemical unit is in this case completed by one bpy ligand, three ita anions (one of them displaying a new, hitherto unreported, ,3 - O,O,:O,,O,,:O,,, binding mode) and two aqua ligands. The whole structure is built up around a twofold rotation axis passing through both cations, as well as through the centre of the bpy ligand and one of the ita anions, thus making only half of the chemical unit independent. Finally, compound (III) presents a single independent Ho centre, a bpy unit and one and a half ita anions (one of them bisected by a twofold rotation axis) in the asymmetric unit, plus two (disordered) nonbonded solvent water molecules. In compounds (II) and (III), those ita anions bisected by a symmetry element incompatible with the internal symmetry of the ligand exhibit disorder in the C=CH2 group. [source] 1,3-Bis(ethylamino)-2-nitrobenzene, 1,3-bis(n -octylamino)-2-nitrobenzene and 4-ethylamino-2-methyl-1H -benzimidazoleACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2008Christopher P. Walczak 1,3-Bis(ethylamino)-2-nitrobenzene, C10H15N3O2, (I), and 1,3-bis(n -octylamino)-2-nitrobenzene, C22H39N3O2, (II), are the first structurally characterized 1,3-bis(n -alkylamino)-2-nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2-C and 5-C atoms of the ring by twofold rotation axes. Both display intramolecular N,H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4,Å apart that interact by hydrophobic interactions involving the n -alkyl groups rather than by ,,, interactions between the rings. The intra- and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4-ethylamino-2-methyl-1H -benzimidazole, C10H13N3, (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N,H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4-amino and 2-alkyl substituents. [source] Structure of the sporulation histidine kinase inhibitor Sda from Bacillus subtilis and insights into its solution stateACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009David A. Jacques The crystal structure of the DNA-damage checkpoint inhibitor of sporulation, Sda, from Bacillus subtilis, has been solved by the MAD technique using selenomethionine-substituted protein. The structure closely resembles that previously solved by NMR, as well as the structure of a homologue from Geobacillus stearothermophilus solved in complex with the histidine kinase KinB. The structure contains three molecules in the asymmetric unit. The unusual trimeric arrangement, which lacks simple internal symmetry, appears to be preserved in solution based on an essentially ideal fit to previously acquired scattering data for Sda in solution. This interpretation contradicts previous findings that Sda was monomeric or dimeric in solution. This study demonstrates the difficulties that can be associated with the characterization of small proteins and the value of combining multiple biophysical techniques. It also emphasizes the importance of understanding the physical principles behind these techniques and therefore their limitations. [source] | ||||||||||