Structure of 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyl 1,10-ditosylate by X-ray crystallography and F-19-NMR spectroscopy

2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorodecyl 1,10-ditosylate and its precursors were synthesized and characterized by H-1- and F-19-NMR spectroscopic methods and X-ray crystallography. These compounds are building blocks for the syntheses of the surfactants containing polyperfluoromethylene spacer. The molecule has extended all-trans conformation with molecular symmetry (1) over bar (C-i). There is a reasonably strong C-H ... O interaction in the crystal and there are two F ... F intermolecular contact distances less than the sum of van der Waals radii. (C) 1999 Elsevier Science B.V. All rights reserved

Structural elucidation, theoretical insights and thermal properties of three novel multicomponent molecular forms of gallic acid with hydroxypyridines

Development of novel drug for manipulating the physicochemical properties of the API by obtaining their multicomponent forms is a challenging task in the pharmaceutical industry. Novel multicomponent crystal forms of gallic acid with three hydroxypyridines have been prepared by liquid assisted grinding and slow evaporation of the solvent. Preliminary PXRD and FTIR characterizations were carried out to confirm the interactions between the components, then the three dimensional molecular structures were confirmed through single crystal X-ray diffraction method. Structural studies clearly revealed the three distinct molecular crystal forms of gallic acid with hydroxypyridines. The molecular structures exhibit O�H�O, N�H�O and C�H�O intermolecular hydrogen bond interactions, which results different supramolecular motifs. Further, intermolecular interactions were quantified through Hirshfeld surface analysis, which revealed the dominance of O�H and H�H interactions. Computation of interaction energies between the molecules and analysis of three dimensional energy frameworks quantifies the molecular packing. The density functional theory calculations were employed to optimize the structural coordinates, which substantiate the experimental results. Low value of HOMO-LUMO energy gap signifies the promising electronic properties of the molecules. The chemical reactive sites were further identified on the molecular electrostatic potential surface. Finally, thermal properties of the crystals were studied using thermogravimetric analysis

Syntheses, structure, reactivity and species recognition studies of oxo-vanadium(V) and -molybdenum(VI) complexes

Alkoxo-rich Schiff-bases of potentially tri-, tetra- and penta-dentate binding capacity, and their sodium tetrahydroborate-reduced derivatives, have been synthesized. Their oxo-vanadium(V) and -molybdenum(VI) complexes were synthesized and characterized using several analytical and spectral techniques including multinuclear NMR spectroscopy and single-crystal X-ray diffraction studies. Eight structurally different types of complexes possessing distorted square-pyramidal, trigonal-bipyramidal and octahedral geometries have been obtained. While (VO)-O-V exhibits dimeric Structures with 2-HOC6H4CH=NC(CH2OH)(3) and 2-HOC6H4CH2-NHC(CH2OH)(3) and related ligands through the formation of a symmetric V2O2 core as a result of bridging of one of the CH2O- groups, Mo O-VI gives only mononuclear complexes even when some unbound CH2OH groups are available and the metal center is co-ordinatively unsaturated. In all the complexes the nitrogen atom from a HC=N or H2CNH group of the ligand occupies a near trans position to the M=O bond. While the Schiff-base ligands act in a tri- and tetra-dentate manner in the vanadium(V) complexes, they are only tridentate in the molybdenum(VI) complexes. Proton NMR spectra in the region of bound CH, provides a signature that helps to differentiate dinuclear from mononuclear complexes. Carbon-13 NMR co-ordination induced shifts of the bound CH, group fit well with the charge on the oxometal species and the terminal or bridging nature of the ligand. The reactivity of the vanadium(V) complexes towards bromination of the dye xylene cyanole was studied. Transmetallation reactions of several preformed metal complexes of 2-HOC6H4CH=NC(CH2OH)(3) with VO3+ were demonstrated as was selective extraction of VO3+ from a mixture of [VO(acac)(2)] and [MoO2(acac)(2)] using this Schiff base. The unusual selectivity and that of related derivatives for VO3+ is supported by binding constants and the solubility of the final products, and was established through a.c. conductivity measurements. The cis-MoO22+ complexes with alkoxo binding showed an average Mo-O-alk distance of 1.926 Angstrom, a value that is close to that observed in the molybdenum(VI) enzyme dmso reductase (1.92 Angstrom). Several correlations have been drawn based on the data

Crystal and solution structure of the C-terminal part of the Methanocaldococcus jannaschii A1AO ATP synthase subunit E revealed by X-ray diffraction and small-angle X-ray scattering.

The structure of the C-terminus of subunit E (E(101-206)) of Methanocaldococcus jannaschii A-ATP synthase was determined at 4.1 A. E(101-206) consist of a N-terminal globular domain with three alpha-helices and four antiparallel beta-strands and an alpha-helix at the very C-terminus. Comparison of M. jannaschii E(101-206) with the C-terminus E(81-198) subunit E from Pyrococcus horikoshii OT3 revealed that the kink in the C-terminal alpha-helix of E(81-198), involved in dimer formation, is absent in M. jannaschii E(101-206). Whereas a major dimeric surface interface is present between the P. horikoshii E(81-198) molecules in the asymmetric unit, no such interaction could be found in the M. jannaschii E(101-206) molecules. To verify the oligomeric behaviour, the low resolution structure of the recombinant E(85-206) from M. jannaschii was determined using small angle X-ray scattering. Rigid body modeling of two copies of one of the monomer established a fit with a tail to tail arrangement