Packing Structure (packing + structure)

Distribution by Scientific Domains
Distribution within Chemistry


Selected Abstracts


Syntheses, structures, and supramolecular properties of giant ,-expanded macrocyclic oligothiophenes

HETEROATOM CHEMISTRY, Issue 5 2007
Masahiko Iyoda
Fully conjugated ,-expanded macrocyclic oligothiophenes with 60,-, 90,-, 120,-, 150,-, and 180,-electron systems (1,5) were synthesized using modified McMurry coupling reaction as a key step. Compound 1 was converted into macrocyclic oligo(2,5-thienylene-ethynylene) 6 using bromination-dehydrobromination procedure. X-ray analysis of 1 revealed a unique molecular and packing structure, reflecting a round, planar shape with nanoscale inner cavity. Interestingly, 2 and 3 self-aggregate in the solid state to form nanowires. The structure of fibrous aggregates was established by scanning electron microscopic and atomic force microscopic analyses. Compounds 1,6 exhibit multi-step reversible redox behavior with fairly low first oxidation potentials, reflecting their cyclic conjugation. Doping of 1,3 with iodine gives semiconductors owing to their ,-donor properties and ,,, stacking ability. © 2007 Wiley Periodicals, Inc. 18:460,466, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20337 [source]


Mixed Isobutylphobane/N-Heterocyclic Carbene Ruthenium- Indenylidene Complexes: Synthesis and Catalytic Evaluation in Olefin Metathesis Reactions

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010
Xavier Sauvage
Abstract Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl2(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane)2(3-phenyl-1-indenylidene)] with a two-fold excess of the corresponding imidazol(in)ium-2-carboxylate zwitterions. Both products were characterized by 1H, 13C, and 31P,NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl2(isobutylphobane)(SIMes)(CH2)] derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins. [source]


Annealing effect of perfluorosulfonated ionomer membranes on proton conductivity and methanol permeability

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Yinghao Luan
Abstract Perfluorosulfonated ionomer (PFSI) was synthesized and PFSI membranes were prepared via a solution-cast method and annealed at different temperatures from 150 to 230°C. The annealing effect on water content, proton conductivity, and methanol permeability were reported and discussed. X-ray diffraction and small angle X-ray scattering were used to test the structure of the membranes. It was found that annealing increased the proton conductivity of the membranes because heat-treatment helped to free the sulfonic groups that were buried in the polymer segments and form more organized ionic clusters. Water content and methanol permeability of the annealed membranes decreased with increasing annealing temperature. Simultaneously, annealing induced more compact chain packing structure, which eventually affected the transport of the proton and methanol through these ionomer membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Wet scrubbing intensification applied to hydrogen sulphide removal in waste water treatment plant

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010
Pierre-François Biard
Abstract Hydrogen sulphide removal in a waste water treatment plant at semi-industrial scale in a compact wet scrubber has been investigated. The gas residence time in the scrubber was reduced to 30,ms using a NaOCl caustic scrubbing solution. The contactor is composed of a wire mesh packing structure where liquid and gas flow co-currently at high velocity (>12,m,s,1). H2S removal percentages higher than 95% could be achieved whereas a moderate pressure drop was measured (<4000,Pa). Both the hydrodynamic and chemical conditions can influence the efficiency of the process. Correlations were developed to predict both the pressure drop and the H2S removal efficiency at given operating conditions. Le traitement du sulfure d'hydrogène dans un laveur de gaz compact a été étudié à l'échelle semi-industrielle en station d'épuration. Le temps de contact dans le laveur est réduit à une trentaine de ms en utilisant une solution d'hypochlorite de sodium à pH basique. Le contacteur se compose d'une structure tissée métallique dans laquelle le gaz et le liquide circulent à co-courant et grande vitesse (>12,m,s,1). Un abattement de l'H2S de plus de 95% peut être obtenu avec une perte de charge modérée (<4000,Pa). A la fois les conditions chimiques et hydrodynamiques influencent les performances de traitement. Des corrélations ont été développées pour prédire la perte de charge mais aussi l'abattement dans des conditions opératoires données. [source]


On the packing structure of collagen: response to Okuyama et al.'s comment on Microfibrillar structure of type I collagen in situ

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009
Joseph.
A response is published to the comment by Okuyama et al. [(2009) Acta Cryst. D65, 1007,1008] on Microfibrillar structure of type I collagen in situ. [source]


Low Molecular Weight Gelators with Hexagonal Order in Their Liquid-Crystal Phases and Gel States: 5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones,

ADVANCED MATERIALS, Issue 10 2003
M. Hashimoto
5-Cyano-2-(3,4,5-trialkoxybenzoylamino)tropones form hexagonal structures in both liquid-crystalline and gel states. The Figure shows an environmental scanning electron microscopy image of octanol gels. Hydrogen bonding between the tropone carbonyl group and the NH group of troponoid amides plays an important role in flattening the molecules, allowing tighter packing structures and more stable columnar mesophases and gel states. [source]


N,N,N,,N,-Tetra­methyl­ethyl­ene­diammonium,succinate,succinic acid (1/1/1)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004
Giuseppe Bruno
In the title compound, C6H18N22+·C4H4O42,·C4H6O4, the components lie on centres of symmetry in space group , such that the asymmetric unit contains three half-mol­ecules. Despite the different mode (with respect to other di­carboxylic acids) adopted by the intermolecular self-interaction of succinic acid derivatives, the overall structure of the title compound consists of anionic layers that are typical of the packing structures exhibited by other di­carboxylic acid analogues. [source]