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71.
72.
Alshahateet Solhe F. Bishop Roger Craig Donald C. Scudder Marcia L. Ung Alison T. 《Structural chemistry》2001,12(3-4):251-257
Dialcohol host 2,7-dimethyltricyclo[4.3.1.03,8]undecane-syn-2,syn-7-diol 1 can form either ellipsoidal clathrate or helical tubulate inclusion compounds where only dispersion forces operate between the hosts and guests. The former (tetragonal space group I41/acd), built from two interpenetrating sublattices containing both diol enantiomers, encloses the guests in rugby ball-shaped cavities. The latter (trigonal space group P3121 or P3221), containing only one diol enantiomer, traps the guests within parallel tubes. Which inclusion type is produced is determined by the guest size and shape and, hence, control is possible over these structures. At room temperature, cyclohexane gives the tetragonal structure, but fluorocyclohexane yields the trigonal structure. Chloroform produces both pseudopolymorphs: the tetragonal form at higher and the trigonal form at lower temperatures. Powder and single-crystal structural X-ray data are reported for these clathrate compounds. 相似文献
73.
Marcia Araque-Marin Fabio Bellot Noronha Mickel Capron Franck Dumeignil Michle Friend Egon Heuson Ivaldo Itabaiana Jr. Louise Jalowiecki-Duhamel Benjamin Katryniok Axel Lfberg Sbastien Paul Robert Wojcieszak 《Molecules (Basel, Switzerland)》2022,27(12)
The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass. 相似文献
74.
A characterization of the iron phases precipitated from aerated solutions of iron(II) sulfate heptahydrate was made using Mössbauer spectroscopy. The experimental conditions for the preparation of the samples were varied. The results are used to the further understanding of rust formation during atmospheric corrosion. 相似文献
75.
The LBLT factorization of Bunch for solving linear systems involving a symmetric indefinite tridiagonal matrix T is a stable, efficient method. It computes a unit lower triangular matrix L and a block 1 × 1 and 2 × 2 matrix B such that T=LBLT. Choosing the pivot size requires knowing a priori the largest element σ of T in magnitude. In some applications, it is required to factor T as it is formed without necessarily knowing σ. In this paper, we present a modification of the Bunch algorithm that can satisfy this requirement. We demonstrate that this modification exhibits the same bound on the growth factor as the Bunch algorithm and is likewise normwise backward stable. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
76.
Marcia M. Meier Luiz A. Kanis Joo C. de Lima Alfredo T. N. Pires Valdir Soldi 《先进技术聚合物》2004,15(10):593-600
The influence of the plasticizer content and film preparation procedure on the morphology, density, thermal and mechanical properties of cellulose acetate (CA) films plasticized with poly‐(caprolactone triol) (PCL‐T), were studied. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD) and infrared spectroscopy (FT‐IR) techniques were used. The films were prepared by dry‐casting CA and CA/PCL‐T in acetone or acetone/water solutions, which produced transparent and opaque films, respectively. In contrast to the transparent films, which were dense, the opaque films presented a porous morphology. However, the presence of PCL‐T reduced the opaque film porosity, increasing, in consequence, its bulk density. The TMA results revealed that PCL‐T reduced the glass transition temperature more significantly in the transparent than in opaque films. Only the transparent CA/PCL‐T films presented a melting temperature, that reduced with higher concentrations of PCL‐T, suggesting a higher ordering (crystallinity) when the films were prepared in the absence of water, as observed from WAXD curves. The mechanical properties also showed that the transparent films were more soft and tough than the opaque films. In summary, PCL‐T was a good plasticizer agent for CA films due to the presence of hydrogen bonds between the components (FT‐IR spectra). The presence of water in the dry casting process has a significant effect mainly on film morphology and mechanical properties. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
77.
Payne MM Parkin SR Anthony JE Kuo CC Jackson TN 《Journal of the American Chemical Society》2005,127(14):4986-4987
We present the device parameters for organic field-effect transistors fabricated from solution-deposited films of functionalized pentacene and anthradithiophenes. These materials are easily prepared in one or two steps from commercially available starting materials and are purified by simple recrystallization. For a solution-deposited film of functionalized pentacene, hole mobility of 0.17 cm2/V.s was measured. The functionalized anthradithiophenes showed behavior strongly dependent on the substituents, with hole mobilities as high as 1.0 cm2/V.s. 相似文献
78.
We report the synthesis and characterization of a series of alkoxy-substituted silylethynylated pentacene derivatives (R = CH(2)CH(2), CHCH, CH(2)). All three compounds are easily prepared, soluble in common organic solvents, and stable both as solids and in solution. Two of the derivatives possess significant pi-face interactions in the crystal. Values for lambda(max) for these new pentacene derivatives range from 621 to 674 nm, and oxidation potentials lie between 109 and 301 mV versus ferrocene. 相似文献
79.
The diols 7-11 have been synthesized, and their X-ray crystal structures determined, to learn how to influence and control lattice hydroxy group hydrogen bonding using crystal engineering ideas. To obtain new lattice inclusion hosts precise structural rules can be defined which enable the necessary supramolecular interactions to be duplicated. In this manner the helical tubuland 10 and ellipsoidal clathrate 11 hosts were obtained for the first time and their chloroform inclusion compounds characterized. New synthetic routes were utilized to obtain the bicyclo[3.3.2]decane and 9-thiatricyclo[4.3.1.1(3,8)]undecane frameworks present in these compounds. The solid-state conformations of bicyclo[3.3.2]decane derivatives 9 and 10 are compared with prior predictions and studies made on this uncommon ring system. 相似文献