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31.
Ellis WW Miedaner A Curtis CJ Gibson DH DuBois DL 《Journal of the American Chemical Society》2002,124(9):1926-1932
The hydride complex [Pt(dmpe)2H]+ (dmpe = 1,2-bis(dimethylphosphino)ethane) reversibly transfers H- to the rhenium carbonyl complex [CpRe(PMe3)(NO)(CO)]+, giving the formyl CpRe(PMe3)(NO)(CHO). From the equilibrium constant for the hydride transfer (16.2), the DeltaGdegrees for the reaction was determined (-1.6 kcal/mol), as was the hydride-donating ability of the formyl (44.1 kcal/mol). The hydride-donating ability, DeltaGdegrees(H-), is defined as the energy required to release the hydride ion into solution by the formyl complex [i.e. M(CHO) right arrow M(CO)+ + H-]. Subsequently, the hydride-donating ability of a series of formyl complexes was determined, ranging from 44 to 55 kcal/mol. With use of this information, two rhenium carbonyl complexes, [CpRe(NO)(CO)2]+ and [Cp*Re(NO)(CO)2]+, were hydrogenated to formyls, employing [Pt(dmpp)2]2+ and Proton-Sponge. Finally, the E(1/2)(I/0) values for five rhenium carbonyl complexes were measured by cyclic voltammetry. Combined with the known DeltaGdegrees(H-) values for the complexes, the hydrogen atom donating abilities could be determined. These values were all found to be approximately 50 kcal/mol. 相似文献
32.
Six X-ray crystal structures are reported, all containing substituted triphenylmethanol derivative 4 either alone or as its mono or bis(chromium tricarbonyl) complexes. All four chromium complexes studied crystallize with two independent molecules in the crystallographic asymmetric unit. It is demonstrated that from the X-ray crystal structure of the acentric racemic (+/-)-(1pR,1' 'R)(1pS,1' 'S)-[Cr(CO)(3)(eta(6)-t-BuC(6)H(3)(CMeOMe)CPh(2)OH)], (+/-)-3, it is possible to deduce the 4-fold helical structure of the chiral (-)-(1pR,1' 'R) isomer, (-)-3. The bimetallic derivatives demonstrate the ability to control intermolecular interactions by the positioning of relative stereochemistry. 相似文献
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K. C. Mishra B. N. Dev S. M. Mohapatra W. M. Gibson T. P. Das 《Hyperfine Interactions》1983,16(1-4):997-1000
The electronic energy levels and wave functions of fluorine and chlorine atoms adsorbed at the <111> surface of silicon are obtained by the Hartree-Fock procedure applied to clusters simulating the surface structure. Minimising the total energy with respect to the positions of the halogen atoms, the Si-Cl distance in the adsorbed system was found to be in good agreement with that from a recent SEXAFS measurement, there being no corresponding data presently available for fluorine on silicon surface. The calculated19 f * nuclear quadrupole coupling constants using the electronic wave functions for SiH3F and the larger cluster Si4H9F, simulating the surface, differed substantially in contrast to the situation for the Si-F distance, indicating that the quadrupole coupling is a more sensitive indicator of the adequacy of the cluster chosen to represent the surface system. Experimental results for the coupling constants are awaited for comparison with theory. 相似文献
34.
Sebastian G. Spain Matthew I. Gibson Neil R. Cameron 《Journal of polymer science. Part A, Polymer chemistry》2007,45(11):2059-2072
Glycopolymers are receiving increasing interest due to their application in areas, such as glycomics, medicine, biotechnology, sensors, and separation science. Consequently, new methods for their synthesis are constantly being developed, with an increasing emphasis on the preparation of well-defined polymers and on the production of complex macromolecular architectures such as stars. This review covers recent developments in the synthesis of glycopolymers, with a particular emphasis on (i) the use of controlled radical polymerization to prepare well-defined glycopolymers from unprotected monomers and (ii) postpolymerization modification strategies using reactive polymer precursors (including “click” reactions). Recent work on the production of glycosylated polypeptides, which are under investigation as mimics of naturally occurring glycoproteins, is also included. The authors offer some suggestions as to future developments and remaining challenges in this topical area of polymer chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci PartA: Polym Chem45: 2059–2072, 2007 相似文献
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Herman Ziffer Kuninbu Kabuto D.T. Gibson V.M. Kobal Donald M. Jerina 《Tetrahedron》1977,33(19):2491-2496
The absolute stereochemistry of a series of 3-substituted cis-dihydrodiols obtained by microbial oxidation of toluene, ethylbenzene, chlorobenzene, and biphenyl has been assigned from chemical and spectrophotometric studies. ?-Halogenated toluenes also have been investigated as substrates in these oxidations, and the corresponding cis-dihydrodiols isolated. Implications from the observation that some of the cis-dihydrodiols are racemic are discussed. Oxidation of an olefin, (±)-3-methylcyclohexene, by these microorganisms leads only to cis-diols whose absolute stereochemistry about the hydroxyl-bearing carbons is the same as that found for the cis-dihydrodiols formed from the aromatic substrates. 相似文献
37.
Scott L. Gibson Marwan K. Al-Shawi Alan E. Senior Russell Hilf 《Photochemistry and photobiology》1995,61(4):390-396
Abstract— The effectiveness of photodynamic therapy against P-glycoprotein ATPase activity in multidrug-resistant cells was studied. Chinese hamster ovary AUXB1 (drug-sensitive) and CR1R12 (multidrug-resistant) cell lines were compared with respect to uptake of 14 C-polyhematoporphyrin and porphyrin photosensitization. Phototoxicity of Photofrin® was similar in both cell lines, and no major differences in uptake or efflux of 14 C-polyhematoporphyrin were observed. Porphyrin photosensitization in vitro of CR1R12 cells or isolated plasma membranes from these cells caused inhibition of P-glycoprotein ATPase activity. Application of porphyrin photosensitization at a sublethal level to CR1R12 cells resulted in a small but significant increase in adriamycin-induced cytotoxicity. The hydrophobic "picket-fence" porphyrin, meso -tetrakis-( o -propionamidophenyl)porphyrin,α,α,α,β-isomer, was more inhibitory toward P-glycoprotein ATPase activity than the two less hydrophobic porphyrins tetraphenylporphine tetrasulfonate and Photofrin®. 相似文献
38.
A method is described for the determination of anionic detergents. The detergent anions are extracted into chloroform as an ion-association compound with the bis(ethylenediamine)copper(II) cation. Determinations are completed by colorimetry or atomic absorption spectrometry. With a 150-ml water sample, the limit or detection is 0.03 μg ml-1 (as LAS) for colorimetry or 0.06 μg ml-1 for a.a.s. The method requires only one phase separation step and is highly selective. It is directly applicable to brine and sea-water samples. 相似文献
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