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931.
Yongjin Xu Beisheng Kang Xuetai Chen Yuanba Cai Yonghan Hu Jiaxi Lu 《Journal of Cluster Science》1992,3(2):167-177
Complex Co4mp4(Hmp)(PBu
3
n
)3 (1) (H2mp=o-Mercaptophenol) was obtained from the reaction of CoCl2 and H2mp in the presence of PBu
n
3 and NaOMe with restricted oxidation. X-ray crystallographic data: triclinic, space group
,a=15.657(5) Å,b=20.469(8) Å,c=12.383(3) Å,=93.59(3)°, =112.45(2)°, =93.65(3)°,V=3648.7 Å3,Z=2,D
c
=1.33 g/cm3;R=0.065. The molecule consists of four cobalt atoms unsymmetrically bridged by S or S and O atoms from four of the five mp ligands. The fifth mp is terminally chelated to Co(4) which is in a distorted trigonal bipyramidal geometry, while Co(1)-Co(3) are square pyramidal. Atom Co(2) is bonded to Co(1) and Co(3) (average distance 2.632 Å) with strong interactions while Co(4) is only loosely connected to Co(1) (3.402 Å) and Co(3) (2.956 Å) through oxygen bridges and a hydrogen bond. The different coordination environments O2S2P, S4P, and O4S of the cobalt atoms make the molecule highly asymmetrical. XPS fitting data confirm the difference of the Co atoms. FABMS data indicate the possible fragmentation routes. The complex is paramagnetic with eff=5.2 B. 相似文献
932.
933.
聚丙烯酰胺对石油磺酸盐/正丁醇混合胶束体系流变性的影响 总被引:1,自引:0,他引:1
研究了一定矿化度下,不同分子量、不同水解度的聚丙烯酰胺对石油磺酸盐/正丁醇混合胶事体系的流型、粘度等充变性质的影响。 相似文献
934.
Stereochemistry plays a major role in the selectivity toward zinc ion over copper(II) of some tripodal ligands with a central piperidine scaffold, one of which acts as a fluorescent zinc sensor with nanomolar sensitivity. 相似文献
935.
Based on the QM/MM optimized X-ray crystal structure of the photosynthetic reaction center (PRC) of purple bacteriaRhodopseudomonas (Rps.)viridis, quantum chemistry density functional method (DFT, B3LYP/6-31G) has been performed to study the interactions between the pigment molecules and either the surrounded amino acid residues or water molecules that are either axially coordinated or hydrogen bonded with the pigment molecules, leading to an explanation of the mechanism of the primary electron-transfer (ET) reactions in the PRC. Results show that the axial coordination of amino acid residues greatly raises theE LUMO of pigment molecules and it is important for the possibility of ET to take place. Different hydrogen bonds between amino acid residues, water molecules and pigment molecules decrease theE LUMO of the pigment molecules to different extents. It is crucial for the ET taking place from excited P along L branch and sustains that the ET is a one-step reaction without through accessory bacteriochlorophyll (ABChl b). It is insufficient to treat the whole protein surrounding as a homogeneous dielectric medium. 相似文献
936.
Volatile Au species in an acidified medium were generated at room temperature by reduction with NaBH4 in acidified aqueous medium using a flow-injection chemical vapor-generation atomic absorption spectrometric (FI-CVG-AAS) system in the presence of micro amounts of sodium diethyldithiocarbamate (DDTC). Precision of 2.0% RSD (n = 11, 2.0 mg L(-1) level) was obtained at a sample throughput of 180 h(-1). A detection limit of 24 ng mL(-1) (3sigma) was obtained with 300 microL sample solution. The method was used for the determination of gold in ore sample digests, and the results obtained agreed well with those obtained by flame AAS. 相似文献
937.
938.
Xu Y Eilers G Borgström M Pan J Abrahamsson M Magnuson A Lomoth R Bergquist J Polívka T Sun L Sundström V Styring S Hammarström L Akermark B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(24):7305-7314
To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these complexes, a mixed-valent dinuclear Ru2(II,III) moiety with one phenoxy and two acetato bridges is covalently linked to a Ru(II) tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru2(II,III) and Ru2(III,III) states, respectively. This could allow for photooxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intramolecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)3]2+ photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO2, and the desired electron transfer from the excited state of the [Ru(bpy)3]2+ moiety to the conduction band of TiO2 followed by intramolecular electron transfer from the dinuclear Ru2(II,III) moiety to photogenerated Ru(III) was observed. The resulting long-lived Ru2(III,III) state decays on the millisecond timescale. 相似文献
939.
The shear viscosity of liquid copper is studied using nonequilibrium molecular-dynamics simulations under planar shear flow conditions. We examined variation of viscosity as function of shear rate at a range of pressures (ca. 0 - 40 GPa). We analyzed these results using eight different phenomenological models and find that the observed non-Newtonian behavior is best described by the Powell-Eyring (PE) model: eta(gamma) = (eta(0)-eta(infinity))sinh(-1)(taugamma)(taugamma) + eta(infinity), where gamma is the shear rate. Here eta(0) (the zero-shear-rate viscosity) extracted from the PE fit is in excellent agreement with available experimental data. The relaxation time tau from the PE fit describes the shear response to an applied stress. This provides the framework for interpreting the shear flow phenomena in complex systems, such as liquid metal and amorphous metal alloys. 相似文献
940.