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51.
The mechanism of the gold nanocluster‐catalyzed aerobic homocoupling of arylboronic acids has been elucidated by means of DFT calculations with Au20? as a model cluster for the Au:[poly(N‐vinylpyrrolidin‐2‐one)] catalyst. We found that oxygen affects the adsorption of phenylboronic acid and, by lowering the energy barrier, a water molecule enhances dissociation of the C?B bond, which is probably the rate‐determining step. The key role of oxygen is in activating the surface of the gold cluster by generating Lewis acidic sites for adsorption and activation of the phenylboronic acid, leading to the formation of biphenyl through a superoxo‐like species. Moreover, the oxygen adsorbed on the Au nanocluster can act as an oxidant for phenylboronic acid, giving phenol as a byproduct. As shown by NBO analysis, the basic aqueous reaction medium facilitates the reductive elimination process by weakening the Au?C bond, thereby enhancing the formation of biphenyl. The coupling of phenyl and reductive elimination of biphenyl occur at the top or facet site with low‐energy‐barrier through spillover of phenyl group on Au NC. The present findings are useful for the interpretation or design of other coupling reactions with Au NC. 相似文献
52.
53.
Mark Kristan Espejo Cabello Dr. Yuta Uetake Dr. Yu Yao Prof. Dr. Susumu Kuwabata Prof. Dr. Hidehiro Sakurai 《化学:亚洲杂志》2021,16(16):2280-2285
An aqueous colloidal dispersion of Pt nanoparticles (NPs) stabilized by fullerenol C60(OH)12 (Pt:C60(OH)12) was successfully synthesized via liquid-phase chemical reduction. The subsequent pyrolysis of Pt:C60(OH)12 at different temperatures was conducted to afford Pt-doped carbon with different chemical compositions (Pt:C60n). X-ray absorption spectroscopy (XAS) and Infrared (IR) absorption spectroscopy and thermogravimetric measurements revealed that the thus-prepared nanocomposite consists of Pt NPs and high valent Pt-C60(OH)12 complex. One distinct feature of C60(OH)12 matrix as catalyst support is the suppression of size growth of Pt NPs during the pyrolysis up to 300 °C. Electrochemical experiments using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were performed to find that Pt:C60300 (pyrolyzed at 300 °C) exhibited higher activity than others, that was attributed to the π-extended feature of the as-obtained carbon. 相似文献
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55.
Chemiluminescence from the reaction of calcium and aluminum with various hydrogen containing compounds in a flowing gas system and in a heat pipe oven are described. Red chemiluminescence of CaH was observed in the reaction of calcium, and weak chemiluminescence of AlH was seen in the reaction of aluminum with formaldehyde (H2CO). It is proposed that a reaction between metal atoms and formaldehyde may be used as a source of diatomic metallic hydrides. 相似文献
56.
Kajitani T Onouchi H Sakurai S Nagai K Okoshi K Onitsuka K Yashima E 《Journal of the American Chemical Society》2011,133(24):9156-9159
We report a unique macromolecule consisting of a rodlike helical polyisocyanide backbone with a narrow molecular weight distribution and rigid mesogenic chiral pendants linked via a flexible spacer that exhibits lyotropic nematic and latticelike new smectic (lat-Sm) liquid crystal phases at different concentrations. The unprecedented lat-Sm phase is associated with the smectic ordering of both the stiff polymer backbone and the rigid-rod side groups. A detailed investigation of the films using X-ray scattering and atomic force microscopy revealed a novel tilted smectic layer structure of the polymer backbone aligned perpendicular to the smectic layer of the mesogenic pendants, which arrange in an antiparallel overlapping interdigitated manner. 相似文献
57.
T Nishi F Saito H Nagahori M Kataoka Y Morisawa Y Yabe M Sakurai S Higashida M Shoji Y Matsushita 《Chemical & pharmaceutical bulletin》1990,38(1):103-109
Syntheses and biological activities of dipeptide renin inhibitors that contain statine analogues are described. The key steps of the synthetic approach to dipeptide renin inhibitors are the asymmetric synthesis of 2(R)-substituted-3-aminocarbonylpropionic acids and the diastereoselective syntheses of (3S,4S)-statine analogues. These inhibitors (2,14-40) inhibited human renin in the 3-140 nM range. Inhibitor ES 6864 (2) was found to be a highly potent inhibitor of human renin (IC50: 4.6 x 10(-9) M) and showed high enzyme specificity. Oral administration of ES 6864 at 3 mg/kg to conscious, sodium-depleted marmosets inhibited plasma renin activity (PRA) more than 80% after 1 h. 相似文献
58.
The title compound shows dual fluorescence depending on polarity of the solvent used. The fluorescence in the nonpolar solvent, cyclohexane, has a maximuni at 370 nm, while the fluorescence in the polar solvent, methanol, has a maximum at 400nm. The short and long wavelength fluorescences were assigned to the syn and anti conformers, respectively. From these observations one is allowed to conclude that a novel solvent dipole-induced rotational isomerism takes place in the excited singlet state. 相似文献
59.
Aniruddha Deb M. Itou Y. Sakurai N. Hiraoka N. Sakai 《Radiation Physics and Chemistry》2001,61(3-6):545-546
The spin density of Heusler alloy Co2FeGa, has been studied using the Compton scattering technique with 274 keV circularly polarized synchrotron radiation in the high energy inelastic scattering beamline (BL08W), at SPring-8, Japan. The magnetic Compton profiles along the two principal directions [1 1 0] and [1 1 1] were measured. The spin profiles shows a good agreement with our FLAPW-GGA results, where the theoretical results were based on the ferromagnetic ground state. The 3d spin moment at the Co and the Fe site was found to be in excellent agreement with the earlier reported neutron diffraction measurements. 相似文献
60.
High-performance liquid chromatography was used to determine cyclosporin A (CsA) concentrations in the serum of kidney transplant patients by rapid-flow fractionation (RFF) followed by silica gel normal-phase high-performance liquid chromatography (HPLC). The extraction of CsA from serum was achieved by RFF using a short diatomaceous earth column eluted with diethyl ether-n-hexane (50:50, v/v). The recovery was more than 80% at concentrations of 50-150 micrograms/l. The concentration of this compound was determined by HPLC using a conventional silica gel column with 3.3 M ammonia solution-ethanol-n-hexane (0.31:10.69:89, v/v) as eluent. Concentration calibration was made on the basis of the peak-height ratio of CsA to CsD as the internal standard. The coefficient of variation of this assay was less than 6.5% and the results were used for the therapeutic drug monitoring of CsA administered to kidney transplant patients. Measurements of the CsA concentrations in 160 serum specimens were also made by conventional radioimmunoassay (RIA) using commercial kits. The data obtained by RIA were on average 2.5 times those obtained by HPLC. Higher values in RIA were observed characteristically with patients with severe disfunction resulting from CsA hepatotoxicity. From the results, it appeared that HPLC rather than RIA provides more precise and reliable values for the concentration of this drug. 相似文献