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排序方式: 共有154条查询结果,搜索用时 31 毫秒
61.
The efficient use of cellulose sulfuric acid as a heterogeneous catalyst promotes three-component, one-pot Mannich reaction of various ketones, aromatic aldehydes, and aromatic amines in ethanol to make the corresponding β-amino ketones with high stereoselectivity in favor of the anti-isomer. This protocol has several advantages such as good yield, mild reaction conditions, no environmental hazards, and simple workup procedure. 相似文献
62.
The mechanism of the interaction between bovine serum albumin (BSA) and [Pt(phen) (histidine)]+ complex was studied employing ultraviolet (UV) absorption, circular dichroism (CD), FT-IR, differential pulse voltammetry (DPV), and fluorescence spectral methods. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by Pt(II) complex in terms of an untypical static quenching process. The corresponding number of binding sites (n) and binding constant (K b) of BSA and complex at 283, 298, and 310 K were calculated to be 0.61?×?106, 19?×?106, and 42?×?106 M?1, respectively. The results showed that the increasing temperature improves the stability of the complex–BSA system, which results in a higher binding constant and the number of binding sites of the complex–BSA system. The positive ΔH and positive ΔS indicated that hydrophobic forces might play a major role in the binding between complex and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance (r) between the donor (BSA) and acceptor (Pt(II) complex) was evaluated. The results of CD, UV–vis, DPV, and FT-IR spectroscopy showed that the binding of Pt(II) complex to BSA induced conformational changes in BSA 相似文献
63.
Kharat A. Nemati Abedini M. Amini M. Mohammadpour Pendleton P. Badalyan A. 《Transition Metal Chemistry》2003,28(3):339-344
Preyssler heteropolytungstophosphate anions with different counter ions, X
x
M
y
[NaP5W30O110], where X = H and M = Cs, Ba, La, Ce, Hg, Tl, Pb and Bi, were prepared and the effect of the counter ion on their behavior was investigated by i.r. spectroscopy, surface area measurements (BET), simultaneous thermal analysis (STA), cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Thermal analyses indicate that the Ce derivative has the highest and the Hg derivative the lowest thermal stability. Only the Cs, Ba and Tl salts show measurable surface area. All heteropolyanions with similar i.r. spectra and electrochemical behavior demonstrate that the heteropolyanion structures are retained. The X-ray photoelectron spectra of the heteropolyacid salts reveal high binding energies for counter ions in comparison with classic salts and strong interaction of counter ion with the oxo oxygen's for H+ and Cs+ derivatives. 相似文献
64.
Mohammad A. Bigdeli Shahram Moradi Firouzeh Nemati 《Journal of Molecular Structure》2008,860(1-3):64-79
Ab initio calculation at HF/6-31G* and MP2/6-31G* levels of theory for geometry optimization of some syn- and anti-1,8-di-pyridine 9H-fluorene, dibenzo[b,d]furan, 9H-carbazole and Dibenzo[b,d]thiophene are reported. The rotational barrier energy, heat of formation and Gibbs energy are determined for the conversion of the anti-(syn) to the syn (anti)-isomers at 25 °C in the gas phase. The models are chosen as isomers of 9H-fluorene, dibenzo[b,d]furan, 9H-carbazole and dibenzo[b,d]thiophene as scaffold with pyridine as module. Results obtained show that (at equilibrium) for most of atropisomers the syn- is favored over the anti-isomer. Moreover, the ground state structures show that the modules are not parallel to each other but are tilted away in order to increase separation and there by minimize electrostatic repulsion. In atropisomers of 9H-carbazole the isomers are showing an attraction due to the presence of nitrogen atom. Influence of the position of nitrogen atom on the magnitude of the rotational barriers in these atropisomers is also studied. 相似文献
65.
Farhad Heidary Ali Nemati Kharat Ali Reza Khodabakhshi 《Journal of Cluster Science》2016,27(1):193-211
A new type of ion-exchange nanocomposite membranes was prepared by addition of barium ferrite nanoparticles to a blend containing sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) and sulfonated polyvinylchloride via a simple casting method. Hard magnetic BaFe12O19 nanoparticles were synthesized via a facile sonochemical-assisted reaction. Nanoparticles and nanocomposites were then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and alternating gradient force magnetometer. Various characterizations revealed that the addition of different amounts of inorganic fillers could affect the membrane performance. The inorganic nanoparticles not only created extra pores and water channels that led to improve ion conductivity, but also provided higher permselectivity and transport number of counter-ions. 相似文献
66.
Nano‐Fe3O4@TiO2/Cu2O Core‐shell Composite: A Convenient Magnetic Separable Catalyst for A3 and KA2 Coupling
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An eco‐efficient one‐pot three component reaction between different aldehydes or ketones with alkynes and amines for the synthesis of propargylamines was performed using Fe3O4@TiO2/Cu2O as a nano‐magnetic composite under solvent free condition. The catalyst showed remarkable catalytic activity by decreasing the time of the reaction in comparison of other reported magnetic catalysts. In addition, the Fe3O4@TiO2/Cu2O can be easily recycled and reutilized for five times without apparent loss of catalytic activity. 相似文献
67.
Rueping M Sugiono E Theissmann T Kuenkel A Köckritz A Pews-Davtyan A Nemati N Beller M 《Organic letters》2007,9(6):1065-1068
The enantioselective Br?nsted acid catalyzed addition of methyleneaminopyrrolidine to N-Boc imines has been achieved in the presence of chiral phosphoric acids derived from 3,3'-di(phenanthryl)-H8-BINOL. The corresponding aminohydrazones have been isolated in good yields with enantiomeric excesses up to 90%. [reaction: see text] 相似文献
68.
Amorphous barium titanate nanothin films were prepared by sol–gel dip-coating method. According to transmission spectrum, the refractive index and optical band gap of nanothin films have been determined. High transmission spectrum without any fluctuation in visible wavelength region was recorded. Experimental results indicated that the surface morphology of prepared nanothin films were improved and as a result of that, a better optical properties, less optical losses and higher band gap width were obtained in contrast with other reported data. It was found that optical propagation loss of BaTiO3 nanothin film was much lower than normal polycrystalline BaTiO3 thin film. It seems to us that, amorphous barium titanate nanothin films would be suitable for several applications. 相似文献
69.
A macroscopic nonlocal theory of sound propagation in homogeneous rigid-framed porous media permeated with a viscothermal fluid has been recently proposed in this journal. It accounts for the first time for the full temporal and spatial dispersion effects, independently of the nature of the microgeometry. In this paper this new Maxwellian theory is validated in the case of sound propagation in cylindrical circular tubes, by showing that it matches exactly the long-known direct Kirchhoff–Langevin’s solutions. 相似文献
70.