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961.
The kinetic stopped flow method has been used to study the reaction rates of Ni(II) and Pd(II) with methioninehydroxamate (MX). Two reaction rates were observed in the MX? Ni(II) system whereas three rates were observed in the MX? Pd(II) system. Most of the rate steps were dependent on pH as well as on TMX (total concentration of methioninehydroxamate). The observed pseudo-first-order rate constants at constant pH are expressed empirically as k = mi + m′i TMX. The parameters mi and m′i are pH-dependent. It has been concluded that hydroxy metal species contributed to the explanation of the rate of the metal complexation with MX. Similar systems have been correlated with the systems of current work. © 1995 John Wiley & Sons, Inc. 相似文献
962.
T. Bonaventure Ngadjui J. Foyere Ayafor B. Lucas Sondengam Joseph D. Connolly David S. Rycroft Sami A. Khalid Peter G. Waterman Norman M.D. Brown Michael F. Grundon V.N. Ramachandran 《Tetrahedron letters》1982,23(19):2041-2044
Four new isomeric dimeric prenylated quinolone alkaloids, vepridimerines A-D, have been isolated from the bark of Vepris louisii and Oricia renieri (Rutaceae) and have been assigned structures (2)–(5) respectively on the basis of spectroscopic evidence, in particular1H and13C n.m.r. data. 相似文献
963.
Khan KM Saify ZS Begum S Noor F Khan MZ Hayat S Choudhary MI Perveen S Atta-Ur-Rahman Zia-Ullah 《Natural product research》2003,17(2):115-125
7-Hydroxy-4-methyl-2H-chromen-2-one (2), 7-hydroxy-4,5-dimethyl-2H-chromen-2-one (15) and their some derivatives were synthesized for exploring selected biological screening. The compounds 9 and 13 had shown high degree of cytotoxic activity. Three compound 9, 10 and 13 showed high degree of bactericidal activity amongst the present series. 相似文献
964.
Mohammed Ibrahim Walash Mohie Khalid Sharaf‐El‐Din Mohammed El‐Sayed Metwally Mostafa Reda Shabana 《中国化学会会志》2004,51(3):523-530
Two spectrophotometric methods were developed for the determination of ranitidine. The first method was a kinetic spectrophotometric method based on the catalytic effect of ranitidine on the reaction between sodium azide and iodine in an aqueous solution. The calibration graph was linear from 4–24 μg/mL. The drug was determined by measuring the decrease in the absorbance of iodine at 348 nm using a fixed time method. The decrease in the absorbance after 1 minute from the initiation of the reaction was related to the concentration of drug. The detection limit of the procedure was 0.76 μg/mL. The proposed procedure was successfully utilized in the determination of the drug in pharmaceutical preparations with mean recovery in the range of 99.83 ? 101.16%. The second method is a colorimetric method, which depends on the measurement of absorbances of tris (o‐phenanthroline) iron(II) [method 2A] and tris (bipyridyl) iron(II) [method 2B] complexes at 512 nm. The complexes obeyed Beer's law over the concentration range of 2–16 μg/mL and 4–40 μg/mL for methods 2A and 2B, respectively. The developed method has been successfully applied for the determination of ranitidine in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in its determination. 相似文献
965.
The electrophilic abstraction of chloride ion by SbCl5 from diphenylchloroborane in CD3NO2 resulted in a transient species of which 11B NMR chemical shift appeared at 20 ppm. This was indicative of diphenylboron cation, stabilized with electron donor O-atom of two nitromethane molecules. The experimental 11B chemical shift for the solvated diphenylboron cation is in good agreement with that calculated by GIAO-HF/6-311+G(2d,p)//B3LYP/6-31+G(d). 相似文献
966.
Substituted 3-amino-oxazolidin-2,4-diones have been prepared by reacting cyanohydrins or alpha-hydroxyesters subsequently with 1,1'-carbonyldiimidazole and 1,1-disubstituted hydrazines followed by acidic hydrolysis in case of the intermediate 3-amino-4-imino-oxazolidin-2-ones. Conventional and microwave-assisted syntheses of N',N'-disubstituted alpha-hydroxyhydrazides have been accomplished by reacting substituted 3-amino-oxazolidin-2,4-diones with catalytic amounts of sodium methoxide in methanol. 相似文献
967.
Kunieda H Rodriguez C Tanaka Y Kabir MH Ishitobi M 《Colloids and surfaces. B, Biointerfaces》2004,38(3-4):127-130
The effect of adding tri(oxyethylene) dodecyl ether (C12EO3) on the phase and rheological behavior of sucrose hexadecanoate and CTAB aqueous solutions in the presence of added salt (NaBr) was investigated. Viscoelastic solutions are formed in CTAB and C16SE systems upon addition of lipophilic nonionic surfactant C12EO3. The zero-shear viscosity shows a maximum at a certain mixing fraction of C12EO3, except in the case of the aqueous CTAB/C12EO3 system in the absence of salt. The rheological properties are strongly affected by the addition of salt to the CTAB systems but they remain unaltered in the case of C16SE systems. In ionic systems, the mixing fraction of C12EO3 for the maximum viscosity depends on salt concentration. 相似文献
968.
Chemoselective synthesis of benzimidazoles in good yield was achieved with a variety of aldehydes in heterogeneous media. This efficient procedure has been developed for the condensation of ortho-phenylene-diamine with aldehydes by silica-supported thionyl chloride in dichloromethane at ambient temperature. 相似文献
969.
Nazeeruddin MK Splivallo R Liska P Comte P Grätzel M 《Chemical communications (Cambridge, England)》2003,(12):1456-1457
Solar cells based on swift self-assembled sensitizer bis(tetrabutylammonium)-cis-di(thiocyanato)-N,N'-bis(4-carboxylato-4'-carboxylic acid-2,2'-bipyridine)ruthenium(II) (N719) on double layers of 12 + 4 microm thick nanocrystalline TiO2 films exhibit the incident monochromatic photon-to-current conversion efficiency (IPCE) 90% and show a short circuit current density of 17 mA cm(-2), 750 mV open circuit potential and 0.72 fill factor yielding power conversion efficiencies over 9.18% under AM 1.5 sun. For the first time highest power conversion efficiencies are obtained for dye sensitized solar cells using a swift self-assembled procedure. 相似文献
970.
John R. Finnegan Emily H. Pilkington Karen Alt Md. Arifur Rahim Stephen J. Kent Thomas P. Davis Kristian Kempe 《Chemical science》2021,12(21):7350
The morphology of nanomaterials critically influences their biological interactions. However, there is currently a lack of robust methods for preparing non-spherical particles from biocompatible materials. Here, we combine ‘living’ crystallisation-driven self-assembly (CDSA), a seeded growth method that enables the preparation of rod-like polymer nanoparticles, with poly(2-oxazoline)s (POx), a polymer class that exhibits ‘stealth’ behaviour and excellent biocompatibility. For the first time, the ‘living’ CDSA process was carried out in pure water, resulting in POx nanorods with lengths ranging from ∼60 to 635 nm. In vitro and in vivo study revealed low immune cell association and encouraging blood circulation times, but little difference in the behaviour of POx nanorods of different length. The stealth behaviour observed highlights the promising potential of POx nanorods as a next generation stealth drug delivery platform.Triggered by heating, a poly(2-alkyl-2-oxazoline) block copolymer undergoes seeded growth in water forming length tuneable nanorods. Morphology and composition combine to impart low immune cell association and promising blood circulation lifetimes. 相似文献