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151.
On encapsulation inside the supercage of zeolite‐Y planar Cu (II)–Schiff base complexes show the modified structural, optical and functional properties. The electronic effect of the different substituent groups present in the catalyst plays the decisive role towards their reactivity in the homogeneous phase but after the encapsulation in zeolite Y, reactivity is mainly governed by the molecular dimensions of the guest complexes rather than the electronic factor of the substituent groups attached on them. These systems are well characterized with the help of different characterization tools like XRD analysis, SEM ‐ EDX, AAS, FTIR, XPS, DSC, TGA, BET and UV–Visible spectroscopy and the comparative optical and catalytic studies have provided a rational explanation of enhanced reactivity of zeolite encapsulated metal complexes for various oxidation reactions compared to their corresponding solution states. 相似文献
152.
153.
Priyadarshini S. Sahoo Anuradha Panigrahi Sunanda K. Patri Rasm N. P. Choudhary 《Central European Journal of Physics》2010,8(4):639-642
A polycrystalline sample, Ba3Sr2DyTi3V7O30, with tungsten bronze structure was prepared by a mixed-oxide method at high temperature (950°C). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound was studied by scanning electron microscopy. The dielectric anomaly at 321°C may be attributed to the ferro-paraelectric phase transitions. This was also confirmed from the appearance of a hysteresis loop. The nature of variation of the ac conductivity and value of activation energy at different temperature regions, suggest that the conduction process is of mixed-type (i.e., ionic-polaronic and space charge generated from the oxygen ion vacancies). 相似文献
154.
155.
Ferheen S Ahmed E Malik A Afza N Lodhi MA Choudhary MI 《Chemical & pharmaceutical bulletin》2006,54(8):1088-1090
Hyperinols A (1) and B (2) are new taraxastane type triterpenes which have been isolated from the chloroform soluble fraction of Hypericum oblongifolium and their structures elucidated on the basis of spectroscopic data. Both showed significant inhibitory activity against chymotrypsin enzyme. 相似文献
156.
Khan SB Afza N Malik A Azhar-Ul-Haq Perveen S Ahmad I Ejaz A Choudhary MI 《Natural product research》2006,20(4):335-339
A new flavonol glycoside (1) has been isolated from the ethyl acetate soluble fraction of Amberboa ramosa and assigned the structure 5,7,4'-trihydroxy-3,8-dimethoxylflavone 5-O-beta-D-gluco-pyranoside (1). In addition, 6,4'-dihydroxy-3,5,7-trimethoxyflavone (2), 5,7-dihydroxy-4'-methoxyflavone (3) and (23R)-5alpha-cycloart-24-ene-3beta,21,23-triol (4) have also been reported for the first time from this species. The structures were deduced on the basis of 1D and 2D NMR techniques. The compounds 1-3 displayed weak to moderate inhibition against the xanthine oxidase enzyme. 相似文献
157.
Wansi JD Wandji J Kamdem WA Ndom JC Ngeufa HE Chiozem DD Chi Shirri J Choudhary MI Tsabang N Tillequin F Fomum ZT 《Natural product research》2006,20(6):586-592
The CH2Cl2/CH3OH (1/1) extract of the dried stem of Drypetes chevalieri Beille afforded two new triterpeno?ds named drypechevalin A (11-oxo-beta-amyrin-3beta-ylcaffeate) and drypechevalin B (3,7-dioxo-D:A-friedooleanan-24-al) along with five known compounds: lupeol, lupeone, erythrodiol, putranjivadione, friedelin. Their structures were established on the basis of spectroscopic analysis and chemical evidence. 相似文献
158.
Mostafa M Nahar N Mosihuzzaman M Sokeng SD Fatima N Atta-Ur-Rahman Choudhary MI 《Natural product research》2006,20(7):686-692
Quinovic acid-3-O-alpha-L-rhamnopyranoside (1), quinovic acid-3-O-beta-D-fucopyranoside (2), quinovic acid-3-O-beta-D-glucopyranosyl (1 --> 4)-beta-D-fucopyranoside (3), methyl gallate (4) and ethyl gallate (5) were isolated from the ethyl acetate extract of Bridelia ndellensis barks by fractionation. Compounds 1-3 showed significant inhibitory activity against snake venom phosphodiesterase-I. 相似文献
159.
Vasant R. Choudhary Suman K. Jana Mahesh K. Chaudhari 《Journal of molecular catalysis. A, Chemical》2001,170(1-2):251-259
Performance of In- and Ga-modified ZSM-5 type zeolites (namely, In2O3/H-ZSM-5, Ga2O3/H-ZSM-5, H-GaMFI and H-GaAlMFI) and InCl3 or GaCl3 supported on high silica mesoporous MCM-41 or on Mont.-K10 in the liquid phase polycondensation of benzyl chloride to polybenzyl has been investigated. Influence of solvent (namely, dichloroethane, n-heptane and ethanol) and temperature on the rate of polycondensation of benzyl chloride over the catalyst (InCl3/Si-MCM-41) showing highest polycondensation activity has also been studied. The In- and Ga-containing solid catalysts show good or high activity in the polycondensation reaction at the reaction condition normally employed in the benzylation of aromatic compounds by benzyl chloride. However, the polycondensation is strongly influenced by the solubility of the polybenzyl polymer in the reaction medium and consequently by the solvent used as the reaction medium. 相似文献
160.