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1.
Summary Rate constants for the oxidation of thiosulphate by hexachloroplatinate(IV) have been measured. The kinetics of the oxidation of thiosulphate follow a second-order rate law, first order with respect to thiosulphate and first order with respect to platinum(IV). The influence of pH is small. The rates are found to depend on the nature and concentration of the cations and follow the order: Cs+>Rb+>K+>Na+>Li+. The activation parameters calculated from the temperature studies are: H=42.9 k J mol–1 and S=–102 JK–1 mol–1. A mechanism of the reaction in terms of intermediate formation of free radicals followed by the formation of tetrathionate is postulated to explain the kinetic behaviour. 相似文献
2.
Shipra Mital Gupta 《High Energy Chemistry》2013,47(3):130-134
Nanoparticles of lead sulphide have been stabilized in the presence of excess Pb2+ in aqueous basic medium by a simple chemical route of synthesis. These PbS nanoparticles were synthesized very conveniently at room temperature using hexametaphosphate as stabilizer. These nanoparticles have an absorption extending into the NIR region. A significant quantum confinement effect made the bandgap of lead sulphide nanoparticles produce a blue shift from 0.41 eV to about 1.5 eV. The size and morphology of the particles were studied by TEM. Particles were relatively small sized (about 6 nm) having narrow size distribution. XRD data analysis indicate that the product is a mixture of PbS, PbO and Pb(OH)2. Both XRD pattern and HRTEM images confirm the crystalline structure of lead sulphide crystals. IR spectroscopy indicates the formation of PbS. PbS nanoparticles were fairly stable and could be stored for about three weeks at room temperature and for about two months at 5°C without agglomeration. These particles were photoactive and sensitized the reaction of aniline by light leading to the formation of azobenzene. 相似文献
3.
Kalyan Kali Sengupta Biswanath Basu Shipra Sengupta Sanghamitra Nandi 《Polyhedron》1983,2(10):983-986
Hypophosphite ion is oxidised by Au(III) in aqueous hydrochloric acid to give phosphorus acid and Au(I). The kinetics of the reaction has been studied spectrophotometrically in the UV region at different temperatures. The oxidation of hypophosphorous acid is first order with respect to both Au(III) and substrate. Hydrogen ion has no effect on the rate in acid media (0.15–1.0)M. The energy and entropy of activations are 128 ± 3.0kJ mol?1 and 135.8 ± 6.5 JK?1 mol?1 respectively. The results are interpreted in terms of the probable formation of intermediate Au(lI). 相似文献
4.
Alla Zablotskaya Izolda Segal Yuris Popelis Edmunds Lukevics Shipra Baluja Irina Shestakova Ilona Domracheva 《应用有机金属化学》2006,20(11):721-728
A series of triorganylsilyl(β‐dialkylaminoethoxy)silanes was prepared and characterized by elemental analysis, 1H, 13C, 29Si NMR and mass spectroscopy. Comparative study of 29Si resonance of newly synthesized compounds showed correlation between its value and substituent nature at the silicon atom, and is shifted upfield for β‐triorganyl(N,N‐dialkylaminoethoxy)silanes in comparison with corresponding methiodides, revealing weak N…Si interaction for proper silanes. In vitro antitumour and antimicrobial properties were investigated. The biological activity data exhibited a marked enhancement of inhibitory activity on trialkylsilylation against tumour cell lines and all the test bacterial/fungal strains. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
5.
Eugenio Daviso Shipra Prakash A. Alia Peter Gast Gunnar Jeschke J?rg Matysik 《Applied magnetic resonance》2010,37(1-4):49-63
Photochemically induced dynamic nuclear polarization (photo-CIDNP) is observed with time-resolved 15N magic-angle spinning (MAS) nuclear magnetic resonance (NMR) in uniformly 15N-labeled reaction centers (RCs) of the purple bacterium Rhodobacter (Rb.) sphaeroides R26 under illumination with nanosecond laser flashes. The 15N NMR signals enhanced by the solid-state photo-CIDNP effect are related to electron spin densities in the primary radical pair and allow for reconstruction of the electronic structure at atomic scale. New assignments for the photochemically active nitrogens are proposed based on simulations of the intensities. The ratio of electron spin densities between cofactors P L and P M is observed to be about 4:1. The origin of the high asymmetry is discussed. 相似文献
6.
Shipra Sagar Binitendra Naath Mongal Abhijit Dutta Paritosh Mondal William Lewis Nadis Saba 《Journal of Coordination Chemistry》2016,69(15):2364-2376
Schiff base pyridin-2-ylimino methyl naphthanol (HL) was synthesized and characterized by spectroscopic (FTIR, ESIMS, and NMR) techniques. The ligand was reacted with perchlorate salts of Mn+2, Co+2, and Ni+2. ESIMS mass spectra indicate the formation of mononuclear complex ML2 for all three complexes. CoL2 crystallizes in P21/n space group, adopting a distorted tetrahedral geometry where Co is in a N2O2 donor environment. Structure of the Co complex was optimized by DFT calculation. Solution-phase complexation between the ligand and the three metals ions: Mn+2, Co+2, and Ni+2 (pH 7.2 in tris buffer), in CH3CN–H2O was performed spectrophotometrically by UV–vis spectral study. Job’s plot from each titration suggests a 1 : 2 metal to ligand combination. The association constants for the formation of ML2 are as follows: Mn (19.80 × 103 M?1), Co (14.54 × 103 M?1) and Ni (19.04 × 103 M?1). 相似文献
7.
Kalyan Kali Sen Gupta Mrityunjoy Adbikary Subrata Kumar Mandal Shipra Sen Gupta 《Transition Metal Chemistry》1987,12(2):152-155
Summary The oxidation of MeCHO by chromium(VI) has been studied in HClO4 medium over a wide range of experimental conditions and has been found to obey the rate law;v=k[MeCHO][HCrO
4
–
][H+]. The calculated H
and-S
values for the reaction are 30±2kJ mol–1 and 171±7J mol–1deg–1, respectively. The mechanism is discussed in terms of carbon-hydrogen bond cleavage. 相似文献
8.
Natarajan B Gupta S Ramamurthy V Jayaraman N 《The Journal of organic chemistry》2011,76(10):4018-4026
This report deals with a study of the properties of internal cavities of dendritic macromolecules that are capable of encapsulating and mediating photoreactions of guest molecules. The internal cavity structures of dendrimers are determined by the interfacial regions between the aqueous exterior and hydrocarbon like interior constituted by the linkers that connect symmetrically sited branch points constituting the dendrimer and head groups that cap the dendrimers. Phloroglucinol-based poly(alkyl aryl ether) dendrimers constituted with a homologous series of alkyl linkers were undertaken for the current study. Twelve dendrimers within first, second, and third generations, having ethyl, n-propyl, n-butyl, and n-pentyl groups as the linkers and hydroxyl groups at peripheries in each generation, were synthesized. Encapsulation of pyrene and coumarins by aqueous basic solutions of dendrimers were monitored by UV-vis and fluorescence spectroscopies, which showed that a lower generation dendrimer with an optimal alkyl linker presented better encapsulation abilities than a higher generation dendrimer. Norrish type I photoreaction of dibenzyl ketone was carried out within the above series of dendrimers to probe their abilities to hold guests and reactive intermediate radical pairs within themselves. The extent of cage effect from the series of third generation dendrimers was observed to be higher with dendrimers having an n-pentyl group as the linker. 相似文献
9.
Prakash S Alia A Gast P de Groot HJ Matysik J Jeschke G 《Journal of the American Chemical Society》2006,128(39):12794-12799
Photochemically induced dynamic nuclear polarization (photo-CIDNP) is observed in photosynthetic reaction centers of the carotenoid-less strain R26 of the purple bacterium Rhodobacter sphaeroides by (13)C solid-state NMR at three different magnetic fields (4.7, 9.4, and 17.6 T). The signals of the donor appear enhanced absorptive (positive) and of the acceptor emissive (negative). This spectral feature is in contrast to photo-CIDNP data of reactions centers of Rhodobacter sphaeroides wildtype reported previously (Prakash, S.; Alia; Gast, P.; de Groot, H. J. M.; Jeschke, G.; Matysik, J. J. Am. Chem. Soc. 2005, 127, 14290-14298) in which all signals appear emissive. The difference is due to an additional mechanism occurring in RCs of R26 in the long-living triplet state of the donor, allowing for spectral editing by different enhancement mechanisms. The overall shape of the spectra remains independent of the magnetic field. The strongest enhancement is observed at 4.7 T, enabling the observation of photo-CIDNP enhanced NMR signals from reaction center cofactors in entire bacterial cells allowing for detection of subtle changes in the electronic structure at nanomolar concentration of the donor cofactor. Therefore, we establish in this paper photo-CIDNP MAS NMR as a method to study the electronic structure of photosynthetic cofactors at the molecular and atomic resolution as well as at cellular concentrations. 相似文献
10.
The depletion of non-renewable resources and rise in global warming has caused great concern to humankind. With a view to
use renewable source of energy and to eliminate hazardous chemical compounds from air, soil, and water, photocatalysis utilizing
solar energy is becoming a rapidly expanding technology. Semiconductor nanoparticles have the ability to undergo photoinduced
electron transfer to an adsorbed particle governed by the band energy positions of the semiconductor and the redox potential
of the adsorbate. A brief overview of metal oxides and sulphides that can act as sensitizers for light-induced redox processes
due to their electronic structure is presented here. 相似文献