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111.
Biplab K. Bera Subhasis Mallick Arup Mandal Parnajyoti Karmakar Asok K. Datta Alak K. Ghosh 《Transition Metal Chemistry》2010,35(5):541-547
The kinetics of the aqua ligand substitution from hydroxopentaaquarhodium(III) ion, [Rh(H2O)5(OH)]2+, by l-Arginine has been studied spectrophotometrically as a function of Arginine concentration, and temperature, at pH 4.3. The
reaction proceeds via a rapid outer sphere association complex formation step followed by two consecutive steps. The first
of these involves ligand-assisted anation, while the second involves chelation as the second aqua ligand is displaced. The
association equilibrium constant for the outer sphere complex formation has been evaluated together with the rate constants
for the two subsequent steps. The activation parameters for both steps have been evaluated using Eyring’s equation. Thermodynamic
parameters calculated from the temperature dependence of the outer sphere association equilibrium constants are also consistent
with an associative mode of activation. The product of the reaction has been characterized by conductivity measurement and
IR spectroscopic analysis. 相似文献
112.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
113.
114.
Manoj K. Yadav Abhijit Mookerjee Biplab Sanyal 《Journal of magnetism and magnetic materials》2010,322(2):253-256
We show that the antiferromagnetic coupling between Mn atoms in MnO can be tuned to a ferromagnetic one by doping it with a small concentration of 2p elements like boron, carbon and nitrogen. Our ab initio density functional calculations in the Hubbard U framework show that the coupling between Mn atoms turns ferromagnetic for 3 at% B doping. B is found to be the most effective one in stabilizing ferromagnetism. We discuss the role of 2p states of the dopant atoms to explain the trend of ferromagnetism in MnO. 相似文献
115.
Maria Grazia Lupo Margherita Zavelani-Rossi Angela Fiore Dario Polli Luigi Carbone Roberto Cingolani Liberato Manna Guglielmo Lanzani 《Superlattices and Microstructures》2010
We studied the delocalization of electron wave function in asymmetric CdSe/CdS nanocrystals, consisting of a spherical CdSe dot embedded in an elongated CdS shell, by means of a pump–probe technique. By comparing the transient spectra obtained upon pumping the band edge transition of the CdSe in CdSe/CdS heterostructure and in a bare CdSe dot, we observed the delocalization of electron wave function at the CdSe/CdS interface. 相似文献
116.
F. Pisanello L. Martiradonna P. Spinicelli A. Fiore J.P. Hermier L. Manna R. Cingolani E. Giacobino M. De Vittorio A. Bramati 《Superlattices and Microstructures》2010
We report the evidence of a polarized single photon flux from a colloidal nanoparticle. We analyze, by time and polarization resolved spectroscopy measurements, the polarization behavior of a single CdSe/CdS core/shell dot in rod, achieving a polarization ratio at room temperature of ∼75% and a lifetime of the excited state of ∼11 ns. 相似文献
117.
The binding of chlorin p6, a photosensitizer having basic tetrapyrrole structure, to bovine serum albumin (BSA) and oxidation of the protein following photodynamic treatment is studied. The Stern-Volmer plot indicates that binding of chlorin p6 to BSA was of single class. Binding parameters, binding association constant and number of binding sites, were found to be 1.62+/-0.27 x 10(5)M(-1) and 1.086+/-.019, respectively. Photodynamic oxidation of protein was studied by (i) loss of intrinsic fluorescence of protein, (ii) protein carbonyl formation, (iii) protein hydroperoxide (iv) formation of TCA soluble amino groups and (v) SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Intrinsic protein fluorescence was observed to decrease almost linearly as a function of irradiation time at a fixed concentration of chlorin p6 and with increasing concentration of chlorin p6 at fixed time of irradiation. Protein carbonyl and hydroperoxide formation was found to increase with increasing photodynamic treatment. No significant increase in 5% TCA soluble amino groups was observed. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) reveals that photodynamic treatment of BSA in presence of chlorin p6, rose bengal and riboflavin causes non-specific fragmentation of protein. Photodynamic carbonyl formation by chlorin p6 was not inhibited by sodium formate (100 mM) or mannitol (25 mM) but was significantly inhibited by sodium azide (2 mM). Protein carbonyl formation increased almost 90% when H2O was replaced by D2O. The results show that chlorin p6 induced photodynamic oxidation of BSA was mainly mediated by singlet oxygen. 相似文献
118.
We present explicit forms of nonadiabatic coupling (NAC) elements of nuclear Schrodinger equation (SE) for a coupled three-state electronic manifold in terms of mixing angles of real electronic basis functions. If the adiabatic-diabatic transformation (ADT) angles are the mixing angles of electronic bases, ADT matrix transforms away the NAC terms and brings diabatic form of SE. ADT and NAC matrices are shown to satisfy a curl condition with nonzero divergence. We have demonstrated that the formulation of extended Born-Oppenheimer (EBO) equation from any three-state BO system is possible only when there exists a coordinate-independent ratio of the gradients for each pair of mixing angles. On the contrary, since such relations among the mixing angles lead to zero curl, we explore its validity analytically around conical intersection(s) and support numerically considering two nuclear-coordinate-dependent three surface BO models. Numerical calculations are performed by using newly derived diabatic and EBO equations and expected transition probabilities are obtained. 相似文献
119.
Poly(3-hexyl thiophene) (P3HT) organically modified montmorillonite (om-MMT) polymer nanocomposites (PNCs) are prepared in the melt-cooled state. Hierarchical structures up to third order, namely, side chain mesomorph formation followed by the interchain lamellar structure of P3HT and finally its intercalation within the clay tactoids are observed. The structures are supported by transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) experiments. The TGA curves show two-stage degradation corresponding to those of the side chain and main chain of P3HT, and both temperatures decrease with an increase in clay concentration in the PNCs. The melting points of PNCs have increased by 2-3 degrees C higher than that of P3HT. The glass-transition temperature (Tg) and beta-transition temperature (Tbeta), measured by DMA, increase with an increase in clay concentration. The storage modulus (G) of PNCs has also increased more dramatically than that of P3HT. The UV-vis spectra of the PNCs show a blue shift in the pi-pi* absorption peak of the conjugated chain, but the photoluminescence spectra showed a red shift with an increase in the clay concentration. The quantum yield of the photoluminescence process also increases in the melt-cooled PNCs, and this is in sharp contrast to that of solvent cast PNCs where photoluminescence quenching was observed. Fibrillar network structure of the solvent cast PNCs promotes energy transfer of the charge carriers, but its absence in the melt-cooled films inhibits such energy transfer, increasing the quantum yield. The room-temperature dc conductivity of the PNCs decreased by an order compared to that of P3HT in both the doped and undoped states. The I-V characteristic curve shows semiconducting behavior, and it slowly transforms into insulator with increasing clay concentration. 相似文献
120.
Dr. Madhu Sudan Manna Rahul Sarkar Prof. Dr. Santanu Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14912-14919
An enantioselective formal C(sp2)?H vinylation of prochiral 2,2‐disubstituted cyclopentene‐1,3‐dione is presented. This vinylative desymmetrization is realized by using a two‐step procedure that consists of a catalytic enantioselective vinylogous Michael addition of deconjugated butenolides to cyclopentene‐1,3‐dione and a base‐mediated decarboxylation. The overall process utilizes deconjugated butenolides as the source of the highly substituted vinyl unit. Five‐membered carbocycles containing a remote all‐carbon quaternary stereogenic center are obtained in good yields and with good to high enantioselectivities. 相似文献