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81.
The N-heterocyclic carbene, imidazole-2-ylidene, and its main group (13-15) analogues contain cyclically conjugated 6π electrons. Experimental 1H nuclear magnetic resonance (NMR) spectra suggest an increase in aromaticity along a period from left to right. Whereas the order along a group is as follows: period 2 > period 5 > period 4 > period 3 due to change in structure. To understand the order of aromaticity, the magnetically induced ring currents of the molecules are calculated using aromatic ring current shielding, gauge-including magnetically induced currents (GIMIC) method and Stanger's σ-model applying the gauge-including atomic orbitals NMR technique. It is found that GIMIC best describes the order of aromaticity especially along a group where current-profile changes on the bivalent atom down a group due to change in electron density. Moreover, the GIMIC provides the visualization of current by sign modulus and the anisotropy of the induced current density plots. 相似文献
82.
Dr. Aloysius Siriwardena Kiran Kumar Pulukuri Pancham S. Kandiyal Dr. Saumya Roy Dr. Omprakash Bande Dr. Subhash Ghosh Dr. José Manuel Garcia Fernández Dr. Fernando Ariel Martin Dr. Jean‐Marc Ghigo Dr. Christophe Beloin Dr. Keigo Ito Dr. Robert J. Woods Dr. Ravi Sankar Ampapathi Dr. Tushar Kanti Chakraborty 《Angewandte Chemie (International ed. in English)》2013,52(39):10221-10226
83.
When contributors to a common cause (or public good) are uncertain about each others’ valuations, early contributors are likely
to be cautious in free-riding on future contributors. Contrary to the case of complete information, when contributors have
independent private valuations for the public good, the expected total contribution generated in a sequential move game may
be higher than in a simultaneous move game. This is established in a conventional framework with quasi-linear utility where
agents care only about the total provision of the public good (rather than individual contribution levels) and there is no
non-convexity in the provision of the public good. We allow for arbitrary number of agents and fairly general distribution
of types. 相似文献
84.
85.
Subhasis Mallick Subala Mondal Arup Mandal Biplab K. Bera Parnajyoti Karmakar Alak K. Ghosh 《国际化学动力学杂志》2011,43(9):498-506
The kinetics of the interaction of three glycine‐containing dipeptides, namely, glycine‐L‐leucine (Gly‐Leu), glycine‐L‐isoleucine (Gly‐Ile), and glycine‐valine (Gly‐Val) with [Pt(en)(H2O)2](ClO4)2 has been studied spectrophotometrically as a function of [substrate complex], [dipeptides] and temperature at a particular pH(4.0), where the substrate complex exists predominantly as the diaqua species and the dipeptides as a zwitterion. The substitution reaction shows two consecutive steps; the first is the ligand‐assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring's equation. The low ΔH1≠ and large negative value of ΔS1≠ as well as ΔH2≠ and ΔS2≠ indicate an associative mode of activation for both the aqua ligand substitution processes. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 498–506, 2011 相似文献
86.
Steady-state and time-resolved techniques are used to study photoinduced electron and/or excitational energy transfer processes involved within a novel donor (zinc tetraphenylporphyrin)-acceptor (9-cyanoanthracene) system in a polar liquid medium (acetonitrile) at the ambient temperature (300 K). After photoexcitation of 9-cyanoanthracene, its fluorescence emission as well as lifetime are found to be quenched in presence of zinc tetraphenylporphyrin. The fluorescence quenching is ascribed to be due to the combined effect of electron transfer from zinc tetraphenylporphyrin to 9-cyanoanthracene and energy transfer (radiative as well as non-radiative) from 9-cyanoanthracene to zinc tetraphenylporphyrin. The highly exergonic values of Gibbs free energy change for both forward electron transfer reaction (−1.15 eV) and charge recombination reaction (−1.94 eV) indicate the possibilities of occurrences of these two processes in the Marcus inverted region. The fluorescence quenching rate due to photoinduced electron transfer reaction is found to be close to the diffusion-controlled limit within the present donor-acceptor system upon excitation of the acceptor molecules. 相似文献
87.
88.
89.
U. S. Rai K. D. Mandal N. P. Singh 《Journal of Thermal Analysis and Calorimetry》1989,35(5):1687-1697
The phase diagrams of the binary systems of picric acid with naphthalene, anthracene and phenanthrene, and of -naphthol withp-toluidine, determined by the thaw-melt method, show the formation of a molecular complex and two eutectics in each system. The heats of the pure components, eutectics and molecular complexes were determined by differential scanning calorimetry. Comparison of the experimental heats of fusion with the theoretical values calculated via the mixture law suggests cluster formation in the melts. The entropy of fusion, enthalpy of mixing and excess thermodynamic functions were also calculated from the heat of fusion data.
Thanks are due to Prof. I. S. Ahuja, Head, Chemistry Department, Banaras Hindu University, for providing research facilities. Thanks are also due to CSIR, New Delhi, for financial assistance. 相似文献
Zusammenfassung Die Phasendiagramme der binären Systeme von Pikrinsäure mit Naphthalin, Anthrazen und Phenanthren sowie von -Naphthol mit p-Aminotoluol wurden bestimmt. In jedem System zeigt sich die Bildung eines Molekülkomplexes sowie je zwei Eutektika. Mittels DSC wurden die Schmelzwärmen der reinen Komponenten, der eutektischen Mischungen und der Molekülkomplexe ermitteis. Der Vergleich der experimentell ermittelten Schmelzwärmen mit den mittels der Mischungsregel errechneten Werten läßt auf eine Clusterbildung in der Schmelze schließen. Weiterhin wurden aus den Schmelzwärmen auch Werte für Schmelzentropie und Mischungsenthalpie errechnet.
— , , - . , . , . , .
Thanks are due to Prof. I. S. Ahuja, Head, Chemistry Department, Banaras Hindu University, for providing research facilities. Thanks are also due to CSIR, New Delhi, for financial assistance. 相似文献
90.
Using the Bohm-Pines hamiltonian we present a method for calculating the effective interaction between two plasmons by solving the equation of motion of a double-time retarded commutator defined to represent the propagation of two plasmons. This is achieved by using a decoupling procedure for the higher-order plasmon Green functions which is based on the conservation of frequency moments. The effective interaction between two plasmons is found to be repulsive, in contrast with the results obtained earlier. 相似文献