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221.
Chakraborty A Seth D Chakrabarty D Sarkar N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(3):801-808
The photoinduced electron-transfer reaction between Coumarin dyes and N,N-dimethylaniline has been investigated using steady-state and Time-resolved fluorescence spectroscopy in the surface of beta-cyclodextrin in dimethyl formamide (DMF) solvent. The electron-transfer rate constant has been correlated with the free-energy change during the process. We have observed a diffusion-controlled ET process in pure DMF by showing a normal Marcus region. However, the picture is different in presence of cyclodextrin. Here the ET is retarded at higher free-energy region. This unusual feature in bimolecular electron-transfer reaction is assumed to be arising from the different binding possibility of the Coumarin molecules to the cyclodextrin moity. 相似文献
222.
Sandip Saha Debabrata Biswas Partha Pratim Chakrabarty Atish Dipankar Jana Athanassios K. Boudalis Saikat Kumar Seth Tanusree Kar 《Polyhedron》2010
The reaction of ethylene diamine with Cu(NO3)2·3H2O and an excess of NaN3 (1:2:4 molar ratio) lead to the formation of copper-azido based polymer [Cu4(N3)8(en)2]n (1), which has been successfully characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction and variable temperature magnetic study. X-ray crystal structure determination of 1 reveals that the structure consists of 1D chains of a centrosymmetric tetranuclear copper(II)-azido cluster, connected through double azido end-to-end bridges. Variable-temperature magnetic studies (between 2 and 300 K) suggest dominant antiferromagnetic interactions in this complex, although ferromagnetic interactions have been observed in all other copper-azido based polymers produced with ethylene diamine reported so far. 相似文献
223.
The undirected power graph G(S) of a semigroup S is an undirected graph whose vertex set is S and two vertices a,b∈S are adjacent if and only if a≠b and a
m
=b or b
m
=a for some positive integer m. In this paper we characterize the class of semigroups S for which G(S) is connected or complete. As a consequence we prove that G(G) is connected for any finite group G and G(G) is complete if and only if G is a cyclic group of order 1 or p
m
. Particular attention is given to the multiplicative semigroup ℤ
n
and its subgroup U
n
, where G(U
n
) is a major component of G(ℤ
n
). It is proved that G(U
n
) is complete if and only if n=1,2,4,p or 2p, where p is a Fermat prime. In general, we compute the number of edges of G(G) for a finite group G and apply this result to determine the values of n for which G(U
n
) is planar. Finally we show that for any cyclic group of order greater than or equal to 3, G(G) is Hamiltonian and list some values of n for which G(U
n
) has no Hamiltonian cycle. 相似文献
224.