University of North Bengal is a state university, situated at Raja Rammohanpur near Siliguri in Darjeeling district in the Indian state of West Bengal. While the second campus of the university is situated at Danguajhar, Jalpaiguri in Jalpaiguri district in the Indian state of West Bengal. The university was established in 1962 with a goal to disseminate knowledge to fulfill growing socio-economic and technical manpower needs in the six North Bengal districts and the neighbouring state of Sikkim. Currently, colleges from Alipurduar, Cooch Behar, Jalpaiguri and Darjeeling districts are affiliated to this university. North Bengal University offers degrees in undergraduate, post graduate, M. Phil and doctorate programs. Wikipedia.
Mandal B.,Surya Sen College |
Basu B.,North Bengal University
RSC Advances | Year: 2014
Organic compounds possessing S-S bonds, often called disulfides or more specifically disulfanes, have been widely applied in various fields ranging from biochemistry to different industrially important polymers, used as synthetic intermediates in other fine chemicals such as catenanes, rotaxanes, micelles, and also in areas like peptidomimetics, self-assembled monolayers (SAMs) etc. Such versatile applications have steered the development of several new methods for the preparation of organic disulfides. The present review has attempted to comprehensively summarize recent advances in the process of S-S bond formation, highlighting plausible mechanistic considerations, scope and limitations. © 2014 The Royal Society of Chemistry.
Conductance, a contrivance to explore ion association and solvation behavior of an ionic liquid (tetrabutylphosphonium tetrafluoroborate) in acetonitrile, tetrahydrofuran, 1,3-dioxolane, and their binaries
Ekka D.,North Bengal University |
Roy M.N.,North Bengal University
Journal of Physical Chemistry B | Year: 2012
Precise measurements on electrical conductance (λ) of solutions of an ionic liquid (IL) tetrabutylphosphonium tetrafluoroborate in acetonitrile (ACN), tetrahydrofuran (THF), and 1,3-dioxolane (1,3-DO) and their binary mixtures have been reported at 298.15 K. The conductance data have been analyzed by the Fuoss conductance equation (1978) in terms of the limiting molar conductance (λo), the association constant (KA), and the association diameter (R) for ion-pair formation. The Walden product is obtained and discussed. However, the deviation of the conductometric curves (λ versus √c) from linearity for the electrolyte in THF and 1,3-DO and their binary mixtures indicated triple-ion formation and therefore the corresponding conductance data have been analyzed by the Fuoss-Kraus theory of triple ions. The limiting ionic conductances (λo ±) have been estimated from the appropriate division of the limiting molar conductivity value of tetrabutylammonium tetraphenylborate [Bu4NBPh4] as the "reference electrolyte" method along with a numerical evaluation of ion-pair and triple-ion formation constants (KP ≈ KA and KT). The results have been discussed in terms of solvent properties and configurational theory. Ionic association in the limiting molar conductances as well as the single-ion conductivity values have been determined for the electrolyte in the solvent media. © 2012 American Chemical Society.
Paul S.,North Bengal University |
Misra A.,North Bengal University
Inorganic Chemistry | Year: 2011
All-metal aromatic molecules are the latest inclusion in the family of aromatic systems. Two different classes of all-metal aromatic clusters are primarily identified: one is aromatic only in the low spin state, and the other shows aromaticity even in high-spin situations. This observation prompts us to investigate the effect of spin multiplicity on aromaticity, taking Al 4 2-, Te 2As 2 2-, and their copper complexes as reference systems. Among these clusters, it has been found that the molecules that are aromatic only in their singlet state manifest antiaromaticity in their triplet state. The aromaticity in the singlet state is characterized by the diatropic ring current circulated through the bonds, which are cleaved to generate excess spin density on the atoms in the antiaromatic triplet state. Hence, in such systems, an antagonistic relationship between aromaticity and high-spin situations emerges. On the other hand, in the case of triplet aromatic molecules, the magnetic orbitals and the orbitals maintaining aromaticity are different; hence, aromaticity is not depleted in the high-spin state. The nonlinear optical (NLO) behavior of the same set of clusters in different spin states has also been addressed. We correlate the second hyperpolarizability and spin density in order to judge the effect of spin multiplicity on thirdórder NLO response. This correlation reveals a high degree of NLO behavior in systems with excess spin density. The variance of aromaticity and NLO response with spin multiplicity is found to stem from a single aspect, the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and eventually the interplay among aromaticity, magnetism, and NLO response in such materials is established. Hence, the HOMO-LUMO energy gap becomes the cornerstone for tuning the interplay. This correlation among the said properties is not system-specific and thus can be envisaged even beyond the periphery of all-metal aromatic clusters. Such interplay is of crucial importance in tailoring novel paradigm of multifunctional materials. © 2011 American Chemical Society. © 2011 American Chemical Society. © 2011 American Chemical Society.
Paul B.C.,North Bengal University |
Ghose S.,North Bengal University
General Relativity and Gravitation | Year: 2010
We obtain cosmological solutions which admit emergent universe (EU) scenario in the framework of Einstein Gauss-Bonnet (GB) gravity coupled with a dilaton field in 4-dimensions. The coupling parameter of the GB terms and the dilaton in the theory are determined for obtaining an EU scenario. The corresponding dilaton potential which admits such scenario is determined. It is found that the GB terms coupled with a dilaton field plays an important role in describing the dynamics of the evolution of the early as well as the late universe. We note an interesting case where the GB term dominates initially in the asymptotic past regime, subsequently it decreases and thereafter its contribution in determining the dynamics of the evolution dominates once again. We note that the Einstein's static universe solution permitted here is unstable which the asymptotic EU might follow. We also compare our EU model with supernova data. © Springer Science+Business Media, LLC 2009.
Nandi K.K.,North Bengal University |
Bhadra A.,North Bengal University
Physical Review Letters | Year: 2012
A Comment on the Letter by P.D. Mannheim and J.G. O'Brien, Phys. Rev. Lett.PRLTAO0031-9007 106, 121101 (2011). © 2012 American Physical Society.