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Banerjee S.,Jadavpur University | Nandy M.,Jadavpur University | Sen S.,Jadavpur University | Sen S.,Rishi Bankim Chandra College | And 6 more authors.
Dalton Transactions | Year: 2011

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new CoII/CoIII and NiII complexes with a pentadentate Schiff base ligand H3L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1:2 molar ratio. The room temperature syntheses involving CoII and NiII nitrates and the ligand H3L lead to the isolation of the dinuclear species [Co2L2(H2O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [CoII 2Co III 2L2(μ3-OMe) 2(NO3)(H2O)2]NO3· 2(H2O) (2), and [Ni4L2(μ3-OMe) 2(H2O)2]·2H2O (4). 1 is found to be a simple mono alkoxo-bridged CoIII dinuclear species, whereas 2 and 4 are both rhomb-like tetrameric complexes with double oxo bridges and μ3-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2 shows six coordinate ordered CoII and CoIII ions and 4 has both six- and five-coordinate Ni II centers. Compound 3 is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, 1H-NMR and ESI mass study results and is supposed to have one NiII center coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2 and 4 is performed which indicate for both 2 and 4 the presence of intracluster dominant ferromagnetic interactions. © 2011 The Royal Society of Chemistry.

Basak S.,Jadavpur University | Sen S.,Jadavpur University | Sen S.,Rishi Bankim Chandra College | Roy P.,Jadavpur University | And 6 more authors.
Australian Journal of Chemistry | Year: 2010

Two new dinuclear bis(μ2-phenoxo)-bridged copper(ii) complexes [Cu(NCS)L1]2 (1) and [Cu(NCS)L2] 2 (2) have been synthesized using two tridentate NNO-donor Schiff-base ligands, L1H (Me2N(CH2) 3N=CHC6H3(OMe)(OH)) and L2H (Me 2N(CH2)3N=C(CH3)C6H 4(OH)), respectively. They have been characterized by elemental analyses, IR, UV-visible, and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-Ray single-crystal structures reveal a central Cu2O2 core in each complex with an isothiocyanate ligand coordinated terminally to each metal centre. The coordination environments around the CuII ions in 1 and 2 are a distorted trigonal bipyramid and a quasi-regular square pyramid, respectively, with significant differences in the Cu-O-Cu bridging angles (100.22(5)° for 1 and 95.64(7)° for 2). Although both Cu II dimers present intradimer antiferromagnetic exchange interactions, the magnitudes of the coupling constants in 1 and 2 (J = -119(1) and 0.361(3) cm-1, respectively) are quite different as a result of the different coordination geometries and Cu-O-Cu bridging angles. Both complexes act as promising catalysts or catalyst precursors for the efficient peroxidative oxidation of cycloalkanes (cyclohexane and cycloheptane) to the corresponding cyclic alcohols and ketones, with maximum overall yields of 53% and 56% for 1 and 2, respectively. © 2010 CSIRO.

Saha N.C.,Kalyani University | Biswas C.,Kalyani University | Biswas C.,Rishi Bankim Chandra College | Ghorai A.,Kalyani University | And 3 more authors.
Polyhedron | Year: 2012

New iron(III) complexes of 5-methyl-3-formylpyrazole-N(4)- dimethylthiosemicarbazone (HMP ZNMe 2) (I) and 5-methyl-3-formylpyrazole-N(4)-diethylthiosemicarbazone (HMP ZNEt 2) (III), [Fe(MP ZNMe 2) 2]NO 3·H 2O (II) and [Fe(MP ZNEt 2) 2]NO 3·H 2O (IV), respectively, have been synthesised for the first time and physico-chemically characterised by magnetic measurements (polycrystalline state), electronic and IR spectra. Both are cationic complexes containing two monodeprotonated tridentate ligands with NNS donor sites and an anionic counterpart; the complex species behave as 1:1 electrolytes in MeOH. IR spectra (4000-200 cm -1) indicate coordination to iron(III) centre via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulfur atom. X-ray crystallographic data of (II) (monoclinic, C2/c) and (IV) (P1̄, triclinic) have authenticated the FeN 4S 2 octahedral coordination in both complex ions, as envisaged from the spectral data. In both species, the two azomethine nitrogen atoms are trans to each other, while the pyrazolyl ring nitrogen and the thiolato sulfurs atoms are in cis positions. We further observed that both the ligands and their corresponding complexes were capable of killing HeLa cells in culture, but the cytotoxicity of the complexes was found to be greater than their corresponding ligands. Complex (II) does not have any role in cell-cycle progression, but complex (IV) arrests the M-phase to prevent cell-cycle progression. © 2011 Elsevier Ltd. All rights reserved.

Dutta B.G.,Rishi Bankim Chandra College | Dutta B.G.,Indian Center for Space Physics | Chakrabarti S.K.,Indian Center for Space Physics | Chakrabarti S.K.,se National Center For Basic Science
Astrophysical Journal | Year: 2016

In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν c) of ∼3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model. © 2016. The American Astronomical Society. All rights reserved.

Chakraborty T.K.,Rishi Bankim Chandra College | Chakraborty T.K.,P.A. College | Chaudhuri S.D.,P.A. College | Choudhury J.,P.A. College
Hacquetia | Year: 2012

The evolutionary history of Ophioglossaceae is enigmatic mainly because fossils of the family trace back only from the earliest Tertiary. Phylogenetic analyses indicate that Helminthostachys is sister to the broadly defined Botrychium. Generally the sporophore of Botrychium is a pinnately compound, whereas it is simple in Helminthostachys. Here examples of different Helminthoistachys are represented which show double or triple spikes with some variations. Plants showing variations in their spike morphology are also grown normally. Variations of Helminthostachys spike morphology indicate a tendency to form a compound sporophore structure and in that way have a strong relationship with Botrychium.

Biswas S.,Rishi Bankim Chandra College | Roy P.,Saha Institute of Nuclear Physics | Dutt-Mazumder A.K.,Saha Institute of Nuclear Physics
Indian Journal of Physics | Year: 2011

We construct the charge symmetry violating (CSV) nucleon-nucleon potential in nuclear matter induced by the p-ω mixing due to the neutron-proton mass difference driven by the NN loop. Analytical expression for for the two-body CSV potential is presented. © 2011 Indian Association for the Cultivation of Science.

Adhya S.P.,Saha Institute of Nuclear Physics | Mandal M.,Saha Institute of Nuclear Physics | Biswas S.,Rishi Bankim Chandra College | Roy P.K.,Saha Institute of Nuclear Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

In this work, dispersion relations of π0 and π± have been studied in vacuum in the limit of a weak external magnetic field using a phenomenological pion-nucleon (πN) Lagrangian. For our purpose, we have calculated the results up to one loop order in self-energy diagrams with the pseudoscalar (PS) and pseudovector (PV) pion-nucleon interactions. By assuming a weak external magnetic field, it is seen that the effective mass of the pion gets explicit magnetic field dependence, and it is modified significantly for the case of PS coupling. However, for the PV coupling, only a modest increase in the effective mass is observed. These modified dispersion relations due to the presence of the external field can have substantial influence in the phenomenological aspect of the mesons, both in the context of neutron stars as well as in relativistic heavy ion collisions. © 2016 American Physical Society.

Biswas S.,Rishi Bankim Chandra College | Roy P.,Saha Institute of Nuclear Physics
Proceedings of the Indian National Science Academy | Year: 2015

We revisit the problem of charge symmetry violation (CSV) in nucleon-nucleon interactions due to π- η mixing driven by the neutron-proton mass difference. We construct the CSV potential and estimate the contribution to the difference between pp and nn scattering lengths. © Printed in India.

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