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Biswas C.,University of Calcutta | Biswas C.,Sarojini Naidu College for Women | Drew M.G.B.,University of Reading | Figuerola A.,Italian Institute of Technology | And 4 more authors.
Inorganica Chimica Acta | Year: 2010

Three new trinuclear copper(II) complexes, [(CuL1)3(μ3-OH)](ClO4) 2·3.75H2O (1), [(CuL2)3(μ3-OH)](ClO4) [(CuL3)3(μ3-OH)](BF4) 2·0.5CH3CN (3) have been synthesized from three tridentate Schiff bases HL1, HL2, and HL3 (HL1 = 2-[(2-amino-ethylimino)-methyl]-phenol, HL2 = 2-[(2-methylamino-ethylimino)-methyl]-phenol and HL3 = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol). The complexes are characterized by single-crystal X-ray diffraction analyses, IR, UV-vis and EPR spectroscopy, and variable-temperature magnetic measurements. All the compounds contain a partial cubane [Cu3O4] core consisting of the trinuclear unit [(CuL)3(μ3-OH)]2+ together with perchlorate or fluoroborate anions. In each of the complexes, the three copper atoms are five-coordinated with a distorted square-pyramidal geometry except in complex 1, in which one of the CuII ions of the trinuclear unit is six-coordinate being in addition weakly coordinated to one of the perchlorate anions. Variable-temperature magnetic measurements and EPR spectra indicate an antiferromagnetic exchange coupling between the CuII ions of complexes 1 and 2, while this turned out to be ferromagnetic for complex 3. Experimental values have been fitted according to an isotropic exchange Hamiltonian. Calculations based on Density Functional Theory have also been performed in order to estimate the exchange coupling constants in these three complexes. Both sets of values indicate similar trends and specially calculated J values establish a magneto-structural correlation between them and the Cu-O-Cu bond angle, in that the coupling is more ferromagnetic for smaller bond angle values. © 2010 Elsevier B.V. All rights reserved. Source

Banerjee S.,CSIR - Central Electrochemical Research Institute | Saraswat G.,CSIR - Central Electrochemical Research Institute | Bandyopadhyay S.A.,CSIR - Central Electrochemical Research Institute | Bandyopadhyay S.A.,Sarojini Naidu College for Women | Kabir S.N.,CSIR - Central Electrochemical Research Institute
PLoS ONE | Year: 2014

The ovary receives a finite pool of follicles during fetal life. Atresia remains the major form of follicular expenditure at all stages since development of ovary. The follicular reserve, however, declines at an exponential rate leading to accelerated rate of decay during the years preceding menopause. We examined if diminished follicle reserve that characterizes ovarian aging impacts the attrition rate. Premature ovarian aging was induced in rats by intra-embryonic injection of galactosyltransferase-antibody on embryonic day 10. On post-natal day 35 of the female litters, either a wedge of fat (sham control) or a wild type ovary collected from 25-day old control rats, was transplanted under the ovarian bursa in both sides. Follicular growth and atresia, and ovarian microenvironment were evaluated in the follicle-deficient host ovary and transplanted ovary by real time RT-PCR analysis of growth differentiation factor-9, bone morphogenetic protein 15, and kit ligand, biochemical evaluation of ovarian lipid peroxidation, superoxide dismutase (SOD) and catalase activity, and western blot analysis of ovarian pro- and anti-apoptotic factors including p53, bax, bcl2, and caspase 3. Results demonstrated that the rate of follicular atresia, which was highly preponderant in the follicle-deficient ovary of the sham-operated group, was significantly prevented in the presence of the transplanted ovary. As against the follicle-deficient ovary of the sham-operated group, the follicle-deficient host ovary as well as the transplanted ovary in the ovary-transplanted group exhibited stimulated follicle growth with increased expression of anti-apoptotic factors and down regulation of pro-apoptotic factors. Both the host and transplanted ovaries also had significantly lower rate of lipid peroxidation with increased SOD and catalase activity. We conclude that the declining follicular reserve is perhaps the immediate thrust that increases the rate of follicle depletion during the final phase of ovarian life when the follicle reserve wanes below certain threshold size. © 2014 Banerjee et al. Source

Biswas C.,University of Calcutta | Biswas C.,Sarojini Naidu College for Women | Drew M.G.B.,University of Reading | Ruiz E.,University of Barcelona | And 3 more authors.
Dalton Transactions | Year: 2010

Three novel mixed bridged trinuclear and one tetranuclear copper(ii) complexes of tridentate NNO donor Schiff base ligands [Cu3(L 1)2(μ1,1-N3)2(CH 3OH)2(BF4)2] (1), [Cu 3(L1)2(μ1,1-N3) 2(μ-NO3-1κO:2κO′)2] (2), [Cu3(L2)2(μ1,1-N 3)2(μ-NO3-1κO:2κO′) 2] (3) and [Cu4(L3)2(μ 1,1-N3)4(μ-CH3COO-1κO: 2κO′)2] (4) have been synthesized by reaction of the respective tridentate ligands (L1 = 2-[1-(2-dimethylamino-ethylimino) -ethyl]-phenol, L2 = 2-[1-(2-diethylamino-ethylimino)-ethyl]-phenol, L3 = 2-[1-(2-dimethylamino-ethylimino)-methyl]-phenol) with the corresponding copper(ii) salts in the presence of NaN3. The complexes are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. Complex 1 is composed of two terminal [Cu(L1)(μ1,1-N3)] units connected by a central [Cu(BF4)2] unit through nitrogen atoms of end-on azido ligands and a phenoxo oxygen atom of the tridentate ligand. The structures of 2 and 3 are very similar; the only difference is that the central unit is [Cu(NO3)2] and the nitrate group forms an additional μ-NO3-1κO:2κO′ bridge between the terminal and central copper atoms. In complex 4, the central unit is a di-μ1,1-N3 bridged dicopper entity, [Cu 2(μ1,1-N3)2(CH 3COO)2] that connects two terminal [Cu(L 3)(μ1,1-N3)] units through end-on azido, phenoxo oxygen and μ-CH3COO-1κO:2κO′ triple bridges to result in a tetranuclear unit. Analyses of variable-temperature magnetic susceptibility data indicates that there is a global weak antiferromagnetic interaction between the copper(ii) ions in complexes 1-3, with the exchange parameter J of -9.86, -11.6 and -19.98 cm-1 for 1-3, respectively. In complex 4 theoretical calculations show the presence of an antiferromagnetic coupling in the triple bridging ligands (acetato, phenoxo and azido) while the interaction through the double end-on azido bridging ligand is strongly ferromagnetic. © 2010 The Royal Society of Chemistry. Source

Biswas C.,University of Calcutta | Biswas C.,Sarojini Naidu College for Women | Drew M.G.B.,University of Reading | Asthana S.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | And 2 more authors.
Journal of Molecular Structure | Year: 2010

Two new mono-aqua-bridged dinuclear Cu(II) complexes of tridentate NNO Schiff bases, [Cu2(μ-H2O)L1 2 (H2O)2](BF4)2·2H2O (1) and [Cu2(μ-H2O)L2 2 (H2O)2](BF4)2·2H2O (2) where HL1 = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol and HL2 = 2-[(2-dimethylamino-ethylimino)-methyl]-phenol were synthesized. Both the complexes were characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. For both the complexes each Cu(II) ion is in a square-pyramidal environment being bonded to three atoms from the tridentate NNO Schiff base and a terminal H2O molecule in the equatorial plane; a second H2O ligand acts as a bridge between the two Cu(II) centres through the axial positions. Hydrogen bonds between the terminal H2O ligand and the Schiff base of the adjacent centre complete the intra-dimer linkages. Variable-temperature (4-300 K) magnetic susceptibility measurement shows the presence of significant antiferromagnetic coupling for both the complexes (J = -12.2 and -12.5 cm-1, respectively, for 1 and 2), mediated mainly through the intra-dimer H-bonds. © 2009 Elsevier B.V. All rights reserved. Source

Das A.,Acharya Prafulla Chandra College | Bhadra S.,Acharya Prafulla Chandra College | Saha S.,Sarojini Naidu College for Women
Quantum Information Processing | Year: 2015

Quantum phase transition in dimerised antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical (or critical like) points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs too in the same dimer chain. Though closed dimerised isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied. © 2015, Springer Science+Business Media New York. Source

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