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Puruliya, India

Guha A.,University of Calcutta | Sanyal R.,University of Calcutta | Chattopadhyay T.,Panchakot Mahavidyalya | Han Y.,Japan National Institute of Advanced Industrial Science and Technology | And 2 more authors.
Journal of Molecular Structure | Year: 2013

Four specially designed Schiff bases 2-formyl-4-R-6-(3N-4- hydroxybenzoicacid)-iminomethyl-phenolato (where R = methyl/tert-butyl/chloro for L1, L2, L3 respectively) and 2-(3N-4-hydroxybenzoicacid)-iminomethyl- phenolato (L4) having ability to form hydrogen bonding and their zinc complexes (1-4) have been synthesized and characterized. These complexes gave various types of nano-sized materials via self-assembly in solid state. FE-SEM was employed to investigate their morphology. Using a variety of analytical techniques such as elemental analysis, infrared spectroscopy (FT-IR), ESI-MS and 1H NMR spectroscopy, a consistent picture of structures of these complexes are obtained. All the Schiff-bases and their zinc complexes exhibit photoluminescence property. Density functional theory calculation has been performed to rationalize the origin of the spectral bands of the ligands as well as the complexes. © 2013 Elsevier B.V. All rights reserved. Source

Maiti P.,University of Calcutta | Khan A.,University of Calcutta | Chattopadhyay T.,Panchakot Mahavidyalya | Das S.,University of Calcutta | And 5 more authors.
Journal of Coordination Chemistry | Year: 2011

Four water-soluble dinuclear Zn(II) complexes (1-4) of compartmental ligand L=2,6-bis(R-iminomethyl)-4-R′-phenolate (where R=N-ethylpiperidine or R=N-ethylpyrrolidine, R′=methyl or tert-butyl) have been synthesized, characterized, and their DNA cleavage activity and cytotoxicity toward HepG2 cancerous cells are evaluated. The dinuclear complexes are formed by a pentadentate-substituted phenolate ligand chelating the metal ions separated by ca 3.27 Å . Each metal is a distorted trigonal bipyramid, completing the coordination sphere through acetate. The X-ray structural determination of 2 shows that the complex is counterbalanced by half Zn(SCN) 4 2- (formulation [Zn 2L 2(CH 3CO 2) 2][(Zn(SCN) 4] 0.5), while in 1 and 3 two crystallographically-independent complexes are present in the unit cell with a Zn(SCN) 4 2-. Among the four complexes only the 4-tert-butyl-phenolato derivatives (3 and 4) show DNA cleavage activity in in-vivo conditions and appear to be promising toward metal complexes to be used as anticancer agents. The cytotoxicity of the complexes, investigated through MTT assay, suggests that 4 is a better choice as artificial nuclease. © 2011 Taylor & Francis. Source

Banerjee A.,University of Calcutta | Guha A.,University of Calcutta | Maiti A.,University of Calcutta | Goswami S.,University of Calcutta | And 5 more authors.
Transition Metal Chemistry | Year: 2011

Three Ni(II) complexes of cresol-based Schiffbase ligands, namely [Ni 2(L 1)(NCS) 3(H 2O) 2], (1) [Ni 2(L 2)- (CH 3COO)(NCS) 2(H 2O)] (2) and [Ni 2(L 3)(NCS) 3] (3), (where L 1 = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L 2 = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L 3 = 2,6-bis{N-ethyl-N-(3-hydroxypropyl iminomethyl)}-4- methylphenolato), have been synthesized and structurally characterized by X-ray single-crystal diffraction in addition to routine physicochemical techniques. Density functional theory calculations have been performed to understand the nature of the electronic spectra of the complexes. Complexes 1-3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile-water medium promote the cleavage of the O-P bond to form p-nitrophenol and smoothly convert 3,5-ditert- butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) either in MeOH or in MeCN medium. Phosphatase- and catecholase-like activities were monitored by UV-vis spectrophotometry and the Michaelis-Menten equation was applied to rationalize all the kinetic parameters. Upon treatment with urea, complexes 1 and 2 give rise to [Ni 2(L 1)(NCS) 2(NCO)(H 2O) 2] (1') and [Ni 2(L 2)- (CH 3COO)(NCO)(NCS)(H 2O)] (2') derivatives, respectively, whereas 3 remains unaltered under same reaction conditions. © Springer Science+Business Media B.V. 2011. Source

Ghosh T.,University of Calcutta | Chattopadhyay T.,Panchakot Mahavidyalya | Das S.,University of Calcutta | Mondal S.,University of Calcutta | And 3 more authors.
Crystal Growth and Design | Year: 2011

Two pseudohalides thiocyanate and dicyanamide have been employed to synthesize complexes of MnII, CoII, NiII, CuII, and ZnII in the presence of a hemilabile ligand 2-benzoylpyridine (Phpyk). With thiocyanate all the aforesaid metal ions (except for CoII, of which suitable single crystals for X-ray analysis were not obtained) produce mononuclear complexes having general composition of [MII(NCS)2(Phpyk)2]. The structure determination reveals that Mn and Zn complexes (1, 4) are isomorphous and isostructural (crystallizing in space group C2/c), while Ni and Cu complexes (2, 3) crystallize in space groups P1̄ and P21/n, respectively. Interestingly, no complex has been obtained with a configuration having the N of one Phpyk trans to the O of the other chelating ligand and among the four complexes only in complex 3 the two thiocyanato ligands are in trans-configuration. On the other hand, complexes 5-8 are isomorphous and crystallize in orthorhombic chiral space group P21212 1. The bridging mode of dicyanamide anions helps to generate a three-dimensional covalently bonded polymeric network of 66 topology for all the polynuclear complexes. By using 8 as sole precursor, we have pyrolytically synthesized triangular shaped ZnO nanoparticles. © 2011 American Chemical Society. Source

Guha A.,University of Calcutta | Banu K.S.,University of Calcutta | Das S.,University of Calcutta | Chattopadhyay T.,Panchakot Mahavidyalya | And 3 more authors.
Polyhedron | Year: 2013

Four new mononuclear nickel(II) complexes, namely [NiL1(H 2O)3](NO3)2 (1), [NiL 2(H2O)3](NO3)2 (2), [NiL3(H2O)3](NO3)2 (3) and [NiL4(ClBz)(H2O)]·1.25(H2O) (4) have been synthesized via Schiff-base formation by condensation between 2-benzoylpyridine and N-(2-aminoethyl)pyrrolidine for L1, salicylaldehyde and N-(2-aminoethyl)piperazine (L2), 5-chlorosalicylaldehyde and N-(2-aminoethyl)piperazine (L3), and 5-chlorosalicylaldehyde and N-(2-aminoethyl)morpholine (L4). These complexes are comprehensively characterized via routine physicochemical techniques as well as by single crystal X-ray structural analyses. Despite all the nickel complexes are mononuclear, the catecholase activity shows prominent variation depending on the coordination environment around the metal center. Complexes 2 and 3 derived from same amine bear an extra positive charge on the ligand system facilitating the substrate-catalyst interaction to promote the oxidation of 3,5-DTBC to 3,5-DTBQ. On the contrary complexes 1 and 4 remain inert in nature, although 1 shows structural similarities in terms of coordination environment with nickel substituted catechol oxidase. Source

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