Tanmay Chattopadhyay

Indian Institute of Engineering Science and Technology, Shibpur, Hawrah, West Bengal, India

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Publications (35)99.02 Total impact

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    ABSTRACT: Three varieties of nickel oxide nanoparticles [NiO(I), NiO(Br) and NiO(Cl)] have been prepared from three simple mononuclear nickel(II) Schiff-base complexes using pyrolytic technique. The synthesized nanoparticles are characterized by FT-IR, UV-Vis, PXRD, DLS, SEM, TEM and EDX method. All the techniques suggest the production of highly pure nickel oxides. The magnetic measurement reveals a small hysteresis loop at room temperature, confirming a super-paramagnetic (weak ferromagnetic) nature of the synthesized NiO nanoparticles. We have applied these nanoparticles for drug delivery. For this purpose, Erythromycin, the well known broad spectrum antibiotic is conjugated with the NiO nanoparticles to develop NiO(I)-Ery, NiO(Br)-Ery and NiO(Cl)-Ery. These conjugated nanoparticles successfully deliver Erythromycin towards both gram positive and gram negative bacteria and show effective antimicrobial activity against Erythromycin resistant Staphylococcus aureus and Escherichia coli as model microbial species, evidenced from the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values. The order of efficiency toward drug delivery is NiO(I)-Ery> NiO(Br)-Ery> NiO(Cl)-Ery. Thus those conjugates can be applied to overcome the drug resistant property of bacteria which will be a beneficial strategy in anti-bacterial therapy.
    RSC Advances 04/2015; 10.1039/C5RA00642B(45). DOI:10.1039/C5RA00642B · 3.84 Impact Factor
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    ABSTRACT: Two new mononuclear Ni(II) complexes, namely [Ni(HL)(SCN)2(H2O)] (1) and [Ni(HL)(SCN)2(4,4′-bipy)] (2) [HL = 2-[(2-piperazin-1-yl-ethylimono)-methyl]phenol] have been synthesized and structurally characterized. The uncoordinated nitrogen atom of the piperazine moiety is protonated to provide electrical neutrality to the system. The configuration of the isothiocyanato ligands is different in the two complexes, cis located in 1 and trans in complex 2. The change of configuration of the isothiocyanato groups on addition of the neutral spacer 4,4-bipyridine to complex 1 has been monitored by conductometric and FTIR spectral studies and the most probable mechanistic pathway has been proposed. DFT calculations have been performed and the outcome corroborates well with the experimental facts. The anticancer activity of the two Ni(II) complexes has been evaluated in human cervical (HeLa) cancer and breast cancer (MCF-7) cell lines. The cytotoxic effects of these complexes were determined by an MTT assay. The fluorescent intensity obtained in HeLa cells reveals the generation of ROS by the complexes using DCFH-DA (2,7-dichlorofluorescein diacetate) dye. The apoptotic cell death was determined by fluorescent staining with acridine orange and ethidium bromide, which confirmed the presence of apoptotic cells. Further, flow cytometry analysis was done, suggesting an arrest of the cell cycle in the S phase of the HeLa cells. Although a detailed molecular mechanism for the anticancer activity of the two complexes was not ascertained, the experimental results suggest that both complexes are effective anticancer agents, with complex 2 seeming to be more promising. The result also indicates that the apoptotic cell death in the cancer cell might be triggered by the process of ROS generation with the complexes. Thermo gravimetric analysis of two complexes hints that NiO particles are the final product after decomposition of the complexes at 600 °C.
    Polyhedron 04/2015; 93. DOI:10.1016/j.poly.2015.03.030 · 2.05 Impact Factor
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    ABSTRACT: An "end-off" compartmental ligand has been synthesized by an abnormal Mannich reaction, namely, 2-[bis(2-methoxyethyl)aminomethyl]-4-isopropylphenol yielding three centrosymmetric binuclear μ-phenoxozinc(II) complexes having the molecular formula [Zn2(L)2X2] (Zn-1, Zn-2, and Zn-3), where X = Cl(-), Br (-), and I (-), respectively. X-ray crystallographic analysis shows that the ZnO3NX chromophores in each molecule form a slightly distorted trigonal-bipyramidal geometry (τ = 0.55-0.68) with an intermetallic distance of 3.068, 3.101, and 3.083 Å (1-3, respectively). The spectrophotometrical investigation on their phosphatase activity established that all three of them possess significant hydrolytic efficiency. Michaelis-Menten-derived kinetic parameters indicate that the competitiveness of the rate of P-O bond fission employing the phosphomonoester (4-nitrophenyl)phosphate in 97.5% N,N-dimethylformamide is 3 > 1 > 2 and the kcat value lies in the range 9.47-11.62 s(-1) at 298 K. Theoretical calculations involving three major active catalyst forms, such as the dimer-cis form (D-Cis), the dimer-trans form (D-Trans), and the monoform (M-1 and M-2), systematically interpret the reaction mechanism wherein the dimer-cis form with the binuclear-bridged hydroxide ion acting as the nucleophile and one water molecule playing a role in stabilizing the leaving group competes as the most favored pathway.
    Inorganic Chemistry 02/2015; DOI:10.1021/ic502937a · 4.79 Impact Factor
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    ABSTRACT: Four new zinc(II) complexes of a tridentate Schiff base ligand 2-((E)-((pyridin-2-yl)methylimino)methyl)phenol (HL), namely [Zn2L2Cl2] (1); [Zn2L2Br2] (2); [ZnL(SCN)(MeOH)] (3) and [Zn2L(OAc)(3) (MeOH)] (4) have been synthesized with the view to investigate the role of co-ligands in controlling the structural diversity, photoluminescence property and catalytic activities. The complexes have been characterized through common physicochemical techniques as well as by X-ray single crystal structural analysis. All of them display interesting co-ligands mediated photoluminescence property the origin of which may be attributed due to ligand to metal charge transfer (LMCT) and the order of photoluminescence efficiency is 3 > 4 > 1 similar to 2. Catecholase and phosphatase activities of the complexes have been investigated in DMF medium using 3,5-di-tert-butylcatechol (3,5-DTBC) and 4-nitrophenylphosphate as substrates respectively. Co-ligands have prominent role on phosphatase activity of the complexes where the order of activity in terms of k(cat) value is 4 > 1 > 2 > 3. Interestingly, only complex 4 is active in catalyzing the aerobic oxidation of 3,5-DTBC. The presence of readily labile solvent molecule in one of the zinc centers of complex 4 perhaps takes the key role for initiating substrate-Zn interaction and thereby the activity. Radical pathway is the probable reason behind the catecholase activity as is evident from EPR study. Solid state thermal analysis suggests that ZnO is the thermally stable end product for complexes 1, 2 and 4, whereas it is ZnS in case of complex 3.
    Polyhedron 01/2015; 85:320–328. DOI:10.1016/j.poly.2014.08.011 · 2.05 Impact Factor
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    ABSTRACT: Two varieties of Co3O4 nano particles (Co3O4-I and Co3O4-II) have been synthesized from two different precursors using a pyrolytic technique. Co3O4-I was prepared by using a coordination polymer [Co(dca)2(2-benzoylpyridine)]n (dca = dicyanamide) as sole precursor, whereas Co3O4-II was obtained from a dinuclear complex [Co2(HL)(OAc)2](OAc)2·4H2O [HL = 2,6-bis(N-ethylpiperazine-iminomethyl)-4-methyl phenol]. The synthesized nanoparticles were characterized by FTIR spectroscopy, magnetic measurements and X-ray diffraction studies. Both Co3O4-I and Co3O4-II are high-quality mono-dispersed, stable and defect-free nanoparticles. The surface morphology of these nanoparticles was revealed by scanning electron microscopy. Co3O4-I nanoparticles have square shape and size ranging from 10 to 25 nm, whereas Co3O4-II nanoparticles have hexagonal shape with larger particle size (100-150 nm). The size distribution of the nanoparticles was determined by dynamic light scattering. The particle size and microstructure were studied by transmission electron microscopy (TEM) images. These nanoparticles show an effective anti-microbial activity, employing Staphylococcus aureus and Escherichia coli as model microbial species, evidenced from the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values.
    RSC Advances 01/2014; 4(29):15022. DOI:10.1039/c3ra47769j · 3.84 Impact Factor
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    ABSTRACT: Three new mononuclear nickel(II) complexes, namely, [NiL(1)(H2O)3]I2·H2O (1), [NiL(1)(H2O)3]Br2·H2O (2), and [NiL(1)(H2O)3]Cl2·2H2O (3) [HL(1) = 2-[(2-piperazin-1-ylethylimino)methyl]phenol], have been synthesized and structurally characterized. Structural characterization reveals that they possess similar structure: [NiL(1)(H2O)3](2+) complex cations, two halide counteranions, and lattice water molecules. One of the nitrogen atoms of the piperazine moiety is protonated to provide electrical neutrality to the system, a consequence observed in earlier studies (Inorg. Chem. 2010, 49, 3121; Polyhedron 2013, 52, 669). Catecholase-like activity has been investigated in methanol by a UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol (3,5-DTBC) as the model substrate. Complexes 1 and 2 are highly active, but surprisingly 3 is totally inactive. The coordination chemistries of 1 and 2 remain unchanged in solution, whereas 3 behaves as a 1:1 electrolyte, as is evident from the conductivity study. Because of coordination of the chloride ligand to the metal in solution, it is proposed that 3,5-DTBC is not able to effectively approach an electrically neutral metal, and consequently complex 3 in solution does not show catecholase-like activity. Density functional theory (DFT) calculations corroborate well with the experimental observations and thus, in turn, support the proposed hypothesis of inactivity of 3. The cyclic voltametric study as well as DFT calculations suggests the possibility of a ligand-centered reduction at -1.1 V vs Ag/AgCl electrode. An electron paramagnetic resonance (EPR) experiment unambiguously hints at the generation of a radical from EPR-inactive 1 and 2 in the presence of 3,5-DTBC. Generation of H2O2 during catalysis has also been confirmed. DFT calculations support the ligand-centered radical generation, and thus a radical mechanism has been proposed for the catecholase-like activity exhibited by 1 and 2. Upon heating, 2 and 3 lose water molecules in two steps (first lattice waters, followed by coordinating water molecules), whereas 3 loses four water molecules in a single step, as revealed from thermogravimetric analysis. The totally dehydrated species are red, in all cases having square-planar geometry, and have amorphous nature, as is evident from a variable-temperature powder X-ray diffraction study.
    Inorganic Chemistry 11/2013; 52(23). DOI:10.1021/ic401819t · 4.79 Impact Factor
  • Jaydeep Adhikary, Averi Guha, Tanmay Chattopadhyay, Debasis Das
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    ABSTRACT: Three homogeneous catalysts, (MnLCl)-Cl-1 center dot 2H(2)O(1.2 H2O) (HmC-1), FeL1(NO3)center dot 3H(2)O (HmC-2) and CoL1(NO3)center dot 2H(2)O (HmC-3) [L-1 = N, N'-ethylenebis(3-formyl-5-methylsalicylaldimine)] have been synthesized and characterized. The catalytic activity of HmC-1, -2 and -3 for epoxidation of alkenes has been investigated in the presence of terminal oxidant tert-butyl hydrogen peroxide (TBHP), in two solvents CH3CN and CH2Cl2. Epoxidation of alkenes catalyzed by HmC-2 and HmC-3 in two solvents CH3CN and CH2Cl2, have also been investigated with of iodosylbenzene (PhIO) as terminal oxidant. The epoxidation study with HmC-1 as catalyst was reported earlier using PhIO as oxidant. Highly ordered 2D-hexagonal mesoporous silica has been functionalized with 3-aminopropyltriethoxysilane (3-APTES) and this has been used to heterogenize the three synthesized homogeneous catalysts and thereby obtained three new heterogeneous catalysts HtC-1, HtC-2 and HtC-3. The heterogeneous catalysts have been characterized by FT-IR, solid state UV-Vis spectroscopy, powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The catalytic activity of these heterogeneous catalysts [HtC-(1-3)] for epoxidation of alkenes has been investigated in the presence of two terminal oxidants PhIO and TBHP, in two solvents CH3CN and CH2Cl2 under mild conditions and compared their activity with their homogeneous counterpart.
    Inorganica Chimica Acta 09/2013; 406:1-9. DOI:10.1016/j.ica.2013.06.045 · 2.04 Impact Factor
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    ABSTRACT: 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.
    Journal of Molecular Structure 06/2013; 1042:104–111. DOI:10.1016/j.molstruc.2013.03.051 · 1.60 Impact Factor
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    ABSTRACT: Four new mononuclear nickel(II) complexes, namely [NiL1(H2O)(3)](NO3)(2) (1), [NiL2(H2O)(3)](NO3)(2) (2), [NiL3(H2O)(3)](NO3)(2) (3) and [NiL4(ClBz)(H2O)]center dot 1.25(H2O) (4) have been synthesized via Schiff-base formation by condensation between 2-benzoylpyridine and N-(2-aminoethyl)pyrrolidine for L-1, salicylaldehyde and N-(2-aminoethyl)piperazine (L-2), 5-chlorosalicylaldehyde and N-(2-aminoethyl)piperazine (L-3), and 5-chlorosalicylaldehyde and N-(2-aminoethyl)morpholine (L-4). 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.
    Polyhedron 03/2013; 52:669-678. DOI:10.1016/j.poly.2012.07.088 · 2.05 Impact Factor
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    ABSTRACT: Four dinuclear and three mononuclear Zn(II) complexes of phenol-based compartmental ligands (HL(1)-HL(7)) have been synthesized with the aim to investigate the viability of a radical pathway in catecholase activity. The complexes have been characterized by routine physicochemical studies as well as X-ray single-crystal structure analysis: [Zn(2)(H(2)L(1))(OH)(H(2)O)(NO(3))](NO(3))(3) (1), [Zn(2)L(2)Cl(3)] (2), [Zn(2)L(3)Cl(3)] (3), [Zn(2)(L(4))(2)(CH(3)COO)(2)] (4), [Zn(HL(5))Cl(2)] (5), [Zn(HL(6))Cl(2)] (6), and [Zn(HL(7))Cl(2)] (7) [L(1)-L(3) and L(5)-L(7) = 2,6-bis(R-iminomethyl)-4-methylphenolato, where R= N-ethylpiperazine for L(1), R = 2-(N-ethyl)pyridine for L(2), R = N-ethylpyrrolidine for L(3), R = N-methylbenzene for L(5), R = 2-(N-methyl)thiophene for L(6), R = 2-(N-ethyl)thiophene for L(7), and L(4) = 2-formyl-4-methyl-6-N-methylbenzene-iminomethyl-phenolato]. Catecholase-like activity of the complexes has been investigated in methanol medium by UV-vis spectrophotometric study using 3,5-di-tert-butylcatechol as model substrate. All complexes are highly active in catalyzing the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ). Conversion of 3,5-DTBC to 3,5-DTBQ catalyzed by mononuclear complexes (5-7) is observed to proceed via formation of two enzyme-substrate adducts, ES1 and ES2, detected spectroscopically, a finding reported for the first time in any Zn(II) complex catalyzed oxidation of catechol. On the other hand, no such enzyme-substrate adduct has been identified, and 3,5-DTBC to 3,5-DTBQ conversion is observed to be catalyzed by the dinuclear complexes (1-4) very smoothly. EPR experiment suggests generation of radicals in the presence of 3,5-DTBC, and that finding has been strengthened by cyclic voltammetric study. Thus, it may be proposed that the radical pathway is probably responsible for conversion of 3,5-DTBC to 3,5-DTBQ promoted by complexes of redox-innocent Zn(II) ion. The ligand-centered radical generation has further been verified by density functional theory calculation.
    Inorganic Chemistry 08/2012; 51(16):8750-9. DOI:10.1021/ic300400v · 4.79 Impact Factor
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    ABSTRACT: 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 angstrom. 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 [Zn2L2(CH3CO2)(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.
    Journal of Coordination Chemistry 11/2011; 64(21-21):3817-3831. DOI:10.1080/00958972.2011.631534 · 2.22 Impact Factor
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    ABSTRACT: Three Ni(II) complexes of cresol-based Schiff-base ligands, namely [Ni2(L1)(NCS)3(H2O)2], (1) [Ni2(L2)(CH3COO)(NCS)2(H2O)] (2) and [Ni2(L3)(NCS)3] (3), (where L1 = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L2 = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L3 = 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-di-tert-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 [Ni2(L1)(NCS)2(NCO)(H2O)2] (1′) and [Ni2(L2)(CH3COO)(NCO)(NCS)(H2O)] (2′) derivatives, respectively, whereas 3 remains unaltered under same reaction conditions.
    Transition Metal Chemistry 11/2011; 36(8):829. DOI:10.1007/s11243-011-9537-4 · 1.40 Impact Factor
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    ABSTRACT: 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 P1̅ 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 P212121. 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.
    Crystal Growth & Design 06/2011; 11(7):3198–3205. DOI:10.1021/cg2004485 · 4.56 Impact Factor
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    ABSTRACT: A coordination polymer, Na2Cd2I6L2(H2O)6 [L = Urotropine] has been employed as sole precursor to synthesize CdO particles. Two different preparation methods viz (i) pyrolysis of the title compound at 700 °C for 2 h and (ii) forming cadmium hydroxide from the title compound followed by pyrolysis at 700 °C for 2 h have been used for the synthesis of nano sized CdO-I and CdO-II, respectively. From powder XRD data the lattice parameters (0.4701 and 0.4696 nm respectively for the two samples) and particle size (~ 77 and 30 nm for CdO-I and CdO-II) have been evaluated. Morphology of the two varieties of CdO is widely different as is evident from their SEM images. The estimated values of the band gap of 2.53 eV and 2.59 eV for CdO-I and CdO-II respectively are obtained from the optical spectral analysis.
    Materials Letters 02/2011; 65(4):783–785. DOI:10.1016/j.matlet.2010.11.055 · 2.27 Impact Factor
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    ABSTRACT: Three new polymeric complexes of cadmium(II) with imidazole and its derivatives [imidazole (Im), benzimidazole (Bim) and 1-methylimidazole (Mim)] mediated by thiocyanate and dicyanamide (dca) anions have been synthesized and characterized by X-ray single crystal structure analysis. The structure analyses reveal that complexes [Cd(SCN)2(Bim)2]n (1) and [Cd(dca)2(Im)2]n (2) are 1D coordination polymers, whereas complex [Cd(dca)2(Mim)2]n (3) adopts a 2D network of (4, 4) topology and thereby suggests that the dimensionality of the coordination polymers are affected by the choice of the counter anions and by the organic ligands. All the species exhibit interesting luminescence property in methanol and in solid state originated from ligands-centered π–π* transitions. The π–π interactions occurring between organic rings (Im, Mim, and Bim) are observed to be important in controlling the fluorescence property of the species.
    Polyhedron 01/2011; 30(1):163-168. DOI:10.1016/j.poly.2010.10.003 · 2.05 Impact Factor
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    ABSTRACT: A unique heterotrinuclear nitrate-bridged complex of hexanitrate praseodymium(III) and dicopper(II) compartmental species has been synthesized and characterized by X-ray single crystal structure analysis. The structure determination indicates that the dinuclear copper moiety undergoes a tilted deformation (with respect to the dicopper complex) upon connection to the lanthanide species via a rare nitrate bridge. The trinuclear species is highly fluorescent owing to the presence of praseodymium.
    Journal of Coordination Chemistry 11/2010; 63(21-21):3714-3723. DOI:10.1080/00958972.2010.520315 · 2.22 Impact Factor
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    ABSTRACT: A new dinuclear nickel(II) complex, [Ni(2)(LH(2))(H(2)O)(2)(OH)(NO(3))](NO(3))(3) (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine-iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV-vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.
    Inorganic Chemistry 03/2010; 49(7):3121-9. DOI:10.1021/ic901546t · 4.79 Impact Factor
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    ABSTRACT: Four new coordination polymers of cadmium(II) with hexamethylenetetramine (htm) have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single crystal structure analysis. They are [CdBr(htm)(SCN)(H2O)2·CH3OH]n (1), [CdI(htm)(SCN)(H2O)2·0.5(CH3OH)]n (2), [Cd2(htm)3(SCN)4(H2O)]n·nH2O (3) and [Cd3Br6(htm)2(H2O)5·(htm)(H2O)6]n (4). Complexes 1, 2 and 3 exhibit 1D polymeric structure and complex 4 shows a 2D undulated layered arrangement, containing Cd6(htm)6 hexagonal units as building block, which extended to a 3D supramolecular architecture through hydrogen bonding. Thorough thermal investigation suggest that as far as the thermal stability of Cd(II)-htm bond is concerned it attains the maximum in complex 1 and minimum in complex 4. In case of complex 3 the thermal study inferred that CdS end product was obtained at ∼730°C, whereas in case of other complexes the thermally stable end product remained unidentified. Solid state fluorescence study shows that all the complexes are luminescent at room temperature except complex 3.
    Polyhedron 02/2010; 29(3):951-958. DOI:10.1016/j.poly.2009.11.009 · 2.05 Impact Factor
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    ABSTRACT: Four new coordination polymers of cadmium(II) with hexamethylenetetramine (htm) have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single crystal structure analysis. They are [CdBr(htm)(SCN)(H2O)2�CH3OH]n (1), [CdI(htm)(SCN)(H2O)2�0.5(CH3OH)]n (2), [Cd2(htm)3(SCN)4(H2O)]n�nH2O (3) and [Cd3Br6(htm)2(H2O)5�(htm)(H2O)6]n (4). Complexes 1, 2 and 3 exhibit 1D polymeric structure and complex 4 shows a 2D undulated layered arrangement, containing Cd6(htm)6 hexagonal units as building block, which extended to a 3D supramolecular architecture through hydrogen bonding. Thorough thermal investigation suggest that as far as the thermal stability of Cd(II)-htm bond is concerned it attains the maximum in complex 1 and minimum in complex 4. In case of complex 3 the thermal study inferred that CdS end product was obtained at �730 �C, whereas in case of other complexes the thermally stable end product remained unidentified. Solid state fluorescence study shows that all the complexes are luminescent at room temperature except complex 3.
    Polyhedron 01/2010; 29:951. · 2.05 Impact Factor
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    ABSTRACT: Four side-off compartmental ligands L1-L4 [L1 = N,N'-ethylenebis(3-formyl-5-methyl-salicylaldimine), L2 = N,N'-1-methylethylenebis(3-formyl-5-methylsalicylaldimine), L3 = N,N'-1,1-dimethylethylenebis(3-formyl-5-methylsalicylaldimine) and L4= N,N'-cyclohexenebis(3-formyl-5-methylsalicylaldimine)] having two binding sites, N2O2 and O4, have been chosen to synthesize mononuclear and dinuclear manganese(III) complexes with the aim to study their catecholase activity using 3,5-di-tert-butylcatechol (3,5-DTBC) as substrate in the presence of molecular oxygen. In all cases only mononuclear manganese complexes (1-4) were obtained, with manganese coordination taking place at the N2O2 binding site only, irrespective of the amount of manganese salt used. All these complexes have been characterized by routine physico-chemical techniques. Complex MnL2Cl.4H2O (2) has further been structurally characterized by X-ray single crystal structure analysis. Four dinuclear manganese complexes, 5-8, were obtained after condensing the two pending formyl groups on each ligand (L1-L4) with aniline followed by reaction with MnCl2 to put the second Mn atom onto another N2O2 site. The catalytic activity of all complexes 1-8 has been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in two different solvents, methanol and acetonitrile. The study reveals that the catalytic activity is influenced by the solvent and to a significant extent by the backbone of the diamine and the behavior seems to be related mainly to steric rather than electronic factors. Experimental data suggest that a correlation, the lower the E(1/2) value the higher the catalytic activity, can be drawn between E(1/2) and Vmax of the complexes in a particular solvent. The EPR measurements suggest that the catalytic property of the complexes is related to the metal center(s) participation rather than to a radical mechanism.
    Dalton Transactions 10/2009; DOI:10.1039/b902498k · 4.10 Impact Factor

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304 Citations
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Institutions

  • 2013
    • Indian Institute of Engineering Science and Technology, Shibpur
      • Department of Chemistry
      Hawrah, West Bengal, India
  • 2011
    • Università degli Studi di Trieste
      Trst, Friuli Venezia Giulia, Italy
  • 2000–2011
    • University of Calcutta
      • Department of Chemistry
      Kolkata, Bengal, India
  • 2005
    • Visva Bharati University
      • Department of Chemistry
      Bolpur, Bengal, India