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Dive into the research topics where Tanmay Chattopadhyay is active.

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Featured researches published by Tanmay Chattopadhyay.


Inorganic Chemistry | 2012

Radical Pathway in Catecholase Activity with Zinc-Based Model Complexes of Compartmental Ligands

Averi Guha; Tanmay Chattopadhyay; Nanda D. Paul; Madhuparna Mukherjee; Somen Goswami; Tapan Kumar Mondal; Ennio Zangrando; Debasis Das

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 | 2013

A Combined Experimental and Theoretical Investigation on the Role of Halide Ligands on the Catecholase-like Activity of Mononuclear Nickel(II) Complexes with a Phenol-Based Tridentate Ligand

Jaydeep Adhikary; Prateeti Chakraborty; Sudhanshu Das; Tanmay Chattopadhyay; Antonio Bauzá; Shyamal Kumar Chattopadhyay; Bipinbihari Ghosh; Franz A. Mautner; Antonio Frontera; Debasis Das

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 | 2009

Metal-Assisted Oxazolidine/Oxazine Ring Formation in Dinuclear Zinc(II) Complexes: Synthesis, Structural Aspects, and Bioactivity

Arpita Banerjee; Subhalakshmi Ganguly; Tanmay Chattopadhyay; Kazi Sabnam Banu; Amarendra Patra; Santanu Bhattacharya; Ennio Zangrando; Debasis Das

Three novel dinuclear Zn(II) complexes of phenol-based compartmental macrocyclic ligands have been synthesized and characterized by routine physicochemical techniques as well as by X-ray single-crystal structure analysis. The dinuclear macrocyclic complexes 1, 2, and 3 were obtained through a 1:2 condensation reaction of 2,6-diformyl-4-methylphenol and N-(hydroxyalkyl) ethylenediamine (L(1), L(2), and L(3), respectively) in the presence of zinc(II) acetate, followed by the addition of thiocyanate anion [L(1) = N-(2-hydroxyethyl)ethylenediamine, L(2) = N-(3-hydroxypropyl)ethylenediamine, and L(3) = N-(2-hydroxypropyl)ethylenediamine]. The synthesized 18-membered macrocycles are noted to be structurally unique, and their formation proceeds with the generation of two oxazolidine side rings in complexes 1 and 3 and two oxazine side rings in 2, along with the creation of four new chiral centers in each case. Complexes 1 and 2 are characterized by a butterfly-like arrangement with the SCN ligands situated on the same side with respect to the Zn(2)O(2) moiety, whereas the centrosymmetric complex 3 exhibits a stepped arrangement with parallel methyl-phenoxy fragments (spaced at ca. 1.5 A) and trans located SCN ligands with respect to the Zn(2)O(2) core. The formation of these unusual macrocycles is considered to be zinc-mediated. Preliminary studies with the complexes show that all of them exhibit an inhibitory effect, on the cell proliferation of human stomach cancer cell line AGS, though with different degrees, where complex 3 shows the highest efficiency.


Journal of Coordination Chemistry | 2011

Dinuclear zinc(II) complexes with compartmental ligands: syntheses, structures, and bioactivities as artificial nuclease

Pali Maiti; Amitava Khan; Tanmay Chattopadhyay; Sudhanshu Das; Krishnendu Manna; Dipayan Bose; Sanjit Dey; Ennio Zangrando; Debasis Das

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 (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 . 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 | 2017

Fe3O4@dopa (dopa = dopamine hydrochloride) functionalized Mn(III) Schiff base complex: A promising magnetically separable heterogeneous catalyst for oxidative transformations

Aratrika Chakraborty; Tanmay Chattopadhyay

Abstract A chiral Schiff base complex has been prepared by treating (R)-1,2-diaminopropane with 3,5-dichlorosalicylaldehyde in ethanol, followed by addition of manganese chloride hexahydrate to generate a homogeneous catalyst, [MnL(Cl)(H2O)] (HMN). Crystal structure of the complex reveals its mononuclear nature. Circular dichroism (CD) studies indicate that the ligand and its corresponding complex contain an asymmetric center. The catalytic activity of HMN toward epoxidation of alkenes, oxidation of alcohols and oxidation of alkanes has been investigated in the presence of iodosylbenzenediacetate (PhI(OAc)2), in acetonitrile. In the present work we found yields to be much higher compared to our previous approaches. For further adaptation, we attached our efficient homogeneous catalyst with surface modified magnetic nanoparticles (Fe3O4@dopa) and thereby obtained a new magnetically separable nanocatalyst Fe3O4@dopa@MnLCl (FDM). This catalyst has been characterized and its oxidation ability assessed in similar conditions as those used for the homogeneous catalyst. Enantiomeric excess in epoxide yield reveals retention of chirality of the active site of Fe3O4@dopa@MnLCl. The catalyst can be recovered by magnetic separation and recycled several times without significant loss of catalytic activity.


Inorganic Chemistry | 2008

Catechol Oxidase Activity of a Series of New Dinuclear Copper(II) Complexes with 3,5-DTBC and TCC as Substrates: Syntheses, X-ray Crystal Structures, Spectroscopic Characterization of the Adducts and Kinetic Studies

Kazi Sabnam Banu; Tanmay Chattopadhyay; Arpita Banerjee; Santanu Bhattacharya; Eringathodi Suresh; Munirathinam Nethaji; Ennio Zangrando; Debasis Das


Inorganic Chemistry | 2010

A Unique Nickel System having Versatile Catalytic Activity of Biological Significance

Tanmay Chattopadhyay; Madhuparna Mukherjee; Arindam Mondal; Pali Maiti; Arpita Banerjee; Kazi Sabnam Banu; Santanu Bhattacharya; Bappaditya Roy; Dhrubajyoti Chattopadhyay; Tapan Kumar Mondal; Munirathinam Nethaji; Ennio Zangrando; Debasis Das


Crystal Growth & Design | 2011

Thiocyanate and Dicyanamide Anion Controlled Nuclearity in Mn, Co, Ni, Cu, and Zn Metal Complexes with Hemilabile Ligand 2-Benzoylpyridine

Totan Ghosh; Tanmay Chattopadhyay; Sudhanshu Das; Sandip Mondal; Eringathodi Suresh; Ennio Zangrando; Debasis Das


Journal of Molecular Catalysis A-chemical | 2005

Bromodimethylsulfonium bromide: A useful reagent for acylation of alcohols, phenols, amines, thiols, thiophenols and 1,1-diacylation of aldehydes under solvent free conditions

Abu T. Khan; Samimul Islam; Adinath Majee; Tanmay Chattopadhyay; Subrata Ghosh


Polyhedron | 2013

A series of mononuclear nickel(II) complexes of Schiff-base ligands having N,N,O- and N,N,N-donor sites: Syntheses, crystal structures, solid state thermal property and catecholase-like activity

Averi Guha; Kazi Sabnam Banu; Sudhanshu Das; Tanmay Chattopadhyay; Ria Sanyal; Ennio Zangrando; Debasis Das

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Debasis Das

University of Calcutta

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Averi Guha

University of Calcutta

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Manami Ghosh

Visva-Bharati University

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