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Bhattacharya P.,Indian Association for The Cultivation of Science | Bhattacharya P.,Budge Budge Institute of Technology | Chakravorti S.,Indian Association for The Cultivation of Science
Chemical Physics Letters

This Letter reports the photophysics of 4,4-diaminodiphenyl sulfone in anionic and cationic reverse micelles (RM). Decreased fluorescence intensity with significant blue shift of intramolecular charge transfer (ICT) fluorescence maximum and longer emission lifetime of the entrapped probe in motionally restricted water nano-pool of anionic RM could be observed. Bi-exponential decay in anionic RM appears due to polarity heterogeneity in the pool. In a nut shell, experiments establish that the probe is anchored in the micellar head group region of anionic RM vis-à-vis far away from the core in cationic RM. Increasing pool size show the opposite effect to the probe. © 2013 Elsevier B.V. All rights reserved. Source

Dutta A.K.,Bengal Engineering and Science University | Maji S.K.,Bengal Engineering and Science University | Dutta S.,Budge Budge Institute of Technology
Journal of Molecular Structure

An oxo-centred, carboxylate bridged trinuclear iron(III) complex [Fe 3(μ 3-O)(O 2CCH 2Cl) 6(H 2O) 3]ClO 4·9H 2O (1·9H 2O) has been synthesized and characterized on the basis of X-ray crystallography, elemental analysis, cyclic voltammetric, UV-vis and IR spectroscopic techniques. Molecular structure has been established by X-ray diffraction analysis and reveals that the complex 1·9H 2O crystallizes in the rhombohedral space group R 3 with a = 18.0070(6) Å, b = 18.0070(6) Å, c = 9.7962(5) Å, α = β = 90.00° and γ = 120.00°. In the highly symmetric trinuclear structure, three iron(III) atoms occupy vertices of equilateral triangle and exhibits a quasi-reversible one-electron reduction at E = +0.337 V vs Ag/AgCl (ΔE p = 0.079 V) due to the [Fe 3(μ 3-O) (O 2CCH 2Cl) 6(H 2O) 3] +/[Fe 3(μ 3-O)(O 2CCH 2Cl) 6(H 2O) 3] couple. In addition, ascending difference between cathodic and anodic peak potentials (ΔE p) with the increasing scan rate confirmed the reduction wave to be quasi-reversible. © 2012 Elsevier B.V. All rights reserved. Source

Bhattacharya P.,Indian Association for The Cultivation of Science | Bhattacharya P.,Budge Budge Institute of Technology | Sahoo D.,Indian Association for The Cultivation of Science | Sahoo D.,Lund University | Chakravorti S.,Indian Association for The Cultivation of Science
Journal of Photochemistry and Photobiology A: Chemistry

The modulation of already established charge transfer (ICT) emission characteristics of 4,4′-diaminodiphenyl sulfone (Dapsone) in different micelles and also its further alterations due to physicochemical change of micelles in company with added room temperature ionic liquid (IL) have been elucidated in this paper with the help of steady state and time-resolved fluorescence spectroscopy. Dapsone seems to enter inside the cationic micelle beyond interfacial region, as evinced by the emission intensity enhancement and blue shift. In anionic micelle little intensity increase and the blue shift of Dapsone point to the presence of the probe near the interfacial region. From Cu 2+ quenching study it has been confirmed that among the ionic micelles the probe makes shallow penetration in anionic micelle compared to that in cationic micelle. In non ionic surfactants the accessibility of the probe to the ionic quencher increases with increasing chain length. The probe's emission intensity is highest in non ionic Tween 20, but it starts decreasing with increasing alkyl chain length up to Tween 60 and it drastically reduces in Tween 80 nearly same as that in water. IL seems to affect the micellization of anionic, cationic and nonionic micelles differently resulting in shrinking and inflating the micellar size. The calculated rotational relaxation time of the micelle-probe complex is very slow compared to the probe rotation inside micelle. © 2012 Elsevier B.V. Source

Saha D.,Jadavpur University | Das S.,Jadavpur University | Karmakar S.,Jadavpur University | Dutta S.,Budge Budge Institute of Technology | Baitalik S.,Jadavpur University
RSC Advances

A mixed-ligand bimetallic ruthenium(ii) complex of composition [(bpy) 2Ru(H2PyImPhen)Ru(bpy)2](ClO4) 4 (1), where H2PyImPhen = 2,6-di(1H-imidazo[4,5-f][1,10] phenanthrolin-2-yl)pyridine and bpy = 2,2′-bipyridine has been synthesized and characterized using standard analytical and spectroscopic techniques. The X-ray crystal structure of its N-H deprotonated form (2) has been determined which showed that the compound crystallized in monoclinic form with the space group P21/c. The optimized geometrical parameters for the complexes computed both in the gas phase and in solution are reported and compared with the available X-ray data. The absorption spectra, redox behavior and luminescence properties of the complexes were thoroughly investigated. Complex 1 displays strong luminescence at room temperature with lifetimes in the range of 160-500 ns (aerated condition), depending upon the nature of the solvent. The complex is found to undergo one reversible oxidation in the positive potential window and three successive quasi-reversible reductions in the negative potential window. Both the anion and cation binding properties of 1 were thoroughly investigated in acetonitrile solution using absorption, steady state and time-resolved emission spectral studies. The anion sensing studies revealed that the receptor acts as a sensor for F-, AcO- and H 2PO4-. It is evident that in the presence of excess F- and AcO- ion, deprotonation of the imidazole N-H fragments of 1 occurs. Anion-induced lifetime quenching by F- and AcO- and enhancement by H2PO4-, makes the receptor 1 a suitable lifetime-based sensor for selective anions. Coordination of metal ions such as Mn2+, Co2+, Cu 2+ to the secondary coordination sphere of 1 trigger emission quenching, while metal ions having a completely filled d orbital (such as Zn2+, Cd2+ or Hg2+) do not quench; rather some finite enhancement of the fluorescence intensity of the receptor occurs. Density functional theory (DFT) and time-dependent DFT (TD-DFT) study provides insight into the nature of the ground and the excited states involved in absorption and emission transitions. In particular, the changes in the absorption and emission spectral characteristics of 1 on interaction with anions and cations are also reproduced by our calculations. © 2013 The Royal Society of Chemistry. Source

Dutta S.,Indian Association for The Cultivation of Science | Dutta S.,Budge Budge Institute of Technology | Biswas P.,Bengal Engineering and Science University

To mimic the phosphate ester hydrolysis behavior of purple acid phosphatases the heterobimetallic complex [(BNPP)FeIIIL(μ-BNPP) NiII(H2O)](ClO4) (1) has been synthesized from the precursor complexes [FeIII(LH2)(H2O) 2](ClO4)3·3H2O and [Fe III(LH2)(H2O)Cl](ClO4) 2·2H2O. In these compounds, L2- is the anion of the tetraiminodiphenol macrocyclic ligand (H2L), while LH2 is the zwitterionic form in which the phenolic protons are shifted to the two metal-uncoordinated imine nitrogens, and BNPP is bis(4-nitrophenyl)phosphate. The X-ray crystal structure of compound 1 has been determined. The structure of 1 comprises of two edge-shared distorted octahedrons whose metal centers are bridged by two equatorial phenolate oxygens and two axially disposed oxygens of a BNPP ligand. The internuclear Fe⋯Ni distance is 3.083 . The high-spin iron(III) and nickel(II) in 1 are antiferromagnetically coupled (J = -7.1 cm-1; H = -2J S 1·S2) with S = 3/2 spin ground state. The phosphodiesterase activity of 1 has been studied in 70:30 H2O- (CH3)2SO medium with NaBNPP as the substrate. The reaction rates have been measured by varying pH (3-10), temperature (25-50 °C), and with different concentrations of the substrate and complex at a fixed pH and temperature. Treatment of the rate data, obtained at pH 6.0 and at 35 °C, by the Michaelis-Menten approach have provided the following parameters: K M = 3.6 × 10-4 M, Vmax = 1.83 × 10-7 M s-1, kcat = 9.15 × 10-3 s-1. As compared to the uncatalyzed hydrolysis rate of BNPP, the kcat value is 8.3 × 108 times higher, showing that 1 behaves as an excellent model for phosphate ester hydrolysis. © 2011 Elsevier Ltd. All rights reserved. Source

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