Publications by authors named "Rajkumar Eswaran"

This paper studies the anticancer potency of dendritic poly(aryl ether)-substituted polypyridyl ligand-based ruthenium(II) coordination entities. The dendritic coordination entities were successfully designed, synthesized, and characterized by different spectral methods such as Fourier transform infrared (FTIR), H and C- NMR, and mass spectrometry. Further, to understand the structure and solvation behavior of the coordination entities, we performed all-atom molecular dynamics (MD) simulations.

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 (L.) Pers., (Lythraceae), commonly called Banaba, is a native plant of Southeast Asia and is widely used in the treatment of diabetics, obesity, kidney diseases, and other inflammatory disorders.

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Luminescent heteroleptic ruthenium(II) complexes of type RuLn X(3-n) [L = 1,10-phenanthroline (phen), X = 4,7 diphenyl phenanthroline disulfonate, (dpsphen) n = 0,1,2,3] were synthesized and their photophysical properties investigated in homogeneous and cationic (CTAB), anionic (SDS) and nonionic (Triton X-100) micelles. The luminescent quantum yield and lifetime of the complexes were found to increase in the presence of micellar media and on the introduction of a disulfonate ligand into the coordination sphere. Both electrostatic and hydrophobic interactions play an important role in the micellar media.

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Four [Ru(NN)(3)](2+) complexes (NN = polypyridine) with ligands of varying hydrophobicity with different charges +2, 0 and -4 were synthesized. The photophysics and photoinduced electron transfer reactions of these Ru(II)-complexes with dimethylaniline (DMA) as the quencher have been studied in aqueous medium and ionic and non-ionic micellar medium. The extent of binding of the complexes with the surfactant interface is evident from the calculated binding constant values (K).

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Amphiphilic ruthenium(II) complexes II–IV were synthesized and their photophysical properties were investigated in the presence of anionic (SDS), cationic (CTAB) and neutral (Triton X-100) micelles. The absorption and emission spectral data in the presence of micelles show that these Ru(II) complexes are incorporated in the micelles. There are two types of interaction between complexes I–IV and the micelles: hydrophobic and electrostatic.

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With the aim of mimicking, at basic level the photoinduced electron transfer process in the reaction center of photosystem II, ruthenium(II)-polypyridyl complexes, carrying amino acids were synthesized and studied their photoinduced electron transfer reactions with quinones by steady state and time resolved measurements. The reaction of quinones with excited state of ruthenium(II)-complexes, I-V in acetonitrile has been studied by luminescence quenching technique and the rate constant, k(q), values are close to the diffusion controlled rate. The detection of the semiquinone anion radical in this system using time-resolved transient absorption spectroscopy confirms the electron transfer nature of the reaction.

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Three ruthenium(II)-bipyridine complexes carrying a tyrosine moiety were synthesized and photophysical and electron transfer studies with quinones were carried out using absorption and emission spectral techniques. The binding efficiency of quinones with ruthenium(II)-bipyridine complexes was also studied using these techniques. The binding efficiency was moderate and similar for all complexes with all quinones.

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[Ru(dcbpy)(3)](2+) (dcbpy = 4,4'-dicarboxyl-2,2'-bipyridine) ion, in the excited state, undergoes facile electron transfer (ET) reaction with aryl methyl and dialkyl sulfides and the quenching rate constant, k(q) value is sensitive to the structure of the sulfide. The detection of the sulfur radical cation in this system using time-resolved transient absorption spectroscopy confirms the ET nature of the reaction. The semiclassical theory of ET has been successfully applied to the photoluminescence quenching of [Ru(dcbpy)(3)](2+) with sulfides.

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