• K Senthil Kumar

      Articles written in Journal of Chemical Sciences

    • Chemistry of selected cyclic P(III) compounds possessing a P-Cl bond

      K C Kumaraswamy Sudha Kumaraswamy Praveen Kommana N Satish Kumar K Senthil Kumar

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      The compounds [CH2(6-t-Bu-4-Me-C6H2O)2]PCl (1), (OCH2CMe2CH2O)-PCl (2), and [ClPN(t-Bu)]2 (3) have been utilized as precursors in the synthesis of (i) new pentacoordinate phosphorus compounds [e.g. CH2(6-t-Bu-4-Me-C6H2O)2 P(NRR′)(O2C6C14), CH2(6-t-Bu-4-Me-C6H2O)2PX[OC(O-i-Pr)N=N(C(O)O-i-Pr)],(ii) cyclic phosphates and their complexes [e.g. imidazolium+CH2(6-t-Bu-4-Me-C6H2O)2PO2-.MeOH], (iii) new cycloaddition products [e.g. CH2(6-t-Bu-4-Me-C6H2O)2PC(CO2Me)C(CO2Me)C(O)N, (iv) macrocyclic compounds [e.g. [(t-BuN)P]2[-OCH2CMe2CH2O-]h2] and (v) phosphonates [e.g. (OCH2CMe2CH2O)P (O)CH2C(CN)=CHC5H4FeC5H5]. The synthetic and structural aspects of these new products are discussed.

    • Photoprocesses of coordination compounds and dyes in solution and nanoporous materials: Evolution from milliseconds to femtoseconds

      P Natarajan K Duraimurugan K Senthil Kumar

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      The photoredox reactions of cobalt(III), nickel(II) complexes and organic dyes are reviewed with particular emphasis on using flash photolysis methods to identify the transients in the time scale from milliseconds to subpicoseconds. The excitation flash radiation initially was limited to flash lamps with a time resolution to study the decay of the excited states and the fast reactions of photo produced transients in milliseconds and microseconds. Some of the photolysis reactions investigated provide details in real time including the thermal reactions of molecular oxygen with cobalt(II) amine systems and the cobalt (III) alkyl complex formation on photolysis of cobalt(III) aminoacid complexes. Photoredox reactions of thiazine and safranine dyes are investigated using time resolved absorption and emission techniques in solution and on encapsulation in micro and mesoporous host materials. Picosecond and femtosecond diffuse reflectance fluorescence investigations in the porous solid host materials show intramolecular proton transfer reactions of the dyes and deprotonation of the dyes in the excited states. Photosensitization of nanoparticles of semiconductors, anatase TiO2 and ZnO by the excited states of dyes in meso and microporous silicate hosts is investigated using pico and femtosecond fluorescence and transient absorptions techniques and the results are reviewed.

    • Thermodynamic, kinetic and electronic structure aspects of a charge-transfer active bichromophoric organofullerene

      K Senthil Kumar Archita Patnaik

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      Our recent work on charge transfer in the electronically push-pull dimethylaminoazobenzene-fullerene C60 donor-bridge-acceptor dyad through orbital picture revealed charge displacement from the n$_{\text{(N=N)}}$ (non-bonding) and $\pi_{\text{(N=N)}}$ type orbitals centred on the donor part to the purely fullerene centred LUMOs and (LUMO+n) orbitals, delocalized over the entire molecule. Consequently, this investigation centres around the kinetic and thermodynamic parameters involved in the solvent polarity dependent intramolecular photo-induced electron transfer processes in the dyad, indispensable for artificial photosynthetic systems. A quasi-reversible electron transfer pathway was elucidated with electrode-specific heterogeneous electron transfer rate constants.

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