• G Allen Gnanaraj

      Articles written in Journal of Chemical Sciences

    • Excited state electron transfer reactions of tris(2,2′-bipyridine) chromium (III) ion with organic sulphides

      G Allen Gnanaraj S Rajagopal C Srinivasan

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      The quenching rate constants,kq, for the excited state electron transfer reactions oftris(2,2′-bipyridine)chromium(III) ion with several aryl methyl sulphides (ArSMe) obtained by the luminescence quenching technique, are accelerated by electron releasing groups and retarded by electron withdrawing groups present in the aryl moiety of ArSMe. The plot ofRT Inkq vs.E1/2 values of different sulphides is linear, indicating the electron transfer nature of the reaction. Studies with alkyl phenyl sulphides demonstrate the importance of the steric effect in these photoredox reactions.

    • Nonadiabaticity in the photoinduced electron transfer reactions of metal complexes

      S Rajagopal C Srinivasan G Allen Gnanaraj

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      The rate of electron transfer (ET) in a variety of chemical and biological processes is influenced by factors like the free energy change (†G), the donor-acceptor electronic coupling and the medium. The effect of donor-acceptor electronic coupling on the rate of photoinduced intermolecular electron transfer is considered by taking Ru(II) and Cr(III) metal complexes in the excited state as electron acceptors and organic compounds as electron donors. The electronic coupling between the donor and acceptors depends strongly on donor-acceptor distance. The electron transfer distance is varied by introducing alkyl groups of different sizes either on the bipyridine ligand of the metal complex or on the quencher. The semiclassical theory of electron transfer expresses kET as the product of a nuclear and an electronic transmission coefficient (Kn andKel respectively) and an effective nuclear-vibration frequency (vn),kET =vnKel, Kn. The electron transfer reaction becomes nonadiabatic if the donor-acceptor distance is long. The change of electron transfer mechanism from adiabatic to nonadiabatic due to the introduction of bulky groups is explained in terms of semiclassical theory and from the temperature-dependence study of photoinduced electron transfer reactions of metal complexes.

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