Electron Transfer Reactions of Photochemically Generated Ruthenium(III)–Polypyridyl Complexes with Methionines |
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| Authors: | DHARMARAJ THIRUPPATHI PERIYAKARUPPAN KARUPPASAMY MUNIYANDI GANESAN VELUCHAMY KAMARAJ SIVASUBRAMANIAN THANGAMUTHU RAJENDRAN SEENIVASAN RAJAGOPAL |
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| Institution: | 1. Postgraduate and Research Department of Chemistry, Vivekananda College, , Madurai, 625 234 India;2. Department of Chemistry, PSNA College of Engineering and Technology, , Dindigul 624 622, India;3. School of Chemistry, Madurai Kamaraj University, , Madurai, 625 021 India |
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| Abstract: | The oxidation of methionine (Met) plays an important role during biological conditions of oxidative stress as well as for protein stability. Ruthenium(III)–polypyridyl complexes, Ru(NN)3]3+, generated from the photochemical oxidation of the corresponding Ru(II) complexes with molecular oxygen, undergo a facile electron transfer reaction with Met to form methionine sulfoxide (MetO) as the final product. Interaction of Ru(NN)3]3+ with methionine leads to the formation of >S+● and (>S∴S<)+ species as intermediates during the course of the reaction. The interesting spectral, kinetic, and mechanistic study of the electron transfer reaction of four substituted methionines with six Ru(NN)3]3+ ions carried out in aqueous CH3CN (1:1, v/v) by a spectrophotometric technique shows that the reaction rate is susceptible to the nature of the ligand in Ru(NN)3]3+ and the structure of methionine. The rate constants calculated by the application of Marcus semiclassical theory to these redox reactions are in close agreement with the experimental values. |
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