Oxidation Of N, N-Dimethylthiourea By Diaquotetrakis(2,2’- BIPYRIDINE) - µ - Oxodiruthenium (III) Ion In Aqueous Acid Medium: A Kinetic Approach To Mechanism Of Reaction

Background: Electron transfer (redox) reactions play very important roles in many biological processes including collagen synthesis, steroid metabolism, the immune response, drug activation, neurotransmitter metabolism, nitrogen fixation, respiration and photosynthesis. Ruthenium complexes with polypyridyl ligands have received much attention owing to their interesting spectroscopic, photophysical, photochemical and electrochemical properties, which are responsible for their potential uses in diverse areas such as photosensitizers for photochemical conversion of solar energy. Thiourea and its derivatives, of which DMTU is one, can be oxidised by a wide variety of oxidising agents and the reaction pathways and final products of the oxidation reaction depend on the reagents used and condition of the reaction mixtures. Materials and Methods: Kinetic and mechanistic studies of the oxidation of N,N-dimethyl thiourea (DMTU) by diaquotetrakis(2,2’-bipyridine) - μ - oxodiruthenium (III) ion, hitherto referred to as Ru2O4+, has been carried out in hydrogen ion concentration, [H+] = 5.0 x 10–2 mol dm-3 (HClO4), ionic strength, I = 0.5 mol dm-3 (NaClO4) and at a temperature, T = 30±1ºC. Results: The reaction revealed that a stoichiometry of 2:1 (DMTU/ Ru2O4+, first order dependence with respect to [DMTU], an acid – independent and inverse acid dependent pathways. The reaction rates were not affected by changes in ionic strength and dielectric constant of the reaction medium. Addition of ions to the reaction medium had little or no effect on the reaction rates. There was evidence of the participation of free radicals in the reaction. There was no shift in λmax of the reaction mixture 1 minute after start of reaction. Michaelis Menten plot revealed no appreciable intercept. Conclusion: Based on the findings, an outersphere mechanism is implicated to operate in the reaction and a plausible mechanism is proposed