Kinetics study of the reduction of [(bipy)₂Mn^IIIO₂Mn^IV(bipy)₂]³⁺ by thiocyanate ion in aqueous hydrochloric acid

Abstract

The kinetics of the reduction of [(bipy)₂Mn^IIIO₂Mn^IV(bipy)₂]³⁺ by thiocyanate ion (SCN-) has been studied in aqueous hydrochloric acid medium. The stoichiometric determination showed a mole ratio of 1:3. Kinetics study was carried out under pseudo - first order condition and showed that the rate of reaction was first order with respect to both [(bipy)₂Mn^IIIO₂Mn^IV(bipy)₂]³⁺ and [SCN^-]. The rate of the reaction was acid dependent and was found to decrease with increase in ionic strength, suggesting a negative salt effect. The addition of added cations and anions (Ni²⁺, Mg²⁺, NO₃^- and CH₃COO^-) increased the rate of reaction and Michaelis-Menten’s plot showed a zero intercept. Based on the results of the spectroscopic studies, kinetic evidences from Michaelis–Menten’s plot and interaction with added ions, an outer–sphere mechanism has been proposed for the reaction of [(bipy)₂Mn^IIIO₂Mn^IV(bipy)₂]³⁺ - SCN- system.

Keywords: Kinetics, Reaction, [(bipy)₂Mn^IIIO₂Mn^IV(bipy)₂]³⁺, Thiocyante Ion