Kinetics study of the reductionof [(bipy)2MnIIIO2MnIV(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 toboth [(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.