Nonenzymatic NADH-Dependent Reduction of Keggin-Type 12-Tungstocobaltate(III) in Aqueous Medium

Abstract

The kinetics of the electron transfer reaction of NADH with 12-tungstocobaltate(III) has been studied over the range 5.07 ≤ 10⁴ [NADH] ≤ 15.22 mol dm^-3, 7.0 ≤ pH ≤ 8.0 and 20 ≤ t ≤ 35 ^oC in aqueous medium. The electron transfer reaction showed first-order dependence each in [NADH]_T and [12-tungstocobaltate(III)]_T. The products of the reaction were found to be NAD⁺ and 12-tungstocobaltate(II). The activation parameters ΔH^# (kJ mol^-1) and ΔS^# (JK^-1mol^-1) of the electron transfer reactions were found to be 64.4±1.8 and -48.86±6.0. Negative value of ΔS^# is an indicative of an ordered transition state for the electron transfer reaction.