Electron transfer reactions between transition metal complexes in micellar solutions

Abstract

We report a systematic investigation of the influence of anionic micelles (SDS) on the kinetics of diffusion controlled outer sphere electron transfer reactions between transition metal complexes. — The micelles interact with the reactants through electrostatic repulsion (e. g. IrCl₆²) or attraction which can cause ion association (e. g. Os(dipy)) as well as through hydrophobic forces (e. g. Fe(phen)₂(CN)₂⁰). The rate constantsk_ETof these reactions range in the order of 10¹⁰M⁻¹s⁻¹in aqueous solution and are decreased by more than four orders of magnitude if these forces superimpose. — By variation of the SDS concentrations and the ionic strengths electrostatic influences were largely eliminated. It was thus possible to establish a hydrophobic barrier in electron transfer reactions between complexes which are solubilized in the hydrophobic core of the micelles and substitution inert complexes in the bulk solution.