Spectroelectrochemical Study of Mediators I. Bipyridylium Salts and Their Electron Transfer Rates to Cytochrome c

Abstract

Abstract In many potentiometric titrations of biological electron transfer components, mediators are often employed to act as electron transfer mediators between the components and the potentiometric electrode. Certain mediators have been employed recently as electrogenerated titrants of components in coulometric titrations, particularly in some spectroelectrochemical studies. In this paper, the optical and electrochemical characteristics of some bipyridylium salts are examined as mediator‐titrants. These salts (dications) undergo a reversible one electron reduction to the radical cation which can be a good reductant. Spectroelectrochemistry has also been applied to the evaluation of the rate of electron transfer from the radical to oxidized cytochrome c. The results reported herein are a part of our interest in evaluating the electron transfer properties of heme proteins found in the mammalian respiratory system.