Redox thermodynamics of surface-bound reactants: Illustrative behavior of cobalt(III)/(II) macrobicyclic “cage” complexes

Abstract

Abstract : The electrochemistry of surface-bound couples is an area of considerable current interest. In addition to their potential applications in electrocatalysis, such couples that involve mechanistically uncomplicated one-electron transfer offer opportunities for studying several fundamental aspects of heterogeneous electron-transfer processes. For example, the interpretation of electrochemical rate parameters for surface-attached reactants is especially straightforward, since these provide direct information on the energetics of the elementary electron-transfer step. The comparison between redox thermodynamics of a given redox couple in solution and in the surface-bound state are expected to yield useful insights into the differences in the solvating environment between the interfacial region and the bulk solution. Bulk solution and surface thermodynamic behavior for two Co(III)/(II) redox couples adsorbed by different means is presented here in order to illustrate the virtues of such analyses for simple electrode reactions.