Covalent Modification of Carbon Surfaces by Direct and Redox Catalysed Oxidation of Carboxylates in Acetonitrile – Concepts and Mechanisms

Electrografting is a relevant process that allows getting modified electrodes where organic molecules are covalently bonded to the electrode surface. The modification is typically performed using electrochemical reactions, where the transient passage by free radicals allows the formation of covalent bonds with the electrode surface. These intermediaries are generated over a wide potential window, and they are commonly prone to a second electron transfer (oxidation or reduction). Thus, this reaction competes with the surface reactions, slowing down the formation of films on the electrode. In the case of carboxylate oxidation, these competitive processes have been minimized by using a redox-catalysed process which occurs at low oxidation potentials. The rate at which modifications procedures occur is relevant in the sense that they determine the properties of the polymeric films covalently attached to the electrode surfaces. Therefore, this review focuses on the main aspects of the direct and redox-catalysed oxidation of carboxylates as a tool for the covalent modification of the surface of different carbon electrodes.