Efficient grafting of redox-active ferrocene polymers from α,ω-diiodoalkanes at cathodically charged glassy carbon

Abstract

α,ω-Dihaloalkanes, when cathodically reduced at glassy carbon (GC), can be immobilized at the electrode surface. The present contribution focuses on the reduction of 1,8-diiodooctane, as model dihalo-substrate, in an aprotic organic solvent containing tetraalkylammonium salts as electrolyte. It is expected that these compounds in contact with GC, polarized at potentials more negative than −1.7 V versus Ag/AgCl, partly lead to monoiodoalkyl chain immobilization onto carbon. The process corresponds to the cathodic charge of graphitized and fullerenized zones present in carbon followed by a displacement reaction (analogous to a nucleophilic attack) towards pending C–I functions. This mode of grafting is then applied to the reaction of negatively charged carbon with bis-(ω-iodoalkyl)ferrocenes. Ferrocene is then used as an efficient redox probe. This study aims to point out the formation of a chemically grafted redox polymer at carbon electrodes that permits one to quantify the level of immobilized alkyl chains according to their chain length. Coverage levels were found to be high, and surface concentrations of ferrocene currently >10−8 mol cm−2 were reached. Ferrocene layers deposited onto carbon were found to be chemically and electrochemically stable and expected to be suitable for efficient electricity storage. .