New insights into the electrochemical oxidation of aniline-dimers in non-aqueous solutions, kinetic parameters obtained by Koutecký-Levich method

The electrochemical oxidation of aniline dimers (4-aminodiphenylamine and 2-aminodiphenylamine) was studied at a glassy carbon electrode in hydrophobic and hydrophilic aprotic solvents and also in ethanol as a neutral amphiprotic solvent. In these solvents, both isomers, show the proton coupled electron transfer mechanism. A linear relationship between the redox potential of these molecules and the donor number of the studied solvents has been found. Our data show that both dynamics of solvent reorientation and the structure of aniline dimer, have a role in the heterogeneous electron transfer rate constant of 4-aminodiphenylamine and 2-aminodiphenylamine. A near linear relationship between the heterogeneous standard rate constant (log k s ) and the longitudinal relaxation time (log τ L ) of the solvents has been found. Furthermore, the mechanism of oxidation of aniline dimers has also been investigated using the rotating disk electrode technique, and the parameters such as heterogeneous rate constant and diffusion coefficient have been determined from Koutecky-Levich plot.