Solvent effect on the electrochemical oxidation of N,N,N′,N′-tetramethyl-1,4-phenylenediamine. New insights into the correlation of electron transfer kinetics with dynamic solvent effects

Electrochemical oxidation of N,N,N',N'-tetramethyl-1,4-phenylenediamine (TMPD) to its cation radical (TMPD center dot+) and dication (TMPD++) in various nonaqueous solvents was studied using the cyclic voltammetry technique on a glassy carbon electrode. The variation of the half-wave potentials (E-1/2) with the physical properties of the solvents was interpreted using multi-parametric correlation. It is shown that polarity-polarizability index, viscosity and longitudinal relaxation of solvents play an undeniable role in the E-1/2 value. The electron transfer rate constants were simulated and analyzed using the MLR regression method to separate the effect of longitudinal relaxation time from other effective parameters according to the Marcus theory. Finally, a new correlation method was developed which involve solvent's Pekar factor, longitudinal and Debye relaxation time, viscosity and relative permittivity. The computational method was used for calculating the standard of the Gibbs free energy of solvation and oxidation process. (C) 2018 Elsevier B.V. All rights reserved.