Kinetics and thermodynamics of redox processes in room temperature ionic liquids: The use of voltammetry and the disproportionation of radical cations of N, N -dimethyl- p -phenylenediamine in 1-butyl-3-methylimidazolium tetrafluoroborate

The voltammetry of N,N-dimethyl-p-phenylenediamine, DMPD, in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate, [C4mim][BF4] is studied by means of microdisc voltammetry over a wide range of voltage scan rates incorporating the transition from linear to convergent diffusion. Two voltammetric waves were recorded corresponding to the formation of the radical cation DMPD+ and dication DMPD 2+; both are stable on the voltammetric time scale. Double potential step chronoamperometry was used to measure the diffusion coefficients of DMPD and DMPD+. These values, in conjunction with simulations of the cyclic voltammetry, permit the inference of the equilibrium constant and kinetics for the comproportionation of DMPD and DMPD2+ forming DMPD+ to be studied. © 2009 American Chemical Society.