The double-well cage effect for a ferrocyanide/dimethylviologen ion pair in viscous media: kinetic and thermodynamic probings through the CT transition band

The ion pair recombination kinetics following the electric field induced predissociation, and the ion pair formation kinetics following direct mixing, were studied by temperature jump and stopped-flow techniques, respectively, in viscous water/glycerol mixtures. The rate constant detected for the recombination process was virtually independent of the glycerol concentration within 65–80% v/v, while direct mixing revealed viscosity-sensitive dispersive kinetics. Thermodynamic parameters for the ion pair formation pseudo-equilibrium under the high viscosity conditions were also determined, which, together with the kinetic data, point to at least a two-step mechanism for the ion pair formation.