A study of dimethylferrocene diffusion and electrode kinetics using microelectrode voltammetry in poly(ethylene glycol) solvent

The heterogeneous electron transfer rate constant (k(s)) of dimethylferroce ne (DMFc) was estimated using cyclic voltammetric peak potential separation s taken typically in a mixed diffusion geometry regime in a polyelectrolyte , and the diffusion coefficient (D) of DMFc was obtained using a steady-sta te voltammogram. The heterogeneous electron transfer rate constant and diff usion coefficient are both smaller by about 100-fold in the polymeric solve nt than in the monomeric solvent. The results are in agreement with the dif ference of longitudinal dielectric relaxation time (tau(L)) in the two kind s of solvents, poly(ethylene glycol) (PEG) and CH3CN, indicating that k(s) varies inversely with tau(L); k(s), is proportional to D of DMFc. Both D an d k(s) of DMFc in PEG containing different supporting electrolytes and at d ifferent temperatures have been estimated. These results show that D and k( s) of DMFc increase with increasing temperature in the polyelectrolyte, whe reas they vary only slightly with changing the supporting electrolyte.