Cyclic Voltammetric Study of Cobalt Poly-4-t-butylpyridine Ligand Complexes on Glassy Carbon Electrodes: Electrolyte Dependence and Mechanistic Considerations

Polypyridyl complexes of Co(II/III) have been gaining prominence as potential replacements for I–/I3– as mediators in dye sensitized solar cells. In that regard, homoleptic pseudo-octahedral complexes of 4,4′-di-t-butyl-2,2′-bipyridine, [Co(DTB)3]2+/3+, and 4,4′,4″-tri-t-butyl-2,2′:6,2″-terpyridine, [Co(TTT)2]2+/3+, have been of particular interest. These complexes show extreme electrode surface and electrolyte dependent electrochemical behavior. Below, we report on the cyclic voltammetric behavior of these two complexes at glassy carbon electrodes in two different electrolytes. The electrochemical data suggests that the Co(II/III) electron transfer is significantly nonadiabatic, especially for [Co(DTB)3]2+/3+ in LiClO4 electrolyte.