A linear relation is predicted to exist between frequencies of charge-transfer bands of a series of transition metal complexes with different ligands and their oxidation potentials corrected for the electron affinities of acceptor ligands. The relation is proved to hold for the tris(2,2′-bipyridine), tris(4,4′-dimethyl-2,2′-bipyridine) and tris(5,5′-dimethyl-2,2′-bipyridine) complexes of iron(II), ruthenium(II), osmium(II), cobalt(I) and chromium(II). On the basis of the fact that the electronic configuration of any one of these complexes and its one-electron oxidation product differs by one in the number of electrons in the t2g-orbitals, an empirical rule is obtained: When a metal t2g-electron is removed by electrochemical oxidation of a tris(2,2′-bipyridine) complex of a transition metal, the oxidation half-wave potential is shifted to a more negative potential on methyls substitution of ligand bipyridines in the order, bipyridine <5,5′-dimethylbipyridine <4,4′-dimethylbipyridine. Combined with the conclusion of Part I9, the present findings suggest a new electrochemical method for determination of the electronic configuration of tris(2,2′-bipyridine) complexes of transition metals.