The redox potentials of diimine mixed-ligand ruthenium complexes were remeasured under identical conditions, The Hubbard Hamiltonian formalism including solvation contribution was used for the enumeration of the energies of all possible configurations which might come into account in the redox series of these complexes. The comparison of the experimental and calculated half-wave potential sequences based on theoretically calculated electron affinities, combined with analysis of spectra of reduction products, enabled the assignment of electron localization along the redox series.