Concerning electrochemically reversible [Ru(III)]/[Ru(II)] redox couples of the substituted bis(eta (3)-polypyrazolylborato)-ruthenium(II) complexes [Ru(L-1)(L-2)], two polypyrazolylborate ligands, L-1 and L-2, were independently exerted on the oxidation half-wave potentials (E-1/2) of the couples. Relative contributions DeltaE(L) of the respective polypyrazolylborates to the E-1/2 values were evaluated.