The optical absorption and luminescence spectra, the electrochemical behavior, and the X-ray crystal structure of a series of three heteroleptic Ru(II) complexes in comparison to [Ru(bipy) 3 ] 2 + are reported. The complexes examined are of the type [Ru(bipy) 2 (bipy%)](PF 6 ) 2 with bipy =2,2%-bipyridine and bipy%= 5,5%-diamino-2,2%-bipyridine (4), diethyl-2,2%-bipyridine-5,5%-dicarboxylate (5) or 5,5%-bis(ethoxycarbonylamino)-2,2%-bipyridine (6). Absorption bands and redox waves are fully assigned. The position of bands or half-wave potentials can be correlated with the electron-withdrawing/donating properties of the bipy% ligand. The relative emission intensities of complexes with 4 and 6 can be modulated through the hydrogen-bonding capabilities of the solvent (MeOH and H 2 O). The cyclic voltammograms between + 1.5 and -2.2 V show a reversible metal-oxidation wave and two to four reduction waves, attributed to successive reductions of the different ligands. Ligand 4 can only be oxidized. Correlations between spectroscopical and electrochemical data give a linear relation for hw max abs , hw max em versus DE 1/2 . A comparison with complexes with the analogous 4,4%-disubstituted-2,2%-bipyridine ligands reveals pronounced differences in the position of the MLCT-absorption and emission bands due to the 5-or 4-position of the substituent.