PROPERTIES OF RUTHENIUM BIPYRIDYL DIMERS BRIDGED BY DISUBSTITUTED ANTHRAQUINONES

Ru(bpy)2Cl2 reacts with 1,4-DHAQ, 1,5-DHAQ and 1,4-AHAQ to form dinuclear complexes. Its reaction with 1,8-DHAQ produces a monomer. Both 1,4-DHAQ and 1,4-AHAQ produce stable mixed valence complexes when oxidized, and show greater separation of ruthenium oxidation potentials than the 1,5-DHAQ complex. K(c) has been calculated to be 3.7 x 10(4) for the 1,4-DHAQ complex, 1.3 x 10(8) for the 1,4-AHAQ complex, and 3.4 x 10(2) for the 1,5-DHAQ complex. In all cases E1/2(1) for the dimers is less positive than E1/2(1) for the monomeric 1,8-DHAQ complex. Spectral studies of the mixed valence states showed IT bands at approximately 2000 nm in acetonitrile for the 1,4-DHAQ complex and at 1368 nm in acetonitrile for the 1,4-AHAQ complex. Solvent dependence was observed for the IT band for the latter complex. The experimental evidence indicates that the three dinuclear complexes may be class II mixed valence dimers.