ELECTRONIC-STRUCTURE OF HETERODINUCLEAR COMPLEXES (BPY)2RU(II)-(MU-BPYM)MLN, BPY = 2,2'-BIPYRIDINE, BPYM = 2,2'-BIPYRIMIDINE, MLN = +CU(PPH3)2, MO(CO)4, RE(CO)3CL

The heterodinuclear title complexes were studied by cyclic voltammetry, absorption spectroscopy and by ESR of their singly reduced forms. Comparison with the homodinuclear analogues reveals that the metal-centered occupied d orbitals show relatively little change on coordination of a second metal (weak interaction) whereas the bpym-centered lowest unoccupied MOs pi*1 and pi*2 are stabilized by effects coming from both metal fragments. Combinations of metal fragments with different pi donor/sigma acceptor characteristics give rise to variable charge transfer energies for major transitions d(Ru) --> pi*1, d(M) --> pi*1, d(Ru) --> pi*2, d(M) --> pi*2; the appearance of spectra is further determined by different widths and intensities of individual bands and by solvent dependence.