275ChemInform Abstract The properties of the bimetallic complexes, where the only variation is the energy of the bridging ligand's π system, are studied. The lowest energy electronic absorption band is assigned as a MLCT process, where the acceptor state is localized primarily on the bridging ligand. Unlike the Ru complexes analogous to (IVa) and (IVb), the bimetallic Re containing complexes show no luminescence. The complexes (III) and (IV) display two reductions and one oxidation. The second reduction may be due to a metal-centered Re(I)/Re(0) process for (IIIa) and ligand centered for (IIIb) and (IIIc). A third reduction is observed for (IVa) and (IVb). A comparison with the analogous Ru complexes show that the Re(CO)3Cl moiety is more effective in stabilizing the reduced forms of the heterocyclic ligands than (Ru(bipy)2)2+ (yields not given).

The properties of the bimetallic complexes, where the only variation is the energy of the bridging ligand's π system, are studied.