Bipyrimidine-bridged rhenium(I)/rhenium(I) and ruthenium(II)/rhenium(I) complexes. Synthesis, electronic absorption and emission spectra

Abstract

The binuclear complexes [Cl(OC) 3Re I(bipym)Re I(CO) 3Cl] (bipym=2,2′-bipyrimidine), [(bipy) 2Ru II(bipym)Re I(CO) 3Cl](PF 6) 2 (bipy=2,2′-bipyridine) and their mononuclear component [Re(bipym)(CO) 3Cl] were prepared. The electronic absorption spectra of these complexes display low-energy Re(I) →π*(bipym) and Ru(II)→π*(bipym) charge transfer (CT) bands. While [Re(bipym)(CO) 3Cl] shows a strong emission from its lowest CT state, the dimer [Cl(OC) 3Re(bipym)Re(CO) 3Cl] is not luminescent. The cation [(bipy) 2Ru(bipym)Re(CO) 3Cl] 2+ emits from the lowest-energy Ru→bipym CT state. The emission behavior of the binuclear complexes is described in terms of intramolecular excited state electron or energy transfer.