Ru-Pt and Ru-Pd heterobimetallic complexes based on a new ligand with two distinct chelate sites

A new ligand p-[N-2-(2′-pyridyl)benzimidazolyl]-[N-2-(2′- pyridyl)indolyl]-benzene (L1) has been synthesized and fully characterized. L1 has two distinct chelating sites: one N,N-chelate site and one N,C-chelate site. This ligand has been found to be very effective in selective binding to two different metal ions. Two new heterobimetallic complexes Ru-Pt and Ru-Pd using L1 as the bridging ligand have been successfully synthesized and fully characterized. To understand the mutual influence of the two metal centers on electronic and photophysical properties, the corresponding monometallic Ru(ii), Pt(ii) and Pd(ii) compounds have also been synthesized and investigated. All Ru(ii)-containing complexes have been found to be luminescent. Electronic communication between the two different metal centers in the heterobimetallic compounds was found to be weak. The Pt(ii) moiety appears to enhance the phosphorescent efficiency of the Ru(ii) unit while the Pd(ii) analogue has little influence.