Raman characterization of charge-transfer transitions in ligand-bridged binuclear polypyridyl complexes of ruthenium(II)

Abstract

In the ligand-bridged complexes [(bipy)₂Ru(dpp)Ru(biq)₂]⁴⁺ and [(biq)₂Ru(dpp)Ru(biq)₂]⁴⁺[dpp = 2,3-bis(2′-pyridyl)pyrazine, bipy = 2,2′-bipyridine and biq = 2,2′-biquinoline], the photophysical and redox properties do not allow differentiation of the low-energy charge-transfer transitions Ru → biq and Ru → dpp. Based on the selective resonance enhancement of the intensities of the Raman bands of the ligand biq by excitation within the lowest-energy absorption band, the lowest excited states in the dinuclear complexes have been assigned unambiguously to Ru → biq charge transfer.