Synthesis, characterization and theoretical studies of ruthenium(II) complexes with the quinone functionalized polypyridine ligand, Nqphen

The synthesis, spectral characterization, electrochemical properties and TDDFT theoretical study of the complexes [Ru(dmbpy)2(Nqphen)](PF6)2 (2a) and [Ru(tmbpy)2(Nqphen)](PF6)2 (2b) is reported. Nqphen is the quinone substituted acceptor ligand [3,2-a:2′,3′-c]-benzo[3,4]-phenazine-11,16-quinone, dmbpy is 4,4′-dimethyl-2,2′-bipyridine and tmbpy is 4,4′,5,5′-tetramethyl-2,2′-bipyridine. No major difference is observed in the spectroscopic and electrochemical properties of the complexes, reflecting that the presence of the electron withdrawing Nqphen ligand governs their behavior. Molecular orbital calculations show that the LUMO is centered on the quinonic fragment of Nqphen, while the HOMO orbital has mainly a metal character. The calculations results at TDFT level were consistent with the experimental data, and permitted their detailed interpretation.