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.

Graphical abstractRu(II) complexes with the polypiridinic quinone substituted acceptor ligand [3,2-a:2′,3′-c]-benzo[3,4]-phenazine-11,16-quinone (Nqphen) was synthesized and characterized. Theoretical study was performed to complement the spectroscopic and electrochemical characterization.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New Ru(II) complexes with Nqphen, a quinone derivatized polypiridinic ligand. ► The properties of the complexes were governed by the behavior of the ligand Nqphen. ► The presence of the quinonic group on Nqphen gives direction to electron transfer. ► The theoretical study results agree with the experimental data for the complexes.