Photophysical Properties and Singlet Oxygen Production by Ruthenium(II) Complexes of Benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine: Spectroscopic and TD-DFT Study

The photophysical properties of a series of Ru-II complexes containing benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn) as a ligand are reported. Transient absorption spectroscopy studies indicate that, in contrast to related Ru(dppz) complexes (dppz = dipyrido[3,2-a:2',3'-c]phenazine), the excited state of all the dppn systems is a long-lived pi pi* triplet state. Computational studies (DFT and TD-DFT) confirm that the excited state is based on the dppn ligand. Near-infrared luminescence studies reveal that the complexes are efficient singlet oxygen sensitizers with yields of 70-83%.