Aryl-modified ruthenium bis(terpyridine) complexes: Quantum yield of 1O2 generation and photocleavage on DNA

Six Ru(II)bis(tpy) (tpy = 2,2′:6′,2″-terpyridine) complexes, functionalized with one or two 2-naphthyl, 1-pyrenyl, or 9-anthracenyl at 4′-position of terpyridine respectively, were investigated with emphasis on their 1O2 generation quantum yields and photocleavage capabilities on DNA. For naphthyl and pyrenyl modified complexes, the lowest energy excited state is 3MLCT, and therefore they behave very similarly to the parent complex, [Ru(tpy)2]2+, having very low 1O2 generation quantum yields. In contrast, for anthracenyl modified complexes, the lowest energy excited state is anthracene-localized 3ππ* state, as a result, they exhibit extremely high 1O2 generation quantum yields (0.96 and 0.71 for bis- and mono-substituted complexes, respectively) and potent photodamage abilities on calf thymus DNA, suggesting their promising applications in 1O2-involved processes, such as DNA photocleavage.