Trinuclear Ru(II)‐Ru(II)‐Ru(II) Complexes as Efficient Photosensitizers for Potent Aqueous Singlet Oxygen Generation and NADH Photo‐Oxidation

Here, two new trinuclear polypyridyl Ru(II) complexes [(DIP) 6 Ru 3 L] 6+ ( D‐3Ru ) and [(Phen) 6 Ru 3 L] 6+ ( P‐3Ru ) (L = 4,4′‐bis(1H‐imidazo[4,5‐f][1,10]phenanthrolin‐2‐yl)−2,2′‐bipyridine) as new photosensitizers were developed and fully characterized by 1 H/ 13 C NMR, HRMS and elemental analysis. The electrochemical cyclic voltammetry study and density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations were determined to investigate the electronic properties. Both complexes showed strong phosphorescence in various solutions, with emission lifetimes of 305 ns ( D‐3Ru ) and 291 ns ( P‐3Ru ). D‐3Ru generated high amount of singlet oxygen under low‐power light exposure (blue (465 nm) and red (650 nm) LED lights), giving singlet oxygen generation efficiency 3.3‐fold (acetonitrile) and 9.7‐fold (PBS) higher than that of [Ru(bpy) 3 ]Cl 2 , giving the singlet oxygen quantum yields of 0.47 (acetonitrile) and 0.88 (PBS). Such potency was also confirmed by oxidation of 1,5‐dihydroxynaphthalene (DHN). D‐3Ru also generated superoxide and hydroxyl radicals with high reaction efficiency under blue LED light irradiation and could fully oxidize coenzyme NADH with a turnover frequency (TOF) value high as 5820 h −1 . The current work provides new example of trinuclear Ru(II) complexes as competent type I and II photosensitizer candidates.