New research published last week in Nature Chemistry demonstrates a novel highly oxidative Ir(iii) photocatalyst, [Ir(ttpy)(pq)Cl]PF6 , which is phototoxic towards both normoxic and hypoxic cancer cells. The research was performed in collaboration between the groups of Peter Sadler (Chemistry, Warwick, UK), Martin Paterson (Engineering and Physical Sciences, Heriot-Watt, UK), Gilles Gasser (Inorganic Chemical Biology, Chimie Paris Tech, France), Hui Chao (Chemistry, Sun Yat-sen, China), Guy Clarkson (Chemistry, Warwick, UK), Pingyu Zhang (Chemistry and Environmental Engineering, Shenzhen, China), Olivier Blacque (Chemistry, Zurich, Switzerland), and the Warwick Centre for Ultrafast Spectroscopy.

The research showed how the photocatayst under study caused a high turn over number and turn over frequency of the oxidation of 1,4-dihydronicotinamide adenine dinucleotide (NADH) - an important coenzyme in living cells - causing cell death in cancer cells. WCUS played a role in this research by providing in vitro time-resolved phosphorescence studies of the photocatalyst under hypoxia and normoxia conditions. These studies showed lifetimes of 743.7/1,390.3ns for air/N₂ in acetonitrile and 330.8/382.3ns for air/N₂ in buffered saline solution. Singlet oxygen quantum yields were found to be 0.71 in acetonitrile and 0.11 in buffered saline. These long lifetimes and large yields of singlet oxygen contribute to the very effective anti-cancer action of the photocatalyst.