High turnover photocatalytic hydrogen formation with an Fe(III) N-heterocyclic carbene photosensitiser.

Herein we report the first high turnover photocatalytic hydrogen formation reaction based on an earth-abundant Fe III -NHC photosensitiser. The reaction occurs via reductive quenching of the 2 LMCT excited state that can be directly excited with green light and employs either Pt-colloids or [Co(dmgH) 2 pyCl] as proton reduction catalysts and [HNEt 3 ][BF 4 ] and triethanolamine/triethylamine as proton and electron donors. The outstanding photostability of the Fe III -NHC complex enables turnover numbers >1000 without degradation.