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 FeIII-NHC photosensitiser. The reaction occurs via reductive quenching of the 2LMCT excited state that can be directly excited with green light and employs either Pt-colloids or [Co(dmgH)2pyCl] as proton reduction catalysts and [HNEt3][BF4] and triethanolamine/triethylamine as proton and electron donors. The outstanding photostability of the FeIII-NHC complex enables turnover numbers >1000 without degradation.