A cobalt–NHC complex as an improved catalyst for photochemical hydrogen evolution from water

A macrocyclic N-heterocyclic carbene (NHC)-cobalt complex was found to act as an improved H2-evolving catalyst in a [Ru(bpy)3](2+)-sensitized photosystem using methylviologen as a redox acceptor (MV(2+) + e(-) → MV(+)˙, MV(2+) = N,N'-dimethyl-4,4'-bipyridinium), which provides a driving force of only 150 meV for H2 evolution at pH 5.0.