Copper-Based Photosensitisers in Water Reduction: A More Efficient In Situ Formed System and Improved Mechanistic Understanding.

The reduction of water has been achieved through a non-noble-metal-based homogeneous catalyst system that is formed in situ. Optimisation of the ligand quantities increased catalyst turnover numbers compared to preformed complexes. Mechanistic studies confirm a heteroleptic Cu complex as the active photosensitiser (PS) and an in situ formed Fe-phosphido dimer complex as the water reduction catalyst. The in situ method has been used to screen a range of ligands for the active PS, which has led to the identification a number of structural features important to longevity and performance.