Photocatalytic watersplitting can be utilised with molecular photocatalysts. Ruthenium complexes with related tpphz type ligands play an important role within this field. [1,2] However, up to now no knowledge based successful design concept for this type of catalysts could be developed.  Through a series of model catalysts we now can differentiate between several important structural aspects influencing the photocatalytic activity.
The depicted catalyst can be tuned by influencing the photochemical properties of the ruthenium photocentre by changing substituents R1. The electron transfer between photocentre and catalytic centre Me is influenced by R2. Whereas the stability and attainable turn over numbers are influenced by the nature of Me and the coordinated ligands L.