Photoinduced water oxidation using dendrimeric Ru(II) complexes as photosensitizers

Following bio-inspired guidelines, solar-powered water oxidation can be exploited for hydrogen generation by direct photocatalytic water splitting. This reaction poses some formidable challenges at the interface of oxidation catalysis and photochemistry. Molecular innovation is expected to provide a decisive lead in the field of artificial photosynthesis. Key achievements include the discovery of novel transition metal catalysts, exhibiting oxygen-evolving activity upon multi-electron oxidation and the design of antenna-like sensitizers. The thermodynamic and photophysical requirements of the system are discussed herein. A successful combination is obtained with polynuclear dendrimeric Ru(II) polypyridine sensitizers, activating colloidal IrO2 nanoparticles or a tetra-ruthenate polyoxometalate catalyst. In this latter case, an unprecedented quantum yield up to 30% is achieved, which holds great promise for the up-grade to functional materials and practical technology.