Photocatalytic Generation of Hydrogen Using Dinuclear π-Extended Porphyrin-Platinum Compounds

A series of heterodinuclear complexes, M-1-PtX₂ with M=H₂ , Zn, Cu or Co, X=Cl or I, has been synthesized, and first results on their photocatalytic activity in visible light driven proton reduction are presented. The compounds are based on a phenanthroline extended meso-tetramesityl-porphyrin bridging ligand (H₂ -1) incorporating different metal centers in the porphyrin moiety, which functions as a photosensitizer unit. The well-known catalytically active PtX₂ fragment resides in the phenanthroline coordination pocket. The synthesis was optimized, compounds were fully characterized and a solid-state structure could be obtained for selected complexes. Photocatalytic studies in acetonitrile/water mixtures using triethylamine as sacrificial electron donor showed that the activity of the complexes depends strongly on the metal center in the porphyrin moiety as well as the halogen ions bound at the platinum(II) center.