Photogeneration of hydrogen from water using an integrated system based on TiO2 and Platinum(II) diimine dithiolate sensitizers

Two platinum(II) diimine dithiolate complexes, Pt(dcbpy)(met) (1) and Pt(dcbpy)(bdt) (2) (dcbpy = 4,4'-dicarboxyl-2,2'-bipyridine; met = cis-1,2-dicarbomethoxyethylene-1,2-dithiolate; bdt = 1,2-benzenedithiolate) were used as sensitizers for platinized TiO2 (TiO2/Pt), and systems composed of 1/TiO2/Pt and 2/TiO2/Pt were found to generate hydrogen from aqueous protons and a sacrificial electron donor, triethanolamine (TEOA), under visible light irradiation. Turnover numbers reached 84 after 95 h of irradiation for the first system and 72 after 73 h of irradiation for the second. Additional photolyses with light of wavelength longer than 455 nm showed that the systems are photostable with no loss of activity. Parallel experiments with Pt(diimine)(met) and Pt(diimine)(bdt) complexes that do not bind to TiO2 reveal that attachment of the sensitizer to TiO2 is essential for effective hydrogen generation.