Visible-light sensitized photocatalytic hydrogen generation using a dual emissive heterodinuclear cyclometalated iridium(III)/ruthenium(II) complex

The synthesis, spectroscopic and electrochemical properties of the heterodinuclear iridium(III)/ruthenium(II) photosensitizer Ir-BBI-Ru, i.e. [(ppy)2Ir-(tmBBI)-Ru(tbbpy)2][PF6] (ppy = 2-phenylpyridine; tmBBI = 4,4’,5,5’-tetramethyl-2,2’-bibenzimidazole; tbbpy = 4,4’-di-tert-butyl-2,2’-bipyridine) are presented. Its absorbance lies well within the visible light spectrum, showing absorption features typical for dinuclear ruthenium(II) bibenzimidazole complexes. The complex exhibits characteristic emission properties of both metal center, indicative of an incomplete energy transfer. The application of Ir-BBI-Ru as visible-light absorbing photosensitizer in the field of photocatalytic water reduction is demonstrated by considerable hydrogen generation with a Co(II) catalyst and triethanol amine as sacrificial donor.