Catechol as an efficient anchoring group for attachment of ruthenium-polypyridine photosensitisers to solar cells based on nanocrystalline TiO2 films

The Ru(II)-polypyridyl complexes [Ru(H2L)(terpy)] [PF6](2) (1) and [Bu4N] [Ru(H2L)(NCS)(3)] (2) (H2L = 4'-(3,4-dihydroxyphenyl)2,2':6'2-terpyridine), in which H2L is coordinated as a terpyridyl fragment with a catechol site pendant from the C4' position, adhere effectively to nanocrystalline TiO2 (anatase) surfaces via the pendant catechol group; incident photon-to-current conversion efficiency values of up to 50% were obtained in their photocurrent action spectra, suggesting that the catechol unit may be a convenient and effective anchoring group for attaching dyes to TiO2-based photovoltaic cells.