A new ruthenium (II) complex, [Ru(terpy-Ph-PO 3 H 2 ) 2 ] 2 + (where terpy-Ph-PO 3 H 2 = 4 -(p-phosphonophenyl)-2,2 :6,2 -terpyridine), has been synthesized for the photosensitization of anatase TiO 2 towards the visible spectrum. The sensitizer is able to establish strong anchorage on the surface of the TiO 2 over a wide pH range. Under broad band visible irradiation, the sensitizer can inject electrons into the conduction band of the semiconductor. Using I - as electron donor, the TiO 2 -[Ru(terpy-Ph-PO 3 H 2 ) 2 ] 2 + system is able to mediate degradation of CCl 4 in aqueous medium.