A photosensitizer complex of formula (I) MLX2 in which M is a transition metal selected from ruthenium, osmium, iron, rhenium and technetium; each X is a co-ligand independently selected from NCS−, Cl−, Br−, I−, CN−, H2O; pyridine unsubstituted or substituted by at least one group selected from vinyl, primary, secondary or tertiary amine, OH and C1-30 alky, preferably NSC− and CN−. L is a tetradentate polypyridine ligand, carrying at least one carboxylic, phosphoric acid or a chelating group and one substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, substituted or unsubstituted alkylamide group having 2 to 30 carbon atoms or substituted or unsubstituted aralkyl group having 7 to 50 carbon atoms. A dye-sensitized electrode includes a substrate having an electrically conductive surface, an oxide semiconductor film formed thereon, and the above sensitizer of formula (I) as specified above, supported on the film.