New dyes for solar cells based on nanostructured semiconducting metal oxides Synthesis and characterization of ruthenium(II) complexes with thiol-substituted ligands

Five azo-dyes: 4-phenylazo-phenol, 4-phenylazo-benzeneamine, 4-phenylazo-benzenethiol, 4-phenylazo-benzoic acid, and 4-phenylazo-pyridine have been prepd. and used as a "test kit" for rapid screening of functional group affinity to metal oxides. The dyes with carboxylic acid and thiol gave colored electrodes both for ZnO and TiO2 whereas the pyridine had affinity only for TiO2. Also, cis-ruthenium-bis[2,2'-bipyridine]-bis[4-thiopyridine], cis-ruthenium-bis[2,2'-bipyridine]-bis[4-pyridinethiolate], cis-ruthenium-bis[2,2'-bipyridine]-bis[4-carboxypyridine], and cis-ruthenium-bis[2,2'-bipyridine]-[4,4'-dicarboxy-2,2'-bipyridine] have been prepd. and adsorbed onto ZnO. In this preliminary photoelectrochem. study, all these ruthenium-bipyridine dyes show electron injection.