Photosensitization of a colloidal TiO2 semiconductor system with hypocrellin B

Several novel triad compounds with fluorescence were synthesized, in which aromatic sulfur components (such as disulfide, 9H-thioxanthen-9-one and thianthrene) were used as "bridges". The fluorescence lifetimes of these compounds in various solvents have been measured by the single-photon counting technique. The characteristic longer wavelength emission of these compounds was observed, which may result from the formation of intramolecular exciplex or ICT excited state. The photoinduced electron transfer (PET) phenomenon was observed for the disulfide series compounds. When PET occurs, the fluorescence of compound is quenched.