Photophysical properties of the Corrole photosensitizers

The photophysical properties of a series of hydroxyl Corroles, Corrole-F, Corrole-Cl, Corrole-Br, Corrole-I and Corrole-2I, have been investigated by steady-state and time-resolved transient spectroscopy. The absorption spectra show a strong peak around 420 nm corresponding to B band and several weak Q absorption bands between 450 nm and 650 nm, exhibiting much stronger Q band absorption than that of porphyrin. The absorptions of these Corroles increase with the atom weight and the number of halogen atoms. All samples show similar fluorescence characteristics of an emission peak at 650 nm. The fluorescence intensities significantly decrease with the atom weight and the number of halogen atoms. The fluorescence quantum yield of Corrole-I is 0.947%, which is larger than that of Corrole-2I (0.381%). The fluorescence dynamics of the hydroxyl Corroles shows that both the fluorescence lifetime and the intersystem-crossing transition time of these Corroles decrease sharply with the increase of the atom weight and the number of halogen atoms, which may lead to the increase of the triplet state quantum yield. The heavy-atom effect on active oxygen of PDT has also been discussed by the end of this paper.