Structure and solvent effect on the photostability of indolenine cyanine dyes

The structure and solvent effect on the photostability of a series of indolenine cyanine dyes have been investigated. It was found that the photostability did not increase with the increase of the central conjugated chain length and/or substituent groups on the heterocyclic ring. Using UV spectra data, we have found that the photostability of indolenine cyanine dyes in solution increased with increase of the E-T (30) values of solvents. The rate of singlet oxygen formation, and beta values in different solvents sensitized by the dye alone were measured using fluorescence spectra. Absolute photooxidation rate constants (k(r)) are calculated, based on the determined beta values and the decay rate of singlet oxygen (k(d)). All these results well agreed with those obtained from UV spectra. (C) 1999 Elsevier Science Ltd. All rights reserved.