Photodynamic potentialities of some phenothiazine derivatives

Summary The quantum yields of fluorescence and phosphorescence and the triplet lifetimes were determined for 29 phenothiazine derivatives; the_p values are varying from 0.2 to 1. The irradiation of phenothiazine derivatives in aerated solutions yields from the triplet state to the formation of singlet oxygen and more especially of superoxide ions and cation-radicals characteristic of the dye. Relative values of the formation rate were determined for these two mechanisms. Production of cation-radicals was correlated with phototoxicity in vivo. Chlorination enhances the two phenomena and acetylation reduces to nothing. A maximum value was estimated for the quantum yield of photoionization.