Yield of intersystem (singlet-triplet) crossing in phthalocyanines evaluated on the basis of a time in resolved photothermal method

The yields of triplet state formation for seven various phthalocyanines (Pc) unsubstituted by metal and substituted by Mg, Zn, Cu and Al in dimethyl-sulfoxide (DMSO) solutions were compared on the basis of time resolved photothermal measurements. The sample with atmospheric oxygen and bubbled by nitrogen were investigated. Absorption, fluorescence, and steady state photoacoustic spectra (PAS) of the same samples were also measured. The yields of triplet state formation for most of metal substituted dyes were higher than for investigated metal-free dyes. The triplets for various dyes were differently quenched by oxygen. The possibility of the application of investigated dyes in photodynamic therapy and diagnosis was discussed. (C) 2001 Elsevier Science B.V. All rights reserved.