Primary photochemical processes in dyads based on indocarbocyanine dyes and chlorin e₆

The spectral-kinetic study of deactivation processes of the excited singlet and triplet states of indocarbocyanine dyes (Dye1, Dye2, and Dye3) and chlorin e(6) (Chl), which constitute dyads I-III (Dye-Chl), was performed. In dyad Dye1-Chl, deactivation of the excited singlet state of the dye occurs mainly due to inductive-resonance energy transfer to Chl with the efficiency of 97%. The consequence of the energy transfer is population of the triplet level of Chl due to singlet-triplet intersystem crossing. In dyads Dye2-Chl and Dye3-Chl, deactivation of the excited singlet state of Chl occurs mainly due to inductive-resonance energy transfer to the dye molecule. The transfer efficiency is 96% for dyad Dye2-Chl and 85% for dyad Dye3-Chl with the shorter length of the -(CH2)- spacer, which binds the Dye3 and Chl molecules. In solutions of Chl and Dye2 (Dye3) mixtures in acetonitrile, exchange - resonance energy transfer occurs from the triplet level of Chl to the Dye2 (Dye3) molecule and electron transfer takes place involving triplet molecules of Dye2 (Dye3).