Interchromophore interactions and energy transfer in covalently bound porphyrin-chlorine heterodimer

Abstract

Energetis of interchromophore interactions in a covalently bound prophyrin-chlorine heterodimer (Por-O-Chl) is investigated at temperatures from 77 to 293 K in solvents with differing polarity (toluene, tetrahydrofurane, and diethyl ether: petroleum ester: isopropanole=5∶5∶2 mixture). We substantiate the conclusion that the strong quenching of fluoresence and phosphorescence of the porphyrin fragments in both stable isomers of the Por-O-Chl heterodimer is induced not by the photoinduced charge transfer but rather by efficient processes of singlet-singlet (probability FSS=1.3·1011 to 6.8°1010 sec−1) and triplet-triplet (probability FTT≥108 sec−1) radiationless electronic excitation transfer. It is shown that the S−S transfer takes place without quantum losses from the thermodynamically equilibrated S1 state of the donor, and its dynamics and main regularities at temperatures from 77 to 293 K are described by the inductive resonance theory without any additional asssumptions.