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

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 F^SS=1.3·10¹¹ to 6.8°10¹⁰ sec⁻¹) and triplet-triplet (probability F^TT≥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. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 75–82, January–February, 1998.