Photoinduced electron transfer in supramolecular donor–acceptor dyads of Zn corrphycene

Abstract

Porphyrins have been used by various researchers as important building blocks of photofunctional molecules, while the number of studies on the excitation properties of the structural isomers of porphyrins is small when compared to those of porphyrins. In the present study, photoinduced electron transfer (ET) processes of supramolecular donor–acceptor dyads of 2,3,6,7,11,12,17,18-octaethylcorrphycenatozinc (ZnCn), one of the porphyrin isomers, and some imide compounds, which can coordinate to the central Zn ion as an electron acceptor, were investigated. Formation of the supramolecular donor–acceptor dyads was confirmed by steady state absorption change. Charge separation and charge recombination processes upon photoexcitation of ZnCn of the supramolecular dyads were successfully observed by subpicosecond laser flash photolysis. The estimated ET rates (k_ET) were compared with those of other porphyrin isomers. Differences in the driving force dependence of k_ET values of porphyrin isomers were attributed to the electronic coupling and internal reorganization energy. Electronic and structural factors, which brought about the difference in k_ET values, were reasonably explained on the basis of the theoretical calculation.