Photoinduced electron transfer and dynamic behavior of charge-separated state nonlinear optical process in a self-assembled porphyrin supramolecular system

The spectroscopic properties of a supramolecular system consisting of two oppositely charged porphyrin monomers, zinc tetra(4-sulfonoatophenyl)porphyrin and zinc tetra(N-methylpyridyl)porphyrin were studied by absorption and fluorescence spectroscopy. The stoichiometry of the self-assembled porphyrins were determined by a fluorimetric titration method showing the formation of the 1:1 heterodimer. Photoinduced electron transfer and charge separation in the supramolecular system have been studied by time resolved forward degenerate-four-wave-mixing (DFWM) geometry. The results indicated the formation of the charge-separated state within 30 ps and the recombination time is about 340 ps. Light-induced enhancement of third-order nonlinear optical (NLO) susceptibility was observed.