Characterization of the Giant Transient Dipole Generated by Photoinduced Electron Transfer in a Carotene−Porphyrin−Fullerene Molecular Triad

Abstract

Excitation of a carotenoid (C) porphyrin (P) fullerene (C60) molecular triad yields the porphyrin first excited singlet state, C−1P−C60, which decays via a sequential two-step photoinduced electron-transfer process into a C•+−P−C60•- charge-separated state with a lifetime of 340 ns in 2-methyltetrahydrofuran solution. The transient dc photocurrent method has been used to investigate the dipole moment of the charge-separated state in tetrahydrofuran and 2-methyltetrahydrofuran. The results show formation of a giant dipole with a moment in excess of 150 D, corresponding to separated charges located on the fullerene and carotene moieties of the triad.