Photoinduced electron-transfer processes between fullerene (C60) and 1,8-bis(dimethylamino)naphthalene, which is called a proton-sponge (PS), have been investigated by means of laser flash photolysis in the presence and absence of CF3CO2H. For a mixture of CM and PS, the transient absorption spectra showed the rise of the C60 radical anion with concomitant decay of the CM triplet (3C60*), suggesting that photoinduced intermolecular electron transfer occurs via 3C 60* in high efficiency in polar solvent. For a covalently bonded C60-PS dyad, photoinduced intramolecular charge-separation process takes place via the excited singlet state of the CM moiety, although charge recombination occurs within 10 ns. For both systems, electron-transfer rates were largely decelerated by addition of a small amount of CF 3CO2H, leaving the long-lived 3C 60*. These observations indicate that the energy levels for charge-separated states of the protonated PS and C60 become higher than the energy level of the 3C60 moiety, showing low donor ability of the protonated PS. Thus, intermolecular electron-transfer process via 3C60* for C60-PS mixture and intramolecular charge-separation process via 1C60*- PS for C60-PS dyad were successfully controlled by the combination of the light irradiation with a small amount of acid.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry