In Situ Switching of Photoinduced Electron Transfer Direction by Regulating the Redox State in Fullerene-Based Dyads.

Novel fullerene-based donor-acceptor (DA) dyads, Sc3N@C80-PTZ and C60-PTZ, have been synthesized and investigated in which the photoinduced electron transfer direction is proved to be switchable by regulating the redox state. In detailed photophysical experiments, reductive electron transfer from the PTZ moiety to Sc3N@C80 is confirmed with transient absorption (TA) spectroscopy in the neutral Sc3N@C80-PTZ dyad. After oxidizing the PTZ moiety to PTZ•+ in a reversible manner, oxidative electron transfer from the Sc3N@C80 moiety to the PTZ•+ radical cation is corroborated experimentally and theoretically, leading to formation of a metastable charge transfer (CT) state (Sc3N@C80)•+-PTZ, which is not observed in the C60-PTZ•+ dyad. To the best of our knowledge, this is the first time in situ tunable molecular photodiode-like behavior is fulfilled utilizing a fullerene dyad. These findings will contribute to the future application of fullerene-based DA conjugates in molecular electronic devices.