Photoinduced Charge Transfer and Electrochemical Properties of Triphenylamine Ih-Sc3N@C80 Donor-Acceptor Conjugates

Two isomeric [5,6]-pyrrolidine-I-h-Sc3N@C-80 electron donor-acceptor conjugates containing triphenylamine (TPA) as the donor system were synthesized. Electrochemical and photophysical studies of the novel conjugates were made and compared with those of their C-60 analogues, in order to determine (i) the effect of the linkage position (N-substituted versus 2-substituted pyrrolidine) of the donor system in the formation of photoinduced charge separated states, (ii) the thermal stability toward the retro-cycloaddition reaction, and (iii) the effect of changing C-60 for I-h-Sc3N@C-80 as the electron acceptor. It was found that when the donor is connected to the pyrrolidine nitrogen atom, the resulting dyad produces a significantly longer lived radical pair than the corresponding 2-substituted isomer for both the C-60 and I-h-Sc3N@C-80 dyads. In addition to that, the N-substituted TPA-I-h-Sc3N@C-80 dyad has much better thermal stability than the 2-subtituted one. Finally, the I-h-Sc3N@C-80 dyads have considerably longer lived charge separated states than their C-60 analogues, thus approving the advantage of using I-h-Sc3N@C-80 instead Of C-60 as the acceptor for the construction of fullerene based donor-acceptor conjugates. These findings are important for the design and future application Of I-h-Sc3N@C-80 dyads as materials for the construction of plastic organic solar cells.