Photoinduced charge transfer and electrochemical properties of triphenylamine I(h)-Sc3N@C80 donor-acceptor conjugates.

Two isomeric [5,6]-pyrrolidine-I(h)-Sc(3)N@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)-Sc(3)N@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)-Sc(3)N@C(80) dyads. In addition to that, the N-substituted TPA-I(h)-Sc(3)N@C(80) dyad has much better thermal stability than the 2-substituted one. Finally, the I(h)-Sc(3)N@C(80) dyads have considerably longer lived charge separated states than their C(60) analogues, thus approving the advantage of using I(h)-Sc(3)N@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)-Sc(3)N@C(80) dyads as materials for the construction of plastic organic solar cells.