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

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Abstract
Two isomeric [5,6]-pyrrolidine−Ih-Sc3[email protected]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 C60 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 C60 for Ih-Sc3[email protected]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 C60 and Ih-Sc3[email protected]80 dyads. In addition to that, the N-substituted TPA−Ih-Sc3[email protected]80 dyad has much better thermal stability than the 2-subtituted one. Finally, the Ih-Sc3[email protected]80 dyads have considerably longer lived charge separated states than their C60 analogues, thus approving the advantage of using Ih-Sc3[email protected]80 instead of C60 as the acceptor for the construction of fullerene based donor−acceptor conjugates. These findings are important for the design and future application of Ih-Sc3[email protected]80 dyads as materials for the construction of plastic organic solar cells.