All‐Fullerene Electron Donor–Acceptor Conjugates

The synthesis and characterization of a covalent all‐fullerene C60‐Lu3N@Ih‐C80 electron donor–acceptor conjugate has been realized by sequential 1,3‐dipolar cycloaddition reactions of azomethine ylides on Lu3N@Ih‐C80 and C60. To the best of our knowledge, this is the first time that two fullerenes behaving as both electron donor (Lu3N@Ih‐C80) and acceptor (C60) are forming an electroactive dumbbell. DFT calculations reveal up to 16 diastereomeric pairs, that is, 8 with syn and 8 with anti orientation, with the anti‐RSSS isomer being the most stable. Spectroelectrochemical absorption and femtosecond transient absorption experiments support the notion that a C60⋅−‐Lu3N@Ih‐C80⋅+ charge‐separated state is formed. Spin conversion from the charge‐separated singlet state C60⋅−‐Lu3N@Ih‐C80⋅+ into the corresponding triplet state is facilitated by the heavy‐atom effect stemming from the Lu3N‐cluster, which, in turn, slows down the charge recombination by one order of magnitude. Dumbbell charge transfer: The synthesis of an all‐fullerene electron donor–acceptor conjugate, C60‐Lu3N@Ih‐C80, is reported. In the dumbbell‐like system, one fullerene moiety acts as the donor (Lu3N@Ih‐C80) while the other acts as the acceptor (C60). Spin conversion of the charge‐separated singlet state into the corresponding triplet state slows down the charge recombination by one order of magnitude.