All-fullerene Electron Donor-Acceptor Conjugates

Abstract

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 syn and 8 with anti orientation, being the anti-RSSS isomer 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 of the singlet C60 --Lu3N@Ih-C80 + charge-separated state into the triplet C60 --Lu3N@Ih-C80 + charge-separated state is facilitated by the heavy atom affect stemming from the Lu3N-cluster and, in turn, slows down the charge recombination by one order of magnitude