Synthesis of 18-Membered Open-Cage Fullerenes through Controlled Stepwise Fullerene Skeleton Bond Cleavage Processes and Substituent-Mediated Tuning of the Redox Potential of Open-Cage Fullerenes

Oxidation of the fullerenediol C60(OH)2(O)­(OAc)­(OOtBu)3 with PhI­(OAc)2 yields the open-cage fullerene derivative C60(O)2(O)­(OAc)­(OOtBu)3 2 with an 11-membered orifice. Compound 2 reacts with aniline to form a new open-cage derivative with a 14-membered orifice, which yields an 18-membered open-cage fullerene derivative upon addition of another molecule of aniline. Two different types of aniline derivatives with either electron-donating or electron-withdrawing substituents can be added sequentially, affording an unsymmetrical moiety in the open-cage structure. Reduction potentials of the 18-membered open-cage fullerene derivatives can be fine-tuned by changing the substituents on the aniline. The results provide new insights about the mechanism of open-cage reactions of fullerene-mixed peroxide.