Complexation of Fullerenes with 5,5‘-Biscalix[5]arene1

5,5‘-Biscalix[5]arene, prepared by oxidative coupling of the tetrabenzoyl ester of calix[5]arene (shown by X-ray crystallographic analysis to have a o,u,u,d,u conformation), forms complexes with C60 (Kassoc = 43 M-1) and C70 (Kassoc = 233 M-1). The X-ray crystallographic structure of the C60 complex reveals its clamshell-shaped architecture, presumably the result of a change in the conformation of biscalix[5]arene from anti (uncomplexed) to syn (complexed).