Molecular recognition of p-tert-butylcalixarenes by surface-linked fullerenes C60 and C70

The complexation processes between fullerenes (C60 and C70) and p-tert-butylcalix[n]arenes with n=6 and 8 are investigated using a chromatographic method in which the fullerenes are surface-linked to HPLC silica microparticles. Thermodynamic parameters for complex formation are extracted from variable temperature chromatography in two different solvent systems. Associations are always enthalpy driven and entropy opposed, with the larger p-tert-butylcalix[8]arene forming the tightest complex.