Thermodynamic study of the complexes of calix[4]naphthalenes with [60]fullerene in different solvents

Calix[4]naphthalenes are a class of molecules which possess deeper cavities than those of the analogous calix[4]arenes. Preliminary data obtained for the complexation of [60]fullerene (C-60) with the C-4-symmetrical endo-calix[4]naphthalene 3 and its tert-butyl-substituted derivative 4 show that they form supramolecular 1∶1 complexes with C-60 in benzene, toluene or CS2 solution with relatively high association equilibrium constants (K-assoc). Reported herein are thermodynamic parameters and additional K-assoc determined for the complexation of C-60 and calix[4]naphthalenes 3 and 4 which show that both a solvophobic effect and pi-pi interactions are major driving forces for the complexation process.