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-ca lix[4]naphthalene 3 and its tert-butyl-substituted derivative 4 show that t hey form supramolecular 1∶1 complexes with C-60 in benzene, toluene o r CS2 solution with relatively high association equilibrium constants (K-as soc). Reported herein are thermodynamic parameters and additional K-assoc d etermined for the complexation of C-60 and calix[4]naphthalenes 3 and 4 whi ch show that both a solvophobic effect and pi-pi interactions are major dri ving forces for the complexation process.