Both [60]- and [70]fullerenes have been shown to form 1:1 supramolecular complexes with (i) 49,50,51,52,53,54,55,56-octamethoxy-5,11,17,23,29,35,41,47-octa-(4-tert-butyl)calix[8]arene (1), (ii) 37,38,39,40,41,42-hex amethoxy-5,11,17,23,29,3 5 -hexa(4-tert-butyl)calix [6] arene (2), (iii) 37,39,41-trimethoxy-38,40,42-trihydroxy-5,11,17,23,29,35-hexa-(4-tert-butyl)calix[6]arene (3), and (4) 24,26-dimethoxy-25,27-dihydroxy-5,11, 17,23-tetra(4-tert-butyl)calix[4]arene (4) in carbon tetrachloride medium by NMR spectroscopy. Formation constants (K) of the above complexes have been determined from the systematic variation of NMR chemical shifts of specific protons of the calixarenes in the presence of [60]- and [70]fullerene. In one particular case it has been possible to show from the C-13 NMR signal that during inclusion the host (3) is preorganized in the conical conformation and the guest molecule approaches from the wider side containing the tert-butyl group.
