Synthesis of p-tert-butylcalix[4]arene semitubes and their binding studies with C60

The synthesis of p-tert-butylcalix[4]arene semitubes in one step reaction with fairly good yields is described. The structures of these compounds were confirmed by H-1 NMR, (CNMR)-C-13 and mass spectrometry. The complexation ability of these compounds with C-60 was investigated and found that they are able to form 1:1 complexes. The stability constants of these complexes were determined and found to be 15, 203 and 525 dm(3) mol(-1) for the semitubes 3a, 3b, 3c respectively. The binding energies of each of C-60, the semitubes and the complexes are calculated using PM6 (Semiempirical quantum chemical) and DFT (Density Functional Theory) methods and found in the order m > p > o. On the other hand, the calculated binding energies using DFT method showed that the stabilities of both centered and side complexes are in the order p > m > o.