RIGID CONE CALIX[4]ARENES AS PI-DONOR SYSTEMS - COMPLEXATION OF ORGANIC-MOLECULES AND AMMONIUM-IONS IN ORGANIC MEDIA

One step synthesis of calix[4]arene biscrowns, with a rigid cone struc ture and alkyl or phenyl groups at the 'upper rim', has been performed . The binding ability of these rigidified cone calix[4]arenes 1-4, 13 has been evaluated, in apolar organic media, towards neutral organic m olecules and ammonium cation salts. Comparison with more flexible anal ogues 5, 6, 11 shows that only rigid cone calix[4]arenes are able to c omplex organic species. The association constants strongly depend on t he type of substituents present at the upper rim. The X-ray crystal st ructure of the endo complex p-cyclohexyl-25,26-27,28-biscrown-3-calix[ 4]arene 3 with CH3NO2 has been resolved.