Spectroscopic and crystallographic study of 27,28-diethoxy-p-tert-butylcalix[4]arenes

The molecular conformation of the anti form of the title compound, i.e. with the two neighbouring phenylethylether fragments in anti positions, is a partial cone. The conformation is stabilized by two intramolecular hydrogen bonds. These bonds involve both the phenolic OH groups as donors and a hydroxyl group and an ethoxygroup as acceptors. FT-IR solid state spectra reveal two OH bands at 3388 and 3175 cm^-1 which is in accordance with the observed hydrogen-bond configuration. In CCl₄ solution the partial cone is preserved for the anti form (3378 and 3187 cm^-1) while the corresponding syn form mainly adopts a cone conformation characterized by O-H stretching vibrations at 3360 and 3168 cm^-1.