| Abstract: | The mesomorphic properties of 2-(4-alkoxybenzoyloxy)-5-alkylaminotropones and 5-alkoxy-2-(4-alkylaminobenzoyloxy)tropones are discussed on the basis of results obtained by X-ray crystallographic and X-ray diffraction studies, as well as temperature-dependent FTIR spectral measurements. The X-ray crystallographic analysis of 2-(4-dodecylaminobenzoyloxy)-5-tetradecyloxytropone (2f) indicated that it formed a head-to-tail dimer through an intermolecular hydrogen bond between the NH and the tropone carbonyl group. The X-ray diffraction study of compound 2f suggested that the molecules formed interdigitated bilayer smectic C phases with a tilt angle of as much as c. 40° to a layer plane. The corresponding benzenoids, however, were non-mesomorphic, with higher melting points than the troponoids. In the troponoids, sigmatropic migration of the benzoyl group weakened the intermolecular hydrogen bonding and assisted the occurrence of mesomorphic properties. |
