New H-Bonded Complexes and Their Supramolecular Liquid-Crystalline Organizations

Different approaches to the design of liquid crystals by using H-bonds were analyzed. A selection of stilbazoles and pyridine compounds, with one or two chelating positions, were used as H-acceptors in mixtures with carboxylic acids. The noncovalent complexes in question afforded calamitic mesomorphism (N, SmA and SmC) as well as a lamellar mesophase (SmCP). Additionally, the liquid crystalline behaviour of the new 2-hydroxy- and 2-aminopyridine compounds as pure materials is also discussed. Useful results concerning the design and stability of noncovalent calamitic and bent-core liquid crystals are reported. To induce the bent-core liquid crystalline order, the conformational flexibility around the H-bond must be controlled. The new liquid crystals were characterized by IR spectroscopy, optical microscopy, calorimetry, X-ray diffraction and dielectric spectroscopy.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)