A highly ordered hydrogen-bonded network

Self-assembled, hydrogen bonded, supramolecular complexes based on the interaction of pyridine with carboxylic acids have been synthesized. These contain different proportions of a compound with two terminal benzoic acid residues and a pentaerythritol-based tetra-pyridyl. They have been investigated for possible mesomorphic properties. Surprisingly for a tetrahedral pentaerythritol-based complex, a mesophase was observed with a grainy microscopic texture, which was fluid and could be sheared. The mesogenic unit is formed on hydrogen bonding complexation between the pyridyl residues and the carboxylic acid residues. Infrared spectra, as a function of the temperature, were recorded for the 1:1 complex; these show pyridyl complexation and changes on isotropisation. These changes are discussed in terms of the hydrogen bonding. Fibres could be drawn from the (mesophase) melt, supporting a polymeric, extended-chain structure for the complexes.