Supramolecular mesomorphic structures based on 2,5-dialkoxyterephthalicacid derivatives
Abstract
Self-assembly of 2,5-di-n-alkoxyterephthalic acids (CnOTpA) and 2,5-di-n-hexylterephthalic acid (C6TpA) as bifunctional hydrogen bond donors with bifunctional acceptors 1,3-diaminopropane (Dap), piperazine (Pip) and 4,4′-bipyridine (Bipy) has been investigated, both in the crystal lattice and in the mesophase. Stoichiometric mixtures of compounds CnOTpA with diamine Dap form mesophases with a lamellar-type structure and constitute, to the best of our knowledge, the first examples of the generation of mesophases from 2,5-di-n-alkoxyterephthalic acids and bifunctional diamines. The liquid crystalline behaviour of these mixtures was characterized using X-ray scattering, DSC and polarizing microscopy. The self-assembly of complexes C6TpA·Bipy and C6TpA·Pip in the crystal lattice was characterized using single crystal X-ray structural analysis. In the crystal lattice of C6TpA·Bipy, only hydrogen bonding interactions between the neutral acid and the base were observed. However, in the crystal structure of cocrystals of C6TpA with Pip, an ionic interaction was observed due to proton transfer from the acid group to the basic nitrogen atoms of the base.