New supramolecular hydrogen-bonded liquid crystals based on 4-alkylbenzenesulfonic acids and 4-pyridyl 4′-alkyloxybenzoates: Quantum chemical modeling and mesomorphic properties

Abstract The results of quantum-chemical modeling of the self-assembly process in the system based on 4-alkylbenzenesulfonic acids and 4-pyridyl 4′-alkyloxybenzoates are presented. It has been shown that the interaction of the pyridyl fragment of 4-pyridyl 4′-alkyloxybenzoat and the sulfonic group of 4-alkylbenzenesulfonic acid leads to the strongest H-complexes. The potential function of proton transfer from the sulfonic group to the pyridyl fragment was simulated both in the gas phase and in a solvent (ethanol). It was found that an H-complex with a hydrogen bond of the O∙∙∙H–N type is formed between the compounds under study. FTIR spectra of the 1(4-alkylbenzenesulfonic acid) : 1(4-pyridyl 4′-alkyloxybenzoate) systems confirm the results of quantum chemical calculations. The mesomorphic properties of the 1(4-methylbenzenesulfonic acid) : 1(4-pyridyl 4′-heptyloxybenzoate) supramolecular complex were studied using DSC and polarizing microscopy. It is shown that the H-complex formed by 4-methylbenzenesulfonic acid and 4-pyridyl 4′-heptyloxybenzoate has a smectic mesophase with expanded temperature range (59o) in comparison with the 4-pyridyl 4′-heptyloxybenzoate (28o).