Induced and enhanced mesomorphism through intermolecular hydrogen-bonding interactions: influence of rigid core and π–π interactions

A non-mesogenic proton acceptor, viz., (4-pyridyl)-benzylidene-4ʹ- n -heptyl aniline (PyB7A), is prepared and treated with non-mesogenic proton donors, viz., aliphatic and aromatic carboxylic acids, in a 1:1 molar ratio, and their mesomorphism is studied. The non-mesogenic aliphatic acids used are nonyl, undecyl, tridecyl, tetradecyl, hexadecyl and octadecanoic acids which are non-toxic, biodegradable and biocompatible; and the non-mesogenic aromatic carboxylic acids used are x -fluoro/ x -chlorobenzoic acids ( x is the position of the substituent, x = 2, 3 or 4). The proton donors and acceptors are non-mesogens and are involved in intermolecular hydrogen-bonding (HB) interactions, resulting a smectic mesomorphism. The HBs between the moieties were characterized by Fourier transform infrared (FTIR) spectroscopy. The mesomorphic thermal stabilities of the PyB7A: m A and PyB7A: x (F/Cl)BA HB complexes are discussed in comparison with the similar HB complexes viz., PyB14A: m A; PyB16A: x (F/Cl)BA; PyB16A: n OBA and n OBA dimers. The number of aromatic rings i.e., rigid cores and the π – π interactions in the HB complexes on the induced mesomorphism are discussed. This research supports sustainable production practices, advancing SDG 12.