Synthesis, spectroscopic and mesomorphic studies on heterocyclic liquid crystals with 1,3-oxazepine-4,7-dione, 1,3-oxazepane-4,7-dione and 1,3-oxazepine-1,5-dione cores

Three series of newly derived 3-substituted-phenyl-2-(4-(tetradecyloxy)phenyl)-2,3-dihydro-1,3-oxazepine-4,7-diones, 3-substituted-phenyl-2-(4-(tetradecyloxy)phenyl)-1,3-oxazepane-4,7-diones and 4-substituted-phenyl-3-(4-(tetradecyloxy)phenyl)-3,4-dihydrobenzo[e][1,3]-oxazepine-1,5-diones have been synthesized from the reactions of 4-substituted-N-(4-(tetradecyloxy)benzylidene)aniline derivatives with maleic, succinic and phthalic anhydride. All structures were elucidated by physical measurements and the bonding characteristics of the resulting compounds were substantiated by FT-IR spectroscopy. Their molecular structures are supported by the 1H and 13C NMR spectra along with two-dimensional COSY, NOESY, HMQC and HMBC. The effect from different substituents upon thermal and mesomorphic behaviour has been investigated by differential scanning calorimetry and polarizing optical microscopy, respectively. All compounds possess relatively high phase transition temperatures with only 4-phenyl-3-(4-(tetradecyloxy)phenyl)-3,4-dihydrobenzo[e][1,3]oxazepine-1,5-dione exhibited the texture characteristics of the nematic phase.