Novel oxazepinedione-derived symmetric dimers: synthesis and mesophase characterisation of seven-membered heterocyclic compounds

Abstract

The synthesis and characterisation of three sets of symmetric dimeric compounds composed of seven-membered oxazepinedione heterocyclic rings were carried out. All the dimers possess the tetradecyl-(n = 14) alkyl side chain attached to the nitrogen atom of the oxazepinedione core. The oxazepinedione core in turn was connected with varied connecting spacers (n = 4, 6, 8, 10 and 12). The dimers were spectroscopically characterised by FT-IR, 1 H-NMR, 13 C-NMR and elemental analysis techniques. The compounds were investigated for liquid crystalline properties using differential scanning calorimetry and polarising optical microscopy with heating assembly. The precursor imines 2a-e itself started exhibiting liquid crystalline SmA/tilted hexatic mesophase. Further fusion of 2a-e with maleic anhydride, succinic anhydride and phthalic anhydride gave the novel oxazepinedione-derived symmetric dimers 3a-e, 4a-e and 5a-e respectively. The dimers 3a-e and 4a-e did not exhibit any liquid crystal (LC) properties. However, the phthalic anhydride-fused oxazepinediones 5a-e show monotropic nematic liquid crystalline phase. The results indicate that the formation of mesophase is dependent on the type of fused oxazepinedione ring. ARTICLE HISTORY