Design, Synthesis, and thermo-optical characterisation of novel hockey stick-shaped 1,3,4-oxadiazole derivatives

A new series of 1,3,4-oxadiazole derivatives featuring a hockey-stick-shaped molecular architecture, composed of five interconnected phenyl rings linked via imine and ester functionalities, was successfully synthesised. The target compounds, designated as 4-(((4-(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)phenyl)imino)methyl)phenyl-4-((4-alkoxyben-zylidene)amino)benzoate [Dn], were thoroughly characterised by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), mass spectrometric analysis (GC-MS), and elemental analysis. The liquid crystalline properties of the series were investigated using polarised optical microscopy (POM) and differential scanning calorimetry (DSC). The homologues [D6-D11] exhibited a liquid crystalline behaviour, displaying both smectic A (SmA) and smectic C (SmC) mesophases across a broad temperature range, beginning at approximately 140°C. A comparative analysis indicated that the insertion of the (-N=CH-Ph) moiety into the molecular core influences the mesomorphic behaviour of the synthesised derivatives relative to previously reported compounds.