Liquid Crystalline Aryltriazene-1-Oxides with Two Ester Units: Synthesis, Characterisation, Structure and Thermal Properties

A new series of mesogenic triazene-1-oxides, C6H5-N(O)=N-NH-C6H4-C(O)-O- C6H4-O-(O)C-C6H4-OR (1, R=n-alkyl group from CH3 to C14H29), was designed and synthesised. All members of this new series were characterised on the basis of spectral and analytical data. The thermotropic liquid crystalline behaviour of the compounds was observed over a wide temperature range using optical microscopy. The mesophase structure was confirmed by a small-angle X-ray diffraction study of a representative member (1k). The molecular structure of compound 1i was determined using the single crystal X-ray diffraction method as a representative case. Dimer formation in the solid state occurs due to intermolecular N-H...O and C-H...O interactions. Intermolecular C-H...π interactions were also detected in 1i. The intermolecular hydrogen bonding and intermolecular C-H...p interactions arrange the phenyl triazene-1-oxide fragments of the molecules in layers within the molecular assembly.