Asymmetric flavone-based liquid crystals: synthesis and properties

<p>A series of flavones (<b><i>n</i>-F</b>) substituted at the 4′, and 6 positions was prepared, characterised by NMR (<sup>1</sup>H,<sup>13</sup>C), HRMS, and studied for liquid crystal properties. The 4′-alkoxy,6-methoxyflavones (<b>4-F–16-F</b>) exhibit varying ranges of nematic and smectic A phases as evidenced by polarised optical microscopy and differential scanning calorimetry (DSC). As the tail length is increased, the smectic phase becomes more prevalent. Smectic phases for (<b>8-F–16-F</b>) were further analysed by powder X-ray diffraction (XRD), and the rate of structural transformations was explored by combined DSC/XRD studies. Flavonol <b>6-F–OH</b> was also prepared but no mesogenic behaviour was observed. The molecular structures of <b>6-F</b> and <b>6-F–OH</b> were determined by single-crystal XRD and help to explain the differences in material properties. Additionally, fluorescence and electrochemical studies were conducted on solutions of <b><i>n</i>-F</b>.</p>