Characterization of quasi-liquid crystalline spiroxazine derivatives

The structures of new spiroxazine derivatives containing a megogenic group attached to 9-position of the naphthoxazine ring was synthesized and characterized by their photo- and thermochromic properties and the intrinsic liquid crystal behavior. All of these derivatives showed the reversible photo- and thermochromism near the melting temperature and only one derivative demonstrated quasi-liquid crystalline behavior. The structural changes as increasing the sample temperature were monitored by FT-IR. The photochromic response of visible absorption at 575 and 606 nm upon 365-nm irradiation was also monitored by UV–Vis absorption spectroscopy. DSC data showed that compound 1 demonstrated a phase transition at near 65 °C during cooling and heating cycle followed by the iso-melting process. Furthermore, polarizing microscopic study and X-ray diffraction (XRD) measurement indicated that compound 1 demonstrated Schlieren texture and nematic liquid crystalline characteristics with one-directional isotropic alignment.