Development of novel azobenzene derivatives showing a room temperature liquid-crystalline phase and their photoresponsive behavior

Novel azotolane derivatives containing various structures of alkyl chains have been synthesized via palladium-catalyzed cross coupling reactions as the key step. The thermotoropic liquid crystalline behavior of these compounds was investigated by polarizing optical microscopy, differential scanning calorimeter, and X-ray scattering, and the influences of the structure and position of the lateral alkyl chain on the mesomorphic properties were studied. Depending on the size or the structure of alkyl chains, different liquid crystalline phases were detected. Furthermore, we found that all compounds show trans-cis photoisomerization behavior upon irradiation of ultraviolet light, as well as a conventional azobenzene moiety.