Light emitting, star-shaped tris(N-salicylideneaniline) discotic liquid crystals bearing trans-stilbene fluorophores: synthesis and characterization

Star-shaped tris(N-salicylideneaniline) discotics possessing trans-stilbene fluorophores have been synthesized by condensing 1,3,5-triformylphloroglucinol with 4-(alkoxystyryl)benzen-amines, and characterized. 1H and 2D 1H–1H COSY NMR experiments reveal their occurrence in two inseparable keto-enamine tautomeric forms featuring C3h and Cs rotational symmetries. Their columnar liquid crystal behavior has been ascertained unequivocally with the aid of a polarizing optical microscope and a differential scanning calorimeter. Photoluminescence property has been examined both in solution and columnar states. Green light emission observed in the solution state is especially noteworthy. Thus, intrinsic self-assembly into a fluid columnar state exhibiting light emission property clearly illustrates their significance in technological applications.