Photoluminescent discotic liquid crystals derived from tris(N-salicylideneaniline) and stilbene conjugates: Structure–property correlations

• Luminescent LCs based on tris(N-salicylideneaniline)s bearing trans-stilbene fluorophores.
• Dependance of the thermal behavior and photophysical properties on the peripheral substitution.
• Emission in solution and glassy columnar phase.

Luminescent discotic liquid crystals based on tris(N-salicylideneaniline)s [TSANs] bearing trans-stilbene fluorophores have been synthesized. Their mesomorphic and photophysical properties were studied. These TSANs existing in the form of C3h and Cs geometrical isomers of the keto-enamine tautomer self-assemble to form the columnar phase and exhibit fluorescence both in solution and mesophase states. These columnar mesophases also exhibit frozen (glassy) columnar phase, which ensures preserved fluorescence intensity, defect free alignment and simultaneous restriction on the motion of ionic impurities. These features make them promising candidates for the use in organic light emitting diodes, particularly as emissive layers. This study also led to an understanding about the dependence of their mesomorphism (mesophase type, stability and thermal range) and photophysical features on the number and pattern of their peripheral substitution, in comparison to the analogous columnar liquid crystalline TSANs reported earlier.

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