Hydrogen-bond mediated columnar liquid crystalline assemblies of C 3 -symmetric heptazine derivatives at ambient temperature

• Published in: Soft matter 2018-08, Vol.14 (30), p.6342-6352
• Main Authors: Bala, Indu, Gupta, Santosh Prasad, Kumar, Sunil, Singh, Harpreet, De, Joydip, Sharma, Neha, Kailasam, Kamalakannan, Pal, Santanu Kumar
• Format: Article
• Language: English
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c8sm00834e

A new class of hydrogen (H) bonded fluorescent liquid crystals (FLCs) based on a newly discovered s-heptazine fluorophore discotic component have been synthesized. The tendency of the s-heptazine core to form H-bonded LCs has been explored for the first time. Interestingly, the pure heptazine derivatives (non-mesomorphic) on complexation with tri-alkoxy benzoic acids exhibit enantiotropic columnar mesomorphism over a wide range of temperatures including room temperature. This indicates the strength of the resulting H-bonded complexes. The H-bonded supramolecular complexes were studied through FT-IR, temperature dependent FT-IR and NMR studies and H-D exchange studies, and their thermal behaviour was deduced through polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. Because of the inherently fluorescent pure heptazine derivative, the resulting complexes exhibit fluorescent behaviour in the solution state as well as in the solid state.