Room-Temperature, Deep-Red/NIR-Emissive, <i>C</i>₃-Symmetric (n,π-conjugated) Columnar Liquid Crystals: <i>C</i>_3<i>h</i>-Tris(keto-hydrazone)s

Abstract

The first examples of deep-red/near-infrared (NIR) photoluminescent, (n,π-conjugated) discotics, namely, <i>C</i> _3<i>h</i> -tris(keto-hydrazone)s, which are the tautomers of tris(azo-enol)s, have been synthesized via a facile one-step triple azo-coupling and characterized. The n,π-resonance-assisted intramolecular H-bonding, rendering planarity and shape persistence to the central core, facilitates their self-assembly into either a hexagonal columnar (Col_h) phase (<i>p</i>6<i>mm</i> lattice) or a columnar rectangular (Col_r) phase (<i>p</i>2<i>mm</i> lattice), over an extended thermal range including room temperature, fluorescing in the deep-red/NIR-I region. The low band gap with deep-red/NIR emission makes them ideal candidates for NIR-organic light-emitting diodes (OLEDs) and bioimaging.