An example of an unsymmetrically substituted, monofunctionalized anthraquinone-based discotic liquid crystal

We report here the synthesis and characterization of an unsymmetrically substituted, monofunctionalized anthraquinone-based discotic liquid crystal, namely 5-hydroxy-1-(4-nitrobenzyloxy)2,3,6,7-tetrapentyloxy-9,10-anthraquinone. Interestingly, this compound, which has only four alkyloxy chains attached to the anthraquinone core, shows a hexagonal columnar phase (Col_h) of much wider temperature range compared with analogues having six alkyloxy chains. Incidentally, among the anthraquinone-based disc-like molecules exhibiting columnar phases known so far, this is the first molecule, which does not possess any C₂-axis of symmetry. Besides its unsymmetrical structure and interesting mesomorphic behaviour, monofunctionalized monomers of this kind, unlike the available C₂-symmetric difunctionalized tetraethers, can serve as potential synthons for obtaining dimers in a unique way. In addition, various anthraquinone-based oligomers, metallomesogens, and side group liquid crystalline polymers can be obtained from these monomers.