Synthesis and Mesomorphism of Novel Chiral Triphenylene-Based Discotic Liquid Crystals

Abstract

A series of new chiral triphenylene-based discotic liquid crystals with one or three chiral soft chains were synthesized through Mitsunobu reactions. Yields of the chiral discotic liquid crystals were achieved up to 84%. Chemical structures were confirmed by ¹H NMR; and mesomorphism was studied by polarized optical microscopy as well as by differential scanning calorimetry. The mesomorphic studies have shown that 1) the chiral discogens have either hexagonal columnar or plastic columnar mesophases; and 2) the introduction of chirality to triphenylene-based discotic liquid crystals could widen mesophase range by lowering melting points. In addition, an unexpected odd-even effect of mesomorphism was observed.

Keywords:

• Discotic liquid crystals
• hexagonal columnar mesophase
• Mitsunobu reactions
• odd-even effect
• plastic phase
• triphenylene

Acknowledgment

The authors would like to thank the National Natural Science Foundation of China (NSFC, No. 50973076) for generous financial support. YTL would like to thank the Undergraduate Students' Research Foundation of Sichuan Normal University for financial support.

Notes

^a All reactions were carried out using 1.0 equiv. 1, 3.0 equiv. 2, DIAD, PPh₃ and i-Pr₂NEt in 0.1 mol/L THF at room temperature for 3d.

^b Yields of isolated, purified products.

^a Unless otherwise noted, all reactions were carried out using 0.148 mmol of 1b and 0.444 mmol of 2 for 3d.

^b The reaction was carried out for only 1d.

^c The reaction was carried out for 3d.

^d The reaction was carried out for 4d.

^e Yields of pure, isolated 3b.

^a Cry, crystal state. Col_h, hexagonal column phase. Col_p, plastic column phase Iso, isotropic liquid.