Columnar Liquid Crystals with a Central Crown Ether Unit

Novel columnar liquid crystals 5a – f bearing a dibenzo[18]crown[6] central unit have been prepared from bromodialkyloxybenzenes 1 and tetrabromodibenzo[18]crown[6] 2 via Suzuki coupling reactions. Differential scanning calorimetry (DSC) revealed that the length of the alkyl chains in the liquid‐crystalline compounds 5 influenced their mesomorphic properties. Whereas 5a – d gave fan‐shaped textures only upon rapid cooling, 5e and 5f with C9 and C10 side chains formed stable columnar textures upon slow cooling. A hexagonal columnar mesophase of 5a is apparent from X‐ray diffraction studies. Complexation of 5 with potassium significantly shifted the clearing points to higher temperatures and also increased the mesophase stability in the cooling cycle.