Hydrogen-bonded liquid crystals formed from 4-alkoxystilbazoles and chlorophenols

Hydrogen-bonded complexes are formed between two chain lengths of 4-alkoxystilbazoles and six different chlorophenols. Single crystal structure determinations were possible for four of the complexes, all of which showed a similar dimeric motif in which two chlorophenols formed a loose back-to-back dimer with a stilbazole hydrogen-bonded at either side. Two of the complexes showed similarities in their three-dimensional packing. Liquid crystal properties were found for all complexes except those containing pentachlorophenol. The phase behaviour of the longer-chain dodecyloxystilbazole complexes was dominated by the observation of the smectic A phase, while both nematic and smectic A phases were found for the octyloxy homologues. The mesophase stability was appreciably lower in these new complexes when compared with fluorophenol analogues reported previously, attributed to a reduction in anisotropy on account of the effects of the greater size of chlorine compared with fluorine.

Automated summary

Hydrogen-bonded complexes were formed between 4-alkoxystilbazoles and different chlorophenols, and their crystal structures were determined. The complexes showed a dimeric motif with two chlorophenols and a stilbazole forming hydrogen bonds. Most complexes exhibited liquid crystal properties except those with pentachlorophenol. The stability of mesophases in these complexes was lower compared to fluorophenol analogues due to the larger size of chlorine atoms.