Preparation of discotic metallomesogens based on phenacylpyridines showing room temperature columnar phases

Abstract

Discotic metallomesogens were prepared by complexation of phenacylpyridine ligands with copper(II) and palladium(II) ions. Picoline derivatives with an alkoxy chain were prepared by the reaction of 5-hydroxy-2-methylpyridine with alkyl bromides. In a similar manner, methyl 3,4,5-trialkoxybenzoates were obtained from methyl 3,4,5-trihydroxybenzoates and alkyl bromides. 5-Alkoxy-2-methylpyridines were metallated with lithium diisopropylamine and reacted with methyl benzoates to give ligand compounds 1–3. Metal complexes Cu1–3 and Pd1–3 were prepared by complexation of the ligands with copper(II) acetate and palladium(II) acetate in tetrahydrofuran, respectively. The ligands did not form liquid crystals, but their metal complexes showed enantiotropic columnar hexagonal mesophases at room temperature.

The metal complexes of phenacylpyridines showed a superior ability to self-assemble into ordered phases compared to their structural analogues, the salicylaldiminato complexes.

Keywords:

• metallomesogen
• phenacylpyridine
• salicylaldimine
• discotic liquid crystal

Acknowledgement

This work was supported by the grant from the Global Research Lab program of Ministry of Education, Science and Technology, Korea.