Wedge-shaped 1,2-diamidobenzenes forming columnar mesophases via hydrogen bonding

Abstract

Two series of o-diamidobenzenes, bearing long-chain alkyl substituted gallic ester groups, have been synthesised. The 3,4,5,6-unsubstituted amides 7 with a minimum chain length of C₉ exhibited columnar rectangular mesophases of p2mm symmetry with Z = 2. The liquid crystalline phases spread over phase width of extremely wide temperature intervals from -50 to 118°C. However, the phase width slightly decreased with an increase in the length of alkyl substituents. Despite their very similar molecular structure, 1,2-dimethoxy-4,5-diamides 10 revealed a different packing behaviour in their mesophases, due to steric factors. The diamides 10 formed columnar rectangular mesophases with p2mm symmetry, but with Z = 3. In a comparison with unsubstituted analogues 7, compounds 10 displayed even broader mesophases (with temperature intervals up to 220°C).

Keywords:

• amides
• 1,2-diaminobenzene
• columnar rectangular mesophase
• liquid crystals
• hydrogen bonding

Acknowledgements

Generous financial support by the Bundesministerium für Bildung und Forschung, the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg, the Max-Planck-Gesellschaft (International Max Planck Research School for Advanced Materials fellowship for M.K.) and the Fonds der Chemischen Industrie is gratefully acknowledged.