Advanced Functional Materials, Vol.11, No.6, 441-446, 2001
Novel columnar tetraphenylethenes via McMurry coupling
Several tetraphenylethenes 2a, 4a-i with lipophilic side chains were synthesized and their mesomorphic properties were investigated. The most promising candidates turned out to be tetrakis[4-(trisalkloxybenzoyloxy)phenyl]ethenes 4e-i with chain lengths between C-7 and C-12. Compounds 4 were prepared by a convergent strategy employing a McMurry coupling of 4,4'-dimethoxybenzophenone 1c. followed by demethylation and subsequent esterification of 2c with either 4-decyloxybenzoic acid 3a, 3,4-didecyloxybenzoic acid 3b, or O-alkylated gallic acids RA. Despite the twisting of the central tetraphenylethene moiety compounds 4c-i display hexagonal columnar mesophases according to differential scanning calorimetry (DSC), polarizing microscopy, and X-ray diffraction studies.