Saddle-shaped tetraphenylenes with peripheral gallic esters displaying columnar mesophases

Tetraphenylenes 2 with eight peripheral gallic esters were prepared in two steps from octamethoxytetraphenylene 1 in 19–72% yield. Investigation of the mesomorphic properties of 2 by DSC, POM and X-ray diffraction revealed that derivatives 2a–d with short alkoxy chain lengths (C(5)–C(8)) did not show any mesomorphic properties, whereas compounds 2e–i with C(9)–C(13) chains displayed rectangular columnar mesophases and compounds 2j–l with C(14)–C(16) chains displayed hexagonal columnar mesophases. Furthermore an anomalous odd-even effect of the clearing points of compounds 2e–l versus chain length was detected.