Pyrazaboles-Based Bent-Core Liquid Crystals

Significance

The authors demonstrate an innovative approach to a bent angle in a liquid-crystal molecule through the use of a nonplanar core derived from a pyrazabole unit appropriately substituted with rod-like moieties. Pyrazabole results from the dimerization of two pyrazole rings through a double BH₂ bridge connected to the ­nitrogen atoms, a process that gives a stable six-membered central B₂N₄ ring with a boat conformation. Sonogashira cross-coupling reaction of 2,6-bis(ethynyl)pyrazabole or the deuterated analogue 4,4,8,8-tetradeutero-2,6-bis(ethynyl)-pyrazabole with two equivalents of 4-iodophenyl 4-tetradecyloxybenzoate yielded the target molecules.