Synthesis, Crystal Structures and Mesomorphic Properties of Liquid Crystals with a N,N′-Bis(tropon-2-yl)piperazine Skeleton

New troponoid liquid crystals with a N,N′-bis(tropon-2-yl)piperazine core were prepared. N,N′-Bis(tropon-2-yl)piperazine derivatives (1) had a smectic C phase with lower thermal stabilities than the corresponding benzenoid derivatives (2), which had a smectic B phase. A single crystal of 1d had distinct layer structures observed in a smectic C phase.