High birefringence and large negative dielectric anisotropy phenyl-tolane liquid crystals

Two phenyl-tolane compounds with two pairs of (2,3) lateral difluoro substitutions were synthesized and their properties evaluated. These compounds exhibit a high birefringence (epsilon similar to 0.35) and a large negative dielectric anisotropy ( De, 28). These two important features make the phenyl-tolane compounds useful as a dopant in a negative Delta epsilon liquid-crystal mixture to enhance the performance of the host mixture, or as a negative component in a dual-frequency liquid-crystal mixture to improve the dielectric anisotropy and birefringence and lower the crossover frequency.