5,6-Difluorobenzofuran: a new core for the design of liquid crystal compound with large dielectric anisotropy and broad nematic range

Abstract

ABSTRACT New liquid crystal compounds with 5,6-difluorobenzofuran core were synthesised by palladium catalysed coupling and ring-closing reaction. Their structures were identified using 1HNMR, 13CNMR and MS. Thermo analysis show that these compounds exhibit a broad nematic range and high clearing points. Physical property test revealed that the dielectric anisotropies of these compounds are about 11 ~ 17, which is twice of that of the 3, 4-difluorinated benzene analogues. DFT calculation results show that the 5, 6-difluorobenzofuran-based compounds have much larger polarisation and dipole moments compared with the common 3,4-difluorobenzene compounds, which leads to a significant increase in dielectric anisotropy and birefringence. As a new fluorinated building block, 5, 6-difluorobenzofuran shows a good prospect for display device.