Piperidine and 3,3,4,4,5,5-hexafluoropiperidine as terminal groups: Syntheses and properties as new liquid crystals

A new class of liquid crystals was synthesized with N-heterocycles as the terminal group, such as Piperidine or 3,3,4,4,5,5-hexafluoropiperidine. Some of these new N-heterocycles liquids crystals displayed broad mesophase range, high clearing points, good thermal stabilities, which can be used as new components in the LCDs. •Novel compounds with piperidine as end group have been synthesized.•Some compounds display broad mesophase ranges, high clearing points.•The influence of fluorine content on mesomorphic behavior was investigated. A series of novel ester liquid crystals with piperidine or 3,3,4,4,5,5-hexafluoropiperidine as terminal group have been prepared in good yield. Some of the new compounds show broad mesomorphic phase range and good thermal stability. Their structures were modified by varying the terminal N-heterocycles, lateral fluorine substituent on the benzene ring, and the number of the cyclohexane ring in the molecules. The compounds 3/2-0F, 5/2-0F and 3/2-1F exhibited nematic phase (N), and 5/2-1F displayed smectic B phase. Compared with compound 3/2-1F (N), 5/2-1F has a longer n-pentyl substituent on the cyclohexane ring. Variation of the terminal N-heterocycles from piperidine to 3,3,4,4,5,5-hexafluoropiperidine causes the absence of mesomorphism behaviors.