Tolane liquid crystals with piperidine, 3,3,4,4,5,5-hexafluoropiperidine as end group: Synthesis and properties

Article abstract of DOI:10.1016/j.molliq.2015.01.043

A series of new tolane liquid crystals with piperidine and 3,3,4,4,5,5-hexafluoropiperidine as their terminal groups were synthesized via Sonagashira reaction by using Pd(PPh₃)₂Cl₂/CuI as the catalyst. Their structures were modified by varying the terminal N-heterocycles and/or the length of the alkyl/alkoxy chains on the benzene ring. Most of these new compounds exhibit Smectic B or G mesophases, good thermal stabilities and high clearing points. The molecule C₂H₅O6F with 3,3,4,4,5,5-hexafluoropiperidine as the end group has a broader HOMO-LUMO energy gap and higher oxidation potential than piperidine derivative C₂H₅O6H. The result indicates that the oxidation resistance of the tolane liquid crystals was improved by introducing the terminal fluorinated piperidine.