Synthesis and mesomorphic properties of mesogens containing (4-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl groups

Due to the activation of fluorine atoms in aromatic rings by four other flu orine atoms and a 4-ethynyl bond, polyfluoroalkoxy chains can be introduced into aromatic rings by direct nucleophilic substitution reaction using pot assium carbonate as base to prepare 4-polyfluoroalkoxy-2,3,5,6-tetrafluorop henylacetylenes. Seven compounds containing (4-polyfluoroalkoxy-2,3,5,6-tet rafluorophenyl)ethynyl groups have been prepared by catalytic reaction usin g bis(triphenylphosphine)palladium dichloride and copper(I) iodide as catal ysts. Mesomorphic properties of target compounds were investigated by optic al polarizing microscopy and differential scanning calorimetry (DSC). Mesop hases were devalued by highly fluorinated alkoxy terminal chains compared w ith similar compounds whose terminal chains were not highly fluorinated. (C ) 2001 Elsevier Science B.V. All rights reserved.