Synthesis and properties of novel 6,7-dihydrocyclopenta[5,6-b]benzofuran-based liquid crystal compounds

Abstract

ABSTRACT A novel liquid crystal core unit 6,7-dihydrocyclopenta[5,6-b]benzofuran was designed and three different kinds of liquid crystals 2MUF, 2MP4, 2MYO2 were synthesised through a facile route which employed palladium-catalysed cascade Sonogashira coupling/cyclisation as a key step. Initially, density function theory calculation illustrated that a compound based on this new unit possessed almost a linear structure. The mesophase and physical properties of these novel compounds were measured and the impacts of the newly designed core unit on these properties were investigated by comparing with two series of analogous materials which contained classical mesogenic cores 1,4-disubstituted benzene and trans-cyclohexyl benzene, finding that the introduction of 6,7-dihydrocyclopenta[5,6-b]benzofuran into liquid crystals tended to promote the formation of nematic phase while increasing both the melting points and the clearing points of target molecules. Meanwhile, the newly synthesised liquid crystals presented higher birefringences when compared with their corresponding reference compounds, indicating that 6,7-dihydrocyclopenta[5,6-b]benzofuran can be a hopeful candidate for the construction of high birefringence liquid crystals.