Synthesis and thermotropic liquid-crystalline properties of a hexyloxy-substituted pyridyl-ethynylene-azobenzene and its halogen-bonded complex with tetrafluoroiodophenyl decanoate

Abstract This work deals with the synthesis and thermotropic behavior of a hexyloxy-substituted pyridyl-ethynylene-azobenzene and its halogen-bonded complex (XB complex) with tetrafluoroiodophenyl decanoate. The XB complex here reported is a highly anisotropic photoactive mesogen. It displays only smectic-type order where two different lamellar stacks seem to co-exist. The smectic period (determined by XRD) shorter than the theoretical length of the XB-complex suggests a single layer stacking of molecules, which may be arranged head-to-tail to satisfy the electrostatic interactions between fluorinated and non-fluorinated rings. Finally, photo-isomerization and NMR experiments seem indicate that the halogen-bonded complex is stable in solution.