Ionic columnar metallomesogens formed by three-coordinated copper(I) complexes

Abstract

Two series of copper(I) complexes (1, 2) derived from bis{2-[3′-(3″,4″-dialkoxyphenyl)-5′-methyl-1′-pyrazolyl]ethyl} ethers and from bis{2-[3′-(3″,4″,5′-trialkoxyphenyl)-5′-methyl-1′-pyrazolyl]ethyl} ethers were prepared and characterized. These ionic copper(I) complexes were obtained by reaction of the ethers with [Cu(MeCN)₄]BF₄ in refluxing acetonitrile. All three-coordinated copper(I) complexes isolated as off-white solids were characterized by NMR spectroscopy and elemental analysis, and their mesomorphic properties were also studied by polarized optical microscopy, differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD). Results indicated that these complexes exhibited hexagonal columnar phases (Col_h). The clearing points of all compounds were relatively low (94–112 °C) and the temperature range of the mesophases was ca. 45–68 °C. Powder XRD diffraction patterns showed three sharp reflections in the small angle region corresponding to a ratio of their positions of 1 :  (1/3)^1/2 ∶ (1/2), indicating typical hexagonal columnar phases.