Synthesis and low dimensional conductive behaviour of columnar bis(beta-diketonato)copper(II) complexes with oligo(ethylene oxide) groups

Several kinds of beta-diketone with oligo(ethylene oxide) groups and their Cu-complexes were synthesized and characterized by ¹H NMR, IR, MS, and elemental analysis. The columnar mesomorphism of the bis [1-(p-ethoxy-di(ethyleneoxy)phenyl)-3-(p-n-hexyloxylphenyl)propane-1,3-dionato]copper(II) complex (abbreviated as C₆EDK-Cu) was studied by differential scanning calorimetry, polarizing optical microscopy and temperature variable X-ray diffraction. In comparison with the conductivity value of c. 10^-8 S cm^-1 of the pure columnar liquid crystal (C₆EDK-Cu), that of C₆EDK-Cu doped with LiClO₄ or iodine is increased by about three orders of magnitude and reaches 10^-5 S cm^-1 when heated to the columnar mesophase. It is noteworthy that the conductivity of C₆EDK-Cu doped with iodine is maintained when the sample is cooled from the mesophase to room temperature, while that of C₆EDK-Cu doped with LiClO4 is decreased. The two kinds of conductive mechanism of C₆EDK-Cu doped with LiClO4 or iodine are discussed.