Formation of disordered hexagonal arrangements in bis(β,δ-triketonato)copper(II) complexes

Abstract

Two homologous series of 1-(4-alkoxy-2-hydroxyphenyl)-3-(3,4,5-trialkoxyphenyl)propane-1,3-diones and 1-(2-hydroxyphenyl)-3-(3,4,5-trialkoxyphenyl)propane-1,3-diones were prepared by base-catalysed rearrangement of 4-alkoxy-2-(3,4,5-trialkoxybenzoyloxy)acetophenones and 2-(3,4,5-trialkoxybenzoyloxy)acetophenones, respectively. The reaction of these β,δ-triketones with copper(II) acetate gave liquid-crystalline dicopper complexes, bis[1-(4-alkoxy-2-hydroxyphenyl)-3-(3,4,5-trialkoxyphenyl)propane-1,3-dionato]- and bis[1-(2-hydroxyphenyl)-3-(3,4,5-trialkoxyphenyl)propane-1,3-dionato]-copper(II). These copper complexes exhibit disordered hexagonal columnar (D_hd) mesophases which were identified by DSC analysis and polarized optical microscopy, and were also confirmed by X-ray powder diffraction. The variable-temperature EPR spectra were also studied.