Liquid-crystalline paramagnetic Cu(ll) complexes of enaminoketone ligands

Abstract

Studies of complexes: [R-C₆H₄-CO(CH)₂N-Alk]₂Cu, (I), [Alk-CO(CH)₂N-C₆H₄-R]₂Cu, (II), and [R¹-C₆H₄-CO(CH)₂N-C₆H₄-R₂]₂Cu, (III), for various terminal substituents R, R¹, R², are presented. For alkyl substituents R, complexes are low-melting and low-clearing nematics (group (I)) and smectics A (group (II)). Mesophases are monotropic for pure compounds, enantiotropic for mixtures. Elongation of molecular core by introduction trans-cyclohexyl rings into R substituents leads to enantiotropic paramagnetic mesogens. Complexes of the group (III) are high-melting and high-clearing mesogens which usually undergo decomposition in the isotropic phase. Chiral highly twisted mesophases are observed for some optically active complexes.