Synthesis and Ion Binding Properties of a p-Keto-oxime and avic-Dioxime Derivative of Calix[6]arene

A keto-oxime derivative of calix[6]arene was synthesized from 5,11,17,23,29,35-hexaacetyl-37,38,39,40,41,42-hexamethoxycalix[6]arene by oxidation of the CH3 group of the acetyl groups to isonitroso groups. The prepared compound was converted into its vic-dioxime derivative by treatment with NH2OH.HCl. The resulting ligands (2, 3) were treated with three transition metal salts (e.g., CuCl2.2H2O, NiCl2.6H2O or CoCl2.6H2O). While the Cu(II), Ni(II) and Co(II) complexes of the vic-dioxime derivative of calix[6]arene were obtained, only Co(II) gave a complex with the keto-oxime derivative of calix[6]arene. All the complexes have a metal-ligand ratio of 3:1. The Cu(II) and Ni(II) complexes of 3 are square-planar, while the Co(II) complex of both ligands are octahedral with water molecules as axial ligands.