Zinc(II) trinuclear complexes involving pyridine N-oxide ligands: distortion isomerism and magnetic properties of copper(II) analogues

The Schiff condensation of the 2-pyridinecarboxaldehyde N-oxide with 2-aminophenol yielded a tridentate ligand, abbreviated as Hpoxap. This ligand is a base of a series of mononuclear complexes [M(poxap)2] and trinuclear complexes of the type [M(poxap)MX4M(poxap)], where X is an acetate or chloro bridge. The X-ray structure of the complex [Zn(poxap)Zn(OAc)4Zn(poxap)]·H2O has been determined: this complex forms a pair of distortion isomers differing slightly in bond lengths and bond angles within the chromophores. The copper(II) doping gave mixed crystals suitable for the ESR spectroscopy (g‖=2.282, g⊥=2.016, A‖=135 G, A⊥=26 G). The magnetic susceptibility of an analogous [Cu(poxap)CuCl4Cu(poxap)] trinuclear complex at low temperature indicates a slight antiferromagnetic interaction (JCuCu/hc=−5.2 cm−1, gCu=2.285).