The spectroscopic and structural properties of copper(II) complexes of the novel tridentate (ONO) pyridine N-oxide ligand Hpoxap

Abstract

A tridentate ligand (Hpoxap=2-( o-hydroxyphenyliminomethyl)pyridine N-oxide) has been synthesised by the Schiff condensation of 2-pyridinecarboxaldehyde N-oxide with 2-aminophenol. A series of copper(II) complexes with this ONO-donor ligand has been prepared and their spectroscopic properties (electron, vibration, ESR) were studied. The structures for two complexes have been determined by X-ray analysis. The structure of [Cu(poxap)(OAc)] consists of isolated neutral molecules in which the copper(II) atom is situated in a slightly distorted square-planar surrounding. The structure of [Cu(poxap)(H 2O)(NO 3)] consists of neutral molecules which are interconnected by hydrogen bonds giving rise to a ladder structure of copper(II) ions with two different Cu⋯Cu distances of 5.27 and 7.41 Å. The copper atoms are in a slightly distorted square-pyramidal environment with the tridentate ligand poxap − and the water molecule in the basal plane; the apical position being occupied by an oxygen atom of the nitrate anion. Magnetic susceptibility studies were undertaken and these confirm predominantly a dimeric character of the complex.