Distortion of the coordination polyhedron in mononuclear copper(II) complexes. Optical absorption and electron spin resonance studies on some five-coordinate copper(II) complexes

Abstract

The preparation and spectral properties are reported for a series of ten mixed-ligand copper(II) complexes of the form [Cu( A)( B) n ]( X), where A is acetylacetonate anion, B represents a mono- or bidentate ligand such as morpholine, piperidine, isonicotinic acid hydrazide, 2,2′-bipyridine, 1,10-phenanthroline and X is variously NO − 3 or ClO − 4 anion and n = 1 or 2. The coordination of the anions and ligands has been demonstrated by infrared and electronic spectral methods. Electron spin resonance spectral data show the square-pyramidal five-coordinated arrangement around copper(II) in these complexes. Parameters such as g ‖, g ⊥, A ‖, A ⊥, 〈 g〉 and 〈 A〉 calculated from electron spin resonance data in solid and solution state at room temperature as well as frozen solution indicate the presence of the unpaired electron in the d x 2 − y 2 or d z 2 orbital. These results are in good agreement with electronic and photoacoustic spectral studies.