Electron spin resonance and optical resonance studies on copper(II) complexes with vanadate, molybdate and tungstate anions

Abstract

A series of complexes of the form Cu(An) n L x · yH 2O, where An = vanadate, molybdate or tungstate anion, L = pyridine, α-, β- or γ-picoline, n = 1 or 2; x = 1−4 and y = 0−3, have been synthesized and characterized by electron spin resonance, photoacoustic and electronic spectral studies as well as infrared spectroscopy in the solid and solution state. The different coordination sites of the ligands and anions have been interpreted from infrared and electronic spectral data. Electron spin resonance spectral data show the square planar or distorted octahedral (in a few cases five-coordinate geometry) stereochemistry around copper(II) in these complexes. Parameters such as g ∥, g ⊥, A ∥, A ⊥, 〈 g〉, 〈 A〉, α 2 and β 2 1 calculated from electron spin resonance data indicate the presence of unpaired electrons in d x 2− y 2 or d z 2 orbitals. The results of electronic and photoacoustic spectral studies are in good accord with ESR data.