Electron spin resonance studies of copper(II) hydroxy-carboxylic acid chelates in aqueous and non-aqueous solutions

Abstract

The theory of the electron spin resonance of dipolar coupled copper(II)–copper(II) pairs has been critically assessed and extended to take into account ΔM= 2 transitions that are observed experimentally. Computational procedures have been evolved to determine the copper(II)–copper(III) separation in dimeric species. The existence of such species has been shown in both aqueous and non-aqueous solutions of the copper(II) chelates of citric, malic, tartronic, mandelic, and 5-sulphosalicyclic acids. The computational procedures have been applied to calculating and comparing the electron spin resonance signal line-shape for the dimeric species with that obtained experimentally, leading to a selection of the values of the parameters involved which includes the copper(II)–copper(II) separation. With this information, structures have been proposed for the various dimeric species.