A spectroscopic study of solvent effects on the formation of Cu(ii)–chloride complexes in aqueous solution

Abstract

A combination of electronic (UV-vis) and X-ray absorption (EXAFS, XANES) spectroscopies has been used to investigate the formation of copper(II)/chloride complexes in concentrated aqueous solutions. It is established that lowering the water activity by the addition of Mg(ClO₄)₂ at a constant Cl⁻/Cu(II) ratio results in the replacement of water molecules by Cl⁻ ions in the primary coordination shell of Cu(II). This behavior closely parallels the effect of increasing the Cl⁻/Cu(II) ratio and demonstrates that full understanding of the stoichiometry and structures of the complexes formed in concentrated metal-ion chloride solutions requires explicit consideration of the role of the solvent.