X-ray Absorption Study of Copper(II)−Glycinate Complexes in Aqueous Solution

The structures of the mono-, bis-, and tris(glycinato)copper(II) complexes in aqueous solution have been determined by X-ray absorption spectroscopy. Four solutions with different complex ratios have been examined, and the species concentrations have been determined on the basis of complex stability constants. An advanced data analysis including multiple-scattering effects and multielectron excitation processes produced quantitative information on the Cu(II)−glycinate complexes present in aqueous solution. The structure of the bis(glycinato)copper(II) complex, which has a low solubility in water, has been determined for the first time. It has been found to have a distorted octahedral geometry with two bidentate glycine ligands coordinating to the Cu2+ ion in the equatorial plane and with the axial sites occupied by two additional water molecules at 2.40 ± 0.06 A. Analysis of the X-ray absorption data allowed a detailed description of the structures of the mono- and tris(glycinato)copper(II) species. The f...