Binary and ternary copper(II) complexes with aspartic acid (H 2 Asp), serine (HSer), and valine (HVal) were prepared by electrochemical and chemical procedures. The purity of the compounds was confirmed by elemental and thermogravimetric analyses. According to the IR spectra, all the complexes contain a five-membered chelate ring in which the Cu(II) atom is bonded with the oxygen atom of the carboxy group and nitrogen atom of the amino group. This is also confirmed by the ESR spectra.Complexation of natural amino acids as components of proteins is of undoubted interest [1]. It is particularly urgent to study mixed-ligand complexes, since real biological systems simultaneously contain several substances capable of complexation with a metal ion. For example, it is known [2] that mixedligand complexes involving two amino acids play an important role in metal transport.Copper is an essential trace element in a human body [3]; the majority of Cu(II) ions in blood plasma are in the form of mixed complexes with amino acids, peptides, and other biomolecules [4]. A series of mixed-ligand Cu(II) complexes with amino acids in solution were studied by polarography [5], UV spectroscopy [6], circular dichroism spectroscopy [7], ESR [8], potentiometry [6, 9311], and voltammetry [12]; their stability constants were determined, and their structure in solution was discussed.Examination of properties of solid mixed-ligand complexes can reveal relationships between the bioactivity of a compound and its composition and structure. Despite numerous papers concerning complexation of Cu(II) ions with amino acids, the structure and properties of solid binary and ternary compounds are studied insufficiently. This may be caused, in particular, by the fact that it is difficult to prepare and isolate these compounds pure. Previously [13,14] we suggested a procedure for anodic synthesis of binary compounds of d elements with various organic ligands, showing advantages as compared to common chemical synthesis of these compounds. We determined the range of potential difference between the electrodes of the electrochemical cell, at which the compounds could be prepared in high yields (90 3 95%) without side anodic processes.The goal of this study was to examine the possibility of electrochemical synthesis of mixed-ligand complexes in various media, to compare the results with those yielded by chemical synthesis, and to determine the physicochemical properties of the complexes.We found that pure organic solvents (acetonitrile, ethanol, dioxane, dimethylformamide, dimethyl sulfoxide) are unsuitable for electrochemical synthesis, because amino acids are poorly soluble in them.Evaluation of the solubility of 1 : 1 amino acid mixtures (H 2 Asp3HVal, H 2 Asp3HSer) in aqueousorganic solvents showed that acceptable solubility (~0.05 M) is provided by water3ethanol (60 390% alcohol) and water3dioxane (80 390% dioxane) mixtures. When amino acids are taken in a 1 : 1 ratio, the relative content of the CuLL`species in the nearelectrode space is several times...