Formation of Mixed-Ligand Complexes of Metals(II) with Monoamine Complexones and Amino Acids in Solution

The formation of mixed-ligand complexes in the M(II)–Nta, Ida–L (M = Cu(II), Ni, Zn, Co(II), L = Ser, Thr, Asp, Arg, Asn) systems, where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, respectively, is studied using pH measurements, calorimetry and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of their formation at 298.15 K and ionic strength I = 0.5 (KNO₃) are determined. The most likely scenario of amino acid residue coordination in the composition of mixed complexes is discussed.