Coordination properties of tridentate (N,O,O) heterocyclic alcohol (PDC) with Cu(II): Mixed ligand complex formation reactions of Cu(II) with PDC and some bio-relevant ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(PDC)L (PDC = 2,6-bis-(hydroxymethyl)-pyridine, HL = amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(PDC)L, Cu(PDC, H−1)(L) and Cu(PDC, H−2)(L) complexes. The concentration distribution of the complexes in solution is evaluated as a function of pH. The effect of dioxane as a solvent on the protonation constant of PDC and the formation constants of Cu(II) complexes are discussed. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants are investigated.