Potentiometric and spectroscopic study of the equilibria in the aqueous copper(II)–3,6-diazaoctane-1,8-diamine system and an equilibrium-di-alysis examination of the ternary system of human serum albumin–copper(II)–3,6-diazaoctane-1,8-diamine

Abstract

3,6-Diazaoctane-1,8-diamine (L, trien) has been obtained by a new purification method, and used in a combined potentiometric and spectroscopic study of the total species formed with Cu^II(M) in 0.15 mol dm^–3 NaCl solution at 25 °C over the range pH 3.0–10.0. The species found are MHL, MH_–1L, ML, MH₄L₂, MH₃L₂, and ML₂, with log stability constants 23.76, 9.39, 20.01, 52.78, 48.52, and 22.87 respectively. The concentrations of the species, over the range pH 3.0–10.0, and their spectroscopic characteristics have been determined. Equilibrium-dialysis studies of the ternary systems: albumin–copper(II)–ligand (ligand = 3,6-diazaoctane-1,8-diamine or D-penicillamine) have been carried out in 0.15 mol dm^–3 NaCl solution, pH 7.47, at 6 °C, to measure the amounts of low-molecular-weight membrane-diffusable copper(II) species formed. There is a substantial difference between the two ligands in this respect which correlates with their different clinical behaviour when used in the treatment of patients having Wilson's disease.