A critical examination of the interaction between copper(II) and glycylglycyl-L-histidine

Abstract

The equilibria involved in the copper(II)-glycylglycyl-L-histidine (HL) system have been re-examined by analytical potentiometry in 0.15 mol dm^–3 NaCl solution at 25 °C. The species found are MH₂L, MHL, ML, MH_–1L, MH_–2L, MH₂L₂, MHL₂, ML₂, MH_–1L₂, and MH_–2L₂, with log stability constants 16.72, 11.78, 7.55, 2.68, –1.92, 25.81, 20.64, 16.68, 9.73, and 1.43 respectively. The visible absorptions of the total system have been measured at discrete pH values. The spectroscopic characteristics of the predominant species MH_–1L, MH_–2L, ML₂, MH_–1L₂, and MH_–2L₂ are computed. The combined potentiometric–spectroscopic analysis has helped to clarify the system in greater detail.