Thermodynamics of the complexation of piperazine-N,N-di-β-propionic acid dihydrochloride with cobalt(II), nickel(II) and copper(II)

Abstract Potentiometric studies on the chelation of Co(II), Ni(II) and Cu(II) with piperazine- N,N -di-β-propionic acid dihydrochloride as as a ligand were carried out in aqueous solution. The effects of the variation of ionic strength and temperature on the proton-ligand and metal-ligand thermodynamic stability constants were calculated. The stability constants of the complexes increase in the order Cu(II) > Ni(II) > Co(II). The thermodynamic parameters Δ H ≠ , Δ S ≠ and Δ G ≠ for the chelation processes were also evaluated. The values of these parameters are discussed in terms of the metal ion present.