Copper(II) complexes of 3,3'-[Ethane-1,2-diylbis(imino)]bis(propanamide) in solution

Abstract

The interaction of copper(II) ions with 3,3'-[ethane-1,2-diylbis(imino)]bis(propanamide) (H2eip) in 0.1 mol l-l KNO3 at 25�C has been studied by means of spectrophotometry and potentiometry. The acid dissociation constants of the ligand have also been determined under the same conditions. Equilibria (1) and (2) apply to the free ligand: (H2eip)H22+KA↔(H2eip)H++H+(1) (H2eip)H22+KA↔(H2eip)H+ (2) For the copper complexes, equilibria (3)-(5) were found to hold: Cu2+H2eip↔Cu(H2eip)2+ (3) Cu(H2eip)2+↔Cu(H2eip)++H+ (4) Cu(Heip)+↔Cu(eip)+H+ (5) The values of the equilibrium constants are: pKA 5.79, pKB 8.88, log K 11.89, pK'1 8.06, pK'2 9.48. The absorption maxima and the extinction coefficients of Cu(H2eip2+ and Cu(eip) are, respectively, γmax654 nm, εmax138 cm-1 mol-1 1 and γmax 543 nm, εmax 98.6 cm-1 mol-1 l.