Complexes binaires et ternaires du cuivre(II) avec la 1-canavanine et la 1-arginine examinés par potentiométrie, spectrophotométrie visible et dichroïsme circulaire

Abstract

The protonation constants of 1 -canavanine (Can) and its structural analogue 1-arginine (Arg) have been calculated at 25 °C and at ionic strength μ = 0.1 (NaNO3). Under the same conditions, the stability constants of the binary and ternary complexes with Cu(II) have been determined by potentiometry, spectrophotometry, and by circular dichroïsm in the visible region. A comparative study of these two amino acids allows us to differentiate the order of protonation of the three functional groups (carboxylic, amino, and guanidyl), mainly by the different modes of complexation with copper(II), which is found in an octahedral coordination: arginine behaves like a bidentate ligand (glycine type) whereas canavanine behaves like a tridentate ligand. Keywords: 1-arginine, 1-canavanine, circular dichroïsm, copper ternary coordination, potentiometry.