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.

Potentiometrie examination of complexation equilibria of some phenoxyacetic acid derivatives with Cu(II), Cd(II) and Zn(II)

“…Calculations of the curves q exp and q cal ¼ fðpHÞ were carried out for the different metalyligand ¼ 1y5 and 1y10 ratios. The data processing using the method of least squares coupled with the pit-mapping method (Albourine, 1989) was carried out using the NEWSI Program.…”

Potentiometric examination of ternary complexes of 2,4-D and 2,4-MCPA, components of a weedkiller, with Cu2+, Cd2+, Hg2+, Pb2+and Zn2+, and a quantum approach to their structures

“…Experimental data were computed by the use of the NEWSI and NEWMI programs derived from the LETRAGROP program which was modified and tested in our laboratory to study a number of the equilibria (Albourine et al, 1989;Albourine et al, 1993;Albourine et al, 2002;M'boungou et al, 1989;Lucas Vas, 1997). These programs make possible the refinement of the parameters by juxtaposition of a least square method and a pit mapping method.…”

Potentiometric and quantum studies of the speciation of phenoxyacetic acids in the presence of mercury (II) and of lead (II)

“…These calculations are reported for several complex compositions, and the set of complexes that is really present will give the lowest values of U min and s 2 ( q q). The potentiometric method has been widely described elsewhere and more details will be found in the literature (Lucas Vaz, 1996;Albourine et al, 1991;Albourine et al, 1989;Albourine et al, 2002).…”