Complexation equilibria of some sulphoazoxines. Part VIII. Complexes of SNAZOXS with copper(II), lead(II) and cadmium(II) ions evaluated by regression analysis of potentiometric data

Abstract

The reactions of oligomers of the sulphoazoxine SNAZOXS with H+, Pb2+, Cd2+ and Cu2+ ions were studied potentiometrically at 298 K in aqueous solutions. The protonation constants of the ligand oligomers L2H42–, L2H33–, L2H24– and L2H5– and the formation constants of several metal complexes were calculated with the aid of the program MINIQUAD. The chemical models were selected on the basis of a critical evaluation of the least-squares results and of a goodness-of-fit test by the statistical analysis of residuals. Whereas Cu2+ and Cd2+ ions form CuL–, CuLH, CuL24– and CuL2H3– complexes (Cu can be replaced with Cd), the Pb2+ ion forms PbLH, PbL24–, PbL2H3– and Pb2L35– complexes.