Multimetal multiligand complex formation equilibria of copper(II), nickel(II) and zinc(II) with iminodiacetic acid and L-pyrrolidine-2-carboxylic acid in aqueous solution

Solution equilibria of homo and heterobinuclear complexes of Cu-II, Ni-II and Zn-II with iminodiacetic acid (IMDA A(2-)) and L-pyrrolidine-2-carboxylic acid (proline = B-) as ligands have been investigated by pH-measurements in an aqueous medium and relevant stability constants have been evaluated using computer technique. The stability constants of binary, ternary and quaternary complexes are determined at 35 +/- 1 degrees C and at I = 0.1 mol dm(-3) (NaNO3). Complexes of the type [M-2(A)(2)(B)](-) and [(MM2)-M-1(A)(2)(B)](-) have been detected along with the various binary and ternary species. The observed order of the stability constants and probable solution structure of homobinuclear complexes have been discussed.