STABILITY AND STRUCTURE STUDIES OF COPPER(II) COMPLEXES WITH POLYAMINES AND RELATED LIGANDS IN AQUEOUS-SOLUTION

Complexes of Cu(II) with a number of polyamines (en, (1,2)tn, tn, put, dien, 2,3-tri) as well as with 2,3-diaminocarboxylate (dapa) and 2,4-diamioocarboxylate (daba) anions have been studied by potentiometric and spectral methods. Stability constants as well as their coordination mode have been determined. Species of ML(x) type are found to dominate in the system where bidentate ligands form 5-membered rings with the involvement of all nitrogen atoms of the ligand, mainly in the equatorial plane. In polyamines of longer chains, besides formation of chelate complexes (with 6- and 7-membered rings), a monofunctional coordination with protonated donor atoms has been observed. Dien and 2,3-tri form ML type complexes with N3 coordination. Complexes of bidentate amines (ML(3) type) and complexes of potentially tridentate polyamines (ML(2) species) form structures with four nitrogen atoms coordinated equatorially and one or two (depending on the type of ligand) nitrogen atoms at axial positions. Similarly, in ML(2) compounds of both diaminocarboxylate ligands, 5 or 6 donor atoms are involved in coordination, however, with two dapa oxygen atoms at apical positions and mixed coordination in daba system.