Equilibrium Studies on Some Ternary Complexes of Cu(II) with 1,3-Diamino Propane as Primary Ligand and O-O Donor Atoms as Secondary Ligands and its Comparison with Binary Complexes

Abstract

The formation constants of the mixed ligand complexes (CuAL) at 1 : 1 : 1 optimum molar concentration of metal as Cu(II); primary ligand, A = 1,3-diamino propane (1,3-DiaP) and O-O donor atoms as secondary ligand, L = salicylic acid, DL-malic acid, DL-mandelic acid, DL-lactic acid have been determined by modified form of Irving-Rossotti titration technique in aqueous media at constant
ionic strength μ = 0.2 M dm^–3 at 30 ± 0.1ºC. The difference between
the stability of ternary complexes and the corresponding binary
complexes has been expressed in terms of parameter
Δlog K_T. The stabilities of the ternary complexes are explained in
terms of π-basicities, structures of secondary ligand and ring size
of chelate. Δlog K_T values are negative which suggests favourable
formation of ternary complexes. The variations of Δlog K_T have
been explained in terms of M → L π-interaction, size of the chelate
ring and steric factors.