Studies on the Stabilities of Some Mixed Ligand Complexes of Lanthanide(III) Ions

Abstract

Ternary complexes of lanthanides with CPTA as primary and
quinaldic acid as a secondary ligand having the general formula
[M-CPTA-quinaldic acid) where M = La(III), Sm(lll), Eu(lII),
Gd(III) and Dy(III) have been described potentiometrically at different
temperatures and at constant ionic strength  μ = 0.2 M
(KNO₃) using the modified Irving and Rossotti's method. The thermodynamic
parameters for the formation of the complex [M-CPTA-quinaldic-
acid] have also been calculated. The stability constants
show the following order
Dy³⁺ < Sm³⁺ = La³⁺ < Eu³⁺ < Gd³⁺