Mixed Ligand Complexes of Mn(II), Pb(II) and Th(IV) with Adenosine Diphosphate and Nitrilotriacetate

Abstract

A new method, paper electrophoresis, involving the use of
ionophoretic technique, is described for the study of equilibria in
mixed ligand system in solution. Migration of a metal ion spot (M),
under an electric field, with complexant added in the background
electrolyte at fixed pH 8.5, is studied. For the study of ternary
complexes, the concentration of the primary ligand adenosine diphosphate
(ADP) is kept constant while that of the secondary ligand
nitrilotriacetate (NTA) is varied. Plot of -log [NTA] against mobility
provided information about the mixed ligand complex to calculate
the stability constants. As a prerequisite, binary equilibrium M-ADP
and M-NTA have also been studied. The overall stability constants
of M-ADP-NTA complexes have been found to be 10^9.04, 10^9.72
and 10^10.49 for Mn(II), Pb(II) and Th(IV) complexes respectively
at ionic strength μ = 0.1 and temp. 30° ± 0.1 °C.