Polarographic Studies on Mixed-Ligand Complexes of Lead(II) with DL-3-(3-,4-Dihydroxy Phenyl) Alanine and Some Dicarboxylic Acids

Abstract

The polarographic reduction of lead(II) in the aqueous solution
of DL-3-(3,4-dihydroxy phenyl) alanine (DL-DOPA) and some dicarboxylic
acids (maleate and succinate) has been carried out. The
stability constants have been determined for the simple Pb-DOPA
system first, and then the mixed-ligand complexes of lead with
DOPA and dicarboxylic acids (maleate and succinate) have been
studied polarographically. The stability constant of mixed-ligand
complexes have been determined by the method of Schaap and
McMasters at 303 ± 3 K and ionic strength of 1.0 M. For the comparison
of the stability of simple and mixed complexes, the mixing
constant (K_m) and stabilization constant (K_s) have been measured.
The positive values of the mixing constants and stabilization constants
show that the ternary complexes are more stable than the
binary complexes.