Ternary Complexes of Essential Metal Ions with L-Arginine and Succinic Acid in Cationic Surfactant Medium
Chemical speciation of ternary complexes MLX, ML2X and MLXH formed by Co(II), Ni(II), Cu(II) and Zn(II) with L-arginine as primary ligand (L) and succinic acid as secondary ligand (X) was studied in various concentrations (0.0-2.5% w/v) of cationic surfactant 
solution maintaining an ionic strength of 0.16 mol dm-3 
(NaNO3) at 303K. Titrations were carried out in the 
presence of different relative concentrations (M: L: X 
=1:2:2, 1:2:4, 1:4:2) of metal to L-arginine to succinic acid with sodium hydroxide as titrant. The observed extra 
stability of ternary complexes compared to their binary 
complexes was explained based on the electrostatic 
interactions of the side chains of the ligands, charge 
neutralization, chelate effect, stacking interactions and 
hydrogen bonding. The trend in log β values with mole 
fraction of the surfactant and distribution diagrams were 
presented. Structures of plausible ternary complexes were 
also presented.