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Stability of Zn2+, Mn2+, VO2+ and Co2+ Binary and Ternary Complexes with 2,3-Dimercaptosuccinic Acid (DMSA) as a Primary Ligand and Some Biologically Important Amino Acids as Secondary Ligands

Nisha Agrawal, Richa Gupta and K. C. Gupta

The mixed ligand complexes of some transition metal ions (Zn2+, Mn2+, VO2+ and Co2+) with 2,3- dimercaptosuccinic acid (DMSA) as a primary ligand and some biologically important amino acids (hippuric acid and sarcosine (N-methylglycine) as secondary ligands and binary complexes of these metal ions with hippuric acid and sarcosine were studied potentiometrically in aqueous medium. Acid dissociation constants of the ligands used and the formation constants of the binary and the ternary complexes were determined at 30oC, 40oC, 50oC and at ionic strength μ = 0.2 mol dm-3 (KNO3). The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of Δ log K. The thermodynamic parameters like free energy (Δ Go), enthalpy (Δ Ho) and entropy (Δ So) have also been calculated.