Thermodynamic parameters of imidazole containing mixed ligand complexes of nickel (II)

Abstract

Equilibrium based computer models have been utilized to determine the stoichiometry and thermodynamic stability constants in the mixed ligand complex systems viz, Ni (II) - imidazole (him) I benzimidazole (bim) (A) -DL-2-aminobutyric acid (2 aba), DL-3- aminobutyric acid (3 aba), 4-aminobutyric acid (4 aba), DL-4- amino-3-hydroxybutyric acid (ahba), 1,2-diamino-propane (dp), 1,3-diaminopropane (tp), DL-2,3-diaminopropionic acid (dapa), DL-2, 4-diarninobutyric acid (daba) and DL-ornithine (orn) (B). The results indicate the tridentate binding of dapa and daba ligands in their complexes. The mode of coordination of other ligands under investigation is same both in the binary and mixed ligand complex species. It appears that the relative stabilities of NiAB and NiA2B complexes depend upon the size of the chelate ring formed by the secondary ligand, B. Higher stabilities have been noted for Ni (II) complexes containing him primary ligand compared to the bim primary ligand systems.