<i>p</i>H-metric and spectroscopic studies on some ternary complex systems of nickel(II)

Abstract

Equilibrium based computer models using MINIQUAD-75 computer program on eighteen ternary complex systems viz. Ni (ll)-histamine(hist)/L-histidine(his)(A)-DL-2 aminobutyric acid (2aba), DL-3- aminobutyric acid (3aba), 4-aminobutyric acid{4aba), DL-4-amino-3-hydroxybutyric acid (ahba), 1,2- diaminopropane (dp), 1,3-diaminopropane(tp), DL-2,3-diaminopropio-nic acid(dapa), DL-2,4- diaminobutyric acid(daba) and DL-ornithine(orn) (B) at 37&deg;C and <em>I</em>=0.15 mol dm^-3 (NaClO₄.) have demonstrated the formation of the ternary complex species of the type NiAB, NiABH or NiABH₂. The results suggest that the Ni (II) ternary chelates containing five and six membered chelate rings are more stable than those with six membered rings. There is a general agreement between the results obtained by the <em>p</em>H-metric and spectral measurements in the systems under investigation. In the NiABH type of species the results indicate the possibility of the attachment of the extra proton to be with the respective secondary ligand. The trends in the results for the NiABH₂ complexes indicate that one proton resides with the primary ligand and the other with the secondary ligand. The computer-simulated distribution of the complexes in solution has also been evaluated.