Complexation Equilibria and Determination of Stability Constants of Binary and Ternary Complexes with Ribonucleotides (AMP, ADP, and ATP) and Salicylhydroxamic Acid as Ligands

The binary and mixed ligand complexes of some transition and alkaline earth metal(II) ions with adenosine-5‘-mono-, -di-, and triphosphate and salicylhydroxamic acid were studied using potentiometric pH titrations. The Irving and Rossotti technique has been adopted to determine the formation constants corresponding to the various complexation equilibria. The acidity constants of the ligands were measured and used for determining the stability constants of the complexes formed in aqueous solutions under the experimental conditions (t = 25 °C, I = 0.1 mol dm-3 NaNO3). The formation of 1:1:1 ternary complexes is inferred from the potentiometric titration curves. The order of stability of the binary or ternary complexes in terms of the nature of the nucleotide is investigated and discussed. The values of Δ log K for ternary systems were evaluated and discussed.