Solution Equilibria of Ternary Systems Involving Transition Metal Ions, Hydroxamic Acids, and Bioligands

Abstract

The formation of ternary complexes of the Cu(II), Co(II), Ni(II), and Zn(II) metal ions with some hydroxamic acids (acetohydroxamic acid, Aha; benzohydroxamic acid, Bha; salicylhydroxamic acid, Sham; and N-phenylbenzohydroxamic acid, N-PhBha) and some bioligands (α-alanine, α-ala; l-valine, l-val; norvaline, norval; aspartic acid, aspart; glutamic acid, glut; asparagines, asperg; histamine, Him; and imidazole, imid) was investigated using the potentiometric technique at 25 °C and I = 0.10 mol·dm−3 NaNO3. The stability constants of these ternary systems were calculated. The order of stability of the ternary complexes in terms of the nature of metal ions, hydroxamic acids, and bioligands was investigated and discussed as well as the values of Δ log K and log X for the ternary systems. The concentration distribution curves of the various binary and ternary complex species in solution were evaluated. The effect of temperature of the medium on both the ionization process of Aha, Sham, aspart, and glut and the complex formation with Cu(II), Co(II), and Ni(II) for 1:1:1 ternary systems in the range of (15 to 45) °C and I = 0.10 mol·dm−3 NaNO3 in an aqueous medium has been studied. The thermodynamic parameters are calculated and discussed. Evaluation of the effect of ionic strength was carried out in NaNO3 as a supporting electrolyte I [(0.10 to 0.50) mol·dm−3]. The dependence on ionic strength of the stability constants of the binary and ternary complexes was analyzed. In addition, the chelation mode of the ternary complexes was ascertained by conductometric titrations. Also, confirmation of the formation of ternary complexes in aqueous solutions has been done using cyclic voltammetry measurements.

Binary Complexes of Aspartic Acid with Some Metal Ions in Aqueous Solution and Water-dioxane Mixtures

“…Negative ∆H°s conveys that the reactions are exothermic, and negative ∆S° are the indication that the complexes are more organized than the reactants. Some workers have conducted research on complex systems of mixed ligands as ternary complexes with transition metal ions which needed sophisticated softwares and more rigorous treatment of data [47][48][49][50][51].…”