Influence of Electronic Effects of Radicals of Some Aliphatic Amino Acids on Complexing Properties with Silver(I) Ions in Aqueous Solutions

The complexation of silver(I) ions with serine (Ser), glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), and isoleucine (Ile) in aqueous solutions at T = 298.2 K and I = 0.1 mol/L NaNO3 was studied using a potentiometric method. It was determined, that in these systems, silver(I) ions form complexes of the composition AgLo and AgL₂⁻ with the aliphatic amino acids used. Based on the calculated numerical values of the protonation constants of individual aliphatic amino acids, as well as the stability constants of the complexes formed from them, patterns in the influence of the electron effects of amino acid side chains on the stability of complex particles in aqueous media were established. It was found that the stability of the resulting complexes changes as follows: AgSer₂⁻ < AgGly₂⁻ < AgLeu₂⁻ < AgAla₂⁻ < AgIle_2\;⁻ < AgVal₂⁻. It was also found that the presented dependence of the stability constants of silver complexes of the indicated amino acids correlates well with the change in the protonation constants of the individual ligands.