Speciation studies of binary and ternary complexes formed with fe(II) ion 2,6-pyridinedicarboxylic acid and several amino acids

The chemical speciation of ternary systems involving Fe(II), 2,6-pyridinedicarboxylic acid (H₂Dipi), and various amino acids (glycine, β-alanine, α-alanine, leucine, methionine, lysine, phenylalanine, threonine, serine, proline, valine, and histidine) was investigated in this work. Potentiometric titrations were conducted for each system in aqueous solution at 25 °C using 1 mol dm⁻³ NaCl solution as the ionic medium. The resulting data were analyzed using the least-squares program LETAGROP. Additionally, the binary system of Fe(II)-2,6-pyridinedicarboxylic acid in aqueous solution at 25 °C with NaCl 1.0 mol dm⁻³ as the ionic medium was also examined. Species distribution diagrams were generated, and the relative stability parameter Δlog K was calculated.