Speciation of the Ternary Cobalt(II) Picolinic and Dipicolinic Acid Complexes with Small Bioligands

This study reports on the determination of stability constants for ternary cobalt­(II) complexes using primary ligands, pyridine carboxylic acids (picolinic (HPic) and dipicolinic (H2Dipic) acids), along with secondary ligands: lactic acid (HLac, HL), oxalic acid (H2Ox, H2L), citric acid (H3Cit, H3L), and phosphoric acid (H3PO4, H3L). Potentiometric data for binary cobalt­(II) bioligand complexes and ternary cobalt­(II) pyridine carboxylic acid and bioligand complexes were analyzed using the computational program LETAGROP. The experiments were conducted in an ionic medium of 1.0 mol dm–3 NaNO3 at 25 °C. Species distribution diagrams were generated, and relative stability parameters Δlog10 K, log10 X, and % R.S. were calculated. These findings may have important implications for the design of new cobalt­(II) complexes for various applications.