Mixed-ligand complex formation equilibria of nickel(II) with picolinic acid and some amino acids (glycine, α-alanine, β-alanine, and proline) studied in 1.0 mol·dm− 3 NaCl at 25 °C

Solution equilibria of the systems Ni(II)-Picolinic acid (HPic)- and the amino acids Glycine (HGly), Proline (HPro), α-alanine (HαAla) and β-alanine (HβAla) have been studied pH-metrically. The formation constants of the resulting mixed ligand complexes have been calculated at 25 °C and ionic strength 1.0 mol·dm− 3 NaCl. Ternary complexes are formed by simultaneous reactions. The relative stability of each ternary complex was compared with that of the corresponding binary complexes in terms of Δ log K″ values. Specie distribution diagrams as a function of pH were briefly discussed.