Stability constants of the ternary complexes formed between vanadium(III)–salicylic acid and amino acids

Abstract In this work, the ternary complex formation between vanadium(III), salicylic acid (H 2 Sal) as primary ligand and the amino acids glycine, α-alanine, β-alanine, proline, serine, threonine, methionine and phenylalanine (HL) as secondary ligands, in aqueous solution at 25 °C using 3.0 mol·dm − 3 KCl as the ionic medium was studied. The analysis of the potentiometric data using the least squares computational program LETAGROP indicates the formation of the species [V(Sal)(HL)] + , V(Sal)(L), [V(Sal)(L)(OH)] − , [V(Sal)(L)(OH) 2 ] 2 − , [V(Sal) 2 (L)] 2 − and [V(Sal) 2 (L)(OH)] 3 − in the ternary V(III)–H 2 Sal–amino acid (HL) systems studied. The values of ∆ log K ″ for ternary systems involving amino acids have been evaluated and discussed. The species distribution diagrams as a function of pH were briefly discussed.