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

In this work, the ternary complex formation between vanadium(III), salicylic acid (H2Sal) 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)-H2Sal-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.