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 (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 Δ 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.