Stability constants of vanadium(III) complexes with 1,10-phenanthroline and the amino acids phenylalanine, methionine, serine and threonine

Abstract

In this work we report a study of ternary complexes of V(III) with 1,10-phenanthroline (Phen) and the amino acids phenylalanine (Phe, HL), methionine (Met, HL), serine (Ser, HL) and threonine (Thr, HL) in aqueous solution with an ionic medium of 3.0 mol/L KCl at 25 °C. The systems were studied by electromotive force (emf(H)) measurements. Analysis of the potentiometric data with the least-squares program LETAGROP indicates formation of complexes of the type VHL, V(Phen)(L)(OH)2, [V2O(Phen)(L)]3+ and [V2O(Phen)2(L)2]2+ in all the systems studied. The species distribution diagrams are briefly discussed. Also, the dimer [V2O(Phen)(L)]3+ was characterized by UV-Vis spectroscopy.