Ternary complex formation between vanadium(III) cytosine and some amino acids

Abstract

In this work we present the results of the speciation of the ternary vanadium(III)–Cytosine (HCyt) complexes with the amino acids Glycine (HGly), Proline (HPro), α-Alanine (HαAla) and β-Alanine (HβAla), studied by means of electromotive force measurements emf (H) using 3.0mol.dm−3 KCl as the ionic medium at 25°C. The experimental data were analyzed by means of the computational least-squares program LETAGROP, taking into account the hydrolysis of the vanadium(III) cation and the respective stability constants of the binary complexes and the acid base reactions of the amino acids which were kept fixed during the analysis. In the binary vanadium(III)–Cytosine system the formation of the complexes [V(HCyt)]3+, [V(Cyt)]2+, [V(Cyt)(OH)]+, V(Cyt)(OH)2, [V(Cyt)2]+ and V(Cyt)3 was observed. In the ternary systems studied were observed the complexes with the amino acids Glycine, Proline and β-Alanine [V(HCyt)(HL)]3+, [V(Cyt)(HL)]2+, [V(Cyt)(L)]+, V(Cyt)(L)(OH) and [V(Cyt)(L)(OH)2]− were HL represent the neutral form of the amino acid, with α-Alanine were detected the ternary complexes [V(HCyt)(HL)]3+, [V(Cyt)(HL)]2+, [V(Cyt)(L)]+, V(Cyt)(L)(OH). The species distribution diagrams as a function of pH were briefly discussed.