Study of the Ternary Complex Formation Between Vanadium(III)-Picolinic Acid and the Amino Acids: Cysteine, Histidine, Aspartic and Glutamic Acids

Abstract

The complex species formed between vanadium(III)-picolinic acid (HPic) and the amino acids: cysteine (H2Cys), histidine (HHis), aspartic acid (H2Asp) and glutamic acid (H2Glu) were studied in aqueous solution by means of electromotive forces measurements emf(H) at 25 °C and 3.0 mol⋅dm−3 KCl as ionic medium. Data analysis using the least-squares program LETAGROP indicates the formation of ternary complexes, whose stoichiometric coefficients and stability constant were determined. In the vanadium(III)-picolinic acid-cysteine system the model obtained was: [V(Pic)(H2Cys)]2+, [V(Pic)(HCys)]+, V(Pic)(Cys) and [V2O(Pic)(Cys)]+. The vanadium(III)-picolinic acid-histidine system contained the following complexes: [V(Pic)(HHis)]2+, [V(Pic)(His)]+, V(Pic)(His)(OH) and [V(Pic)2(HHis)]+. In the vanadium(III)-picolinic acid-aspartic acid system the model obtained was: V(Pic)(Asp), [V(Pic)(Asp)(OH)]− and [V2O(Pic)(Asp)]+ and finally, in the vanadium(III)-picolinic acid-glutamic acid system the complexes: V2O(Pic)2(HGlu)2, V(Pic)(HGlu)2 and V(Pic)2(HGlu) were observed.