| dc.description | In this paper we present speciation results for the ternary vanadium(III)–
dipicolinic acid (H2dipic) systems with the amino acids glycine (Hgly), proline (Hpro),
α-alanine (Hα-ala), and β-alanine (Hβ-ala), obtained by means of electromotive forces
measurements emf(H) using 3.0 mol·dm−3 KCl as the ionic medium and a temperature
of 25 °C. The experimental data were analyzed by means of the computational leastsquares
program LETAGROP, taking into account hydrolysis of the vanadium(III) cation,
the respective stability constants of the binary complexes, and the acid base reactions of
the ligands, which were kept fixed during the analysis. In the vanadium(III)–dipicolinic
acid–glycine system, formation of the ternary [V(Hdipic)(Hgly)]2+, [V(dipic)(Hgly)]+,
[V(dipic)(gly)], [V(dipic)(gly)(OH)]− and [V(dipic)(gly)(OH)2]2− was observed; in the
case of the vanadium(III)–dipicolinic acid–proline system the ternary complexes [V(Hdipic)
(Hpro)]2+, [V(dipic)(Hpro)]+, [V(dipic)(pro)] and [V(dipic)(pro)(OH)]− were observed; in
the vanadium(III)–picolinic acid–α-alanine were observed [V(Hdipic)(Hα-ala)]2+, [V(dipic)
(Hα-ala)]+, [V(dipic)(αala)], [V(dipic)(α-ala)(OH)]− and [V(dipic)(α-ala)(OH)2]2−; and
in the vanadium(III)–dipicolinic acid–β-ala system the complexes [V(dipic) (Hβ-ala)]+,
[V(dipic)(β-ala)], [V(dipic)(β-ala)(OH)]− and [V(dipic)(β-ala)(OH)2]2− were observed.
Their respective stability constants were determined, and we evaluated values of log10K
in order to understand the relative stability of the ternary complexes compared to the corresponding
binary ones. The species distribution diagrams are briefly discussed as a function
of pH. | |
