Formation Constants for the Ternary Complexes of Vanadium(III), 2,2′-Bipyridine, and the Amino Acids Histidine, Cysteine, Aspartic and Glutamic Acids

• Published in: Journal of solution chemistry 2012-06, Vol.41 (5), p.840-848
• Main Authors: Hernández, Lino, Lubes, Giuseppe, Rodríguez, Mildred, Lubes, Vito
• Format: Article
• Language: English
• Subjects: Amino acids; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Constants; Cysteine; Exact sciences and technology; General and physical chemistry; Geochemistry; Glutamic acid; Histidine; Industrial Chemistry/Chemical Engineering; Inorganic Chemistry; Ligands; Oceanography; Physical Chemistry; Solutions; Speciation; Stability constants
• ISSN: 0095-9782; 1572-8927
• DOI: 10.1007/s10953-012-9836-1

In this study we report the stability constants and the speciation of the ternary vanadium(III) complexes with 2,2′-bipyridine (Bipy) and the amino acids histidine (HHis), cysteine (H 2 Cys), aspartic acid (H 2 Asp) and glutamic acid (H 2 Glu) by means of potentiometric titrations employing 3.0 mol⋅dm −3 KCl as the ionic medium at 25 °C. The potentiometric data were analyzed 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 ligands, which were kept fixed during the analysis. The complexes detected in the different systems are: in the vanadium(III)–Bipy–HHis system, [V(HBipy)(HHis)] 4+ and [V(HBipy)(H 2 His)] 5+ ; in the vanadium(III)–Bipy–H 2 Cys system, [V 2 O(Bipy)(Cys)] 2+ ; in the vanadium(III)–Bipy–H 2 Asp system, [V(Bipy) (Asp)] + , [V 2 O(Bipy)(Asp)] 2+ , and V 2 O(Bipy) 2 (Asp) 2 ; and finally in the vanadium(III)–Bipy–H 2 Glu system, [V(Bipy)(H 2 Glu)] 3+ and [V(Bipy)(Glu)] + . The respective stability constants were determined and the specie distribution diagrams as a function of pH are briefly discussed.