ANALYSIS OF THE STATE OF ISOPOLYNIOBOTUNGSTATE ANIONS (Nb:W = 3:3) AND THEIR SYNTHESIS FROM AQUEOUS SOLUTIONS

Svetlana М. Vavilova; Maksym А. Kryuchkov; Victoria V. Ignatуeva; Ekaterina Е. Belousova

doi:10.17308/kcmf.2017.19/224

Authors

Svetlana М. Vavilova Cand. Sci. (Chem.), Lecture of Scientific and Mathematical Disciplines Department, Voronezh State Medical University named after N.N. Burdenko; ph.: +7(960) 1220157, e-mail: svavilova@mail.ru
Maksym А. Kryuchkov Ph.D (Chem.), Department of Chemistry, McGill University, Montreal, Quebec, Canada; e-mail: maks_ne@yahoo.com
Victoria V. Ignatуeva Cand. Sci. (Chem.), Assistant Professor of Pharmaceutical and Medicinal Chemistry Department M. Gorky Donetsk National Medical University, Donetsk People’s Republic; ph.: +38(050) 9001116, e-mail: ignatyevavictoriya@gmail.com
Ekaterina Е. Belousova Cand. Sci. (Chem.), Assistant Professor of Inorganic Chemistry Department, Donetsk National University, Donetsk People’s Republic; ph.: +38(050) 2958348

DOI:

https://doi.org/10.17308/kcmf.2017.19/224

Keywords:

polyoxometalates, isopolyanion, isopolyniobotungstate, Lindqvist anion, modeling complex formation in solution

Abstract

The formation of complexes in the system Nb₆O₁₉^8-–WO₄^2-–H⁺–H₂O, where Nb:W = 3:3 and C⁰_Nb+W= 10, 5, 2.5 and 1 mmol/L, was studied by pH–complexonometric titration. Using computer modeling of the processes of complexes formation (CLINP 2.1 software), concentrational constants of the mixed isopolyniobotungstate anions formation were obtained (Z=C0H+C0Nb+W=0−3.0Z=CH+0CNb+W0=0−3.0, background electrolyte is NaCl) and their distribution diagrams were built. The thermodynamic constants of H_xNb₃W₃O₁₉^(5-x)- (х=0–3) formation were calculated, and it was shown that the formation of these anions takes place only after the polycondensation of the initial orthotungstate anions. Calcium and Thallium salts (Ca_1.5Н₂Nb₃W₃O₁₉·12H₂O and Tl_5-xН_xNb₃W₃O₁₉·nH₂O, respectively, x = 1–3) were prepared and characterized by X–ray spectral analysis, scanning electron microscopy, and IR–spectroscopy.