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Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions

Authorized Users Only
2012
Authors
Holclajtner-Antunović, Ivanka
Bajuk-Bogdanović, Danica
Popa, Alexandru
Uskoković-Marković, Snežana
Article (Published version)
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Abstract
The various molecular species formed by decomposition of 12-tungstophosphoric acid (WPA) in methanol/water solutions of different composition, and over a pH range 1-12, were identified by UV, FTIR, micro Raman and P-31 NMR spectroscopy. The dependence of stability on organic solvent amount, pH and concentration of WPA in solution is investigated in detail. It is shown that addition of methanol in aqueous solution of WPA with varied pH causes extension of the pH region where parent Keggin anion is stable. While Keggin anion is preserved in aqueous solution with pH lt 2, in solution with 25% of methanol it is stable up to pH 2.5, in solution with 50% of methanol up to pH 3.5, and in solution with 75% of methanol Keggin anion is observed up to pH 4.5. Various molecular species, such as monovacant and trivacant lacunary Keggin structures and dimeric Wells-Dawson derivatives, are observed as a result of Keggin anion destruction with increasing of pH, but speciation in both aqueous and meth...anol/water solutions is similar. It is also shown that lacunary anions are less soluble in solutions with higher methanol content and with higher pH. In aqueous solution at pH >8, the solution contains only tungstates and phosphates with no precipitation. In solution with 25% of methanol, precipitate is formed at pH 8.0 and contains trivacant lacunary Keggin anion. In solution with 50% of methanol the precipitation is at pH 6.5, and in solution with 75% of methanol it is observed at pH 4.5, but in both solutions the precipitate contains monovacant lacunary anion as the main component.

Keywords:
12-Tungstophosphoric acid / Methanol/water / Stability / FTIR / Micro Raman / P-31 NMR spectroscopy
Source:
Inorganica Chimica Acta, 2012, 383, 26-32
Publisher:
  • Elsevier Science Sa, Lausanne
Funding / projects:
  • Electroconducting and redox-active polymers and oligomers: synthesis, structure, properties and applications (RS-172043)

DOI: 10.1016/j.ica.2011.10.035

ISSN: 0020-1693

WoS: 000300623600005

Scopus: 2-s2.0-84857239429
[ Google Scholar ]
28
23
URI
https://farfar.pharmacy.bg.ac.rs/handle/123456789/1717
Collections
  • Radovi istraživača / Researchers’ publications
Institution/Community
Pharmacy
TY  - JOUR
AU  - Holclajtner-Antunović, Ivanka
AU  - Bajuk-Bogdanović, Danica
AU  - Popa, Alexandru
AU  - Uskoković-Marković, Snežana
PY  - 2012
UR  - https://farfar.pharmacy.bg.ac.rs/handle/123456789/1717
AB  - The various molecular species formed by decomposition of 12-tungstophosphoric acid (WPA) in methanol/water solutions of different composition, and over a pH range 1-12, were identified by UV, FTIR, micro Raman and P-31 NMR spectroscopy. The dependence of stability on organic solvent amount, pH and concentration of WPA in solution is investigated in detail. It is shown that addition of methanol in aqueous solution of WPA with varied pH causes extension of the pH region where parent Keggin anion is stable. While Keggin anion is preserved in aqueous solution with pH  lt 2, in solution with 25% of methanol it is stable up to pH 2.5, in solution with 50% of methanol up to pH 3.5, and in solution with 75% of methanol Keggin anion is observed up to pH 4.5. Various molecular species, such as monovacant and trivacant lacunary Keggin structures and dimeric Wells-Dawson derivatives, are observed as a result of Keggin anion destruction with increasing of pH, but speciation in both aqueous and methanol/water solutions is similar. It is also shown that lacunary anions are less soluble in solutions with higher methanol content and with higher pH. In aqueous solution at pH >8, the solution contains only tungstates and phosphates with no precipitation. In solution with 25% of methanol, precipitate is formed at pH 8.0 and contains trivacant lacunary Keggin anion. In solution with 50% of methanol the precipitation is at pH 6.5, and in solution with 75% of methanol it is observed at pH 4.5, but in both solutions the precipitate contains monovacant lacunary anion as the main component.
PB  - Elsevier Science Sa, Lausanne
T2  - Inorganica Chimica Acta
T1  - Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions
VL  - 383
SP  - 26
EP  - 32
DO  - 10.1016/j.ica.2011.10.035
ER  - 
@article{
author = "Holclajtner-Antunović, Ivanka and Bajuk-Bogdanović, Danica and Popa, Alexandru and Uskoković-Marković, Snežana",
year = "2012",
abstract = "The various molecular species formed by decomposition of 12-tungstophosphoric acid (WPA) in methanol/water solutions of different composition, and over a pH range 1-12, were identified by UV, FTIR, micro Raman and P-31 NMR spectroscopy. The dependence of stability on organic solvent amount, pH and concentration of WPA in solution is investigated in detail. It is shown that addition of methanol in aqueous solution of WPA with varied pH causes extension of the pH region where parent Keggin anion is stable. While Keggin anion is preserved in aqueous solution with pH  lt 2, in solution with 25% of methanol it is stable up to pH 2.5, in solution with 50% of methanol up to pH 3.5, and in solution with 75% of methanol Keggin anion is observed up to pH 4.5. Various molecular species, such as monovacant and trivacant lacunary Keggin structures and dimeric Wells-Dawson derivatives, are observed as a result of Keggin anion destruction with increasing of pH, but speciation in both aqueous and methanol/water solutions is similar. It is also shown that lacunary anions are less soluble in solutions with higher methanol content and with higher pH. In aqueous solution at pH >8, the solution contains only tungstates and phosphates with no precipitation. In solution with 25% of methanol, precipitate is formed at pH 8.0 and contains trivacant lacunary Keggin anion. In solution with 50% of methanol the precipitation is at pH 6.5, and in solution with 75% of methanol it is observed at pH 4.5, but in both solutions the precipitate contains monovacant lacunary anion as the main component.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Inorganica Chimica Acta",
title = "Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions",
volume = "383",
pages = "26-32",
doi = "10.1016/j.ica.2011.10.035"
}
Holclajtner-Antunović, I., Bajuk-Bogdanović, D., Popa, A.,& Uskoković-Marković, S.. (2012). Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions. in Inorganica Chimica Acta
Elsevier Science Sa, Lausanne., 383, 26-32.
https://doi.org/10.1016/j.ica.2011.10.035
Holclajtner-Antunović I, Bajuk-Bogdanović D, Popa A, Uskoković-Marković S. Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions. in Inorganica Chimica Acta. 2012;383:26-32.
doi:10.1016/j.ica.2011.10.035 .
Holclajtner-Antunović, Ivanka, Bajuk-Bogdanović, Danica, Popa, Alexandru, Uskoković-Marković, Snežana, "Spectroscopic identification of molecular species of 12-tungstophosphoric acid in methanol/water solutions" in Inorganica Chimica Acta, 383 (2012):26-32,
https://doi.org/10.1016/j.ica.2011.10.035 . .

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