Advances on the Determination of the Astatine Pourbaix Diagram: Predomination of AtO(OH)2− over At− in Basic Conditions

It is generally assumed that astatide (At−) is the predominant astatine species in basic aqueous media. This assumption is questioned in non‐complexing and non‐reductive aqueous solutions by means of high‐pressure anion‐exchange chromatography. Contrary to what is usually believed, astatide is found...

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Published in:Chemistry : a European journal 2016-02, Vol.22 (9), p.2964-2971
Main Authors: Sergentu, Dumitru-Claudiu, Teze, David, Sabatié-Gogova, Andréa, Alliot, Cyrille, Guo, Ning, Bassal, Fadel, Silva, Isidro Da, Deniaud, David, Maurice, Rémi, Champion, Julie, Galland, Nicolas, Montavon, Gilles
Format: Article
Language:English
Subjects:
Anion-exchange chromatography
Aqueous solutions
Astatine
Chemical Sciences
Chemistry
Chromatography
Competition
competition experiments
Exchanging
Hydrolysis
hydrolysis constants
Mathematical analysis
Media
or physical chemistry
Pourbaix diagrams
Pressure
quantum mechanical calculations
Quantum mechanics
Theoretical and
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Summary:It is generally assumed that astatide (At−) is the predominant astatine species in basic aqueous media. This assumption is questioned in non‐complexing and non‐reductive aqueous solutions by means of high‐pressure anion‐exchange chromatography. Contrary to what is usually believed, astatide is found to be a minor species at pH=11. A different species, which also bears a single negative charge, becomes predominant when the pH is increased beyond 7. Using competition experiments, an equilibrium constant value of 10−6.9 has been determined for the formation of this species from AtO(OH) with the exchange of one proton. The identification of this species, AtO(OH)2−, is achieved through relativistic quantum mechanical calculations, which rule out the significant formation of the AtO2− species, while leading to a hydrolysis constant of AtO(OH) in excellent agreement with experiment when the AtO(OH)2− species is considered. Beyond the completion of the Pourbaix diagram of astatine, this new information is of interest for the development of 211At radiolabeling protocols. Where it's At: The outcomes of chromatography, competition experiments, and quantum mechanical calculations are combined to demonstrate that the predominant astatine species in basic and non‐reductive conditions is not At−, but actually AtO(OH)2−.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201504403