2016
ACL
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D.C.Sergentu, D.Teze, A.Sabatié-Gogova, C.Alliot, N.Guo, F.Bassal, I.Da Silva, D.Deniaud, R.Maurice, J.Champion, N.Galland, G.Montavon, 'Advances on the Determination of the Astatine Pourbaix Diagram: Predomination of AtO(OH)2− over At− in Basic Conditions', Chem.-Eur. J. 22 2964-2971 (2016) doi:10.1002/chem.201504403
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.
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