Possible Formation of H3O+ Cations Due to Aluminum Fluoride Interactions with Water.

The isomeric structures formed by the aluminum fluoride (AlF3) system and surrounding water molecules were theoretically examined by employing MP2 and CCSD(T) methods and the aug-cc-pVDZ basis set together with the polarized continuum solvation model within a self-consistent reaction field treatment. The calculations performed for the AlF3·n(H2O) systems (n = 1-6) revealed that facial and meridional octahedral structures correspond to the lowest energy isomers for the AlF3·4H2O, AlF3·5H2O, and AlF3·6H2O systems, whereas the isomers containing the H3O+ and AlF3OH- fragments were predicted to be less stable by only 5-7 kcal/mol, which indicates the possible formation of the hydronium cations in such systems even at room temperature.