The HAlF4 superacid fragmentation induced by an excess electron attachment

Abstract

The excess electron attachment to the HAlF₄ superacid molecule was studied by employing ab initio CCSD(T) and MP2 methods and a purposely suited aug-cc-pVTZ+4s4p3d basis set. The results indicate that the HAlF₄ molecule, due to its polarity, may attract a distant excess electron and form a dipole-bound anionic state whose vertical electron binding energy is 1106 cm⁻¹. The initially formed (HAlF₄)⁻ anion of a dipole-bound nature undergoes an immediate structural reorganization driven by the (AlF₄)⁻ strongly-bound superhalogen anion formation. The potential energy surface analysis leads to the conclusion that the (HAlF₄)⁻ → (AlF₄)⁻ + H transformation should proceed spontaneously and involve the simultaneous structure relaxation of the AlF₄ moiety (in the direction approaching a tetrahedral geometry) and the excess electron density migration from the area outside the molecular framework to the valence AlF₄ region. The fragmentation of the HAlF₄ superacid molecule is predicted to be the final effect of the excess electron attachment process. In addition, the important antenna role of the initially formed (HAlF₄)⁻ dipole-bound anionic state is discussed.