The HF2−–(H2O)2 complex: a theoretical study

Energetics, geometries and vibrational frequencies of three minimum energy structures of the HF2−–(H2O)2 complex are examined using density functional theory. For the most stable geometry the water molecules are hydrogen bonded to different F atoms of HF2− and to one another, forming a ring structure, and the water dimer is largely intact. Both the F–F distance and the blue shift of the F–H–F asymmetric stretch are significantly smaller than for HF2−–H2O. The energy for dissociation to HF+F−–(H2O)2 is 27.1 kcal/mol, and the strong hydrogen bond of HF2− is weakened by 18.9 kcal/mol (41%).