O---H stretching force constants in complexes of water with F^-, Cl^-, Li⁺ ions and LiF, LiCl ion pairs by 6-31G ab initio MO calculations

Abstract

Ab initio MO calculations using 6-31G and 6-31+G (for complexes with F^- and LiF) basis sets have been carried out for complexes of H₂O (monomer and dimer) with F^-, Cl^-, Li⁺ ions as well as with LiF and LiCl ion pairs for the evaluation of the O---H stretching force constants. The changes in force constants are discussed in terms of molecular interactions, cooperativity effect and interionic electrostatic interactions. It is noticed that the cooperativity effect also operates through ionic bonds in symmetrically hydrated ion pairs and that O---H stretching force constants are found to increase in the case of solvent bound ion pairs and symmetrically hydrated halide ions showing anticooperativity effect.