ELECTRON TOPOLOGICAL AND ENERGETIC STUDY OF THE INTERMOLECULAR HALOGEN BONDING INTERACTIONS IN COMPLEXES H2O ⋯ M (M = F2, ClF, ANDCF4)

The halogen bonding complexes H 2 O ⋯ M ( M = F 2, ClF , and CF 4) in comparison with the hydrogen bonding H 2 O ⋯ HF complex are studied by high-level ab initio calculations and electron topological atoms-in-molecules (AIM) analyses. The basis set superposition error corrections are important to predict if the structures are in good agreement with the experimental results. Both the CCSD(T)/aug-cc-pVTZ calculations and the AIM analyses indicate a interaction strength order: H 2 O ⋯ HF > H 2 O ⋯ ClF ⋯ H 2 O ⋯ F 2 ⋯ H 2 O ⋯ CF 4, with the interaction energies –7.91, –4.16, –1.11, and –1.05 kcal/mol, respectively. The symmetry-adapted perturbation theory analyses have been carried out towards understanding of the nature of the halogen bonding interactions in the complexes H 2 O ⋯ M ( M = F 2, ClF , and CF 4), where the exchange energies are the predominant repulsive components. For the complexes involving polar monomers, the hydrogen bonding H 2 O ⋯ HF and the halogen bonding H 2 O ⋯ ClF , the largest attractive contributions are the electrostatic energies. However, in H 2 O ⋯ F 2 and H 2 O ⋯ CF 4, the attractive dispersion energies become more important, and the induction energy in the former complex is a little higher than that in the latter. In contrary to the red-shifts of H – F , Cl – F , and F – F bond stretching vibrational frequencies in the complexes H 2 O ⋯ M ( M = HF , ClF , and F 2), the blue-shifts are predicted for C – F bonds neighboring water in H 2 O ⋯ CF 4.