We have carried out extensive computational analyses of the structure and bonding mechanism in trihalides DX���A� and the analogous hydrogen-bonded complexes DH���A� (D, X, A being F, Cl, Br, I) using relativistic density functional theory. We present an accurate physical model of the halogen bond based on quantitative Kohn�Sham molecular orbital theory, energy decomposition analyses and Voronoi deformation density analyses of the charge distribution, and compare it to the hydrogen bond. It appears that the halogen bond in DX���A� arises not only from classical electrostatic attraction but also receives substantial stabilization from HOMO�LUMO interactions between the lone pair of A� and the s* orbital of D�X. Thus, halogen bonds have a sizeable covalent component, similar to hydrogen bonds. Neither halogen bonds nor hydrogen bonds are therefore predominantly, let alone purely, electrostatic phenomena.

Halogen bonding vs. hydrogen bonding: A molecular orbital perspective

245th National Meeting (2013)

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