The sigma-hole is an important concept which has been widely used lately to describe the halogen bond (XB) essentially as electrostatic in nature. However, this idea is not free of controversy. For the sake of this work, localised molecular orbital energy decomposition analysis (LMOEDA), interacting quantum atom (IQA) method and analysis of the electrostatic potential have been applied to O-Cl...B (B=CO, PH3, SH2, CS, NH3, OH-) complexes. The results show that in their equilibrium geometry the stabilizing effect that arises from the Pauli exclusion principle is larger in magnitude than the electrostatic interactions. Besides, it appears that an electronic exchange channel is established at a certain approach distance between the monomers.
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