Disentanglement of orthogonal hydrogen and halogen bonds via natural orbital for chemical valence: A charge displacement analysis

As known, the electron density of covalently bound halogen atoms is anisotropically distributed, making them potentially able to establish many weak interactions, acting at the same time as halogen bond donors and hydrogen bond acceptors. Indeed, there are many examples in which the halogen and hydrogen bond coexist in the same structure and, if a correct bond analysis is required, their separation is mandatory. Here, the advantages and limitations of coupling the charge displacement analysis with natural orbital for chemical valence method (NOCV-CD) to separately analyze orthogonal weak interactions are shown, for both symmetric and asymmetric adducts. The methodology gives optimal results with intermolecular adducts but, in the presence of an organometallic complex, also intramolecular interactions can be correctly analyzed. Beyond the methodological aspects, it is shown that correctly separate and quantify the interactions can give interesting chemical insights about the systems.