Selective Emergence of the Halogen Bond in Ground and Excited States of Noble‐Gas–Chlorine Systems. Issue 13 (20th February 2019) - Pirani, Fernando
Abstract: Molecular‐beam scattering experiments and theoretical calculations prove the nature, strength, and selectivity of the halogen bonds (XB) in the interaction of halogen molecules with the series of noble gas (Ng) atoms. The XB, accompanied by charge transfer from the Ng to the halogen, is shown to take place in, and measurably stabilize, the collinear conformation of the adducts, which thus becomes (in contrast to what happens for other Ng‐molecule systems) approximately as bound as the T‐shaped form. It is also shown how and why XB is inhibited when the halogen molecule is in the 3 Πu excited state. A general potential formulation fitting the experimental observables, based on few physically essential parameters, is proposed to describe the interaction accurately and is validated by ab initio computations. Abstract : The intermolecular interaction in noble gas adducts with Cl2 presents peculiar features in comparison with diatoms. Specifically, for the collinear conformation with Cl2 in its ground state a halogen bond contribution occurs, together with a sizable charge transfer from noble gas to Cl2, and stabilizes the conformer. The halogen bond is inhibited if Cl2 is in the excited state.