Computational Investigation of Halogen Bonding in X-Br···Nucleophile(X=F,Cl,Br) Complexes

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Presenter Information(s)

Zane Youssef, Blake Bui, Richard Nguyen

Abstract or Description

Noncovalent interactions govern molecular assembly, recognition, and reactivity in chemical and biological systems. While hydrogen bonds have long been the main driver for molecular assembly, σ-hole interactions have opened new routes for the synthesis of versatile materials with desired physical and chemical properties. In particular, halogen bonding has gained attention for its applications in materials science, catalysis, and drug design. Halogen bonds arise from a donor-acceptor interaction between a nucleophile N, and the σ-hole (surface of positive charge) of a covalently bonded halogen atom X to a substituent R, resulting in the N--X-R bonding pattern. Halogen bonds are highly directional and can be tuned by modifying the nucleophile N, the halogen atom X and/or the covalently bonded substituent R. However, the electronic interactions driving the formation of halogen bonds remain elusive. In particular, the covalent character of the N--X interaction and how it is affected by the different components N, X and R, are still subject to debate.

This study investigates halogen bonding interactions between the dimers Br-X (X=F, Cl and Br) and the nucleophiles (NCH, PCH, NH₃, OCH₂) through computational quantum chemistry methods. Geometries, interaction energies, electrostatic potential maps, and dipole moment are analyzed. A quasi-atomic orbital (QUAO) analysis provides a quantitative measure of the covalent character of the N--X bond. This analysis provides valuable insight into the electronic interactions driving the formation of the halogen bonds, and how each component of the system (N, X and R) affects the covalent character of the bond.

Mentor

Dr. Emilie Guidez