Probing internal electric fields of π‐ and σ‐hole bonds

Abstract

π‐ and σ‐holes are nonnuclear molecular regions of positive electric potential, which make non‐covalent interactions with negative sites, for example, lone pairs of molecules containing nitrogen or oxygen, the so called π‐ and σ‐hole bonds. We investigate these bonds locally using a probe programmed as a virtual molecule. Unlike the hydrogen bond, electric fields are detected having strengths that are different from the sum of the separated parts, meaning that molecular electrostatic potential surfaces analysis of the different parts are not enough to analyze the bonds. Based on an application of the Hellmann‐Feynman theorem, which states that intermolecular bonds are fully described by Coulombian interactions (electrostatic plus polarization), we connect the electric field strength with the bond strength measured in experiments, so that it can be considered as a quantifier for the bonds.