Experimental electron density overlapping in hydrogen bonds: topology vs. energetics

Abstract

We have investigated the relationship between the energetic properties of the hydrogen bond (HB) interaction and the topological overlapping of the electronic clouds at the H⋯O critical point r CP. This study involves a total of 83 X–H⋯O (X=C, N, O) HBs, which have been described in terms of the topological properties of the electron density ρ( r ) at r CP for a large set of compounds. Kinetic G( r CP) and potential V( r CP) contributions to the local energy density of electrons exhibit linear functionalities against, respectively, the positive and negative curvatures of ρ( r ) at the critical point, showing an effective deconvolution in the local form of the Virial theorem. The topological variation of the curvatures at r CP, and therefore changes in the H⋯O overlapping, are related to the onset of the repulsion between the electronic clouds of the basic and acid atoms.