The account of atom-pair dispersion interaction on the stabilization of C–H/π bound phenylacetylene–hydrocarbon complexes

Abstract

In this article, atom-pairwise dispersion interaction terms were calculated to describe the origin of dispersion interaction in weakly bound molecular clusters. A series of C–H/π bound phenylacetylene–hydrocarbon complexes were computationally investigated, using the dispersion-corrected DFT methods B3LYP-D3(BJ) and PBE0-D3(BJ) with def2-TZVPP and aug-cc-pVDZ basis sets. The geometry-optimized structures were used to quantitatively analyze the binding energy dependence on several atomic and molecular polarizability parameters. The binding energies of the dispersively bound complexes were excellently correlated linearly with the cumulative dispersion terms (ED3(BJ) and ETD) calculated using Grimme's D3(BJ) and D2 numerical methods, respectively. Only the binary complexes with significant contributions from electrostatic terms are found to deviate from linearity. Depending on the contribution of individual atoms of the ad-molecules, dispersion-layers were proposed. The first layers of hydrogen and carbon atoms have contributed ~ 85% of the total interaction energy. In the most stable structures, the ad-molecules were positioned atop of the center of mass of the PHA molecules suggesting the maximum atom-pair contacts between the interacting partners. The current results provide proof for the atomic polarizability parameters to be accountable for the dispersion energy and do not support ‘sandwiched hydrogen atom’ and ‘C–H···π hydrogen bonding’ models for the face-bound hydrocarbon complexes. The CHn number calculated from structural parameters showed a linear correlation with the binding energy, which suggests the directionless properties of the C–H/π interaction.