Intermolecular binding of С...H−Cl in complexes of methane, ethane, and propane with a chlorine hydride molecule

Quantum-chemical calculations of binary complexes with the intermolecular bond С...H−Cl formed by methane, ethane, and propane molecules with a chlorine hydride molecule were carried out by the MP2/aug-cc-pVTZ method. It is shown that the bonding of hydrocarbon with an HCl molecule is possible at different mutual orientation of monomers; at that, the properties of the formed complexes are similar to the properties of molecular systems with a typical hydrogen (H-) bond. Upon complexation, elongation of the covalent bond H−Cl is observed with a frequency shift of the respective IR band of the valence vibration to the long-wave region, as well as a chemical shift on the bridging hydrogen atom characteristic of H-bonded complexes. Analysis of the nature of intermolecular bonding included decomposition of the binding energy into components, as well as NBO analysis and study of the electron density topology by the AIM method of the Bader theory. Potential curves of intermolecular interaction and electron density shift maps when the complex is formed out of monomers are were plotted.