Theoretical study of noncovalent interactions between triple bonds and chlorine atoms in complexes of acetylene and some chloromethanes

Ab initio calculations were performed to investigate the noncovalent interactions between the triple bonds and chlorine atoms in the complexes of acetylene with several chloromethanes, CH3Cl, CH2Cl2, CHCl3 and CCl4. The intermolecular potential surfaces of the acetylene-chloromethane complexes containing C-Cl⋯π (triple bond) interaction were calculated by the HF and MP2 methods with Dunning's correlation consistent basis sets (cc-pVXZ, X = D, T and Q). At the minimum, the intermolecular distances between the triple bond and chlorine atom range from 3.3 to 3.5 Å. The CCSD(T) method predicted that the binding energies of the acetylene complexes with CH3Cl, CH2Cl2, CHCl3 and CCl4 are −0.49, −0.77, −1.05 and −1.34 kcal/mol at the basis set limit, respectively. The energy decomposition analysis indicates that the complex is mainly stabilized by the dispersion interaction while the electrostatic interaction also plays an important role in the attraction between acetylene and chloromethane molecules.