C–H⋯π interactions involving acetylene: an ab initio MO study

Abstract

Ab initio MO calculations on the weak complexes of acetylene with CH3Cl, CH2Cl2 and CHCl3, provide qualitative and quantitative insights into the nature of the C–H⋯π interaction in these species. Cooperative C–H⋯C(π) interactions stabilize the HCCH⋯(CH3Cl)2, HCCH⋯(CH2Cl2)2 and HCCH⋯(CHCl3)2 complexes. The interaction energies at the MP2/6-311+G(df,pd)//MP2/6-31G(d,p) level of theory, including ZPE contributions, and corrected for the basis set superposition error (BSSE), amount to 1.75, 2.27 and 2.91kcal/mol, respectively. An energy decomposition analysis shows the variation of the different components as a function of the increase in polarity of the C–H bond. The electron correlation contribution is the most significant component of the binding energy.