Strengthening halogen… halogen interactions by hydrogen and lithium bonds in NCM···NCX···YCH3 and CNM···CNX···YCH3 (M = H, Li and X,Y = Cl, Br) complexes: a comparative study

Abstract

ABSTRACTIn this work, ab initio calculations at the MP2/aug-cc-pVTZ level of theory are performed to analyse the interplay between halogen···halogen and hydrogen/lithium bond interactions in NCM···NCX···YCH3 and CNM···CNX···YCH3 (M = H, Li and X,Y = Cl, Br) complexes. The nature of these interactions and the origin of cooperativity are studied by means of molecular electrostatic potential, energy decomposition and atoms in molecules (AIM) analyses. For each triad, the shortening of the binding distances in the H-bonding is more prominent than that in the Li-bonding. The estimated values of cooperative energy are all negative which indicate a positive cooperativity between both of the interactions. The two-body energy term is the most important source of the attraction of ternary complexes, which its contribution accounts for 89%–96% of the total interaction energy. The topological analysis based on the AIM theory is used to characterise the interactions and analyse their enhancement with varying electron density at bond critical points.