Halogen bond, hydrogen bond and N⋯C interaction – On interrelation among these three noncovalent interactions

The analysis of interrelation among halogen bond, hydrogen bond and weak N⋯C interaction in the (CH3X)(HNC)(HCN) complexes (X = Cl, Br) was performed on the basis of MP2 calculations. The model system was chosen for the complexes in such a way that all three interactions stabilize the complexes consisting of three molecular fragments. Both two-body additive contributions and three-body nonadditive contributions to the total interaction energy are discussed. Additionally, interaction energy decomposition was performed with the use of SAPT, such that both two- and three-body contributions were also estimated. QTAIM was used for topological analysis of electron density. In the case of investigated complexes both hydrogen bond and N⋯C interaction predominate over halogen bond. The SAPT results indicate that the electrostatic contribution to interaction energy dominates for the hydrogen bond and the N⋯C interaction, while the dispersion component is mostly responsible for the halogen bonding, which is weakest of all. The QTAIM analysis reveals that the noticeable transfer of electron charge occurs only between the molecular fragments forming the hydrogen bond. Finally, we establish the influence of CP-corrected optimization and MP2 variant on the geometries and interaction energies of the complexes.