Revealing substituent effects on - stacking and halogen bond interactions. A Theoretical study

In this study, the MP2 level of theory was employed to explore the mutual influence between - stacking and halogen bonds interactions. Cooperativity effect was observed in X-ben||pyr∙∙∙Cl-F complexes (X = CN, F, Cl, Br, CH3 , OH and H where || and ∙∙∙ denote - stacking and halogen bonds interactions). This effect was analyzed in details in terms of the energetic, geometrical parameters, and charge transfer properties of the complexes. It was shown that the trend of binding energies of X-ben||pyr∙∙∙Cl-F complexes was as follows: H  OH < CH3 < F  Cl < Br < CN. In addition, the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) were also employed to characterize the interactions and to examine the strengthening of the interactions. The results indicate the cooperativity of - stacking and halogen bonds interactions in X-ben||pyr∙∙∙Cl-F complexes.