Theoretical Studies On Dimers Formed From Extraordinary Direct Interaction Between Two Positively Charged Atoms

It is well known that the intermolecular interactions play an importantrole in chemistry, physics, and in particular in the biodisciplines. Theydetermine the structure and physical properties of molecular complexes.Discovering novel molecular interactions is always an exciting part ofchemistry. During the past few decades a number of unusual molecularinteractions, including dihydrogen bond, π–hydrogen bond, π–type hydrogenbond, anion hydrogen bond, electron–hydrogen bond, intermolecularthree-electron hemibond, and halogen bond, have been proposed. Most ofthese molecular interactions are attractions between positively charged andnegatively charged atoms. From the viewpoint of electrostatics, it is naturalthat heterogeneously charged atoms attract each other. That homogeneouslycharged atoms also can attract each other sounds unbelievable. But recently anattraction between two positively charged atoms as secondary interaction incomplex CH2F2–ClF has been found by our work group. This discoveryencouraged us to consider, will two positive atoms in different moleculesimmediately attract each other to form a stable complex? The answer will begiven here by theoretical calculation.Chosing the simple dimers FXδ+···δ+HF(X=Cl,Br) and FXδ+···δ+YF(X,Y=Cl,Br) ,using the ab initio methods, we found that a novelintermolecular interaction in which two positively charged atoms in differentmolecules can attract each other to result in stable complexes, which isascribed to that hydrogen bond or halogen bond is stronger than electrostaticrepulsion between two positive charges.