Br₂ dissociation in water clusters: The catalytic role of water

In this work, we explore the effect halogen bonds and hydrogen bonds have on the activation of the chemical bonds modified in the course of the Br2? (H2O)n? HOBr? HBr reaction and the effect the number of water molecules present in the cluster has on the barrier and the stability of the products formed. Using ab initio MP2 methods, we have analyzed the local electrodonating and electroaccepting power functions that revealed the differentiation between bromine atoms in Br2 due to interaction with water molecules, thus resulting in an increase in the donor power that stabilizes the proton transfer process from a water molecule in the next step of the reaction. This situation is confirmed by the lowering in the corresponding activation barrier found. Our results show that the catalytic effect of water is already important for clusters with three water molecules and the effect additional molecules have is related to the acid dissociation of the products.