Weak interaction in halogen bonding systems: A challenge to the accuracy of the theoretical models

Abstract

Weak interactions of 44 halogen bonding complexes are analyzed. The interaction strength of neutral complexes can be visually demonstrated with the map of electron local function. For negatively charged complexes, it is found that bond length and ADCH atomic charge are effective tools for studying the weak interaction because of the strong charge transfer. Interaction energies have good linear correlations with its four components, electron density and electron potential energy density at halogen bond critical point. The effect of theoretical models on the order of interaction energies of four complex sets are investigated. It is found that these orders are dependent not only on the theoretical models used to calculate the interaction energy but also on the models for geometry optimization, which indicates the interaction energy orders of the four sets predicted by the theoretical models are not consistent. This brings a serious challenge to the accuracy of theoretical models considered here.