Polychlorinated Biphenyls Interactions with Water—Characterization Based on the Analysis of Non-Covalent Interactions and Energy Partitioning

Abstract

Although polychlorinated biphenyls (PCBs) have been long banned from use, both they and dioxins are still considered persistent organic pollutants. The reason is twofold: their relative inertness (especially to oxidation) and their ability to accumulate in fat tissue. The current study sheds light on the interactions of PCBs with water, chlorine, and chlorine dioxide. Necessary insight is gained from Atoms in Molecules (AIM) and Non-Covalent Interactions (NCI) index and analyses for the 1:1 complexes of PCBs with water and chlorine (Cl2) molecules. Further, Symmetry-Adapted Perturbation Theory (SAPT) calculations reveal the strength and nature of the intermolecular interactions, and the presence of halogen bonding is demonstrated in AIM, NCI, and SAPT studies. The stability of water, chlorine, and chlorine dioxide (ClO2) complexes with PCBs is discussed using the supramolecular MP2 approach. Finally, analysis of microsolvation shells of PCBs showed the origins of the hydrophobicity and environmental persistence of these chemicals. Our results are applicable to the sustainability of water treatment strategies providing a description of forces and interactions at the molecular level.