Halogen Bonding in the Complexes of CH₃I and CCl₄ with Oxygen-Containing Halogen-Bond Acceptors

Abstract

Methyl iodine (CH₃I) and carbon tetrachloride (CCl₄) are both important volatile precursors for atmospheric ozone destruction. CH₃I and CCl₄ can act as halogen bond donors to form molecular complexes with atmospheric organic species, such as 2,5-dihydrofuran, tetrahydrofuran, and acetone. This study characterized the halogen bonds in the CH₃I and CCl₄ complexes using matrix isolation infrared spectroscopy and density functional theory calculations. With the combination of vibrational frequencies in spectra and the calculated interaction energies, frequencies and atoms-in-molecules analyses, we confirmed the formation of halogen-bonded complexes. CH₃I as a halogen-bond donor is comparable or slightly weaker than CCl₄, and furans involving ether oxygens are better halogen acceptors than acetone. The results help to understand the possibilities of formation of atmospheric molecular complexes that may influence the atmospheric chemical activities and enhance the aerosol formation.