Simultaneous interactions of amphoteric halogen in XY (X = Cl, Br and Y = F, Cl, Br) with C and O atoms of CO2 in ring-shaped CO2·X(Y)·CO2 complexes

Abstract

Dihalogen molecule XY (X=Cl and Br and Y=F, Cl and Br) can interact with two CO2 and form ring-shaped CO2·X(Y)·CO2 trimers, in which the X atom simultaneously interacts with C atom of one CO2 and O atom of the other CO2. Theoretical calculations show that their optimized geometries and stretching vibrational frequencies are different from the individual (CO2)2, CO2⋯XY and YX⋯CO2 dimers. Their interaction energies are stronger than the sum of the interaction energies of the individual dimers, revealing the cooperativity between the dimers. Their binding distances and interaction strengths are closely associated with the electronegativity of X and Y atoms. Energy decomposition analysis suggests that electrostatic force is the main net contribution to total interaction energy. Quantum theory of atoms in molecules analysis confirms the formation of ring-shaped structures and the cooperativity between the dimers. Molecular electrostatic potential was employed to elucidate the formation mechanisms of ring-shaped trimers.