Theoretical study on intermolecular interactions between furan and dihalogen molecules XY(X,Y=F,Cl,Br)

Equilibrium geometries, interaction energies, atomic charge, and charge transfer for the intermolecular interactions between furan and dihalogen molecules XY(X; Y=F,Cl,Br) were studied at the MP2aug-cc-pVDZ level. Three types of geometry are observed in these interactions: the pi-type geometry (I), in which the XY lies above the furan ring and almost perpendicularly to the C4-C5 bond of furan; the sigma-type geometry (II), where the X atom is pointed toward the nonbonding electron pair (n pair) of oxygen atom in furan; and the chi-type geometry (III), describing a blueshift hydrogen bond formed between the hydrogen atom of furan and dihalogen molecules XY. The calculated interaction energies show that the pi-type structures are more stable than the corresponding sigma-type and chi-type structures. To study the nature of the intermolecular interactions, an energy decomposition analysis was carried out and the results indicate that both the pi-type and sigma-type interactions are dominantly inductive energy in nature, while dispersion energy governs the chi-type interactions.