Theoretical Study of the Formation of Complexes Between CO2 and Nitrogen Heterocycles

Abstract

A density functional theory study was performed to analyze the formation of complexes between CO2 and different nitrogen heterocycles such as imidazole, 2-methylimidazole, benzimidazole, and pyrazine. Two orientations of CO2 were considered: in-plane and top-on with respect to the plane of the heterocyclic ring. The in-plane complexes are more stable than their top-on counterparts, most likely due to electrostatic and Lewis acid-base interactions. The strength of the intermolecular interactions in the top-on complexes can be related to a combination of dispersion, weak electrostatic, dipole-quadrupole and quadrupole-quadrupole interactions, and to some extent to the interactions where some charge transfer from the ring to CO2 is involved. With respect to a potential use as CO2 scrubbers, imidazole and its derivatives appear to be better than pyrazine.