Ab initio study of aerogen-bonds between some heterocyclic compounds of benzene with the noble gas elements (Ne, Ar, and Kr)

Abstract

Ab initio calculations have been performed to study the complexes between the noble gas elements (Ae = Ne, Ar, Kr) with a series of benzene isoelectronic heterocyclic compounds of benzene, including boraphosphinine (BP), borazine (BN), and alumazine (AlN), at MP2/Aug-CC-pVTZ level of theory. According to the molecular electrostatic potential (MEP) iso-surface of BP, BN, and AlN, the active sites of rings are identified which utilized to predict the relative strength of aerogen···π (Ae···π) interactions as follows: Kr···π > Ar···π > Ne···π/Ae···BP > Ae···BN > Ae···AlN. Then, the equilibrium structures of all the complexes are characterized, and their energetic, geometrical, topological, and molecular orbital descriptors were used to estimate the strength of Ae···π interactions, that are in line with MEP results. Energy decomposition analysis reveals that dispersion effects play a vital role in formation of the Ae···π complexes. Furthermore, intermolecular interactions were also investigated with the quantum theory of atoms in molecules (QTAIM) and the non-covalent interactions (NCI) and natural bond orbital’s (NBO) analysis. NBO analysis showed that like the benzene complexes, charge transfers from the noble gas atom to heterocyclic ring have occurred. Finally, the aromaticity of the rings is measured using the well-established indices namely the nucleus independent chemical shift (NICS) and the average two-center index (ATI).