A density functional theory study on the interactions between dibenzothiophene and tetrafluoroborate-based ionic liquids.

The interactions between dibenzothiophene (DBT) and N-butyl-N-methylimidazolium tetrafluoroborate ([BMIM][BF4]), N-butyl-N-methylmorpholinium tetrafluoroborate ([Bmmorpholinium][BF4]), N-butyl-N-methylpiperdinium tetrafluoroborate ([BMPiper][BF4]), N-butyl-N-methylpyrrolidinium tetrafluoroborate ([BMPyrro][BF4]), and N-butylpyridinium tetrafluoroborate ([BPY][BF4]) were investigated using density functional theory approach. Geometric, electron, and topological properties were analyzed using natural bond orbital, atoms in molecules theory, and noncovalent interaction methods in order to understand intermolecular interactions between DBT and ionic liquids. The result shows that hydrogen bond and van der Waals interactions are widespread in all the ionic liquids-DBT systems. Ion-π interactions between DBT and cation or anion are also observed, while π+-π interactions are only found in the [BMIM][BF4]-DBT and [BPY][BF4]-DBT systems. The order of interaction energy is [BPY][BF4]-DBT > [BMIM][BF4]-DBT >> [BMPiper][BF4]-DBT > [BMPyrro][BF4]-DBT > [BMmorpholinum][BF4]-DBT. The energies between DBT and the two ionic liquids containing aromatic cations are significantly higher.