Intermolecular interaction characteristics of the all-carboatomic ring, cyclo[18]carbon: Focusing on molecular adsorption and stacking

Recently, an intriguing all-carboatomic ring, cyclo[18]carbon, was observed in the condensed phase for the first time, and it quickly attracted widespread attention. In this article, we first investigated the interaction of the cyclo[18]carbon with external environment through electrostatic potential and our recently proposed van der Waals potential, and then examined the strength and nature of the intermolecular interactions between cyclo[18]carbon and various small molecules in detail by state-of-art quantum chemistry calculations and elaborate wavefunction analyses. Finally, we studied the cyclo[18] carbon dimer, which is closely related to actual status of the cyclo[18]carbon in condensed phase. These researches show that the cyclo[18]carbon has a strong tendency to adsorb small molecules to or near its ring center, and the dispersion attraction is found to play a leading role in the binding interaction, while the electrostatic effect has a nonnegligible influence on the configuration of the molecular complexes. Two cyclo[18]carbon molecules can form a relatively stable dimer through prominent pi-pi stacking effect. Its ideal configuration is found to have a face-to-face D-9d symmetry, but this geometry can be easily broken by relative sliding between the two rings due to thermal motion, as revealed by ab initio molecular dynamic simulation. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The research found that cyclo[18]carbon has a strong tendency to adsorb small molecules in its condensed phase, where dispersion attraction plays a leading role in binding interactions and the electrostatic effect also influences the configuration of molecular complexes. Additionally, two cyclo[18]carbon molecules can form a stable dimer through pi-pi stacking effect.