Rotational spectroscopic studies of the tetrel bonded CH3CN-CO2 complex

Abstract

The rotational spectra of the weakly bound acetonitrile-carbon dioxide complex have been recorded using a pulsed-nozzle Fourier transform microwave spectrometer. In a supersonic expansion using helium as the carrier gas, the two lowest energy conformers were observed. A T-shaped structure where the nitrogen end of CH3CN donates electron density to the C center of CO2, and a slipped-parallel structure where the CO2 and CH3CN are aligned such that the linear heavy atom backbones are parallel. Spectra were also recorded for the CD3CN∙∙∙CO2 and the CH313CN∙∙∙CO2 isotopologues which help to confirm the structures observed. The spectra show hyperfine splitting due to nitrogen quadrupole coupling which could be resolved. The CH3CN∙∙∙CO2 complex offers the possibility to study the tetrel bond involving the three C atoms of the system. The observed T-shaped structure is bound by a N∙∙∙C carbon/tetrel bond. The Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses are used to identify the non-covalent interactions present in this complex and investigate different types of tetrel bonds.