Tetrel bonds and conformational equilibria in the formamide-CO₂ complex: a rotational study

Area of Science:

• Physical Chemistry
• Molecular Spectroscopy
• Computational Chemistry

Background:

• Formamide-CO2 complexes are studied to understand non-covalent interactions.
• Tetrel bonds and hydrogen bonds play crucial roles in molecular complex formation.

Purpose of the Study:

• To investigate the structural and energetic properties of formamide-CO2 complexes.
• To identify and characterize different isomers of the formamide-CO2 complex.
• To determine the relative populations of the observed isomers.

Main Methods:

• Pulsed jet Fourier transform microwave spectroscopy was used to measure rotational spectra.
• Bader's quantum theory of atoms in molecules (QTAIM) was applied for interaction analysis.
• Johnson's non-covalent interaction (NCI) analyses were employed to study binding.
• Relative intensity measurements of spectral transitions were used to estimate isomer populations.

Main Results:

• Two isomers of the formamide-CO2 complex were detected and assigned.
• The dominant interaction in both isomers is a CO tetrel bond.
• Secondary linkages involve either N-H--O or C-H--O hydrogen bonds.
• The relative population of the two isomers was determined to be approximately 18:1.

Conclusions:

• The study successfully characterized two isomers of the formamide-CO2 complex.
• Tetrel bonds are key in stabilizing these complexes, alongside hydrogen bonds.
• The significant population difference between isomers provides insights into their relative stability.