Tetrel bonds and conformational equilibria in the formamide–CO2 complex: a rotational study†
The rotational spectra of the complex formamide–CO2 have been measured and assigned by pulsed jet Fourier transform microwave spectroscopy. Two isomers of the complex have been detected where a C⋯O tetrel bond dominates the interactions, and either N–H⋯O or C–H⋯O forms a secondary linkage. Bader's quantum theory of atoms in molecules and Johnson's non-covalent interaction analyses were applied to unveil the intermolecular binding sites and energetic properties in the complex. Relative intensity measurements on a set of μa-type transitions allowed estimating the relative population of the observed two isomers as NI/NII ≈ 18/1.