Intermolecular amide and aldehyde interactions: rotational spectroscopy of the complexes of formaldehyde with 2-azetidinone and formamide

Abstract

The binary intermolecular complexes of amides and formaldehyde can be taken as suitable models to investigate the non-covalent interactions of a peptide with the carbonyl group. We herein studied the rotational spectra of the model complexes of 2-azetidinone–H₂CO and formamide–H₂CO generated in a helium supersonic jet. For each complex, one rotational spectra featuring hyperfine structures caused by the ¹⁴N quadrupole coupling effect was observed and assigned to its global minimum conformation. The detected isomers of both studied complexes are stabilized by a dominant amide hydrogen bond N–H⋯OC and a weaker C–H⋯O interaction, preferring the C_s symmetry. NBO and SAPT analyses provide quantitative estimation of the non-covalent interactions stabilizing the complexes.