New vibrational assignments for the ν 1 to ν 17 vibrational modes of aziridine and first analysis of the high-resolution infrared spectrum of aziridine between 720 and 1050 cm−1

Abstract

Fourier transform spectra of aziridine (C2H4NH) were recorded at high resolution (0.002 or 0.003 cm−1) in the 600–1750 and 1750–4000 cm−1 regions, using a Bruker IFS125HR (an upgraded version of the IFS120HR) spectrometer, located at the LISA facility in Creteil. In parallel, the harmonic force field of aziridine was evaluated analytically at the optimized geometry with second-order Møller–Plesset perturbation theory (MP2) together with the correlation-consistent polarized valence triple zeta basis sets cc-pVTZ. These ab initio predictions were used to perform consistent vibrational assignments for the ν 1 to ν 17 fundamental bands of aziridine observed in the infrared spectra recorded during this study. Finally, a first detailed rotational assignment was performed for two B-type bands located at 772.3571 cm−1 (ν 10, CH2 rock) and 997.1592 cm−1 (ν 8, NH bend) and for an A-type band located at 904.0429 cm−1 (ν 17, ring deform). We noticed that the ν 10 band is weakly perturbed, presumably because the v 10 = 1 rotational levels are coupled with those of the v 18 = 1 dark band located around 817 cm−1 through B-type and C-type Coriolis resonances.