New Infrared Bands of the C-Bonded Isomer of OC–N₂O and Determination of Two Intermolecular Frequencies

Abstract

Three combination bands involving intermolecular modes of the most stable isomer of the OC-NO van der Waals complex have been observed, two in the carbon monoxide CO stretch region (∼2150 cm) and one in the ν asymmetric stretch region of NO (∼2223 cm). Vibrational assignment is achieved by comparison with data recently published ( Barclay , A. ; et al. Chem. Phys. Lett. 2016 , 62 , 651 ), concerning OC-CO. Two of these bands involve the same intermolecular mode, one with the CO stretch and the other with the ν asymmetric stretch of NO. The values of intermolecular frequency deduced from these two bands agree very well, showing no significant dependence on intramolecular vibrational excitation.

A New Ab Initio Potential Energy Surface and Rovibrational Spectra for the CO–N2O Complex

“…The intermolecular first excited state is attributed to the mode of in-plane disrotation with frequencies of 24.9488 and 24.6677 cm –1 for CO–N 2 O at the ν 3 = 0 and 1 states of N 2 O, respectively. The calculated frequency for CO–N 2 O with N 2 O in the ν 3 = 1 state matches well with the corresponding experimental value of 24.181 cm –1 . In the previous work, an ab initio value of 29.13 cm –1 was reported by Venayagamoorthy and Ford under the harmonic frequency computations .…”

“…The ZPE is about one-fourth of the global potential wells, indicating that the ground state of CO− N 2 O is localized. Furthermore, the vibrational ground state energy is −296.8482 cm −1 for CO−N 2 O at the N 2 O ν 3 = 1 state, and the ν 3 vibrational origin shift of the N 2 O monomer in CO−N 2 O can be inferred to be 2.7570 cm −1 , which is in good accordance with the experimental data 10 (2.9048 cm −1 ). The blue-shifted band origin implies that the intermolecular interaction of the CO−N 2 O complex becomes weaker upon vibrational excitation.…”

“…Venayagamoorthy and Ford carried out ab initio calculations for CO–N 2 O at the MP2 level in 2005, while the study was limited to the geometrical optimizations of a few specific points on the potential energy surface (PES) and harmonic frequency computations. In their work, the predicted intermolecular frequency for the in-plane CO rock/disrotatory bending vibrational mode was 29.13 cm –1 , which significantly deviated from the experimental value of 24.181 cm –1 . In addition, the calculated shift of the N 2 O ν 3 asymmetric stretching mode in the CO–N 2 O complex with the value of 3.2 cm –1 did not reproduce well the observed data of 2.9054 cm –1 .…”

“…In the same year, new infrared bands of CO− N 2 O in the CO stretching zone and in the N 2 O ν 3 stretching zone were recorded. 10 In their work, the authors further determined two intermolecular vibrational frequencies from the obtained combination bands. It is necessary to combine experimental investigations with theoretical studies to comprehensively understand the characteristics of the intricate spectra.…”

“…The results indicated that there exists another stable T-shaped structure for the CO–N 2 O complex with a higher energy than that observed previously, but the CO moiety is flipped by 180°. In the same year, new infrared bands of CO–N 2 O in the CO stretching zone and in the N 2 O ν 3 stretching zone were recorded . In their work, the authors further determined two intermolecular vibrational frequencies from the obtained combination bands.…”