IR photofragmentation of the phenyl cation: spectroscopy and fragmentation pathways

Abstract

We present the gas-phase infrared spectra of the phenyl cation, phenylium, in its perprotio C6H5+ and perdeutero C6D5+ forms, in the 260--1925 cm-1 (5.2-38 μm) spectral range, and investigate the...

Fingerprinting fragments of fragile interstellar molecules: dissociation chemistry of pyridine and benzonitrile revealed by infrared spectroscopy and theory

“…The 1735 cm −1 band and many other features can be associated with the phenyl + structure. This assignment is strengthened by the comparison with experimental infrared frequencies from Wiersma et al 73 The result shows that we observe the loss of CNc, rather than the loss of C 2 H 2 . The other CC stretching mode around 1680 cm −1 is likely due to an interesting structure containing a CH group and a 5-membered ring that was observed at the B3LYP-GD3/N07D level of theory (Supplementary Fig.…”

A Spectroscopic View on Cosmic PAH Emission

“…In this respect, the calculated IR spectra in the harmonic approximation have clear limitations, even after applying a scaling factor (amounting to ≃100 cm –1 ). Overall, these anharmonic studies demonstrate that calculated frequencies agree with the measurements at the 0.2% level without the need for scaling factors and, in addition, they reproduce the relative strength better. ,,, Nevertheless, there is room for improvement, as measurements show that triple combination bands should be accounted for as well and an accurate benchmark is needed to improve on anharmonic infrared intensities and prediction of symmetric modes . In this assessment, we should keep in mind that quantum chemical calculations are now approaching the reliability demanded by astronomical observations with the JWST spectrometers, 1–2 cm –1 spectral resolution.…”

“…Moreover, anharmonicity may shift bands out of resonance, affecting the peak position. The advantage of this technique is the possibility to probe the vibrational spectrum of unusual PAHs, such as protonated 85 or dehydrogenated 86 species. In addition, information about the fragmentation and hence the stability of the studied molecules comes for free.…”

“…2,93,100,101 Nevertheless, there is room for improvement, as measurements show that triple combination bands should be accounted for as well 90 and an accurate benchmark is needed to improve on anharmonic infrared intensities and prediction of symmetric modes. 86 In this assessment, we should keep in mind that quantum chemical calculations are now approaching the reliability demanded by astronomical observations with the JWST spectrometers, 1−2 cm −1 spectral resolution. For now, computations are limited to small PAHs and it will be important to develop reliable extrapolations into the larger size regime thought to be relevant for the interstellar PAH family.…”

Ionic fragmentation products of benzonitrile as important intermediates in the growth of polycyclic aromatic hydrocarbons

“…S2, ESI †). [52][53][54] The non-covalent interactions present for some of the reaction products have been calculated using NCI analysis 55 with Multiwfn 56 using the reduced electron density gradient:…”