Spectroscopic Detection of Cyano-Cyclopentadiene Ions as Dissociation Products upon Ionization of Aniline

Abstract

The H-loss products (C 6 H 6 N + ) from the dissociative ionization of aniline (C 6 H 7 N) have been studied by infrared predissociation spectroscopy in a cryogenic ion trap instrument at the free electron laser for infrared experiments (FELIX) laboratory. Broadband and narrow line width vibrational spectra in the spectral fingerprint region of 550–1800 cm –1 have been recorded. The comparison to calculated spectra of the potential isomeric structures of the fragment ions reveals that the dominant fragments are five-membered cyano-cyclopentadiene ions. Computed C 6 H 7 N •+ potential energy surfaces suggest that the dissociation path leading to H loss starts with an isomerization process, following a similar trajectory as the one leading to HNC loss. The possible presence of cyano-cyclopentadiene ions and related five-membered ring species in Titan’s atmosphere and the interstellar medium are discussed.

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

“…For the dissociative ionization of aniline, it has been observed that the H and HNC loss channels are coupled via the same intermediate structures. 32 In that case, no direct H-loss was observed, but both H-migration and isomerization steps occurred prior to the loss of a hydrogen atom. Although the end products of the HNC loss pathway are energetically less favourable, the intermediates such as iC1 and iC3 are significantly lower in energy than their corresponding structures on the HCN pathway.…”

“…The identified structures of the H-loss fragments of benzonitrile suggest a direct H-loss mechanism. In contrast to pyridine (and aniline 32 ) no precursor for H-loss can therefore be observed in the PES.…”

“…A variety of studies has been investigating the fragmentation processes of astronomical relevant molecules in detail ranging from theoretical [29][30][31] to experimental studies using dissociative ionization and infrared spectroscopy [32][33][34][35][36][37] or imaging Photoelectron-Photoion-Coincidence (iPEPICO) spectroscopy [38][39][40] . By using a combination of techniques, some of these studies have provided structural information of the fragment ions.…”

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

“…Other studies have been looking into the destruction processes of astronomical relevant species to understand their stability and fragmentation processes. [17][18][19][20][21][22][23][24][25][26][27][28] Fragmentation processes are shown to play a role for the astronomically detected Buckminsterfullerenes C 60 , C 70 and C 60 + that are thought to be formed via top-down chemistry from large PAHs. 3,29,30 In a chemical environment like the interstellar medium the fragmentation and formation reactions are strongly intertwined.…”

10 Years of the ACS PHYS Astrochemistry Subdivision

“…Most notably, one manuscript reports that silicon carbide grains in conditions like those found in late-stage circumstellar envelopes will produce buckyballs and nanotubes, confirming in large part Nobel Laureate Sir Harry Kroto’s original idea about the astrophysical formation of these carbon allotropes. Examples of other novel molecules with potential astrochemical significance include 2-aza-1,3-butadiene, the C 7 H 5 radical, functionalized buckyballs in the form of C 60 O + and C 60 OH + , the 1-quinolinium (C 9 H 7 NH + ) cation along with its corresponding neutral and hydrogenated radicals, cyano-cyclopentadiene ions, the simplest aminooxycarbene in aminohydroxymethylene (H 2 N–C̈–OH), 1-cyanocyclobutene (C 5 H 5 N), monocyclic carbon ring cations of the form C 2 n + , the phenalenyl radical, and isomers of the PAH C 16 H 10 + . Purely theoretical studies are providing characterization for other unique molecules including glycolic acid, pyridyl radicals, and diazirine along with its cyclic isomers .…”