Slow Photoelectron Velocity-Map Imaging Spectroscopy of the<i>ortho</i>-Hydroxyphenoxide Anion

Weichman, Marissa L.; Kim, Jongjin B.; Neumark, Daniel M.

doi:10.1021/acs.jpca.5b00768

Cited by 12 publications

(10 citation statements)

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“…High-resolution peak widths are typically 4-5 cm −1 FWHM for the ground states of all three anthracenyl radicals and as narrow as 2-3 cm −1 FWHM. This constitutes a notable improvement in instrumental resolution over previous cryo-SEVI studies of aromatic molecules, where the narrowest features were more often 7-8 cm −1 FWHM (17,36). Peaks indicating some contamination of the 1-anthracenyl isomer in the 2-anthracenyl spectrum are plotted in gray in Fig.…”

Section: Resultsmentioning

confidence: 89%

“…The cryo-SEVI technique used here is a high-resolution variant of PES and yields spectra of complex anions with sub-meV resolution (17,35,36). Specific anthracenyl anion isomers are prepared using trimethylsilyl-anthracene precursors and cooled to cryogenic temperatures (∼10 K) before photodetachment, eliminating hot spectral features and narrowing the rotational profiles of the observed peaks.…”

Section: Significancementioning

confidence: 99%

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Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

Weichman

DeVine

Levine

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Polycyclic aromatic hydrocarbons, in various charge and protonation states, are key compounds relevant to combustion chemistry and astrochemistry. Here, we probe the vibrational and electronic spectroscopy of gas-phase 9-, 1-, and 2-anthracenyl radicals (C 14 H 9 ) by photodetachment of the corresponding cryogenically cooled anions via slow photoelectron velocity-map imaging (cryo-SEVI). The use of a newly designed velocity-map imaging lens in combination with ion cooling yields photoelectron spectra with <2 cm −1 resolution. Isomer selection of the anions is achieved using gasphase synthesis techniques, resulting in observation and interpretation of detailed vibronic structure of the ground and lowest excited states for the three anthracenyl radical isomers. The groundstate bands yield electron affinities and vibrational frequencies for several Franck-Condon active modes of the 9-, 1-, and 2-anthracenyl radicals; term energies of the first excited states of these species are also measured. Spectra are interpreted through comparison with ab initio quantum chemistry calculations, Franck-Condon simulations, and calculations of threshold photodetachment cross sections and anisotropies. Experimental measures of the subtle differences in energetics and relative stabilities of these radical isomers are of interest from the perspective of fundamental physical organic chemistry and aid in understanding their behavior and reactivity in interstellar and combustion environments. Additionally, spectroscopic characterization of these species in the laboratory is essential for their potential identification in astrochemical data.polycyclic aromatic hydrocarbons | anion photoelectron spectroscopy | velocity-map imaging | vibronic structure P olycyclic aromatic hydrocarbons (PAHs) are an important class of species in many areas of chemistry. They are major components in coal (1) and in soot formed from combustion of organic matter (2, 3). PAHs are therefore common environmental pollutants and have well-documented mutagenic and carcinogenic biological activity (4, 5). PAHs are also believed to be abundant in the interstellar medium (6) and may be carriers of the anomalous IR emission bands (7-9). Recent molecular beam studies indicate that PAH growth can proceed through cold collisions of smaller hydrocarbons under interstellar conditions (10, 11). Individual PAH molecules can subsequently provide nucleation sites for amorphous graphitic grains (9). Interstellar PAHs and their clusters therefore bridge the gap between small carbonaceous molecules and larger particles, analogous to their role in soot condensation in combustion environments (12).In space, PAH species are likely to exist as an equilibrium of neutral and ionic charge states, with varying degrees of hydrogenation and dehydrogenation (13-15). Models of dense interstellar clouds find that anionic PAHs are the major carriers of negative charge, rather than free electrons (16). Closed-shell, singly deprotonated PAH carbanions have large electron affinities compared with ...

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Section: Resultsmentioning

confidence: 89%

Section: Significancementioning

confidence: 99%

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

Weichman

DeVine

Levine

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Hydroxyphenoxide, a close analog of methylphenoxide, has also been recently studied. 63,64 Autodetachment was observed in the photoelectron spectrum of ohydroxyphenoxide, again attributed to a dipole bound anion electronic excited state. 63 In the current study, the m-and p-methylphenoxide anions both display signatures of electron autodetachment.…”

Section: Discussionmentioning

confidence: 96%

Anion photoelectron spectroscopy of deprotonated ortho-, meta-, and para-methylphenol

Nelson

Gichuhi

Miller

et al. 2017

The Journal of Chemical Physics

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The anion photoelectron spectra of ortho-, meta-, and para-methylphenoxide, as well as methyl deprotonated meta-methylphenol, were measured. Using the Slow Electron Velocity Map Imaging (SEVI) technique, the Electron Affinities (EAs) of the o-, m-, and p-methylphenoxyl radicals were measured: 2.1991 ± 0.0014, 2.2177 ± 0.0014, and 2.1199 ± 0.0014 eV, respectively. The EA of mmethylenephenol was also obtained, 1.024 ± 0.008 eV. In all four cases, the dominant vibrational progressions observed are due to several ring distortion vibrational normal modes that were activated upon photodetachment, leading to vibrational progressions spaced by ~500 cm -1 . Using the

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“…34,35 By cooling ions to internal temperatures of ∼10 K prior to detachment (cryo-SEVI), rotational broadening and spectral congestion are minimized, yielding transitions as narrow as 1.2 cm −1 FWHM that reflect the vibronic structure of the corresponding neutral. 36,37 Cryo-SEVI has been highly successful in revealing subtleties in the vibronic structure of a number of aromatic radicals; 32,[38][39][40][41] in cases where multiple radical isomers are possible, reaction of appropriate trimethylsilyl (TMS) substituted precursors with fluoride anions has enabled acquisition of isomer-specific spectra. 32,40,41 Here, we use this approach to obtain cryo-SEVI spectra for the three anion isomers of deprotonated pyridine.…”

Section: Introductionmentioning

confidence: 99%

High-resolution photoelectron spectroscopy of the pyridinide isomers

DeVine

Babin

Blackford

et al. 2019

The Journal of Chemical Physics

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Isomer-specific, high-resolution photoelectron spectra of cryogenically cooled pyridinide anions obtained using slow photoelectron velocitymap imaging are presented. New vibrational structure in the detachment spectrum of para-pyridinide is resolved, and the spectra of metaand ortho-pyridinide are reported for the first time. These spectra yield electron affinities of 1.4797(5), 1.4473(5), and 0.8669(7) eV for the para-, meta-, and ortho-pyridyl radicals, respectively, as well as a number of vibrational frequencies for each neutral isomer. While most of the resolved structure in all three spectra is readily assigned by comparison to B3LYP/6-311+G * Franck-Condon simulations, the para-pyridinide spectrum shows newly resolved fine structure attributed to anharmonic coupling within the vibrational manifold of the corresponding neutral radical. Isomeric trends in the photoelectron angular distributions are rationalized by approximating the detached anion orbitals as superpositions of s-, p-, and d-like hydrogenic orbitals, based on an application of Sanov's generalized mixing model [D. Khuseynov et al., J. Chem. Phys. 141, 124312 (2014)]. The presented experimental and theoretical results are used to address the relative energies of the anion and neutral isomers, as well as the site-specific bond dissociation energies of pyridine.Published under license by AIP Publishing. https://doi.

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Slow Photoelectron Velocity-Map Imaging Spectroscopy of theortho-Hydroxyphenoxide Anion

Cited by 12 publications

References 58 publications

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

Isomer-specific vibronic structure of the 9-, 1-, and 2-anthracenyl radicals via slow photoelectron velocity-map imaging

Anion photoelectron spectroscopy of deprotonated ortho-, meta-, and para-methylphenol

High-resolution photoelectron spectroscopy of the pyridinide isomers

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