On the formation and vibronic spectroscopy of α-halobenzyl radicals in a supersonic expansion

Yao, J.; Bernstein, E. R.

doi:10.1063/1.474710

Cited by 21 publications

(10 citation statements)

References 34 publications

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“…Identification of the molecule(s) giving rise to the observed spectrum in the benzene discharge is not straightforward because many different isomers of C 7 H 7 exist. 14 The known benzyl radical electronic spectrum 6 does not correspond to the observed bands. Spectra were measured using different precursors in order to identify the band of the tropyl radical.…”

Section: Results and Structural Assignmentmentioning

confidence: 53%

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Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical

et al. 2002

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One color resonance enhanced two photon ionization spectra of the tropyl C 7 H 7 and C 7 D 7 radicals were recorded in a molecular beam. Tropyl was produced in a supersonic plasma source using different precursors to identify its vibronic bands. The vibronic system is assigned to the 2 E′′ 3 r X 2 E′′ 2 electronic transition with origin near 25 719 cm -1 . It covers 6 000 cm -1 revealing a large change of geometry due to a Jahn-Teller distortion in both the ground and the excited states. Ab initio calculations were carried out on the JahnTeller configurations to guide the assignment.

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Section: Results and Structural Assignmentmentioning

confidence: 53%

“…The tropyl radical has been poorly investigated compared to neutral benzyl. 6 Though the latter is more stable by only 40 kJ/mol, 7 tropyl is believed to convert rapidly to benzyl. Further data on tropyl may aid the investigation of such reactions by laser-based diagnosis.…”

Section: Introductionmentioning

confidence: 99%

Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical

et al. 2002

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“…A smaller blue shift (34 cm −1 ) was reported for the ␣-chlorobenzyl radical [17]. On the other hand, all ring-substituted benzyl radicals exhibit red shift of the origin band due to extension of the space available for electron delocalization, and this shift increases with number of substituents regardless of substituent type.…”

Section: Resultsmentioning

confidence: 87%

“…The laser excitation spectra of ␣-halo and ␣,␣-dihalobenzyl radicals were observed by Yao and Bernstein [17], who obtained rotational constants changes upon electronic excitation from an analysis of rotational contours. However, the data could not determine vibrational mode frequencies and electronic transition energy of the ␣,␣-dichlorobenzyl radical.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic evidence of α,α-dichlorobenzyl radical produced by corona discharge of benzotrichloride

Yoon

Chae

Lim

et al. 2015

Chemical Physics Letters

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“…The prototypical aromatic RSR is the benzyl radical, which has a rich history of theoretical and experimental studies. − One of the important aspects of the electronic spectroscopy of benzyl radical is its prominent vibronic coupling due to closely lying electronic states. Other studies have investigated the implications of substitution on the benzyl radical ring or radical site, and observed significant changes in the electronic state behavior. ,− …”

Section: Introductionmentioning

confidence: 99%

Jet-Cooled Spectroscopy of the α-Methylbenzyl Radical: Probing the State-Dependent Effects of Methyl Rocking Against a Radical Site

et al. 2013

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The state-dependent spectroscopy of α-methylbenzyl radical (α-MeBz) has been studied under jet-cooled conditions. Two-color resonant two-photon ionization (2C-R2PI), laser-induced fluorescence, and dispersed fluorescence spectra were obtained for the D0-D1 electronic transition of this prototypical resonance-stabilized radical in which the methyl group is immediately adjacent to the primary radical site. Extensive Franck-Condon activity in hindered rotor levels was observed in the excitation spectrum, reflecting a reorientation of the methyl group upon electronic excitation. Dispersed fluorescence spectra from the set of internal rotor levels are combined with the excitation spectrum to obtain a global fit of the barrier heights and angular change of the methyl group in both D0 and D1 states. The best-fit methyl rotor potential in the ground electronic state (D0) is a flat-topped 3-fold potential (V3" = 151 cm(-1), V6" = 34 cm(-1)) while the D1 state has a lower barrier (V3' = 72 cm(-1), V6' = 15 cm(-1)) with Δφ = ± π/3, π, consistent with a reorientation of the methyl group upon electronic excitation. The ground state results are compared with calculations carried out at the DFT B3LYP level of theory using the 6-311+G(d,p) basis set, and a variety of excited state calculations are carried out to compare against experiment. The preferred geometry of the methyl rotor in the ground state is anti, which switches to syn in the D1 state and in the cation. The calculations uncover a subtle combination of effects that contribute to the shift in orientation and change in barrier in the excited state relative to ground state. Steric interaction favors the anti conformation, while hyperconjugation is greater in the syn orientation. The presence of a second excited state close by D1 is postulated to influence the methyl rotor properties. A resonant ion-dip infrared (RIDIR) spectrum in the alkyl and aromatic CH stretch regions was also recorded, probing in a complementary way the state-dependent conformation of α-MeBz. Using a scheme in which infrared depletion occurs between excitation and ionization steps of the 2C-R2PI process, analogous infrared spectra in D1 were also obtained, probing the response of the CH stretch fundamentals to electronic excitation. A reduced-dimension Wilson G-matrix model was implemented to simulate and interpret the observed infrared results. Finally, photoionization efficiency scans were carried out to determine the adiabatic ionization threshold of α-MeBz (IP = 6.835 ± 0.002 eV) and provide thresholds for ionization out of specific internal rotor levels, which report on the methyl rotor barrier in the cation state.

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On the formation and vibronic spectroscopy of α-halobenzyl radicals in a supersonic expansion

Abstract: 2 + 1 ) Resonance-enhanced ionization spectroscopy of a state-selected beam of OH radicals

Cited by 21 publications

References 34 publications

Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical

Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical

Spectroscopic evidence of α,α-dichlorobenzyl radical produced by corona discharge of benzotrichloride

Jet-Cooled Spectroscopy of the α-Methylbenzyl Radical: Probing the State-Dependent Effects of Methyl Rocking Against a Radical Site

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On the formation and vibronic spectroscopy of α-halobenzyl radicals in a supersonic expansion

Abstract: 2 + 1 ) Resonance-enhanced ionization spectroscopy of a state-selected beam of OH radicals

Cited by 21 publications

References 34 publications

Gas-Phase Electronic Spectrum of the Tropyl C7H7 Radical

Gas-Phase Electronic Spectrum of the Tropyl C7H7 Radical

Spectroscopic evidence of α,α-dichlorobenzyl radical produced by corona discharge of benzotrichloride

Jet-Cooled Spectroscopy of the α-Methylbenzyl Radical: Probing the State-Dependent Effects of Methyl Rocking Against a Radical Site

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Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical

Gas-Phase Electronic Spectrum of the Tropyl C₇H₇ Radical