Photodissociation spectroscopy of the negative ion dimer of toluquinone

Comita, Paul B.; Brauman, John I.

doi:10.1021/ja00259a001

Cited by 32 publications

(27 citation statements)

References 5 publications

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“…This result is consistent with Comita and Braumann: 19 in addition to the band at hν ~ 1.9 eV, they identified an intense dissociative band producing pTQ -with onset at hν ~ 2.7 eV. Given that photodissociation for (pTQ) 2 -must be competitive with the < 50 ns timescale of electron detachment, we assign the Boltzmann-like photoelectron distribution to delayed autodetachment.…”

supporting

confidence: 91%

“…1. We chose to study cluster anions of pTQ rather the nonmethylated para-benzoquinone (pBQ) because pTQ anions π-stack readily in the gas-phase at room temperature, 4,19 whereas (pBQ) 2 -is thought to have a non-π-stacked structure. 20 The experimental methodology, frequency-resolved photoelectron spectroscopy, involves recording a series of photoelectron spectra across a wide range of photon energies (hv), which, when considered holistically, provide fingerprints of the resonances and their associated dynamics.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of π*-resonances in anionic clusters of para-toluquinone

Bull

Verlet

2017

Phys. Chem. Chem. Phys.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Frequency-resolved photoelectron spectroscopy applied to mass-selected cluster anions is an insightful approach to characterise the dynamics of π*-resonances with microsolvation. Here, the technique demonstrated with monomer, dimer and trimer radical anions of para-toluquinone (pTQ) over a ~1 eV excitation window above the detachment threshold. The pTQ -spectra show similar resonances and dynamics to para-benzoquinone, a prototype electrophore. The dimer, (pTQ)2 -, has a π-stacked geometry and shows a competition between photodissociation and prompt autodetachment. The trimer, (pTQ)3 -, also has a π-stacked cluster geometry and shows vibrational autodetachment from a non-valence state up to ~0.7 eV above-threshold, outcompeting dissociation. At higher photoexcitation energies, (pTQ)3 -shows monomer-like dynamics, blue-shifted in photoexcitation energy by the cluster cohesion energy. Overall, the study highlights the variety of non-adiabatic dynamics available to π*-resonances and the profound changes that occur through clusterization with one and two monomers.

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supporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Dynamics of π*-resonances in anionic clusters of para-toluquinone

Bull

Verlet

2017

Phys. Chem. Chem. Phys.

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“…In Figure 2(a), each PE spectrum has been normalized to the relative total photoelectron cross sections of Brauman and co-workers. 25 The total integrated cross section increases rapidly for hv > 3.8 eV as evidenced by the prominence of the feature at high eKE in Figure 2(a). The cross section for direct detachment as a function of eKE is expected to be a smoothly increasing function and the sharp increase observed suggests that a resonance is accessed at these photon energies.…”

Section: Resultsmentioning

confidence: 88%

“…21 Finally, Brauman and co-workers have reported low resolution total photodetachment cross sections with photon energies up to ~4.6 eV, identifying two broad maxima centered at ~3.0 eV and ~4.1 eV, as well as the onset of an intense band starting at ~4.4 eV. 25,26 5 pBQ has also been the subject of a number of electron attachment and transmission studies, which have identified at least three resonances centered at 0.7 eV, 1.4 eV and ~2.0 eV above the ground state of the neutral, with the latter producing radical anions that survive for at least several microseconds. 8,12-14 Although some vibrational structure could be discerned in these experiments, on the whole, the bands are very broad and overlapping.…”

Section: Introductionmentioning

confidence: 99%

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

et al. 2014

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract:The resonant attachment of a free electron to a closed shell neutral molecule, and the interplay between the following electron detachment and electronic relaxation channels represents a fundamental but common process throughout chemical and biochemical systems. The new methodology of anion frequency-resolved photoelectron imaging is detailed and used to map-out molecular excited state dynamics of gas-phase para-benzoquinone, which is the electron accepting moiety in many biological electron-transfer chains. Three-dimensional spectra of excitation energy, electron kinetic energy and electron ejection anisotropy reveal clear fingerprints of excited and intermediate state dynamics. The results show that many of the excited states are strongly coupled, providing a route to forming the ground state radical anion, despite the fact that the electron is formally unbound in the excited states. The relation of our method to electron impact attachment studies and the key advantages, including the extension to time-resolved dynamics and to larger molecular systems is discussed.

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“…However, we can hypothesise that mechanism (iii) is unlikely based on experimental trends of total PE yield across other related systems and electron attachment experiments of related species. 44 For example, both CQ 0 and pBQ have similar: electronic structure, geometries, electron affinities, resonances and calculated oscillator strengths; and only one accessible neutral detachment continuum. In addition, we did not observe any sudden changes in the β 2 parameters that would support a sudden increase in the relative contributions.…”

Section: Comparison With Para-benzoquinonementioning

confidence: 99%

Anion resonances and above-threshold dynamics of coenzyme Q₀

Bull

West

Verlet

2015

Phys. Chem. Chem. Phys.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Temporary radical anions (resonances) of isolated co-enzyme Q 0 (CQ 0 ) and their associated above-threshold dynamics have been studied using frequency-, angle-, and time-resolved photoelectron imaging (FAT-PI). Experimental energetics and dynamics are supported with ab initio calculations. All results support that CQ 0 exhibits similar resonances and energetics compared with the smaller para-benzoquinone subunit, which is commonly considered as a prototype electrophore for larger biological para-quinone species. However, the abovethreshold dynamics in CQ 0 relative to para-benzoquinone show significantly enhanced prompt detachment compared with internal conversion, particularly around the photoexcitation energy of 3.10 eV. The change in dynamics can be attributed to a combination of an increase in the shape character of the optically-accessible resonance at this energy, a decrease in the autodetachment lifetime due to the higher density of states in the neutral, and a decrease in the probability that the wavepacket formed in the FranckCondon window can access the local conical intersection in CQ 0 over the timescale of autodetachment. Overall, this study serves as a clear example in understanding the trends in spectroscopy and dynamics in relating a simple prototypical para-quinone electrophore to a more complex biochemical species.

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Photodissociation spectroscopy of the negative ion dimer of toluquinone

Cited by 32 publications

References 5 publications

Dynamics of π*-resonances in anionic clusters of para-toluquinone

Dynamics of π*-resonances in anionic clusters of para-toluquinone

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

Anion resonances and above-threshold dynamics of coenzyme Q₀

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Photodissociation spectroscopy of the negative ion dimer of toluquinone

Cited by 32 publications

References 5 publications

Dynamics of π*-resonances in anionic clusters of para-toluquinone

Dynamics of π*-resonances in anionic clusters of para-toluquinone

Anion Resonances of para-Benzoquinone Probed by Frequency-Resolved Photoelectron Imaging

Anion resonances and above-threshold dynamics of coenzyme Q0

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Product

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Anion resonances and above-threshold dynamics of coenzyme Q₀