Interplay of Open-Shell Spin-Coupling and Jahn–Teller Distortion in Benzene Radical Cation Probed by X-ray Spectroscopy

Vidal, Marta L.; Epshtein, Michael; Scutelnic, Valeriu; Yang, Zheyue; Xue, Ting; Leone, Stephen R.; Krylov, Anna I.; Coriani, Sonia

doi:10.1021/acs.jpca.0c08732

Cited by 52 publications

(79 citation statements)

References 91 publications

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“…40,41 The first peak at 285.2 eV, labeled as A, is the most intense feature and is known as the transition from the 1sC orbital to the π*(e2u) LUMOs, 42 as can be seen in the energy diagram in Fig 1(c). Peaks B, C and D are due to core-to-Rydberg transitions, as also discussed in detail in the companion theoretical paper, 29 which corrects a previously debated assignment of peak D as a transition to a higher π*(b1g) orbital, 35,38,39,43 to the new assignment of doubly degenerate transitions to Ry(s) and Ry(p) character.…”

Section: Resultssupporting

confidence: 64%

“…27,28 In addition, each of the 1s→π* transitions can be split due to spin coupling in the presence of the partially vacant π orbital, as explained in the companion theoretical paper. 29 Analogous splittings were recently reported in N2 + , 30 as well as at the O Kedge of CO + . 31 In N2 + , the features at 402.2 eV and 403.1 eV correspond to the π* excitation, as assigned through x-ray absorption spectroscopy (XAS) of neutral nitrogen molecules, but with a 3σg spectator hole in the case of the ion, i.e., a 3σg −1 2 Σg → 1σu −1 3σg −1 1πg 2 Πu transition.…”

Section: Introductionsupporting

confidence: 71%

“…The difference can be partly explained by changes in orbital energies (i.e., a decrease of the π* orbital (0.25 eV) and an increase of the semi-occupied π orbital in the cation, which occur as a result of the symmetry distortion) and partly by exchange interactions arising due to the spin couplings of the unpaired electrons, as discussed further in the companion theoretical paper. 29 The preparation of benzene cation in the electronic ground state and the exclusion of possible contributions due to one photon excitation of neutral benzene or three photon or more electronically excited cations are important points for further discussion. It is always a challenging problem to limit an ionization process in an intense field to just two UV photons, nevertheless the two-photon ionization with 267 nm is known to be very effective in benzene.…”

Section: Resultsmentioning

confidence: 99%

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Table-Top X-ray Spectroscopy of Benzene Radical Cation

Epshtein

Scutelnic²,

Yang³

et al. 2020

Preprint

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Ultrafast table-top x-ray spectroscopy <a>at the carbon K-edge </a>is used to measure the x-ray spectral features of benzene <a>radical cations (Bz+). The ground state of the cation is prepared selectively by </a><a>two-photon ionization of neutral benzene, and the x-ray spectra are probed at early times after the ionization by transient absorption using x-rays produced by high harmonic generation (HHG). </a><a>Bz+ is well known to undergo Jahn-Teller </a>distortion, leading to a lower symmetry and splitting of the π orbitals. Comparison of the x-ray absorption spectra of the neutral and the cation reveals a splitting of the two degenerate π* orbitals as well as an appearance of a new peak due to excitation to the partially occupied π -subshell. The <a>π*</a> orbital splitting of the cation, elucidated on the basis of high-level calculations in a companion theoretical paper [Vidal et al, submitted to J. Phys. Chem. Lett.; ChemRxiv link: doi XXXXX], is discovered to be due to both the symmetry distortion and even more dominant spin coupling of the unpaired electron in the partially vacant π orbital (from ionization) with the unpaired electrons resulting from the transition from the 1sC core orbital to the fully vacant <a>π* </a>orbitals.

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Section: Resultssupporting

confidence: 64%

Section: Introductionsupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

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Table-Top X-ray Spectroscopy of Benzene Radical Cation

Epshtein

Scutelnic²,

Yang³

et al. 2020

Preprint

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“…Quite recently, the structure of the benzene cation radical has been elucidated by Table-Top X-ray spectroscopy accompanied by high-level equation-of-motion coupled-cluster calculations [100,101]. It appears that in the benzene cation radical, there is a splitting of the two degenerate π* orbitals manifested by a new peak coming from an excitation to the partially occupied π-subshell.…”

Section: Geometrymentioning

confidence: 99%

Substituent Effect in the Cation Radicals of Monosubstituted Benzenes

Dobrowolski

Dudek

Karpińska

et al. 2021

IJMS

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In 30 monosubstituted benzene cation radicals, studied at the ωB97XD/aug-cc-pVTZ level, the phenyl rings usually adopt a compressed form, but a differently compressed form—equivalent to an elongated one—may coexist. The computational and literature ionization potentials are well correlated. The geometrical and magnetic aromaticity, estimated using HOMA and NICS indices, show the systems to be structurally aromatic but magnetically antiaromatic or only weakly aromatic. The partial charge is split between the substituent and ring and varies the most at C(ipso). In the ring, the spin is 70%, concentrated equally at the C(ipso) and C(p) atoms. The sEDA(D) and pEDA(D) descriptors of the substituent effect in cation radicals, respectively, were determined. In cation radicals, the substituent effect on the σ-electron system is like that in the ground state. The effect on the π-electron systems is long-range, and its propagation in the radical quinone-like ring is unlike that in the neutral molecules. The pEDA(D) descriptor correlates well with the partial spin at C(ipso) and C(p) and weakly with the HOMA(D) index. The correlation of the spin at the ring π-electron system and the pEDA(D) descriptor shows that the electron charge supplied to the ring π-electron system and the spin flow oppositely.

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“…This is followed by low intensity Rydberg transitions at higher photon energies. 62 Due to symmetry, the vertical transitions that contribute to the first XAS peak correspond to six nearly degenerate core-excitations, out of which only one has non-zero oscillator strength. Although the ground state (GS) PES leads to an equilibrium molecular configuration with a high symmetry, the core-excited PES has six potential wells with slight distortions corresponding to Jahn-Teller minima.…”

Section: A X-ray Absorption Spectramentioning

confidence: 99%

Analytical Gradients for Core-Excited States in the Algebraic Diagrammatic Construction (ADC) Framework

Brumboiu

Rehn²,

Dreuw³

et al. 2021

Preprint

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Here we present a derivation of the analytical expressions required to determine nuclear gradients for core-excited states at the core-valence separated algebraic diagrammatic construction (CVS-ADC) theory level. Analytical gradients up to and including the extended CVS-ADC(2)-x order have been derived and implemented into a Python module, adc_gradient. The gradients were used to determine core-excited state optimized geometries and relaxed potential energy surfaces for the water, formic acid, and benzne molecules.

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Interplay of Open-Shell Spin-Coupling and Jahn–Teller Distortion in Benzene Radical Cation Probed by X-ray Spectroscopy

Abstract: download file view on ChemRxiv manuscript_benzene-theory.pdf (1.45 MiB) download file view on ChemRxiv manuscript_benzene-theory-SI.pdf (2.17 MiB)

Cited by 52 publications

References 91 publications

Table-Top X-ray Spectroscopy of Benzene Radical Cation

Table-Top X-ray Spectroscopy of Benzene Radical Cation

Substituent Effect in the Cation Radicals of Monosubstituted Benzenes

Analytical Gradients for Core-Excited States in the Algebraic Diagrammatic Construction (ADC) Framework

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