The ground state (1A1) and the lowest triplet state (3B1) of the phenyl cation C6H5+ revisited

Hrušák, Jan; Schröder, Detlef; Iwata, Suehiro

doi:10.1063/1.473757

Cited by 50 publications

(21 citation statements)

References 36 publications

(29 reference statements)

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“…The ionization of phenyl radical may involve the removal of the unpaired electron from the localized orbital of the bare C atom or an electron from the orbital of the six-carbon ring structure, resulting in the singlet C 6 H 5 + ͑ 1 A 1 ͒ and triplet C 6 H 5 + ͑ 3 B 1 ͒ cationic states, respectively. Previous theoretical studies 51,52 indicate that the triplet phenyl cation C 6 H 5 + ͑ 3 B 1 ͒ is higher in energy than the singlet phenyl cation C 6 H 5 + ͑ 1 A 1 ͒ by Ϸ0.8− 0.9 eV. The structure of the C 6 H 5 + ͑ 3 B 1 ͒ cation is expected to be similar to that of phenyl radical.…”

Section: B Ionization Energy Of C 6 H 5 and Heats Of Formation Of C mentioning

confidence: 84%

Accurate ab initio predictions of ionization energies and heats of formation for the 2-propyl, phenyl, and benzyl radicals

Lau

2006

The Journal of Chemical Physics

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The ionization energies (IEs) for the 2-propyl (2-C(3)H(7)), phenyl (C(6)H(5)), and benzyl (C(6)H(5)CH(2)) radicals have been calculated by the wave-function-based ab initio CCSD(T)/CBS approach, which involves the approximation to the complete basis set (CBS) limit at the coupled cluster level with single and double excitations plus quasiperturbative triple excitation [CCSD(T)]. The zero-point vibrational energy correction, the core-valence electronic correction, and the scalar relativistic effect correction have been also made in these calculations. Although a precise IE value for the 2-C(3)H(7) radical has not been directly determined before due to the poor Franck-Condon factor for the photoionization transition at the ionization threshold, the experimental value deduced indirectly using other known energetic data is found to be in good accord with the present CCSD(T)/CBS prediction. The comparison between the predicted value through the focal-point analysis and the highly precise experimental value for the IE(C(6)H(5)CH(2)) determined in the previous pulsed field ionization photoelectron (PFI-PE) study shows that the CCSD(T)/CBS method is capable of providing an accurate IE prediction for C(6)H(5)CH(2), achieving an error limit of 35 meV. The benchmarking of the CCSD(T)/CBS IE(C(6)H(5)CH(2)) prediction suggests that the CCSD(T)/CBS IE(C(6)H(5)) prediction obtained here has a similar accuracy of 35 meV. Taking into account this error limit for the CCSD(T)/CBS prediction and the experimental uncertainty, the CCSD(T)/CBS IE(C(6)H(5)) value is also consistent with the IE(C(6)H(5)) reported in the previous HeI photoelectron measurement. Furthermore, the present study provides support for the conclusion that the CCSD(T)/CBS approach with high-level energy corrections can be used to provide reliable IE predictions for C(3)-C(7) hydrocarbon radicals with an uncertainty of +/-35 meV. Employing the atomization scheme, we have also computed the 0 K (298 K) heats of formation in kJ/mol at the CCSD(T)/CBS level for 2-C(3)H(7)/2-C(3)H(7) (+) ,C(6)H(5)/C(6)H(5) (+), and C(6)H(5)CH(2)/C(6)H(5)CH(2) (+) to be 105.2/822.7 (90.0/806.4), 351.4/1148.5 (340.4/1138.8), and 226.2/929.0 (210.3/912.7), respectively. Comparing these values with the available experimental values, we find that the discrepancies for the 0 and 298 K heats of formation values are < or =2.6 kJ/mol for 2-C(3)H(7)/2-C(3)H(7) (+),< or =4.1 kJ/mol for C(6)H(5)/C(6)H(5) (+), and < or =3.2 kJ//mol for C(6)H(5)CH(2)C(6)H(5)CH(2) (+).

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Section: B Ionization Energy Of C 6 H 5 and Heats Of Formation Of C mentioning

confidence: 84%

Accurate ab initio predictions of ionization energies and heats of formation for the 2-propyl, phenyl, and benzyl radicals

Lau

2006

The Journal of Chemical Physics

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“…Several of its electronic properties have been measured, including its ultraviolet absorption spectrum, 13,14 ionization potential, 15,16 photoionization cross section, 17 and electron affinity. 18 The electronic states and vibronic spectra of the phenyl radical have also been calculated.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the photodissociation dynamics of the phenyl radical

Cole-Filipiak

Shapero

Negru

et al. 2014

The Journal of Chemical Physics

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We have reinvestigated the photodissociation dynamics of the phenyl radical at 248 nm and 193 nm via photofragment translational spectroscopy under a variety of experimental conditions aimed at reducing the nascent internal energy of the phenyl radical and eliminating signal from contaminants. Under these optimized conditions, slower translational energy (P(E(T))) distributions for H-atom loss were seen at both wavelengths than in previously reported work. At 193 nm, the branching ratio for C2H2 loss vs. H-atom loss was found to be 0.2 ± 0.1, a significantly lower value than was obtained previously in our laboratory. The new branching ratio agrees with calculated Rice-Ramsperger-Kassel-Marcus rate constants, suggesting that the photodissociation of the phenyl radical at 193 nm can be treated using statistical models. The effects of experimental conditions on the P(E(T)) distributions and product branching ratios are discussed.

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“…Transfer of an electron from the π‐system to the empty σ‐orbital6 restores the sp 2 hybridization at the cost of forming a triplet ( 3 B 1 ) electronic state and sacrificing the aromaticity of the system 4. By now, a singlet ( 1 A 1 ) ground state about 77 kJ mol −1 lower in energy than the triplet has been firmly established 7…”

Section: Methodsmentioning

confidence: 94%

“…Values for the singlet–triplet energy gap obtained using other computational methods indeed show significant scatter, favoring the triplet state (PM3,17 CISD, ROHF,18 HF19) or the singlet state (MP2,19 CCSD(T)15) by substantial amounts. This result suggests that a multireference approach as has been applied to the phenyl7 and vinyl13 cations may be required in this case as well. On the other hand, the study on substituted vinyl cations found good agreement between DFT and CASPT2 values for the singlet–triplet gap,13 encouraging the use of low‐cost DFT methods.…”

Section: Methodsmentioning

confidence: 99%

“…It may be wondered whether there are propensities that preferentially form one of the two electronic states in the CBr bond cleavage. For instance, formation of the phenyl cation from the neutral C 6 H 5 ⋅ radical by photoionization favors the higher‐energy triplet state due to better Franck–Condon overlap 7. Analogously, homolytic bond cleavage in the C 10 H 7 Br + radical cation would lead to the triplet naphthyl cation.…”

Section: Methodsmentioning

confidence: 99%

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