Reactions of a distonic peroxyl radical anion influenced by SOMO–HOMO conversion: an example of anion-directed channel switching

So, Sui; Kirk, Benjamin B.; Wille, Uta; Trevitt, Adam J.; Blanksby, Stephen J.; Silva, Gabriel da

doi:10.1039/c9cp05989j

Cited by 10 publications

(7 citation statements)

References 29 publications

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“…Furthermore, gas-phase ion–molecule reactions can often exhibit negative temperature dependence (i.e., increased reaction efficiency with lower temperature) , thus reinforcing their importance in low-temperature and low-pressure environments of the interstellar medium and extraterrestrial atmospheres such as Titan. Charge-effects can influence rates of reaction, and there is an increase in research into the controlled use of orientated electric fields (OEFs) to enhance and catalyze reactivity, − and this includes charge-effects on radical reactivity. − …”

Section: Introductionmentioning

confidence: 99%

Reactivity Trends in the Gas-Phase Addition of Acetylene to the N-Protonated Aryl Radical Cations of Pyridine, Aniline, and Benzonitrile

Shiels

Kelly

Bright

et al. 2021

J. Am. Soc. Mass Spectrom.

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A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N-containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion−molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl), and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta, and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios, and reaction efficiencies are measured. The rate coefficients increase from para to ortho positions. The second-order rate coefficients can be sorted into three groups: low, between 1 and 3 × 10 −12 cm 3 molecule −1 s −1 (3Anl and 4Anl); intermediate, between 5 and 15 × 10 −12 cm 3 molecule −1 s −1 (2Bzn, 3Bzn, and 4Bzn); and high, between 8 and 31 × 10 −11 cm 3 molecule −1 s −1 (2Anl, 2Pyr, 3Pyr, and 4Pyr); and 2Anl is the only radical cation with a rate coefficient distinctly different from its isomers. Quantum chemical calculations, using M06-2X-D3(0)/6-31++G(2df,p) geometries and DSD-PBEP86-NL/aug-cc-pVQZ energies, are deployed to rationalize reactivity trends based on the stability of prereactive complexes. The G3X-K method guides the assignment of product ions following adduct formation. The rate coefficient trend can be rationalized by a simple model based on the prereactive complex forward barrier height.

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Section: Introductionmentioning

confidence: 99%

Reactivity Trends in the Gas-Phase Addition of Acetylene to the N-Protonated Aryl Radical Cations of Pyridine, Aniline, and Benzonitrile

Shiels

Kelly

Bright

et al. 2021

J. Am. Soc. Mass Spectrom.

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“…According to the Aufbau principle, singly occupied molecular orbitals (SOMOs) have a higher energy than doubly occupied molecular orbitals in the most stable electronic configuration of ground-state molecules. However, SOMO–highest occupied molecular orbital (HOMO)-converted molecules, in which the SOMO has a lower energy than the HOMO, have been reported in radicals such as metal complexes, , distonic anion radicals, − nitroxides, − and some stable tris(2,4,6-trichlorophenyl)methyl derivatives. , The generation of high-spin molecules from monoradicals through oxidation and the switching of bond dissociation energy are of particular interest in the chemistry of SOMO–HOMO-converted molecules. Although the reactivity of SOMO–HOMO-converted molecules has attracted considerable attention in radical chemistry, only a limited number of organic molecules have been reported to date.…”

Section: Introductionmentioning

confidence: 99%

SOMO–HOMO Conversion in Triplet Cyclopentane-1,3-diyl Diradicals

2021

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According to the Aufbau principle, singly occupied molecular orbitals (SOMOs) are energetically higher lying than a highest doubly occupied molecular orbital (HOMO) in the electronically ground state of radicals. However, in the last decade, SOMO–HOMO-converted species have been reported in a limited group of radicals, such as distonic anion radicals and nitroxides. In this study, SOMO–HOMO conversion was observed in triplet 2,2-difluorocyclopentane-1,3-diyl diradicals DR3F1, DR4F1, and 2-fluorocyclopentante-1,3-diyl diradical DR3HF1, which contain the anthracyl unit at the remote position. The high HOMO energy in the anthracyl moiety and the low-lying SOMO–1 due to the fluoro-substituent effect are the key to the SOMO–HOMO conversion phenomenon. Furthermore, the cation radical DR3F1 + generated through the one-electron oxidation of DR3F1 was found to be a SOMO–HOMO-converted monoradical.

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“…The reactivity of peroxide radicals with SHC configurations was reported by Silva and co-workers in 2020. [24] They studied the reaction of CH 2 CH(OH)CH 2 C(O)Owith O 2 using ion-trap MS in the gas phase and suggested a possible reaction mechanism (Fig. 7).…”

Section: Distonic Radical Anionsmentioning

confidence: 99%

Singly Occupied Molecular Orbital−Highest Occupied Molecular Orbital (SOMO−HOMO) Conversion

2021

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Singly occupied molecular orbital−highest occupied molecular orbital (SOMO−HOMO) conversion (inversion), SHC, is a phenomenon in which the SOMO is lower in energy than the doubly occupied molecular orbitals (DOMO, HOMO). A non-Aufbau electronic structure leads to unique properties such as a switch in bond dissociation energy and the generation of high-spin species on one-electron oxidation. In addition, the pronounced photostability of these species has been reported recently for application in organic light-emitting devices. In this review article, we summarise the chemistry of SOMO−HOMO converted (inverted) species reported to date.

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Reactions of a distonic peroxyl radical anion influenced by SOMO–HOMO conversion: an example of anion-directed channel switching

Abstract: Deprotonation of a remote site in a peroxyl radical energetically buries the singly occupied molecular orbital, suppressing radical-driven oxidation and promoting reactions involving the anion site.

Cited by 10 publications

References 29 publications

Reactivity Trends in the Gas-Phase Addition of Acetylene to the N-Protonated Aryl Radical Cations of Pyridine, Aniline, and Benzonitrile

Reactivity Trends in the Gas-Phase Addition of Acetylene to the N-Protonated Aryl Radical Cations of Pyridine, Aniline, and Benzonitrile

SOMO–HOMO Conversion in Triplet Cyclopentane-1,3-diyl Diradicals

Singly Occupied Molecular Orbital−Highest Occupied Molecular Orbital (SOMO−HOMO) Conversion

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