Reactivity of an Aromatic σ,σ,σ‐Triradical: The 2,4,6‐Tridehydropyridinium Cation

Jankiewicz, Bartłomiej J.; Adeuya, Anthony; Mj, Yurkovich; Vinueza, Nelson R.; Sj, Gardner; Zhou, Meng; Jj, Nash; Hi, Kenttämaa

doi:10.1002/anie.200701732

Cited by 28 publications

(72 citation statements)

References 24 publications

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“…The 2,4,6-tridehydropyridinium cation ( 86 ) was found 311 to form products similar to those of the related mono- and diradicals. However, it reacts with most reagents more efficiently than related biradicals and at about equal efficiency as related monoradicals.…”

Section: Properties and Reactivitymentioning

confidence: 93%

“…Apparently, the large EA v of 86 counterbalances most of the radical reactivity hindering effect caused by the coupling of the three unpaired electrons. 311 …”

Section: Properties and Reactivitymentioning

confidence: 99%

“…311–314 However, the reported reactivity studies are limited only to five different tridehydropyridinium cations. 311–314 This limited amount of data may not be sufficient to make definite conclusions on what factors control the reactivity of these reactive species. However, possible reactivity controlling factors are discussed below.…”

Section: Properties and Reactivitymentioning

confidence: 99%

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Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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Section: Properties and Reactivitymentioning

confidence: 93%

“…Apparently, the large EA v of 86 counterbalances most of the radical reactivity hindering effect caused by the coupling of the three unpaired electrons. 311 …”

Section: Properties and Reactivitymentioning

confidence: 99%

Section: Properties and Reactivitymentioning

confidence: 99%

See 1 more Smart Citation

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

et al. 2013

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“…Electron spin resonance experiments and multi reference multi state MS-CASPT2 quantum chemical computations suggest that this trication also has a D 3h symmetry, high-spin 4 A 00 2 ground state, and the corresponding low spin 2 A 2 and 2 B 1 states are lying 35.1 and 33.0 kJ/mol above the ground state, respectively. Substituent effects on the electronic structure and the properties of triradicals have been studied using both experimental [17,18] and theoretical [1,5,6] methods. Most of these studies have however been restricted to nitrogen substitution.…”

Section: Introductionmentioning

confidence: 99%

Tuning the position of unpaired electrons and doublet–quartet gap of the 1,3,5-trimethylenebenzene triradical by nitrogen, phosphorus and arsenic substitution

Höltzl

Veszprémi

Nguyen

2010

Chemical Physics Letters

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“…The reactivity of aromatic monoradicals, 19-21,24,25 biradicals, 26-28 and triradicals 29-31 have been studied in the gas phase. Based on these studies, the hydrogen atom abstraction ability of basic aromatic carbon-centered σ-radicals in solution may be tuned by controlling the pH of the system since protonation increases the EA and hence the reactivity of these radicals.…”

Section: Introductionmentioning

confidence: 99%

Direct Comparison of Solution and Gas-Phase Reactions of the Three Distonic Isomers of the Pyridine Radical Cation with Methanol

et al. 2012

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In order to directly compare the reactivity of positively charged carbon-centered aromatic σ-radicals toward methanol in solution and in the gas phase, the 2-, 3-, and 4-dehydropyridinium cations (distonic isomers of the pyridine radical cation) were generated by ultraviolet photolysis of the corresponding iodo-precursors in a mixture of water and methanol at varying pH. The reaction mixtures were analyzed by using liquid chromatography/mass spectrometry. Hydrogen atom abstraction was the only reaction observed for the 3- and 4-dehydropyridinium cations (and –pyridines) in solution. This also was the major reaction observed earlier in the gas phase. Depending on the pH, the hydrogen atom can be abstracted from different molecules (i.e., methanol or water) and from different sites (in methanol) by the 3- and 4-dehydropyridinium cations/-pyridines in solution. In the pH range of 1 – 4, the methyl group of methanol is the main hydrogen atom donor site for both 3- and 4-dehydropyridinium cations (just like in the gas phase). At higher pH, the hydroxyl groups of water and methanol also act as hydrogen atom donors. This finding is rationalized by a greater abundance of the unprotonated radicals that preferentially abstract hydrogen atoms from the polar hydroxyl groups. The percentage yield of hydrogen atom abstraction by these radicals was found to increase with lowering the pH in the pH range of 1.0-3.2. This pH effect is rationalized by polar effects: the lower the pH, the greater the fraction of protonated (more polar) radicals in the solution. This finding is consistent with previous results obtained in the gas phase and suggests that gas-phase studies can be used to predict solution reactivity, but only as long as the same reactive species is studied in both experiments. This was found not to be the case for the 2-iodopyridinium cation. Photolysis of this precursor in solution resulted in the formation of two major addition products, 2-hydroxy- and 2-methoxypyridinium cations, in addition to the hydrogen atom abstraction product. These addition products were not observed in the earlier gas-phase studies on 2-dehydropyridinium cation. Their observation in solution is explained by the formation of another reactive intermediate, the 2-pyridyl cation, upon photolysis of 2-iodopyridinium cation (and 2-iodopyridine). The same intermediate was observed in the gas phase but it was removed before examining the reactions of the desired radical, 2-dehydropyridinium cation (which cannot be done in solution).

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Reactivity of an Aromatic σ,σ,σ‐Triradical: The 2,4,6‐Tridehydropyridinium Cation

Cited by 28 publications

References 24 publications

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Properties and Reactivity of Gaseous Distonic Radical Ions with Aryl Radical Sites

Tuning the position of unpaired electrons and doublet–quartet gap of the 1,3,5-trimethylenebenzene triradical by nitrogen, phosphorus and arsenic substitution

Direct Comparison of Solution and Gas-Phase Reactions of the Three Distonic Isomers of the Pyridine Radical Cation with Methanol

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