Reversible σ‐Dimerizations of Persistent Organic Radical Cations

Chen, Xiaoyu; Wang, Xingyong; Zhou, Zhiping; Li, Yi‐Zhi; Sui, Yunxia; Ma, Jing; Wang, Xinping; Power, Philip P.

doi:10.1002/ange.201207412

Cited by 11 publications

(9 citation statements)

References 56 publications

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“…[9] By using weakly coordinating anions, Wang and co-workers recently succeeded in isolating benzidine and aniline radical cations, [10] among other organic radical cations. [11] Kamada, Yamamoto, and co-workers demonstrated that bis(acridine) dimers with diradical character show much larger two-photon absorption cross-sections than closed-shell compounds with the same structural backbone and composition. [12] Monoradical cations of bis(triarylamine) compounds have been investigated as mixed-valence (MV) systems to probe basic electron-transfer processes.…”

Section: Introductionmentioning

confidence: 99%

Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution

Nie

Yao

Shao

et al. 2014

Chemistry A European J

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Monoamine 1, diamines 2-4, triamine 5, and tetraamine 6 have been synthesized by substituting dianisylamino groups at the 1-, 3-, 6-, and/or 8-positions of pyrene. Diamines 2-4 differ in the positions of the amine substituents. No pyrene-pyrene interactions are evident in the single-crystal packing of 3, 4, and 6. With increasing numbers of amine substituents, the first oxidation potential decreases progressively from the mono- to the tetraamine. These compounds show intense charge-transfer (CT) emission in CH2 Cl2 at around 530 nm with quantum yields of 48-68 %. Upon stepwise oxidation by electrolysis or chemical oxidation, these compounds were transformed into radical cations 1(⋅+) -6(⋅+) and dications 2(2+) -6(2+) , which feature strong visible and near-infrared absorptions. Time-dependent density functional theory studies suggested the presence of localized transitions from the pyrene radical cation and aminium radical cation, intervalence CT, and CT between the pyrene and amine moieties. Spectroscopic studies indicated that these radical cations and dications have good stability. Triamine 5 and tetraamine 6 formed efficient CT complexes with tetracyanoquinodimethane in solution. The results of EPR spectroscopy and density functional theory calculations suggested that the dications 2(2+) -4(2+) have a triplet ground state, whereas 5(2+) and 6(2+) have a singlet ground state. The dication of 1,3-disubstituted diamine 4 exhibits a strong EPR signal.

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Section: Introductionmentioning

confidence: 99%

Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution

Nie

Yao

Shao

et al. 2014

Chemistry A European J

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“…[19] We also took into account the possibility of the formationo fc ovalent (DMA) 2 C + and (DMA) 2 2 + ,c onsidering that the formationo fd imeric radical cations of aromatic acetylenes has been reported [25] and the covalentt ype (DMA) 2 2 + has been produced in crystals( Figure 1a). [26] Figure 2a shows the TA spectra of DMAo bserved at time delays of 50 ns to 50 msa fter pulse radiolysis. The absorption spectrum observeda tDt = 50 ns exhibits two stronga bsorption bands with the maxima located at around4 30 and 560 nm and aw eak absorption band in the near-IR region (900-1600nm).…”

Section: Resultsmentioning

confidence: 99%

“…[25] Several studies on the structure of dimeric radical ions have focusedo nt he existence of charge-localizedd imer radical ions induced by conformational flexibility in solution. [7,16,[25][26][27][28][29] For example, the major structure of the benzene dimer radical cation hasl ong been debated. [7,[30][31][32][33][34][35] Although as lipped faceto-face configurationh as been accepted as the dominant species characterized by ac harge resonance band in solution and gas phases, other tilted face-to-face dimers, and T-shaped dimer radicalc ations with charge localization have also been discussed as possible conformations.…”

Section: Introductionmentioning

confidence: 99%

“…[28,39] Recently,C hen et al have shown that radical cations of 2-ethyl-9,10-dimethoxyanthracene( DMAC + )e xist dominantly as monomers in solution, whereas dimerization of the radicalc ations occurs upon crystallization. [26] In the present study,w ec onducted transienta bsorption( TA)a nd time-resolved resonance Raman( TR 3 )s pectroscopic measurements using pulser adiolysis of DMA dissolved in 1,2-dichloroethane (DCE). Pulse radiolysis, whichc an easily and selectively generate radicali ons, is highly effective in investigating the changes induced by additional charges in the solution.…”

Section: Introductionmentioning

confidence: 99%

“…Pulse radiolysis, whichc an easily and selectively generate radicali ons, is highly effective in investigating the changes induced by additional charges in the solution. [5,7,16,[23][24][25][26][27][28] The results obtained from the TA and TR 3 experiments and density functional theory (DFT) calculations indicate the charge-localized DMA dimer radical cation, (DMA) 2 C + ,e xists in solution.…”

Section: Introductionmentioning

confidence: 99%

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Formation of the Charge‐Localized Dimer Radical Cation of 2‐Ethyl‐9,10‐dimethoxyanthracene in Solution Phase

Choi

Ahn

Fujitsuka

et al. 2019

Chemistry A European J

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Although dimer radicali ons of aromatic molecules in the liquid-solution phase have been intensely studied, the understanding of charge-localized dimers, in which the extra charge is localized in as ingle monomer unit insteado f being shared between two monomer units,i ss till elusive. In this study,t he formation of ac harge-localized dimer radical cation of 2-ethyl-9,10-dimethoxyanthracene( DMA), (DMA) 2 C + is investigated by transient absorption (TA) and time-resolved resonance Raman( TR 3 )s pectroscopic methodsc ombined with ap ulse radiolysis technique. Visible-and near-IR TA signals in highly concentrated DMA solutionss upported the formation of non-covalent( DMA) 2 C + by association of DMA and DMAC + .T R 3 spectra obtainedf rom 30 ns to 300 ms time delays showedt hat the major bands are quite similar to those of DMA except for small transient bands, even at 30 ns time delay,s uggesting that the positivec hargeo fnoncovalent( DMA) 2 C + is localized in as inglem onomer unit. From DFT calculationsf or (DMA) 2 C + ,o ur TR 3 spectra showed the best agreement with the calculated Raman spectrum of charge-localized edge-to-faceT -shaped (DMA) 2 C + ,t ermed DTC + ,a lthought he charge-delocalizeda symmetric p-stacked face-to-face (DMA) 2 C + ,t ermedD F3C + ,i st he most stable structure of (DMA) 2 C + according to the energetics from DFT calculations. The calculated potentiale nergy curves for the association between DMAC + and DMA showed that DTC + is likely to be efficientlyf ormed and contributes ignificantly to the TR 3 spectra as ar esult of the permanent charge-induced Coulombic interactions and ad ynamic equilibrium between chargel ocalized and delocalized structures.

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Tuning Ground States of Bis(triarylamine) Dications: From a Closed‐Shell Singlet to a Diradicaloid with an Excited Triplet State

Wang

Zheng

et al. 2014

Angewandte Chemie

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Three bis(triarylamine) dications were isolated by using weakly coordinating anions. Their electronic structures in the ground state were investigated by various experiments in conjunction with theoretical calculations. The ground-state electronic structures of these species were tunable by substituent effects, with two of them as closed-shell singlets and one of them as an open-shell singlet in the solid state. The excited state of the latter is thermally accessible, indicated by EPR and SQUID measurements. The work provides a new and stable diradicaloid structure motif with an excited triplet sate.

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Reversible σ‐Dimerizations of Persistent Organic Radical Cations

Cited by 11 publications

References 56 publications

Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution

Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution

Formation of the Charge‐Localized Dimer Radical Cation of 2‐Ethyl‐9,10‐dimethoxyanthracene in Solution Phase

Tuning Ground States of Bis(triarylamine) Dications: From a Closed‐Shell Singlet to a Diradicaloid with an Excited Triplet State

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