Electron and organic radical anion solvation. Pulse radiolysis of tetrahydrofuran and its solutions of N-methylacetamide or pyrrolidone

Tran‐Thi, T.‐H.; Koulkès-Pujo, A. M.

doi:10.1021/j100230a014

Cited by 29 publications

(29 citation statements)

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“…A persistent ESA is observed at negative delay times (blue), and it is also observed in neat THF (gray) at both positive and negative delay times (Figure S7). The increasing intensity of this ESA band at longer probe wavelengths is consistent with previously reported spectra of ionized THF generated by pulse radiolysis, 39,40 and thus we assign it to the long-lived species produced by multiphoton ionization of the solvent 41 (i.e., solvent radical cations and solvated electrons). A much stronger ESA band consistent with the Cu(II)* state, however, appears between 450 and 650 nm at positive times, growing in amplitude and shifting toward shorter wavelengths over the first several picoseconds until reaching a maximum amplitude at ∼10 ps.…”

Section: ■ Results and Discussionsupporting

confidence: 91%

Mechanisms of the Cu(I)-Catalyzed Intermolecular Photocycloaddition Reaction Revealed by Optical and X-ray Transient Absorption Spectroscopies

et al. 2021

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The [2 + 2] photocycloaddition provides a simple, single-step route to cyclobutane moieties that would otherwise be disfavored or impossible due to ring strain and/or steric interactions. We have used a combination of optical and X-ray transient absorption spectroscopies to elucidate the mechanism of the Cu(I)-catalyzed intermolecular photocycloaddition reaction using norbornene and cyclohexene as model substrates. We find that for norbornene the reaction proceeds through an initial metal-to-ligand charge transfer (MLCT) state that persists for 18 ns before the metal returns to the monovalent oxidation state. The Cu K-edge spectrum continues to evolve until ∼5 μs and then remains unchanged for the 50 μs duration of the measurement, reflecting product formation and ligand dissociation. We hypothesize that the MLCT transition and reverse electron transfer serve to sensitize the triplet excited state of one of the norbornene ligands, which then dimerizes with the other to give the product. For the case of cyclohexene, however, we do not observe a charge transfer state following photoexcitation and instead find evidence for an increase in the metal−ligand bond strength that persists for several ns before product formation occurs. This is consistent with a mechanism in which ligand photoisomerization is the initial step, which was first proposed by Salomon and Kochi in 1974 to explain the stereoselectivity of the reaction. Our investigation reveals how this photocatalytic reaction may be directed along strikingly disparate trajectories by only very minor changes to the structure of the substrate.

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Section: ■ Results and Discussionsupporting

confidence: 91%

Mechanisms of the Cu(I)-Catalyzed Intermolecular Photocycloaddition Reaction Revealed by Optical and X-ray Transient Absorption Spectroscopies

et al. 2021

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“…In reaction , electron pulses with a pulse width <50 ps ionized THF (RH) to produce solvated electrons, which react with Na + to form (Na + , e s – ) pairs . A proton transfer occurs from a radical solvent molecule (RH •+ ) to an adjacent solvent molecule (RH) as described in reaction . (Na + , e s – ) reacts with the polymers (P) to inject an electron to make polymer radical anions (P • ) in reaction . RH → RH • + + normale normals − RH • + + RH → RH 2 + + normalR Na + + normale normals − → ( Na + , e s − ) normalP + ( Na + , e s − ) → normalP • − + Na + …”

Section: Experimental Methodsmentioning

confidence: 99%

Polarons, Compressed Polarons, and Bipolarons in Conjugated Polymers

et al. 2013

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Extensive reductive chemical doping in four conjugated polymers showed evolution of optical spectra for negative polarons and more reduced species. Delocalization lengths of the polarons, which ranged from 2 to 6 nm, were determined from measurements of bleaching of the neutrals, with the extinction coefficients measured by pulse radiolysis. A particular advantage of reductive doping is the ability to encapsulate the Na + counterions in the C 222 cryptand to control the interaction of charges with counterions. For lightly doped chains C 222 had little effect on the delocalization lengths or spectra of the two polaron transitions P 1 and P 2 , perhaps because most were completely dissociated to free ions. C 222 did strongly alter the spectra when many electrons were added to a chain. For the shortest polarons, 2 nm in poly(phenylene-vinylene) (PPV), energies of the P 1 and P 2 transitions increased with the extent of reduction. The effect on the P 1 transition was greater in the absence of C 222 indicating ion-pairing equilibria for the short PPV polarons. Highly reduced ions formed upon injection of multiple electrons included polarons compressed by factors of four or more from their normal lengths to ∼1 charge/nm: a highly reduced 60 nm long chain contained ∼60 electrons. For compressed polarons the transitions shifted with increasing reduction indicating sensitivity to counterions: ion pairing is an important determinant of the behavior upon multiple reductions.

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“…Solute radical anions are also produced by pulse radiolysis in tetrahydrofuran (THF). The reactions yielding the radical anion are summarized in the following equations 50 , 51 : …”

Section: Resultsmentioning

confidence: 99%

Formation of intramolecular dimer radical ions of diphenyl sulfones

Okamoto

Kawai

Kozawa

2020

Sci Rep

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Dimer radical ions of aromatic molecules in which excess charge is localized in a pair of rings have been extensively investigated. While dimer radical cations of aromatics have been previously produced in the condensed phase, the number of molecules that form dimer anions is very limited. In this study, we report the formation of intramolecular dimer radical ions (cations and anions) of diphenyl sulfone derivatives (DPs) by electron beam pulse radiolysis in the liquid phase at room temperature. The density functional theory (DFT) calculations also showed the formation of the dimer radical ions. The torsion barrier of the phenyl ring of DPs was also calculated. It was found that the dimer radical ions show the larger barrier than the neutral state. Finally, stability of the dimer radical anion is dependent on not only the inductive effect of the sulfonyl group but the conjugation involving the d-orbital of the S atom and the phenyl rings.

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Electron and organic radical anion solvation. Pulse radiolysis of tetrahydrofuran and its solutions of N-methylacetamide or pyrrolidone

Cited by 29 publications

References 0 publications

Mechanisms of the Cu(I)-Catalyzed Intermolecular Photocycloaddition Reaction Revealed by Optical and X-ray Transient Absorption Spectroscopies

Mechanisms of the Cu(I)-Catalyzed Intermolecular Photocycloaddition Reaction Revealed by Optical and X-ray Transient Absorption Spectroscopies

Polarons, Compressed Polarons, and Bipolarons in Conjugated Polymers

Formation of intramolecular dimer radical ions of diphenyl sulfones

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