Laser flash photolysis and product studies of the photoionization of N-methylacridan in aqueous solution

Shukla, Deepak; Rege, F. De; Wan, Peter; Johnston, Linda J.

doi:10.1021/j100178a005

Cited by 17 publications

(18 citation statements)

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“…41 The radical cation then decays by deprotonation to give the long-lived diphenylaminyl radical, in agreement with earlier results for other amine radical cations. 10,29 Further, we cannot exclude the possibility that some radical is produced by direct photohomolysis, as has been observed for some other amines. 29,30,42 Under a nitrogen atmosphere (where both triplet DPA and DHC are formed) some of the short wavelength signal is also due to DHC since the decay kinetics in the long time regime (e20 µs) are the same as those at 630 nm.…”

Section: Resultsmentioning

confidence: 91%

“…25,26 Examples include the ionization of upper triplets of biphenyl, phenothiazine, promazine, N-methylacridan, and a number of aromatic ketones in polar solvents and of N,N,N′,N′-tetramethyl-p-phenylenediamine in both polar and nonpolar solvents. 10,11,13,22,23,[27][28][29][30][31][32] Although it is clear that ionization via upper excited triplet states is relatively common, previous studies have indicated that this process is solvent dependent. For example, substrates such as phenothiazine and promazine undergo ionization from their upper triplet states in acetonitrile and aqueous acetonitrile but not in alcohol solvents.…”

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confidence: 99%

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Triplet State Mechanism for Diphenylamine Photoionization

Johnston

Redmond

1997

J. Phys. Chem. A

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The photoionization of diphenylamine has been studied using both one-and two-laser flash photolysis in acetonitrile, alcohols, and aqueous solvent mixtures with the aim of elucidating the role of the triplet in the photoionization process. Excitation of triplet diphenylamine at 532 nm leads to irreversible triplet bleaching in all solvents, although the yields decrease by approximately an order of magnitude in comparing 1:1 aqueous acetonitrile to neat methanol or 2-propanol. Photoionization to yield the diphenylamine radical cation accounts for a substantial fraction of the triplet bleaching in all cases, demonstrating that biphotonic photoionization via an upper triplet is a viable mechanism. Triplet bleaching does not lead to either N-H bond cleavage or reverse intersystem crossing in aqueous acetonitrile. Plots of the radical cation yield as a function of laser power for one-laser (308 nm) excitation of diphenylamine are linear, consistent with monophotonic ionization under these conditions.

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Section: Resultsmentioning

confidence: 91%

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confidence: 99%

Triplet State Mechanism for Diphenylamine Photoionization

Johnston

Redmond

1997

J. Phys. Chem. A

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“…The mechanism of the iridium species is similar to the represented one in Scheme 15, in which triethanolamine (TEOA) being used as reducing agent. 55 Laser flash photolysis studies provided direct evidence for photoionization of this starting compound to give the radical cation through a SET process.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Subsequent deprotonation and dimerization furnished 9,9′-bis(methylacridyl) 76 as the only isolable product in 50% yield (Scheme 24). 55 Laser-flash photolysis studies provided direct evidence for photoionization of this starting compound to give the radical cation through a SET process.…”

Section: Review Synthesismentioning

confidence: 99%

Photocatalytic Homocoupling Transformations

et al. 2021

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The homocoupling reactions promoted by photocatalysts are not very abundant in the literature but compounds generated from them are very interesting. In this short review the coverage of this item will be classified as follows on the basis of the starting material nature. 1. Introduction 2. Arenes and heteroarenes 3. Alkenes 4. Alkanes 5. Alkynes 6. Aldehydes, ketones, alcohols, amines and imines 7. Carboxylic acids 8. Nitrocompounds 9. Conclusions

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“…In the presence of oxygen, the benzyl radical forms a Ph-CH 2 -OO • radical, known to react via the Bennett mechanism [23], yielding benzaldehyde as a main product. The 10-methylacridinyl radical AcrMe • may be oxidized by oxygen molecules (E red = -0.4 V [24]), regenerating the AcrMe ? substrate or alternatively forming 10-methylacridin-9(10H)-one (AcrMe=O) with the formation quantum yield of U = 0.0004, as listed in Table 1.…”

Section: Mechanismmentioning

confidence: 99%

Photoinduced electron transfer reactions in the 10-methylacridinium cation–benzyltrimethylsilane system: steady-state and flash photolysis studies

et al. 2009

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The mechanism of the photoinduced reaction of the lowest excited singlet state of the 10-methylacridinium (AcrMe ? ) cation with benzyltrimethylsilane (BTMSi) in acetonitrile has been investigated by means of steady-state and time-resolved methods. A variety of stable products was found after irradiation (365 nm) of the reaction mixture under aerobic and oxygen-free conditions. The stable products were identified and analyzed using UV-Vis spectrophotometry, high performance liquid chromatography (HPLC), and mass spectrometry (MS). Based on Stern-Volmer plots of the AcrMe ? fluorescence quenching by BTMSi (using fluorescence intensity and lifetime measurements), the rate constants were determined to be k q = 1.24 (± 0.02) 9 10 10 M -1 s -1 and k q = 1.23 (± 0.02) 9 10 10 M -1 s -1 , i.e., close to the diffusion-controlled limit in acetonitrile, indicating the dynamic quenching mechanism. The quenching process was shown to occur via an electron-transfer reaction leading to the formation of acridinyl radicals (AcrMe • ) and C 6 H 5 CH 2 Si(CH 3 ) 3•? radical cations. Based on stationary and flash photolysis experiments, a detailed mechanism of the secondary reactions is proposed and discussed. The AcrMe • radical was shown to decay by two processes. The fast decay, observed on the nanosecond timescale, was attributed to the back-electron transfer occurring within the initial radical ion pair. The slow decay on the microsecond timescale was explained by recombination reactions of radicals which escaped from the radical pair, including benzyl radicals formed via C-Si bond cleavage in the C 6 H 5 CH 2 Si(CH 3 ) 3•? radical cation.

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Laser flash photolysis and product studies of the photoionization of N-methylacridan in aqueous solution

Cited by 17 publications

References 0 publications

Triplet State Mechanism for Diphenylamine Photoionization

Triplet State Mechanism for Diphenylamine Photoionization

Photocatalytic Homocoupling Transformations

Photoinduced electron transfer reactions in the 10-methylacridinium cation–benzyltrimethylsilane system: steady-state and flash photolysis studies

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