Time-resolved fluorescence-detected magnetic resonance and fluorescence studies of trialkylamines irradiated by pulse radiolysis in alkane solvents

Lefkowitz, Steven M.; Trifunac, A. D.

doi:10.1021/j150645a019

Cited by 37 publications

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“…In addition to the quinone radical anions 1,5-AQDS •3- and 2,6-AQDS •3- we observe at short delay times six groups of lines separated by approximately 60 MHz. This spectrum is shown in Figure a and can be assignated to the TEA radical cation. ,, The simulated spectrum in Figure a was calculated with hfs coupling constants determined from ESR 26 and FDMR 25 measurements in the solid phase. In order to confirm this interpretation, the experiment was repeated with 15 N-substituted TEA, and the result is shown in Figure b.…”

Section: Resultsmentioning

confidence: 99%

Investigation of the Photoreduction of Anthraquinonedisulfonic Acid by Triethylamine with Fourier Transform Electron Spin Resonance

1997

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The photoreduction of 9,10-anthraquinone-1,5-disulfonate and 9,10-anthraquinone-2,6-disulfonate with triethylamine in aqueous solution has been studied by laser photolysis using time-resolved Fourier transform electron spin resonance and optical detection in the nanosecond and microsecond time scale. With FT-ESR the semiquinone radical anions and the triethylamine radical cations could be detected at pH ) 11 in Coulombcoupled radical pairs in addition to the separated semiquinone radical anions. At pH ) 14, the R-aminoalkyl radical could be detected as the decay product of the triethylamine radical cation. From the time dependence of the spin-polarized ESR intensities of the various components the lifetime of the Coulomb-coupled radical ion pair was determined. The radical ion pair decay exhibits a two-component behavior with a fast and a slow decay time. These lifetimes depend on the pH of the solution and are on the order of 10 ns to 2 µs.

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Section: Resultsmentioning

confidence: 99%

Investigation of the Photoreduction of Anthraquinonedisulfonic Acid by Triethylamine with Fourier Transform Electron Spin Resonance

1997

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“…Some support to this idea came from fluorescence studies which failed to indicate that the mobile holes are involved in the generation of delayed fluorescence from a scintillator . The mobile holes were not observed with magnetic resonance techniques, such as fluorescence detected magnetic resonance (FDMR) .…”

Section: Introductionmentioning

confidence: 99%

High-Mobility Ions in Cyclohexane. A Transient Absorption Study

1996

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Transient absorption kinetics in radiolysis of N2O-saturated cyclohexane has been studied (0.1−100 ns; 300−800 nm). The spectra indicate the involvement of at least three cations (ions I, II, and III), only one of them having abnormally high mobility. Ion II is probably the cyclohexene radical cation, and ion III might be the dimer olefin ion. These two ions absorb as much as ion I at 450−500 nm. While ion II and ion III are scavenged by ethanol and triethylamine with a rate constant of ≈1010 mol-1 dm3 s-1, the scavenging of ion I proceeds with rate constants of ≈9 × 1010 and 2.3 × 1011 mol-1 dm3 s-1, respectively. The spectrum of ion I is similar to the spectrum of the radical cation of cyclohexane isolated in low-temperature matrices. We were not able to observe the absorption from ion I at delay times longer than 50 ns. A corresponding fast growth of the absorption from solute radical cations of pyrene and perylene was observed. The data (simulated using continuum-diffusion and Monte Carlo approaches) indicate that the scavenging constant is ≈4 × 1011 mol-1 dm3 s-1; the lifetime of the precursor of the aromatic radical cations is ≈30 ns. This short lifetime cannot be explained by a reaction with radiolytic products or by homogeneous recombination, and it seems to be incompatible with identification of the long-lived high-mobility ions observed in conductivity experiments as the radical cation of cyclohexane. A mechanism in which the mobile radical cation is in equilibrium with a normally-diffusing ion is examined in an attempt to resolve this conundrum.

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“…A similar FDMR experiment has been performed by Lefcowitz and Trifunac, who tried to observe the mobile solvent radical cation in cyclohexane. Contrary to their expectations, the growth of the signal from the solute radical cations at t d > 50 ns was not faster than diffusion-controlled . This was interpreted as an indication of the short lifetime of the mobile species.…”

Section: Resultsmentioning

confidence: 93%

“…In the latter range the FDMR decay kinetics become considerably faster, but the spectrum shape does not change. This indicates proton transfer between TEA •+ and TEA . The dependence of the rate constant of the FDMR decay on [TEA] exhibits two linear ranges (Figure b).…”

Section: Resultsmentioning

confidence: 94%

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Electron Transfer Reactions and Mobile Holes in Radiolysis of Squalane. Time-Resolved FDMR Study

and¹,

Trifunac²

1996

J. Phys. Chem.

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Fluorescence detected magnetic resonance (FDMR) is applied to study ion−molecule reactions in squalane (2,6,10,15,19,23-hexamethyltetracosane). Several time-resolved pulsed FDMR experiments are suggested to measure rate constants of scavenging by aromatic solutes. These constants vary from 5 × 108 to 1.6 × 109 mol-1 dm3 s-1. The ion−molecule reactions of radical cations are somewhat slower than reactions of radical anions. The scavenging of the alkane hole is significantly faster than ion−molecule reactions of molecular cations. The mobile hole decays on a time scale of several tens of nanoseconds. These FDMR results are in accord with our recent work on transient absorption spectroscopy in radiolysis of squalane.

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Time-resolved fluorescence-detected magnetic resonance and fluorescence studies of trialkylamines irradiated by pulse radiolysis in alkane solvents

Cited by 37 publications

References 0 publications

Investigation of the Photoreduction of Anthraquinonedisulfonic Acid by Triethylamine with Fourier Transform Electron Spin Resonance

Investigation of the Photoreduction of Anthraquinonedisulfonic Acid by Triethylamine with Fourier Transform Electron Spin Resonance

High-Mobility Ions in Cyclohexane. A Transient Absorption Study

Electron Transfer Reactions and Mobile Holes in Radiolysis of Squalane. Time-Resolved FDMR Study

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