Fluorescence quenching by the stable free radical di-<i>t</i>-butylnitroxide

Green, James; Singer, Lawrence A.; Parks, Joel H.

doi:10.1063/1.1679569

Cited by 129 publications

(81 citation statements)

References 21 publications

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“…While it is not clear how the unpaired electron in the nitroxide radical could directly enhance this process, this mechanism has been suggested by other experimenters (2,5). …”

mentioning

confidence: 82%

“…A quick check for the influence of 10 mM HCO2- (5) showed about a five-fold decrease in hydroxyl radical trapping rate due to HC0 2 -comparing two 20 minute irradiations at 310 nm, one with and one without HCO2-. The presence of an additional sink, in this case formate, results in the following modification to equation (29) Figure 9.…”

Section: Kineticsmentioning

confidence: 99%

“…The mechanisms by which the excited singlet states of aromatic organic compounds are quenched by stable nitroxide radicals has been the subject of numerous studies over the last several decades (1)(2)(3)(4)(5). Much of this past work has been directed at disentangling the relative contributions of electron exchange, energy transfer and electron transfer to the quenching process (1).…”

Section: Introductionmentioning

confidence: 99%

“…The NO produced by (2) can further react with superoxide to form additional hydroxyl radical (or a species with similar reactivity), although the production of nitrate competes with this process (4)(5)(6)(7).…”

Section: Introductionmentioning

confidence: 99%

“…ICDOM* or 3 CDOM* ---direct photochemistry products (5) 1CDOM* or 3 CDOM* ----indirect photochemistry products (6) Transformations include direct photochemistry in which the individual excited CDOM molecule undergoes a chemical reaction (5) and indirect photochemistry in which some of the energy is transferred to another molecule sorbed or near the original molecule (6). Here we will focus on the indirect pathway (6).…”

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confidence: 99%

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Photophysics and photochemistry of natural waters with emphasis on radical probe development and application

Herbelin¹

1994

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The work presented here consists of a literature review and calculations to estimate the importance of photochemistry to carbon cycling in the oceans, followed by a photophysical study of a series of stable nitroxide radical probes that have been used for the quantitative detection of individual carbon-centered radicals and reducing species in natural waters. Two appendices follow. The first contains preliminary experiments utilizing one of the nitroxide probes in an investigation of hydroxyl radical production rates and steadystate concentrations in seawater. The second consists of an investigation of the singlet lifetimes of humic acids (HA), in order to aid in understanding their photochemical cycling and influence on other compounds.The impact of photochemical reactions on global oceanic carbon cycling was calculated from literature values. The results indicate that between 1 and 13% of all dissolved organic carbon in the oceans is oxidized photochemically. This is a significant flux term, much larger than that of riverine input for example.A photophysical study of nitroxide radical probes was undertaken. For all of the compounds studied, steady-state absorption and fluorescence spectra were identical to those of the parent fluorophores. A decrease in fluorescence lifetime and quantum yield of tens-to hundreds-fold was observed for the paramagnetic compounds relative to their diamagnetic counterparts. Very rapid fluorescence quenching rates (3 to 80 x 1010 s-1 ) were calculated for the fluorescamine moiety of the paramagnetic nitroxide compounds in a variety of solvents. Calculated energy minimized geometries were very similar for all compounds which implies that geometric differences are not responsible for the variations found in fluorescence lifetimes and quantum yields between compounds. Calculated Firster and Dexter overlap integrals do not support deexcitation by these mechanisms. Time-resolved absorption measurements resulted in no evidence for transient species due to either intersystem crossing to the triplet state or charge transfer. Of the mechanisms considered, direct internal conversion to the ground state, is most likely given our results.An investigation of the utility of 3-(aminomethyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy free radical (3-amp) for detection and quantification of hydroxyl radicals in natural waters found that the addition of primary probe compounds resulted in the generation of secondary carbon-centered radicals that were successfully trapped by 3-amp. Competition kinetics experiments with dimethyl sulfoxide resulted in a natural scavenger rate constant that matched previous literature results for coastal seawater. As expected, the addition of formate resulted in decreases, and the addition of nitrite in increases, in the hydroxyl radical trapping rate by this method. The resulting quantum yield values were about an order of magnitude higher than previous literature results. However, probablyI IYIIIIYYI Wilkl 4 due to the use of different latitudes at which to estimat...

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“…While it is not clear how the unpaired electron in the nitroxide radical could directly enhance this process, this mechanism has been suggested by other experimenters (2,5). …”

mentioning

confidence: 82%

Section: Kineticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Photophysics and photochemistry of natural waters with emphasis on radical probe development and application

Herbelin¹

1994

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CIDEP Effects of Intramolecular Quenching of Singlet and Triplet Excited States by Nitroxide Radicals in Oligopeptides: A Potentially Useful New Method for Investigating Peptide Secondary Structures in Solution

et al. 2000

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Two hexapeptides, each bearing one photoactive alpha-amino acid (Bin or Bpa) and one nitroxide-containing TOAC residue, have been synthesized and fully characterized. FT-IR absorption measurements indicate that a 3(10)-helical conformation is adopted by these peptides in solution. As two amino acid units separate the photoactive residue from TOAC in the peptide sequences, the two moieties face each other at a distance of about 6 A after one complete turn of the ternary helix. Irradiation by a light pulse from an excimer laser populates the excited states localized on the chromophores. An intramolecular interaction between the singlet (Bin) or triplet (Bin and Bpa) excited states and the doublet state of the TOAC nitroxide makes a spin-selective decay pathway possible, that produces transient spin polarization. In addition, in order to determine whether the intramolecular exchange interaction occurs through-bond or through-space, we have prepared linear and cyclic TOAC-Bin dipeptide units. A CIDEP study revealed that a through-space intramolecular interaction is operative. The observation of spin polarization makes the two helical hexapeptides suitable models to test the possibility of application of this novel technique to conformational studies of peptides in solution.

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Air‐Stable Organic Radicals: New‐Generation Materials for Flexible Electronics?

et al. 2020

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In the last few years, air‐stable organic radicals and radical polymers have attracted tremendous attention due to their outstanding performance in flexible electronic devices, including transistors, batteries, light‐emitting diodes, thermoelectric and photothermal conversion devices, and among many others. The main issue of radicals from laboratory studies to real‐world applications is that the number of known air‐stable radicals is very limited, and the radicals that have been used as materials are even less. Here, the known and newly developed air‐stable organic radicals are summarized, generalizing the way of observing air‐stable radicals. The special electric and photophysical properties of organic radicals and radical polymers are interpreted, which give radicals a wide scope for various of potential applications. Finally, the exciting applications of radicals that have been achieved in flexible electronic devices are summarized. The aim herein is to highlight the recent achievements in radicals in chemistry, materials science, and flexible electronics, and further bridge the gap between these three disciplines.

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Fluorescence quenching by the stable free radical di-t-butylnitroxide

Cited by 129 publications

References 21 publications

Photophysics and photochemistry of natural waters with emphasis on radical probe development and application

Photophysics and photochemistry of natural waters with emphasis on radical probe development and application

CIDEP Effects of Intramolecular Quenching of Singlet and Triplet Excited States by Nitroxide Radicals in Oligopeptides: A Potentially Useful New Method for Investigating Peptide Secondary Structures in Solution

Air‐Stable Organic Radicals: New‐Generation Materials for Flexible Electronics?

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