Quenching of excited triplet sensitizers by organic peroxides

Engel, Paul S.; Woods, Treacy L.; Page, Matthew A.

doi:10.1021/j100224a004

Cited by 21 publications

(8 citation statements)

References 1 publication

(1 reference statement)

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“…Also, for comparison, O 2 degassed conditions were used; otherwise, a competing process would include dione sensitization to O 2 and formation of singlet oxygen. Our work is also part of a growing body of work, ,− examining sensitization reactions by peroxide O–O bond homolysis, where the reaction is also relevant to the more commonly studied sensitization of 3 O 2 to 1 O 2 .…”

Section: Resultsmentioning

confidence: 99%

Dark-Binding Process Relevant to Preventing Photosensitized Oxidation: Conformation-Dependent Light and Dark Mechanisms by a Dual-Functioning Diketone

et al. 2019

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Few photosensitizers function in both light and dark processes as they usually have no function when the lights are turned off. We hypothesized that light and dark mechanisms in an α-diketone will be decoupled by dihedral rotation in a conformation-dependent binding process. Successful decoupling of these two functions is now shown. Namely, anti- and syn-skewed conformations of 4,4′-dimethylbenzil promote photosensitized alkoxy radical production, whereas the syn conformation promotes a binding shutoff reaction with trimethyl phosphite. Less rotation of the diketone is better suited to the photosensitizing function since phosphite binding arises through the syn conformer of lower stability. The dual function seen here with the α-diketone is generally not available to sensitizers of limited conformational flexibility, such as porphyrins, phthalocyanines, and fullerenes.

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Section: Resultsmentioning

confidence: 99%

Dark-Binding Process Relevant to Preventing Photosensitized Oxidation: Conformation-Dependent Light and Dark Mechanisms by a Dual-Functioning Diketone

et al. 2019

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“…The light doses are also smaller than those required for obtaining the same effect with the parent drug. Indeed, hydroperoxides are known to undergo easy photosensitized homolysis through energy or electron transfer (26–28). Therefore, this hydroperoxy derivative is both more toxic and more phototoxic than the parent drug.…”

Section: Resultsmentioning

confidence: 99%

In Vitro Phototoxic Properties of Triamcinolone 16,17-acetonide and Its Main Photoproducts¶

Miolo

Ricci

Caffieri

et al. 2007

Photochemistry and Photobiology

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The phototoxicity of triamcinolone 16,17‐acetonide has been estimated through a panel of in vitro tests. The main target involved in phototoxicity induced by triamcinolone appeared to be the cell membrane. Oxygen‐independent photohemolysis was observed. A photochemical study in water and buffered solutions supported the conclusion that this is related to the action of radicals formed upon UV irradiation (in particular UV‐B) by Norrish Type‐I fragmentation of the C‐20 ketone group. Peroxy radicals were formed in the presence of oxygen and were the active species in that case. Three photoproducts, isolated from the photodegradation of the drug, were submitted to the same toxicity tests. Two of them were proved to possess toxic or phototoxic properties on erythrocytes, primarily induced by UV‐B light, and may participate in the photosensitizing activity of triamcinolone 16,17‐acetonide. Our in vitro results suggest that the drug can elicit weak photosensitizing properties in vivo.

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“…Diethyl peroxide is a convenient source of the ethoxyl radical, as it is stable enough to handle, does not thermally decompose on the timescale of NTAS experiments, and photochemically dissociates to give two ethoxyl radicals without generating any byproducts. In principle, ethoxyl radicals can be generated from diethyl peroxide by either direct irradiation or triplet-sensitized energy transfer . The former approach proved to be more useful for the present purposes because it results in simpler kinetics, as the ethoxyl radicals are effectively formed instantly on the nanosecond timescale.…”

Section: Resultsmentioning

confidence: 99%

Direct Experimental Evidence for Alkoxyl Radicals Reacting as Hydrogen Atom Donors toward Pyridines

2021

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Nanosecond transient absorption spectroscopy was used to generate ethoxyl radicals and demonstrate that they react with 2,6-lutidine and 4-phenylpyridine to give the corresponding N-hydropyridinyl radicalsproducts of a novel hydrogen atom transfer from the alkoxyl radical to the nitrogen atom of the substituted pyridines. Nanosecond kinetics show that both reactions are rapid (k ∼ 107 M–1 s–1) in acetonitrile at room temperature. Rate constants measured for reaction of the ethoxyl vs. d 5-ethoxyl radical with 2,6-lutidine and 4-phenylpyridine show that both reactions exhibit primary H/D kinetic isotope effects for the hydrogen (deuterium) atom transfer reactions.

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Quenching of excited triplet sensitizers by organic peroxides

Cited by 21 publications

References 1 publication

Dark-Binding Process Relevant to Preventing Photosensitized Oxidation: Conformation-Dependent Light and Dark Mechanisms by a Dual-Functioning Diketone

Dark-Binding Process Relevant to Preventing Photosensitized Oxidation: Conformation-Dependent Light and Dark Mechanisms by a Dual-Functioning Diketone

In Vitro Phototoxic Properties of Triamcinolone 16,17-acetonide and Its Main Photoproducts¶

Direct Experimental Evidence for Alkoxyl Radicals Reacting as Hydrogen Atom Donors toward Pyridines

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