Relative One-Electron Reduction Potentials of Carotenoid Radical Cations and the Interactions of Carotenoids with the Vitamin E Radical Cation

1998 ◽  
Vol 120 (17) ◽  
pp. 4087-4090 ◽  
Author(s):  
Ruth Edge ◽  
Edward J. Land ◽  
David McGarvey ◽  
Louise Mulroy ◽  
T. George Truscott
Keyword(s):  
Vitamin E ◽  
Radical Cation ◽  
Radical Cations ◽  
Reduction Potentials ◽  
Electron Reduction

Elektronentransfer und Ionenpaar-Bildung, 33 [1, 2]. Die Einelektronen-Reduktion von Tetraphenyl-p-benzochinon mit Alkalimetallen: ENDOR-Spektren von Kontaktionen-Paaren sowie Tripelionen in Lösung und Einkristallstrukturen der Neutralverbindung und ihres Natrium-Salzes / Electron Transfer and Ion Pair Formation, 33 [1,2]. The Single Electron Reduction of Tetraphenyl-p-benzoquinone by Alkali Metals: ENDOR Spectra of Contact Ion Pairs as well as Triple Ions in Solution and Single Crystal Structures of Both the Neutral Compound and its Sodium Salt

1994 ◽  
Vol 49 (4) ◽  
pp. 529-541 ◽  
Author(s):  
Hans Bock ◽  
Andreas John ◽  
Markus Kleine ◽  
Christian Näther ◽  
Jan W. Bats
Keyword(s):  
Single Crystal ◽  
Radical Anion ◽  
Alkali Metals ◽  
Ion Pairs ◽  
Radical Cations ◽  
Chair Conformation ◽  
Reduction Potentials ◽  
Half Wave ◽  
Electron Reduction ◽  
Contact Ion Pairs

Tetraphenyl-p-benzoquinone, according to its single crystal structure, shows some steric congestion: its quinone ring is distorted by 7° to a chair conformation, and its phenyl substituents are twisted around their CC axes between 46° and 72°. The half-wave reduction potentials of -0.57 and -1.25 V in acetonitrile confirm negligible π interaction of the phenyl substituents. Addition of alkalimetal tetraphenylborate salts lowers the second reduction potential due to contact ion formation, which can be confirmed by UV/VIS spectra recorded under aprotic conditions. Extensive ESR/ENDOR investigations prove the formation of the following species in THF solution: Tetraphenyl-p-benzosemiquinone radical anion contact ion pairs [M·⊖ Me⊕solv]' (Me⊕: Li⊕, Na⊕, Rb⊕, Cs⊕) and contact triple ion radical cations both with identical cations [M·⊖ (Me⊕solv)2]·⊕ (Me⊕: Li⊕, Na⊕, Cs⊕) and different cations [M·⊖ (Li⊕solv)(Me⊕solv)]·⊕ (Me⊕: Na⊕, Cs⊕). Addition of crown ethers can lead to external solvation of the Me⊕ counter cations, whereas cryptands form internal solvation complexes. The radical anion of 2,6-diphenyl-p-benzosemiquinone adds cations at its phenyl-free molecular half. The radical anion salt [tetraphenyl-p-benzosemiquinone·⊖ (Na⊕(tetrahydropyrane) 2)] could be crystallized and its structure determined at 200 K. In agreement with the Hirota sign rules for contact radicals in solution, the Na⊕ ion is found 62 pm above the π plane and 29° outside the axis of the CO bound, which is elongated due to one-electron reduction by 5 pm to 127 pm.

One-electron reduction potentials of dietary carotenoid radical cations in aqueous micellar environments

FEBS Letters ◽  
2001 ◽  
Vol 500 (3) ◽  
pp. 132-136 ◽  
Author(s):  
Marc Burke ◽  
Ruth Edge ◽  
Edward J. Land ◽  
David J. McGarvey ◽  
T.George Truscott
Keyword(s):  
Radical Cations ◽  
Reduction Potentials ◽  
Electron Reduction ◽  
Dietary Carotenoid

Electron n-doping of a highly electron-deficient chlorinated benzodifurandione-based oligophenylene vinylene polymer using benzyl viologen radical cations

2021 ◽  
Author(s):  
Teck Lip Dexter Tam ◽  
Albertus Denny Handoko ◽  
Ting Ting Lin ◽  
Jianwei Xu
Keyword(s):  
Radical Cation ◽  
Radical Cations ◽  
Benzyl Viologen ◽  
Electron Doping ◽  
N Doping ◽  
Polyphenylene Vinylene

Successful electron-doping of highly electron-deficient chlorinated benzodifurandione-based polyphenylene vinylene using viologen radical cation.

scholarly journals Spectral Probe for Electron Transfer and Addition Reactions of Azide Radicals with Substituted Quinoxalin-2-Ones in Aqueous Solutions

2021 ◽  
Vol 22 (2) ◽  
pp. 633
Author(s):  
Konrad Skotnicki ◽  
Slawomir Ostrowski ◽  
Jan Cz. Dobrowolski ◽  
Julio R. De la Fuente ◽  
Alvaro Cañete ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Density Functional ◽  
Reduction Potential ◽  
Biological Significance ◽  
Radical Cations ◽  
Basis Sets ◽  
Double Bonds ◽  
Reduction Potentials

The azide radical (N3●) is one of the most important one-electron oxidants used extensively in radiation chemistry studies involving molecules of biological significance. Generally, it was assumed that N3● reacts in aqueous solutions only by electron transfer. However, there were several reports indicating the possibility of N3● addition in aqueous solutions to organic compounds containing double bonds. The main purpose of this study was to find an experimental approach that allows a clear assignment of the nature of obtained products either to its one-electron oxidation or its addition products. Radiolysis of water provides a convenient source of one-electron oxidizing radicals characterized by a very broad range of reduction potentials. Two inorganic radicals (SO4●−, CO3●−) and Tl2+ ions with the reduction potentials higher, and one radical (SCN)2●− with the reduction potential slightly lower than the reduction potential of N3● were selected as dominant electron-acceptors. Transient absorption spectra formed in their reactions with a series of quinoxalin-2-one derivatives were confronted with absorption spectra formed from reactions of N3● with the same series of compounds. Cases, in which the absorption spectra formed in reactions involving N3● differ from the absorption spectra formed in the reactions involving other one-electron oxidants, strongly indicate that N3● is involved in the other reaction channel such as addition to double bonds. Moreover, it was shown that high-rate constants of reactions of N3● with quinoxalin-2-ones do not ultimately prove that they are electron transfer reactions. The optimized structures of the radical cations (7-R-3-MeQ)●+, radicals (7-R-3-MeQ)● and N3● adducts at the C2 carbon atom in pyrazine moiety and their absorption spectra are reasonably well reproduced by density functional theory quantum mechanics calculations employing the ωB97XD functional combined with the Dunning’s aug-cc-pVTZ correlation-consistent polarized basis sets augmented with diffuse functions.

scholarly journals Inhibition of plant fatty acid synthesis by nitroimidazoles

1981 ◽  
Vol 198 (1) ◽  
pp. 193-198 ◽  
Author(s):  
A V Jones ◽  
J L Harwood ◽  
M R Stratford ◽  
P K Stumpf
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
Soluble Fraction ◽  
Acid Synthesis ◽  
Long Chain Fatty Acids ◽  
Reduction Potentials ◽  
Marked Inhibition ◽  
Mechanism Of Inhibition ◽  
Pea Seeds ◽  
Electron Reduction

1. The effect of the addition of a number of nitroimidazoles was tested on fatty acid synthesis by germinating pea seeds, isolated lettuce chloroplasts and a soluble fraction from pea seeds. 2. All the compounds tested had a marked inhibition on stearate desaturation by lettuce chloroplasts and on the synthesis of very-long-chain fatty acids by pea seeds. 3. In contrast, the effect of the drugs on total fatty acid synthesis from [14C]acetate in chloroplasts was related to the compound's electron reduction potentials. 4. Of the compounds used, only metronidazole had a marked inhibition on palmitate elongation in the systems tested. 5. The mechanism of inhibition of plant fatty acid synthesis by nitroimidazoles is discussed and the possible relevance of these findings to their neurotoxicity is suggested.

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