Electron transfer versus hydrogen abstraction in photoreduction of quinones. An application of chemically induced dynamic electron polarization

1978 ◽  
Vol 100 (17) ◽  
pp. 5488-5490 ◽  
Author(s):  
S. King Wong
Keyword(s):  
Electron Transfer ◽  
Hydrogen Abstraction ◽  
Electron Polarization ◽  
Chemically Induced

Chemically Induced Dynamic Electron Polarization. IV. The Photolysis of 1,4-Naphthoquinone

1974 ◽  
Vol 52 (2) ◽  
pp. 251-256 ◽  
Author(s):  
Sau-King Wong ◽  
Douglas A. Hutchinson ◽  
Jeffrey K. S. Wan
Keyword(s):  
Acetic Acid ◽  
Hydrogen Abstraction ◽  
Electron Polarization ◽  
Semiquinone Radicals ◽  
Chemically Induced ◽  
Resonance Emission ◽  
Abstraction Reaction ◽  
Spin Resonance ◽  
Spin Polarized ◽  
Hydrogen Abstraction Reaction

Electron spin resonance emission was studied from the photochemically produced 1,4-naphthosemi-quinone radical in liquid methanol, ethanol, isopropanol, ethylene glycol, and in acetic acid in the presence of 2,6-di-tert-butylphenol. This chemically induced dynamic electron polarization is due to the optically spin polarized triplets of the parent quinone and their subsequent hydrogen abstraction reaction with retention of the polarization in the resultant semiquinone radicals. In the acetic acid–2,6-di-tert-butylphenol system, emission was observed also from the phenoxy counter radical. The magnitude of the polarization at constant microwave power was found to be temperature dependent. The comparison of the photochemical theory and the radical-pair theory is examined in the light of some of the results obtained.

Selective chemochromic and chemically-induced photochromic response of a metal–organic framework

2020 ◽  
Vol 56 (44) ◽  
pp. 5929-5932 ◽  
Author(s):  
Peng Li ◽  
Qi Sui ◽  
Meng-Yue Guo ◽  
Shuai-Liang Yang ◽  
Ran Bu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Acceptor ◽  
Photoinduced Electron Transfer ◽  
Color Change ◽  
Metal Organic Framework ◽  
Confined Space ◽  
Chemically Induced ◽  
Metal Organic ◽  
Organic Framework

The MOF provides unique confined space furnished with electron acceptor sites, and exposure to amines/alcohols causes specific and size-selective direct/UV-assisted color change owing to spontaneous/photoinduced electron transfer.

scholarly journals Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

2013 ◽  
Vol 9 ◽  
pp. 1448-1454
Author(s):  
Martin Goez ◽  
Martin Vogtherr
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Nuclear Polarization ◽  
Activation Barrier ◽  
Activation Parameters ◽  
Radical Cations ◽  
Free Energies ◽  
Time Resolved ◽  
Diethyl Sulfide ◽  
Chemically Induced

Electron transfer between the title compounds and their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation entropies provide evidence for an associative–dissociative electron exchange involving dimeric radical cations. Despite this mechanistic complication, the free energies of activation were found to be well reproduced by the Marcus theory of electron transfer, with the activation barrier still dominated by solvent reorganization.

scholarly journals Flavones’ and Flavonols’ Antiradical Structure–Activity Relationship—A Quantum Chemical Study

Antioxidants ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 461 ◽  
Author(s):  
Maciej Spiegel ◽  
Tadeusz Andruniów ◽  
Zbigniew Sroka
Keyword(s):  
Electron Transfer ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Hydrogen Abstraction ◽  
Quantum Chemical Study ◽  
Hydrogen Atom Transfer ◽  
Hydroxyl Group ◽  
Water Solvent ◽  
Intramolecular Hydrogen ◽  
Catechol Moiety

Flavonoids are known for their antiradical capacity, and this ability is strongly structure-dependent. In this research, the activity of flavones and flavonols in a water solvent was studied with the density functional theory methods. These included examination of flavonoids’ molecular and radical structures with natural bonding orbitals analysis, spin density analysis and frontier molecular orbitals theory. Calculations of determinants were performed: specific, for the three possible mechanisms of action—hydrogen atom transfer (HAT), electron transfer–proton transfer (ETPT) and sequential proton loss electron transfer (SPLET); and the unspecific—reorganization enthalpy (RE) and hydrogen abstraction enthalpy (HAE). Intramolecular hydrogen bonding, catechol moiety activity and the probability of electron density swap between rings were all established. Hydrogen bonding seems to be much more important than the conjugation effect, because some structures tends to form more intramolecular hydrogen bonds instead of being completely planar. The very first hydrogen abstraction mechanism in a water solvent is SPLET, and the most privileged abstraction site, indicated by HAE, can be associated with the C3 hydroxyl group of flavonols and C4’ hydroxyl group of flavones. For the catechol moiety, an intramolecular reorganization to an o-benzoquinone-like structure occurs, and the ETPT is favored as the second abstraction mechanism.

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