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V. B. Vol'eva A. I. Prokofev A. Yu. Karmilov N. L. Komissarova I. S. Belostotskaya T. I. Prokofeva V. V. Ershov 《Russian Chemical Bulletin》1998,47(10):1920-1923
The formation of semiquinone and phenoxazyl radicals and metallocomplexes with semiquinone ligands was observed by ESR during
the interaction of di-tert-butylpyrocatechol with Al2O3, ZnO, SiO2, and TiO2. In the case of different modifications of SiO2, admixtures of TiO2 exhibit a higher reactivity in complex formation with the organic substrate.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1975–1978, October, 1998. 相似文献
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本文研究了竹红菌甲素和还原型谷胱甘肽(GluSH)间的光诱导氧化还原作用。甲素是3,10-二羟基-4,10-苝醌衍生物。在GluSH作为电子给体时,甲素经受可见光诱导的单电子还原,生成年醌自由基或二氢甲素,取决于pH值,同时GluSH被氧化。甲素的单电子还原量子效率随pH值增加而增加。在充氧溶液中甲素敏化氧化GluSH的反应通过类型Ⅰ和Ⅱ的混合机制进行。用ESR检测到了通过Fenton反应产生的羟基自由基。在脂质体包裹的甲素溶液中用动力学测定方法证明了甲素敏化GluSH的氧化是通过类型Ⅱ机制进行的。 相似文献
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《Journal of Coordination Chemistry》2012,65(1-3):77-84
Abstract Hydroxyanthraquinones, model compounds for anthracycline antibiotics, are reduced by Fe(II)-ADP and Fe(II)-phosphate complexes to produce semiquinone radicals. In case the corresponding hydroquinone is stable, two electron reduction is caused by the Fe(II)-phosphate complex, rather strong reducing agent. 相似文献
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Joseph C. Sloop Tashni Coote Benjamin Shepler Ubie Sullivan Jeff W. Kampf Paul D. Boyle 《Journal of Physical Organic Chemistry》2012,25(4):314-321
The design of novel, functionalized bis‐metaphenylene semiquinone (SQ) ligands and their corresponding metal complexes which combine conformational flexibility and electron‐withdrawing, electron‐donating, and conjugating substituents enable investigation of multiple structure–property relationships. Along these lines, we report the synthesis of three new bis(ZnII(SQ)TpCum,Me) complexes containing the bis‐metaphenylene coupling fragment. Using electron paramagnetic resonance spectroscopy, ab initio computations and superconducting quantum interference device magnetometry, we show how spin‐density is affected by the bis‐metaphenylene system substituents. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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A. S. Tatikolov 《Russian Chemical Bulletin》1997,46(6):1082-1088
Kinetics of the interaction of ketyl and neutral semiquinone radicals with dioxygen was studied by the flash photolysis technique.
The reactivity of neutral semiquinone radicals in the transfer of a hydrogen atom to O2 is lower than that of ketyl radicals and increases as the reduction ability of the radicals increases, which give evidence
for the charge transfer from the radicals to O2 in the transition state of the reaction. The deuterium kinetic isotope effect of the reaction (up to 2.6) suggests considerable
weakening of the O−H bond of the seminquinone radical in the transition state. A cyclic structure of the transition state
similar to that in the reactions of ketyl radicals with hydrogen atom acceptors is proposed. In aprotic volvents, solvation
has essentially no effect on the reactivity of neutral anthrasemiquinone radicals up to solvent nucleophilicityB≈240. In solvents with higher nucleophilicity and in protic solvents, their reactivity drops sharply. Hydrogen atom transfer
reactions involving ketyl and neutral semiquinone radicals are shown to involve concerted electron and proton transfers, and
to have transition states in which the partial transfer of an electron and a proton from the ketyl or semiquinone radical
to an acceptor occurs.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1131–1137, June, 1997. 相似文献
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Experimental rate constants of the reactions of semiquinone radicals with hydroquinones in chlorobenzene at ∼300 K are by
almost an order of magnitude higher than the rate constants of the reactions of phenoxyl radicals with phenols, which are
equivalent to the former ones by heat effects. To reveal differences in the rate constants of these groups of reactions, we
performed quantum chemical calculations of the energy profiles of the reactions and dissociation energies by the B3LYP density
functional theory using the GAMESS and GAUSSIAN-03 programs in the 6-31+G* basis set. The solvation energies were calculated in all stationary points on the reaction coordinate by the method of polarized
continuum model. In terms of the intersecting parabolas method, the reactions of semiquinone radicals with hydroquinones and
phenoxyl radicals with phenols can be attributed to the same class of reactions only in the gas phase. In solvents this class
of reactions is divided into two subclasses due to differences in solvation energies of the preliminary complexes and transition
states of these reactions.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1495–1501, September, 2006. 相似文献
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We have used EPR to study oak bark, bulb onion peel, and their aqueous extracts. We have established that their paramagnetic
properties are determined by at least four types of paramagnetic centers: semiquinone radicals, Fe3+ ions, and two types of Mn2+ ions. We have observed that metal ions are extracted by water from the plant raw material without any change in their original
coordination environment. The aqueous extracts were subjected to oxidative processes: mild oxidation in the dried state, strong
oxidation when stored as solutions. We have shown that when the solutions are stored, the oxidation reaction is catalyzed
by the metal ions and is accompanied by formation of semiquinone radicals.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 440–445, May–June, 2009. 相似文献
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Dr. Víctor García-López Dr. Michal Zalibera Dr. Nils Trapp Dr. Martin Kuss-Petermann Prof. Dr. Oliver S. Wenger Prof. Dr. François Diederich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11451-11461
Resorcin[4]arene cavitands, equipped with diverse quinone ( Q ) and [Ru(bpy)2dppz]2+ (bpy=2,2′-bipyridine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine) photosensitizing walls in different configurations, were synthesized. Upon visible-light irradiation at 420 nm, electron transfer from the [Ru(bpy)2dppz]2+ to the Q generates the semiquinone ( SQ ) radical anion, triggering a large conformational switching from a flat kite to a vase with a cavity for the encapsulation of small guests, such as cyclohexane and heteroalicyclic derivatives, in CD3CN. Depending on the molecular design, the SQ radical anion can live for several minutes (≈10 min) and the vase can be generated in a secondary process without need for addition of a sacrificial electron donor to accumulate the SQ state. Switching can also be triggered by other stimuli, such as changes in solvent, host–guest complexation, and chemical and electrochemical processes. This comprehensive investigation benefits the development of stimuli-responsive nanodevices, such as light-activated molecular grippers. 相似文献