Spin statistical factor in the reactions of excess electron scavenging by stable nitroxyl radicals

Borovkov, V. I.; Matveeva, A. G.; Ivanishko, I. S.; Beregovaya, I. V.; Резников, В. А.

doi:10.1134/s0012501611090065

Cited by 3 publications

(3 citation statements)

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“…The reason of 4-fold more effective scavenging by the TEMPON radical is its spin independence since the formation of the triplet state of anion diradical is energetically allowed. 14 We emphasize that if the electron transfer to nitroxide radicals in our experimental conditions occurs then the typical electron−radical distance is about 1.5 nm, but for TEMPO, only one-quarter of the encounters results in the scavenging due to spin statistical factor 1/4. Figure 2c shows the TR MFE curves, rising parts of which are determined primarily by the rates of the singlet−triplet mixing between the nearly degenerate singlet and triplet states of the radical pairs driven by hyperfine couplings (HFC) in the TMPD +• radical cation and its precursors, as well as by phase relaxation as schematically illustrated in Figure 1.…”

Section: ■ Resultsmentioning

confidence: 79%

“…Note that the addition of TEMPON or 1,2-dibromoethane at a concentration of 0.03 mM leads to virtually the same effect as does the addition of TEMPO at four times greater concentration. The reason of 4-fold more effective scavenging by the TEMPON radical is its spin independence since the formation of the triplet state of anion diradical is energetically allowed . We emphasize that if the electron transfer to nitroxide radicals in our experimental conditions occurs then the typical electron–radical distance is about 1.5 nm, but for TEMPO, only one-quarter of the encounters results in the scavenging due to spin statistical factor 1/4.…”

Section: Resultsmentioning

confidence: 82%

“…In order to minimize the spin exchange contribution to spin transitions in the SCRPs, we have studied long-distance electron transfer to 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) as well as to 2,2,3,4,5,5-hexamethylimidazolidin-1-oxyl (HMI) in n-dodecane. As our previous studies showed, 14,15 reaction 2 proceeds in these cases only if the spin state of e − /R • encounter pair is singlet, with the typical reaction distances of about 1.5 nm. Rates of all the processes involved, i.e., recombination of the SCRPs, spin evolution of SCRPs, and the reaction of excess electrons scavenging, have been monitored using recombination fluorescence decays from the irradiated TMPD solutions.…”

Section: ■ Introductionmentioning

confidence: 74%

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Spin-Selective Reaction with a Third Radical Destroys Spin Correlation in the Surviving Radical Pairs

et al. 2013

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The goal of this work is to reveal the effect that an irreversible spin-selective reaction of a partner of the spin-correlated radical pair (SCRP) with a third paramagnetic particle has on the spin state of the surviving SCRPs in the absence of spin exchange interaction. As studied SCRPs, we used the geminate (excess electron/radical cation) pairs generated by ionizing irradiation of tetramethyl-para-phenylenediamine solutions in n-dodecane. As a spin-selective reaction, the scavenging of electrons by nitroxide radicals from the bulk of the solution was used. Both the electron scavenging reaction and the spin correlation in the surviving SCRPs were monitored by measuring the recombination fluorescence decays of the irradiated solutions under the same experimental conditions. It was found that the spin-selective electron scavenging results in the acceleration of spin correlation decay in the remaining unreacted SCRPs. In accordance with the suggested theoretical model, the rate of this additional spin correlation decay is revealed to be equal to the scavenging rate.