Bipyridylium quaternary salts and related compounds. Part 6.—Pulse radiolysis studies of the reaction of paraquat radical analogues with oxygen

Farrington, John A.; Ebert, M.; Land, Edward J.

doi:10.1039/f19787400665

Cited by 80 publications

(38 citation statements)

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“…We have noticed the same trend for the same compounds (11, 12, 13) as for other bridged sub-groups of 2,2'-bipyridinium salts (14,15,16) and 1,10-phenanthroline salts (22,23,24). For n > 4, we expect that the spectra and E'/2 of each sub-group approach those of the corresponding non-bridged compounds (10,21).…”

supporting

confidence: 62%

On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Amouyal

Zidler

1982

Israel Journal of Chemistry

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Abstract. The influence of electron relay redox potential (EI/') on the electrontransfer reactions occurring in the photo-induced hydrogen generation from water has been investigated using the Ru(bipy)~+ IMV'+ IEDTA/colloidal Pt model system. Quenching rate constants k q for electron transfer quenching of Ru(bipy)~+" by a series of 2,2'-and 4,4'-bipyridinium ions and by a series of phenanthroline ions having different redox potential EI/2 have been determined by laser flash spectroscopy in deaerated aqueous solutions at pH 5. The rate constants k h of the back electron transfer following the quenching reaction have been obtained for five bipyridinium ions under the same experimental conditions. Our results show that: (I) for the same EI/" the quencher molecular structure of the two homogeneous series does not affect k q significantly; (2) for the two series, k q increases with increasing E 1/' up to a value which is close to the diffusion-controlled limit. The same correlation between k q and E'I2 is obtained for the two series. Such a correlation is satisfactorily interpreted in the frame of existing theories describing electron-transfer reactions. particularly with the Rehm-Weller treatment, provided that an intrinsic barrier .:la"(O) = 5.2 kcal. M-I is used; (3) k h is close to the diffusion-controlled limit for E 112 comprised between -0.33 and -0.65 V (vs NHE); (4) a correlation between H, production rates and EI/, is suggested, and a maximum H, production is observed for EI/' = -0.45 V (vs. NHE) corresponding to compounds 1 and 14.

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supporting

confidence: 62%

On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Amouyal

Zidler

1982

Israel Journal of Chemistry

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“…The coincidence of the rates of disappearance of the hydrated electrons and the rate of appearance of MV •+ suggests that the latter are formed via diffusive bimolecular encounters between hydrated electrons and MV 2+ . The reduction of methylviologen by hydrated electrons in aqueous solutions has been observed previously[28][29][30] and was not further investigated in this work.Double Helical Structure of DNA is Critical for the Intermolecular Reduction of Methylviologen. The interpretation of the rapid kinetic phase in the reduction of MV 2+ observed in double-stranded but not in single-stranded DNA(Figure 2)is supported by the transient absorbance spectra observed at different ∆t values and by the effects of magnesium ions on these spectra.…”

mentioning

confidence: 80%

Migration and Trapping of Photoinjected Excess Electrons in Double-Stranded B-Form DNA But Not in Single-Stranded DNA

et al. 1997

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Photoexcitation of a pyrene derivative covalently bound to double-stranded calf thymus DNA with 355 nm Nd:YAG laser pulses (fwhm ) 24 ps, 50 mJ/cm 2 /pulse) results in the efficient two-photon-induced ionization of the pyrenyl residues. By use of nanosecond transient absorption techniques, it is shown that the excess electrons injected into the DNA can reduce methylviologen cations (MV 2+ ) that are noncovalently bound to the DNA but not MV 2+ in the outer aqueous solution phase. In double-stranded DNA, this reduction of MV 2+ to MV •+ occurs via two kinetic phases, a rapid one that is complete within e7 ns and a slower one (200-300 ns) due to the diffusive reduction of MV 2+ by hydrated electrons. The appearance of the first, rapid reduction phase of MV 2+ depends on the secondary structure of the DNA, since it is observed only in the double-stranded form but not in the denatured, single-stranded form. This rapid reduction phase is entirely eliminated upon the addition of magnesium ions, which displace the positively charged MV 2+ cations from the double-stranded DNA molecules. By variation of the concentration of MV 2+ cations at a constant distribution of covalently bound pyrenyl residues (60 base pairs per pyrenyl residue), a mean distance of migration of excess electrons in double-stranded DNA of ca. 40 Å is estimated.

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“…It would be tempting to refer to further examples, such as the study of electron-transfer and redox properties of herbicides (Farrington et al 1978 ;Camilleri et al . the author's) own work and collaborative studies .…”

Section: Discussionmentioning

confidence: 99%

Weiss Lecture

Wardman

1989

International Journal of Radiation Biology

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The work of Weiss in the 1930s, particularly with Haber, has only recently been recognized to have implications in biology and medicine. Similarly, research in radiation chemistry and the application of the pulse radiolysis technique, for example, have implications far beyond traditional radiation chemistry. Some examples of such research are discussed against a background of categorization into 'basic', 'strategic' or 'tactical' science, rather than 'pure' and 'applied'. Examples discussed include redox properties of free radicals, which are now on a firm quantitative basis, and the identification and characterization of nitro radicals as intermediates in drug metabolism. Radical reactions often take place in multicomponent systems, and the techniques of radiation chemistry can be used to probe, for example, events occurring at interfaces in micelles. Industrial processes involving radiation are attracting investment, particularly in Japan. Radiation chemistry deserves further support to exploit its full potential, but much research using radiation chemical techniques often appears, probably more appropriately, under different labels.

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Bipyridylium quaternary salts and related compounds. Part 6.—Pulse radiolysis studies of the reaction of paraquat radical analogues with oxygen

Cited by 80 publications

References 0 publications

On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

On the Effect of Electron Relay Redox Potential on Electron Transfer Reactions in a Water Photoreduction Model System

Migration and Trapping of Photoinjected Excess Electrons in Double-Stranded B-Form DNA But Not in Single-Stranded DNA

Weiss Lecture

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