- Glow Discharge Plasma Reduction of Viologen Homologues and Organic Dyes in Solid and Solvated States
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A variety of viologen homologues (1,1'-disubstituted 4.4'-dipyridinium ions) were reduced both in solid and in DMF solution by a radio-frequency gaseous plasma.Reduction occured very rapidly and quantitatively with plasma exposure and resulted in the corresponding cation radicals.These radicals were oxidized on exposure to air but reduced again with repeated plasma exposure indicating that the reduction is an one-electron process.In a similar manner organic compounds such as methylene blue and brilliant green were also reduced effectively by the plasma.From kinetic study and ESR measurements approximate electron concentrations responsible for the reduction in the plasma were estimated.
- Osada, Yoshihito,Iriyama, Yu
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- Effects of pressure on the thermal back electron transfer in a dibenzylbipyridinium salt. Solvent reorganizations and dynamic solvent effects
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Kinetic effects of pressure on a decay of a radical pair produced by UV irradiation of N,N′-dibenzyl-4,4′-bypyridinium dichloride were studied in acetonitrile (AN) and propylene carbonate (PC). Both in AN and PC, the process was accelerated by an increase in pressure indicating a considerable contraction of the solvation sphere during the activation. Furthermore, in PC, pressure-induced retardation was observed at P > 200 MPa and it was attributed to slow solvent thermal fluctuations at high pressures. Copyright
- Shihab, Mehdi S.,Kubota, Koji,Takahashi, Toru,Ohga, Yasushi,Asano, Tsutomu
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- ELECTROCHEMISTRY OF METALLOPORPHYRINS AND VIOLOGENS AT ZEOLITE Y MODIFIED ELECTRODES: EVIDENCE FOR ELECTRON TRAPPING BY MONOMOLECULAR PORPHYRIN LAYERS.
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Cyclic voltammetric data are presented for electrodes coated with zeolite Y powder containing porphyrins and viologens. Half-wave potentials for viologen cations (methylviologen, benzylviologen, or N,N prime -(1,3-propenyl)-2,2 prime -bipyridinium) do not change significantly when they are exchanged into zeolite Y, whereas the reduction potentials for cobalt and zinc tetrakis (N-methyl-4-pyridyl)porphyrins shift (relative to aqueous solution) by plus 200 mV. When a viologen cation is ion exchanged into the bulk of the zeolite, and cobalt tetrakis(N-methyl-4-pyridyl)porphyrin is adsorbed onto its outer surface in monolayer quantities, current rectification and charge trapping reactions are observed.
- Li,Wang,Persaud,Mallouk
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- Poly(Xylylviologen) Electron Transfer Mediators in Amperometric Glucose Sensors
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Water-soluble poly(o-xylylviologen dibromide) and poly(p-xylylviologen dibromide) are shown to efficiently mediate electron transfer from reduced glucose oxidase to a conventional carbon paste electrode.Because of their low oxidation potentials, glucose sensors based on glucose oxidase and these mediators can be operated in a potential range where oxidation of interfering species such as ascorbic acid and uric acid does not occur.The corresponding monomeric materials, benzylviologen bromide and dibenzylviologen dibromide cannot serve as electron transfer mediators astheir formal potentials are more negative than that of the flavin redox centers in glucose oxidase.
- Hale, P. D.,Boguslavsky, L. I.,Skotheim, T. A.,Karan, H. I.,Lan, H. L.,Okamoto, Y.
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p. 259 - 264
(2007/10/02)
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- The Importance of Hydrophobic-Hydrophilic Factors in Binding of Charged Substrates to Micelles: The Use of Extramicellar Probe Luminescence to Monitor Association of Cations to the Micelle
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The anionic metal complexes 1, RuL34-, where L = 4,4'-dicarboxy-2,2'-bipyridine, has been used as an extramicellar lumeniscent probe to monitor the binding capacity of anionic sodium dodecylsulfate micelles for the quencher Cu2+ and several organic cations.Addition of surfactant attenuates the quenching activity of the cations toward 1 in each case.For Cu2+ the binding capacity, as monitored by the quenching of the extramicellar probe, is in good agreement with those determined for Cu2+ and other divalent metal ions, using quite different methods; curvature in the quenching plot as 2+> increases is attributed to screening of the micellar charge by bound Cu2+.For MV2+ quite different behavior is observed; the Stern-Volmer type quenching plot shows two good linear portions at any surfactant concentration.The portion with low slope at low 2+> is attributed to MV2+ binding to the organized surfactant; at higher 2+> the steeper plot has a slope essentially the same as that obtained in water in the absence of micelles.The absence of curvature suggests association of several MV2+ molecules does not inhibit binding of additional quenchers until nearly all the binding sites are occupied.This finding, combined with the relatively high binding capacity in terms of cation/SDS for MV2+ compared to metal ions, suggests that MV2+ binds at different sites and that other factors control its binding.Similar results heve been obtained with other organic cations.The results are most consistent with a model whereby these bind at hydrocarbon-water interfaces and not primarily with the micelle head groups.
- Foreman, Thomas K.,Sobol, Warren M.,Whitten, David G.
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p. 5333 - 5336
(2007/10/02)
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- PHOTOCHEMICALLY INDUCED REDUCTION OF VIOLOGENS IN SOLID POLAR APROTIC POLYMER MATRICES
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Photochemically induced reversible reduction of viologens in solid polar aprotic polymer matrices proceeds much more efficiently than that in protic ones.The effects of the N-substituent and anionic part of viologens were also considerable.
- Kamogawa, Hiroyoshi,Masui, Toshiaki,Nanasawa, Masato
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p. 1145 - 1148
(2007/10/02)
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