- Photosensitized Reduction of Methylviologen through the Energy Transfer from Triplet Dyes to 9-Anthracenecarboxylate Anion
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The reaction mechanism for photosensitized reduction of methylviologen, MV2+ through the triplet-triplet energy transfer from organic dyes to 9-anthracenecarboxylate, AC- was investigated.From the kinetic analysis on MV+. formation, it was estimated that both efficiencies of the energy transfer and of the electron transfer from 3AC- to MV2+ were close to unity.
- Usui, Yoshiharu,Sasaki, Yoshimi,Ishi, Yukie,Tokumaru, Katsumi
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- An Aqueous Redox-Flow Battery with High Capacity and Power: The TEMPTMA/MV System
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Redox-flow batteries (RFB) can easily store large amounts of electric energy and thereby mitigate the fluctuating output of renewable power plants. They are widely discussed as energy-storage solutions for wind and solar farms to improve the stability of the electrical grid. Most common RFB concepts are based on strongly acidic metal-salt solutions or poorly performing organics. Herein we present a battery which employs the highly soluble N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4-ammonium chloride (TEMPTMA) and the viologen derivative N,N′-dimethyl-4,4-bipyridinium dichloride (MV) in a simple and safe aqueous solution as redox-active materials. The resulting battery using these electrolyte solutions has capacities of 54 Ah L?1, giving a total energy density of 38 Wh L?1at a cell voltage of 1.4 V. With peak current densities of up to 200 mA cm?2the TEMPTMA/MV system is a suitable candidate for compact high-capacity and high-power applications.
- Janoschka, Tobias,Martin, Norbert,Hager, Martin D.,Schubert, Ulrich S.
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- Pyridinium Quenchers of Ru(bpy)32+*. Charge Effects of the Yield of Electron Transfer
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The quenching of the lumunescent state of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) by a series of pyridinium ions has been studied. 4-Acetyl-, 4-cyano-, 4-carbomethoxy-, or 4-carboxy-1-methylpyridinium, along with the well-known electron-transfer agent methyl viologen (MV2+), were employed as electron-acceptor quenchers in order to reveal the effects of charge type on the yield of photoinduced electron transfer involving the Ru(II) luminescent state as electron donor.Rates of quenching by the pyridinium ions were measured by using steady irradiation techniques and compared with expectations based on the calculated energetics of electron transfer.Electron transfer yields were obtained by measurement of the transient absorbances of photogenerated radicals (e.g., pyridinyls) using conventional flash photolysis (broad band visible excitation, pH 5, μ = 0.5).The pyridiniums were less effective electron relays for photocleavage of water in terms of the rate of hydrogen production using the Ru(II) complex as sensitizer, the selected acceptor quenchers, the sacrificial relay, EDTA, and a colloidal platinum catalyst at pH = 0.5.The reduced yield of electron transfer (and photoformation of hydrogen) for quenching by pyridinium ions was consistent with an effect of electrostatic charge in the nascent radical pair produced on electron transfer quenching of Ru(bpy)32+* by viologens/pyridiniums.The transient photobleaching of Ru(bpy)32+ by 4-carboxy-1-methylpyridinium was studied by using a Nd:YAG laser with results showing pH control of the charge type and yield of net electron transfer due to in-cage protonation of photogenerated geminate radical pairs.The electrochemical properties of the pyridinium ions were also examined by cyclic voltammetry and a Hammett correlation was made of the reduction potentials.
- Jones, Guilford,Malba, Vincent
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- Aspects of Artificial Photosynthesis. Photosensitized Electron Transfer and Charge Separation in Redox Active Surfactant Aggregates
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Photosensitized electron transfer and charge separation have been demonstrated by steady-state and nanosecond laser flash photolysis in the presence of redox active surfactant aggregates prepared from CH2=C(CH3)COO(CH2)11(C5H4N+)2CH3, Br-, I- (RMV2+).Tris(2,2'-bipyridine)ruthenium chloride (Ru(bpy)32+) has been used as a sensitizer.Forward electron transfer from excited Ru(bpy)32+ to RMV2+ aggregates has been shown to be faster than that from Ru(bpy)32+ to methylviologen (MV2+) in homogeneous solutions.Conversely, the undesirable back-reactionbetween the reduced electron acceptor RMV+. and the oxidized sensitizer Ru(bpy)33+ has been found to be considerably retarded compared to the reaction between MV+. and Ru(bpy)32+.Further, unlike MV+., RMV+. decayed by a two-step process.These results have been rationalized in terms of a mechanism which requires most of the photosensitized forward electron transfer to occur on the surface of RMV2+ aggregates.Subsequently, some of the oxidized sensitizer escapes the potential field of RMV2+ and charge recombination is retarded by electrostatic repulsion between the positively charged aggregates and Ru(bpy)33+.
- Kurihara, Kazue,Tundo, Pietro,Fendler, Janos H.
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- Photoinduced Reduction of Methylviologen by Ascorbate Using Chlorophyllin in Liposome System
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Photoinduced electron transport across bilayer lipid membrane was studied, using chlorophyllin (Chln), a water-soluble derivative of chlorophyll.Photoreduction of methylviologen (MV2+) by ascorbate was observed only in the liposome system containing ascorbate in the internal aqueous phase and MV2+ in the external aqueous phase.This suggests asymetry of bilayer lipid membrane.This reaction rate was not affected by the addition of carbonyl cyanide m-chlorophenylhydrazone in the system buffered by tris(hydroxymethyl)aminomethane (Tris), but strongly affected by N-2-hydro xyethylpiperazine-N'-2-ethanesulfonic acid.In the system buffered by Tris, a proton carried is not Chln having carboxyl groups but Tris possesing primary amine group.Replacement of the central Mg of Chln with Zn gives higher rate of MV2+ photoreduction, but when Cu was used in place of Zn, photoreduction was not observed.The central metal may affect the redox potential and the life time of exited Chln.
- Hidaka, Seiji,Matsumoto, Eizo,Toda, Fujio
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- A supramolecular switch based on three binding states of a pyrene derivate: A reversible three-state switch with only two stimuli
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A fluorescent molecule, N-methyl-pyrenemethylammonium (MPA+), can be encapsulated inside cucurbit[8]uril's (CB[8]) cavity to form a binary host-guest complex. And the binary complex can further binds methyl viologen (MV2+), yielding a ternary complex. With only two chemical stimuli, cucurbit[7]uril (CB[7]) and amantadine hydrochloride (AD), the three binding states of MPA+, unbound MPA+, the binary complex and the ternary complex, can transform reversibly and exert three different fluorescence outputs.
- Chen, Hao,Yang, Hui,Xu, Wenchao,Tan, Yebang
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- Interaction of Formate and Oxalate Ions with Radiation-Generated Radicals in Aqueous Solution. Methylviologen as a Mechanistic Probe
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The reduction of methylviologen (MV(2+)) to MV.- by species arising from the interaction of radiation-generated radicals with formate and oxalate ions in aqueous solution has been studied by using the techniques of continuous and pulse radiolysis.CO2.-, arising from the reaction of H and OH with HCO2(1-), generates MV.- rapidly (k ca. 1 x 1010 M-1 s-1 at zero ionic strength) and quantitatively; k(CO2.- + MV(2+)) decreases with increasing ionic strength, and G(MV.-) increases with increasing .The reaction of eaq- with oxalate ions produces species capable of reducing MV(2+), possibly via the intermediacy of CO2.-.The oxidation of MV.- by the radicals resulting from the reaction of OH and oxalate ions, in competition with their rapid (k = 2 x 106 s-1) conversion into CO2.-, results in a decrease of G(MV.-) with increasing radiation dose.The relevance of these observations to the use of oxalate ions as a sacrificial electron donor in photochemical model systems for energy conversion is discussed.
- Mulazzani, Quinto G.,D'Agelantonio, Mila,Venturi, Margherita,Hoffman, Morton Z.,Rodgers, Michael A. J.
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- Salt Effects on the Apparent Stability of the Cucurbit[7]uril-Methyl Viologen Inclusion Complex
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The effects of the medium ionic composition on the apparent equilibrium association constant (K) for the formation of a 1:1 inclusion complex between the guest methyl viologen (MV2+) and the host cucurbit[7]uril (CB7) were studied in aqueous solutions. The K values were found to decrease with increasing ionic strength, with more pronounced effects for solutions containing divalent Ca2+ ions than for solutions containing monovalent Na+ ions. The competing ion-dipole interactions between Ca2+ or Na+ and MV2+ ions appear to be responsible for the remarkable modulation of the K values observed in this work.
- Ong, Winston,Kaifer, Angel E.
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- Preparation of Polyviologen-modified TiO2 by Photocatalytic Polymerization of Bis(4-cyano-1-pyridinio)-p-xylene Dibromide
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Methylviologen was prepared from 4-cyano-1-methylpyridinium chloride by photocatalytic reduction using TiO2 powder.In the similar manner, insoluble polyviologen was deposited on TiO2 powder by photocatalytic polymerization of bis(4-cyano-1-pyridinio)-p-xylene dibromide.Moreover, polyviologen-polyanion complex modified TiO2 was prepared in the presence of polyanion salt.
- Saika, Tetsuyuki,Iyoda, Tomokazu,Shimidzu, Takeo
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- Photochemistry of Methyl Viologen in Aqueous and Methanolic Solutions
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The photochemistry of MV(2+)(Cl(1-))2 (methyl viologen; paraquat; 1,1'-dimethyl-4,4'-bipyridinium dichloride) has been investigated in both H2O and CH3OH.It is shown that the observed photochemistry occurs via the ground-state charge-transfer complexation with the halide counterion(s).In H2O, the radical pair MV(1+).Cl2(1-). is formed with a quantum yield of 0.2 from the dichloride complex (K2Cl=1.4 M-1) with a rate > 1E8 s -1.The MV(1+).Cl2(1-). formation and decay is pH independent (1.5 to 9), the kinetics of the disappearance being second order.When the Cl(1-) counterions are replaced by Br(1-) (K2Br= 1.8 M-1) or by I(1-) (K2I= 3.2 M-1) the quantum yield drops dramatically (0.01).By comparison with Cs(1+) it is concluded that an intracomplex heavy-atom effect is observed.In methanol, where the end product is MV(1+).Cl(1-), it is shown that the radical pair MV(1+).Cl. must be an intermediate in the formation of the initial methoxy radical and MV(1+)., the observed quantum yield of the latter being strongly dependent on the chloride concentration.Furthermore, in agreement with previous suggestions in the literature, the results indicate that a weak methyl viologen chloride-methanol complex is involved in the MV(2+)(Cl(1-))2 photochemistry in methanol.
- Ebbesen, T. W.,Ferraudi, G.
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- Correlating solution binding and ESI-MS stabilities by incorporating solvation effects in a confined cucurbit[8]uril system
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The high-throughput characterization of solution binding equilibria is essential in biomedical research such as drug design as well as in material applications of synthetic systems in which reversible binding interactions play critical roles. Although isothermal titration calorimetry (ITC) has been widely employed for describing such binding events, factors such as speed, concentration, and sample complexity would principally favor a mass spectrometry approach. Here, we show a link between ITC and electrospray ionization mass spectrometry (ESI-MS) by incorporating solvation free energies in the study of the ternary complexes of the macrocyclic host cucurbit[8]uril (CB[8]). The binding affinities of 32 aromatic reference complexes were studied by ITC and ESI-MS and combined with solvation data of the guests from an implicit solvation model (SM8) to obtain a correlation between aqueous and gas-phase measurements. The data illustrates the critical importance of solvation on the binding strength in CB[8]'s ternary complexes. Finally, this treatment enabled us to predict association constants that were in excellent agreement with measured values, including several highly insoluble guest compounds.
- Rauwald, Urs,Biedermann, Frank,Deroo, Stéphanie,Robinson, Carol V.,Scherman, Oren A.
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- Time-Resolved Optical Study on the Charge Carrier Dynamics in a TiO2/AgI Sandwich Colloid
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Preparation of a sandwich colloid involving TiO2 and AgI (hexagonal) particles in alkaline aqueous solution is described.Time-resolved optical absorption experiments are reported that involve pulsed laser excitation at 355 nm (TiO2 bandgap) and at 410 nm (AgI bandgap).Charge carrier dynamics was probed directly by transient absorption measurements in the near-infrared and by reaction with methyl viologen (MV2+).Reduction of MV2+ was observed to occur over a period of 100-200 μs.MV+ so produced reduced AgI to silver.By contrast, MV2+ reduction upon bandgap excitation of neat alkaline TiO2 colloid was complete within 1 μs.These observations signal a prolonged electron-hole separation in the case of the AgI/TiO2 sol and indicate the formation of sandwich particles.
- Fitzmaurice, Donald,Frei, Heinz,Rabani, Joseph
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- Pulse Radiolysis of Methyl Viologen in Aqueous Solutions
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Pulse radiolysis of air-free aqueous methyl viologen (MV2+) solutions was carried out at various pH.The attack of e-aq on MV2+, with k(e-aq + MV2+) = 7.5*1010 dm3 mol-1 s-1, leads to the formation of the long-lived radical cation (MV.+), which possesses two absorption maxima at 392.5 nm (ε392.5 = 4200 m2 mol-1) and 600 nm (ε600 = 1450 m2 mol-1).The H-atoms react with MV2+ at pH 1 forming two species, which have superimposed absorption bands.By means of a computer simulation they are resolved in the absorptions belonging to: (1) a protonated form of the radical cation (MV.+H+), which is produced with k(H + MV2+) = (3.5+/-0.2)*108 dm3 mol-1 s-1, has 2 absorption maxima at 390 nm (ε390 = 1700 m2 mol-1) and 595 nm (ε595 = 760 m2 mol-1) and decays by second-order kinetics with k = 3.5*109 dm3 mol-1 s-1; (2) an H-adduct (MV.2+H) on the ring carbon, which is formed with k(H + MV2+) = 2.5*108 dm3 mol-1 s-1, absorbs at 310 nm (ε310 = 900 m2 mol-1) and 470 nm (ε470 = 630 m2 mol-1) and decays by conversion into MV.+H+ in a first-order process with k = 6*103 s-1.For the equilibrium MV.+H+ MV.+ + H+ pK = 2.9+/-0.1 was determined.The presented data explain, at least partly, the instability of MV2+ when used as an electron acceptor in various devices for utilization of solar energy.
- Solar, Sonja,Solar, Wolfgang,Getoff, Nikola,Holcman, Jerzy,Sehested, Knud
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- Methylviologen Redox Reactions at Semiconductor Single Crystal Electrodes
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The mechanism of the two-step reduction of the rnethylviologen cation radical (MV2+) was studied at CdS, GaAs and InP single crystal electrodes. In aqueous solution the second step (MV+?→MV0) gives rise to layer formation \vhich is not observed in mixed ethanol/water solutions. This layer has interesting electrical properties. The reoxidation of MV0 occurs by electron injection into the conduction band of aii three semiconductors. The reoxidation of MV+? at InP is also a conduction band reaction and electroluminescence is observed with the ptype semiconductor. Electron injection from MV+dot; into the conduction band of GaAs is not observed while the kinetics of the reaction at CdS depend critically on the state of the electrode surface and on the nature of the electrolyte solution. ? VCH Verlagsgesellschaft mbH,.
- Schoenmakers,Waagenaar,Kelly
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- A preparation method of paraquat (by machine translation)
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The invention provides a preparation method of paraquat, including: S1) metal palladium compound in the presence, of formula (I) with a compound represented by the 4 - pyridine boronic acid mixed reaction, to obtain 4, 4 '- bipyridyl; S2) will be the 4, 4' - bipyridyl with chlorodifluoromethane into salt, get the paraquat; wherein X is halogen or amides. Compared with the prior art, this invention has the formula (I) with a compound represented by the 4 - pyridine boronic acid as the raw material, to palladium metal compound as a catalyst, to carry out the cross-coupling reaction to obtain 4, 4' - bipyridyl, with the methyl chloride salt to obtain the paraquat, the method the reaction conversion is high, the reaction time is short, mild reaction conditions, without the need of high-temperature high-pressure, low requirements on equipment, and does not need to carry on the anhydrous solvent processing, at the same time the method after treatment is simple, the separation of the obtained product, the production process is simplified, is suitable for mass production. (by machine translation)
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- Metal-Free Electrocatalytic Aerobic Hydroxylation of Arylboronic Acids
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Hydroxylation of arylboronic acids to aryl alcohols was realized by a scalable electrocatalytic method. The present electrochemical hydroxylation employs low-cost methyl viologen as an organic cathodic electrocatalyst and involves O2 as a green and sustainable reactant. The electrochemical kinetic studies shown here can be a powerful tool to gain rich mechanistic and kinetic information and thus an in-depth understanding of the electrocatalytic mechanism.
- Luo, Jian,Hu, Bo,Sam, Alyssa,Liu, T. Leo
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supporting information
p. 361 - 364
(2018/01/28)
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- Protein thiocarboxylate-dependent methionine biosynthesis in Wolinella succinogenes
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Thiocarboxylated proteins are important intermediates in a variety of biochemical sulfide transfer reactions. Here we identify a protein thiocarboxylate-dependent methionine biosynthetic pathway in Wolinella succinogenes. In this pathway, the carboxy terminal alanine of a novel sulfur transfer protein, HcyS-Ala, is removed in a reaction catalyzed by a metalloprotease, HcyD. HcyF, an ATP-utilizing enzyme, catalyzes the adenylation of HcyS. HcyS acyl-adenylate then undergoes nucleophilic substitution by bisulfide produced by Sir to give the HcyS thiocarboxylate. This adds to O-acetylhomoserine to give HcyS-homocysteine in a PLP-dependent reaction catalyzed by MetY. HcyD-mediated hydrolysis liberates homocysteine. A final methylation completes the biosynthesis. The biosynthetic gene cluster also encodes the enzymes involved in the conversion of sulfate to sulfide suggesting that sulfate is the sulfur source for protein thiocarboxylate formation in this system.
- Krishnamoorthy, Kalyanaraman,Begley, Tadhg P.
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experimental part
p. 379 - 386
(2011/03/16)
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- Photocatalytic reduction of nitroorganics over illuminated titanium dioxide: Electron transfer between excited-state TiO2 and nitroaromatics
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The present study investigates the steady-state photocatalytic reduction of methyl viologen and a suite of monosubstituted nitrobenzenes. Reduction was carried out in deoxygenated, illuminated aqueous slurries of titanium dioxide (Degussa P25) in the presence of a sacrificial electron donor, 2-propanol. Langmuir-Hinshelwood plots were obtained for the reduction of each compound and found to be linear, with an average correlation of 0.98 and with a standard deviation on the correlations of 0.02. The concentration independent rates for nitroaromatic reduction obtained from these plots were normalized against the rate of methyl viologen reduction and the ratio was used to solve for the rate constant of nitroaromatic reduction, assuming a bimolecular model. The assumptions behind this procedure were tested by the use of the Marcus expression. Using the reorganization energy for the reaction as the fitting variable, it was possible to fit the measured rates to the predicted rates with a reorganization energy of 138 kJ/mol.
- Ferry, John L.,Glaze, William H.
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p. 2239 - 2244
(2007/10/03)
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- The Methylviologen Radical Cation. Synthesis, Crystal Structure and ab initio Calculations of N,N'-Dimethyl-4,4'-bipyridinium Chloride Dihydrate
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The title compound has been prepared by the reduction of N,N'-dimethyl-4,4'-bipyridinium dichloride with dilithium tritelluride in dimethylformamide solution.It forms deep blue crystal needles, which were characterized by a crystal structure determination.Space group Pna21, Z = 8, 3450 observed unique reflections, R = 0.045.Lattice dimensions at -70 deg C: a = 1707.6(8), b = 2323.9(11), c = 664.6(3) pm.The N,N'-dimethyl-4,4'-bipyridinium radical cations are planar and form ion pairs in the lattice.The chloride ions together with the water molecules form an infinite network of hydrogen bridges along the crystallographic a-axis.The structural parameters of the radical cation are in excellent agreement with ab initio calculations. - Keywords: N,N'-Dimethyl-4,4'bipyridinium Chloride Dihydrate, Synthesis, Crystal Structure
- Wolkers, Hans,Stegmann, Ralf,Frenking, Gernot,Dehnicke, Kurt,Fenske, Dieter,Baum, Gerhard
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p. 1341 - 1347
(2007/10/02)
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- Evidence for the Product of the Viologen Comproportionation Reaction being Spin-paired Radical Cation Dimer
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The mechanism of the bipyridylium comproportionation reaction has been determined using the redox states of methyl viologen (MV).The reaction, hitherto presumed to follow the stoichiometry MV2+ + MVo -> 2 MV+, has been investigated using in situ electrochemical EPR and UV-VIS spectroscopy and been shown to proceed via an intermediate step forming a spin-paired radical cation dimer (MV)22+.Dimer dissociation occurs as a subsequent reaction stage.
- Monk, Paul M. S.,Fairweather, Robert D.,Ingram, Malcolm D.,Duffy, John A.
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p. 2039 - 2041
(2007/10/02)
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- Radiolytic Reductions and Oxidations in Dimethyl Sulfoxide Solutions. Solvent Effects on Reactivity of Halogen Atom Complexes
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Radiolysis of dimethyl sulfoxide (DMSO) solutions containing various additives was used to achieve clean one-electron reduction or oxidation of solutes.Pulse radiolysis of benzoquinone in DMSO solutions containing acetone and triethylamine permitted conversion of all primary radicals into reducing species.The total yield of reduction in the γ-radiolysis of methyl viologen solutions was found to be 0.37 μmol/J.In the pulse radiolysis of TMPD and triphenylamine in aerated DMSO containing LiCl and/or CCl4, all the primary radicals were converted into oxidizing species and gave a maximum yield of 0.39 μmol/J.In the latter systems, oxidation was partly by halogen atom complexes.The reactivity of complexes of DMSO (DMSO*Cl, DMSO*Br) and of halide ions (Br2.1-, I2.1-) was examined for several organic compounds.DMSO*Cl oxidizes chlorpromazine, triphenylamine, and zinc porphyrin with rate constants of the order of 1E7-1E8 M-1 s-1, and the rates increase upon addition of CH2Cl2 as well as upon addition of water and formamide.DMSO*Cl also reacts with olefins by addition of Cl to the double bond; the rate constants increase upon increasing the electron-donating properties of the substituents on the double bond.The rate constants for oxidation of chlorpromazine by Br2.1- and I2.1- increase by more than 2 orders of magnitude upon changing the solvent from DMSO gradually to water.The change was less with acetonitrile/water mixtures, and the difference is probably due to differences in ion solvation.
- Kumar, M.,Neta, P.
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p. 3350 - 3354
(2007/10/02)
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- Solid, herbicidal bipyridinium quaternary salt compositions
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Bipyridinium quaternary salt compositions are prepared which are dry, free-flowing, wettable powders. The solid compositions are complexes of the bipyridinium salts and algin.
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- Solid, herbicidal complexes
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Low viscosity heteropolysaccharides, e.g., xanthan gum, S-194, and guar gum, are disclosed. These gums are especially useful in preparing herbicidal compositions.
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- ELECTRON TRANSFER FROM EXCITED MOLECULES OF ANTHRACENE DERIVATIVES TO METHYLVIOLOGEN. GENERATION OF THE CATION-RADICAL AND HYDROGEN
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The quantum yields of formation of the methylviologen cation-radical were measured, the effect of pH was studied, and the possibility of photogeneration of hydrogen was examined for systems with disodium 1,5- or 1,8-anthracenedisulphonate in aqueous media or 9-acetylanthracene in micellar media of sodium dodecyl sulphate, in the presence of methylviologen, triethanolamine, and colloidal platinum.
- Rehak, Viktor
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p. 1666 - 1671
(2007/10/02)
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- Coulombic Effect on Photoinduced Electron-Transfer Reactions between Phenothiazines and Viologens
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Photoinduced electron-transfer reactions between excited phenothiazine derivatives (PTH) and viologens (V) were investigated in aqueous acetonitrile at room temperature.Ionic substituents on PTH or V strongly affected the reaction kinetics, and the Coulombic effects on the reactions were interpreted by the work terms wr and wp, where r and p represent reactants and products, respectively.Fluorescence quenching reactions proceeded with the diffusion-controlled rate constants which were dependent on wr and were explained by the Debye-Smoluchowski equation.Charge separation efficiency (F) corresponding to the cage escape yield of geminate ion radical pair strongly depended on (wp - wr), which indicated that (i) the back-electron-transfer rate determined F and (ii) the Coulombic work terms decided the back-electron-transfer rate.Quantitative teatments of the present results demonstrated that Coulombic effects can be used effectively to generate highly efficient photoredox systems.
- Kawanishi, Yuji,Kitamura, Noboru,Tazuke, Shigeo
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p. 2469 - 2475
(2007/10/02)
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- A Pulse Radiolytic Study of Aqueous Solutions Containing Nitrobenzene and Methylviologen
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Solutions containing 2-propanol, nitrobenzene (NB), and methylviologen (MV2+) have been studied in wide ranges of concentrations and pHs.The two radicals NB- and MV+ are formed by the reactions of NB and MV2+, respectively, with both the hydrated electron and the 2-propanol radical.Studies were carried out at 578 nm where only the MV+ absorbs light.The decay of MV+ follows a single second-order process whose rate constant depends on , +>, and 2+>.Our findings could be explained by a fast equilibrium between the viologen and nitrobenzene redox systems followed by a slow reaction between MV+ and either NB- or its acidic form NBH.
- Nahor, Gad S.,Rabani, Joseph
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p. 5256 - 5260
(2007/10/02)
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- 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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p. 5951 - 5956
(2007/10/02)
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- Vibrational Study of the Methyl Viologen Dication MV(2+) and Radical Cation MV.(1+) in SEveral Salts and as an Intercalate in Some Layered MPS3 Compounds
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Infrared and Raman spectra (1800-200 cm-1) of methyl viologen (1,1'-dimethyl-4,4'-bipyridyl dication or MV(2+)) ( and derivatives) have been recorded for the chloride, iodide and palladate salts and for the intercalated compounds of formula M0.84PS3-(MV)0.16 (with M = Mn and Cd), FePS3-(MV)0.15 and Zn0.71PS3-(MV)0.29.Complete assignments have been proposed for all these species.The methyl viologen appears to be intercalcated in its dicationic form and is weakly interacting with the host lattice.In the ZnPS2 system the MV(2+) pyridyl rings are twisted while in MnPS3, CdPS3 and FePS3 the cation rings are coplanar and parallel to the sulphur layers.From these results, a model of packing of MV(2+) in the MPS3 host lattices has been established which accounts for the different interaction rates.Finally, the reduced product, MV.(1+), has been studied in both the chloride salt and the CdPS3 interaction compound: in the latter case the radical cation behaves as though diluted and trapped inside an inert matrix, demonstrating unexpected stability.
- Poizat, Olivier,Sourisseau, Claude,Mathey, Yves
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p. 3257 - 3274
(2007/10/02)
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- 1,2,3-Thiadiazole-3-in-5-ylidene-urea derivatives, process for making the same and compositions containing the same having growth regulating activity for plants
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1,2,3-Thiadiazole-3-in-5-ylidene-urea derivative of the formula STR1 in which R1 is hydrogen or alkyl which may be substituted in one or several places by oxygen or sulfur and wherein R2 and R3 have the meaning as given in the attached specification and wherein X is oxygen or sulfur. The compounds have properties suited for controlling the natural growth and natural development of plants and in addition have a superior defoliating property without accompanying unpleasant odors.
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- 1,2,3-Thiadiazole-2-id derivatives, process for making the same and composition containing the same having a growth regulating activity for plants
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1,2,3-Thiadiazole-2-id-derivative of the formula STR1 in which R1 is hydrogen or alkyl which may be substituted in one or several places by oxygen or sulfur and wherein R1 has the meaning as given in the attached specification and wherein X is oxygen or sulfur and B is a univalent metal atom. The compounds have properties suited for controlling the natural growth and natural development of plants and in addition have a superior defoliating property.
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- Herbicidal compositions
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A solid complex of a herbicidal bipyridylium salt in combination with urea or thiourea having the formula: Wherein X represents the bipyridylium salt, A represents urea or thiourea, n is 1, 2 or 4, and m is 0 to 4, its preparation and use are disclosed.
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