26985-31-9Relevant articles and documents
Reactivity of cation radicals generated from trivalent-phosphorus compounds in the reaction with methylviolgen: Kinetic analysis
Yasui, Shinro,Shioji, Kosei,Tsujimoto, Munekazu,Ohno, Atsuyoshi
, p. 783 - 784 (1995)
Cation radicals generated from trivalent-phosphorus compounds through single-electron transfer to methylviologen undergo ionic reactions with alcohols or thiols.A kinetic analysis of the reactions has suggested that the reaction of the trivalent-phosphorus cation radicals with alcohol possesses a tighter transition state than that with thiols.
Photoinduced Charge Accumulation and Prolonged Multielectron Storage for the Separation of Light and Dark Reaction
Schulz, Martin,Hagmeyer, Nina,Wehmeyer, Frerk,Lowe, Grace,Rosenkranz, Marco,Seidler, Bianca,Popov, Alexey,Streb, Carsten,Vos, Johannes G.,Dietzek, Benjamin
, p. 15722 - 15728 (2020)
The utilization of solar energy is restricted by the intermittent nature of solar influx. We present novel noble-metal free complexes that can be photochemically charged in the presence of sacrificial electron donors and remain stable in its charged form for over 14 h. This allows the doubly reduced Cu(I) 4H-imidazolate complex to be stored after photochemical charging and used as a reagent in dark reactions, such as the reduction of methyl viologen or oxygen. Combined UV-vis/EPR spectroelectrochemistry indicates that a two-electron reduction is induced by introducing sacrificial electron donors that facilitate proton-coupled electron transfer. Repeated photochemical reduction and chemical oxidation reveals that the complex retained a charging capacity of 72% after four cycles. We demonstrate a chemical system that can decouple photochemical processes from the day-night cycle, which has been a barrier to realizing utilization of solar energy in photochemical processes on a global scale.
Solid-phase Reactivity of Pure Methyl Viologen upon Thermolysis and Photolysis: a Vibrational and Electronic Study
Poizat, Olivier,Giannotti, Charles,Sourisseau, Claude
, p. 829 - 834 (1987)
Two reactions are induced from pure solid methyl viologen dichloride, MV2+ (CL-)2, upon heating under vacuum: warming over 50 deg C yields Cl-MV+.Cl. via an intracomplex electron-transfer process; warming to 180 deg C yields 4,4'-bipyridine and CH3Cl, probably via a second intracomplex charge-transfer process.Both these reactions are also shown to occur upon visible excitation of dehydrated MV2+(Cl-)2.In this case, the MV2+ -> MV+. reduction does not arise from direct photochemistry but rather results from thermal activation.Similar treatment of the bromide and iodide salts, MV2+(Br-)2 and MV2+(I-)2, lead only to the dealkylation products.These reactions have been investigated and followed using i.r., Raman, u.v.-visible, and e.s.r. spectroscopy and their mechanisms are discussed.
Unexpected Salt Effects on Charge Separation Yields in Phenothiazine Derivatives-Methylviologen Systems
Kawanishi, Yuji,Kitamura, Noboru,Tazuke, Shigeo
, p. 6034 - 6037 (1986)
Neutral salt effects on photoinduced electron-transfer reactions between the singlet excited state of phenothiazine derivatives (PTH) and methylviologen (MV2+) were investigated in homogeneous acetyonitrile-water (4/1 v/v) mixture.In the N-methylphenothiazine-MV2+ system, the fluorescence quenching reaction was no affected by the addition of neutral salts, whereas the yield of viologen cation radical was greatly improved when some neutral salts having hydrophobic long alkyl chains were added in the solution.The well-known micellar effect was excluded since no preaggregation was found either between salts or between salt and reactant.The increased charge separation yield in the presence of neutral salts was well explained by the suppression of the back-electron-transfer reaction within the geminate ion pair owing to changes in solvation.The effect is discussed with two different and recently developed treatments, (i) solvent fraction and (ii) solvation mode.
Photoreduction of the Paraquat Dication (1,1'-Dimethyl-4,4'-bipyridinium) by Visible Light via its Charge Transfer Complex with a Dithioanion
Deronzier, Alain
, p. 329 - 331 (1982)
Photoproduction by visible light of the mild reductant 1,1'-dimethyl-4,4'-bipyridinium (PQ.+) occurs to an appreciable extent in acetonitrile via irradiation of the charge-transfer complex of PQ2+ with a dithioanion.
The Mechanism of Electron Transfer Reaction for Xanthene Dye-Sensitized Formation of Methy Viologen Radical
Usui, Yoshiharu,Misawa, Hiroaki,Sakuragi, Hirochika,Tokumaru, Katsumi
, p. 1573 - 1578 (1987)
Sensitized reduction of methyl viologen, MV2+, occurs efficiently through electron transfer from triplet xanthene dyes to MV2+ followed by electron transfer to the resulting semioxidized dyes from a reductant like triethanolamine.Unreactive ion pair complexes between these dyes and MV2+ are formed (formation constant: 1.2E3 M-1 for Eosine Y and MV2+ in 50 percent aqueous ethanol solution).The quantum yield for the reduced methyl viologen radical depends on the concentrations of MV2+ and the amine and on the ionic strength of solution.The efficiency of electron transfer from triplet dyes to MV2+ is increased by addition of alcohol, and solvent effects on the reaction mechanism are discussed.
Electrochemical oxidation of paraquat in neutral medium
Cartaxo,Borges,Pereira,Mendon?a
, p. 1010 - 1018 (2015/08/11)
Abstract Steel, Pt and pelleted Co2FeO4 electrodes were used for the electrochemical oxidation of paraquat in aqueous solutions at room temperature. The oxide electrodes were characterized by cyclic voltammetry. Paraquat electrochemical oxidation was carried out by electrolysis at constant current and monitored by UV-vis absorbance measurements. Different anode/cathode pairs were used. After 1.5 h of electrolysis the highest removal (≈79%), was obtained with the electrode pair Pt/steel followed by Co2FeO4/Pt (≈55%), corresponding to the paraquat oxidation by a conversion mechanism. Removals of ≈64% were obtained with Co2FeO4 / Co2FeO4 after 3 h of electrolysis. Mass spectrometry analysis indicates that the main intermediate oxidation products were monopyridone and dipyridone derivatives.
Intramolecular Electron Transfer from Mn or Ligand Phenolate to Photochemically Generated RuIII in Multinuclear Ru/Mn Complexes. Laser Flash Photolysis and EPR Studies on Photosystem II Models
Burdinski, Dirk,Wieghardt, Karl,Steenken, Steen
, p. 10781 - 10787 (2007/10/03)
In a mononuclear MnIV and a trinuclear MnII complex, the ligands of which contain electron-rich phenols (coordinated to the Mn('s)) and covalently attached ruthenium(II) 2,2′-trisbipyridyl(=bpy)-type groups, intramolecular electron transfer (ET) from the phenolate ligand (in the mononuclear MnIV complex) or from a MnII (in the trinuclear MnII complex) to the photochemically (λexc= 455 nm) generated RuIII takes place with k ≥ 5 × 107 s-1, giving rise to the corresponding phenoxyl radical (complexed to MnIV) or to MnIII, respectively. Thus, in the trinuclear MnII complex, the source of the electron that reduces the photogenerated RuIII(bpy?-) moiety is a MnII, in contrast to the situation with the mononuclear MnIV complex, where the electron stems from a phenolate. The half-life of the coordinated phenoxyl-type Ru(bpy)/Mn complex (as produced in the presence of [CoIII(NH3)5Cl]2+) is of the order 0.5-1 ms. The Ru(bpy) compound containing three (phenolate-ligated) MnII atoms is the first example of a photochemically induced intramolecular ET from a multinuclear Mn cluster to an attached sensitizer , and the Ru complex containing one (phenolate-ligated) MnIV is the first case of an ET from a synthetic MnIV-coordinated phenolate to a photochemically produced oxidant (RuIII).
Formation of radical anions on the reduction of carbonyl-containing perfluoroaromatic compounds in aqueous solution: A pulse radiolysis study
Shoute, Lian C. T.,Mittal, Jai P.
, p. 14022 - 14027 (2007/10/03)
Radical anions are formed on addition of hydrated electrons to pentafluoroacetophenone (PFA) and pentafluorobenzaldehyde (PFB) in aqueous solutions. On the other hand, addition of hydrated electrons to pentafluorobenzoic acid (PFBA) leads to rapid fluoride elimination. The spectrum of the radical anion of PFA has λmax at 300 and 440 nm with absorption coefficient at 440 nm ε440 = 2100 L mol-1 cm-1. PFA?- decays with a rate constant of (7 ± 3.0) × 103 s-1. It has a pKa = 7.5 and the spectrum of the conjugate acid has λmax at 270 and 460 nm with ε460 = 900 L mol-1 cm-1. The spectrum of the radical anion of PFB has λmax at 285 and 430 nm with ε430 = 800 L mol-1 cm-1. PFB?- decays with a rate of (4 ± 2) × 103 s-1. It has a pKa = 7.2 and the spectrum of the conjugate acid has weak absorption at 330 nm. Evidence for the formation of the radical anion was obtained from intermolecular electron transfer from the radical anions of PFA and PFB top-benzoquinone (Q), methyl viologen (MV2+), and 9,10-anthraquinone-2-sulfonate (AQS-). Strong reductants derived from reduction of 2,2-bipyridine (BpyH?) and 1,10-phenanthroline (PhenH?) can reduce both PFA and PFB. From the kinetics of these electron transfer reactions the reduction potentials of PFA and PFB have been determined to be -0.86 ± 0.1 and -0.75 ± 0.1 V vs NHE at pH 9.4. Addition of OH? radical to the aromatic ring of these fluorinated compounds led to rapid HF elimination and the formation of phenoxyl radicals, and addition of H? atoms led to the formation of cyclohexadienyl radical.
Photochemical generation of radical cations from α-terthienyl and related thiophenes: Kinetic behavior and magnetic field effects on radical-ion pairs in micellar solution
Evans, Christopher H.,Scaiano
, p. 2694 - 2701 (2007/10/02)
The photochemistry of α-terthienyl (αT) and related compounds has been examined in homogeneous solution and in anionic micelles in the presence of electron acceptors. The absorption spectra of the radical cations from four thiophenic substrates have been characterized; for example, those derived from α-bithienyl (αB) and αT show absorption maxima at 420 and 530 nm, respectively. Triplet quenching by acceptors such as methyl viologen (MV2+) and tetracyanoethylene approaches diffusion control (k > 5 × 109 M-1 s-1). Quenching by oxygen, which is known to be dominated by singlet oxygen sensitization, involves electron transfer only to a minor extent; the highest efficiency, for αB, was only 6%. In micellar systems the behavior of the radical-ion pairs produced via electron transfer involves the competition of geminate and exit processes which occurs in the 10-7-10-6 s time domain. Both processes are slower in the larger micelles. Geminate processes are dramatically affected by magnetic fields. A model is proposed where the rate of geminate processes is suggested to depend upon the intramicellar reencounter frequency for the pair and the degree of singlet character in the triplet-derived radical-ion pair. The magnetic field effects observed are consistent with such a model.
