Bipyridinium Ions

Methyl viologen has also been used to oxidize 19 electron organometallic complexes which were generated photochemically. The reduced form of methyl viologen has been utilized in the reduction of Fe4S4 clusters to Fe4Sj. The irradiation of a pH 8 solution of [V(phen)3] and (A 500 nm) leads to 

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By introducing redox-active N-methyl-4,4/-bipyridinium ion (mbpy+) to the oxo-centered triruthenium cores, a series of triruthenium derivatives bearing two or three axially coordinated mbpy+ were prepared by Abe et al. [12, 13]. Electrochemical studies indicated that these mbpy+-containing triruthenium complexes afforded a total of seven to nine reversible or quasi-reversible redox waves in acetonitrile solutions at ambient temperature. Of these redox waves, four or five one-electron redox processes arise from RU3 -based oxidations or reductions involving five or six formal oxidation states, including... 

An intense purple-blue species forms within a few seconds when Cr +, in excess, is added to 4,4 -bipyridinium ion, bpyH. The color fades slowly over many minutes. The formation and disappearance of the intermediate, kf and respectively, are assigned to k2 and Atj respectively from considerations of the assessed spectrum of the intermediate. The reactions involved are... 

When KMnO is mixed with MnCl2,4H20 in cone. HCl followed by the addition of [Co(en)3]Cl3 at — 10"C, [Co(en)3][MnCl ],H20 is formed. Spectroscopic and magnetic properties = 4.94 BM at 293 K) have been reported. Polarized crystal spectra of MnClj" have been reported. The results indicate 2, symmetry for (bipH2)[MnCl5] (bipH2 = bipyridinium ion) and symmetry when Mn is doped into (Et N)2lnCl5. ... 

A member of the bipyridylium family of herbicides is the compound paraquat (1,1-dimethyl-4,4-bipyridinium ion as the chloride salt) (Figure 5.1). It is a very water-soluble contact herbicide that is active against a broad range of plants and is used as a defoliant on many crops. The compound binds tightly to soil particles following... 

TFPB- and iodide (I-) salts of 4,4/-bipyridinium ions showed pale yellow and orange colors, respectively, although each ion is colorless. These new absorption spectra above 350 nm in solutions were attributed to the IPCT complexes with 4,4 -bipyridinium ion as an acceptor and TFPB- or I- as a donor. It was thus demonstrated that these ion pairs made electronic interactions at the ground state partially transferring electronic charges from a donor to an acceptor. No color... 

In viologen-carboxylate mixtures, the charge transfer interaction between the bipyridinium ion and carboxylate is the dominant activating influence light of wavelength longer than can be absorbed by either oxidant or reductant is active and MV-+ is formed. Quantum yields between 0.3 and 1 were found [203] and its dependence on the pH of the solution was linked to the pH effect on the CTC concentration [204],... 

In the search for new herbicides and for information on factors which influence the herbicidal properties of bipyridinium ions, many substances have been synthesized, especially by Summers and co-workers. Structural... 

Combination of superoxide ion with the cation radical (MV+0 of methyl viologen (l,T-dimethyl-4,4 -bipyridinium ion, Paraqnat) is one of the best-documented examples of a stoichiometric 02 - radical coupling reaction. The initial addition to give an unstable diamagnetic product is assumed to be at a-carbon atoms (which possess the maximum unpaired spin density in the cation radical), followed by formation of a dioxetane-like intermediate that decomposes to a complex mixture of products (Scheme 13). This process may provide a means to explain the mechanism of Paraquat toxicity. Several other reports have proposed direct coupling of 02 - to cation radicals. ... 

Dutta and co-workers focused on the completely intrazeolitic Ru(bpy)3 + and bipyridinium ion systems [141]. Three N,N -dialkyl-2,2 -bipyridinium ions and methylviologen (4,4 -bipyridinium ion) with reduction potentials varying from —0.37 to —0.65 V (vs. NHE) were studied. For the 2,2 -bipyridinium salts (members... 

Specific examples of electron transfer studies made include a time resolved spectroscopic investigation of CT complexes of 2-naphthol with triethylamine in polar and non-polar solvents , fluorescence quenching of carbazole and indole by ethylene thiodicarbonate which forms ground state complexes , and the luminescent charge transfer complex of 4,4 -bipyridinium ion with tetrakis [3.5-bis(trifluoromethyl)phenyl]borate anion . 

Synonyms Paraquat dichloride Methyl viologen l,l -Dimethyl-4,4 -bipyridinium ion Gramoxone Chemical/Pharmaceutical/Other Class Quaternary nitrogen (bis-pyridinium) compound Chemical Structure ... 

In the past year, reviews on 1,8-naphthyridines, perimidines, polyazaphen-anthrenes, 3-azabicyclo[3.3.1]nonanes, and 1,2- and 2,1-benzothiazines have appeared. Reviews on specialist aspects of pyridine chemistry are devoted to the reactions of newly available pyridines, a,a -disubstituted pyridines, the reactions of pyridines with nucleophiles, the electrochemistry of IjT-disubstituted 4,4 -bipyridinium ions (the viologens such as paraquat), dihydropyridines, and 4-aryl-dihydropyridines (a new class of calcium antagonists). Reviews have been published on the cyclization of oximes and amides to quinolines and isoquinolines, quinoline- and isoquinoline-diones, benzo[fl ]- and benzo[c]-quinolizinium ions, azachrysene preparation, quinazolines with plant-growth-regulating and biocidal activities, quinazolines in pharmaceutical research, isotopic hydrogen exchange in... 

A suitable system for the measiuement of g(eaq ) and g(H) + g(H2) up to 200 °C comprises a deaerated solution containing 10" mol dm sodium nitrate and 5 x 10 mol dm sodium phosphite [2,3]. Steady-state radiolysis of this system produces nitrite ion and hydrogen, which are measmed at room temperature. G(N02 ) provides a measure of g(Caq ) and G(H2) is equated with g( + g(H2). Pulse radiolysis can also be used to measure g(eaq ) but a limitation is that the molar absorption coefficient, e, of the species formed has to be known at the temperature being studied since the measurable quantity is G . Deoxygenated solutions containing l,l -dimethyl-4,4 -bipyridinium ion (methyl... 

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