Dimethyl sulfoxide , redox

Fig. 15. EPR spectra of the Rieske cluster in membranes of Paracoccus denitrificans in different redox states of the quinone pool and with inhibitors added. Q x, ascorbate reduced Qred) reduced with trimethylhydroquinone dissolved in dimethyl sulfoxide +EtOH, reduced with trimethylhydroquinone dissolved in 90% ethanol +Myxo, ascorbate reduced with myxothiazol added + Stigma, ascorbate reduced with stigmatellin added. Only the gy and signals are shown. The dotted line has been drawn at...

The redox characteristics, using linear sweep and cyclic voltammetry, of a series of (Z)-6-arylidene-2-phenyl-2,3-dihydrothiazolo[2,3-r][l,2,4]triazol-5(6//)-ones 155 (Figure 24) have been investigated in different dry solvents (acetonitrile, 1,2-dichloroethane, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO)) at platinum and gold electrodes. It was concluded that these compounds lose one electron forming the radical cation, which loses a proton to form the radical. The radical dimerizes to yield the bis-compound which is still electroactive and undergoes further oxidation in one irreversible two-electron process to form the diradical dication on the newly formed C-C bond <2001MI3>. 

The cells are permitted to "plant" to the ECM and adjust to the incubator temperature (37°C) and C02 concentration. Then test compounds or controls (both in 0.1% dimethyl sulfoxide, DMSO) are added to the test wells. The cells are then incubated overnight, and the indicator dye Alamar blue10 is added. This noncytotoxic dye reacts to mitochondrial redox reactions and is measured fluorometrically. Cell metabolic activity is determined starting at 3 h after the dye is added and daily thereafter. 

A values have been obtained for oxidation of benzenediols by [Fe(bipy)(CN)4], including the effect of pH, i.e., of protonation of the iron(III) complex, and the kinetics of [Fe(phen)(CN)4] oxidation of catechol and of 4-butylcatechol reported. Redox potentials of [Fe(bipy)2(CFQ7] and of [Fe(bipy)(CN)4] are available. The self-exchange rate constant for [Fe(phen)2(CN)2] has been estimated from kinetic data for electron transfer reactions involving, inter alios, catechol and hydroquinone as 2.8 2.5 x 10 dm moF s (in dimethyl sulfoxide). 

In addition, the reduction of a-11 and (3-11 was s tudied in dimethyl sulfoxide as solvent, in the presence of pyridiniump-toluensulfonate. This medium makes mutarota-tion slower than the redox process.73 The two anomeric forms could reduce Cr(VI) and Cr(V) by formation of a Cr(VI) and Cr(V) ester intermediate. The equilibrium constant for this step and the rate of the redox step were different for each anomer for a-11, the equilibrium constant for ester formation is higher than for (3-11, but the redox process within this complex is faster for the latter anomer. These differences can be explained by the better chelating capacity of the 1,2-cri-diol moiety of a-11. Room-temperature CW-EPR spectra of these mixtures revealed for the a anomer several five-coordinated Cr(V)-bischelates (giso= 1.9820 [crilso 15.9xl(r4cm 1 (=47.7MHz)],... 

The electroactivity of a redox polymer may depend upon the solvent with which the surface modified electrode is in contact. Thus, for example, PVP containing an EDTA complex of ruthenium(III) is electroactive in contact with aqueous media, but inactive in contact with solvents such as dimethyl sulfoxide. 

The redox potentials for several quionones (Q 3,5-di-tert-butyl-o-quinone, o-benzoquinone, p-benzoquinone, and tetrafluoro-o-benzoquinone), their semi-quinone anion radicals (SQ- -) and their fully reduced forms [catechols (H2Cat) and catechol anions (HCat-)] in four aprotic solvents [acetronitrile (AN), di-methylformamide (DMF), dimethylacetaminde (DMA), and dimethyl sulfoxide (Me O)] are summarized in Table 12.2.12... 

More interesting because of earlier work on the reduction of 02 at macrocycles is the reduction of 02 in dimethyl sulfoxide using a redox couple involving anthraqui-none mixed into various complex polymers that are attached to the underlying metal or graphite. The diffusion of 02 into the film turns out to be relatively fast, as... 

The redox properties of tetraphenylporphyrin have been studied in dimethyl sulfoxide (DMSO) and more polar water/DMSO mixtures. Increasing solvent polarity [i.e. inereasing water content) shifts the reduction potentials to more positive values and makes the reduetion step more favourable, since a better solvated anion is formed from a neutral speeies [291]. 

The most widely studied examples are cyclooctatetraene (COT,I) and its derivatives. In such conventional aprotic solvents as DMF, dimethyl sulfoxide (DMSO), or acetonitrile containing tetraalkylammonium salts, two distinct one-electron reduction waves are observed at approximately —1.64 V and —1.80 V versus SCE, with AE separations varying from —130 V to —240 mV [43,53-56]. In THF and NH3, this separation reduces further [57-59], and in the presence of all alkali salts [60,61] even two-electron reduction waves with positive AE differences were obtained, indicating large disproportionation constants. The unusually small separation of the two redox steps in comparison to the... 

On heating with dimethyl sulfoxide, 2-hydroxymethylquinoxaline 1,4-dioxide undergoes a redox reaction in which 2-carboxyquinoxaline 4-oxide is formed. Similar treatment of 2,3-bis(hydroxymethyl)quinoxaline... 

Figure 2 NMR (10.17 MHz) spectrum of 4,6-dinitro-3-nitro-soaniline in dimethyl sulfoxide (<5 N)= -473.9 (NO), 0.0) CH3NO2, reference compound, -14.4 and -14.9 (2 x NO2) and -293.9 NH2). (Machacek V, Hassanien MMM, Sterba V, and Lycka A (1987) Formation of 4,6-dinitro-2-nitrosoaniline by intermolecular redox reaction of esters and amides of 2- 2,4,6-trinitroaniline) carboxylic acids. Journal of the Chemical Society, Perkin Transaction II, p. 869 reproduced by permission of The Royal Society of Chemistry.)...

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