One-electron reduction product

Apart from the nuclear bromination observed (Section 2.15.13.1) in the attempted radical bromination of a side-chain methyl group leading to (396), which may or may not have involved radical intermediates, the only other reaction of interest in this section is a light-induced reduction of certain hydroxypyrido[3,4-f)]pyrazines or their 0x0 tautomers analogous to that well-known in the pteridine field (63JCS5156). Related one-electron reduction products of laser photolysis experiments with 1 -deazaflavins have been described (79MI21502). 

In the same year, Evans and coworkers reported the electrochemical reduction of protons to H2 catalyzed by the sulfur-bridged dinuclear iron complex 25 as a hydrogenase mimic in which acetic acid was used as a proton source [201]. The proposed mechanism for this reaction is shown in Scheme 60. The reduction of 25 readily affords 25 via a one electron reduction product 25. Protonation... 

The adsorption maximum of 496 nm characteristic of one electron reduction product of TQ was not observed. TQH2 in DCE could not be determined because of the distribution of TQH2 to W. 

Solutions of tetrazolium salts, e.g., 53, have been reported to both become colored and bleached under the influence of both UV and visible light. Several workers have attributed this phenomenon to photoreduction to the corresponding formazan (51) and the formation of a fluorescent colorless compound (152) through photooxidation.240- 243 The reduction of 152 under UV or blue light to the intense green radical structure (153) has also been reported (Scheme 21).244 A one-electron reduction product (154) is proposed as a short-lived intermediate in the photoreduction.245... 

One-Electron Reduction Product of Tris(2,2 -bipyridine)rhodium(III)... 

A detailed study of the electronic, vibrational, and e.s.r. spectra of a series of substituted dipyrromethane complexes of nickel(ii) has been reported." The reduction of the nickel(ii) 1,19-diethoxycarbonyltetradehydrocorrin cation with a sodium film in THF under high vacuum gives both one- and two-electron reduction products. The one-electron reduction product is a very stable free radical, and the other product is formulated as a Ni" species with the two extra electrons located in ligand n-orbitals. The structures of nickel-(ii)-octaethylporphin and nickel(ii)-deoxophylloerythrin methyl ester-1,2-... 

The bis-hydroxylamine adduct [Fe (tpp)(NH20H)2] is stable at low temperatures, but decomposes to [Fe(tpp)(NO)] at room temperature. [Fe(porphyrin)(NO)] complexes can undergo one-and two-electron reduction the nature of the one-electron reduction product has been established by visible and resonance Raman spectroscopy. Reduction of [Fe(porphyrin)(NO)] complexes in the presence of phenols provides model systems for nitrite reductase conversion of coordinated nitrosyl to ammonia (assimilatory nitrite reduction), while further relevant information is available from the chemistry of [Fe (porphyrin)(N03)]. Iron porphyrin complexes with up to eight nitro substituents have been prepared and shown to catalyze oxidation of hydrocarbons by hydrogen peroxide and the hydroxylation of alkoxybenzenes. ... 

Reaction (26) is followed by a first order process, which has been interpreted as an homolytic splitting of the N-S bond, Eq. (27), with formation of the one-electron reduction product of NP, [Fe(CN)sNO]3, ... 

For the dimer, polographic results in CH3CN reveal a four-membered series (Eq. 32), and the one-electron reduction product was isolated (434). 

At the same time, dimerization of one-electron reduction product was indicated by oscillopolarographic studies in acid for l-R-3,4-diphenyl-6,7-dimethoxybenzo[c]pyrylium perchlorates (R = Me, Et, Ph) (76MI1). As was noted in Section III,F, 1, the benzo[c]pyrylium cation 261, unsubstituted in position 1, undergoes l, 1 -dimerization via the postulated intermediate radical, and the bisisochromene 263 thus formed is readily converted into the initial monomeric salt, but not into the corresponding biscation on treatment with chemical electron acceptors (76KGS999). 

Table 10 Absorption spectra for sulfones 235 and their one-electron reduction products...

Also, the introduction of methyl viologen (MV2+, paraquat) in biological systems results in the formation of its one-electron reduction product, MV+-, which mediates the production of O2 ... 

Recently, the perchlorate of 2,3,7,8-tetramethoxythianthrenium dication has been prepared.Interestingly, this material exists as a ground-state triplet as part of the study of this material its one-electron reduction product, the cation-radical 179, has been well characterized by ESR (indicated hyperfine splittings are in gauss). Comparison of the splittings in 178 and 179 shows the substitution to bring about a redistribution of the spin... 

Superoxide anion, O2 One-electron reduction products of O2, produced by phagocytes formed in autoxidation reactions generated by oxidases (heme protein). 

Pyrazine and its reduction product 1,4-dihydropyrazine form a system that at a mercury electrode behaves nearly reversibly [322, 323]. In acid solution, two one-electron waves are found, indicating a certain stability of the semiquinone-type one-electron reduction product. In substituted pyrazines, the initially formed reduction product, the 1,4-dihydropyr-azine, may tautomerize into the less easily oxidizable 1,2- or 1,6-dihydropyrazine the rate of tautomerization is pH dependent [324]. 

The variable temperature and 13C NMR spectra for the stable radical anions [Os3(CO).)(p3-r 2-L)(. i-[ I)], where HL = phenanthridine, 5,6-ben-zoquinoline, quinoxaline and their one-electron reduction products, showed that electron transfer between neutral and uninegative species occurs on the NMR timescale.1068 Proton NMR studies have been reported for isomerisation between the three known isomers of OsCl2(dmso)4.1069... 

The complex (57) shows vN=0 of the nitrosoaryl ligand at 1301 cm-1.308 IR spectroelectrochemistry (vNO) reveals that reduction of ClsIr(NO)- is reversible, and predominantly NO-centred, i.e. vNO is at 1952 cm-1 for original complexes, 1677 cm-1 for the one-electron reduction product.309 NO adsorbed on supported iridium catalysts (Ir/Si02, Ir/Al203) gives vNO at 1870 cm-1 from Ir5+(NO) species.310... 

---