Electron transfer generation

The previous examples of eel were interpreted on the basis of a relatively simple mechanism. In these cases the back electron transfer generates directly the emitting excited state (annihilation). However, in more complicated systems back electron transfer and formation of an emitting state may be separate processes... 

The first (reversible) electron transfer generates the ketyl anion-radical. The ketyl moiety then attacks the aryl group in the ortho position. The resulting cyclohexadienyl radical is reduced to a cyclohexadienyl anion by a second electron transfer, and the anion is finally protonated. HMPA as... 

G. Pandey, Synlett 1992, 546-552 . .Synthetic Perspectives of Photoinduced Electron Transfer Generated Amine Radical Cations". 

The critical difference between the electrode and powders probably centers on the different operative space-charge thickness developed on each surface. On a powder, a newly formed radical will remain isolated, persisting until back electron transfer generates an anion, protonation of which allows for surface desorption, Eq. (27). 

This chemoluminescence results from interaction of 156 (generated from 155 under thermal conditions) and 1,3-DIBF (formed in a minor amount from 156). The first step is the formation of an encounter complex. Electron transfer generates a peroxide radical anion of 156 and a radical cation of 1,3-DIBF. Cleavage of the 0-0 bond in the radical anion of 156 forms an o-dibenzoylbenzene radical anion. Annihilation of the oppositely charged ions gives an excited singlet of 1,3-DIBF (with subsequent fluorescence) (82JA1041). 

Voluminous studies have been made to distinguish the reactivity of singlet oxygen, triplet oxygen, and electron transfer-generated superoxide (228). For example, while superoxide gives both endoperoxide and side chain oxidation of 1,4-dimethyl-naphthalene, eq. 73 (229),... 

If electron transfer generates a charged ion which is hydrophilic and bears the same charge as the micelle, its expulsion from the micellar cage will reduce the rate of back electron transfer. In a cationic micelle, for example, electron transfer from dimethylaniline to excited Ru(bpy ), +> eq. 86,... 

Phenothiazine is readily oxidized when irradiated in solution with chlorinated hydrocarbones (8). The reaction has been shown to be an electron transfer generating the phenothiazine (PTH) radical cation (PTH+ ) and the halogen anion as shown in equation 1. hv. ... 

Pandey, G., Karthikeyan, M., and Mumgan, A. (1998) New intramolecular a-arylation strategy of ketones by the reaction of silyl enol ethers to photosensitized electron transfer generated arene radical cations construction of benzannulated and benzospiroannulated compounds. Journal of Organic Chemistry, 63, 2867-2872. 

The same Anal product 175 is obtained in the reaction of spirostiborane 150 with liquid sodium-potassium alloy, most probably via initial one-electron-transfer generating the anion radicals 176a and/or 176b131. ... 

For essentially all n systems, electron transfer is connected with particular changes in the electronic absorption spectra. Thus, the usefulness of aromatic (poly)-anions and cations should particularly come to pass in cases when electron-transfer generated stages occur as short-lived mediators or as optoelectronic devices and sensors. 

Each electron transfer generates a proton or Lewis acid at the anode and a hydroxyl ion or Lewis base at the cathode. This creates strongly acidic or basic media in the reaction layers adhering to the anode or cathode, whereby acid- [24] or base-catalyzed reactions [25] can be induced (see Chapter 30). 

Mazzocchi, P. H., Klingler, L. Photoreduction of N-methylphthalimide with 2,3-dimethyl-2-butene. Evidence for reaction through an electron transfer generated ion pair. J. Am. Chem. Soc. 1984,106, 7567-7572. 

Single electron transfer generates radicals and although this mechanism is now more common than once thought in non-biological redox reactions, its prevalence in enzyme-catalysed reactions is limited to coenzymes with quinoid-type structures e.g. flavins, coenzyme Q, vitamins C, E and K and to enzymes containing transition metals. Of course, there is a growing interest in metabolic disorders initiated by radical reactions. Reduction by 2-electron transfer can take place by either (a) hydride, H, transfer or (b) discrete electron, e , and proton, H", addition. 

Cyano substituents have important influences on the electrochemical reductive cleavage of C—O bonds of 2-, 3- and 4-cyanoanisoles in DMF. Under cyclic voltammetric conditions reversible electron transfer, generating radical anions, was observed for 2- and... 

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