Electron spin resonance acceptors

Electron donor-acceptor complexes, electron transfer in the thermal and photochemical activation of, in organic and organometallic reactions, 29, 185 Electron spin resonance, identification of organic free radicals, 1, 284 Electron spin resonance, studies of short-lived organic radicals, 5, 23 Electron storage and transfer in organic redox systems with multiple electrophores, 28, 1... 

Many workers have looked for electron spin resonance absorption in complexes having either powerful donors (D), powerful acceptors (A),... 

In that same year, a rather revolutionary publication appeared [35] on The Scope of the Reaction Between Carhanions or Nitron ions and Unsaturated Electron Acceptors. Many carbanions and nitranions seemed to react with unsaturated molecules, such as nitroaromatics, azobenzene, and diaryl ketones, to form the radical anions derived from the unsaturated compounds. The same effect was observed with n-butylmagnesium bromide and n-butyllithium. The radical anions were observed with the aid of electron spin resonance... 

Possible electron transfer processes merit discussion, a priori, because of the relatively low solid-state ionization energy of the PDA backbone (2) and the strong acceptor character of bromine. Since the resultant products of bromination are largely diamagnetic, a long-lived electron transfer product is not involved. Moreover, when the bromination reaction is monitored by electron-spin resonance ( ), no buildup of a paramagnetic species was noted. In view of these observations, reaction via electron transfer as a major process is ruled out. 

Sears, P. G., Wolford, R. K., and Dawson, L. R. (1956). Conductances of some acids, bromides, and picrates in dimethylformamide at 25°C. J. Electrochem. Soc. 103, 633-636. Senesi, N. (1981). Free radicals in electron donor-acceptor reactions between a soil humic acid and photosynthesis inhibitor herbicides. Z. Pflanzenernahr Dung. Bodenkd. 144, 580-586. Senesi, N., Chen, Y., and Schnitzer, M. (1977a). Hyperfine splitting in electron spin resonance spectra of fulvic acid. Soil Biol. Biochem. 9, 371-372. 

AR McIntosh, M Chu and JR Bolton (1975) Flash photolysis electron spin resonance studies of the electron acceptor species at low temperatures in photosystem I of spinach subchloroplast particles. Biochim Biophys Acta 376 308-314... 

Electron spin resonance reveals the unpaired electrons associated with impurities or structural defects and can be used to identify the lattice site positions of these features. Nitrogen is shown to substitute for carbon and acts as a shallow donor. The various ESR triplets due to nitrogen in several SiC polytypes give information on the lattice sites occupied. For the acceptor boron, ESR shows it to occupy Si sites only, in disagreement with DAP photoluminescence measurements which show only boron on carbon sites. It may be that boron substitutes on both sites and the two techniques have sensitivity for only one particular lattice site. The aluminium acceptor is not observed in ESR but gallium has been noted in one report. Transition metals, Ti and V, have been identified by ESR both isolated on Si sites and in Ti-N complexes. Several charged vacancy defects have been assigned from ESR spectra in irradiated samples. 

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