Electron spin resonance studies

The importance of e.s.r. in this field is mainly in achieving a detailed characterization of radical structures. Because the resonance line due to the unpaired electron is split by magnetic nuclei in the radical in a very characteristic way, the technique actually counts the various types of nuclei and allows in many cases an accurate determination of their respective position and geometrical orientation. Patterns of relationships between structure and e.s.r. parameters, based on many experimental results, have been developed and applied to new systems successfully. Details of e.s.r. methods are given in many books and reviews on the subject (see especially Fessenden and Schuler, 1970 Wertz and Bolton, 1972). 

Although much of the e.s.r. work has utilized radical production methods other than radiation, such as photolysis or rapid-mix redox reactions which can give mostly similar data, we shall limit our discussion here to those topics treated by the combined e.s.r.-radiation chemical technique in aqueous solutions. Most of these studies have been carried out by the steady-state method developed by Eiben and Fessenden (1971) and have been primarily concerned 

The reaction of OH with saturated aliphatic compounds is known to take place mainly by hydrogen abstraction from the alkyl groups. For example, amines undergo a reaction such as (32). However, 

The reaction of OH radicals with benzoate has been found to produce the three isomeric hydroxycyclohexadienyl radicals (Eiben and Fessenden, 1971). Moreover, addition to each para- and meta-position was found to take place with similar rate, whereas addition to each ortho -position proceeds at only about half that rate. 

In contrast with the addition of OH and many other radicals to the acz-form of nitromethane [reaction (34)], it has been found that 

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Fessenden R W and Schuler R H 1963 Electron spin resonance studies of transient alkyl radicals J. Chem. Phys. 39 2147-95... 

Wang P, Maruyama Y and Metzger R M 1996 Superconductivity of Cgg Langmuir-Blodgett films doped with potassium low-field signal and electron spin resonance study Langmuir M 3932-7... 

R. E. Florin and L. A. Wad, "Electron Spin Resonance Studies on Fluorination of Polymers," abstract no. 8, Fluorine Chemistry Div., 165th American ChemicalSodef Meeting, Dadas, Tex., Apr. 10,1973. 

The dithionite ion has a remarkable eclipsed stmcture of approximate C2v symmetry (Fig. 15.32b). The extraordinarily long S-S distance (239 pm) and the almost parallel SO2 planes (dihedral angle 30°) are other unusual features. Electron-spin-resonance studies have shown the presence of the S02 radical ion in solution ( 300ppm), suggesting the establishment of a monomer-dimer equilibrium 8204 ... 

In addition, Bamford, Jenkins and coworkers (19) previously reported on the behavior of occluded radicals in the heterogeneous polymerizations of acrylonitrile, methyl acrylate, methyl methacrylate and vinylidene chloride. From their electron spin resonance studies, they concluded that the degree of occlusion was ... 

McMillan has reviewed the chemistry of Ag(II) and Ag(IlI). Paramagnetism and electron spin resonance studies confirm the presence of Ag(ll) (as opposed to equimolar Ag(I)+Ag(III)). The colours of Ag(II) solutions in various mineral acids indicate the existence of complexes, the oxidising power of which is apparent from their decomposition even at 0 °C, although high acidity promotes stability. Rapid isotope exchange between Ag(I) and Ag(n) is considered to result from the equilibrium... 

Fessenden, R.W. and Verma, N.C. (1978). A time-resolved electron spin resonance study of the oxidation of ascorbic acid by the hydroxyl radical. Biophys. J. 24, 93. 

Jackson, M.J., Edwards, RH.T. and Symons, M.C.R (1985). Electron spin resonance studies of intact mammalian skeletal muscle. Biochim. Biophys. Acta 847, 185-190. 

Mukai, K. Tsuzuki, N. Ouchi, S. Fukuzawa, K. Electron spin resonance studies of chromanoxyl radicals derived from tocopherols. Chem. Phys. Lipids 1982, 30, 337-345. 

Knight, L. B., Kaup, J. G., Petzold, B., Ayyad, R., Ghanty, T. K., Davidson, E. R., 1999, Electron Spin Resonance Studies of 45Sc170, 89Y170, and 139La170 in Rare Gas Matrices Comparison With Ab Initio Electronic Structure and Nuclear Hyperfine Calculations , J. Chem. Phys., 110, 5658. 

The reduction of cyanocobalamin gives three possible oxidation states for the cobalt atom (Fig. 2). Electron spin resonance studies with Bi2-r reveals that this molecule is the only paramagnetic species giving a spectrum expected for a tetragonal low spin Co(II) complex. Controlled potential reduction of cyanocobalamin to Bi2-r proves that this reduction involves one electron, and further reduction of Bi2-r to B12-S requires a second single electron (16—19). At one time B12-S was considered to be a hydride of Co(III), but controlled potential coulometry experiments provided evidence against a stable hydride species (16). However, these experimental data do not exclude the possibility of a stable Co(III) hydride as the functional species in enzyme catalyzed oxidation reduction reactions. 

Arem, J. E. (1987), Color Encyclopedia of Gemstones, Van Nostrand-Reinhold, New York. Armiento, G., D. Attanassio, and R. Platania (1997), Electron spin resonance study of... 

Electron Spin Resonance Studies of Primary Processes in the Radiolysis of Transition Metal Carbonyls... 

Malmstrom, B.G., Mosbach, R., and Vanngard, T. 1959. An electron spin resonance study of the state of copper in fungal laccase. Nature 183 321-322. 

Although it is very hard to observe the absorption spectrum of eh when metal is dissolved in water because of its high reactivity, some attempts were made in water and ice (Jortner and Stein, 1955 Benett et al., 1964, 1967). Furthermore ESR (electron spin resonance) studies revealed that the trapped or solvated electron in ice interacts with six equivalent protons, thus ruling out H20-. 

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... 

Radiation techniques, application to the study of organic radicals, 12, 223 Radical addition reactions, gas-phase, directive effects in, 16, 51 Radicals, cation in solution, formation, properties and reactions of, 13, 155 Radicals, organic application of radiation techniques, 12,223 Radicals, organic cation, in solution kinetics and mechanisms of reaction of, 20, 55 Radicals, organic free, identification by electron spin resonance, 1,284 Radicals, short-lived organic, electron spin resonance studies of, 5, 53 Rates and mechanisms of solvolytic reactions, medium effects on, 14, 1 Reaction kinetics, polarography and, 5, 1... 

Short-lived organic radicals, electron spin resonance studies of, 5,53... 

The alkali metals in liquid ammonia give deep coloured solutions which have been shown to contain solvated electrons. The unsaturated system takes up an electron to give an anion radical. There is evidence for this species from electron spin resonance studies. It accepts a proton from the solvent to give a radical which is reduced to a carbanion by another sodium atom. Finally the addition of a proton gives the reduced product. This proton is supplied by a protic solvent like enthanol and not from NH3. 

Nickel(III) peptide complexes have a tetragonally-distorted octahedral geometry as shown by electron spin resonance studies (19) and by reaction entropies for the Ni(III,II) redox couple (17). Axial substitutions for Ni(III)-peptide complexes are very fast with formation rate constants for imidazole greater... 

Short-lived organic radicals, electron spin resonance studies of, 5, 53 Small-ring hydrocarbons, gas-phase pyrolysis of, 4, 147... 

Kuska, H. A., and M. T. Rogers Electron spin resonance studies and covalent bonding of cyanide and fluoride complexes of transition metals. J. Chem. Phys. 41, 3802 (1964). 

Jerome D (1991) The physics of organic superconductors. Science 252 1509-1514. A more detailed diagram was then proposed Dumm M, Loidl A, Travel BW, Starkey KP, Montgomery LK, Dressel M (2000) Electron spin resonance studies on the organic linear-chain compounds (TMTCF)2X (C = S, Se X = PFg, AsFg, CIO4, Br). Phys Rev B61 511-521... 

Simon, I., C. P. Burns, and A. A. Spector. Electron spin resonance studies on intact cells and isolated lipid... 

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