Electron paramagnetic resonance characteristics

L. A. Franks, and R. K. Mullen, Time Dependent Electron Paramagnetic Resonance Characteristics of Detonated Primer Residues, U.S. Dept, of Justice, Law Enforcement Assistance Administration, National Institute of Law Enforcement and Criminal Justice (November 1972). 

Yonetani, T., Yamamoto, FI., Erman, J. E., Leigh, J. S., Jr., and Reed, G. H. (1972). Electromagnetic properties of hemoproteins. V. Optical and electron paramagnetic resonance characteristics of nitric oxide derivatives of metalloporphyrin-apohemoprotein complexes. J. Biol. Chem. 247, 2447-2455. 

The [Fe =0(TMP+ )]+ complex exhibited a characteristic bright green color and corresponding visible absorbance in its UV-vis spectrum. In its NMR spectrum, the meta-proton doublet of the porphyrin mesityl groups were shifted more than 70 ppm downfield from tetramethylsilane (TMS) because they were in the presence of the cation radical, while the methyl protons shift between 10 and 20ppm downfield. In Mossbauer spectroscopy, the isomer shift, 5 of 0.06 mm/s, and A q value of 1.62mm/s were similar to those for other known Fe(IV) complexes. Electron paramagnetic resonance (EPR), resonance Raman (RR), and EXAFS spectroscopies provided additional indications of an Fe =0 n-cation radical intermediate. For instance,... 

Fig. 6. Electron paramagnetic resonance signal showing the g= 1.94 characteristic of the dithionite-reduced spinach ferredoxin, a plant-type iron-sulfur protein. Spectrum taken at 20 °K...

When one looks for methods to detect OH, one always has two keep in mind that these radicals are very reactive, and in the presence of substrates their steady-state concentrations are extremely low even at a high rate of OH production. The fact that OH only absorbs far out in the UV region (Hug 1981) is thus not the reason why an optical detection of OH is not feasible. Electron paramagnetic resonance (EPR) must also fail because of the extremely low steady-state concentrations that prevail in the presence of scavengers. The only possibility to detect their presence is by competition of a suitable OH probe that allows the identification of a characteristic product [probe product, reaction (41)]. When this reaction is carried out in a cellular environment, the reaction with the probe is in competition with all other cellular components which also readily react with OH [reaction (42)]. The concentration of the probe product is then given by Eq. (43), where [ OH ] is the total OH concentration that has been formed in this cellular environment and q is the yield of the probe product per OH that has reacted with the probe. 

The spectrum for LaY impregnated with vanadyl naphthenate shows a characteristic band at 365 nm that loses most of its intensity after calcination, Figs. 5a, 5b. This is not surprising since Pompe et al (30), using TGA/DTA data,have shown that the oxidative decomposition of the vanadyl naphthenate is complete at 500°C. Electron paramagnetic resonance (EPR) studies have shown that vanadium (after calcination) is stabilized mainly in the form of vanadyl (V02+) cations in the zeolite supercages (29). 

The reagent alkali metal/naphthalene in tetrahydrofuran reacts with graphite, polynuclear aromatics, and various coals to form chemically reduced products. In the present paper, we emphasize the use of electron paramagnetic resonance data, in the form of g values, linewidths, radical densities, and saturation characteristics, to analyze the reduced coal products and to infer certain differences between the reduced coals and the anions of graphite and simple aromatic hydrocarbons. Additionally, because the interaction of coals with alkali metal/naph-thalene requires much time for completion, we have investigated internal decomposition pathways for the... 

---