ESR Spectra Of Nitroxide Radicals Research Articles

Temperature dependence of ESR spectra of nitroxide spin probe in glassy polymers

AbstractTemperature dependencies of ESR spectra of nitroxide spin probes in glassy polymers near and below glass transition temperature were examined in detail. Three temperature ranges, each characterized by specific changes in spectral shape, were defined. (i) In the low temperature range, ESR spectra of nitroxide radical in glassy polymer matrix weakly depend on temperature and remain qualitatively the same. (ii) In the intermediate temperature range, significant changes in the shape of spectra are observed. (iii) A new phenomenon was revealed near and below glass transition temperature: narrowing of linewidths occurs while the ratio of amplitudes of different components varies insignificantly. Analysis of molecular rotational mobility was carried out by means of commonly used empirical approaches. It was shown that widely used formulas and empirical approaches are not applicable for characterization of molecular mobility in glassy polymers. Mechanisms of rotational molecular movements in glassy polymers are discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 563–575, 2009

Hydroxylamine Derivative in Purex Process III. The Kinetics of Oxidation-reduction Reaction Between N,N-diethylhydroxylamine and Neptunium(VI)

The kinetics of oxidation-reduction reaction between N,N-diethylhydroxylamine (DEHAN) and neptunium (VI) in nitric acid media has been studied by spectrophotometry at 25.2 °C. The rate equation is -d[Np(VI)/dt=k[Np(VI)][DEHAN]/[H+] found by investigating the influence of concentration, acidity, ionic strength and temperature on the reaction. The rate constant of the reaction k is 23.0±1.8 min−1 for μ = 2.0 mol/l. A possible mechanism of reaction has been suggested according to the ESR spectra of nitroxide radical produced in the DEHAN+V(V) system.

ChemInform Abstract: ESR Spectra of Nitroxide Radicals (III) Formed from Some 4‐Nitrosopyrazole Derivatives in the Trapping of ·CH2OH and ·CH3 Radicals

ChemInformVolume 20, Issue 37 Preparative Organic Chemistry ChemInform Abstract: ESR Spectra of Nitroxide Radicals (III) Formed from Some 4-Nitrosopyrazole Derivatives in the Trapping of ·CH2OH and ·CH3 Radicals C. LAGERCRANTZ, C. LAGERCRANTZ Dep. Med. Phys., Univ. Goeteborg, S-400 33 Goeteborg, Swed.Search for more papers by this author C. LAGERCRANTZ, C. LAGERCRANTZ Dep. Med. Phys., Univ. Goeteborg, S-400 33 Goeteborg, Swed.Search for more papers by this author First published: September 12, 1989 https://doi.org/10.1002/chin.198937105Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue37September 12, 1989 RelatedInformation

ESR Spectra of Nitroxide Radicals Formed from Some 4-Nitrosopyrazole Derivatives in the Trapping of .CH2OH and .CH3 Radicals.

ESR Spectra of Nitroxide Radicals Formed from Some 4-Nitrosopyrazole Derivatives in the Trapping of .CH2OH and .CH3 Radicals.

Dipolar and spin exchange effects in the ESR spectra of nitroxide radicals in solution: Part I. Pure water solution

The electron spin—electron spin interactions in aqueous solutions of a negatively charged nitroxide radical (2,2,5,5-tetramethylpyrrolidine-1-oxyl-3-carboxylate, Tempydo −) have been analyzed as a function of concentration and of temperature in order to suggest possible uses of this kind of probe in colloidal and biological systems. The dipole—dipole broadening was effective starting from a radical concentration > 2.5 × 10 −3 M, whereas the Heisenberg spin exchange began to be effective above 7.5 × 10 −3 M. Both spin—spin interactions followed the temperature and viscosity dependence predicted by the current theories. The Smoluchowsky theory for diffusion-controlled collision between nitroxide radicals was quite well fulfilled in water.

Dipolar and spin exchange effects in the ESR spectra of nitroxide radicals in solution: Part II. Water solutions adsorbed on porous silica gels

The analysis of the ESR lineshape of a negative nitroxide radical (2,2,5,5-tetramethylpyrrolidine-1-oxyl-3-carboxylate, Tempydo −) introduced as aqueous solutions into silica gels with different pore diameters indicated that the probe was prevalently localized in the intermediate and central regions of the pores. As a function of concentration inside the pores, line broadening effects that depend on the water mobility and therefore on the pore diameter were observed. Dipole-dipole broadening prevailed at low temperature and in narrow pores, while Heisenberg spin exchange dominated at high temperatures. Adsorbed water did not behave as predicted by the Smoluchowsky theory for diffusion-controlled collisions, thus proving anomalous properties of the adsorbed water.

Computer simulation of the superhyperfine structure of the ESR spectra of nitroxide radicals in solution

Calcul du spectre RPE de solutions de Tempol montrant une structure superhyperfine due aux protons du squelette moleculaire. La concordance des spectres theoriques et experimentaux permet une determination exacte du temps de correlation, dont l'application est importante en chimie et biochimie

Detection of the kinetics of biochemical reactions with oxygen using exchange broadening in the ESR spectra of nitroxide radicals

To detect changes in the oxygen concentration during biochemical reactions, the exchange broadening in the ESR spectra of nitroxide radicals caused by the dissolved oxygen, has been used. The measurements have been carried out using changes in the width either of the proton hyperfine structure components or of the nitrogen hyperfine structure line with an unresolved proton structure. Detection of mitochondrial respiration in a volume of about 10 −3 cm 3 and respiration for 100±5 liver cells in a volume of about 10 −4 cm 3 has been carried out.