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In the presence of organic acids in organic media, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) reacts with peroxyl radicals at nearly diffusion-controlled rates by proton-coupled electron transfer from the protonated nitroxide. [ABSTRACT FROM AUTHOR]

EPR spectroscopy has been used to study the interaction of para-substituted benzyl hydroxyalkyl nitroxides with the monolayer of water-soluble protected gold cluster made by a short alkyl chain and a triethylene glycol monomethyl einer unit. The inclusion of nitroxide probes in the more hydrophobic environment of the monolayer gave rise to a reduction of the value of both nitrogen and β-proton hyperfine splittings. The spectra also showed selective line broadening attributed to modulation of the spectroscopic parameters as the result of exchange between free and complexed nitroxide. The rate constants were obtained by analyzing the EPR line shape variations as functions of nanoparticle concentration and temperature. This represents, to the best of our knowledge, the first determination of rate constants for the solubilization of organic substrates in a monolayer-protected cluster. [ABSTRACT FROM AUTHOR]

Examines the chemical reactions involving the tetramethyl-1-piperidinoxyl (TEMPO) compounds along with the related nitroxides. Characterization of the metal hydrides; Proposal of a mechanism for the reduction of TEMPO by the two trimethylsiyl-substituted silanes; Information on the behavior of the nitroxide radicals.

The article demonstrates that the core size of metallic nanoparticles impart different solvating properties to the protective organic monolayers. It reports on the measurement of partition isotherms of an organic probe between an aqueous solution and the monolayer of water-soluble monolayer-protected gold clusters of different sizes. It argues that ESR spectroscopy is a simple and powerful tool to investigate the binding properties of nanoparticles that, are difficult to obtain by other techniques. Using ESR spectroscopy, it illustrates the monitoring of the partition of lipophilic nitroxides between the monolayer of water-soluble nanoparticles and bulk water.

Abstract: Halogen-bonded complexes between aliphatic and aromatic iodoperfluorocarbons and persistent nitroxide radicals have been detected by ESR spectroscopy in solution. Quantitative data indicate that nitroxides behave as strong electron donors in halogen bonding, giving rise to interactions whose strength is close to that of strong hydrogen bonds. These results point to a novel design of supramolecular paramagnetic species. [Copyright &y& Elsevier]

An EPR investigation of the kinetics of the exit, k[sup -], and entrance, k[sup +], processes in micelles of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide and polyoxyethylene(6)decanol of a family of para-substituted benzyl tert -butyl nitroxides and para-substituted benzyl hydroxyalkyl nitroxides is reported. The inclusion of nitroxide probes in the hydrophobic environment of the micelle gives rise to a reduction of the value of both nitrogen and β-proton splittings, with the result that the resonance fields for the M[sub I](2H[sub β]) = ±1lines of the free and included species are significantly different. The rate constants were obtained by analyzing the EPR line shape variations as function of surfactant concentration and temperature. The experimental value of k[sup +] obtained from the study of benzyl tert-butyl nitroxide indicates that the association reaction is very close to being controlled by diffusion. The value of the exit rate, k[sup -], instead, depends on the probe hydrocarbon chain length. A comparison of our results with those obtained by luminescence quenching techniques is also reported. [ABSTRACT FROM AUTHOR]