Search

Examines the synthesis of morpholin-4-ylphosphoramidic acid diethyl ester (1a) and (2,2,6,6-tetramethylpiperidin-1-yl)phosphoramidic acid diethyl ester (2a). Characterization of formed hydrazyl radicals 1b and 2b by electron paramagnetic resonance spectroscopy; Dependence of 1b radical spectra on temperature; Determination of constants for cyclodextrins.

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]

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: Chalcone, flavone, and arylideneflavanone derivatives bearing one or two 3,5-di-tert-butyl-4-hydroxyphenyl groups were synthesized from 2′,4′-dihydroxyacetophenone and 3,5-di-tert-butyl-4-hydroxybenzaldehyde. These flavonoids were converted into the corresponding malonates and then reacted with C60 to yield the title compounds. The O–H bond dissociation enthalpies (BDE) and the chain-breaking antioxidant activity of the flavonoid derivatives and the corresponding C60 conjugates were evaluated. These results are consistent with the phenolic moiety being the main responsible for the reaction with peroxyl radicals, while the C60 part of the molecule acts synergically by trapping alkyl radicals under reduced O2 partial pressure. These novel C60–flavonoid conjugates are therefore promising leads for broad-spectrum radical scavengers. [Copyright &y& Elsevier]

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]