title: Spin exchange of nitroxyl radicals in H2O and D2O.
abstract: By means of continuous wave electron spin resonance (cw ESR) in the X and L bands, the spin exchange of series of different concentrations of the spin probes 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), and 4-(trimethylamino)-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (CAT-1) in H(2)O and D(2)O have been examined. The rate constants k(e) of the spin exchange have been determined by complete spectra simulations, as well as directly from hyperfine line broadenings and concentration depending line shifts. The obtained results showed a good agreement. Their respective differences {k(e)(H(2)O) - k(e)(D(2)O)} could be determined for the first time. They reflect the different influence of the solvents on the spin dynamics but confirm the decrease of the reaction rate in D(2)O, caused by the higher degree of order in this liquid. The spectroscopic and kinetic results presented in this paper establish a further kind of isotopic effect.
authors.affiliation: Institute of Chemistry, Humboldt University Berlin, Berlin, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Stösser
authors.forename: Werner
authors.initials: W
authors.lastname: Herrmann
authors.forename: Anita
authors.initials: A
authors.lastname: Pahlke
mesh_terms: D017666:Deuterium Oxide / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D009589:Nitrogen Oxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D009589:Nitrogen Oxides; D014867:Water; C039900:nitroxyl; D017666:Deuterium Oxide