The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

Abstract

. Can. J. Chem. 66, 2395 (1988). ~, We report the first 'H and ' 4~ electron nuclear double resonance (ENDOR) spectra of oxygen-centered radical adducts (i.e.,derived from the addition of tert-butoxyl radicals) of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as well as the related cyclic nitrones: 4-phenyl-5,5-dimethyl-1-pyrroline-N-oxide (4-Ph-DMPO) and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO).Features of the electron paramagnetic resonance (EPR) and ENDOR spectra of these cyclic (pyrrolidine) aminoxyl (nitroxide) species along with some deuterated analogues in liquid toluene solutions are highlighted. For instance, we found several long-range y-H hyperfine splittings (HFS's) detectable by ENDOR that provide unique spectral signatures for these radical adducts. Conformational assignments of the pyrrolidine aminoxyl structures based upon the EPR and ENDOR findings are also discussed. Signs of the various hyperfine splittings (i.e., aN, a;, a : ) investigated by cross-relaxation intensity sequence patterns (CRISP) in the ENDOR spectra are also presented. [Traduit par la revue]

Effects of temperature on the ESR and ENDOR spectra of the DMPO-OBut spin adduct; the problems of identifying the trapped radical

“…This is assigned to TMPO-OBu t . This provides strong evidence that a proton in the 3-position generates the further splitting seen with most oxygen-centred DMPO adducts, in agreement with the conclusions of Haire et al 6 from their detailed ENDOR studies of this spin adduct.…”

“…In addition to theˇ-proton and -proton coupling seen by ESR, an additional coupling of 0.01 mT with six methyl protons is also observed in the ENDOR spectrum, which is less than the ESR linewidth of 0.131 mT. An additional coupling of 0.046 mT has been attributed to a υ-proton, in agreement with the assignment of a υ-proton coupling of 0.031 mT in toluene as solvent at 200 K. 6 Haire et al 6 detected only four ring proton ENDOR lines, but we have been able to resolve a fifth coupling of 0.025 mT in 2MB to either the 3or 4-position. Table 1 lists the paramagnetic parameters determined in this study compared with those of Haire et al at the higher temperature.…”

Dual‐Functioning Molecular Carrier of Superoxide Radicals for Stable and Efficient Lithium–Oxygen Batteries

“…The chemical stabilization of the DMPO–O 2 − complex, which is attributable to the resonance effect, leads to a substantial reduction in the parasitic reactions involving the radicals. [ 50,51 ] We also reveal that DMPO promotes the charging process by actively scavenging the superoxide species formed on the surface of the solid Li 2− x O 2 upon charging, implying its dual function during both discharge and charge. These activities lead to a remarkable reduction of the overpotential and a high oxygen efficiency, as confirmed by differential electrochemical mass spectrometry (DEMS) and cyclability analyses.…”

Chiral Spin Traps. The Spin Trapping Chemistry of 5-Methyl-5-phenylpyrroline-N-oxide (MPPO)

“…Other groups are finding their way into trap-derived radical. This problem has surfaced in studies the 3-and 4-position (17,29,30).…”

“…2-Ph-DMPO has only one carbon atom more than PBN and might have similar properties as a spin trap in biological systems. In further work from these laboratories, we are investigating the effect of moving the phenyl group in DMPO around the ring: to the 3-position (31), the 4-position (29), and the 5-position (this paper). An earlier study with 3-methyl-and 4-methyl-DMPO can be reinterpreted in a similar fashion (38).…”