Skip to Main content Skip to Navigation
Journal articles

Combined ESR and Thermodynamic Studies of the Superoxide Adduct of 5-(Diethoxyphosphoryl)-5-Methyl-1-Pyrroline N-Oxide (DEPMPO): Hindered Rotation around the O-O Bond Evidenced by Two-Dimensional Simulation of Temperature-Dependent Spectra

Abstract : Experiments were performed to elucidate the origin of the superhyperfine structure and line width alternation (LWA) seen in the ESR spectrum of the major diastereoisomer (1) of DEPMPO-OOH, the remarkably persistent superoxide adduct of 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO). Using selectively deuterated DEPMPO derivatives, we demonstrated that the superhyperfine pattern can be unambiguously attributed to long-range couplings. The recording in pyridine of highly resolved spectra in a wide temperature range, combined with two-dimensional simulation, allowed us to characterize an inverted LWA in 1 and revealed a uniform line broadening in the spectrum of the minor DEPMPO-OOH diastereoisomer (2), with both effects originating from a chemical exchange between conformers. When the individual spectra of 1 presenting LWA in the fast-exchange regime were simulated, four equally good fits were obtained and this ambiguity could be resolved by using a two-dimensional simulation technique. The thermodynamic and kinetic constants of this exchange were consistent with a rotation around the O-O bond. We propose that line broadening effects in 1 and 2 result from this O-O rotation concerted with the pseudo-rotation of the pyrrolidine ring.
Complete list of metadatas

https://hal-amu.archives-ouvertes.fr/hal-01142288
Contributor : Marcel Culcasi <>
Submitted on : Tuesday, April 14, 2015 - 9:01:08 PM
Last modification on : Thursday, September 6, 2018 - 4:00:03 PM

Links full text

Identifiers

Collections

Citation

Antal Rockenbauer, Jean-Louis Clément, Marcel Culcasi, Anne Mercier, Paul Tordo, et al.. Combined ESR and Thermodynamic Studies of the Superoxide Adduct of 5-(Diethoxyphosphoryl)-5-Methyl-1-Pyrroline N-Oxide (DEPMPO): Hindered Rotation around the O-O Bond Evidenced by Two-Dimensional Simulation of Temperature-Dependent Spectra. Journal of Physical Chemistry A, American Chemical Society, 2007, 111, pp.4950. ⟨10.1021/jp070679u⟩. ⟨hal-01142288⟩

Share

Metrics

Record views

149