The formation of the Superoxide radical anion (O 2 •-) adduct of the nitrone 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as detected by electron paramagnetic resonance (EPR) spectroscopy is one of the most common techniques for O 2 •- detection in chemical and biological systems. However, the nature of DMPO-O 2H has confounded spin-trapping investigators over the years, since there has been no independently synthesized DMPO-O 2H to date. A density functional theory (DFT) approach was used to predict the isotropic hyperfine coupling constants arising from the N, β-H, and γ-H nuclei of DMPO-O 2H using explicit interactions with water molecules as well as via a bulk dielectric effect employing the polarizable continuum model (PCM). Theoretical calculation on the thermodynamics of DMPO-O 2H decay shows favorable intramolecular rearrangement to form a nitrosoaldehyde and a hydroxyl radical as products, consistent with experimental observations. Some pathways for the bimolecular decomposition of DMPO-O 2H and DMPO-OH have also been computed.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry