Single-phase primary electron spin polarization transfer in spin-trapping reactions

Abstract

Time-resolved (TR) ESR was employed to investigate the reaction of diphenylphosphinoyl reactive free radicals with N-phenyl-tert-butylnitrone (PBN), which were produced by laser flash photolysis (YAG laser, 355 nm) of diphenyl-2,4,6-trimethylbenzoyl phosphine oxide (DPO). The TR ESR and continuous wave (cw) ESR spectra of the nitroxide spin adduct of diphenylphosphinoyl radicals and PBN were investigated, and both spectra of the adduct show the same hyperfine-splitting and relative line intensities. The TR ESR spectra of the spin adduct as well as the initial diphenylphosphinoyl radicals are absorptively polarized, corresponding to a net electron spin polarization transfer. The requirements for spin polarization transfer in radical addition reactions and the TR and cw ESR spectrum of the spin adduct are discussed.