title: Diketone radical cations: ketonic and enolic forms as revealed by matrix EPR studies and DFT calculations.
abstract: Radical cations of 2,3-butanedione, 2,4-pentanedione, 3-methylpentane-2,4-dione, 2,5-hexanedione, and 2,3-pentanedione were investigated by electron paramagnetic resonance (EPR) spectroscopy in a solid Freon matrix and density functional theory (DFT) quantum chemical calculations. All the diketone radical cations in ketonic form show small proton hyperfine couplings (typically unresolved in the EPR spectra). In the cases of 2,4-pentanedione and 3-methylpentane-2,4-dione, enolic forms of the radical cations (pi-type species with main spin population at carbon atom) were characterized. Preferential stabilization of the enolic form of 3-methylpentane-2,4-dione radical cation was explained by trap-to-trap positive hole migration rather than monomolecular relaxation of the ionized ketonic form through H atom transfer.
authors.affiliation: Department of Chemistry, Moscow State University, Moscow 119992, Russia. kirill.nuzhdin@rad.chem.msu.ru
authors.forename: Kirill B
authors.initials: KB
authors.lastname: Nuzhdin
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Feldman
authors.forename: Aleksey V
authors.initials: AV
authors.lastname: Kobzarenko