| 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 Freonmatrix and density functional theory (DFT) quantum chemical calculations. All the diketone radical cationsin ketonic form show small proton hyperfine couplings (typically unresolved in the EPR spectra). In thecases of 2,4-pentanedione and 3-methylpentane-2,4-dione, enolic forms of the radical cations (π-type specieswith main spin population at carbon atom) were characterized. Preferential stabilization of the enolic form of3-methylpentane-2,4-dione radical cation was explained by trap-to-trap positive hole migration rather thanmonomolecular relaxation of the ionized ketonic form through H atom transfer.
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