Electron paramagnetic resonance evidence for the dihydro-9,10-anthrasemiquinone transient radical anion

The dihydro-9,10-anthrasemiquinone and 9,10-anthrasemiquinone transient radicals are prepared sequentially by the reaction of tetrahydro-9,10-anthraquinone and sodium hydroxide. The B1LYP hybrid density functional method, employing triple-ζ basis sets, is used to calculate their hyperfine tensors. The dihydro-9,10-anthrasemiquinone geometry is elucidated from the agreement between the computed 1H isotropic hyperfine coupling constants and those determined by EPR simulation. Thus for the first time, accurate 1H hyperfine tensors for anthrasemiquinones may be directly computed at an economical cost.