AN ELECTRON SPIN RESONANCE INVESTIGATION OF ANION RADICALS 1,4-DIMETHYLANTHRASEMIQUINONE AND 1,4,5,8-TETRAMETHYLANTHRASEMIQUINONE

Electron spin resonance spectra have been observed for the radical anions 1,4,5,8-tetramethylanthrasemiquinone and 1,4-dimethylanthrasemiquinone. For the former radical in dimethoxyethane solution we find 12 equivalent methyl protons with aH = 0.329 G and 4 ring protons with aH = 1.153 G. Assignments for spectra of both radicals indicate that the methyl groups are freely rotating on the time scale of the esr experiment. This finding is in contrast to a previous report in which rotation of methyl groups in the 1 position of several anthrasemiquinone anions was reported to be so strongly hindered that the protons were no longer magnetically equivalent.