ESR spectra of semiquinone radicals, formed as intermediary reduction products in reversibly reducible thiazine and oxazine dyestuffs, have been investigated in acid as well as in alkaline solution.
In acid solutions at relatively high concentration of the dye the spectra consist of four lines. In alkaline solutions at high concentration there are three lines. At lower concentrations most spectra could be resolved further into many components.
A tentative interpretation of the spectra is given.
The high-resolution ESR spectrum of the radical of 4,4′-dipyridyl (Tony blue) is observed and analyzed. Dipyridyl in alcoholic solution is converted into Tony blue upon irradiation with sunlight. The spectrum consists of 153 lines, each of less than 0.1 gauss width. The measurements were also extended to a partially deuterated compound of Tony blue, and the analysis was found to be in agreement with the former within the limits of observation.
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