Flavosemiquinone model systems. Part 2. Methyl-substituted quinoxaline radical ions

Abstract

2,3-Dimethyl-, 6,7-dimethyl-, and 2,3,6,7-tetramethyl-quinoxaline were reduced in aprotic (THF) and acidic media (DMF–HClO₄) to yield the corresponding quinoxaline radical anions and 1,4-dihydroquinoxaline radical cations. Analysis of their e.s.r. spectra was accomplished by computer simulation; a consistent assignment of coupling constants in quinoxaline radical ions could be made on the basis of the methyl substitution pattern. The hyperfine splitting is in agreement with Hückel MO correlations and may be used to explain the spin distribution in flavosemiquinones.