An electron spin resonance reinvestigation of dihydropyridyl radicals

Abstract

An e.s.r. study of substituted dihydropyridyl radicals is reported. Some spectra previously described have been reinterpreted and the structures of the radicals reassigned. The factors influencing the persistence of dihydro-pyridyl radicals are discussed. In one case (4-aceteyl-1-methyidihydropyridyl) extraordinarly large variations of hyperfine splitting constants with solvent were observed: these were explained in terms of mesomerism. The large solvent-induced redistribution of spin density makes this radical a useful substrate for studying medium effects.