The g tensor in disubstituted phenothiazine cation radicals. Substituent and packing effects

The results of an ESR study of two homologous series of phenothiazine derivatives, in polycrystalline form and in liquid and frozen solutions, are analyzed in order to determine the influence of the R₂ and R₁₀ substituents on the g tensor. In solution the g-values are mainly affected by R₂ through electronic effects, however in polycrystalline form both substituents can modify the g-values through packing effect. A highly electronegative R₂ substituent can induce a different molecular stacking.