ESR Study of MnO42− in γ-Irradiated KMnO4

When KMnO₄ is γ irradiated at 77°K a single paramagnetic species is detected which is shown to be basically the manganate ion, $\mathrm{Mn}(\mathrm{VI}){\mathrm{O}}_4^{\text{2−}}$ , however, the single odd electron interacts at the same time with a second manganese nucleus of a neighboring diamagnetic species. Although the species giving rise to the weaker, superhyperfine ⁵⁵Mn interaction could not be identified with certainty, it is probably a neighboring ${\mathrm{MnO}}_4^{-}$ ion or ${\mathrm{MnO}}_3^{+}$ lattice defect so that the center produced might be written $[\mathrm{Mn}(\mathrm{VI}){\mathrm{O}}_4^{\text{2−}}\mathrm{···}\mathrm{Mn}(\mathrm{VII}){\mathrm{O}}_n^{\text{7−2n}}]$ . The g tensor and both ⁵⁵Mn hyperfine splitting tensors have been obtained, and the structure of the radical is discussed. On warming to room temperature a radical not containing manganese, probably ${\mathrm{O}}_3^{-}$ , is found.