Magnetic Susceptibilities of Crystalline Phenothiazine, N-Methylphenothiazine and Thianthrene Radical Salts with Antimony Pentachloride

Phenothiazine, N-methylphenothiazine and thianthrene are oxidized with antimony pentachloride, and give the corresponding monopositive ion radicals. These aromatic positive ions form crystalline salts with the complex negative ion of antimony pentachloride or tetrachloride. The paramagnetism for these salts is attributed to the aromatic ion radicals, and follows the Curie-Weiss law at higher temperatures, and deviates from it at lower temperatures. This behavior has been interpreted by assuming the linear chain model being applicable, which suggests a remarkable spin exchange interaction in the crystalline salt of phenothiazine·SbCl4, of J/k∼395°K.