Magnetic Properties of Some Iminoxyl Polyradicals. II. TEMPOP Triradical and TEMPOS Tetraradical

The EPR spectra of the TEMPOP triradical and the TEMPOS tetraradical in solution showed seven and nine absorption lines respectively, which were interpreted as the hyperfine interaction between unpaired electron and 14N nuclei in the case of |Jin|>>A. The paramagnetic susceptibilities of TEMPOP and TEMPOS were measured. In the case of TEMPOP, no typical short-range ordering effect was found, but the 1⁄χM−T curve deviated from the Curie-Weiss law at very low temperatures. In the case of TEMPOS, the 1⁄χM−T curve was divided into four regions. In the first and third regions, the 1⁄χM−T curves both obey the Curie-Weiss law. The second region is the intermediate region between the first and third regions. In the last region, 1⁄χM−T shows a slight deviation from the Curie-Weiss law of the third region. In order to explain this behavior, some spin-cluster models with three and four spins were applied.