Syntheses of Nitronyl Nitroxide and Nitroxide Polyradicals and Their Magnetic Characterization

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Abstract
The present paper describes the syntheses of polyradicals with pendant nitronyl nitroxide (1) or nitroxide radicals (2) and their magnetic characterization. Polyradical 1 was obtained by the polycondensation of nitronyl nitroxide substituted 3,5-diethynylbenzene with 1,3-diiodobenzenes in Et3N-pyridine in the presence of (PPh3)2PdCl2- Cul. The spin concentrations were 1.12 × 1021 - 1.33 × 1021 spin/g and the number average molecular weights (Mn) were 4300 - 4800. Polyradical 2 was obtained by the polymerization of N/-tert-butyl-3-ethynyl-5-terf-phenyl nitroxide using a Rh catalyst. The spin concentration of 2 was 2.09 × 1021 spin/g and M n was 11000. Solution ESR spectra of 1 and 2 were a broad single line, and no hyperfine splittings due to nitrogen and proton nuclei were observed. This is due to the spin-exchange interaction. The SQUID measurements of 1 performed in the temperature range of 300 - 1.8 K showed that polyradical 1 is paramagnetic and there is no significant interaction among the spins. The magnetic characterization of 2 is in progress.