Syntheses of Nitronyl Nitroxide and Nitroxide Polyradicals and Their Magnetic Characterization

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 Et 3 N-pyridine in the presence of (PPh3) 2 PdCl 2 - Cul. The spin concentrations were 1.12 × 10 21 - 1.33 × 10 21 spin/g and the number average molecular weights (M n ) 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 × 10 21 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.