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 c haracterization. Polyradical 1 was obtained by the polycondensation of nitronyl nitroxide substituted 3,5-diethynylbenzene with 1,3-diiodobe nzenes in Et3N-pyridine in the presence of (PPh3)2PdCl2 - Cul. The spi n concentrations were 1.12 x 10(21) - 1.33 x 10(21) spin/g and the num ber average molecular weights (Mn) were 4300 - 4800. Polyradical 2 was obtained by the polymerization of N-tert-butyl-3-ethynyl-5-tert-pheny l nitroxide using a Rh catalyst. The spin concentration of 2 was 2.09 x 10(21) spin/g and Mn 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 interact ion. 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 characterizatio n of 2 is in progress.