Poly(1,2-phenylenevinylene) Ferromagnetically 3,5-Bearing Phenoxyl Radicals

A π-conjugated but non-Kekulé- and nondisjoint-type molecule, poly(1,2-phenylenevinylene) 3,5-disubstituted with pendant phenoxyl radicals ( 1a ), was designed as a new high-spin organic polymer and synthesized by the head-to-tail coupling polymerization of 2-bromo-3,5-bis(3,5-di- tert -butyl-4-aceotoxyphenyl)styrene ( 3 ) using a palladium catalyst. The corresponding high-spin dimer model compound bearing four phenoxyl radicals ( 2a ) was also synthesized. The stepwise radical formation in 1 and 2 was electrochemically studied. The ESR signal at Δ M s = ±2 indicated a triplet ground state for 1 and 2 . However, the SQUID data revealed that the spin concentration and the average spin quantum number of 1a and 2a remained at ca. 0.5 spin/phenol unit and 2/2, respectively. A degradation at the vinylene bridge was suggested after the radical generation.