Poly(3-phenylgalvinoxylthiophene). A new conjugated polyradical with high spin concentration

3-{4-[(3, 5-Di-tert-butyl-4-acetoxyphenyl)(3,5 -di-tert-butyl-4-oxocyclohexa-2,5-diene-1-ylidene)methyl]phenyl} thiophene (2a) was synthesized and oxidatively polymerized with ferric chloride at low temperature to yield poly(3-{4-[(3, 5-di-tert-butyl-4-acetoxyphenyl)(3,5-di-tert-butyl-4-oxocyclohexa-2,5 -diene-1-ylidene)-methyl]phenyl} thiophene) (1a). Head-to-tail content of 1a with a molecular weight of > 10⁴ reached 92%. This polymer has a quinoid chromophore, and it reversibly showed a dark blue and red brownish color ascribed to an anion and a radical form, respectively. The polyradical 1 was almost quantitatively generated from 1b (a spin concentration of 0.9 spin/galvinoxyl unit), which was persistent at room temperature. The SQUID measurement at low temperature gave a spin quantum number (S) of 1/2 for 1, which indicated a paramagnetic ground state. 1 doped with iodine showed an electrical conductivity of 10^-5 S cm^-1. The polyradical derivatives, 7 and 8, displayed S of 1/2-2/2 and 1/2, respectively, and an electrical conductivity of 10^-4-10^-3 S cm^-1 after doping.