Poly[(3,5-di-tert-butyl-4-hydroxyphenyl)acetylene] and Its Polyradical Derivative

(3,5-Di-tert-butyl-4-hydroxyphenyl)acetylene (8) was synthesized and polymerized with WCl₆ and MoCl₅, giving a novel and solvent-soluble conjugated polymer, poly[(3,5-di-tert-butyl-4-hydroxyphenyl)-acetylene] (3). Visible absorption of the polymer indicated a fairly long π-conjugated system along the main chain. The polymer yielded its polyanion 10 and polyradical derivative 4 after the treatment of its solution with an alkali and oxidizing reagent, respectively. The polyradical 4 was surprisingly stable, and spin concentration was increased up to 2.3 × 10²³ spins/molar (hydroxyphenyl)acetylene residue. ESR spectra of the polyradical 4 in solution suggested that the formed upaired electrons were delocalized along the polyacetylene main chain. 4 was also very stable even in solid state. Spin-exchange interaction observed in 4 strongly depended on its spin concentration. Antiferromagnetic interaction between the upaired electrons was suggested from the temperature dependency of the ESR signal intensity.