Regioregular polythiophene with pendant phenoxyl radicals: A new high-spinorganic polymer

Poly[3-(3',5'-di-tert-butyl-4'-acetoxyphenyl)thiophene] (la) was regioselec tively synthesized via simple oxidative polymerization of 3-(3',5'-di-tert- butyl-4'-acetoxyphenyl)thiophene (2a) with ferric chloride. Head-to-tail co ntent of la with a molecular weight of >10(4) reached 96% by modulating bot h the polymerization conditions and the purification procedure of the polym er. Visible absorption and fluorescence maxima were bathochromically shifte d for both la and poly[3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)thiophene] ( Ib), which suggests an extended pi -conjugation, i.e., a regioregular struc ture. Redox of the phenolate and of the thiophene residue of Ib was observe d reversibly and independently under alkaline conditions. The polyphenoxyl 1 derived from the oxidation of Ib showed an electrical conductivity of 10( -5) S cm(-1). The polyradical 1 satisfies both an alternant but non-Kekule- type pi -conjugation and ferromagnetic connectivity of the unpaired electro ns of the pendant phenoxyls. 1 with a spin concentration of 0.3 spin/unit d isplayed a spin quantum number (S) value of 2/2 to 3/2, indicating a high-s pin ground state and an intramolecular ferromagnetic spin coupling through the polythiophene backbone.