Triarylamine-bearing poly(1,4-phenylenevinylene): Facile preparation and its durable aminium polyradical

Poly[2-{bis(4-methoxyphenyl)amino}phenyl-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] 1 was prepared via the Gilch reaction of the p-bis(chloromethyl)benzene monomer, 2-{bis(4-methoxyphenyl)aminophenyl}-α, α′-dichloro-p-xylene. The Gilch reaction facilitated the preparation of the polyphenylenevinylene with a triarylamine pendant group when compared to that via the Heck polycondensation. The molecular weight of the polymer was approximately 4.0 × 10⁵, and it was soluble in common solvents and was reversibly redoxed due to the pendant arylamine moiety. Chemical oxidation of 1 afforded the corresponding aminium polyradical 1⁺ with the half life-time of ca. 2 weeks under ambient conditions. ESR and magnetization measurements of 1⁺ revealed a forbidden multiplet signal and an average spin quantum number (S) of 3/2 at low temperature, respectively. The polyradical 1⁺ was the first example of a high molecular weight, high-spin organic polymer with solvent-solubility and film formability. 2,3-Bis[N,N-bis(4-methoxyphenyl)aminophenyl]stilbene 2 and its aminium diradical 2⁺ were also prepared as the model dimer compounds; 2⁺ was a triplet molecule at low temperature. The effect of the π-conjugated poly(1,4-phenylene-vinylene) backbone on the high-spin alignment was also discussed.