Stable Radical Functionalized Polythiophenes: Synthesis and Characterization

Abstract: Materials with multiple properties have garnered attention due to their potential applications in various fields, including photovoltaic cells and energy storage. The incorporation of stable radicals within polymer backbones yields polymers with high spin density. This review reports the synthesis and characterization of new materials that combine the properties of stable radicals and conducting materials. Polythiophenes exhibit excellent stability in both states, a reversible electrochemical response, and are highly conductive. The presence of the radical on the polythiophene backbone provides a great opportunity to add an extra negative or positive charge, which has a significant effect on the optical, magnetic, and electrical properties of the conjugated polymers. Nitroxides, phenoxides, and verdazyl radicals are very stable, facilitating incorporation into the polythiophene backbone. The radical-functionalized polythiophene can be synthesized directly via either electrochemical or chemical oxidation of the radical-oligothiophene precursor or through a crosscoupling reaction. Nitroxides, phenoxides, and verdazyl radicals attached to polythiophenes via different synthetic routes, along with their characterizations, are discussed in this review. The interactions between the spin and the π-system are also explained. Additionally, challenges and synthetic approaches to prepare new stable organic polyradicals for the development of organic batteries are also explored in this review. Finally, perspectives for designing magnetic materials based on metallopolyradicals are presented.