Simple Synthesis of Conjugated Polymers Enabled via Pyrrolo[3,2-b]pyrroles

Abstract

Accessing conjugated polymers suitable for applications ranging from organic photovoltaics to bioelectronics through simple synthetic protocols is desirable for the conjugated polymer community, as many polymer systems that meet device performance metrics require arduous synthetic protocols. To simplify and minimize monomer and polymer synthetic steps, a dibrominated dihydropyrrolopyrrole was synthesized in air using a single synthetic step and did not require column chromatography for purification. Subsequently, the first example of an electron-rich pyrrolopyrrole monomer being polymerized is accomplished via direct arylation polymerization using a dioxythiophene comonomer to access an alternating copolymer in a total of three synthetic steps. The resulting copolymer exhibits absorbance in the high-energy portion of the visible spectrum in solution and the solid state, a relatively low onset of oxidation (∼0.6 V vs Ag/AgCl), and yellow-to-black electrochromism. Finally, the synthetic complexity is calculated, and the pyrrolopyrrole-co-dioxythiophene polymer is less synthetically complex when compared to many conjugated polymers that find applicability in organic photovoltaics and electrochromism. These findings demonstrate the viability of incorporating dihydropyrrolopyrroles into the repeat unit structure of conjugated polymers via metal-catalyzed cross-coupling reactions and highlight their potential to offer a synthetically simple alternative to current state-of-the-art conjugated polymers.