Cascade C−H Activation−Annulation Polymerization toward Fluorescent Polycyclic Heteroaromatic Polyelectrolytes with Multiple Functionalities

Abstract

Fluorescent main-chain charged polyelectrolytes (MCCPs) have emerged as a highly attractive class of multifunctional materials. However, their structural diversity remains severely limited by synthetic challenges. Herein, we report a cascade C−H activation−annulation polymerization (CAAP) strategy that can in situ generate MCCPs bearing multisubstituted N-doped cationic benzo[c,d]fluoranthene units via successive C−C/C−N formation in a straightforward manner. The CAAP reactions of readily available 2-arylbenzimidazoles and internal alkynes proceed efficiently under mild conditions, producing a series of high-molecular-weight fluorescent MCCPs (absolute Mw up to 174,300) in high yields of up to 99.2%. Benefiting from the unique structures, the obtained MCCPs show excellent solution processability and film-forming ability along with readily tunable aggregate-state fluorescence through variations in the surrounding substituents and counterion types. These properties enable them to serve as efficient energy donors for Förster resonance energy transfer, and their thin films can be processed into fluorescent photopatterns. Moreover, the fluorescent conjugated MCCPs exhibit efficient reactive oxygen species generation capability, enabling light-enhanced antimicrobial activity through the photodynamic effect, particularly against Gram-negative bacteria.