Synthesis of Conjugated Polymers: Comparing the Indophenine Reaction with Traditional Methods

Abstract

Conjugated polymers are an important class of materials whose development underpins many recent advances in organic electronics. Traditionally, these polymers have been synthesized by transition-metal-catalyzed cross-couplings using organometallic reagents (e.g., Stille couplings). Although direct heteroarylation polymerization (DHAP) dispenses with the organometallic intermediates, DHAP is still a metal-catalyzed coupling, requiring both catalyst optimization and purification to remove trace metal contaminants. In contrast, a recent report from our group demonstrated that the indophenine reaction can be used as a metal-free method to prepare conjugated polymers; however, from this initial proof-of-concept study, it was not clear how it compared to other methods of conjugated polymer synthesis. Therefore, in this report, we synthesized the same polymer using three distinctly different approaches: Stille coupling, DHAP, and the indophenine reaction. This allows us to directly compare the three methodologies; we find that each offers distinct trade-offs in terms of atom economy, defects, and molecular weight.