A Chain‐Growth Mechanism for Conjugated Polymer Synthesis Facilitated by Dinuclear Complexes with Redox‐Active Ligands

Abstract

Conjugated polymers are widely used in energy conversion and sensor applications, but their synthesis relies on imprecise step-growth or narrowscope chain-growth methods, typically based on transition metal (TM)-catalyzed cross-coupling. Here we report that a dinickel complex with a redox-active naphthyridine diimine ligand accesses new chain-growth mechanistic manifolds for both donor and acceptor conjugated polymers, represented by poly(3-hexylthiophene), poly(2,3-bis(2-ethylhexyl)thienopyrazine), and poly(2-(2-octyldodecyl)benzotriazole). For the latter, our method is particularly effective: we achieve high degrees of polymerization (DP) (> 100) with moderate dispersities (Đ) of � 1.4. Mechanistic analysis supports a radical/radical anion chain-growth mechanism with organometallic intermediates instead of TM-catalyzed crosscouplings. Hence, our work develops new mechanisms for conjugated polymer synthesis and furnishes insights about the elementary reactivity of dinuclear complexes.

Influence of Metal Identity and Complex Nuclearity in Kumada Cross-Coupling Polymerizations with a Pyridine Diimine-Based Ligand Scaffold

“…Alternatively, complexes with multiple metal centers can unlock new forms of reactivity and effectively expand the "toolbox" for chemical transformations�as evidenced by examples in both synthetic and biological systems. 9−12 Based on the findings from our previous work, 16 we sought a catalyst scaffold that (1) had a redox-active ligand, (2) placed the metals in proximity of each other, (3) formed complexes with multiple different first-row metals, and (4) could be readily compared to mononuclear analogs. We selected the bis(pyridine diimine) scaffold pioneered in the Tomson group because it fits these criteria and allowed us to investigate both nickel and iron complexes.…”

Correction to “Light Directs Monomer Coordination in Catalyst-Free Grignard Photopolymerization”

“…The g-value of the chemically reduced P1 radical anion is 2.0035, and that of the reaction mixture is 2.0033, both of which are in agreement with the values for a dimer radical anion from a report by King and Zhukhovitskiy published after our original article. 1 The caption of Figure 2 has been corrected to reflect the revised procedure and data.…”

“…Additionally, the gvalue we observed for doped P1 likely corresponds to trace metal-centered radical, not an organic radical anion. 1 We have since found that our original conditions for polymer reduction with sodium napththalenide did not sufficiently reduce P1. Instead, excess Na metal does reduce P1, which we confirmed with UV−vis absorption and spectroelectrochemistry (Figures S24 and S25, respectively, in the revised Supporting Information presented here).…”

“…However, further analysis of our data (by the expanded research group listed as authors here) revealed that the excited-state lifetime reported is incorrect; it represents the lifetime of the neutral polymer, not a radical anion. Additionally, the g -value we observed for doped P1 likely corresponds to trace metal-centered radical, not an organic radical anion …”

“…Based on the instability of reduced P1 in air, greater care was taken to exclude oxygen from the samples when they were transferred from the glovebox to the instrument, which allowed detection of the radical anion of interest. The g -value of the chemically reduced P1 radical anion is 2.0035, and that of the reaction mixture is 2.0033, both of which are in agreement with the values for a dimer radical anion from a report by King and Zhukhovitskiy published after our original article . The caption of Figure has been corrected to reflect the revised procedure and data.…”