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 narrow-scope 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 cross-couplings. Hence, our work develops new mechanisms for conjugated polymer synthesis and furnishes insights about the elementary reactivity of dinuclear complexes.