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.

Polymerization of Primary Amines with Sulfur Monochloride to Yield Red Polymers with a Conjugated SN Backbone

“…17−25 Unfortunately, its applications are limited due to its unstable nature that leads to degradation in water or under atmospheric conditions to give a gray powder. 2,3,12,17,26,27 Although a large diversity of small organic compounds containing sulfur−nitrogen bonds have been studied for their biological activities 4,28−48 and synthesis of transition-metal complexes, 49−52 surprisingly few polymers possess nitrogen−sulfur bonds along the backbone. 30,53,54 We recently reported the synthesis of polysulfenamides, polydiaminosulfides, and polydiaminodisulfides, but these polymers possess sp 3 hybridized carbon atoms along their backbones that interrupt conjugation.…”

“…Polythiazyl (SN) x was first synthesized in 1906 and contains alternating sulfur and nitrogen atoms along its backbone (Figure ). − It has many interesting properties such as being one of only two examples of a synthetic polymer that is metallic at room temperature under atmospheric pressure and in the absence of doping. − This polymer is also superconducting with a critical temperature of 0.3 K. − Unfortunately, its straightforward composition does not lead to simple methods to alter its structure or properties, most research has described doping with different chemicals. − This polymer has been heavily investigated since its discovery, and different methods to synthesize it and its derivatives have been developed as well as numerous potential applications that take advantage of its electrical conductivity through the alternating sulfur–nitrogen bonds. − Unfortunately, its applications are limited due to its unstable nature that leads to degradation in water or under atmospheric conditions to give a gray powder. ,,,,, Although a large diversity of small organic compounds containing sulfur–nitrogen bonds have been studied for their biological activities ,− and synthesis of transition-metal complexes, − surprisingly few polymers possess nitrogen–sulfur bonds along the backbone. ,, We recently reported the synthesis of polysulfenamides, polydiaminosulfides, and polydiaminodisulfides, but these polymers possess sp 3 hybridized carbon atoms along their backbones that interrupt conjugation. ,,,…”