Versatile Protocol of C–H Direct Arylation Coupling Enables the Synthesis of Narrow-Band-Gap Polymers Containing Benzobisthiadiazole or Thiadiazoloquinoxaline Units

Abstract

π-Conjugated narrow-band-gap polymers (NBPs), characterized by their intrinsically electrical, optical, spintronic, and mechanical properties, have attracted broad interest since the development of the first generation of conducting polymers. The current synthesis of NBPs, nevertheless, largely relies on traditional Suzuki or Stille coupling, which often requires preactivation of aryl C–H bonds involving highly flammable organometallic reagents, such as butyl lithium and highly toxic stannyl agents, which are often involved in Stille coupling. Here, we report the synthesis of a series of NBPs consisting of benzobisthiadiazole (BBT) or thiadiazoloquinoxaline (BBQ) units via a “greener chemistry” of direct arylation polymerization (DArP). Free of toxic organotin compounds or extra borylation, our DArP protocol, in the presence of a Pd2(dba)3 catalyst, phosphine ligands, and carboxylic acid additives enables efficient polymerization with monomers of BBT or BBQ with comonomers containing opposite reactive sites. Consequently, a series of donor–acceptor (D–A) or acceptor–acceptor (A–A) alternating copolymers have been synthesized in decent yields and with minimal defects. These polymers with narrow optical band gaps below 1.3 eV can achieve near-infrared (NIR) absorption and fluorescence emission, as well as stable electrochemical performance. Moreover, the scope of open-shell BBT- and BBQ-based polymers has been broadened, including a series of spin density and spin–orbit coupling, as well as tunable electron, hole, or ambipolar charge transport behavior.

Accessing Poly(DA-ran-Dπ) Ternary Copolymers via Direct C–H Arylation for Ultrahigh Photocatalytic Hydrogen Production

“…In recent years, the boron- and tin-free DArP (i.e., the straightforward C–H/C–Br coupling) has emerged as a green and atom-economical alternative to the traditional Suzuki and Stille C–M/C–Br (M = B and Sn) couplings. − Here, the Pd-catalyzed DArP ,, (Scheme ) among DBTSO 2 , EDOT, and 1,4-dibromobenzene (DBB) led to the formation of five target LCPs EDBz-0 , EDBz-25 , EDBz-50 , EDBz-75 , and EBz-100 , wherein 0, 25, 50, 75, and 100 represent the percentages of phenyl units involved. By varying the feed ratios of DBB, the ternary LCPs incorporating different contents of the phenyl π-spacer and DBTSO 2 were facilely obtained (Scheme ).…”

An acceptor-quantity modulation strategy for high-performance ambipolar semiconducting polymers: from a dual-acceptor to a quad-acceptor backbone

“…21,29–31 However, the huge synthetic challenges of unstable distannyl monomers and the generation of toxic organotin by-products make Stille-coupling polymerization not an ideal polymerization method. 32–34 As for Suzuki-coupling polymerization, reactions with chlorinated compounds (especially those molecules with huge steric hindrance) or thiophene-based heterocyclic boric acids are always difficult to carry out. 35–37 Recently, direct arylation polymerization (DArP) that can construct semiconducting polymers by using the direct activation of C–H bonds has appeared as an atom-economical protocol.…”