Indacenodithiophene Homopolymers via Direct Arylation: Direct Polycondensation versus Polymer Analogous Reaction Pathways

Open-flask, ambient temperature direct arylation synthesis of mixed ionic-electronic conductors

Conjugated polymers are widely studied for application areas ranging from energy technology to wearable electronics and bioelectronics. To develop a truly sustainable technology, environmentally benign synthesis is essential. Here, the open-flask synthesis of a multitude of conjugated polymers at room temperature by ambient direct arylation polymerization (ADAP) is demonstrated. The batch synthesis of over 100 grams of polymer in a green solvent and continuous droplet flow synthesis without any solid support is described. Polymers prepared by ADAP are characterized by improved structural order compared to materials prepared by other methods. Hence, organic electrochemical transistors (OECTs) feature beyond state-of-the-art electrical properties, i.e., an OECT hole mobility μ as high as 6 cm2 V-1 s-1, a volumetric capacitance C* over 200 F cm-3, and thus a figure of merit [μC*] exceeding 1100 F cm-1 V-1 s-1. Thus, ADAP paves the way for the benign and large-scale production of high-performance conjugated polymers.

Rational Design of New Conjugated Polymers with Main Chain Chirality for Efficient Optoelectronic Devices: Carbo[6]Helicene and Indacenodithiophene Copolymers as Model Compounds

The unique properties of conjugated polymers (CPs) in various optoelectronic applications are mainly attributed to their different self-assembly processes and superstructures. Various methods are utilized to tune and control CP structure and properties with less attention paid to the use of chirality. CPs with main chain chirality are rare and their microscopic and macroscopic properties are still unknown. In this work, the first experimental results are provided along these lines by synthesizing a series of racemic and enantiopure CPs containing statistical and alternating carbo[6]helicene and indacenodithiophene moieties and evaluating their microscopic (optical, energy levels) and macroscopic properties (hole mobilities, photovoltaic performance). It is demonstrated that a small statistical insertion of either the racemic or enantiopure helicene into the polymer backbone finely tunes the microscopic and macroscopic properties as a function of the statistical content. The microscopic properties of the enantiopure versus the racemic polymers with the same helicene loading remain similar. On the contrary, the macroscopic properties, and more interestingly those between the two enantiomeric forms, are altered as a function of the statistical content. Once incorporated into a solar cell device, these chiral CPs display better performance in their enantiopure versus racemic forms.

Tunable Regioselectivity in C-H-Activated Direct Arylation Reactions of Dithieno[3,2-b:2',3'-d]pyrroles

In this study, regioselectively controlled direct arylation of dithieno[3,2-b:2,3'-d]pyrroles (DTPs) is reported. By carefully selecting the catalytic system, Pd source, ligand, and additives, we achieved either selective N-arylation or unprecedented β-arylation and β,β'-diarylation of the DTP core through C-H activation when reacting unsubstituted H-DTP with 9-anthracenyl halides. For N-substituted DTPs, we obtained regioselective carboxylate-assisted arylation of the α-position(s). Consequently, depending on the catalytic system and substitution at the DTP nitrogen, we successfully synthesized novel regioselectively substituted DTPs, including N-aryl, rarely reported β-aryl, β,β'-diaryl, α-aryl, and α,α'-diaryl scaffolds. These compounds can be straightforwardly prepared and further functionalized for applications as organic electronic materials.

Synthesis of Conjugated Polymers via Transition Metal Catalysed C-H Bond Activation

Transition metal catalysed C-H bond activation chemistry has emerged as an exciting and promising approach in organic synthesis. This allows us to synthesize a wider range of functional molecules and conjugated polymers in a more convenient and more atom economical way. The formation of C-C bonds in the construction of pi-conjugated systems, particularly for conjugated polymers, has benefited much from the advances in C-H bond activation chemistry. Compared to conventional transition-metal catalysed cross-coupling polymerization such as Suzuki and Stille cross-coupling, pre-functionalization of aromatic monomers, such as halogenation, borylation and stannylation, is no longer required for direct arylation polymerization (DArP), which involve C-H/C-X cross-coupling, and oxidative direct arylation polymerization (Ox-DArP), which involves C-H/C-H cross-coupling protocols driven by the activation of monomers' C(sp² )-H bonds. Furthermore, poly(annulation) via C-H bond activation chemistry leads to the formation of unique pi-conjugated moieties as part of the polymeric backbone. This review thus summarises advances to date in the synthesis of conjugated polymers utilizing transition metal catalysed C-H bond activation chemistry. A variety of conjugated polymers via DArP including poly(thiophene), thieno[3,4-c]pyrrole-4,6-dione)-containing, fluorenyl-containing, benzothiadiazole-containing and diketopyrrolopyrrole-containing copolymers, were summarized. Conjugated polymers obtained through Ox-DArP were outlined and compared. Furthermore, poly(annulation) using transition metal catalysed C-H bond activation chemistry was also reviewed. In the last part of this review, difficulties and perspective to make use of transition metal catalysed C-H activation polymerization to prepare conjugated polymers were discussed and commented.

Step-Economical Synthesis of Conjugated Polymer Materials Composed of Three Components: Donor, Acceptor, and π Units

Conjugated polymers have immense potential for their use as semiconducting materials in organic optoelectronic devices. The improvement of synthetic methods for conjugated polymers is important for the practical application of conjugated polymers. For mass production, synthetic methods must be developed by considering the concerns regarding cost and environment. Reduction in the number of synthetic steps is an efficient approach to address these concerns. The utilization of direct CH functionalization is a reasonable strategy in monomer and polymer syntheses, because the prefunctionalization steps for CC bond formation can be eliminated. This review summarizes the recent developments in the efficient syntheses of conjugated polymers as well as their monomers via direct arylation (CH/CX coupling) and cross-dehydrogenative coupling (CH/CH coupling) reactions.

Approaches for improving the sustainability of conjugated polymer synthesis using direct arylation polymerization (DArP)

Emerging strategies to enhance the sustainability of Direct Arylation Polymerization (DArP) are discussed, illustrating the great potential of this method.