Photo-Induced Ruthenium-Catalyzed C-H Arylation Polymerization at Ambient Temperature

Transition metal-catalyzed C-H arylation polymerization (CHAP) is an attractive tool for constructing π-conjugated polymers in a sustainable manner. However, the existing methods primarily rely on palladium catalysis, which usually entails harsh reaction conditions and branching/cross-linking. Here we report the first example of an ambient-temperature ruthenium-catalyzed C-H arylation polymerization induced by visible light irradiation. The present polymerization can produce various meta- and para-linked polymers in excellent yields with high molecular weights. The remarkable feature of our mild reaction platform is represented by high chemoselectivity, leading to polymers that are otherwise inaccessible under conventional reaction conditions at high temperatures.

Thienoisoindigo-Based Conjugated Polymers Synthesized by Direct Arylation Polycondensation

A series of thienoisoindigo (TIG)-based conjugated polymers (CPs) with high molecular weights are synthesized by direct arylation polycondensation (DArP) by using TIG derivatives as CBr monomer and multi-halogenated thiophene derivatives, i.e., (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT), (E)-1,2-bis(3,4-dichlorothien-2-yl)ethene (4ClTVT), 3,3',4,4'-tetrafluoro-2,2'-bithiophene (4FBT), and 3,3',4,4'-tetrachloro-2,2'-bithiophene (4ClBT), as CH monomers. Density functional theory (DFT) calculations reveal the high selectivity between α-CH bonds in 4FTVT, 4ClTVT, 4FBT, and 4ClBT and β-CH bonds in TIG CBr monomer. All four resulting CPs exhibit low optical bandgaps of ca. 1.20 eV and ambipolar transport characteristics with both electron and hole mobility above 0.1 cm2  V-1  s-1 as elaborated with organic thin-film transistors (OTFTs). The polymer TIG-4FTVT delivers the best device performance. With this polymer, n-channel OTFTs with electron mobility up to 1.67 cm2  V-1  s-1 and p-channel OTFTs with hole mobility up to 0.62 cm2  V-1  s-1 are fabricated by modifying source/drain electrodes with polyethylenimine ethoxylated (PEIE) and MoO3 , respectively, to selectively inject electrons and holes.

Nonstoichiometric Direct Arylation Polymerization of Octafluorobiphenyl with 2,7-Diiodofluorene for Regulating CH Terminals of π-Conjugated Polymer

Nonstoichiometric direct arylation polycondensation of 2,2',3,3',5,5',6,6'-octafluorobiphenyl with excess of 2,7-diiodo-9,9-dioctyl-9H-fluorene is demonstrated. Pd/Ag dual-catalyst system under water/2-methyltetrahydrofuran biphasic conditions enables direct arylation under mild conditions and promotes the intramolecular transfer of a Pd catalyst walking through the fluorene moiety. The nonstoichiometric direct arylation polycondensation under the optimized reaction conditions produces the corresponding π-conjugated polymer with a high molecular weight and terminal octafluorobiphenyl units at both ends.

Synthesis of Organic Optoelectronic Materials Using Direct C-H Functionalization

Small molecules and polymers with conjugated structures can be used as organic optoelectronic materials. These molecules have conventionally been synthesized by cross-coupling reactions; however, in recent years, direct functionalization of C-H bonds has been used to synthesize organic optoelectronic materials. Representative reactions include direct arylation reactions (C-H/C-X couplings, with X being halogen or pseudo-halogen) and cross-dehydrogenative coupling (C-H/C-H cross-coupling) reactions. Although these reactions are convenient for short-step synthesis, they require regioselectivity in the C-H bonds and suppression of undesired homo-coupling side reactions. This review introduces examples of the synthesis of organic optoelectronic materials using two types of direct C-H functionalization reactions. In addition, we summarize our recent activities in the development of direct C-H functionalization reactions using fluorobenzenes as substrates. This review covers the reaction mechanism and material properties of the resulting products.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

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.

Dehalogenative or Deprotonative? The Preparation Pathway to the Organometallic Monomer for Transition-Metal-Catalyzed Catalyst-Transfer-Type Polymerization of Thiophene Derivatives

Due to a wide range of applications in electronic materials, polythiophenes attract considerable attention in organic and polymer syntheses as well as in materials science. For the purpose of developing the practical synthetic protocol, this review focuses on the deprotonative pathway in the preparation of thiophene organometallic monomer, which was shown to be effective employing 2-halo-3-substituted thiophene as a monomer precursor. The thus metallated thiophene monomer was shown to undergo polymerization by nickel(II) complex catalysis, with which highly regioregular head-to-tail (HT)-type polythiophenes were obtained with controlled molecular weight and molecular weight distribution. Several polythiophene derivatives with modified thiophene-ring and side-chain structures were shown to be designed in order to achieve the designed functionality as materials.

Nanoarchitectonics of Nanoporous Carbon Materials in Supercapacitors Applications

High surface area and large pore volume carbon materials having hierarchical nanoporous structure are required in high performance supercapacitors. Such nanoporous carbon materials can be fabricated from organic precursors with high carbon content, such as synthetic biomass or agricultural wastes containing cellulose, hemicellulose, and lignin. Using recently developed unique concept of materials nanoarchitectonics, high performance porous carbons with controllable surface area, pore size distribution, and hierarchy in nanoporous structure can be fabricated. In this review, we will overview the recent trends and advancements on the synthetic methods for the production of hierarchical porous carbons with one- to three-dimensional network structure with superior performance in supercapacitors applications. We highlight the promising scope of accessing nanoporous graphitic carbon materials from: (i) direct conversion of single crystalline self-assembled fullerene nanomaterials and metal organic frameworks, (ii) hard- and soft-templating routes, and (iii) the direct carbonization and/or activation of biomass or agricultural wastes as non-templating routes. We discuss the appealing points of the different synthetic carbon sources and natural precursor raw-materials derived nanoporous carbon materials in supercapacitors applications.

Semifluorinated, kinked polyarylenes via direct arylation polycondensation

The T_g of semifluorinated polyarylenes made via DAP is varied between 35–195 °C depending on side chain, but solubilities are much less side chain dependent. This is explained by interactions between alkoxyphenyl and tetrafluorobenzene units.

Significant Difference in Semiconducting Properties of Isomeric All-Acceptor Polymers Synthesized via Direct Arylation Polycondensation

The direct arylation polycondensation (DArP) appeared as an efficient method for producing semiconducting polymers but often requires acceptor monomers with orienting or activating groups for the reactive carbon-hydrogen (C-H) bonds, which limits the choice of acceptor units. In this study, we describe a DArP for producing high-molecular-weight all-acceptor polymers composed of the acceptor monomers without any orienting or activating groups via a modified method using Pd/Cu co-catalysts. We thus obtained two isomeric all-acceptor polymers, P1 and P2, which have the same backbone and side-chains but different positions of the nitrogen atoms in the thiazole units. This subtle change significantly influences their optoelectronic, molecular packing, and charge-transport properties. P2 with a greater backbone torsion has favorable edge-on orientations and a high electron mobility μ_e of 2.55 cm²  V^-1  s^-1 . Moreover, P2-based transistors show an excellent shelf-storage stability in air even after the storage for 1 month.

Self-assembly as a key player for materials nanoarchitectonics

The development of science and technology of advanced materials using nanoscale units can be conducted by a novel concept involving combination of nanotechnology methodology with various research disciplines, especially supramolecular chemistry. The novel concept is called 'nanoarchitectonics' where self-assembly processes are crucial in many cases involving a wide range of component materials. This review of self-assembly processes re-examines recent progress in materials nanoarchitectonics. It is composed of three main sections: (1) the first short section describes typical examples of self-assembly research to outline the matters discussed in this review; (2) the second section summarizes self-assemblies at interfaces from general viewpoints; and (3) the final section is focused on self-assembly processes at interfaces. The examples presented demonstrate the strikingly wide range of possibilities and future potential of self-assembly processes and their important contribution to materials nanoarchitectonics. The research examples described in this review cover variously structured objects including molecular machines, molecular receptors, molecular pliers, molecular rotors, nanoparticles, nanosheets, nanotubes, nanowires, nanoflakes, nanocubes, nanodisks, nanoring, block copolymers, hyperbranched polymers, supramolecular polymers, supramolecular gels, liquid crystals, Langmuir monolayers, Langmuir-Blodgett films, self-assembled monolayers, thin films, layer-by-layer structures, breath figure motif structures, two-dimensional molecular patterns, fullerene crystals, metal-organic frameworks, coordination polymers, coordination capsules, porous carbon spheres, mesoporous materials, polynuclear catalysts, DNA origamis, transmembrane channels, peptide conjugates, and vesicles, as well as functional materials for sensing, surface-enhanced Raman spectroscopy, photovoltaics, charge transport, excitation energy transfer, light-harvesting, photocatalysts, field effect transistors, logic gates, organic semiconductors, thin-film-based devices, drug delivery, cell culture, supramolecular differentiation, molecular recognition, molecular tuning, and hand-operating (hand-operated) nanotechnology.

Synthesis of conjugated polymers via direct C–H/C–Cl coupling reactions using a Pd/Cu binary catalytic system

Selective C–H/C–Br coupling and polycondensation with C–H/C–Cl coupling afforded conjugated polymers in a short synthetic step.