Palladium-Catalyzed Chain-Growth Polycondensation of AB-type Monomers: High Catalyst Turnover and Polymerization Rates

AB- Versus AA+BB-Suzuki Polycondensation: A Palladium/Tris(tert-butyl)phosphine Catalyst Can Outperform Conventional Catalysts

A Pd/Pt-Bu₃ catalyst having bulky, electron-rich ligands significantly outperforms conventional "step-growth catalysts" Pd(PPh₃ )₄ and Pd(Po-Tol₃ )₃ in the Suzuki polycondensation of the AB-type arylene-based monomers, such as some of the substituted fluorenes, carbazoles, and phenylenes. In the AA+BB polycondensation, Pd/Pt-Bu₃ also performs better under homogeneous reaction conditions, in combination with the organic base Et₄ NOH. The superior performance of Pd/Pt-Bu₃ is discussed in terms of its higher reactivity in the oxidative addition step and inherent advantages of the intramolecular catalyst transfer, which is a key step joining catalytic cycles of the AB-polycondensation. These findings are applied to the synthesis of a carbazole-based copolymer designed for the use as a hole conductor in solution-processed organic light-emitting diodes.

A General and Air-tolerant Strategy to Conjugated Polymers within Seconds under Palladium(I) Dimer Catalysis

While current M0 /MII based polymerization strategies largely focus on fine-tuning the catalyst, reagents and conditions for each and every monomer, this report discloses a single method that allows access to a variety of different conjugated polymers within seconds at room temperature. Key to this privileged reactivity is an air- and moisture stable dinuclear PdI catalyst. The method is operationally simple, robust and tolerant to air.

Controlled Pd(0)/Ad3P-Catalyzed Suzuki Cross-Coupling Polymerization of AB-Type Monomers with Ad3P-Coordinated Acetanilide-Based Palladacycle Complex as Initiator

Controlled Pd(0)-catalyzed Suzuki cross-coupling polymerizations of AB-type monomers with tris(1-adamantyl)phosphine (Ad₃P) as the ligand was described. Ad₃P-coordinated acetanilide-based palladacycle complex (1) was demonstrated to be an efficient initiator for controlled Suzuki cross-coupling polymerization, affording polymers with narrow Đs and well-controlled end groups. Our study provided an efficient ligand and an efficient initiator for controlled Suzuki cross-coupling polymerizations.

Impact of Precatalyst Activation on Suzuki-Miyaura Catalyst-Transfer Polymerizations: New Mechanistic Scenarios for Pre-transmetalation Events

The relevance of L_nPdX₂ precatalyst activation on the Suzuki-Miyaura reaction course was investigated in the case of catalyst-transfer polymerizations. A catalytic study, backed up by theoretical calculations, allowed to ascertain the coexistence of a neutral and an anionic mechanistic pathways in the precatalyst activation, in which the bulky ^tBu₃P external ligand plays a crucial role. The fine-tuning of the catalytic conditions can steer the activation step toward the anionic pathway, leading to the full control over the polymerization course. While providing insights and perspectives into the catalyst-transfer polymerizations, these results uncover unexplored scenarios for the pre-transmetalation events of Suzuki-Miyaura reactions contributing to its full understanding.

Facile synthesis of oligo(3-hexylthiophene)s conductive wires with charge-transfer functions

A series of fully conjugated oligo(3-hexylthiophene)s bearing different starting- and end-groups have been synthesized by means of externally initiated Kumada catalyst-transfer polymerization (KCTP) and Grignard Metathesis Polymerization (GRIM).

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures

This review details synthetic strategies leading to structurally-defined electrochemically and (photo)redox-active polymer architectures,e.g.block, graft and end functionalized (co)polymers.

Copolymerization of zinc-activated isoindigo- and naphthalene-diimide based monomers: an efficient route to low bandgap π-conjugated random copolymers with tunable properties

We report preparation of isoindigo-based copolymers for optoelectronic applications.

Transition-metal-free controlled polymerization of 2-polyfluorophenyl-5-trimethylsilylthiophenes: the substituent impact of fluorine

A transition-metal-free polymerization of a series of 2-polyfluorophenyl-5-trimethylsilylthiophenes promoted by fluoride anions is reported.

A fast controlled synthesis of poly(p-phenyleneethynylene)s under transition-metal-free conditions

A transition-metal-free polymerization of an AB-type monomer for the synthesis of well-defined poly(p-phenyleneethynylene)s is described.

Palladium-Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

Oxidation reactions by molecular oxygen (O2 ) over palladium (Pd)-based nanomaterials are a series of processes crucial to the synthesis of fine chemicals. In the past decades, investigations of related catalytic materials have mainly been focused on the synthesis of Pd-based nanomaterials from the angle of tailoring their surface structures, compositions and supporting materials, in efforts to improve their activities in organic reactions. From the perspective of rational materials design, it is imperative to address the fundamental issues associated with catalyst performance, one of which should be oxygen activation by Pd-based nanomaterials. Here, the fundamentals that account for the transformation from O2 to reactive oxygen species over Pd, with a focus on singlet O2 and its analogue, are introduced. Methods for detecting and differentiating species are also presented to facilitate future fundamental research. Key factors for tuning the oxygen activation efficiencies of catalytic materials are then outlined, and recent developments in Pd-catalyzed oxygen-related organic reactions are summarized in alignment with each key factor. To close, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields.

Influence of Semiconductor Thickness and Molecular Weight on the Charge Transport of a Naphthalenediimide-Based Copolymer in Thin-Film Transistors

The N-type semiconducting polymer, P(NDI2OD-T2), with different molecular weights (MW=23, 72, and 250 kg/mol) was used for the fabrication of field-effect transistors (FETs) with different semiconductor layer thicknesses. FETs with semiconductor layer thicknesses from ∼15 to 50 nm exhibit similar electron mobilities (μ's) of 0.2-0.45 cm2 V(-1) s(-1). Reduction of the active film thickness led to decreased μ values; however, FETs with ∼2 and ∼5 nm thick P(NDI2OD-T2) films still exhibit substantial μ's of 0.01-0.02 and ∼10(-4) cm2 V(-1) s(-1), respectively. Interestingly, the lowest molecular weight sample (P-23, MW≈23 kg/mol, polydispersity index (PDI)=1.9) exhibited higher μ than the highest molecular weight sample (P-250, MW≈250 kg/mol, PDI=2.3) measured for thicker devices (15-50 nm). This is rather unusual behavior because typically charge carrier mobility increases with MW where improved grain-to-grain connectivity usually enhances transport events. We attribute this result to the high crystallinity of the lowest MW sample, as confirmed by differential scanning calorimetry and X-ray diffraction studies, which may (over)compensate for other effects.

Negishi coupling in the synthesis of advanced electronic, optical, electrochemical, and magnetic materials

Negishi coupling is an efficient and versatile tool for selective C–C bond formation in the synthesis of organic electronic, optical, electrochemical, and magnetic materials.

Kumada catalyst transfer polycondensation for controlled synthesis of polyfluorenes using 1,3-bis(diarylphosphino)propanes as ligands

The moderately hindered catalyst Ni(acac)₂/L2 outperformed other catalysts, affording PF8s with M_n up to 91.1 in a controlled manner.

Intramolecular catalyst transfer polymerisation of conjugated monomers: from lessons learned to future challenges

Eleven years after the first reports on intramolecular catalyst transfer polycondensations, this review aims to critically recap on the fundamental “lessons” that can be learned from the historic literature as well as from the fervid activity that has emerged in the last three years.

Selective and general exhaustive cross-coupling of di-chloroarenes with a deficit of nucleophiles mediated by a Pd–NHC complex

We report the first example of a general, exhaustive Pd-mediated cross-coupling of polychloroarenes in the presence of a deficit of nucleophiles, mediated by the highly active PEPPSI-IPent catalyst.

Pd- and Ni-catalyzed cross-coupling reactions in the synthesis of organic electronic materials

Organic molecules and polymers with extended π-conjugation are appealing as advanced electronic materials, and have already found practical applications in thin-film transistors, light emitting diodes, and chemical sensors. Transition metal (TM)-catalyzed cross-coupling methodologies have evolved over the past four decades into one of the most powerful and versatile methods for C-C bond formation, enabling the construction of a diverse and sophisticated range of π-conjugated oligomers and polymers. In this review, we focus our discussion on recent synthetic developments of several important classes of π-conjugated systems using TM-catalyzed cross-coupling reactions, with a perspective on their utility for organic electronic materials.

Transition-metal-free controlled polymerization of 2-perfluoroaryl-5-trimethylsilylthiophenes

A catalytic amount of fluoride anion promoted the polymerization of 2-pentafluorophenyl-5-trimethylsilylthiophene, providing a high-molecular-weight conjugated polymer in a chain-growth-like manner. The resulting polymer with a controlled molecular weight and a low molecular weight distribution was obtained in a high yield. The mechanism involves a pentacoordinated fluorosilicate as a key intermediate. The active polymerization end also initiated the second polymerization to afford well-defined block copolymers.