Designing Interfaces That Function to Facilitate Charge Injection in Organic Light-Emitting Diodes

Layer-by-layer (LbL) assembly of triarylamine (TAA)-containing polymers has been applied for anode functionalizations in organic light-emitting diodes (OLEDs). Surface work function of the ITO electrodes was significantly altered with the functionalizations, and the values changed depending on electron affinity of the substituents (X) on the TAA units. When the functionalized ITO electrodes were utilized for the conventional TPD/Alq OLED, the multilayers of P1 (X = 4-OMe) and P2 (X = none) were found to promote better energy matching at the ITO/TPD interface to reduce the hole injection barrier. Furthermore, the multilayers having heterodeposited structure of several TAA polymers provided stepped and graded electronic profiles to facilitate hole mobility from ITO to TPD, so that the resulting OLED devices can exhibit appreciably reduced turn-on voltage and higher luminous intensities

Control of Molecular Aggregation Features in Polymer-Dispersed Liquid Crystal Films Utilizing a Boronate-Terminated Self-Assembled Monolayer

Control of Molecular Aggregation Features in Polymer-Dispersed Liquid Crystal Films Utilizing a Boronate-Terminated Self-Assembled Monolaye

Palladium Nanoparticles Captured in Microporous Polymers: A Tailor-Made Catalyst for Heterogeneous Carbon Cross-Coupling Reactions

A new strategy based on polymerization-induced phase separation (PIPS) techniques was proposed for fabricating palladium nanoparticles (PdNPs) captured in a microporous network polymer. Pd(OAc)2 was premixed with a monomer having a poly(amidoamine)-based dendrimer ligand, and subsequently this was thermally polymerized with an excess amount of ethylene glycol dimethacrylate under PIPS conditions. In this system, the formation of PdNPs occurred concurrently with the polymer synthesis in a one-pot process, even with no additional reducing reagent. The resultant microporous polymer was found to have a mesoporosity; the nitrogen sorption analysis gave a specific-surface area of 511 m2 g−1, an average pore diameter of 9.9 nm, and a total pore volume of 1.01 mL g−1. The TEM images of the polymer revealed that the created PdNPs were very small with a diameter of mainly ca. 2.0 nm; the high-resolution images were lattice-resolvable, showing the crystalline nature of the PdNPs (Pd(111) facets). Catalytic performances of the PdNP-containing microporous polymers were investigated for a heterogeneous Suzuki−Miyaura reaction of 4′-bromoacetophenone and phenylboronic acid in water. In the presence of 10−2 molar equiv of the polymer, the reaction efficiently proceeded at 80 °C and gave the desired product, 4-acetylbiphenyl, in >90% yield after 2 h. On the basis of the ICP-AES analysis, the Pd content released into the solution phase was estimated to be only 0.27% of the initial charge. Thereby, this polymer was successfully recovered by simple filtration and reused with only a minimal loss of activity (yield >90% even at the eighth run). When the catalytic reaction was examined with a low amount of the polymer catalyst, the turnover number (TON) reached 8.5 × 104 while maintaining a good yield. Finally, the dendrimer template effect of the polymer catalyst was discussed by referring to the catalytic performances of a control polymer prepared with nonintegrated ligand monomers

Anchoring Effects of Self-Assembled Monolayers for Polymer-Dispersed Liquid Crystal Films

Polymer-dispersed liquid crystal (PDLC) films of 4-cyano-4‘-pentylbiphenyl (5CB) were fabricated between two quartz substrates, the surfaces of which had been modified with the self-assembled monolayers (SAMs) of CH3−(CH2)17−Si(OMe)3 (1), HS−(CH2)10−Si(OEt)3 (2), and NC−(CH2)11−Si(OEt)3 (3). The SAM-modification effects on the molecular aggregation of 5CB were investigated by steady-state and time-resolved fluorescence analysis for the PDLC films. Remarkably, it was found that selective excitation of the interface layer with the substrate surface gave both the monomer and excimer emissions of 5CB in relative intensities, depending on the chemical nature of the SAM surfaces. While the monomer and excimer emissions appeared in comparative intensities in the case of the unmodified quartz surface, the surface modification with the SAM of 1 resulted in a dominant contribution of the excimer emission. By contrast, the monomer emission was much stronger than the excimer emission in the case of the surface modified by the SAM of 2. The surface modification with the SAM of 3 gave a fluorescence spectrum very similar to that in the case of the unmodified surface. Fluorescence decay analysis for the PDLC films revealed that the excimer emission consists of two components with shorter (1.3−1.6 ns) and longer (10−12 ns) lifetimes, whose relative contributions depend on the SAM modifications. The molecular pictures of 5CB depicted from the decay dynamics are in good agreement with those derived from the steady-state fluorescence behavior of the PDLC films. Electrooptic devices based on the PDLC films were constructed by using indium−tin oxide transparent electrodes modified with the SAMs, and it was confirmed that the electrooptic responses again significantly depend on the modifications of the substrate surface. The dependency of the fluorescence and electrooptic behavior on the surface modifications for the PDLC films has been discussed in terms of anchoring effects of the substrate surfaces, which effectively work even in heterogeneous materials such as PDLCs

Critical Effects of Ligand Integration in Creating Palladium-Incorporated Porous Polymer Composites

This Article reports on the ligand integration effect of poly­(amidoamine) (PAMAM) dendrimers working in the solid composite systems, which is significant for stabilizing Pd nanoparticles (PdNPs). To carry forward this research, the fourth generation of PAMAM dendrimer (G4) was modified with polymerizable functions and tied to polymer networks constituting porous composites through the polymerization-induced phase separation (PIPS) strategy. The obtained results indicate that creation of PdNPs is strongly affected by the G4 template, and, consequently, unforeseen critical control of their sizes was definitely performed. Also, the crucial importance from perspective of catalytic applications is strong suppression of Pd leaching for the G4-utilized porous polymer composites (G4-p). This fact means that the catalytic event of G4-p entirely occurs on the polymer support. All of these characteristics are in marked contrast to those of the composite that was fabricated with a nonintegrated, small molecule ligand system. On the basis of the present study, a primary mechanism that describes how Pd and ligand associate mutually during PIPS is proposed, where the Pd reduction and polymer propagation concurrently occurred

Efficient Synthesis of a Highly Selective NPY-5 Receptor Antagonist: A Drug Candidate for the Treatment of Obesity

A concise and practical synthesis of highly selective NPY-5 receptor antagonist 1 is described. The animopyrazine intermediate 3 was synthesized via either monobromination of aminopyrazine or palladium-catalyzed regioselective debromination of dibromopyrazine followed by an efficient Suzuki−Miyaura coupling. For the preparation of the spirolactone piperidine 2, significantly improved yield was achieved by using a combination of n-BuMgCl and n-BuLi. This protocol also dramatically increased the thermal stability of the aryllithium intermediate and eliminated the requirement for costly cryogenic conditions. The union of the spirolactone piperidine 2 and aminopyrazine 3 via a carbonyl group was accomplished using phenyl chloroformate delivering the target molecule in high yield

Enantioselective, Biocatalytic Reduction of 3-Substituted Cyclopentenones: Application to the Asymmetric Synthesis of an hNK-1 Receptor Antagonist

A convergent and enantioselective route to the hNK-1 receptor antagonist (1) is described, which sets all six stereogenic centers with high diastereoselectivity and delivers 1 in only 11 steps and 23% overall yield. The process was enabled by the development of the enantioselective enzymatic reduction of 3-functionalized cyclopentenones and stereospecific Pd-catalyzed etherification coupling of fragments 6 and 7

Practical Synthesis of a HIV Integrase Inhibitor

A practical and efficient synthesis of the potent HIV integrase inhibitor 1 is described. Starting from readily available 3,4-dihydro-2H-pyran, the six-step synthesis features a through process without purification of any of the intermediates until the isolation of crystalline intermediate 7. After deprotection and classical resolution, amine 8 was isolated with excellent enantiopurity. A final amide coupling completed the synthesis of 1 in 7.6% overall yield from DHP. This chromatography-free route is more cost effective and increases the overall yield by nearly 3 times when compared with the original Med Chem synthethic route. This improved chemistry was used successfully to prepare multikilogram quantities of integrase inhibitor 1

Synthesis of a Muscarinic Receptor Antagonist via a Diastereoselective Michael Reaction, Selective Deoxyfluorination and Aromatic Metal−Halogen Exchange Reaction

An efficient synthesis of a structurally unique, novel M3 antagonist 1 is described. Compound 1 is conveniently disconnected retrosynthetically at the amide bond to reveal the acid portion 2 and the amine fragment 3. The synthesis of key intermediate 2 is highlighted by a ZnCl2−MAEP complex 19 catalyzed diastereoselective Michael reaction of dioxolane 7 with 2-cyclopenten-1-one (5) to establish the contiguous quaternary-tertiary chiral centers and a subsequent geminal difluorination of ketone 17 using Deoxofluor in the presence of catalytic BF3·OEt2. The synthesis of the amine moiety 3 is highlighted by the discovery of a novel n-Bu3MgLi magnesium−halogen exchange reaction for selective functionalization of 2,6-dibromopyridine. This new and practical metalation protocol obviated cryogenic conditions and upon quenching with DMF gave 6-bromo-2-formylpyridine (26) in excellent yield. Further transformations afforded the amine fragment 3 via reductive amination with 35, Pd-catalyzed aromatic amination, and deprotection. Finally, the highly convergent synthesis of 1 was accomplished by coupling of the two fragments. This synthesis has been used to prepare multi-kilogram quantities of the bulk drug