An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2-aryl-pyridines and 2-aryl-sp(2) -nitrogen-atom-containing ...heterocycles with alkynes through rhodium(III)-catalyzed CH activation and annulation under an O2 atmosphere is described. A possible mechanism that involves the chelation-assisted CH activation of the 2-aryl-pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five-membered rhodacycle (I'). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.
A synthetic method for highly substituted pyridinium salts from the multicomponent reaction of vinyl ketones/aldehydes, amines, and alkynes using a rhodium catalyst is demonstrated. The catalytic ...reaction proceeds via an in situ generated imine-assisted RhIII-catalyzed vinylic C–H activation.
Addressing the critical requirement for real-time monitoring of tumor progression in cancer care, this study introduces an innovative wearable platform. This platform employs a thermoplastic ...polyurethane (TPU) film embedded with hafnium oxide nanoparticles (HfO2 NPs) to facilitate dynamic tracking of tumor growth and regression in real time. Significantly, the synthesized HfO2 NPs exhibit promising characteristics as effective sonosensitizers, holding the potential to efficiently eliminate cancer cells through ultrasound irradiation. The TPU-HfO2 film, acting as a dielectric elastomer (DE) strain sensor, undergoes proportional deformation in response to changes in the tumor volume, thereby influencing its electrical impedance. This distinctive behavior empowers the DE strain sensor to continuously and accurately monitor alterations in tumor volume, determining the optimal timing for initiating HfO2 NP treatment, optimizing dosages, and assessing treatment effectiveness. Seamless integration with a wireless system allows instant transmission of detected electrical impedances to a smartphone for real-time data processing and visualization, enabling immediate patient monitoring and timely intervention by remote medical staff. By combining the dynamic tumor monitoring capabilities of the TPU-HfO2 film with the sonosensitizer potential of HfO2 NPs, this approach propels cancer care into the realm of telemedicine, representing a significant advancement in patient treatment.
Three pyridine-carbonitrile–carbazole-based thermally activated delayed fluorescence (TADF) materials with highly sterically congested structures have been synthesized. The donor–acceptor-type TADF ...emitters (26-, 246-, and 35tCzPPC) consist of a 2,6-diphenylpyridine-3,5-dicarbonitrile core (PPC) as the acceptor and a di(t-butyl)carbazole-substituted phenyl group attached to C4 of the PC core as the donor. The molecules show a unique structure containing two consecutive large twisted angles along the donor and acceptor groups. The structure leads to a nearly complete space separation of the highest occupied molecular orbital and lowest unoccupied molecular orbital, a small ΔE ST value, and excellent TADF property. Moreover, the 26- and 246tCzPPC dopants favor a horizontal alignment enhancing the light outcoupling of the device. In contrast, 35tCzPPC favors a perpendicular alignment reducing the light outcoupling efficiency of the device. The 246tCzPPC-based devices show external quantum efficiency as high as 29.6% because of excellent TADF property, very high photoluminescence quantum yield, and high Θ value in the thin films. The device performance is the best among the pyridine-carbonitrile-based TADF emitters.
Ultra-efficient and stable OLED devices can be obtained via effective charge injection, accumulation, and exciton confinement into the emissive layer. However, the leakage of charge and excitons from ...the EML to adjacent layers can lead to low device performance. Thus, high-triplet-energy charge-transport materials (CTMs) are required to confront these issues. Herein, we demonstrate a class of efficient arylamine derivatives, viz. TPA-Py, TPA-2Py, and DPA-2Py, which were synthesized through the insertion of triphenyl pyridine as an acceptor unit to the aryl amino system to accomplish high triplet energy, thermal stability, and charge transportability during device operation. The charge-transfer analysis of the developed materials was accomplished for the S1 and T1 states through theoretical simulation. The intramolecular hole reorganization energies helped in understanding the hole transportability of these molecules. Single-crystal analysis indicated a considerable dihedral angle across the units, quasiplanar geometries, and the nonexistence of π–π stacking in the solid state. These molecular materials exhibited good thermal stability, which improve the morphological stability of their thin films. All of the molecules possess suitable HOMO energy levels for hole injection and appropriate LUMO energy levels for electron blocking from the emissive layer. Moreover, their high triplet energy (up to 2.69 eV) prevents exciton transfer from the EML to HTL and results in better device performance. The device with DPA-2Py as an HTM in a green OLED showed the maximum current efficiency (CE) and power efficiency (PE) values of ∼74 cd/A and ∼72 lm/W, respectively, with a maximum EQE of ∼21%. The PE of the current device is at par with the highest reported PE so far in solution-processed phosphorescent OLEDs.
The organic semiconducting polymer dots (Pdot) or nanoparticles exhibited a promising efficiency as photocatalyst for hydrogen production. This study reported a new Pdot-based photocatalyst ...constructed in the form of Donor-Acceptor-Metal cocatalyst (D-A-Mcat). These D-A-Mcat Pdots systems consisting of fluorene (F) as the donor, thienyl-benzo-dithiophene-dione (TBDD) as the acceptor and Ir (TPy)2 (acac) as the metal complex, and their structural, thermal, electrochemical and photophysical properties were systematically demonstrated for the first time. Introducing the cyclometalated iridium (III) complex comonomer into the polymer chain resulting in PFTBDD-IrTPy Pdots showed enhancement of the hydrogen evolution rates, which is over 20-times higher than those of pure polymer (PFTBDD Pdots) under otherwise identical conditions. In addition, the optical and electrical measurements indicated that the cyclometalated iridium (III) part have an important function for inhibiting the charge recombination of the PFTBDD-IrTPy Pdots during the photocatalytic reaction. The result strongly implies that inserted catalytic amount of Ir(III)-complex into the D-A polymers is beneficial for the enhancement of photocatalytic hydrogen evolution, which can inspire further optimization and greater molecular design strategies at a low-cost are highly desirable for the development of high-performance in photocatalysis.
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•Donor and acceptor with cyclometallic Ir-based polymer dots (D-A-Mcat Pdots) are developed for hydrogen evolution.•The systematic study of PFTBDD-IrTPy Pdot of their thermal and photophysical properties are discussed.•PFTBDD-IrTPy Pdot is a potential candidate for high HER activity as compared to PFTBDD Pdots.•Introduction of Ir(III)-complex into the PFTBDD polymers is beneficial for the enhancement of photocatalytic activity.
Reaction mechanisms for the synthesis of indenamines, indenols, and isoquinolinium salts through cobalt- and rhodium-catalysis were investigated using density functional theory calculations. We found ...that the valence charge of transition metals dramatically influences the reaction pathways. Catalytic reactions involving lower-oxidation-state transition metals (MI/MIII, M = Co and Rh) generally favor a 3 + 2 cyclization pathway, whereas those involving higher oxidation states (MIII/MV) proceed through a 4 + 2 cyclization pathway. A catalytic cycle with novel MIII/MV as a crucial species was successfully revealed for isoquinolinium salts synthesis, in which highly valent MV was encountered not only in the RhCp*-catalysis but also in the CoCp*-catalysis.
The strategy of acceptor modification is a powerful technique for tuning the emission color of thermally activated delayed fluorescence (TADF) emitters. In this study, we have successfully designed ...and synthesized three TADF emitters with donor–acceptor (D–A) structures using a 4-(diphenylamino)-2,6-dimethylphenyl (TPAm) donor and various pyridine-3,5-dicarbonitrile (PC) acceptor units. As a result, three compounds named TPAmbPPC, TPAm2NPC, and TPAmCPPC exhibited greenish-yellow to orange-red emissions with high photoluminescent quantum yields (76–100%) in thin films. Remarkably, a greenish-yellow device based on TPAmbPPC and TPAm2NPC showed a high maximum external quantum efficiency (EQEmax) of 39.1 and 39.0%, respectively. Furthermore, benefiting from the suitable steric hindrance between the acceptor and donor, the nondoped organic light-emitting diodes (OLEDs) based on TPAmbPPC demonstrated an exceptional EQEmax of 21.6%, indicating its promising potential as an efficient emitter for the application of OLED applications. Furthermore, orange-red OLED devices based on TPAmCPPC exhibited a high EQEmax of 26.2%, a CE of 50.1 cd A–1, and a PE of 52.4 lm W–1.
Quaternary ammonium salts were synthesized in moderate to good yields through double oxidative C−H bond activation on azobenzenes. The mechanism of the highly regioselective reaction of 2‐azobiaryls ...with alkenes to give orange‐red‐fluorescent cinnolino2,3‐fphenanthridin‐9‐ium salts and 15H‐cinnolino2,3‐fphenanthridin‐9‐ium‐10‐ide is proposed to involve ortho C−H olefination of the 2‐azobiaryl compound with the alkene, intramolecular aza‐Michael addition, concerted metalation–deprotonation (CMD), reductive elimination, and oxidation.
Fired up: Orange‐red‐fluorescent cinnolino2,3‐fphenanthridin‐9‐ium salts were synthesized with high regioselectivity from 2‐azobiaryls and alkenes by palladium(II)‐catalyzed C−H activation under mild reaction conditions (see scheme). The prepared quaternary ammonium salts showed strong fluorescence emission maxima at 575–620 nm with broad bandwidths.
A highly regioselective synthesis of pyrido2,1‐aisoindolium salts from 2‐arylpyridines and two equivalents of electron‐deficient alkenes catalyzed by rhodium is demonstrated. The reaction was carried ...out in aqueous medium at 110 °C using inexpensive oxygen as oxidant. Reverse aza‐Michael addition of the isoindolium salt occurs when the salt was treated with base to give a β‐disubstituted alkene product. A reaction mechanism involving an ortho C–H olefination of 2‐arylpyridine by alkene, intramolecular aza‐Michael addition, deprotonation at the β‐carbon of the alkene fragment followed by another Michael addition to give the final product is proposed.
