A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple CH bond cleavage and CC and CN ...bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho CH activation, alkyne insertion, and reductive elimination, is proposed for this transformation.
Activated and annulated: A rhodium‐catalyzed one‐pot synthesis of highly substituted polyheteroaromatic compounds from N‐hydroxybenzamidines and alkynes is described. This reaction likely proceeds through multiple CH bond activation and annulation.
Over the past few decades, organic light-emitting diodes (OLEDs) find applications in smartphones, televisions, and the automotive sector. However, this technology is still not perfect, and its ...application for lighting purposes has been slow. For further development of the OLEDs, we designed twisted donor-acceptor-type electroactive bipolar derivatives using benzophenone and bicarbazole as building blocks. Derivatives were synthesized through the reaction of 4-fluorobenzophenone with various mono-alkylated 3,3'-bicarbazoles. We have provided a comprehensive structural characterization of these compounds. The new materials are amorphous and exhibit suitable glass transition temperatures ranging from 57 to 102 °C. They also demonstrate high thermal stability, with decomposition temperatures reaching 400 °C. The developed compounds exhibit elevated photoluminescence quantum yields (PLQY) of up to 75.5% and favourable HOMO-LUMO levels, along with suitable triplet-singlet state energy values. Due to their good solubility and suitable film-forming properties, all the compounds were evaluated as blue TADF emitters dispersed in commercial 4,4'-bis(N-carbazolyl)-1,10-biphenyl (CBP) host material and used for the formation of emissive layer of organic light-emitting diodes (OLEDs) in concentration-dependent experiments. Out of these experiments, the OLED with 15 wt% of the emitting derivative 4-(9'-{2-ethylhexyl}-3,3'-bicarbazol-9-yl)benzophenone exhibited superior performance. It attained a maximum brightness of 3581 cd/m
, a current efficacy of 5.7 cd/A, a power efficacy of 4.1 lm/W, and an external quantum efficacy of 2.7%.
Abstract
Photocatalytic water splitting is attracting considerable interest because it enables the conversion of solar energy into hydrogen for use as a zero-emission fuel or chemical feedstock. ...Herein, we present a universal approach for inserting hydrophilic non-conjugated segments into the main-chain of conjugated polymers to produce a series of discontinuously conjugated polymer photocatalysts. Water can effectively be brought into the interior through these hydrophilic non-conjugated segments, resulting in effective water/polymer interfaces inside the bulk discontinuously conjugated polymers in both thin-film and solution. Discontinuously conjugated polymer with 10 mol% hexaethylene glycol-based hydrophilic segments achieves an apparent quantum yield of 17.82% under 460 nm monochromatic light irradiation in solution and a hydrogen evolution rate of 16.8 mmol m
−2
h
−1
in thin-film. Molecular dynamics simulations show a trend similar to that in experiments, corroborating that main-chain engineering increases the possibility of a water/polymer interaction. By introducing non-conjugated hydrophilic segments, the effective conjugation length is not altered, allowing discontinuously conjugated polymers to remain efficient photocatalysis.
A series of new functional pyridine-appended pyrene derivatives, viz., 2,6-diphenyl-4-(pyren-1-yl)pyridine (Py-03), 2,6-bis(4-methoxyphenyl)-4-(pyren-1-yl)pyridine (Py-MeO), ...4-(pyren-1-yl)-2,6-di-p-tolylpyridine (Py-Me), and 2,6-bis(4-bromophenyl)-4-(pyren-1-yl)pyridine (Py-Br) were designed, developed, and studied as the hole-transporting materials (HTMs) for organic light-emitting diode (OLED) application. The crystal structures of two molecules revealed to have a large dihedral angle between the pyrene and pyridine units, indicating poor π-electronic communication between them due to ineffective orbital overlap across the pyrene–pyridine systems as the two p-orbitals of pivotal atoms are twisted at 66.80° and 68.75° angles to each other in Py-03 and Py-Me, respectively. The influence of variedly functionalized pyridine units on the electro-optical properties and device performance of the present integrated system for OLED application was investigated. All of the materials have suitable HOMO values (5.6 eV) for hole injection by closely matching the HOMOs of indium tin oxide (ITO) and the light-emitting layer. All of the synthesized molecules have suitable triplet energies, glass transition temperatures, and melting temperatures, which are highly desirable for good HTMs. The pyrene–pyridine-based devices demonstrated stable performance with low-efficiency roll-off. The device with Py-Br as HTM showed a maximum luminance of 17300 cd/m2 with a maximum current efficiency of 22.4 cd/A and an EQE of 9% at 3500 cd/m2 with 7% roll-off from 1000 to 10 000 cd/m2. Also, the devices with Py-Me and Py-03 showed performance roll-up while moving from 1000 to 10 000 cd/m2.
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‐sp2‐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.
RhIII and easy: A convenient synthesis of polycyclic pyridinium salts in excellent yields through RhIII‐catalyzed CH activation under an O2/CuII atmosphere at ambient temperature is described (see scheme). These salts showed strong fluorescence in CH2Cl2 (DME=1,2‐dimethoxyethane).
An efficient method for the synthesis of substituted isoquinolinium salts from benzaldehydes, amines, and alkynes via ruthenium-catalyzed C–H bond activation and annulation in one pot is described.
Deep-blue organic emitters have attracted considerable attention from both industrial as well as academic research in organic light-emitting diodes (OLEDs). In this context, three novel deep blue ...fluorophores based on benzothiazole 2-(4'-(1,4,5-triphenyl-1H-imidazole-2-yl)-1,1′-biphenyl-4-yl)benzo dthiazole (PHBISN), 2-(4'-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazole-2-yl)-1,1′-biphenyl-4-yl)benzo dthiazole (PTBISN) and 2-(4'-(4,5-diphenyl-1-(3-(trifluoromethyl)phenyl)-1H-imidazole-2-yl)-1,1′-biphenyl-4-yl)benzo dthiazole (m-CFBISN) were designed and synthesized. The fluorophores were structurally characterized and a detailed computational study reveals the compounds with wide energy gap (>3eV). The thermal properties, photophysical and electronic properties were systematically investigated. Photoluminescence and electroluminescence study shows fluorophores with deep blue emission. Novel synthesized fluorophores exhibit good performance for deep-blue solution-processed OLEDs. The doped device based on PTBISN shows the highest performance with deep blue electroluminescent and maximum EQE 1.5% with CIE color coordinates of (0.15, 0.08), which is near to the blue standard (0.14, 0.08) of the National Television System Committee (NTSC).
Display omitted
•Three new deep-blue emitters based on donor and acceptor (D-π-A) were designed and synthesized.•The synthesized emitters are thermally stable and showed deep-blue emission with good PLQY in solution and solid.•The solution-processed doped OLED device based on PTBISN shown deep-blue EL (0.15, 0.08) with EQEmax of 1.5%.
Highly efficient thermally activated delayed fluorescence (TADF) molecules are in urgent demand for solid‐state lighting and full‐color displays. Here, the design and synthesis of three ...triarylamine‐pyridine‐carbonitrile‐based TADF compounds, TPAPPC, TPAmPPC, and tTPAmPPC, are shown. They exhibit excellent photoluminescence quantum yields of 79−100% with small ΔEST values, fast reverse intersystem crossing (RISC), and high horizontal dipole ratios (Θ// = 86−88%) in the thin films leading to the enhancement of device light outcoupling. Consequently, a green organic light‐emitting diode (OLED) based on TPAmPPC shows a high average external quantum efficiency of 38.8 ± 0.6%, a current efficiency of 130.1 ± 2.1 cd A–1, and a power efficiency of 136.3 ± 2.2 lm W–1. The highest device efficiency of 39.8% appears to be record‐breaking among TADF‐based OLEDs to date. In addition, the TPAmPPC‐based device shows superior operation lifetime and high‐temperature resistance. It is worth noting that the TPA‐PPC‐based materials have excellent optical properties and the potential for making them strong candidates for TADF practical application.
Three 2,6‐diphenylpyridine‐3,5‐dicarbonitrile‐based compounds with excellent photoluminescent quantum yields (79–100%) and high horizontal dipole ratios (86−88%) in the thin films are demonstrated. With two methyl groups on the triarylamines, the spin−orbit coupling is enhanced due to the elevated locally excited triplet states (3LE), leading to a fast reverse intersystem crossing. Green thermally activated delayed fluorescence (TADF) organic light‐emitting diodes based on them exhibit a record‐high external quantum efficiency of 39.8% without any optical extraction technique.
An efficient synthesis of highly substituted isoquinolinium salts from ketimines and alkynes via a Rh(III)-catalyzed C-H bond activation and annulation reaction is described.
PDF
