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The endeavor to develop high‐performance narrowband blue organic light‐emitting diodes (OLEDs) with low efficiency roll‐off represents an attractive challenge. Herein, we introduce a hetero‐acceptor design strategy centered around the heptagonal diimide (BPI) building block to create an efficient thermally activated delayed fluorescence (TADF) sensitizer. The alignment of a twisted BPI unit and a planar diphenyltriazine (TRZ) fragment imparts remarkable exciton dynamic properties to 26tCz‐TRZBPI, including a fast radiative decay rate (kR) of 1.0×107 s−1 and a swift reverse intersystem crossing rate (kRISC) of 1.8×106 s−1, complemented by a slow non‐radiative decay rate (kNR) of 6.0×103 s−1. Consequently, 26tCz‐TRZBPI facilitates the fabrication of high‐performance narrowband pure‐blue TADF‐sensitized fluorescence OLEDs (TSF‐OLEDs) with a maximum external quantum efficiency (EQEmax) of 24.3 % and low efficiency roll‐off even at a high brightness level of 10000 cd m−2 (EQE10000: 16.8 %). This showcases a record‐breaking external quantum efficiency at a high luminance level of 10000 cd m−2 for narrowband blue TSF‐OLEDs. [ABSTRACT FROM AUTHOR]

Narrowband organic light‐emitting diodes (OLEDs) are receiving significant attention and have demonstrated impressive performance in blue and green OLEDs. However, developing high‐performance narrowband red OLEDs remains a highly desired yet challenging task. Herein, we have developed narrowband red fluorescent emitters by utilizing a boron‐dipyrromethene (BODIPY) skeleton in combination with a methyl‐shield strategy. These emitters exhibit small full‐width at half‐maxima (FWHM) ranging from 21 nm (0.068 eV) to 25 nm (0.081 eV) and high photoluminescence quantum yields (ΦPL) ranging from 88.5 % to 99.0 % in toluene solution. Using BODIPY‐based luminescent materials as emitters, high‐performance narrowband red OLEDs have been assembled with external quantum efficiency as high as 18.3 % at 623 nm and 21.1 % at 604 nm. This work represents, to our knowledge, the first successful case of achieving NTSC pure‐red OLEDs with the Commission Internationale de l'Éclairage (CIE) coordinates of [0.67, 0.33] based on conventional fluorescent emitters. [ABSTRACT FROM AUTHOR]

Suppressing aggregation‐caused quenching (ACQ) effect and reducing device efficiency roll‐off are both crucial yet challenging for multi‐resonance (MR) emitters. Herein, we put forward a medium‐ring strategy to design efficient MR emitters that feature heptagonal tribenzo[b,d,f]azepine (TBA) donors. The highly twisted conformation enlarges the intermolecular distances between the MR‐emitting cores, and thus suppresses ACQ effect. Meanwhile, the introduction of heptagonal donors enhances spin‐orbital coupling, so as to accelerate reverse intersystem crossing (RISC) process. This medium‐ring strategy gives rise to the first example of blue MR emitter that simultaneously possesses radiative decay rate as fast as 108 s−1 and RISC rate as fast as 106 s−1. Accordingly, DTBA‐B2N3 enables to assemble high‐performance blue organic light‐emitting diodes (OLEDs) with maximum external quantum efficiency (EQEmax) of 30.9 % and alleviated efficiency roll‐off (EQE1000: 20.5 %). [ABSTRACT FROM AUTHOR]

Disclosed herein is a RhCl3‐catalyzed peri‐selective C−H/C−H oxidative homo‐coupling of 1‐substituted naphthalenes, which provides a highly efficient and streamlined approach to chalcogen‐embedded anthanthrenes from readily available starting materials. Introducing O, S, and Se into the anthanthrene skeleton leads to gradually increased π–π stacking distances but significantly enhanced π–π overlaps with the growth of the hetero‐atom radius. Moderate π–π distance, overlap area, and intermolecular S−S interactions endow S‐embedded anthanthrene (PTT) with excellent 2D charge‐transport properties. Moreover, the transformation of p‐type to n‐type S‐embedded anthanthrenes is realized for the first time via the S‐atom oxidation from PTT to PTT‐O4. In organic field‐effect transistor devices, PTT derivatives exhibit hole transport with mobilities up to 1.1 cm2 V−1 s−1, while PTT‐O4 shows electron transport with a mobility of 0.022 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

The development of intramolecular‐lock strategy is an appealing task for designing efficient thermally activated delayed fluorescence (TADF) molecules, but only limited examples have been reported so far. Herein we present a "medium ring"‐lock strategy to develop TADF emitters for improving the efficiency of organic light‐emitting diodes (OLEDs). The installation of an electron‐deficient heptagonal diimide lock onto a highly rotatable biphenyl‐based emitter not only enhances electron‐withdrawing ability of acceptor that decreases singlet‐triplet energy gap (ΔEST), but also endows the skeleton with modest rigidity and flexibility that increases photoluminescence quantum yield (PLQY) in neat film. In particular, the integration of the diimide lock also leads to an increase in horizontal orientation factor (Θ//) from 69 % to 83 %. Consequently, this modified intramolecular‐lock strategy enables an efficient TADF emitter to assemble high‐performance non‐doped OLEDs with a high external quantum efficiency of 26.2 % and a power efficiency of 76.6 lm W−1. [ABSTRACT FROM AUTHOR]

An approach allowing remote editing of stacked aromatic assemblies for heteroannular C−H functionalization would represent a transformative chemical toolbox that may make the diversification of complex molecules in a straightforward manner. However, such a C−H activation is usually less kinetically and thermodynamically favorable than homoannular ortho C−H activation and remains a fundamental challenge. Herein we disclose an engineer's approach, using a transient ligand as an interim bridge between two aryl rings (analogues to mountaintops) to anchor the metal center on the remote heteroannular C−H bond. As a proof‐of‐concept, we present the palladium‐catalyzed heteroannular C−H olefination of stacked aromatic assemblies with olefins and allylation with vinyl acetates using L‐tert‐leucine acid as a transient ligand. Mechanistic investigations suggest an unusual olefin coordination‐promoted interannular palladium migration process determinative for reversal of the site‐selectivity. [ABSTRACT FROM AUTHOR]

Multi‐resonance boron‐nitrogen‐containing thermally activated delayed fluorescence (MR‐TADF) emitters have experienced great success in assembling narrowband organic light‐emitting diodes (OLEDs). However, the slow reverse intersystem crossing rate (kRISC) of MR‐emitters (103–105 s−1) that will lead to severe device efficiency roll‐off has received extensive attention and remains a challenging issue. Herein, we put forward a "space‐confined donor‐acceptor (SCDA)" strategy to accelerate RISC process. The introduction of SCDA units onto the MR‐skeleton induces intermediate triplet states, which leads to a multichannel RISC process and thus increases kRISC. As illustrated examples, efficient MR‐emitters have been developed with a sub‐microsecond delayed lifetime and a high kRISC of 2.13×106 s−1, which enables to assemble high‐performance OLEDs with a maximum external quantum efficiency (EQEmax) as high as 32.5 % and an alleviated efficiency roll‐off (EQE1000: 22.9 %). [ABSTRACT FROM AUTHOR]

The development of high‐performance blue organic light‐emitting diodes (OLEDs) remains a challenging task. While exploiting new blue emitters has attracted great interest, developing host materials that considerably determine device performance obviously lags behind. Herein, we present an ease of access to the structurally diverse benzoheteroaromatic‐fused pyridine skeletons by the iridium‐catalyzed intramolecular C−H/C−H coupling reaction, which unlocks an unparalleled opportunity to rapidly assemble a library of pyridine‐fused bipolar host materials. As an illustrated example, the benzo[4,5]thieno[2,3‐b]pyridine skeleton (BTP) has been made to a pseudo‐symmetric host (DCz‐BTP). The merging of a pyridine fragment enables strong intermolecular interactions, leading to satisfactory bipolar transporting properties. Utilizing DCz‐BTP as the host, blue thermally activated delayed fluorescent OLEDs (TADF‐OLEDs) exhibit a low turn‐on voltage of 2.8 V and a high maximum external quantum efficiency (EQEmax) of 29.0 % and blue TADF‐sensitized florescent OLEDs (TSF‐OLEDs) give an EQEmax as high as 20.5 %, revealing the potential of the BTP skeleton for the construction of high‐performance host materials. [ABSTRACT FROM AUTHOR]

The academically widely used electron‐transporting materials (ETMs) typically suffer from low glass transition temperatures (Tg) that could lead to poor device stability. Considering practical applications, we herein put forward a "3D molecular interaction architecture" strategy to design high‐performance ETMs. As a proof‐of‐concept, a type of structurally nontraditional ETMs with the benzo[c]cinnoline (BZC) skeleton have been proposed and synthesized by the C−H/C−H homo‐coupling of N‐acylaniline as the key step. 2,9‐diphenylbenzo[c]cinnoline (DPBZC) exhibits strong intermolecular interactions that feature a 3D architecture, which boosts Tg to exceedingly high 218 °C with a fast electron mobility (μe) of 6.4×10−4 cm2 V−1 s−1. DPBZC‐based fluorescent organic light‐emitting diodes show outstanding electroluminescent performances with an external quantum efficiency of 20.1 % and a power efficiency as high as 70.6 lm W−1, which are superior to those of the devices with the commonly used ETMs. [ABSTRACT FROM AUTHOR]

The emitting layer based on a host–guest system plays a crucial role in organic light‐emitting diodes (OLEDs). While emitters have witnessed rapid progress in structural diversity, hosts still rely heavily on traditional structures and are underdeveloped. Herein a "medium‐ring" strategy has been put forward to design structurally nontraditional host molecules, which are not only rotatable enough to suppress close π–π stacking, thus reducing exciton annihilation, but also rigid enough to prevent excessive conformational flipping, thus inhibiting non‐radiative decay. Accordingly, a brand‐new type of bipolar hosts with a twisted "butterfly‐shaped heptagonal acceptor (EtBP), which features an electron‐deficient benzophenone fragment with a flexible ethylidene bridge, has been developed. With satisfactory morphological stability and well‐balanced hole‐ and electron‐transporting properties, the EtBP‐based bipolar hosts enable high‐performance RGB phosphorescent OLEDs with small efficiency roll‐off, which are superior to those of acyclic benzophenone‐based devices. [ABSTRACT FROM AUTHOR]

Herein disclosed is the first example of diarylation/annulation of benzoic acids via an iridium catalyst system. This protocol provides a step‐economic and highly efficient pathway to 1‐aryl, 1,3‐diaryl, 1,7‐diaryl and 1,3,7‐triaryl spirobifluorenes from readily available starting materials. The applications of multi‐aryl spirobifluorenes as pure hydrocarbon (PHC) hosts for red, green, and blue (RGB) phosphorescent organic light‐emitting diodes (PhOLEDs) were explored. Due to high triplet energies, 1,3‐diaryl spirobifluorenes exhibit the potential as the host material of blue PhOLEDs. 1,7‐Diaryl spirobifluorene can serve as the host of green PhOLEDs. 1,3,7‐Triaryl spirobifluorene is a high‐performance host for red PhOLEDs, which exhibits a high external quantum efficiency (EQE) up to 27.3 %. This work not only exemplifies the great potential of multi‐aryl spirobifluorenes as PHC hosts, but also offers a new approach for the synthesis of these PHC hosts. [ABSTRACT FROM AUTHOR]

The pursuit of efficient synthetic route to thienoacenes represents an appealing yet challenging task in the fields of both organic synthetic chemistry and organic functional materials. In this work, we disclose a rhodium‐catalyzed cascade C−H annulation of phenacyl phosphoniums with (benzo)thiophenes via a Heck‐type pathway to provide a new class of planar thienoacenes, which involves the formation of three Caryl‐Caryl bonds and one Caryl−O bond in a single operation. The neutral S,O‐heteroacenes exhibit superior stability and adopt a herringbone‐like packing mode with efficient π–π stacking in the crystals, suggesting their potential in organic semiconducting materials. This work first exemplifies the superiority of cascade oxidative C−H annulation involving a Heck‐type pathway in the development of concise access to heteroacenes. [ABSTRACT FROM AUTHOR]

Disclosed here is a palladium‐catalyzed direct [4+1] spiroannulation of ortho‐C−H bonds of naphthols with cyclic diaryliodonium salts to construct spirofluorenyl naphthalenones (SFNP) under mild reaction conditions. This spiroannulation directly transforms the hydroxy group into a carbonyl group, and also tolerates reactive functional groups such as the halo groups, which provide an opportunity to rapidly assemble structurally new thermally activated delayed fluorescent (TADF) materials that feature a carbonyl group with an adjacent spirofluorenyl unit as the acceptor. As an illustrated example, the OLED device utilizing the assembled DMAC‐SFNP as the host material exhibits a low turn‐on voltage of 2.5 V and an ultra‐high external quantum efficiency of 32.2 %. This work provides inspiration for structurally new TADF materials, and also displays the potential of C−H activation as a synthetic strategy for the innovation of optoelectronic materials. [ABSTRACT FROM AUTHOR]

Despite the aesthetically appealing structures and tantalizing physical and chemical properties, zigzag hydrocarbon belts and their heteroatom‐embedded analogues remain challenging synthetic targets. We report herein the synthesis of diverse O/N‐doped zigzag hydrocarbon belts based on selective bridging of the fjords of resorcin[4]arene derivatives through intramolecular SNAr and palladium‐catalyzed intermolecular C−N bond formation reactions. Preorganized conformations of mono‐macrocyclic, half‐belt and quasi‐belt compounds were revealed to facilitate cyclization reactions to construct heteroatom‐linked octahydrobelt[8]arenes. The acquired products had strained square‐prism‐shaped belt structures in which all six‐membered heterocyclic rings adopted an unusual boat conformation with equatorially configured alkyl groups. The unprecedented heteroatom‐bearing belts also exhibited different photophysical and redox properties to those of octahydrobelt[8]arene analogues. [ABSTRACT FROM AUTHOR]

Described herein is a strategy to construct cationic azahelicenes through the three‐component annulation reaction of isoquinoline, indole, and 1,2‐dichloroethane (DCE), in which DCE serves as an in situ activating agent for C1−H activation of isoquinoline, a vinyl equivalent, and a solvent. This in situ activation annulation reaction features a facile one‐step synthesis and complete regioselectivity. The complete regioselectivity of C1 over C3 for the isoquinoline ring paves a path to the helical structure in a highly ordered sequence. One of the synthesized ionic [5]azahelicenium fluorophores exhibits the potential to serve as a mitochondria‐targeted biomarker with good photostability and low cytotoxicity. [ABSTRACT FROM AUTHOR]

In the application of new fluorescent bioimaging reagents, typically, one synthetic method yields one type of organelle tracker. Herein, a molecular engineering approach to access fluorescent trackers of multiple organelles via a powerful synthetic toolbox is described. Starting from easily available acridone and analogues, a one‐pot strategy is set up for the synthesis of structurally diversified heteroatom‐doped polycyclic aromatic hydrocarbons (PAHs, types I–V) through the rhodium‐catalyzed oxidative [4 + 2] cyclization of C = X (X = N, O, S) bonds with alkynes, which assembles both ionic and neutral fluorescent frameworks. The tetracyclic acridine‐type luminogens (I–IV) are capable of targeting multiple organelles, including lysosome, endoplasmic reticulum, mitochondria, and mitochondria‐nucleus, in which the chemical environments of the nitrogen atom modulate the targeting regions. The fluorescent organelle trackers developed herein possess unique features. The formally protonated type I molecules are suitable for the long‐term detection of the lysosomes (>24 h). The type IV molecules exhibit the photo‐induced transfer from mitochondria to nucleus targeting, which indicates that IV can be used as an effective tool for real‐time research on physiological processes related to cell trafficking. [ABSTRACT FROM AUTHOR]

The development of efficient non‐doped organic light‐emitting diodes (OLEDs) is highly desired but very challenging because of a severe aggregation‐caused quenching effect. Herein, we present a heptagonal diimide acceptor (BPI), which can restrict excessive intramolecular rotation and inhibit close intermolecular π–π stacking due to well‐balanced rigidity and rotatability of heptagonal structure. The BPI‐based luminogen (DMAC‐BPI) shows significant aggregation‐induced delayed florescence with an extremely high photoluminescence quantum yield (95.8 %) of the neat film, and the corresponding non‐doped OLEDs exhibit outstanding electroluminescence performance with maximum external quantum efficiency as high as 24.7 % and remarkably low efficiency roll‐off as low as 1.0 % at 1000 cd m−2, which represents the state‐of‐the‐art performance for non‐doped OLEDs. In addition, the synthetic route to DMAC‐BPI is greatly streamlined and simplified through oxidative Ar−H/Ar−H homo‐coupling reaction. [ABSTRACT FROM AUTHOR]

Squaraines (SQs) with tunable emission in the solid state is of great importance for various demands; however a remaining challenge is emission quenching upon aggregation. Herein, a unique SQ, named as CIEE‐SQ, is designed to exhibit strong emission in crystal, undergoing crystallization‐induced reverse from dark 1(n+σ,π*) to bright 1(π,π*) excited states. Such an excited state of CIEE‐SQ can be subtly tuned by molecular conformation changes during the unexpected temperature‐triggered single‐crystal to single‐crystal (SCSC) reversible transformation. Furthermore, co‐crystallization between CIEE‐SQ and chloroform largely stabilize the 1(π,π*) state, enhancing the transition dipole moment and decreasing the reorganization energy to boost the fluorescence, which is promising in data encryption and decryption. [ABSTRACT FROM AUTHOR]

The hydroformylation of alkynes is a fundamental and important reaction in both academic research and industry. Conventional methods focus on the conversion of alkynes, CO, and H2 into α,β‐unsaturated aldehydes, but they often suffer from problems associated with operation, regioselectivity, and chemoselectivity. Herein, we disclose an operationally simple, mild, and syngas‐free rhodium‐catalyzed reaction for the hydroformylation of alkynes via formyl and hydride transfer from an alkyl aldehyde. This synthetic method uses inexpensive and easy‐to‐handle n‐butyraldehyde to overcome the challenge posed by the use of syngas in traditional approaches and employs a commercially available catalyst and ligand to transform a broad range of internal alkynes, especially alkynyl‐containing complex molecules, into versatile stereodefined α,β‐unsaturated aldehydes with excellent chemo‐, regio‐, and stereoselectivity. [ABSTRACT FROM AUTHOR]

Disclosed herein is the merging of C−H activation and radical chemistry, enabling rapid access to a structurally diverse family of fused carbohelicenes through the fusion of α‐acetylnaphthalenes with alkynes under oxidative conditions. This cascade process exhibits exquisite chemoselectivity and regioselectivity. The reaction pathway was analyzed by intermediate separations, control experiments, radical trapping, EPR, MALDI‐TOF‐MS, and ESI‐HRMS experiments, and shown to involve a C2−H activation/radical reaction/C8−H activation relay. Carbohelicenes were synthesized with unparalleled ease in a C−H activation/radical reaction/C−H activation sequence starting from α‐acetylnaphthalenes and alkynes. This process exemplifies the high compatibility of ionic and radical transformations. [ABSTRACT FROM AUTHOR]

Reported herein is a rhodium(III)‐catalyzed three‐component annulation reaction of simple pyridines, alkynes, and 1,2‐dichloroethane (DCE), affording a streamlined pathway to diverse ring‐fused pyridiniums. DCE not only serves as a vinyl equivalent but also as an in situ activating agent for pyridine C2−H activation. A cationic five‐membered rhodacycle complex has been isolated and proposed as a possible intermediate. This strategy can be extended to other N‐containing heteroarenes for the synthesis of multiring‐fused pyridiniums. These multicomponent reactions exhibit excellent regioselectivity for 1,3‐diynes, paving a path to the cascade cyclization of 3‐fluoropyridine or N‐methylpyridin‐3‐amine with 1,3‐diynes for the construction of brand‐new tricyclic‐fused pyrano‐ or hydropyridoquinolizinium salts. These ionic fluorophores have been investigated as potential biomarkers. Triple agent: Disclosed herein is a rhodium(III)‐catalyzed multicomponent reaction of simple pyridines, alkynes, and 1,2‐dichloroethane (DCE) to afford a streamlined pathway to diverse ring‐fused pyridiniums. DCE serves as a vinyl equivalent and an in situ activating agent for pyridine C2−H activation, as well as a solvent. [ABSTRACT FROM AUTHOR]

Abstract: By making use of a dual‐chelation‐assisted strategy, a completely regiocontrolled oxidative C−H/C−H cross‐coupling reaction between an N‐acylaniline and a benzamide has been accomplished for the first time. This process constitutes a step‐economic and highly efficient pathway to 2‐amino‐2′‐carboxybiaryl scaffolds from readily available substrates. A Cp*‐free RhCl3/TFA catalytic system was developed to replace the [Cp*RhCl2]2/AgSbF6 system generally used in oxidative C−H/C−H cross‐coupling reactions between two (hetero)arenes (Cp*=pentamethylcyclopentadienyl, TFA=trifluoroacetic acid). The RhCl3/TFA system avoids the use of the expensive Cp* ligand and AgSbF6. As an illustrative example, the procedure developed herein greatly streamlines the total synthesis of the naturally occurring benzo[c]phenanthridine alkaloid oxynitidine, which was accomplished in excellent overall yield. [ABSTRACT FROM AUTHOR]

Abstract: The functionalization of thiophenes is a fundamental and important reaction. Herein, we disclose iridium‐catalyzed one‐pot annulation reactions of (benzo)thiophenes with (hetero)aromatic or α,β‐unsaturated carboxylic acids, which afford thiophene‐fused coumarin‐type frameworks. Dearomatization reactions of 2‐substituted thiophenes with α,β‐unsaturated carboxylic acids deliver various thiophene‐containing spirocyclic products. The occurrence of two interconnected reactions provides direct evidence for a Heck‐type pathway. The mechanistic scenario described herein is distinctly different from the SEAr and concerted metalation–protodemetalation (CMD) pathways encountered in the well‐described oxidative C−H/C−H cross‐coupling reactions of thiophenes with other heteroarenes. [ABSTRACT FROM AUTHOR]

Described herein is the synthesis of stable oxonium-doped polycyclic aromatic hydrocarbons (PAHs) by the rhodium-catalyzed C−H activation/annulations of naphthalene-type aldehydes with internal alkynes. This protocol provides four divergent reaction types, including two unexpected annulations with an oxygen transposition process, which lead to diverse types of phenalenyl-fused pyrylium cations comprising a four-, five-, or six-ring-fused π-conjugated core. The annulations exhibit an exquisite regioselectivity and a high tolerance of sensitive functional groups. These PAHs feature intriguing photophysical properties such as full-color tunable fluorescence emission, high quantum yield, and positively charged core, and can be reduced easily to the phenalenyl radicals. [ABSTRACT FROM AUTHOR]

The fabrication of highly efficient deep-blue organic light-emitting field-effect transistors (OLEFETs) remains a challenge due to the large energy bandgap of deep-blue emitters. In this work, an effective strategy is developed by combining an ambipolar charge transport material with an efficient deep-blue fluorescent emitter that features the hybridized local and charge-transfer (HLCT) excited state character in a trilayer device architecture. The ambipolar nature of charge transport material endows the device with a relatively high hole-electron recombination efficiency, while the HLCT excited state character of the emitter offers the device a high singlet exciton yield. The device exhibits a maximum brightness of 710 cd m−2 and a maximum external quantum efficiency (EQE) of 0.28%, which is the first example of deep-blue OLEFETs. Unlike conventional OLEFETs, the devices presented herein display high EQEs during almost the entire illumination. The EQE of device at the maximum brightness reaches 0.20%, which is the highest value among the reported blue OLEFETs. Moreover, the device exhibits an excellent color purity with a sharp emission peak at 445 nm, a narrow full-width at half-maximum of 58 nm, and a Commission Internationale de l'Eclairage coordinates of (0.15, 0.06) that is very close to the National Television System Committee standard blue (0.14, 0.08). [ABSTRACT FROM AUTHOR]

A new type of water-soluble ruthenium sensitizers incorporating imidazolium counterions, denoted [DMPI]2−Ru and [DMHI]2−Ru, has been developed, which can be efficiently adsorbed onto TiO2 photoanodes in aqueous solution. Owing to the good thermal stability of imidazolium, [DMPI]2−Ru adsorbed on TiO2 has a higher decomposition temperature than N719 dye [di(tetrabutylammonium) cis-di(thiocyanato)bis(2,2′-bipyridine-4,4′-dicarboxylato)ruthenium(II)]. When using organic solvent-based I−/I3− electrolytes, solars cell based on [DMPI]2−Ru-sensitized TiO2 in water show high power conversion efficiencies (PCE) of up to 10.2 %, which is higher than that of N719 (9.9 %) under the common conditions for dye sensitization in organic solvent. [DMHI]2−Ru, with poorer water solubility than [DMPI]2−Ru, gives a smaller dye-adsorption amount on TiO2 and thus a lower PCE of 9.4 %. From the viewpoint of safety and environmental impact, the fabrication of dye-sensitized solar cells (DSSCs) by using water as solvent is undoubtedly a preferable strategy. Although the [DMPI]2−Ru-based device fabricated by using water as the solvent for both the dye-sensitization process and the electrolyte gives a relatively low efficiency, it provides a promising approach for the practical application of DSSCs. [ABSTRACT FROM AUTHOR]

An unprecedented Rh-catalyzed ketone-directed vinylic C−H activation/[4+2] O-annulation of α-aryl enones with internal alkynes followed by a Cu-catalyzed ring contraction in air to provide multiaryl-substituted furan derivatives has been developed. The preliminary mechanism study identifies the active pyrylium salt as the key intermediate. [ABSTRACT FROM AUTHOR]

Considerable efforts have been devoted to the development of highly efficient blue light-emitting materials. However, deep-blue fluorescence materials that can satisfy the Commission Internationale de l'Eclairage (CIE) coordinates of (0.14, 0.08) of the National Television System Committee (NTSC) standard blue and, moreover, possess a high external quantum efficiency (EQE) over 5%, remain scarce. Here, the unusual luminescence properties of triphenylamine-bearing 2-(2′-hydroxyphenyl)oxazoles ( 3a-3c) and their applications in organic light-emitting diodes (OLEDs) are reported as highly efficient deep-blue emitters. The 3a-based device exhibits a high spectral stability and an excellent color purity with a narrow full-width at half-maximum of 53 nm and the CIE coordinates of (0.15, 0.08), which is very close to the NTSC standard blue. The exciton utilization of the device closes to 100%, exceeding the theoretical limit of 25% in conventional fluorescent OLEDs. Experimental data and theoretical calculations demonstrate that 3a possesses a highly hybridized local and charge-transfer excited state character. In OLEDs, 3a exhibits a maximum luminance of 9054 cd m−2 and an EQE up to 7.1%, which is the first example of highly efficient blue OLEDs based on the sole enol-form emission of 2-(2′-hydroxyphenyl)azoles. [ABSTRACT FROM AUTHOR]

The most appealing oxidant, molecular oxygen, is employed for the first time as the sole oxidant in the transition metal-catalyzed oxidative direct arylation polymerization (C−H/C−H-type DArP), which eliminates by-product formation of stoichiometric metal salts except for water . Compared to conventional approaches, other than the avoidance of an end-capping procedure, the current protocol is remarkably advanced in the aspect of eco-friendliness, step- and cost-economy, and, of special significance, the purity of polymer products. As illustrative examples, six 5,5′-bithiazole-based polymers are synthesized using this new method, demonstrating higher number-average molecular weight ( Mn up to 33 700) in better yields (up to 93 %) through only one step. The evolution of C−H/C−H-type DArP from heavy metal salts to O2 alone as the oxidant could solve the problem of metal residues in polymers, which is considered harmful to the performance of devices. [ABSTRACT FROM AUTHOR]

Nickel can be used to promote oxidative C(sp2)−H/C(sp2)−H cross-coupling between two heteroarenes. The reaction scope can be extended to aromatic carboxamides as the coupling partner. The reaction exhibits high functional-group compatibility and broad substrate scope. The silver oxidant can be recycled to reduce costs and waste, which is very useful for practical applications. [ABSTRACT FROM AUTHOR]

The first example of cobalt-catalyzed oxidative C−H/C−H cross-coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2⋅4 H2O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C−H bond activation pathway that the well-described oxidative C−H/C−H cross-coupling reactions between two heteroarenes typically undergo. [ABSTRACT FROM AUTHOR]

A rapid access to 2,2′-bithiazole-based copolymers has been developed on the basis of the sequential palladium-catalyzed CH/CX and CH/CH coupling reactions. To assemble a 'copolymer' through homopolymerization, a type of symmetric A-B-A-type building block is designed as the monomer and prepared via the regioselective C5H arylation of thiazole. A PdCl2/CuCl-cocatalyzed oxidative CH/CH homopolymerization has been established to afford the 2,2′-bithiazole-based copolymers with high Mn (up to 69400). The current protocol features atom- and step-economy and exhibits a potential in the highly efficient construction of conjugated copolymers. [ABSTRACT FROM AUTHOR]

A metal-free radical cyclization of arenesulfonyl chlorides with alkynes has been developed, which provides a rapid and practical access to a variety of π-conjugated benzothiophenes with a broad reactive functional group tolerance. Furthermore, dialkynyl compounds could also undergo this transformation to give extended π-systems in good yields. [ABSTRACT FROM AUTHOR]

Reported herein is the first example of a transition-metal- catalyzed internal oxidative C-H/C-H cross-coupling between two (hetero)arenes through a traceless oxidation directing strategy. Without the requirement of an external metal oxidant, a wide range of phenols, including phenol-containing natural products, can undergo the coupling with azoles to assemble a large library of highly functionalized 2-(2-hydroxyphenyl)azoles. The route provides an opportunity to rapidly screen white-light-emitting materials. As illustrative examples, two bis(triphenylamine)-bearing 2-(2-hydroxyphenyl) oxazoles, which are difficult to access otherwise, exhibit bright white-light emission, high quantum yield, and thermal stability. Also presented is the first example of the white-light emission, in a single excited-state intramolecular proton transfer system, of 2-(2-hydroxyphenyl)azoles, thus highlighting the charm of C-H activation in the discovery of new organic optoelectronic materials. [ABSTRACT FROM AUTHOR]

Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well-developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under-represented. This work describes a novel CuCl-catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag2CO3 as the oxidant. Interestingly, simply changing the oxidant to K2S2O8 results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant-controlled catalytic transformations of phenols. [ABSTRACT FROM AUTHOR]

Disclosed herein is a RhIII-catalyzed chelation-assisted activation of unreactive C [ABSTRACT FROM AUTHOR]

Disclosed herein is a RhIII-catalyzed chelation-assisted activation of unreactive C [ABSTRACT FROM AUTHOR]

RhIII-catalyzed oxidative CH/CH cross-coupling between (hetero)aromatic carboxylic acids and various heteroarenes has been accomplished to construct highly functionalized ortho-carboxy-substituted bi(hetero)aryls. The use of a carboxy group as the directing group obviates tedious steps for installation and removal of extra directing groups, and enables a facile one-step synthesis of ortho-carboxy bi(hetero)aryls. The method provides opportunities for rapid assembly of a library of important fluorene and coumarin-type poly-heterocycles through intramolecular electrophilic substitution or oxidative lactonization. As illustrative examples, the strategy developed herein greatly streamlines accesses to a variety of appealing polyheterocycles such as DTPO (5 H-dithieno[3,2- b:2′,3′- d]pyran-5-one), CPDTO (cyclopentadithiophen-4-one), and indenothiophenes. [ABSTRACT FROM AUTHOR]

A transition-metal-free formal decarboxylative coupling reaction between α-oxocarboxylates and α-bromoketones to synthesize 1,3-diketone derivatives is presented. In this reaction, a broad scope of substrates can be employed, and neither a metal-based reagent nor an additional base is required. DFT calculations reveal that this reaction proceeds through a coupling followed by decarboxylation mechanism and the α-bromoketone unprecedentedly serves as a nucleophile under neutral conditions. The rate-determining step is an unusual hydrogen-bond-assisted enolate formation by thermolysis. [ABSTRACT FROM AUTHOR]

An unprecedented catalytic system composed of the Wilkinson catalyst [Rh(PPh3)3Cl] and CF3COOH enabled the highly regioselective cross-coupling of aromatic amines with a variety of heteroarenes through dual CH bond cleavage. This protocol provided a facile and rapid route from readily available substrates to (2-aminophenyl)heteroaryl compounds, which may be conveniently transformed into highly extended π-conjugated heteroacenes. The experimental studies and calculations showed that thianaphtheno[3,2-b]indoles have large HOMO-LUMO energy gaps and low-lying HOMO levels, and could therefore potentially be high-performance organic semiconductors. Herein we report the first use of a rhodium(I) catalyst for oxidative CH/CH coupling reactions. The current innovative catalyst system is much less expensive than [RhCp*Cl2]2/AgSbF6 and could open the door for the application of this approach to other types of CH activation processes. [ABSTRACT FROM AUTHOR]

A counterion-directed molecular design strategy is described for the spontaneous formation of stable vesicles via readily available imidazolium salts with the EDTA counterion in aqueous media. The counteranion is employed to adjust the balance between hydrophobic and hydrophilic parts, which satisfies the requirement of packing parameter for vesicle formation. The counterion-induced vesicles (CIVs) feature spontaneous formation, simple preparation, and easy availability of surfactants. Importantly, the unusual counterion-induced vesicle-like sphere aggregates can further chelate europium(III) ions to enhance the europium-centered emission in aqueous media and make it viable for an optical pH sensor, which exhibits a linear response in a wide range of pH values from 3 to 11. To the best of our knowledge, this constitutes one of the widest ranges of Eu-based pH sensors reported so far. This design concept has offered a new avenue for the preparation of functional vesicles. [ABSTRACT FROM AUTHOR]

In sharp contrast to the gold-catalyzed reactions of alkynes/allenes with nucleophiles, gold-catalyzed oxidative cross-couplings and especially CH/CH cross-coupling have been under represented. By taking advantage of the unique redox property and carbophilic π acidity of gold, this work realizes the first gold-catalyzed direct C(sp3)H alkynylation of 1,3-dicarbonyl compounds with terminal alkynes under mild reaction conditions, with subsequent cyclization and in situ oxidative alkynylation. A variety of terminal alkynes including aryl, heteroaryl, alkenyl, alkynyl, alkyl, and cyclopropyl alkynes all successfully participate in the domino reaction. The protocol offers a simple and region-defined approach to 3-alkynyl polysubstituted furans. [ABSTRACT FROM AUTHOR]

Diversification of the β -carboline skeleton has been demonstrated to assemble a β -carboline library starting from the tetrahydro-β -carboline framework. This strategy affords feasible access to heteroaryl-, aryl-, alkenyl-, or alkynyl-substituted β-carbolines at the C1, C3, or C8 position through three categorically different types of transition-metal-catalyzed CC bond-forming reactions, in the presence of multiple potentially reactive positions. These site-selective functionalizations include; 1) the Cu-catalyzed C1/C3-selective decarboxylative C [ABSTRACT FROM AUTHOR]

Mechanofluorochromic materials have great potential for a wide variety of applications such as sensors, memory devices, motion systems, security systems, and so forth. However, only few design principles have been disclosed, which greatly impedes the growth of mechanofluorochromic dyes. Here, a strategy of molecular design for mechanochromic luminescence is reported, based on the cation-anion interaction-directed switching of molecular stacking. On the basis of this strategy, a series of common N-heteroaromatic onium fluorophores such as imidazolium, 1,2,4-triazolium, triazolopyridinium, benzoimidazolium, γ-carbolinium, and pyridinium salts have been designed and proved to have striking reversible mechanofluorochromic behaviors. The simple attachment of a non-fluorescent imidazolium unit to the pyrene scaffold through a flexible carbon chain can even trigger the mechanofluorochromic phenomenon, which gives a consummate interpretation that the cation-anion interaction can be considered as an important general tool to design organic mechanochromic luminescent materials. [ABSTRACT FROM AUTHOR]

Colors to dye for: Palladium‐catalyzed regiospecific N‐heteroarylations of amidines with 2‐halo‐N‐heteroarenes leads to a structurally diverse library of BF2/amidine‐based complexes. These dyes not only present full‐visible‐color solid‐state emissions with large Stokes shifts and high fluorescence quantum yields, but also exhibit a full‐color‐tunable mechanofluorochromic nature. [ABSTRACT FROM AUTHOR]

Fully loaded: A coordinating activation strategy has been developed to furnish α‐quaternary α‐amino acids through the iron(III)‐catalyzed oxidative functionalization of α‐C(sp3)H bonds of α‐tertiary α‐amino acid esters. The reaction exhibits a broad substrate scope for both α‐amino acids and nucleophiles (Nu) as well as good functional‐group tolerance (see scheme, DTBP=di‐tert‐butyl peroxide, DCE=1,2‐dichloroethane). [ABSTRACT FROM AUTHOR]

Double role: A traceless directing group also acts as an internal oxidant in a novel RhIII‐catalyzed protocol developed for the synthesis of ortho‐alkenylated tertiary anilines (see scheme). A five‐membered cyclometalated RhIII complex is proposed as a plausible intermediate and confirmed by X‐ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

CC bond construction: A palladium‐catalyzed oxidative C sp 3H/C sp 3H cross‐coupling is shown to forge CC bonds rather than C sp 3C sp 3 bonds through reactions of indolin‐2‐ones or benzofuran‐2‐ones with O‐benzoyl hydroxylamines in the absence of an added oxidant. [ABSTRACT FROM AUTHOR]

Rhodium catalysis: A highly efficient and general method has been established to prepare cinnolines, cinnolinium salts, and polycyclic cinnolinium salts through the rhodium(III)‐catalyzed oxidative CH activation/cyclization of azo compounds with alkynes (see scheme). Key features of this methodology include the unprecedented capacity to create both cinnoline and cinnolinium frameworks. [ABSTRACT FROM AUTHOR]

A concise, highly efficient palladium-catalyzed direct C-H (hetero)arylation is developed to modularly assemble a diketopyrrolopyrrole ( DTDPP)-based polymer library to screen low-bandgap and near-infrared (NIR) absorbing materials. The DTDPP-based copolymers P1 and P2 with an alternating donor-acceptor-donor-acceptor (D-A-D-A) sequence and the homopolymer P9 exhibit planarity and excellent π-conjugation, which lead to low bandgaps (down to 1.22 eV) as well as strong and broad NIR absorption bands (up to 1000 nm). [ABSTRACT FROM AUTHOR]