The development of efficient metal‐free organic emitters with thermally activated delayed fluorescence (TADF) properties for deep‐blue emission is still challenging. A new family of deep‐blue TADF ...emitters based on a donor–acceptor architecture has been developed. The electronic interaction between donor and acceptor plays a key role in the TADF mechanism. Deep‐blue OLEDs fabricated with these TADF emitters achieved high external quantum efficiencies over 19.2 % with CIE coordinates of (0.148, 0.098).
Deep blue emission: An internal quantum efficiency (IQE) of almost 100 % was achieved in organic light‐emitting diodes by a rational molecular design strategy. The organic light‐emitting diodes showed deep‐blue thermally activated delayed fluorescence.
By simple modification of the functional groups on the donor unit, the thermally activated delayed fluorescence (TADF) properties of emitters can easily be manipulated. A series of deep blue to blue ...emissive TADF derivatives is developed, capable of deep‐blue emissions from 403 to 460 nm in toluene. Deep‐blue organic light‐emitting diodes (OLEDs) based on this series of TADF emitters are fabricated, resulting in an electroluminescence peak at 428 nm and a high external quantum efficiency of up to 10.3%. One deep‐blue OLED has achieved the commission internationale de l'eclairage (CIE) coordinates of (0.156, 0.063), which is among the best reported TADF performances for deep‐blue OLEDs with CIEy < 0.07.
A series of deep‐blue to blue emissive TADF derivatives is developed, by which deep‐blue emissions from 403 to 460 nm in toluene are achieved. Deep‐blue OLEDs based on this series of TADF emitters are fabricated, exhibiting an electroluminescence peak at 428 nm and a high external quantum efficiency of up to 10.3%.
Metal-catalyzed electrochemical diazidation of alkenes Fu, Niankai; Sauer, Gregory S.; Saha, Ambarneil ...
Science (American Association for the Advancement of Science),
08/2017, Letnik:
357, Številka:
6351
Journal Article
Recenzirano
Odprti dostop
Vicinal diamines are a common structural motif in bioactive natural products, therapeutic agents, and molecular catalysts, motivating the continuing development of efficient, selective, and ...sustainable technologies for their preparation. We report an operationally simple and environmentally friendly protocol that converts alkenes and sodium azide—both readily available feedstocks—to 1,2-diazides. Powered by electricity and catalyzed by Earth-abundant manganese, this transformation proceeds under mild conditions and exhibits exceptional substrate generality and functional group compatibility. Using standard protocols, the resultant 1,2-diazides can be smoothly reduced to vicinal diamines in a single step, with high chemoselectivity. Mechanistic studies are consistent with metal-mediated azidyl radical transfer as the predominant pathway, enabling dual carbon-nitrogen bond formation.
Interest in deuterated active pharmaceutical ingredients (APIs) is increasing as deuteration holds promise for kinetic isotope effect (KIE) regulated fine‐tuning of API performance. Moreover, ...deuterium isotope labeling is frequently carried out to study organic and bioorganic reaction mechanisms and to facilitate complex target synthesis. As such, methods for highly selective deuteration of organic molecules are highly desirable. Herein, we present an electrochemical method for the selective deuterodehalogenation of benzylic halides via a radical‐polar crossover mechanism, using inexpensive deuterium oxide (D2O) as the deuterium source. We demonstrate broad functional group compatibility across a range of aryl and heteroaryl benzylic halides. Furthermore, we uncover a sequential paired electrolysis regime, which permits switching between net reductive and overall redox‐neutral reactions of sulfur‐containing substrates simply by changing the identity of the sacrificial reductant employed.
Site‐specific introduction of deuterium is important in organic and medicinal chemistry. Herein, we present an electrochemical method for the deuterodehalogenation of aryl and heteroaryl benzylic halides, using inexpensive deuterium oxide as the deuterium source. We also uncover a sequential paired electrolysis regime, which permits switching between net reductive and overall redox‐neutral reactions of sulfur‐containing substrates.
Herbal medicines (HMs) are much appreciated for their significant contribution to human survival and reproduction by remedial and prophylactic management of diseases. Defining the scientific basis of ...HMs will substantiate their value and promote their modernization. Ever‐increasing evidence suggests that gut microbiota plays a crucial role in HM therapy by complicated interplay with HM components. This interplay includes such activities as: gut microbiota biotransforming HM chemicals into metabolites that harbor different bioavailability and bioactivity/toxicity from their precursors; HM chemicals improving the composition of gut microbiota, consequently ameliorating its dysfunction as well as associated pathological conditions; and gut microbiota mediating the interactions (synergistic and antagonistic) between the multiple chemicals in HMs. More advanced experimental designs are recommended for future study, such as overall chemical characterization of gut microbiota‐metabolized HMs, direct microbial analysis of HM‐targeted gut microbiota, and precise gut microbiota research model development. The outcomes of such research can further elucidate the interactions between HMs and gut microbiota, thereby opening a new window for defining the scientific basis of HMs and for guiding HM‐based drug discovery.
Riboflavin‐derived photocatalysts have been extensively studied in the context of alcohol oxidation. However, to date, the scope of this catalytic methodology has been limited to benzyl alcohols. In ...this work, mechanistic understanding of flavin‐catalyzed oxidation reactions, in either the absence or presence of thiourea as a cocatalyst, was obtained. The mechanistic insights enabled development of an electrochemically driven photochemical oxidation of primary and secondary aliphatic alcohols using a pair of flavin and dialkylthiourea catalysts. Electrochemistry makes it possible to avoid using O2 and an oxidant and generating H2O2 as a byproduct, both of which oxidatively degrade thiourea under the reaction conditions. This modification unlocks a new mechanistic pathway in which the oxidation of unactivated alcohols is achieved by thiyl radical mediated hydrogen‐atom ion.
Dynamic duo: The combination of electrochemistry and photochemistry allows the generation of highly reactive catalytic intermediates without the need for a chemical oxidant. This photoelectrocatalytic strategy thus accessed the elusive reactivity of flavins for oxidizing unactivated aliphatic alcohols. HAT=hydrogen‐atom transfer.
A family of organic emitters with a donor–σ–acceptor (D‐σ‐A) motif is presented. Owing to the weakly coupled D‐σ‐A intramolecular charge‐transfer state, a transition from the localized excited ...triplet state (3LE) and charge‐transfer triplet state (3CT) to the charge‐transfer singlet state (1CT) occurred with a small activation energy and high photoluminescence quantum efficiency. Two thermally activated delayed fluorescence (TADF) components were identified, one of which has a very short lifetime of 200–400 ns and the other a longer TADF lifetime of the order of microseconds. In particular, the two D‐σ‐A materials presented strong blue emission with TADF properties in toluene. These results will shed light on the molecular design of new TADF emitters with short delayed lifetimes.
Avoid long delays: A novel molecular design for thermally activated delayed fluorescence (TADF) emitters based on a donor–σ–acceptor motif led to short TADF decay lifetimes of less than 400 ns. Since shorter delayed lifetimes in TADF emitters are highly beneficial for device performance, this design strategy is expected to provide an effective approach to advanced TADF materials.
The bed nucleus of stria terminalis (BST) is a critical structure that mediates sustained vigilant responses to contextual, diffuse, and unpredictable threats. Dysfunction of the BST could lead to ...excessive anxiety and hypervigilance, which are often observed in posttraumatic stress disorder and anxiety disorders. Vigilance of potential future threats from the external environment is a basic brain function and probably requires rapid and/or short neural circuits, which enable both quick detection of the potential threats and fast adaptive responses. However, the BST in literature does not appear to receive spatial information directly from earlier visual or spatial processing structures. In this study, a novel subdivision of the BST is uncovered in monkey, rat, and mouse brains based on the human equivalent and is found in mouse to receive direct inputs from the ventral lateral geniculate nucleus and pretectal nucleus as well as from the spatial processing structures such as subiculum, presubiculum, and medial entorhinal cortex. This new subdivision, termed spindle‐shaped small cell subdivision (BSTsc), is located between the known BST and the anterior thalamus. In addition to the unique afferent connections and cell morphology, the BSTsc also displays unique molecular signature (e.g., positive for excitatory markers) compared with other BST subdivisions, which are mostly composed of inhibitory GABAergic neurons. The BSTsc appears to have largely overlapping efferent projections with other BST subdivisions such as the projections to the amygdala, hypothalamus, nucleus accumbens, septum, and brainstem. Together, the present study suggests that the BSTsc is poised to serve as a shortcut bridge directly linking spatial information from the environment to vigilant adaptive internal responses.
A novel subdivision of the bed nucleus of stria terminalis (BST) was identified in monkey, rat, and mouse brains based on the human equivalent. This spindle‐shaped small cell subdivision (BSTsc) receives its main inputs from the earlier visual and spatial processing structures and projects to many common target regions as other BST subdivisions do (see the graph). The neurons in the BSTsc mostly expresses excitatory marker genes while those in other BST components mainly contains inhibitory marker genes. The BSTsc is poised to serve as a shortcut bridge directly linking spatial information from the environment to vigilant adaptive internal responses.
Ultrathin ZnIn2S4 nanosheets (NSs) are grown on Co/N‐doped graphitic carbon (NGC) nanocages, composed of Co nanoparticles surrounded by few‐layered NGC, to obtain hierarchical Co/NGC@ZnIn2S4 hollow ...heterostructures for photocatalytic H2 generation with visible light. The photoredox functions of discrete Co, conductive NGC, and ZnIn2S4 NSs are precisely combined into hierarchical composite cages possessing strongly hybridized shell and ultrathin layered substructures. Such structural and compositional virtues can expedite charge separation and mobility, offer large surface area and abundant reactive sites for water photosplitting. The Co/NGC@ZnIn2S4 photocatalyst exhibits outstanding H2 evolution activity (e.g., 11270 µmol h−1 g−1) and high stability without engaging any cocatalyst.
Hierarchical Co/N‐doped graphitic carbon (NGC)@ ZnIn2S4 heterostructured cages are fabricated by supporting ultrathin ZnIn2S4 nanosheets on Co/NGC nanocages. This delicate design can facilitate charge separation and transport as well as provide large surface area and rich active sites for water photosplitting reactions. Outstanding activity and high stability for H2 evolution under visible light are achieved without the assistance of any cocatalysts.
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