查看更多>>摘要：Since polymer-based light-emitting diodes(PLEDs)are well-suited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high demand.To respond to this demand,light-emitting TADF units have initially been modified with electron-transporting units to balance the carrier transport of regiorandom TADF poly-mers,and simultaneously,an intramolecular sensitizing strategy has also been employed by covalently incorporat-ing TADF sensitizers with light-emitting TADF units and hosts in conjugated polymers to accelerate the spin-flip of triplet excitons.Superior photophysical properties have been achieved by a rational regulation of the proportions of each component,achieving a photoluminescence quan-tum yield of 90％,an extremely high rate of reverse intersys-tem crossing of 3 × 106 s-1,and a relatively low nonradiative decay rate of around 105 s-1.As a result,the solution-processed PLEDs can attain an external quantum efficiency(EQE)value of 25.4％with emission peaks of around 550 nm,representing record-high performance for PLEDs.The effi-ciency roll-off can also be significantly suppressed,main-taining an EQE value of 24.2％at 1000 cd/m2 with ideal efficiency roll-off of lower than 5％.Encouragingly,this work provides a valid strategy to tackle the imperative need for PLEDs with high EQE and low efficiency roll-off.
查看更多>>摘要：Epoxides are important chemicals and used in multi-ple fields.The conventional thermal-catalytic produc-tion of epoxides consumes a large amount of energy and generates abundant carbon emissions.Therefore,sustainable manufacturing technologies are highly desired.Taking advantage of renewable electricity to drive electrochemical epoxidation reactions provides a novel approach to generating value-added products in the chemicals sector.This review describes the current progress of selective electrochemical oxida-tion of olefins to epoxides,which is categorized according to the different reaction mechanisms.The halide-mediated method is first discussed,followed by an overview of electrochemical epoxidations with H2O and O2-derived H2O2.Moreover,the existing problems in this fast-growing field and future devel-oping directions are pointed out.This review hopes to provide inspiration for the design of electrocatalysts,electrode materials,and electrolyzers for the electro-chemical production of epoxides in a sustainable manner.
查看更多>>摘要：Photodynamic therapy(PDT)has emerged as an effi-cient method for cancer therapy.However,traditional photosensitizers(PSs)always have low bioavailabili-ty.For example,hydrophobic PSs tend to aggregate in cells and lead to aggregation-induced quenching;while hydrophilic PSs that have good solubility in water systems can hardly penetrate into cells whose membranes are lipophilic.To overcome these draw-backs,suitable PSs that meet the requirements of PDT are needed.Numerous investigations have been introduced,especially the molecular-assembly tech-nique that can increase the bioavailability of PSs during the tumor therapy process.Besides,increasing the quantum yield of reactive oxygen species(ROS)by adjusting the PS triplet state lifetime as well as developing aggregation-induced emission(AIE)agents can also improve the PDT effect.This review summarizes the molecular-assembly technique to ob-tain intelligent PSs to achieve high PDT efficiency.First,increasing the quantum yield of ROS by de-creasing the energy gap between S1 and T1 states or increasing the spin-orbit coupling Hamiltonian are introduced.Second,we present the bioavailability of traditional PSs by improving the amphiphilicity of the PSs or using intelligent nanostructures.Then,the AIE PSs that can form ROS in the aggregated state under irradiation are described.Finally,the perspective and challenges of PDT are discussed.
查看更多>>摘要：Amides are among the fundamental chemicals in organic chemistry.Compared to other carbonyl functional groups,the transformation of amide is relatively difficult and remains a challenge.The tra-ditional deconstruction transformations of amides to other functional products are usually limited to twisted or electronically activated amides.Herein,we describe a direct nitrogenation approach to con-vert amides into nitriles.This chemistry provides a novel amide transformation pathway via both C-C and C-N bond cleavage.Interestingly,the simple,readily available,and inexpensive inorganic salt NaNO2 is successfully employed as a nitrogen source in this organic N-incorporation process.Applications of this study are demonstrated through the late-stage modification of drug and natural product deri-vatives.
查看更多>>摘要：We report herein a visible light-mediated direct deu-teration of alkenes with D2O or deuterated methanol(MeOD)using a cobaloxime as a hydrogen/deuteri-um(H/D)exchange catalyst.The synergistic photoredox/Co catalysis enabled facile deuterium(D)-incorporation of a variety of terminal and internal alkenes at either terminal or benzylic positions.We proposed that this process proceeded through a sequence of reversible addition-elimination reac-tions and fast proton exchange involving Co(Ⅲ)-H,which was generated in situ by photoreduction.
查看更多>>摘要：Conjugated polyene motifs are ubiquitous in various natural products and functional molecules;however,their synthesis is very challenging because of the required lengthy and time-consuming processes.We herein report an efficient approach for the synthesis of(E,E)-trienes via cationic rhodium catalysis using acetylene and simple alkenes bearing diverse direct-ing groups as the starting materials.The reaction featured high step economy,excellent functional group compatibility,and exclusive stereoselectivity.Various directing groups such as carbonyl,sulfone,phosphate,hydroxyl,and amino were compatible.Furthermore,the triene products allowed versatile elaborations,providing rapid and convenient access to several important bioactive molecules,including vitamin A,(+)-roxaticin,and other complex polyenes.Mechanistic experiments showed that the directing group on the alkene played a crucial role in the reaction.
查看更多>>摘要：Sustainable and site-selective C-H functionalization is still a challenge because of the comparable prop-erties of bonds of the same type.Here,an electro-chemical C(sp2)-H/C(sp3)-H coupling with aryl iodides is reported for the first time.The C(sp2)-H bond outperformed the much weaker C(sp2)-I bond participating in C(sp2)-H/C(sp3)-H coupling.This protocol features mild reaction conditions,good functional group tolerance,and scalability.Cross-coupling products with C-I bonds are versatile moi-eties for further synthetic manipulation,that can undergo Suzuki,Sonogashira,Ullmann-Ma,Catellani,Heck reactions,and so on to introduce new function-al groups into target molecules with good yields.Mechanistic investigations showed that the site selectivity of the reaction is enabled by an iodine-assisted[3,3]-sigmatropic rearrangement,and the interaction of hypervalent iodine generated in situ with an enolate is the rate-determining step.
查看更多>>摘要：Covalent adaptable networks(CANs),which com-bine the benefits of traditional thermosets and ther-moplastics,have attracted considerable attention.The dynamics of reversible covalent bonds and mobility of polymer chains in CANs determine the topological rearrangement of the polymeric net-work,which is critical to their superior features,such as self-healing and reprocessing.Herein,we introduce an ionic liquid to dimethylglyoxime-urethane(DOU)-based CANs to regulate both reversible bond dynamics and polymer chain mo-bility by cooperative chemical coupling and physi-cal lubrication.Small-molecule model experiments demonstrated that ionic liquids can catalyze dy-namic DOU bond exchange.Ionic liquid also breaks the hydrogen bonds between polymeric chains,thereby increasing their mobility.As a combined result,the activation energy of the dissociation of the dynamic network decreased from 110 to 85 kJ mol-1.Furthermore,as a functional moiety,the ionic liquid imparts new properties to CANs and will greatly expand their applications.For example,the consequent conductivity of resultant ionic CAN(iCAN)has demonstrated a great power to build high-performance multifunctional wearable elec-tronics responsive to multiple stimulations includ-ing temperature,strain,and humidity.This study provides a new design principle that simultaneously uses the chemical and physical effects of two struc-tural components to regulate material properties enabling novel applications.
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