bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diketopyrrolopyrrole‐Based Conjugated Polymers Synthesized via Direct Arylation Polycondensation for High Mobility Pure n‐Channel Organic Field‐Effect Transistors
Authors: Guo Kai , Bai Junhua , Jiang Yu , Wang Zhongli , Sui Ying , Deng Yunfeng , Han Yang , Tian Hongkun , Geng Yanhou 
Published: June 2018

AbstractHigh‐performance unipolar n‐type conjugated polymers (CPs) are critical for the development of organic electronics. In the current paper, four “weak donor–strong acceptor” n‐type CPs based on pyridine flanked diketopyrrolopyrrole (PyDPP), namely PPyDPP1‐4FBT, PPyDPP2‐4FBT, PPyDPP1‐4FTVT, and PPyDPP2‐4FTVT, are synthesized via direct arylation polycondensation by using 3,3′,4,4′‐tetrafluoro‐2,2′‐bithiophene (4FBT) or (E)‐1,2‐bis(3,4‐difluorothien‐2‐yl)ethene (4FTVT) as weak donor unit. All four polymers exhibit low‐lying highest occupied molecular orbital (≈ −5.90 eV) and lowest unoccupied molecular orbital energy levels (≈ −3.70 eV). Top‐gate/bottom‐contact organic field‐effect transistors based on all four polymers display unipolar n‐channel characteristics with electron mobility (µe) above 1 cm2 V−1 s−1 in air, and presented linear |ISD|1/2 −VGS plots and weak dependence of the extracted moblity on gate voltage (VGS), indicative of the reliability of the extracted mobility values. Importantly, the devices based on PPyDPP1‐4FBT and PPyDPP2‐4FBT show a pure unipolar n‐channel transistor behavior as revealed by the typical unipolar n‐channel output characteristics and clear off‐regimes in transfer characteristics. Attributed to its high crystallinity and favorable thin film morphology, PPyDPP2‐4FBT shows the highest µe of 2.45 cm2 V−1 s−1, which is among the highest for unipolar n‐type CPs reported to date. This is also the first report for DPP based pure n‐type CPs with µe greater than 1 cm2 V−1 s−1.
Morphology Engineering in Monolayer MoS2‐WS2 Lateral Heterostructures
Authors: Zhou Jiadong , Tang Bijun , Lin Junhao , Lv Danhui , Shi Jia , Sun Linfeng , Zeng Qingsheng , Niu Lin , Liu Fucai , Wang Xiaowei , Liu Xinfeng , Suenaga Kazu , Jin Chuanhong , Liu Zheng 
Published: June 2018

AbstractIn recent years, heterostructures formed in transition metal dichalcogenides (TMDs) have attracted significant attention due to their unique physical properties beyond the individual components. Atomically thin TMD heterostructures, such as MoS2‐WS2, MoS2‐MoSe2, MoS2‐WSe2, and WSe2‐WS2, are synthesized so far via chemical vapor deposition (CVD) method. Engineering the morphology of domains including size and shape, however, still remains challenging. Here, a one‐step CVD strategy on the morphology engineering of MoS2 and WS2 domains within the monolayer MoS2‐WS2 lateral heterostructures through controlling the weight ratio of precursors, MoO3 and WO3, as well as tuning the reaction temperature is reported. Not only can the size ratio in terms of area between WS2 and MoS2 domains be easily controlled from less than 1 to more than 20, but also the overall heterostructure size can be tuned from several to hundreds of micrometers. Intriguingly, the quantum well structure, a WS2 stripe embedded in the MoS2 matrix, is also observed in the as‐synthesized heterostructures, offering opportunities to study quantum confinement effects and quantum well applications. This approach paves the way for the large‐scale fabrication of MoS2‐WS2 lateral heterostructures with controllable domain morphology, and shall be readily extended to morphology engineering of other TMD heterostructures.
Plasmon‐Promoted Electrochemical Oxygen Evolution Catalysis from Gold Decorated MnO2 Nanosheets under Green Light
Authors: Xu Jing , Gu Peng , Birch David J. S. , Chen Yu 
Published: June 2018

AbstractThe oxygen evolution reaction (OER) is of great importance for renewable energy conversion and storage; however, the intrinsic process is sluggish and suffers from severe efficiency loss as well as large overpotentials. In this work, with the introduction of the plasmonic effects by design of the Au‐MnO2 hybrid catalysts, it is demonstrated that this photophysical phenomenon could largely promote the confinement of the outer electrons of Mn cations by plasmonic “hot holes” generated on gold surface. These “hot holes” work as the effective electron trapper to form the active Mnn+ species which could provide active sites to extract electrons from OH− and eventually facilitate the electrochemical OER catalysis under low laser power. By tuning the laser intensity from 100 to 200 mW, the overpotential is decreased from 0.38 to 0.32 V, which is comparable to IrO2 and RuO2 catalysts. These findings may provide insights into activation of plasmon‐promoted electrocatalysis under low power laser irradiation/treatment and the design of novel composite electrocatalysts.
Heteroatom Effect on Star‐Shaped Hole‐Transporting Materials for Perovskite Solar Cells
Authors: García‐Benito Inés , Zimmermann Iwan , Urieta‐Mora Javier , Aragó Juan , Calbo Joaquín , Perles Josefina , Serrano Alvaro , Molina‐Ontoria Agustín , Ortí Enrique , Martín Nazario , Nazeeruddin Mohammad Khaja 
Published: June 2018

AbstractThree new star‐shaped hole‐transporting materials (HTMs) incorporating benzotripyrrole, benzotrifuran, and benzotriselenophene central cores endowed with three‐armed triphenylamine moieties (BTP‐1, BTF‐1, and BTSe‐1, respectively) are designed, synthesized, and implemented in perovskite solar cells (PSCs). The impact that the heteroatom‐containing central scaffold has on the electrochemical and photophysical properties, as well as on the photovoltaic performance, is systematically investigated and compared with their sulfur‐rich analogue (BTT‐3). The new HTMs exhibit suitable highest‐occupied molecular orbitals (HOMO) levels regarding the valence band of the perovskite, which ensure efficient hole extraction at the perovskite/HTM interface. The molecular structures of BTF‐1, BTT‐3, and BTSe‐1 are fully elucidated by single‐crystal X‐ray crystallography as toluene solvates. The optimized (FAPbI3)0.85(MAPbBr3)0.15‐based perovskite solar cells employing the tailor‐made, chalcogenide‐based HTMs exhibit remarkable power conversion efficiencies up to 18.5%, which are comparable to the devices based on the benchmark spiro‐OMeTAD. PSCs with BTP‐1 exhibit a more limited power conversion efficiency of 15.5%, with noticeable hysteresis. This systematic study indicates that chalcogenide‐based derivatives are promising HTM candidates to compete efficiently with spiro‐OMeTAD.
Enhancing Ultrafast Lithium Ion Storage of Li4Ti5O12 by Tailored TiC/C Core/Shell Skeleton Plus Nitrogen Doping
Authors: Yao Zhujun , Xia Xinhui , Xie Dong , Wang Yadong , Zhou Cheng‐ao , Liu Sufu , Deng Shengjue , Wang Xiuli , Tu Jiangping 
Published: June 2018

AbstractIt is of great importance to reinforce electronic and ionic conductivity of Li4Ti5O12 electrodes to achieve fast reaction kinetics and good high‐power capability. Herein, for the first time, a dual strategy of combing N‐doped Li4Ti5O12 (N‐LTO) with highly conductive TiC/C skeleton to realize enhanced ultrafast Li ion storage is reported. Interlinked hydrothermal‐synthesized N‐LTO nanosheets are homogeneously decorated on the chemical vapor deposition (CVD) derived TiC/C nanowires forming binder‐free N‐LTO@TiC/C core–branch arrays. Positive advantages including large surface area, strong mechanical stability, and enhanced electronic/ionic conductivity are obtained in the designed integrated arrays and rooted upon synergistic TiC/C matrix and N doping. The above appealing features can effectively boost kinetic properties throughout the N‐LTO@TiC/C electrodes to realize outstanding high‐rate capability at different working temperatures (143 mAh g−1/10 C at 25 °C and 122 mAh g−1/50 C at 50 °C) and notable cycling stability with a capacity retention of 99.3% after 10 000 cycles at 10 C. Moreover, superior high‐rate cycling life is also demonstrated for the full cells with N‐LTO@TiC/C anode and LiFePO4 cathode. The dual strategy may provoke wide interests in fast energy storage areas and motivate the further performance improvement of power‐type lithium ion batteries (LIBs).
Catalytic Cascade Access to Biaryl‐2‐Methyl Acetates from Pyruvate O‐Arylmethyl Ketoximes via the Palladium‐Catalyzed C(sp2)H Bond Arylation and C−O Bond Solvolysis
Authors: Shao Ling‐Yan , Xing Li‐Hao , Guo Ying , Yu Kun‐Kun , Wang Wei , Liu Hong‐Wei , Liao Dao‐Hua , Ji Ya‐Fei 
Published: June 2018

AbstractA catalytic cascade has been developed for the synthesis of biaryl‐2‐methyl acetates via a palladium‐catalyzed ortho‐C(sp2)−H bond arylation of pyruvate O‐arylmethyl ketoximes with aryl iodides followed by a solvolysis, in which the pyruvic ketoxime ester as a new auxiliary is employed to direct the C(sp2)−H bond activation. The straightforward treatment of O‐arylmethyl hydroxylamines and ethyl pyruvate with aryl iodides also provides the target products in a one‐pot fashion. Furthermore, the new palladacycle intermediate is unambiguously confirmed by single‐crystal X‐ray diffraction analysis. A plausible reaction pathway is proposed for the Pd‐catalyzed arylation‐acetolysis sequence.magnified image
Advances in Palladium‐Catalyzed Cascade Cyclizations
Authors: Biemolt Jasper , Ruijter Eelco 
Published: June 2018

AbstractThe past decades in organic chemistry have witnessed significant improvements in synthetic efficiency as a result of considerable progress in cascade reactions, tandem reactions, and related one‐pot processes. These methods are less time‐consuming and produce less waste compared to the classical stepwise approach. However, cascade chemistry requires a more careful design and compatible reaction types for success. Palladium‐catalyzed cross‐coupling reactions, with their well understood multistep catalytic cycles, form a promising basis for the design of cascade reactions. Furthermore, they are compatible with a range of functional groups and can be combined with a range of secondary transformations. The resulting palladium‐catalyzed cascade reactions have provided access to a plethora of complex small molecules of high medicinal relevance. This review provides an overview of the developments in palladium‐catalyzed cascade reactions since 2011, classified according to the initiation, propagation, and termination steps comprising the palladium cascade reactions. This classification should assist the reader and may provide inspiration for the design of new cascade reactions.magnified image
Factors Important to Top Clinical Performance in Emergency Medicine Residency: Results of an Ideation Survey and Delphi Panel
Authors: Pines Jesse M. , Alfaraj Sukayna , Batra Sonal , Carter Caitlin , Manikoth Nisha , Roche Colleen N. , Scott James , Goldman Ellen F. 
Published: June 2018

AbstractObjectivesWe explore attributes, traits, background, skills, and behavioral factors important to top clinical performance in emergency medicine (EM) residency.MethodsWe used a two‐step process—an ideation survey with the Council of Emergency Medicine Residency Directors and a modified Delphi technique—to identify: 1) factors important to top performance, 2) preresidency factors that predict it, and 3) the best ways to measure it. In the Delphi, six expert educators in emergency care assessed the presence of the factors from the ideation survey results in their top clinical performers. Consensus on important factors that were exemplified in >60% of top performers were retained in three Delphi rounds as well as predictors and measures of top performance.ResultsThe ideation survey generated 81 responses with ideas for each factor. These were combined into 89 separate factors in seven categories: attributes, personal traits, emergency department (ED)‐specific skills and behaviors, general skill set, background, preresidency predictors, and ways to measure top performance. After three Delphi rounds, the panel achieved consensus on 20 factors important to top clinical performance. This included two attributes, seven traits, one general skill set, and 10 ED‐specific skills and behaviors. Interview performance was considered the sole important preresidency predictor and clinical competency committee results the sole important measure of top performance.ConclusionOur expert panel identified 20 factors important to top clinical performance in EM residency. Future work is needed to further explore how individuals learn and develop these factors.
Differences in xylogenesis between dominant and suppressed trees
Authors: Liu Shushan , Li Xiaoxia , Rossi Sergio , Wang Lily , Li Wei , Liang Eryuan , Leavitt Steven W. 
Published: June 2018

AbstractPremise of The StudyMost dendroecological studies focus on dominant trees, but little is known about the growing season of trees belonging to different size classes and their sensitivity to biotic factors. The objective of this study was to compare the dynamics of xylem formation between dominant and suppressed trees of Abies fabri of similar age growing in the Gongga Mountains, southeastern Tibetan Plateau, and to identify the association between xylem growth and climate.MethodsThe timing and duration of xylogenesis in histological sections were investigated weekly during the 2013–2015 growing seasons.Key ResultsOur investigation found that timing and duration of xylogenesis varied with canopy position and its associated tree size. Xylogenesis started 6–14 days earlier, and ended 5–11 days later in dominant trees than in suppressed trees, resulting in a significantly longer growing season. Dominant trees also exhibited higher temperature sensitivity of tracheid production rate than suppressed trees.ConclusionsThe observed differences in xylogenesis among trees suggested that competition affects tree growth by reducing the growing period in suppressed trees. Representative climate–growth relationships should involve trees of all size classes when evaluating the effects of the environment on forest dynamics.
Origin and diversification of winged bean (Psophocarpus tetragonolobus (L.) DC.), a multipurpose underutilized legume
Authors: Yang Shuyi , Grall Aurélie , Chapman Mark A. 
Published: June 2018

Premise of the StudyFor many crops, research into the origin and partitioning of genetic variation is limited and this can slow or prevent crop improvement programs. Many of these underutilized crops have traits that could be of benefit in a changing climate due to stress tolerance or nutritional properties. Winged bean (Psophocarpus tetragonolobus (L.) DC.) is one such crop. All parts of the plant can be eaten, from the roots to the seeds, and is high in protein as well as other micronutrients. The goal of our study was to identify the wild progenitor and analyze the partitioning of genetic variation in the crop.MethodsWe used molecular phylogenetic analyses (cpDNA and nuclear ITS sequencing) to resolve relationships between all species in the genus, and population genetics (utilizing microsatellites) to identify genetic clusters of winged bean accessions and compare this to geography.Key ResultsWe find that winged bean is genetically distinct from all other members of the genus. We also provide support for four groups of species in the genus, largely, but not completely, corresponding to the results of previous morphological analyses. Within winged bean, population genetic analysis using 10 polymorphic microsatellite markers suggests four genetic groups; however, there is little correspondence between the genetic variation and the geography of the accessions.ConclusionsThe true wild progenitor of winged bean remains unknown (or is extinct). There has likely been large‐scale cross‐breeding, trade, and transport of winged bean and/or multiple origins of the crop.
Base‐Promoted Synthesis of 2,4,6‐Triarylpyridines from Enaminones and Chalcones
Authors: Zhang Hong , Shen Jinhai , Cheng Guolin , Wu Binjie , Cui Xiuling 
Published: June 2018

AbstractA protocol for the synthesis of 2,4,6‐trisubstituted pyridines from N‐unsubstituted enaminones and chalcones via base‐promoted tandem Michael/cyclization reaction has been developed. This method provides an efficient, convenient route to 2,4,6‐trisubstituted pyridines with a good functional group tolerance under mild conditions in the absence of transition metal.
Chemical Engineering of Photoactivity in Heterometallic Titanium–Organic Frameworks by Metal Doping
Authors: Castells‐Gil Javier , Padial Natalia M. , Almora‐Barrios Neyvis , Albero Josep , Ruiz‐Salvador A. Rabdel , González‐Platas Javier , García Hermenegildo , Martí‐Gastaldo Carlos 
Published: June 2018

AbstractWe report a new family of titanium–organic frameworks that enlarges the limited number of crystalline, porous materials available for this metal. They are chemically robust and can be prepared as single crystals at multi‐gram scale from multiple precursors. Their heterometallic structure enables engineering of their photoactivity by metal doping rather than by linker functionalization. Compared to other methodologies based on the post‐synthetic metallation of MOFs, our approach is well‐fitted for controlling the positioning of dopants at an atomic level to gain more precise control over the band‐gap and electronic properties of the porous solid. Changes in the band‐gap are also rationalized with computational modelling and experimentally confirmed by photocatalytic H2 production.
Formazanate Complexes of Hypervalent Group 14 Elements as Precursors to Electronically Stabilized Radicals
Authors: Maar Ryan R. , Catingan Sara D. , Staroverov Viktor N. , Gilroy Joe B. 
Published: June 2018

AbstractThe stability of molecular radicals containing main‐group elements usually hinges on the presence of bulky substituents that shield the reactive radical center. We describe a family of Group 14 formazanate complexes whose chemical reduction allows access to radicals that are stabilized instead by geometric and electron‐delocalization effects, specifically by the square‐pyramidal coordination geometry adopted by the Group 14 atom (Si, Ge, Sn) within the framework of the heteroatom‐rich formazanate ligands. The reduction potentials of the Si, Ge, and Sn complexes as determined by cyclic voltammetry become more negative in that order. Examination of the solid‐state structures of these complexes suggested that their electron‐accepting ability decreases with increasing size of the Group 14 atom because a larger central atom increases the nonplanarity of the ligand‐based conjugated π‐electron system of the complex. The experimental findings were supported by density‐functional calculations on the parent complexes and the corresponding radical anions.
Catalytic Transformations of Functionalized Cyclic Organic Carbonates
Authors: Guo Wusheng , Gómez José Enrique , Cristòfol Àlex , Xie Jianing , Kleij Arjan W. 
Published: June 2018

AbstractFunctionalized cyclic organic carbonates and related heterocycles have emerged as highly versatile heterocyclic substrates for ring‐opening and decarboxylative catalytic transformations allowing for the development of new stereo‐ and enantioselective C−N, C−O, C−C, C−S and C−B bond formation reactions. Transition‐metal‐mediated conversions have only recently been rejuvenated as powerful approaches towards the preparation of more complex molecules. This minireview will highlight the potential of cyclic carbonates and structurally related heterocycles with a focus on their synthetic value and the mechanistic manifolds that are involved upon their conversion.
Organocatalytic Enantioselective Cross‐Vinylogous Rauhut–Currier Reaction of Methyl Coumalate with Enals
Authors: Liu Qiwen , Zu Liansuo 
Published: June 2018

AbstractThe organocatalytic enantioselective intermolecular cross‐vinylogous Rauhut–Currier (RC) reaction of methyl coumalate with α,β‐unsaturated aldehydes is reported, and the enals are activated by iminium catalysis to serve as the Michael acceptors and methyl coumalate is used as an activated diene to generate a latent enolate. The excellent selectivity is driven by the aromaticity of methyl coumalate, and the post transformation of this heterocyclic structure into other electron‐deficient arenes and heterocycles have addressed, in part, the challenging selectivity issues of the intermolecular cross‐RC reactions and the limited scope of iminium catalysis.
The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me, Ph, Et)
Authors: Culver Damien B. , Huynh Winn , Tafazolian Hosein , Ong Ta‐Chung , Conley Matthew P. 
Published: June 2018

AbstractMultinuclear solid‐state NMR studies of Cp*2Sc−R (Cp*=pentamethylcyclopentadienyl; R=Me, Ph, Et) and DFT calculations show that the Sc−Et complex contains a β‐CH agostic interaction. The static central transition 45Sc NMR spectra show that the quadrupolar coupling constants (Cq) follow the trend of Ph≈Me>Et, indicating that the Sc−R bond is different in Cp*2Sc−Et compared to the methyl and phenyl complexes. Analysis of the chemical shift tensor (CST) shows that the deshielding experienced by Cβ in Sc−CH2CH3 is related to coupling between the filled σC‐C orbital and the vacant
orbital.
Synthesis of Thiophene‐Based π‐Conjugated Oligomers via Ligand‐Enabled Pd‐Catalyzed Suzuki–Miyaura Coupling of Haloterthienyls
Authors: Guo Jie , Wu Yong , Kwong Fuk Yee , Zhang Heng , Lei Aiwen 
Published: June 2018

AbstractA ligand‐enabled Pd‐catalyzed Suzuki–Miyaura coupling of haloterthienyls for the synthesis of various thiophene‐based π‐conjugated oligomers including quinquethiophenes is demonstrated. An indolyl phosphine ligand plays an important role in this transformation. Thiopheneboronic acids were well applied, which might open up a window for the application of thiopheneboronic acids in the synthesis of thiophene‐based π‐conjugated oligomers in materials chemistry.
Bifunctional Solid Catalyst for Organic Reactions in Water: Simultaneous Anchoring of Acetylacetone Ligands and Amphiphilic Ionic Liquid “Tags” by Using a Dihydropyran Linker
Authors: Lai Bingbing , Mei Fuming , Gu Yanlong 
Published: June 2018

AbstractThe use of solid catalysts to promote organic reactions in water faces the inherent difficulty of the poor mass‐transfer efficiency of organic substances in water, which is often responsible for insufficient reaction and low yields. To solve this problem, the solid surface can be manipulated to become amphiphilic. However, the introduction of surfactant‐like moieties onto the surface of silica‐based materials is not easy. By using an accessible dihydropyran derivative as a grafting linker, a surfactant‐combined bifunctional silica‐based solid catalyst that possessed an ionic liquid tail and a metal acetylacetonate moiety was prepared through a mild Lewis‐acid‐catalyzed ring‐opening reaction with a thiol‐functionalized silica. The surfactant‐combined silica‐supported metal acetylacetone catalysts displayed excellent catalytic activity in water for a range of reactions. The solid catalyst was also shown to be recyclable, and was reused several times without significant loss in activity.
A Peptide‐Based Supramolecular Hydrogel for Controlled Delivery of Amine Drugs
Authors: Wang Youzhi , Zhang Yiming , Li Xinxin , Li Can , Yang Zhimou , Wang Ling 
Published: June 2018

AbstractSupramolecular hydrogels hold great promise for controlled drug delivery. Herein we report a supramolecular hydrogel based on a peptide bearing a terminal aldehyde. The hydrogel was prepared via an enzyme instructed self‐assembly (EISA) process, and the resulting hydrogels showed ultra‐stable properties in highly acidic or basic aqueous solutions. The hydrogelator could form Schiff bases with amine drugs. Owing to the pH‐responsive properties of Schiff bases, the hydrogels could be used for controlled release of encapsulated amine drugs. Our study provides a peptide‐based hydrogel that may be applied for controlled drug delivery.