bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Conducting Organic–Inorganic Hybrid Copper Sulfides CuxC6S6 (x=4 or 5.5): Ligand‐Based Oxidation‐Induced Chemical and Electronic Structure Modulation
Authors: Huang Xing , Qiu Yi , Wang Yishan , Liu Liyao , Wu Xiaoyu , Liang Yingying , Cui Yutao , Sun Yimeng , Zou Ye , Zhu Jia , Fang Weihai , Sun Junliang , Xu Wei , Zhu Daoben 
Published: September 2020

AbstractConductive coordination polymers (CPs) have potential in a wide range of applications because of their inherent structural and functional diversity. Three electrically conductive CPs (CuxC6S6, x=3, 4 or 5.5) derived from the same organic linker (benzenehexathiol) and metal node (copper(I)) were synthesized and studied. CuxC6S6 materials are organic–inorganic hybrid copper sulfides comprising a π‐π stacking structure and cooper sulfur networks. Charge‐transport pathways within the network facilitate conductivity and offer control of the Fermi level through modulation of the oxidation level of the non‐innocent redox‐active ligand. Two CuxC6S6 (x=4 or 5.5) CPs display high electrical conductivity and they feature a tunable structural topology and electronic structure. Cu4C6S6 and Cu5.5C6S6 act as degenerate semiconductors. Moreover, Cu5.5C6S6 is a p‐type thermoelectric material with a ZT value of 0.12 at 390 K, which is a record‐breaking performance for p‐type CPs.
A General Strategy for Development of Activatable NIR‐II Fluorescent Probes for In Vivo High‐Contrast Bioimaging
Authors: Ren Tian‐Bing , Wang Zhi‐Yao , Xiang Zhen , Lu Peng , Lai Huan‐Hua , Yuan Lin , Zhang Xiao‐Bing , Tan Weihong 
Published: September 2020

AbstractOrganic dye based NIR‐II fluorescent probes, owing to their high signal‐to‐background ratio and deeper penetration, are highly useful for deep‐tissue high‐contrast imaging in vivo. However, it is still a challenge to design activatable NIR‐II fluorescent probes. Here, a novel class of polymethine dyes (NIRII‐RTs), with bright (quantum yield up to 2.03 %), stable, and anti‐solvent quenching NIR‐II emission, together with large Stokes shifts, was designed. Significantly, the novel NIR‐II dyes NIRII‐RT3 and NIRII‐RT4, equipped with a carboxylic acid group, can serve as effective NIR‐II platforms for the design of activatable bioimaging probes with high contrast. As a proof of concept, a series of target‐activatable NIRII‐RT probes (NIRII‐RT‐pH, NIRII‐RT‐ATP and NIRII‐RT‐Hg) for pH, adenosine triphosphate (ATP), and metal‐ion detection, were synthesized. By applying the NIRII‐RT probe, the real‐time monitoring of drug‐induced hepatotoxicity was realized.
Biopolymer‐based Carriers for DNA Vaccine Design
Authors: Franck Christoph O. , Fanslau Luise , Bistrovic Popov Andrea , Tyagi Puneet , Fruk Ljiljana 
Published: September 2020

AbstractOver the last 30 years, genetically engineered DNA has been tested as novel vaccination strategy against various diseases, including human immunodeficiency virus (HIV), hepatitis B, several parasites, and cancers. However, the clinical breakthrough of the technique is confined by the low transfection efficacy and immunogenicity of the employed vaccines. Therefore, carrier materials were designed to prevent the rapid degradation and systemic clearance of DNA in the body. In this context, biopolymers are a particularly promising DNA vaccine carrier platform due to their beneficial biochemical and physical characteristics, including biocompatibility, stability, and low toxicity. This article reviews the applications, fabrication, and modification of biopolymers as carrier medium for genetic vaccines.
Iron‐Catalyzed Radical Relay Enabling the Modular Synthesis of Fused Pyridines from Alkyne‐Tethered Oximes and Alkenes
Authors: Du Fei , Li Shi‐Jun , Jiang Kun , Zeng Rong , Pan Xi‐Chun , Lan Yu , Chen Ying‐Chun , Wei Ye 
Published: September 2020

AbstractWe have rationally designed a new class of alkyne‐tethered oximes and applied them in an unprecedented iron‐catalyzed radical relay protocol for the rapid assembly of a wide array of structurally new and interesting fused pyridines. This method shows broad substrate scope and good functional‐group tolerance and enabled the synthesis of several biologically active molecules. Furthermore, the fused pyridines could be diversely functionalized through various simple transformations, such as cyclization, C−H alkylation, and a click reaction. DFT calculation studies indicate that the reactions involve cascade 1,5‐hydrogen atom transfer, 5‐exo‐dig radical addition, and cyclization processes. Moreover, preliminary biological investigations suggest that some of the fused pyridines exhibit good anti‐inflammatory activity by restoring the imbalance of inflammatory homeostasis of macrophages in a lipopolysaccharide‐induced model.
Direkte β‐ und γ‐C(sp3)‐H Alkinylierung freier Carbonsäuren**
Authors: Ghiringhelli Francesca , Uttry Alexander , Ghosh Kiron Kumar , van Gemmeren Manuel 
Published: September 2020

AbstractIn dieser Studie berichten wir über die Identifizierung einer neuen Klasse von Liganden für die Palladium‐katalysierte C(sp3)‐H‐Aktivierung, welche die direkte Alkinylierung freier Carbonsäuren ermöglicht. Im Gegensatz zu früheren synthetischen Methoden ist keine Einführung/Entfernung einer exogenen dirigierenden Gruppe erforderlich. Als Substrate kann eine breite Palette von Säuren verwendet werden, darunter sowohl α‐quartäre als auch anspruchsvolle α‐nicht‐quartäre Substrate. Zusätzlich wird über die Alkinylierung in der entfernten γ‐Position berichtet. Schließlich beinhaltet diese Studie vorläufige Ergebnisse zu einer enantioselektiven Variante der Titelreaktion sowie zu synthetischen Anwendungen der erhaltenen Produkte.
Bindung von CO am FeV‐Cofaktor der CO‐reduzierenden Vanadium‐Nitrogenase bei atomarer Auflösung
Authors: Rohde Michael , Grunau Katharina , Einsle Oliver 
Published: September 2020

AbstractNitrogenasen reduzieren N2, das häufigste Element in der Erdatmosphäre, das aufgrund seiner Dreifachbindung chemisch nicht leicht zugänglich ist. Vanadium‐Nitrogenase zeichnet sich zudem durch die Fähigkeit aus, Kohlenmonoxid, einen bekannten Inhibitor für alle Substrate mit Ausnahme von H+, umzusetzen. Die Reduktion von CO führt zur Bildung von Kohlenwasserstoffprodukten, welche das Potential für biotechnologische Anwendungen in Analogie zum industriellen Fischer‐Tropsch‐Verfahren bergen. Hier berichten wir über die bisher detaillierteste Struktur der Vanadium Nitrogenase bei einer Auflösung von 1.0 Å, in welcher CO nach katalytischer Umsetzung an den Cofaktor des aktiven Zentrums gebunden ist. CO verbrückt dabei die Eisenionen Fe2 und Fe6 und ersetzt damit das Sulfid S2B in einem Bindungsmodus, der mit bisherigen Berichten des CO‐Komplexes der Molybdän‐Nitrogenase in Einklang ist. Wir erläutern zudem die strukturellen Konsequenzen fortlaufender katalytischer Umsetzung, wenn CO wieder entfernt wird. Diese umfassen den Austausch von CO, möglicherweise durch OH−, Bewegungen der Seitenketten Q176D und K361D, die Rückkehr des Sulfids und das Auftauchen zweier zusätzlicher Wassermoleküle, die im CO‐gebunden Zustand nicht vorhanden sind.
Visible‐Light‐Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2
Authors: Lian Pengcheng , Long Wenhao , Li Jingjing , Zheng Yonggao , Wan Xiaobing 
Published: September 2020

AbstractThis work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2‐dichloride compounds using an inexpensive, low‐molecular‐weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C−Cl bonds in this synthetic process.
Ligand‐Controlled Regiodivergence in Nickel‐Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids**
Authors: Li Zi‐Qi , Fu Yue , Deng Ruohan , Tran Van T. , Gao Yang , Liu Peng , Engle Keary M. 
Published: September 2020

AbstractA nickel‐catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand‐free conditions, with up to 99 % yield and >20:1 selectivity. Alternatively, anti‐Markovnikov products can be accessed with a novel 4,4‐disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover‐limiting and selectivity‐determining step induced by the optimal ligand. DFT calculations reveal that in the anti‐Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate‐ and regioselectivity‐determining transmetalation transition state.
C−H Methylation of Iminoamido Heterocycles with Sulfur Ylides**
Authors: Ghosh Prithwish , Kwon Na Yeon , Kim Saegun , Han Sangil , Lee Suk Hun , An Won , Mishra Neeraj Kumar , Han Soo Bong , Kim In Su 
Published: September 2020

AbstractThe direct methylation of N‐heterocycles is an important transformation for the advancement of pharmaceuticals, agrochemicals, functional materials, and other chemical entities. Herein, the unprecedented C(sp2)‐H methylation of iminoamido heterocycles as nucleoside base analogues is described. Notably, trimethylsulfoxonium salt was employed as a methylating agent under aqueous conditions. A wide substrate scope and excellent level of functional‐group tolerance were attained. Moreover, this method can be readily applied to the site‐selective methylation of azauracil nucleosides. The feasibility of gram‐scale reactions and various transformations of the products highlight the synthetic potential of the developed method. Combined deuterium‐labeling experiments aided the elucidation of a plausible reaction mechanism.
Two Spectroscopies in One: Interference of Circular Dichroism and Raman Optical Activity
Authors: Wu Tao , Li Guojie , Kapitán Josef , Kessler Jiří , Xu Yunjie , Bouř Petr 
Published: September 2020

AbstractPreviously, we and other laboratories have reported an unusual and strong Raman optical activity (ROA) induced in solvents by chiral dyes. Various theories of the phenomenon appeared, but they were not capable of explaining fully the observed ROA band signs and intensities. In this work, an analysis based both on the light scattering theory and dedicated experiments provides a more complete understanding. For example, double‐cell magnetic circular dichroism and magnetic ROA experiments with copper‐porphyrin complex show that the induced chirality is observed without any contact of the solvents with the complex. The results thus indicate that a combination of electronic circular dichroism (ECD) with the polarized Raman scattering is responsible for the effect. The degree of circularity of solvent vibrational bands is a principal molecular property participating in the event. The insight and the possibility to predict the chirality transfer promise future applications in spectroscopy, chemical analysis and polarized imaging.
MOF‐Mediated Fabrication of a Porous 3D Superstructure of Carbon Nanosheets Decorated with Ultrafine Cobalt Phosphide Nanoparticles for Efficient Electrocatalysis and Zinc–Air Batteries
Authors: Hou Chun‐Chao , Zou Lianli , Wang Yu , Xu Qiang 
Published: September 2020

AbstractSuperstructures have attracted great interest owing to their potential applications. Herein, we report the first scalable preparation of a porous nickel‐foam‐templated superstructure of carbon nanosheets decorated with ultrafine cobalt phosphide nanoparticles. Uniform two‐dimensional (2D) Co‐metal organic framework (MOF) nanosheets (Co‐MNS) grow on nickel foam, followed by a MOF‐mediated tandem (carbonization/phosphidation) pyrolysis. The resulting superstructure has a porous 3D interconnected network with well‐arranged 2D carbon nanosheets on it, in which ultrafine cobalt phosphide nanoparticles are tightly immobilized. A single piece of this superstructure can be directly used as a self‐supported electrode for electrocatalysis without any binders. This “one‐piece” porous superstructure with excellent mass transport and electron transport properties, and catalytically active cobalt phosphide nanoparticles with ultrasmall size (3–4 nm), shows excellent trifunctional electrocatalytic activities for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), achieving great performances in water splitting and Zn–air batteries.
Self‐Waveguide Single‐Benzene Organic Crystal with Ultralow‐Temperature Elasticity as a Potential Flexible Material
Authors: Liu Bin , Lu Zhuoqun , Tang Baolei , Liu Hao , Liu Huapeng , Zhang Zuolun , Ye Kaiqi , Zhang Hongyu 
Published: September 2020

AbstractWith the increasing popularity and burgeoning progress of space technology, the development of ultralow‐temperature flexible functional materials is a great challenge. Herein, we report a highly emissive organic crystal combining ultralow‐temperature elasticity and self‐waveguide properties (when a crystal is excited, it emits light from itself, which travels through the crystal to the other end) based on a simple single‐benzene emitter. This crystal displayed excellent elastic bending ability in liquid nitrogen (LN). Preliminary experiments on optical waveguiding in the bent crystal demonstrated that the light generated by the crystal itself could be confined and propagated within the crystal body between 170 and −196 °C. These results not only suggest a guideline for designing functional organic crystals with ultralow‐temperature elasticity but also expand the application region of flexible materials to extreme environments, such as space technology.
Photochemical In Situ Exfoliation of Metal–Organic Frameworks for Enhanced Visible‐Light‐Driven CO2 Reduction
Authors: Zheng Hui‐Li , Huang Shan‐Lin , Luo Ming‐Bu , Wei Qin , Chen Er‐Xia , He Liang , Lin Qipu 
Published: September 2020

AbstractTwo novel two‐dimensional metal–organic frameworks (2D MOFs), 2D‐M2TCPE (M=Co or Ni, TCPE=1,1,2,2‐tetra(4‐carboxylphenyl)ethylene), which are composed of staggered (4,4)‐grid layers based on paddlewheel‐shaped dimers, serve as heterogeneous photocatalysts for efficient reduction of CO2 to CO. During the visible‐light‐driven catalysis, these structures undergo in situ exfoliation to form nanosheets, which exhibit excellent stability and improved catalytic activity. The exfoliated 2D‐M2TCPE nanosheets display a high CO evolution rate of 4174 μmol g−1 h−1 and high selectivity of 97.3 % for M=Co and Ni, and thus are superior to most reported MOFs. The performance differences and photocatalytic mechanisms have been studied with theoretical calculations and photoelectric experiments. This study provides new insight for the controllable synthesis of effective crystalline photocatalysts based on structural and morphological coregulation.
Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non‐Innocent Ligand and the Uranium Center
Authors: Wang Penglong , Douair Iskander , Zhao Yue , Wang Shuao , Zhu Jun , Maron Laurent , Zhu Congqing 
Published: September 2020

AbstractActivation of dinitrogen (N2, 78 %) and dioxygen (O2, 21 %) has fascinated chemists and biochemists for decades. The industrial conversion of N2 into ammonia requires extremely high temperatures and pressures. Herein we report the first example of N2 and O2 cleavage by a uranium complex, [N(CH2CH2NPiPr2)3U]2(TMEDA), under ambient conditions without an external reducing agent. The N2 triple bond breaking implies a UIII–PIII six‐electron reduction. The hydrolysis of the N2 reduction product allows the formation of ammonia or nitrogen‐containing organic compounds. The interaction between UIII and PIII in this molecule allows an eight‐electron reduction of two O2 molecules. This study establishes that the combination of uranium and a low‐valent nonmetal is a promising strategy to achieve a full N2 and O2 cleavage under ambient conditions, which may aid the design of new systems for small molecules activation.
α‐Functionalisation of Ketones Through Metal‐Free Electrophilic Activation
Authors: Zawodny Wojciech , Teskey Christopher J. , Mishevska Magdalena , Völkl Martin , Maryasin Boris , González Leticia , Maulide Nuno 
Published: September 2020

AbstractTriflic anhydride mediated activation of acetophenones leads to highly electrophilic intermediates that can undergo a variety of transformations when treated with nucleophiles. This electrophilic ketone activation gives access to α‐arylated and α‐oxyaminated acetophenones under metal‐free conditions in moderate to excellent yields and enables extension to the synthesis of arylated morpholines via generation of vinylsulfonium salts. Computational investigations confirmed the transient existence of intermediates derived from vinyl triflates and the role of the oxygen atoms at the para position of aromatic ring in facilitating their stabilisation.
Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si–H Bond Activation
Authors: Avigdori Idan , Pogoreltsev Alla , Kaushanski Alexander , Fridman Natalia , Gandelman Mark 
Published: September 2020

AbstractN‐heterocyclic nitrogen Lewis acids are a recent addition to the field of organic chemistry. Based on nitrenium cations, these acids where previously shown to generate Lewis adducts when combined with the appropriate Lewis bases. Herein, a triazinium‐based Lewis acid was combined with tBu3P to generate a frustrated Lewis pair (FLP) capable of cleaving, for the first time, Si−H bonds in silanes. Whereas low yields were initially encountered owing to insufficient Lewis acidity, a new nitrenium‐based Lewis acid was synthesized, and its superior Lewis acidity was experimentally and computationally confirmed. A FLP based on this acid cleaved the Si−H bond in PhSiH3, generating the triazane product in a quantitative yield. This unprecedented N−H triazane was fully characterized by multinuclear NMR techniques and single‐crystal X‐ray crystallography. A new class of compounds, N‐H triazanes display the potential capacity to participate in hydride transfer reactions.
Synthesis ofi‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions
Authors: Zhuang Sheng‐Yi , Cheng Ying , Zhang Qian , Tong Shuo , Wang Mei‐Xiang 
Published: September 2020

Abstracti‐Corona[3]arene[3]tetrazines were synthesized from the nucleophilic aromatic substitution reaction of resorcinol and its derivatives with 3,6‐dichlorotetrazine in a one‐pot fashion under mild conditions. All of the resulting macrocycles adopted 1,3,5‐alternate conformation irrespective of the nature of the substituents on both upper‐ and lower‐rims. i‐Corona[3]arene[3]tetrazine was found to self‐regulate its macrocyclic conformation and cavity to recognize anions with binding constants spanning from 26 M−1to 2.2×103 M−1depending on the structure of the anions. The selective binding resulted from a significant interdependent and synergistic effect between multiple tetrazine π/anion and Caryl–H/anion hydrogen bond interactions. Taking advantage of synergistic effect revealed, a cyanobenzene‐embedded i‐corona[3]arene[3]tetrazine was designedly synthesized and highly selective and very strong affinity toward nitrate with a binding constant of 2.2×105 M−1was achieved.
Double Histidine Based EPR Measurements at Physiological Temperatures Permit Site‐Specific Elucidation of Hidden Dynamics in Enzymes
Authors: Singewald Kevin , Bogetti Xiaowei , Sinha Kaustubh , Rule Gordon S , Saxena Sunil 
Published: September 2020

AbstractProtein dynamics is at the heart of all cellular processes. Here, we utilize the dHis‐CuIINTA label to obtain site‐specific information on dynamics for both an α‐helix and β‐sheet site of GB1, the immunoglobulin binding domain of protein G. Spectral features found in our CW‐EPR measurements were consistent with the overall rigid nature of GB1 and with predictions from molecular dynamics simulations. Using this information, we show the potential of this approach to elucidate the role of dynamics in substrate binding of a functionally necessary α‐helix in human glutathione transferase A1‐1 (hGSTA1‐1). We observe two dynamical modes for the helix. The addition of the inhibitor GS‐Met and GS‐Hex resulted in hGSTA1‐1 to favor the more rigid active state conformation, while the faster mode potentially aids the search for substrates. Together the results illustrate the remarkable potential of the dHis‐based labelling approach to measure site‐specific dynamics using room temperature lineshape analysis.
Hydrogen Purification through a Highly Stable Dual‐Phase Oxygen‐Permeable Membrane
Authors: Jia Lujian , He Guanghu , Zhang Yan , Caro Jürgen , Jiang Heqing 
Published: September 2020

AbstractUsing oxygen permeable membranes (OPMs) to upgrade low‐purity hydrogen is a promising concept for high‐purity H2 production. At high temperatures, water dissociates into hydrogen and oxygen. The oxygen permeates through OPM and oxidizes hydrogen in a waste stream on the other side of the membrane. Pure hydrogen can be obtained on the water‐splitting side after condensation. However, the existing Co‐ and Fe‐based OPMs are chemically instable as a result of the over‐reduction of Co and Fe ions under reducing atmospheres. Herein, a dual‐phase membrane Ce0.9Pr0.1O2−δ‐Pr0.1Sr0.9Mg0.1Ti0.9O3−δ (CPO‐PSM‐Ti) with excellent chemical stability and mixed oxygen ionic‐electronic conductivity under reducing atmospheres was developed for H2 purification. An acceptable H2 production rate of 0.52 mL min−1 cm−2 is achieved at 940 °C. No obvious degradation during 180 h of operation indicates the robust stability of CPO‐PSM‐Ti membrane. The proven mixed conductivity and excellent stability of CPO‐PSM‐Ti give prospective advantages over existing OPMs for upgrading low‐purity hydrogen.
A Concise Enantioselective Total Synthesis of (−)‐Deoxoapodine
Authors: Yoshida Kei , Okada Kosuke , Ueda Hirofumi , Tokuyama Hidetoshi 
Published: September 2020

AbstractWe have established a highly convergent 10‐step route for the total synthesis of (−)‐deoxoapodine, which is a hexacyclic aspidosperma alkaloid. The quaternary C5 center of the characteristic tetrahydrofuran ring was constructed by a chiral‐phosphoric‐acid‐catalyzed enantioselective bromocycloetherification in a 5‐endo fashion and subsequent allylation by using the Keck protocol. Construction of the aspidosperma skeleton features the formation of a nine‐membered lactam by a catalytic C−H palladation/alkylation cascade at the indole 2‐position and an iron‐catalyzed oxidative transannular reaction at a late‐stage of the synthesis.