bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalytic Enantioselective Carbonyl Propargylation Beyond Preformed Carbanions: Reductive Coupling and Hydrogen Auto‐Transfer
Authors: Ambler Brett R. , Woo Sang Kook , Krische Michael J. 
Published: August 2018

AbstractChiral metal complexes catalyze enantioselective carbonyl propargylation via reductive coupling or as hydrogen auto‐transfer processes, in which reactant alcohols serve dually as reductant and carbonyl proelectrophile. Unlike classical propargylation protocols, which rely on allenylmetal reagents or metallic reductants (e. g. NHK reactions), reductive protocols for carbonyl propargylation can occur in the absence of stoichiometric metals, precluding generation of metallic byproducts. Propargylations of this type exploit both enyne and propargyl halide pronucleophiles.
Ultra‐Stable Asymmetric Supercapacitors Constructed by In‐Situ Electro‐Oxidation Activated Ni@CNTs Composites
Authors: Zhang Xiaojia , Wang Lei , Wei Zengxi , Zhang Guanhua , Zeng Wei , Fu Jiecai , Liu Quanhui , Duan Huigao 
Published: August 2018

AbstractUp to now, it is still an enormous challenge to build high‐performance asymmetric supercapacitors showing long cycling life and superior rate capability. In this work, unique three‐dimensional nickel deposited onto carbon nanotubes (Ni@CNTs) composites are synthesized by a reduction and catalytic growth process with ethanol as both, reductive agent and green carbon source. Asymmetric supercapacitors are assembled by only using the Ni@CNTs composites as positive and negative electrodes with our concept “one for two”, in rational combination with electro‐oxidation activation. Here, the three‐dimensional CNTs are responsible for the electric double layer capacitance and the encapsulated NiOOH nanoparticles derived from electro‐oxidation reaction contribute to pseudocapacitance. The asymmetric devices exhibit remarkable cycling stability with 100 % capacitance retention even up to 60,000 cycles at a current density of 10 mA cm−2 and excellent rate capability with 72.9 % capacitance retention with the current density increasing from 5 to 50 mA cm−2. To better understand the electrochemical behavior, the relative contributions from electric double layer capacitance and pseudocapacitance of the positive electrode as well as the electrochemical kinetics of the devices are quantified.
Self‐Polymerized Disordered Carbon Enabling High Sodium Storage Performance through Expanded Interlayer Spacing by Bound Sulfur Atoms
Authors: Li Wei , Wang Kangli , Cheng Shijie , Jiang Kai 
Published: August 2018

AbstractAn effective strategy to fabricate sulfur‐doped carbon with tunable doping sites is developed using a one‐step pyrolytic technique. Applied as Na‐storage anode, this sulfur‐doped carbon exhibits high reversible capacity, excellent rate capability (330 mAh g−1 at 0.02 A g−1 and 158 mAh g−1 at 5 A g−1), as well as superior durability (159 mAh g−1 over 10000 cycles at 2 A g−1 with 95.7 % retention). Experimental characterization and theoretical calculation reveal that interlayer C−S−C bonds not only expand the d002 spacing, but also provide an alternative pathway for electron transport. This improves Na+ ion intercalation/deintercalation capability and electronic conductivity.
Hierarchical Shell‐Like ZSM‐5 with Tunable Porosity Synthesized by using a Dissolution–Recrystallization Approach
Authors: Lin Junzhong , Cichocka Magdalena O. , Peng Fei , Yang Taimin , Sun Junliang 
Published: August 2018

AbstractZeolites have been widely used in various fields in industry, such as catalysis, separation, and adsorption, etc. The small pore size of the micropores in the zeolite could lead to severe diffusion resistance in mass transfer. Numerous efforts have been dedicated to imposing hierarchical pore systems into zeolites by using templates or leaching methods. Here, we report the synthesis of single‐crystalline hierarchical shell‐like ZSM‐5 by utilizing a dissolution–recrystallization post‐treatment on mesoporous ZSM‐5. Tetrapropylammonium hydroxide solution was used in the post‐treatment. The hierarchical porosity in the crystalline shell can be controlled by adding sodium cations into the synthesis system. The hierarchical shell‐like ZSM‐5 reported here shows higher catalytic activity in acetalization reactions containing bulky molecules.
Microporous N,P‐Codoped Graphitic Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction in Whole pH Range for Energy Conversion and Biosensing Dissolved Oxygen
Authors: Lin Deqing , Hu Chuangang , Chen Hao , Qu Jia , Dai Liming 
Published: August 2018

AbstractMicroporous N,P‐codoped graphitic nanosheets (N,P‐CMP‐1000) were synthesized by thermal annealing (1000 °C) of as‐synthesized conjugated microporous polymers (CMPs) in the presence of phytic acid, which can be used as an effective metal‐free electrocatalyst for the oxygen reduction reaction (ORR) for energy conversion. In the whole pH range (i.e. alkaline, acidic, and neutral solutions), the obtained N,P‐CMP‐1000 exhibits superior electrocatalytic activity for ORR with a low overpotential, high current density, and good stability. Furthermore, N,P‐CMP‐1000 can also be applied for electrochemically sensing dissolved oxygen (DO), with a high sensitivity (1.89 μA mg−1 L) and broad detection range (2.56 to 16.65 mg L−1) due to its good electrocatalytic performance towards ORR in neutral solution. In vitro cytotoxicity tests (CCK‐8 and Live/Dead Cell Double Staining Assay) of N,P‐CMP‐1000 extracts demonstrated its good biocompatibility to Human Corneal Epithelial Cells (HCEC), which shows its great potential as an eye‐wearable biosensor for sensing DO in tears.
Non‐Metal‐Heteroatom‐Doped Carbon Dots: Synthesis and Properties
Authors: Li Feng , Yang Dayong , Xu Huaping 
Published: August 2018

AbstractCarbon dots (CDs) are new materials with applications in bioimaging, optical devices, catalysis, and many other fields. Their advantages, such as ease of large‐scale preparation, low‐costing precursors, highly tunable photoluminescence, satisfactory biocompatibility, and photostability against photobleaching, make them competitive alternatives to conventional semiconductor‐based quantum dots and organic dyes. To overwhelm other luminescent materials in applications, their functionalities still need to be improved in spite of the abovementioned advantages. In recent years, it has been proven that heteroatom doping is an effective approach to improve the optical and electronic performance of CDs by tuning their carbon skeleton matrices and chemical structures. In this review, the development of non‐metal‐heteroatom‐doped CDs, including heteroatom categories, preparation methods, and physicochemical properties, are discussed. Progressive trends in heteroatom‐doped CDs are also discussed at the end of this review.
Reaction Selectivity in On‐Surface Chemistry by Surface Coverage Control—Alkyne Dimerization versus Alkyne Trimerization
Authors: Klaasen Henning , Liu Lacheng , Meng Xiangzhi , Held Philipp Alexander , Gao Hong‐Ying , Barton Dennis , Mück‐Lichtenfeld Christian , Neugebauer Johannes , Fuchs Harald , Studer Armido 
Published: August 2018

AbstractThis work reports the influence of molecular coverage in on‐surface C−C‐bond formation on reaction outcome. 6‐Ethynyl‐2‐naphthoic acid (ENA) was chosen as organic component and Ag(111) as substrate. The alkyne moiety in ENA can either react by dimerization to ENA dimers (Glaser coupling or hydroalkynylation) or cyclotrimerization to generate a benzene core as connecting moiety. Dimer formation is preferred at high surface coverage whereas trimerization is the major reaction pathway at low coverage. Mechanistic studies are provided.
Perovskite Oxide LaNiO3 Nanoparticles for Boosting H2 Evolution over Commercial CdS with Visible Light
Authors: Xu Junli , Sun Chunfang , Wang Zhaoyu , Hou Yidong , Ding Zhengxin , Wang Sibo 
Published: August 2018

AbstractLaNiO3/CdS heterojunction photocatalysts are constructed by compositing LaNiO3 nanoparticles with commercially available CdS, and are used for efficient photocatalytic splitting of H2O with visible light. The LaNiO3/CdS hybrids are characterized systematically using a series of physicochemical techniques. The photocatalytic activity of the perovskite hybrids is examined by H2 evolution with Na2S‐NaSO3 as the hole scavenger. The optimized LaNiO3/CdS sample without the assistance of any cocatalyst (e.g., Pt) delivers a high H2 production rate of 74 μmol h−1 (e.g., 3700 μmol h−1 g−1), which is substantially superior to the individual LaNiO3 and CdS. Besides, the composite photocatalyst also manifests high stability. The greatly improved H2 production performance of LaNiO3/CdS is attributed to the facilitated separation and transport of photoinduced charge carriers, as evidenced by photoelectrochemical (PEC) analyses, such as photoluminscence spectroscopy, transient photocurrent responses, and electrochemical impedance spectroscopy. Moreover, a probable photocatalytic mechanism of the H2 evolution reaction is proposed on the basis of the results of the catalysis evaluation and PEC tests.
Sodium Salicylate: An In‐Depth Thermal and Photophysical Study
Authors: Spielberg Eike T. , Campbell Paul S. , Szeto Kai C. , Mallick Bert , Schaumann Julian , Mudring Anja‐Verena 
Published: August 2018

AbstractSodium salicylate (2‐hydroxybenzoate) has been fully characterised by single‐crystal X‐ray diffraction (SCXRD), thermogravimetric analysis in combination with in operando FTIR spectroscopy and GC‐MS, as well as by UV/Vis absorption and photoluminescence spectroscopy backed up by DFT calculations. SCXRD revealed a layered crystal structure composed of ionic sheets formed by Na+–O contacts sandwiched between π‐stacked aromatic rings of the salicylate anion oriented perpendicular to the layer plane. Only weak van der Waals interactions hold the individual sheets together. No solid/solid or solid/liquid phase transitions were observed upon heating, but a three‐step decomposition was observed, with the first onset at 245 °C corresponding to concomitant release of CO2 and phenol. The UV/Vis absorption spectra show temperature‐dependent absorption bands at around 305 and/or 345 nm, which according to DFT calculations correspond to the absorption of the carboxylate or phenolate proton transfer species, respectively. In solution, indications of the phenolate species are found only in a very apolar solvent (cyclohexane). Because of excited‐state relaxation, emission always occurs from the phenolate structure, which explains the large Stokes shift.
Molecular Design towards Controlling Charge Transport
Authors: Awais Mohammad Ahmad , Cai Zhengxu , Zhang Na , Yu Luping 
Published: August 2018

AbstractOrganic electronics generally deals with bulk, statistically averaged electrical properties of organic materials. Single‐molecule electronic devices can then be viewed as linkers to these bulk properties. However, controlling charge transport in single‐molecule systems still remains a formidable task and has prevented proliferation of these systems from research laboratories to household electronics. This Concept article provides a general overview of the recent advances made by our group in the field. We will describe several concepts in designing molecular functions towards controlling charge transport through molecular systems. It should be noted, however, that this Concept article is by no means comprehensive and readers should look elsewhere for a more comprehensive picture of molecular electronics.
Novel Types of Hypermodified Fluorescent Phyllobilins from Breakdown of Chlorophyll in Senescent Leaves of Grapevine (Vitis vinifera)
Authors: Erhart Theresia , Mittelberger Cecilia , Liu Xiujun , Podewitz Maren , Li Chengjie , Scherzer Gerhard , Stoll Gertrud , Valls Josep , Robatscher Peter , Liedl Klaus R. , Oberhuber Michael , Kräutler Bernhard 
Published: August 2018

AbstractThe tetrapyrrolic chlorophyll catabolites (or phyllobilins, PBs) were analyzed in yellow fall leaves of the grape Chardonnay, a common Vitis vinifera white wine cultivar. The major fractions in leaf extracts of V. vinifera, tentatively assigned to PBs, were isolated and their structures elucidated. The dominant fraction is a dioxobilin‐type non‐fluorescent Chl‐catabolite of a previously observed type. Two less polar fluorescent PBs were characterized as a novel dioxobilin‐type fluorescent Chl‐catabolite with a bicyclo‐1′,6′‐glycosyl architecture, and its new fluorescent formyloxobilin‐type analogue. The discovery of persistent hypermodified fluorescent PBs with the architecture of bicyclo‐[17.3.1]‐PBs (bcPBs), suggests the activity of an unknown enzyme that forges the 20‐membered macroring at the tetrapyrrolic core of a fluorescent PB. bcPBs may play specific physiological roles in grapevine plants and represent endogenous anti‐infective agents, as found similarly for other organic bicyclo‐[n.3.1]‐1′,6′‐glycosyl derivatives.
Tenacic Acids: A New Class of Tenacious Binders to Metal Oxide Surfaces
Authors: Komati Rajesh , Mitchell Carl A. , LeBeaud Anastasia , Do Huy , Goloverda Galina Z. , Kolesnichenko Vladimir L. 
Published: August 2018

AbstractThe backbone of 2‐hydroxyisophthalic acid was identified as a potential metal oxide anchor because of the perfect alignment of all three of its donor groups for binding to inorganic surfaces. It can therefore be used in the design of organic linkers for metal oxide based hybrid materials. Optimized and scalable methods for the synthesis of 2‐hydroxyisophthalic acid (1) and its 5‐substituted derivatives: 5‐bromo‐ (2), 5‐sulfooxy‐ (3), 5‐hydroxy‐ (4), and 5‐PEG600 (5) are presented. Dynamic light scattering (DLS) demonstrated that compound 2 inhibits Fe(OH)3 precipitation when FeIII aqueous solutions are titrated with NaOH, while similar titrations in the presence of the structurally‐related isophthalic and salicylic acids, both missing the third donor group, show turbidity at pHs as low as 2.3 and 3.5, respectively. The adduct synthesized from 4.5 nm γ‐Fe2O3 nanoparticles and 5 is water‐, alcohol‐ and CH2Cl2‐soluble, and forms stable aqueous colloids in the pH range of 4.4–8.7. Moreover, at a pH close to neutral these colloids survive at 100 °C, demonstrating the high practicality of 2‐hydroxyisophthalic acid for nanoparticulate inorganic/organic hybrid material design.
Soluble Hetero‐Polyoxovanadates and Their Solution Chemistry Analyzed by Electrospray Ionization Mass Spectrometry
Authors: Warzok Ulrike , Mahnke Lisa K. , Bensch Wolfgang 
Published: August 2018

AbstractPolyoxometalates (POMs) are an intriguing class of compounds due to their tremendous structural variety and the wide spectrum of resulting properties, which make them interesting for applications in fields such as catalysis, material science or nanotechnology. Their ability to form large supramolecular architectures by self‐assembly offers an entry to complex, functional systems. After an introduction into the structure and synthesis of POMs of the early transition metals, recently discovered water‐soluble antimonato polyoxovanadates (Sb‐POVs) and the investigation of their chemical reactivity are discussed. Electrospray ionization mass spectrometry (ESI‐MS) is presented as an analytical technique suitable to investigate the structure of complex POM assemblies in solution and to probe the underlying reactivity and formation mechanisms. This Minireview highlights the first studies on the soluble Sb‐POVs and how the knowledge of their reactivity obtained by ESI‐MS has fostered the syntheses of numerous novel Sb‐POV compounds.
The First Examples of Lithium‐Containing Mixed‐Alkali Strontium Borates with Different Dimensional Anionic Architectures and Short Cutoff Edges
Authors: Ma Ruru , Yang Yun , Hu Cong , Yang Zhihua , Pan Shilie 
Published: August 2018

AbstractThree new mixed‐alkali strontium borates, Li2KSr6(BO3)5, Li2Rb7Sr24(BO3)19, and Li2Rb2SrB18O30, have been synthesized by the high‐temperature solution method by adjusting the molar ratios of the reactants. They represent the first examples of lithium‐containing mixed‐alkali strontium borates. The structures of the three compounds show different dimensional anionic architectures, with Li2KSr6(BO3)5 and Li2Rb7Sr24(BO3)19 possessing isolated BO3 units, whereas Li2Rb2SrB18O30 has three‐dimensional (3D)
open frameworks with three types of channels occupied by the strontium and rubidium atoms. Interestingly, Li2KSr6(BO3)5 is the first example of a
chain composed of LiO5 linked through the sharing of vertexes and edges. However, in Li2Rb7Sr24(BO3)19, isolated LiO3 units can be observed, which is also rare in borates. Detailed analysis and comparisons of the structures of the anhydrous mixed‐alkali‐ and alkaline‐earth‐metal borates and nine‐polymeric fundamental building blocks have been made. Furthermore, Li2Rb7Sr24(BO3)19 and Li2Rb2SrB18O30 present short cutoff edges (<190 nm), which was confirmed by the UV/Vis/NIR diffuse reflectance spectra. These attributes make them attractive for deep‐UV optical materials.
Synthesis of Thin‐Film Metal Pyrites by an Atomic Layer Deposition Approach
Authors: Wang Jue , Guo Zheng , Xiong Wei , Wang Xinwei 
Published: August 2018

AbstractLate 3d transition metal disulfides (MS2, M=Fe, Co, Ni, Cu, Zn) can crystallize in an interesting cubic‐pyrite structure, in which all the metal cations are in a low‐spin electronic configuration with progressive increase of the eg electrons for M=Fe–Zn. These metal pyrite compounds exhibit very diverse and intriguing electrical and magnetic properties, which have stimulated considerable attention for various applications, especially in cutting‐edge energy conversion and storage technologies. The synthesis of the metal pyrites is certainly very important, because highly controllable, reproducible, and reliable synthesis methods are virtually essential for both fundamental materials research and practical engineering. In this Concept, a new approach of (plasma‐assisted) atomic layer deposition (ALD) to synthesize the thin‐film metal pyrites (FeS2, CoS2, NiS2) is introduced. The ALD synthesis approach allows for atomic‐precision control over film composition and thickness, excellent film uniformity and conformality, and superior process reproducibility, and therefore it is of high promise for uniformly conformal metal pyrite thin‐film coatings on complex 3D structures in general. Details and implications of this ALD approach are discussed in this Concept, mainly from a conceptual perspective, and it is envisioned that, with this new ALD synthesis approach, a significant amount of new studies will be enabled on both the fundamentals, and novel applications of the metal pyrite materials.
DNA–RNA Hybrid Quadruplexes Reveal Interactions that Favor RNA Parallel Topologies
Authors: Haase Linn , Dickerhoff Jonathan , Weisz Klaus 
Published: August 2018

AbstractA DNA G‐quadruplex adopting a (3+1)‐hybrid structure was substituted at its 5′‐tetrad by riboguanosine (rG) analogs. Incorporation of anti‐favoring rG at appropriate syn‐positions of the 5′‐outer tetrad induced conformational rearrangements to yield a quadruplex featuring a 5′‐tetrad with reversed polarity. A high‐resolution structure of a disubstituted quadruplex variant as well as direct NMR experimental evidence reveals a non‐conventional C−H⋅⋅⋅O hydrogen bond in a medium groove between the 2′‐OH of an rG residue adopting a C2′‐endo sugar pucker and H8 of a 3′‐neighboring anti‐G residue. In contrast, a C3′‐endo sugar conformation for another guanine ribonucleotide prevents formation of a corresponding hydrogen bond but relocates its 2′‐OH substituent from the quadruplex narrow groove into a medium groove. Both the formation of favorable CHO hydrogen bridges and unfavorable interactions of the 2′‐hydroxyl group in a narrow groove will promote RNA folding into a parallel topology featuring all‐anti core residues and four grooves of medium size.
Multipurpose and Durable Adhesive Hydrogel Assisted by Adenine and Uracil from Ribonucleic Acid
Authors: Liu Xin , Zhang Qin , Li Kunming , Duan Lijie , Gao Guanghui 
Published: August 2018

AbstractNucleobase pairs of adenine and uracil (A‐U) from ribonucleic acid are of particular interest for various promising material properties. Herein, a novel polyacrylamide hydrogel with adhesive properties that are assisted by adenine and uracil has been designed and investigated. The incorporation of adenine and uracil enables the formation of a polyacrylamide hydrogel with remarkable adhesive behaviour with various materials including polytetrafluoroethylene (PTFE), plastics, rubber, glasses, metal, ceramics and wood. Moreover, the adhesive hydrogel can easily and directly adhere to humid biological tissues without any extra process, including heart, liver, spleen, lung, kidney, bone and muscle of mouse. More impressively, even after repeated peeling tests (10×), the AU‐mediated polyacrylamide hydrogel still exhibits excellent durable adhesion for various materials. From mechanical contact tests, the adhesion energy of the A‐U adhesive hydrogel is 47.9 J m−2, which is nearly nine times that of polyacrylamide hydrogel (5.3 J m−2). The 90° peeling strength for aluminium, titanium, silica rubbers, glasses, PTFE and hogskin is 518, 645, 445, 396, 349, and 119 N m−1, respectively. The multipurpose and durable adhesive behaviour of hydrogels assisted by adenine and uracil indicated the promise of nucleobase pairs from ribonucleic acid for the future development of adhesive materials.
Chain‐Conformation‐Directed Polymerization Cyclization for Effective Synthesis of Macrocycles in Bulk
Authors: Cao Kai , Peng Liao , Zhu Junli , Feng Anchao , Liu Dapeng , Worku Aklilu , Liu Senyang , Lin Jiaping , Yuan Jinying , Wang Xiaosong 
Published: August 2018

AbstractBiological cyclization is highly efficient, and this can be attributed to the conformation of the backbone of the biopolymer. Taking advantage of metal‐coordination geometry, we developed a method for conformation‐directed polymerization cyclization through rational design of metal carbonyl monomers that could be used to produce cyclic macromolecules, even in bulk. PFpR [PFp=(PPh2(CH2)3Cp)Fe(CO)2 with the phosphine group tethered on the cyclopentadiene (Cp) ring; R=CH3 or (CH2)5CH3] was designed and synthesized for migration insertion polymerization to generate P(PFpR) with the polymer backbone containing Cp−Fe bonds. Growth of the backbone led to a cyclic conformation with close end‐to‐end distances, which facilitated the cyclization. This conformation‐directed cyclization was attributed to the piano‐stool metal‐coordination geometry of the repeating units and the low rotational barrier of the Cp−Fe bonds in the backbone. The produced macrocycles, which contain a metal carbonyl coordination structure in their backbones, are rigid, unlike many organic macrocycles. The macrocycles thus have a large excluded volume. This new type of metal carbonyl macrocycle will be of interest as a building block for supramolecular chemistry and in the exploration of novel materials.
Synthesis and Characterization of the First Tin Fluoride Borate Sn3[B3O7]F with Second Harmonic Generation Response
Authors: Schönegger Sandra , Jantz Stephan G. , Saxer Andreas , Bayarjargal Lkhamsuren , Winkler Björn , Pielnhofer Florian , Höppe Henning A. , Huppertz Hubert 
Published: August 2018

AbstractThe new non‐centrosymmetric tin fluoride borate Sn3[B3O7]F was synthesized hydrothermally, and was characterized by single‐crystal and powder X‐ray diffraction, vibrational spectroscopy, DFT calculations, second harmonic generation (SHG) measurements, thermogravimetry, and differential scanning calorimetry. Its SHG response is about 12 times that of quartz. The compound crystallizes in the non‐centrosymmetric orthorhombic space group Pna21 with lattice parameters a=922.4(2), b=769.8(4), and c=1221.9(6) pm (Z=4). Characteristic for the structure are isolated B3O7 moieties, consisting of two corner‐sharing BO3 units and one BO4 tetrahedron. These occupy half of the octahedral voids of a slightly distorted hexagonal closest packing of Sn2+ atoms, with [SnF]+ units in the other half of the octahedral voids. Sn3[B3O7]F is transparent over a wide spectral range with a UV cut‐off edge at about 263 nm.