bluuebunny/crossref_metadata_2025_split huggingface dataset:
Versatile Relay and Cooperative Palladium(0) N‐Heterocyclic Carbene/Copper(I) N‐Heterocyclic Carbene Catalysis for the Synthesis of Tri‐ and Tetrasubstituted Alkenes
Authors: Lesieur Mathieu , Bidal Yannick D. , Lazreg Faïma , Nahra Fady , Cazin Catherine S. J. 
Published: June 2015

AbstractTwo new and efficient dual catalytic procedures for the synthesis of tri‐ and tetrasubstituted alkenes using aryl bromides and chlorides are reported. The formation of these vinyl arenes occurs independently in a one‐pot relay and a one‐pot cooperative procedure using well‐defined Pd and Cu N‐heterocyclic carbene (NHC) complexes. Mechanistic studies were performed to elucidate the key role of the solvent in each procedure as well as the formation of the key intermediate, [Cu(alkenylboron)(NHC)], which allows transmetalation with the Pd‐NHC co‐catalyst in the cooperative catalysis.
Design of Carbon‐Encapsulated Fe3O4 Nanocatalyst with Enhanced Performance for Fischer–Tropsch Synthesis
Authors: Tu Jun‐ling , Ding Ming‐yue , Zhang Qian , Zhang Yu‐lan , Wang Chen‐guang , Wang Tie‐jun , Ma Long‐long , Li Xin‐jun 
Published: June 2015

AbstractFischer–Tropsch synthesis (FTS), an important process for the production of liquid fuels and chemicals from syngas derived from coal and biomass, is receiving renewed interest for both industrial and academic applications. Adjusting the product distribution of hydrocarbons is the focus of research in this field. Herein, a novel carbon‐encapsulated Fe3O4 nanocatalyst was synthesized by a simple one‐step solvothermal method without calcination. The catalyst exhibited excellent catalytic activity and higher selectivity for C5–12 hydrocarbons (gasoline range products) than the traditional Fe2O3 catalyst. A 45.25 % C5–12 selectivity was obtained for Fe3O4@C, which is close to the maximum value from the Anderson–Schulz–Flory distribution.
A Viable Hydrogen Storage and Release System Based on Cesium Formate and Bicarbonate Salts: Mechanistic Insights into the Hydrogen Release Step
Authors: Sordakis Katerina , Dalebrook Andrew F. , Laurenczy Gábor 
Published: June 2015

AbstractAqueous solutions of cesium formate and bicarbonate represent an effective hydrogen storage–delivery couple that undergoes either release or take up of hydrogen in the presence of {RuCl2(mTPPTS)2}2 (TPPTS=triphenylphosphine trisulfonate) and excess mTPPTS ligand, with no other additives required. Cesium salt solutions offer the advantage of improved volumetric and gravimetric H2 density compared to their sodium and potassium analogs, owing to their high water solubility. Details of the equilibrium between formate and bicarbonate, which constitutes an important parameter for the applicability of this H2 storage/release cycle, were determined. H2 production is readily tunable by controlling the operating pressure. This behavior was also rationalized through the identification of catalytic intermediates under various conditions. High concentration formate and bicarbonate solutions were used during the tests and the bidirectional catalytic system could be recycled without loss of activity or replacement of solvent. A tentative mechanism is proposed for the formate dehydrogenation step. Among the identified hydride species, the pentacoordinated [RuH(H2O)(TPPTS)3] complex was indispensable for promoting the formate dehydrogenation reaction.
Macrocyclic Gd3+ Complexes with Pendant Crown Ethers Designed for Binding Zwitterionic Neurotransmitters
Authors: Oukhatar Fatima , Meudal Hervé , Landon Céline , Logothetis Nikos K. , Platas‐Iglesias Carlos , Angelovski Goran , Tóth Éva 
Published: June 2015

AbstractA series of Gd3+ complexes exhibiting a relaxometric response to zwitterionic amino acid neurotransmitters was synthesized. The design concept involves ditopic interactions 1) between a positively charged and coordinatively unsaturated Gd3+ chelate and the carboxylate group of the neurotransmitters and 2) between an azacrown ether appended to the chelate and the amino group of the neurotransmitters. The chelates differ in the nature and length of the linker connecting the cyclen‐type macrocycle that binds the Ln3+ ion and the crown ether. The complexes are monohydrated, but they exhibit high proton relaxivities (up to 7.7 mM−1 s−1 at 60 MHz, 310 K) due to slow molecular tumbling. The formation of ternary complexes with neurotransmitters was monitored by 1H relaxometric titrations of the Gd3+ complexes and by luminescence measurements on the Eu3+ and Tb3+ analogues at pH 7.4. The remarkable relaxivity decrease (≈80 %) observed on neurotransmitter binding is related to the decrease in the hydration number, as evidenced by luminescence lifetime measurements on the Eu3+ complexes. These complexes show affinity for amino acid neurotransmitters in the millimolar range, which can be suited to imaging concentrations of synaptically released neurotransmitters. They display good selectivity over non‐amino acid neurotransmitters (acetylcholine, serotonin, and noradrenaline) and hydrogenphosphate, but selectivity over hydrogencarbonate was not achieved.
How to Make Weak Noncovalent Interactions Stronger
Authors: Xu Jiang‐Fei , Chen Linghui , Zhang Xi 
Published: June 2015

AbstractBy employing noncovalent interactions, chemists have constructed a variety of molecular aggregates with well‐defined structures and fascinating properties. In fabricating stable and large molecular assemblies, noncovalent interactions with high binding strength are needed. This Concept summarizes some strategies to modify and optimize the structures of building blocks for making weak noncovalent interactions stronger. The strategies include: 1) Preorganization of binding sites; 2) spatial confinement effects; 3) multivalent enhancement; 4) synergistic binding with multiple forces. Examples of the fabrication of supramolecular architectures by utilizing these strategies are presented and discussed. Guidance is offered in the construction and fabrication of stable molecular assemblies and supramolecular materials.
Electrochemical Properties of Fiber‐in‐Tube‐ and Filled‐Structured TiO2 Nanofiber Anode Materials for Lithium‐Ion Batteries
Authors: Cho Jung Sang , Hong Young Jun , Kang Yun Chan 
Published: June 2015

AbstractPhase‐pure anatase TiO2 nanofibers with a fiber‐in‐tube structure were prepared by the electrospinning process. The burning of titanium‐oxide‐carbon composite nanofibers with a filled structure formed as an intermediate product under an oxygen atmosphere produced carbon‐free TiO2 nanofibers with a fiber‐in‐tube structure. The sizes of the nanofiber core and hollow nanotube were 140 and 500 nm, respectively. The heat treatment of the electrospun nanofibers at 450 and 500 °C under an air atmosphere produced grey and white filled‐structured TiO2 nanofibers, respectively. The initial discharge capacities of the TiO2 nanofibers with the fiber‐in‐tube and filled structures and the commercial TiO2 nanopowders were 231, 134, and 223 mA h g−1, respectively, and their corresponding charge capacities were 170, 100, and 169 mA h g−1, respectively. The 1000th discharge capacities of the TiO2 nanofibers with the fiber‐in‐tube and filled structures and the commercial TiO2 nanopowders were 177, 64, and 101 mA h g−1, respectively, and their capacity retentions measured from the second cycle were 89, 82, and 52 %, respectively. The TiO2 nanofibers with the fiber‐in‐tube structure exhibited low charge transfer resistance and structural stability during cycling and better cycling and rate performances than the TiO2 nanofibers with filled structures and the commercial TiO2 nanopowders.
Palladium‐Catalyzed Mono‐α‐arylation of Acetone at Room Temperature
Authors: MacQueen Preston M. , Chisholm Alicia J. , Hargreaves Breanna K. V. , Stradiotto Mark 
Published: June 2015

AbstractThe first examples of acetone mono‐α‐arylation at room temperature are described, enabled by use of a [Pd(cinnamyl)Cl]2/JosiPhos catalyst system. (Hetero)aryl chloride, bromide, and iodide electrophiles featuring or lacking ortho‐substitution, and comprising a range of functionalities (e.g., alkoxy, cyano, fluoro, trifluoromethyl, or alkenyl) and heteroaryl motifs (e.g., pyrrole, pyridine, isoquinoline, quinoline, quinaldine, (benzo)thiophene, benzothiazole, or benzodioxole) were successfully accommodated. Proof‐of‐principle experiments confirm that other (hetero)aryl methyl ketones can also be employed in such room temperature mono‐α‐arylations. The established substrate scope is the most extensive reported to date for acetone mono‐α‐arylation under any conditions, and more generally represents the first room temperature ketone mono‐α‐arylations employing a structurally diverse set of (hetero)aryl chlorides.
Moving toward Ylide‐Stabilized Carbenes
Authors: Borthakur Bitupon , Phukan Ashwini K. 
Published: June 2015

AbstractThe effect of ylide substitution at the α position to the carbene carbon (Cc) atom on the stability and σ‐donating ability of a number of cyclic carbenes has been studied theoretically. The stabilities of all of the carbenes were investigated from an evaluation of their singlet–triplet energy gaps and stabilization energies. All carbenes were found to have a stable singlet state. The energy of the σ‐symmetric lone‐pair orbital at the Cc atom increases as a result of the introduction of ylide centers near to the Cc atom. This indicates an enhanced σ‐donating ability of the ylide‐containing carbenes. The calculated carbonyl‐stretching frequencies of the corresponding rhodium complexes, proton affinities, and nucleophilicity index values correlate well with the σ basicity of the carbenes.
Pyridyl‐Functionalised 3H‐1,2,3,4‐Triazaphospholes: Synthesis, Coordination Chemistry and Photophysical Properties of Low‐Coordinate Phosphorus Compounds
Authors: Sklorz Julian A. W. , Hoof Santina , Rades Nadine , De Rycke Nicolas , Könczöl László , Szieberth Dénes , Weber Manuela , Wiecko Jelena , Nyulászi László , Hissler Muriel , Müller Christian 
Published: June 2015

AbstractNovel conjugated, pyridyl‐functionalised triazaphospholes with eithertBu or SiMe3substituents at the 5‐position of the N3PC heterocycle have been prepared by a [3+2] cycloaddition reaction and compared with structurally related, triazole‐based systems. Photoexcitation of the 2‐pyridyl‐substituted triazaphosphole gives rise to a significant fluorescence emission with a quantum yield of up to 12 %. In contrast, the all‐nitrogen triazole analogue shows no emission at all. DFT calculations indicate that the 2‐pyridyl substituted systems have a more rigid and planar structure than their 3‐ and 4‐pyridyl isomers. Time‐dependent (TD) DFT calculations show that only the 2‐pyridyl‐substituted triazaphosphole exhibits similar planar geometry, with matching conformational arrangements in the lowest energy excited state and the ground state; this helps to explain the enhanced emission intensity. The chelating P,N‐hybrid ligand forms a ReIcomplex of the type [(N^N)Re(CO)3Br] through the coordination of nitrogen atom N2to the metal centre rather than through the phosphorus donor. Both structural and spectroscopic data indicate substantial π‐accepting character of the triazaphosphole, which is again in contrast to that of the all‐nitrogen‐containing triazoles. The synthesis and photophysical properties of a new class of phosphorus‐containing extended π systems are described.
Mechanistic Insights on the Iodine(III)‐Mediated α‐Oxidation of Ketones
Authors: Beaulieu Samuel , Legault Claude Y. 
Published: June 2015

AbstractThe synthesis of α‐substituted carbonyl compounds is of great importance due to their ubiquity in both natural and man‐made biologically active compounds. The field of hypervalent iodine chemistry has been a great contributor to access these molecules. For example, the α‐oxidation of carbonyl compounds has been one of the most investigated iodine(III)‐mediated stereoselective transformations. Yet, it is also the transformation that has met the most challenge in terms of achieving high stereoselectivities. The different mechanistic pathways of the iodine(III)‐mediated α‐tosyloxylation of ketones have been investigated. The calculations suggest an unprecedented iodine(III)‐promoted enolization process. Indications that iodonium intermediates could serve as proficient Lewis acids are reported. This concept could have broad impact and foster new developments in the field of hypervalent iodine chemistry.
Tunable Molecular Logic Gates Designed for Imaging Released Neurotransmitters
Authors: Klockow Jessica L. , Hettie Kenneth S. , Secor Kristen E. , Barman Dipti N. , Glass Timothy E. 
Published: June 2015

AbstractTunable dual‐analyte fluorescent molecular logic gates (ExoSensors) were designed for the purpose of imaging select vesicular primary‐amine neurotransmitters that are released from secretory vesicles upon exocytosis. ExoSensors are based on the coumarin‐3‐aldehyde scaffold and rely on both neurotransmitter binding and the change in environmental pH associated with exocytosis to afford a unique turn‐on fluorescence output. A pH‐functionality was directly integrated into the fluorophore π‐system of the scaffold, thereby allowing for an enhanced fluorescence output upon the release of labeled neurotransmitters. By altering the pH‐sensitive unit with various electron‐donating and ‐withdrawing sulfonamide substituents, we identified a correlation between the pKa of the pH‐sensitive group and the fluorescence output from the activated fluorophore. In doing so, we achieved a twelvefold fluorescence enhancement upon evaluating the ExoSensors under conditions that mimic exocytosis. ExoSensors are aptly suited to serve as molecular imaging tools that allow for the direct visualization of only the neurotransmitters that are released from secretory vesicles upon exocytosis.
Comparative Study of Halogen‐ and Hydrogen‐Bond Interactions between Benzene Derivatives and Dimethyl Sulfoxide
Authors: Zheng Yan‐Zhen , Deng Geng , Zhou Yu , Sun Hai‐Yuan , Yu Zhi‐Wu 
Published: June 2015

AbstractThe halogen bond, similar to the hydrogen bond, is an important noncovalent interaction and plays important roles in diverse chemistry‐related fields. Herein, bromine‐ and iodine‐based halogen‐bonding interactions between two benzene derivatives (C6F5Br and C6F5I) and dimethyl sulfoxide (DMSO) are investigated by using IR and NMR spectroscopy and ab initio calculations. The results are compared with those of interactions between C6F5Cl/C6F5H and DMSO. First, the interaction energy of the hydrogen bond is stronger than those of bromine‐ and chlorine‐based halogen bonds, but weaker than iodine‐based halogen bond. Second, attractive energies depend on 1/rn, in which n is between three and four for both hydrogen and halogen bonds, whereas all repulsive energies are found to depend on 1/r8.5. Third, the directionality of halogen bonds is greater than that of the hydrogen bond. The bromine‐ and iodine‐based halogen bonds are strict in this regard and the chlorine‐based halogen bond only slightly deviates from 180°. The directional order is iodine‐based halogen bond>bromine‐based halogen bond>chlorine‐based halogen bond>hydrogen bond. Fourth, upon the formation of hydrogen and halogen bonds, charge transfers from DMSO to the hydrogen‐ and halogen‐bond donors. The CH3 group contributes positively to stabilization of the complexes.
Antagonistic Functionalized Nucleation and Oxidative Degradation in Combustive Formation of Pyrene‐Based Clusters Mediated by Triplet O and O2: Theoretical Study
Authors: Maranzana Andrea , Tonachini Glauco 
Published: June 2015

AbstractPolycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanoparticles can be oxidized right from their inception and all through their growth. Oxidation can also promote their degradation. This modelistic density functional theory (DFT) study explores, in a descriptive manner, if oxidation can mediate the earliest stages of nucleation (“functionalized nucleation”), though contrasted by mass declension triggered by oxidation itself. Initial O (3P) attack onto pyrene, chosen as a representative of a generic small PAH or nascent soot lamella, forms an oxyl diradical intermediate that can evolve into an open‐shell epoxide, phenol, or ketone species or, alternatively, undergo mass depletion from the beginning (without impeding further additions). Open‐shell intermediates can add O or O2 (3Σg−) and ethyne, in any order, and open the way, through formation of carbon and oxygen bridges, to the addition of a second molecule of pyrene, whereas formation of direct carbon–carbon links between the two PAH‐like parts might also occur.
Highly Stable Na2/3(Mn0.54Ni0.13Co0.13)O2 Cathode Modified by Atomic Layer Deposition for Sodium‐Ion Batteries
Authors: Kaliyappan Karthikeyan , Liu Jian , Lushington Andrew , Li Ruying , Sun Xueliang 
Published: June 2015

AbstractFor the first time, atomic layer deposition (ALD) of Al2O3 was adopted to enhance the cyclic stability of layered P2‐type Na2/3(Mn0.54Ni0.13Co0.13)O2 (MNC) cathodes for use in sodium‐ion batteries (SIBs). Discharge capacities of approximately 120, 123, 113, and 105 mA h g−1 were obtained for the pristine electrode and electrodes coated with 2, 5, and 10 ALD cycles, respectively. All electrodes were cycled at the 1C discharge current rate for voltages between 2 and 4.5 V in 1 M NaClO4 electrolyte. Among the electrodes tested, the Al2O3 coating from 2 ALD cycles (MNC‐2) exhibited the best electrochemical stability and rate capability, whereas the electrode coated by 10 ALD cycles (MNC‐10) displayed the highest columbic efficiency (CE), which exceeded 97 % after 100 cycles. The enhanced electrochemical stability observed for ALD‐coated electrodes could be a result of the protection effects and high band‐gap energy (Eg=9.00 eV) of the Al2O3 coating layer. Additionally, the metal‐oxide coating provides structural stability against mechanical stresses occurring during the cycling process. The capacity, cyclic stability, and rate performance achieved for the MNC electrode coated with 2 ALD cycles of Al2O3 reveal the best results for SIBs. This study provides a promising route toward increasing the stability and CE of electrode materials for SIB application.
Molecular Engineering of Organic Dyes with a Hole‐Extending Donor Tail for Efficient All‐Solid‐State Dye‐Sensitized Solar Cells
Authors: Lu Jianfeng , Chang Yu‐Cheng , Cheng Hsu‐Yang , Wu Hui‐Ping , Cheng Yibing , Wang Mingkui , Diau Eric Wei‐Guang 
Published: June 2015

AbstractWe report a new concept for the design of metal‐free organic dyes (OD5–OD9) with an extended donor–π–acceptor (D–π–A) molecular framework, in which the donor terminal unit is attached by a hole‐extending side chain to retard back electron transfer and charge recombination; the π‐bridge component contains varied thiophene‐based substituents to enhance the light‐harvesting ability of the device. The best dye (OD9) has a D–A–π–A configuration with the hexyloxyphenylthiophene (HPT) side chain as a hole‐extension component and a benzothiadiazole (BTD) internal acceptor as a π‐extension component. The co‐sensitization of OD9 with the new porphyrin dye LW24 enhanced the light‐harvesting ability to 800 nm; thus, a power conversion efficiency 5.5 % was achieved. Photoinduced absorption (PIA) and transient absorption spectral (TAS) techniques were applied to account for the observed trend of the open‐circuit voltage (VOC) of the devices. This work provides insights into the molecular design, photovoltaic performance, and kinetics of charge recombination.
Teens that fear screams: A comparison of fear conditioning, extinction, and reinstatement in adolescents and adults
Authors: Den Miriam Liora , Graham Bronwyn M. , Newall Carol , Richardson Rick 
Published: June 2015

ABSTRACTThis study investigated differences between adolescents and adults on fear conditioning, extinction, and reinstatement (i.e., the recovery of conditioned fear following re‐exposure to the unconditioned stimulus [US] post‐extinction). Participants underwent differential conditioning (i.e., the Screaming Lady) where one neutral face (CS+) was followed by the same face expressing fear and a loud scream (US) while another neutral face (CS−) remained neutral. Extinction involved non‐reinforced presentations of both CSs, after which participants were reinstated (2xUSs) or not. On two self‐report measures, both ages showed conditioning, good extinction learning and retention, and reinstatement‐induced relapse. However, only adolescents showed conditioning, extinction, and reinstatement on the eye tracking measure; relapse on this measure could not be assessed in adults given they did not show initial conditioning. Lastly, higher levels of depression predicted stronger conditioning and weaker extinction in adolescents only. These findings are discussed in terms of their implications for adolescent anxiety disorders. © 2015 Wiley Periodicals, Inc. Dev Psychobiol 57: 818–832, 2015.
Potential of Gelatin‐Zinc Oxide Nanocomposite as Ascorbic Acid Sensor
Authors: Rawat Kamla , Sharma Anshu , Solanki Pratima R. , Bohidar H. B. 
Published: June 2015

AbstractWe report on the studies relating to fabrication of gelatin B (GB) and zinc oxide (ZnO) based nanocomposite (GB‐ZnO) film deposited on indium‐tin‐oxide (ITO) glass plate, and used for the immobilization of ascorbate oxidase (AsOx) which was further used for ascorbic acid (AA) detection. The structural and morphological studies of GB‐ZnO, and AsOx/GB‐ZnO/ITO bioelectrodes were carried out using XRD, SEM and FTIR techniques. This bioelectrode showed a broad range of linearity (5–500 mg/dL), low detection limit (1 mg/dL), higher sensitivity (0.106 µA mg/dLcm−2) and low value of the apparent MichaelisMenten constant (Kmapp=0.35 mg/dL) for AA. Efforts are being made to utilize this electrode for sensing AA in real samples in a bid to develop a strip based sensor.
A Layer‐by‐Layer Biosensing Architecture Based on Polyamidoamine Dendrimer and Carboxymethylcellulose‐Modified Graphene Oxide
Authors: Borisova Boryana , Ramos Javier , Díez Paula , Sánchez Alfredo , Parrado Concepción , Araque Elena , Villalonga Reynaldo , Pingarrón José M. 
Published: June 2015

AbstractA novel nanostructured architecture for the construction of electrochemical enzyme biosensors is here described. It implies the electrostatic layer‐by‐layer assembly of four‐generation ethylenediamine core polyamidoamine G‐4 dendrimers on glassy carbon electrodes coated with a graphene oxide‐carboxymethylcellulose hybrid nanomaterial. This modified surface was further employed for the covalent immobilization of the model enzyme tyrosinase through a glutaraldehyde‐mediated cross‐linking. The prepared enzyme electrode allowed the amperometric detection of catechol in the 2–400 nM range. The biosensor showed excellent analytical performance with high sensitivity of 6.3 A/M and low detection limit of 0.9 nM. The enzyme electrode retained over 93 % of the initial activity after 40 days at 4 °C.
Direct Electrochemistry of Glucose Oxidase at Reduced Graphene Oxide and β‐Cyclodextrin Composite Modified Electrode and Application for Glucose Biosensing
Authors: Palanisamy Selvakumar , Devasenathipathy Rajkumar , Chen Shen‐Ming , Ajmal Ali M. , Karuppiah Chelladurai , Balakumar V. , Prakash P. , Elshikh Mohamed S. , Al‐Hemaid Fahad M. A. 
Published: June 2015

AbstractA simple glucose biosensor has been developed based on direct electrochemistry of glucose oxidase (GOx) immobilized on the reduced graphene oxide (RGO) and β‐cyclodextrin (CD) composite. A well‐defined redox couple of GOx appears with a formal potential of ∼−0.459 V at RGO/CD composite. A heterogeneous electron transfer rate constant (Ks) has been calculated for GOx at RGO/CD as 3.8 s−1. The fabricated biosensor displays a wide response to glucose in the linear concentrations range from 50 µM to 3.0 mM. The sensitivity and limit of detection of the biosensor is estimated as 59.74 µA mM−1 cm−2 and 12 µM, respectively.