bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of Graphene by Using an Intense Cavitation Field in a Pressurized Ultrasonic Reactor
Authors: Štengl Václav 
Published: September 2012

AbstractA new and efficient method to produce a large quantity of high‐quality and non‐oxidized graphene flakes from powdered natural graphite by using a high‐intensity cavitation field in a pressurized ultrasonic reactor is demonstrated. TEM and selected‐area electron diffraction (SAED) confirmed the ordered graphite crystal structure of graphene. Atomic force microscopy (AFM) was used to examine the thickness of the graphene sheets. The delamination (exfoliation) of natural graphite in the liquid phase depends on the physical effects of ultrasound, which break down the 3D graphite structure into a 2D graphene structure. The prepared graphene is of high purity and without defects because no strongly oxidizing chemicals are used and no toxic products result. TEM shows that graphene nanosheets were produced with sizes in the range of tens to hundreds of square nanometers; these nanosheets were smooth and without any ripples and corrugations. High‐resolution TEM (HRTEM) and SAED analysis confirmed that the products were graphene nanosheets.
Mechanism of the Pd‐catalyzed Decarboxylative Allylation of α‐Imino Esters: Decarboxylation via Free Carboxylate Ion
Authors: Li Zhe , Jiang Yuan‐Ye , Yeagley Andrew A. , Bour James P. , Liu Lei , Chruma Jason J. , Fu Yao 
Published: September 2012

AbstractThe Pd‐catalyzed decarboxylative allylation of α‐(diphenylmethylene)imino esters (1) or allyl diphenylglycinate imines (2) is an efficient method to construct new C(sp3)C(sp3) bonds. The detailed mechanism of this reaction was studied by theoretical calculations [ONIOM(B3LYP/LANL2DZ+p:PM6)] combined with experimental observations. The overall catalytic cycle was found to consist of three steps: oxidative addition, decarboxylation, and reductive allylation. The oxidative addition of 1 to [(dba)Pd(PPh3)2] (dba=dibenzylideneacetone) produces an allylpalladium cation and a carboxylate anion with a low activation barrier of +9.1 kcal mol−1. The following rate‐determining decarboxylation proceeds via a solvent‐exposed α‐imino carboxylate anion rather than an O‐ligated allylpalladium carboxylate with an activation barrier of +22.7 kcal mol−1. The 2‐azaallyl anion generated by this decarboxylation attacks the face of the allyl ligand opposite to the Pd center in an outer‐sphere process to produce major product 3, with a lower activation barrier than that of the minor product 4. A positive linear Hammett correlation [ρ=1.10 for the PPh3 ligand] with the observed regioselectivity (3 versus 4) supports an outer‐sphere pathway for the allylation step. When Pd combined with the bis(diphenylphosphino)butane (dppb) ligand is employed as a catalyst, the decarboxylation still proceeds via the free carboxylate anion without direct assistance of the cationic Pd center. Consistent with experimental observations, electron‐withdrawing substituents on 2 were calculated to have lower activation barriers for decarboxylation and, thus, accelerate the overall reaction rates.
Femtogram Detection of Explosive Nitroaromatics: Fluoranthene‐Based Fluorescent Chemosensors
Authors: Venkatramaiah N. , Kumar Shiv , Patil Satish 
Published: September 2012

AbstractHerein we report a novel fluoranthene‐based fluorescent fluorophore 7,10‐bis(4‐bromophenyl)‐8,9‐bis[4‐(hexyloxy)phenyl]fluoranthene (S3) and its remarkable properties in applications of explosive detection. The sensitivity towards the detection of nitroaromatics (NACs) was evaluated through fluorescence quenching in solution, vapor, and contact mode approaches. The contact mode approach using thin‐layer silica chromatograp‐ hic plates exhibited a femtogram (1.15 fg cm−2) detection limit for trinitrotoluene (TNT) and picric acid (PA), whereas the solution‐phase quenching showed PA detection at the 2–20 ppb level. Fluorescence lifetime measurements revealed that the quenching is static in nature and the quenching process is fully reversible. Binding energies between model binding sites of the S3 and analyte compounds reveal that analyte molecules enter into the cavity created by substituted phenyl rings of fluoranthene and are stabilized by strong intermolecular interactions with alkyl chains. It is anticipated that the sensor S3 could be a promising material for the construction of portable optical devices for the detection of onsite explosive nitroaromatics.
Direct Acyl Substitution of Carboxylic Acids: A Chemoselective O‐ to N‐Acyl Migration in the Traceless Staudinger Ligation
Authors: Kosal Andrew D. , Wilson Erin E. , Ashfeld Brandon L. 
Published: September 2012

AbstractA chlorophosphite‐modified, Staudinger‐like acylation of azides involving a highly chemoselective, direct nucleophilic acyl substitution of carboxylic acids is described. The reaction provides the corresponding amides with analytical purity in 32–97 % yield after a simple aqueous workup without the need for a pre‐activation step. The use of chlorophosphites as dual carboxylic acid–azide activating agents enables the formation of acyl CN bonds in the presence of a wide range of nucleophilic and electrophilic functional groups, including amines, alcohols, amides, aldehydes, and ketones. The coupling of carboxylic acids and azides for the formation of alkyl amides, sulfonyl amides, lactams, and dipeptides is described.
Experimental and DFT Evidence for the Fractional Non‐Innocence of a β‐Diketonate Ligand
Authors: Das Amit , Scherer Thomas Michael , Mondal Prasenjit , Mobin Shaikh M. , Kaim Wolfgang , Lahiri Goutam Kumar 
Published: September 2012

AbstractNew compounds [Ru(pap)2(L)](ClO4), [Ru(pap)(L)2], and [Ru(acac)2(L)] (pap=2‐phenylazopyridine, L−=9‐oxidophenalenone, acac−=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)2(L)](ClO4) and [Ru(acac)2(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the RuIII/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac− ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L− into L. could be deduced from the near‐IR absorption of [RuIII(pap)(L.)(L−)]2+. Other intense long‐wavelength transitions, including LMCT (L−→RuIII) and LL/CT (pap.−→L−) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [RuIII(pap0)2(L−)]2+↔[RuII(pap0)2(L.)]2+ and [RuIII(pap0)(L−)2]+↔[RuII(pap0)(L⋅)(L−)]+. Calculations of electrogenerated complex [RuII(pap.−)(pap0)(L−)] displayed considerable negative spin density (−0.188) at the bridging metal.
Copper‐Catalyzed Three‐Component Borylstannylation of Alkynes
Authors: Takemoto Yuki , Yoshida Hiroto , Takaki Ken 
Published: September 2012

AbstractRegio‐ and stereoselective installation of boryl and stannyl moieties into a carbon–carbon triple bond of various alkynes has been achieved based on a three‐component coupling reaction by using a diboron and a tin alkoxide with the aid of a copper(II) acetate–tricyclohexylphosphine complex, giving diverse vic‐borylstannylalkenes in a straightforward manner. Carbon–tin and carbon–boron bonds of the resulting borylstannylation product are successively transformed into carbon–carbon bonds by a Migita–Kosugi–Stille and a Suzuki–Miyaura coupling, leading to the formation of (Z)‐tamoxifen with anti‐breast cancer activity.
Chiral Benzamidinate Ligands in Rare‐Earth‐Metal Coordination Chemistry
Authors: Benndorf Paul , Kratsch Jochen , Hartenstein Larissa , Preuss Corinna M. , Roesky Peter W. 
Published: September 2012

AbstractThe treatment of the recently reported potassium salt (S)‐N,N′‐bis‐(1‐phenylethyl)benzamidinate ((S)‐KPEBA) and its racemic isomer (rac‐KPEBA) with anhydrous lanthanide trichlorides (Ln=Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)‐PEBA}3Sm], bis(amidinate) complexes [{Ln(PEBA)2(μ‐Cl)}2] (Ln=Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)2(thf)n] (Ln=Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)–amido complexes [{(S)‐PEBA}2Ln{N(SiMe3)2}] (Ln=Y, Lu) were synthesized by an amine‐elimination reaction and salt metathesis. All of these chiral bis‐ and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac‐PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)‐PEBA}2Ln{N(SiMe3)2}] (Ln=Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.
Adsorption Characteristics of β‐Ionone in Water on Granular Activated Carbon
Authors: Deng Jing , Shao Yi‐Sheng , Gao Nai‐Yun , Zhou Shi‐Qing , Hu Xu‐Hao 
Published: September 2012

AbstractThe adsorption performance of β‐ionone on four types of granular activated carbon (GAC) in water was investigated through batch experiments. The effect of initial β‐ionone concentrations and natural organic matter (NOM) adsorbed on GAC, adsorption kinetic and isothermal models were also studied. The results showed that four types of GAC all had good adsorption performance for β‐ionone, the equilibrium adsorption amount of the GAC employed was in the order of YK > GK > MZ‐A > MZ‐B. The adsorption amount increased with increasing initial concentrations. The presence of NOM could reduce adsorption of β‐ionone to a certain extent, and small molecular weight (MW) fractions (particularly <1000 Da) exhibited a remarkably competitive effect on the adsorption of β‐ionone. The experimental data showed good correlation with pseudo‐first‐order model. Furthermore, adsorption of β‐ionone on GAC fitted Freundlich, Langmuir, and Tempkin isotherms in the range of experimental concentrations, but followed Freundlich isothermal model most appropriate. The thermodynamic parameters were calculated by the results of the experiment, which showed adsorption of β‐ionone on GAC as being endothermic and spontaneous.
Synthesis, Cytotoxicity, Induction of Apoptosis, and Interaction with DNA of Dinuclear Platinum(II) Complexes
Authors: Xu Gang , Gao Chuanzhu , Gou Shaohua , Cao Zhe 
Published: September 2012

AbstractSix dicarboxylato‐bridged dinuclear platinum(II) complexes S1–S6, with a newly designed chiral ligand, 2‐{[(1R,2R)‐2‐aminocyclohexyl]amino}propanoic acid (HL), were prepared and spectrally characterized. The in vitro cytotoxicity of all resulting platinum(II) complexes was evaluated against human HCT‐116, MCF‐7, and HepG‐2 tumor cell lines. The results show that all compounds exhibit positive biological activity toward HCT‐116 and MCF‐7 cell lines, of which complexes S3, S4, and S5, with succinate and its derivatives as bridges, showing better activity than the positive controls. Moreover, double‐dyeing flow cytometric resection experiments indicate that the target compounds inhibit tumor cell growth by inducing apoptosis; gel electrophoresis experiments demonstrate the compounds′ ability to prompt pET22b plasmid DNA degradation in almost the same way as oxaliplatin.
A Photosensitive Liquid Crystal Studied by 14N NMR, 2H NMR, and DFT Calculations
Authors: Marini Alberto , Zupančič Blaž , Domenici Valentina , Mennucci Benedetta , Zalar Boštjan , Veracini Carlo Alberto 
Published: September 2012

AbstractAn azobenzene derivative, namely diheptylazobenzene, showing the nematic and smectic A liquid crystalline phases, was investigated by means of a combined approach based on NMR and DFT calculations. 14N NMR quadrupole‐ and chemical‐shift‐perturbed spectra were acquired in the whole mesophasic range, providing both experimental quadrupolar splittings and chemical shift anisotropy values. On the same mesogen, deuterium labelled at the α‐position of the hydrocarbon chain, 2H NMR quadrupole‐perturbed spectra were recorded. The analysis of these NMR data was performed with the help of ab initio calculations, in vacuo and by taking into account the effect of the anisotropic environment typical of liquid crystals, by using the IEF‐PCM model. The geometry optimizations of the azomesogen in the trans and cis configurations were performed by DFT calculations employing the combination of B3LYP functional with the 6‐311G(d) basis set. The analysis of experimental NMR data was performed by considering the trans configuration as the most populated one and the corresponding quadrupolar tensors and chemical shielding tensors were determined at the DFT level of theory. The main result of this work is the determination of a relatively high and temperature‐dependent molecular biaxiality of the trans state of this azomesogen.
Impacts of Composition and Post‐Treatment on the Brønsted Acidity of Steam‐Treated Faujasite: Insights from FTIR Spectroscopy
Authors: Cairon Olivier 
Published: September 2012

AbstractA detailed FTIR study of the effects of steaming and acid leaching on protonated Y faujasite (FAU) and EMT zeolites is provided and the results are thoroughly analysed. In particular, emphasis is placed on the Brønsted acidic evolution and acidic strength measurements for a large series of as‐modified zeolites using CO as a sensitive probe to distinguish various protonic sites. While an increase of acidity for framework OH groups is observed during the strengthening of dealumination for both FAU and EMT series, the steaming process also generates a large variety of additional Brønsted acidic groups. Regarding acidic strength, these heterogeneous OH groups are sensitive to post‐treatments and their existence strongly depends on the initial composition of the zeolites. The presence of residual Na+ cations in the starting materials induces dramatic Brønsted acidic changes after steaming. As a result, steamed zeolites that initially contain traces of sodium possess unusual acidic Brønsted groups with low acidity. This result contradicts the trend generally observed with framework OH groups, for which steaming results in an increase of Brønsted acidic strength. The study reveals that the situation is indeed more complex, as some compositions and post‐treatments strongly influence the Brønsted acidity of as‐steamed zeolites both in their nature and their corresponding acidic strength. By linking these IR‐compiled features to the as‐exposed modifications, a large acidity scale better suited to characterizing catalysts having Brønsted acidity expanding from lowest to highest strength is proposed.
Prism‐Based Surface Plasmon Coupled Emission Imaging
Authors: Cai Wei‐Peng , Liu Qian , Cao Shuo‐Hui , Weng Yu‐Hua , Liu Xiao‐Qing , Li Yao‐Qun 
Published: September 2012

AbstractA prism‐based surface plasmon coupled emission (SPCE) imaging apparatus with a reverse Kretschmann (RK) configuration was developed and applied to dye‐doped polymer films. Highly polarized, directional and enhanced fluorescence images were obtained. The angular distribution of the SPCE images was in accordance with the validated theoretical calculation performed using Fresnel equation. Prism‐based SPCE imaging combined with microarray technology appears to be a promising platform for rapid and high‐throughput analysis, especially for high‐density arrays. We believe that prism‐based SPCE imaging has potential applications in biochemical research.
A Spectroscopic and Computational Study of Propofol Dimers and Their Hydrated Clusters
Authors: León Iker , Millán Judith , Castaño Fernando , Fernández José A. 
Published: September 2012

AbstractPropofol (2,6‐diisopropylphenol, PPF) homodimers and their complexes with one water molecule are analyzed by means of mass‐resolved excitation spectroscopy. Using two‐color resonance‐enhanced multiphoton ionization (REMPI) the S1 electronic spectra of these systems are obtained, avoiding fragmentation. Due to the large size of these species, the spectra present a large abundance of lines. Using UV/UV hole‐burning spectroscopy, two isomers of PPF2 are found and the existence of at least three isomers for propofol2(H2O)1 (PPF2W1) is demonstrated. Comparison with the structures calculated at the M06‐2X/6‐311++G(d,p) and M06‐2X/6‐31+G(d) levels of theory shows that the main driving forces in PPF2 are several CH⋅⋅⋅π interactions accompanied by dipole–dipole interaction between the OH moieties. On the other hand, there is evidence for the formation of cyclic hydrogen‐bond structures in the heterotrimers. A comparison of the results obtained herein with those of similar systems from previously published studies follows.
Synthesis, Physicochemical Studies, Molecular Dynamics Simulations, and Metal‐Ion‐Dependent Antiproliferative and Antiangiogenic Properties of Cone ICL670‐Substituted Calix[4]arenes
Authors: Rouge Pascal , Dassonville‐Klimpt Alexandra , Cézard Christine , Boudesocque Stéphanie , Ourouda Roger , Amant Carole , Gaboriau François , Forfar Isabelle , Guillon Jean , Guillon Emmanuel , Vanquelef Enguerran , Cieplak Piotr , Dupradeau François‐Yves , Dupont Laurent , Sonnet Pascal 
Published: September 2012

AbstractIron chelators, through their capacity to modulate the iron concentration in cells, are promising molecules for cancer chemotherapy. Chelators with high lipophilicity easily enter into cells and deplete the iron intracellular pool. Consequently, iron‐dependent enzymes, such as ribonucleotide reductase, which is over‐expressed in cancer cells, become nonfunctional. A series of calix[4]arene derivatives substituted at the lower rim by ICL670, a strong FeIII chelator, have been synthesized. Physicochemical properties and antiproliferative, angiogenesis, and tumorigenesis effects of two calix[4]arenes mono‐ (5 a) or disubstituted (5 b) with ICL670 have been studied. These compounds form metal complexes in a ratio of one to two ligands per FeIII atom as shown by combined analyses of the protometric titration curves and ESIMS spectra. The grafting of an ICL670 group on a calix[4]arene core does not significantly alter the acid–base properties, but improves the iron‐chelating and lipophilicity properties. The best antiproliferative and antiangiogenic results were obtained with calix[4]arene ligand 5 a, which possesses the highest corresponding properties. Analyses of molecular dynamics simulations performed on the two calix[4]arenes provide three‐dimensional structures of the complexes and proved 5 a to be the most stable upon complexation.
Evaluation of the Catalytic Performance of Gas‐Evolving Electrodes using Local Electrochemical Noise Measurements
Authors: Zeradjanin Aleksandar R. , Ventosa Edgar , Bondarenko Alexander S. , Schuhmann Wolfgang 
Published: September 2012

AbstractCharacterization of gas evolution reactions at the electrode/electrolyte boundary is often difficult due to the dynamic behavior of interfacial processes. Electrochemical noise measurements determined by scanning electrochemical microscopy were used to characterize Cl2 evolution at gas‐evolving electrodes (GEEs). Analysis of the electrochemical noise is a powerful method to evaluate the efficiency of the catalyst layer at a GEE. The high sensitivity of the developed measurement system enabled accurate monitoring of the current fluctuations caused by gas‐bubble detachment from the electrode surface. Fourier transform analysis of the obtained current responses allows extraction of the characteristic frequency, which is the main parameter of the macrokinetics of GEEs. The characteristic frequency was used as part of a methodology to evaluate the catalyst performance and, in particular, to estimate the fraction of the catalyst layer that is active during the gas evolution reaction.
Selective Synthesis of 1‐O‐Alkyl(poly)glycerol Ethers by Catalytic Reductive Alkylation of Carboxylic Acids with a Recyclable Catalytic System
Authors: Sutter Marc , Dayoub Wissam , Métay Estelle , Raoul Yann , Lemaire Marc 
Published: September 2012

Abstract(Poly)glycerol monoethers were synthesized in good yield and selectivity by the catalytic reductive alkylation of glycerol, diglycerol, and triglycerol with readily available, cheap and/or bio‐sourced carboxylic acids. The reaction was catalyzed by 1 mol % of Pd/C under 50 bar H2 using an acid ion‐exchange resin as a recyclable cocatalyst. The catalytic system was recycled several times, and a mechanism is proposed for this transformation.
Influence of nitrogen addition on fundamental discharge properties in alternating current plasma display panels
Authors: Oda Akinori , Hirano Yoshikuni 
Published: September 2012

AbstractIn order to clarify the influence of the addition of nitrogen on the fundamental properties of plasma display panel (PDP) discharges in a Ne/Xe (10%) gas mixture, the PDP discharges in Ne/Xe/N2 gas mixtures have been simulated using a one‐dimensional fluid model that is based on the continuity equations for electrons, ions, excited atoms and molecules, with the Poisson equation and the electron energy balance equation. Based on the simulation results, we found that a pulsed discharge with a short time ( 100 ns) occurs once during every half cycle. At a nitrogen concentration of more than 100 ppm, a phase delay of the gap voltage and discharge current in Ne/Xe gas mixture PDP discharges began to appear. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(10): 37–43, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10399
Manganese Detection with a Metal Catalyst Free Carbon Nanotube Electrode: Anodic versus Cathodic Stripping Voltammetry
Authors: Yue Wei , Bange Adam , Riehl Bill L. , Riehl Bonnie D. , Johnson Jay M. , Papautsky Ian , Heineman William R. 
Published: September 2012

AbstractAnodic stripping voltammetry (ASV) and cathodic stripping voltammetry (CSV) were used to determine Mn concentration using metal catalyst free carbon nanotube (MCFCNT) electrodes and square wave stripping voltammetry (SWSV). The MCFCNTs are synthesized using a Carbo Thermal Carbide Conversion method which results in a material that does not contain residual transition metals. Detection limits of 120 nM and 93 nM were achieved for ASV and CSV, respectively, with a deposition time of 60 s. CSV was found to be better than ASV in Mn detection in many aspects, such as limit of detection and sensitivity. The CSV method was used in pond water matrix addition measurements.