bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guanosine Hydrogen‐Bonded Scaffolds: A New Way to Control the Bottom‐Up Realisation of Well‐Defined Nanoarchitectures
Authors: Lena Stefano , Masiero Stefano , Pieraccini Silvia , Spada Gian Piero 
Published: May 2009

AbstractOver the last two decades, guanosine‐related molecules have been of interest in different areas, ranging from structural biology to medicinal chemistry, supramolecular chemistry and nanotechnology. The guanine base is a multiple hydrogen‐bonding unit, capable also of binding to cations, and fits very well with contemporary studies in supramolecular chemistry, self‐assembly and non‐covalent synthesis. This Concepts article, after reviewing on the diversification of self‐organised assemblies from guanosine‐based low‐molecular‐weight molecules, will mainly focus on the use of guanine moiety as a potential scaffold for designing functional materials of tailored physical properties.
High‐Performance p‐Channel Organic Semiconducting Candidates Based on Benzo[1,2‐k;4,5‐k′]difluoranthene Derivatives
Authors: Liu Wei‐Szu , Liu Chia‐Chun , Kuo Ming‐Yu 
Published: May 2009

AbstractOrbital promises: Frontier orbital analyses showed that the small λ+ value of 8,17‐di‐n‐hexylbenzo[1,2‐k;4,5‐k′]difluoranthene (DH‐BDF) is owed to the nonbonding character of the BDF framework. The calculated adiabatic ionic potential and hole mobility indicates that this compound is a p‐type air‐stable organic field‐effect transistor, which promises to be a soluble, stable and high‐performance p‐type organic semiconductor.magnified image
Osmabenzenes from Osmacycles Containing an η2‐Coordinated Olefin
Authors: Gong Lei , Chen Zhening , Lin Yumei , He Xumin , Wen Ting Bin , Xu Xin , Xia Haiping 
Published: May 2009

AbstractOsmabenzenes can be easily synthesized from two η2‐coordinated olefin osmacycles in the presence of benzonitrile by means of facile hydrogen‐transfer conversions (see graphic). Mechanisms for the formation of osmabenzenes are proposed based on DFT calculations.magnified imageTreatment of HCCC(CH3)(OH)CHCH2 with [OsCl2(PPh3)3] in dichloromethane yielded the η2‐olefin‐coordinated osmacycle [Os{CHC(PPh3)C(CH2)‐η2‐CHCH2}Cl2(PPh3)2] (9). Transformations of osmacycle 9 by treatment with benzonitrile under various conditions have been investigated. Reaction of 9 with excess benzonitrile at room temperature afforded the dicationic osmacycle [Os{CHC(PPh3)C(CH2)‐η2‐CHCH2}(PhCN)2(PPh3)2]Cl2 (11) by ligand substitution, which reacted further to the intramolecularly coordinated η2‐allene complex [Os{CHC(PPh3)C(CH3)(η2‐CCH2)}(PhCN)2(PPh3)2]Cl2 (12). In contrast, heating a chloroform solution of 9 to the reflux temperature in the presence of excess benzonitrile generated osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}(PhCN)2(PPh3)2]Cl2 (14). Complexes 11, 12 and 14 are in fact isomers. In the absence of excess benzonitrile, the isolated dicationic 12 and 14 readily dissociate the benzonitrile ligands in solution to produce the neutral complex [Os{CHC(PPh3)C(CH3)(η2‐CCH2)}Cl2(PPh3)2] (13) and the monocationic osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}Cl(PhCN)(PPh3)2]BPh4 (15), respectively. Mechanisms for the formation of osmabenzene 14 from 11 and 12 are proposed based on DFT calculations.
Complexation of Aliphatic Ammonium Ions with a Water‐Soluble Cucurbit[6]uril Derivative in Pure Water: Isothermal Calorimetric, NMR, and X‐ray Crystallographic Study
Authors: Kim Youngkook , Kim Hyunuk , Ko Young Ho , Selvapalam Narayanan , Rekharsky Mikhail V. , Inoue Yoshihisa , Kim Kimoon 
Published: May 2009

AbstractWithout interference: The complexation of aliphatic ammonium ions with a water‐soluble cucurbit[6]uril (CB[6]) derivative, CB*[6] (see picture), in pure water is investigated by isothermal titration calorimetry, NMR spectroscopy, and X‐ray crystallography. The binding affinity of the host in pure water is 2–5 orders of magnitude higher than that in the presence of interfering ions, such as protons and alkali metal ions.magnified imageComplexation of a water‐soluble cucurbituril (CB) derivative, cyclohexanocucurbit[6]uril (CB*[6]), the cavity dimensions of which are essentially the same as those of CB[6], with various organic mono‐ and diammonium ions has been studied by isothermal titration calorimetry and 1H NMR spectroscopy. The binding affinity of CB*[6] with the guest molecules in water is 3–5 and 2–3 orders of magnitude higher than those of CB[6] in 50 % formic acid and in 0.05 m NaCl solution, respectively, which is mainly due to the larger enthalpic gains upon complex formation in the absence of interfering ions, such as protons and Na+. In particular, the binding constant (K) of spermine to CB*[6] was measured to be 3.4×1012 m−1, which is the highest binding constant ever reported for CB[6] or its derivatives. We also obtained the X‐ray crystal structures of α,ω‐alkanediammonium ions (CnDA2+, n=4–8) and spermine complexes with CB[6], in which the aliphatic chains of the guest molecules take an extended or partially bent conformation inside the CB[6] cavity, depending on the chain length. The hexamethylene chain of C6DA2+ takes a twisted conformation, which not only allows strong ion–dipole interactions between the ammonium groups and the carbonyl groups at the portals, but also increases hydrophobic interactions between the alkyl part of the guest and the inner wall of the host, which results in the largest enthalpic gain among α,ω‐alkanediammonium ions. The thermodynamic parameters associated with the complexation are discussed in relation to the binding modes and conformations of the aliphatic chain of the guest molecules inside the host, which were investigated by 1H NMR spectroscopy and X‐ray crystallography.
Highly Enantioselective One‐Pot, Three‐Component Mannich‐type Reaction Catalyzed by an N,N′‐Dioxide–Scandium(III) Complex
Authors: Chen Shikui , Hou Zongrui , Zhu Yin , Wang Jing , Lin Lili , Liu Xiaohua , Feng Xiaoming 
Published: May 2009

AbstractMild‐mannered Mannich reaction: Highly enantioselective one‐pot, three‐component Mannich‐type reaction of aldehydes, 2‐aminophenol, and ketene silyl acetal with 5 mol % of a C2‐symmetric N,N′‐dioxide‐based scandium(III) triflate (2:1) complex as the catalyst was achieved under mild conditions (see scheme), which facilitated the asymmetric synthesis of biologically interesting β‐amino esters.magnified image
How are Heteroelements (Ga and Ge) Incorporated in Silicate Oligomers?
Authors: Schaack Bernd Bastian , Schrader Wolfgang , Schüth Ferdi 
Published: May 2009

AbstractUncovering the mystery: Typical zeolite prenucleating solutions containing Ga and Ge were studied by ESI‐MS. Ga and Ge incorporate into the oligomers in different ways, and their structure‐directing effect appears stronger than that of the template. MS/MS experiments were used to obtain detailed structural information about the occurring species (see figure).magnified imageThe properties of microporous solids can be strongly influenced during the first stages of solid‐state formation from solution. Furthermore, their properties are directly related to the presence, number, and character of intra‐ or extraframework heteroelements. In this contribution we studied the influence of the substitution of silicon against heteroelements, such as gallium and germanium. The aqueous prenucleating solutions were obtained by hydrolysis of the silicon and heteroelement sources in the presence of tetraalkylammonium cations. The time‐resolved stepwise formation of larger oligomers was studied by using electrospray ionization mass spectrometry (ESI‐MS). Furthermore, the structures of the obtained signals were verified by using MS/MS experiments, which led to the conclusion that strong structure‐directing effects emerge from the introduction of heteroelements into the solutions.
Untersuchung der Ultrafeinmahlung von Bariumsulfat
Authors: Petrova A. , Tomas J. 
Published: May 2009

AbstractDie Ultrafeinmahlung von Bariumsulfat wurde in einer Ringspaltmühle untersucht und dazu diskontinuierliche Versuche durchgeführt. Es zeigt sich, dass die eingetragene Energie, der Mahlkörperfüllungsgrad sowie die Mahlgutkonzentration einen signifikanten Einfluss auf das Zerkleinerungsergebnis haben. Die Agglomeration der Partikel wurde mit einem handelsüblichen Dispergiermittel verhindert, das einen signifikanten Einfluss auf den spezifischen Leistungseintrag und die Energieausnutzung in der Mühle nimmt.
Pd/C/PPh3: A Simple and Efficient Catalyst System for Double Carbonylation Reactions
Authors: LIU Jianming , ZHENG Shuzhan , SUN Wei , XIA Chungu 
Published: May 2009

AbstractThe double carbonylation of iodobenzene and diethylamine proceeds smoothly in the presence of Pd/C and carbon monoxide to afford the corresponding α‐keto amide in good yields with excellent selectivity. In addition, other aryl iodides and secondary amines also react under similar conditions to form α‐keto amides in good yields.
Reactivity of Carboxyl‐functionalized Cubane‐like Photocyclodimer of 2‐Substituted Naphthalene toward Aromatic Amines
Authors: LIAO Guihong , LUO Lin , WU Xiaoling , LEI Lei , TUNG Chenho , WU Lizhu 
Published: May 2009

AbstractReactions of carboxyl‐functionalized cubane‐like photocyclodimer 2 with a series of aromatic amines 3 were investigated for understanding the reactivity of this unique system. Spectroscopic and X‐ray crystal structural analyses demonstrate that N,N′‐dicyclohexylcarbodiimide (DCC) is reactive toward 2 affording stable 4 with a well‐retained cubane‐like structure. With the assistance of DCC, mono‐ and diacyl‐substituted photocyclodimers of 2‐sustituted naphthalene (5 and 6) have also been achieved in reasonable yields in addition to the formation of 4. Subtle change in the electronic properties of the series of aromatic amines 3 modulates the reactivity and product distribution remarkably.
Dynamical Complexity in Electrochemical Oxidations of Thiocyanate
Authors: LIU Li , FENG Jiamin , WU Guoguang , LÜ Xiaoli , Gao Qingyu 
Published: May 2009

AbstractKinetics and mechanism of the electrochemical oxidation of thiocyanate on a Pt electrode were investigated by using various electrochemical methods, in which both current and potential oscillations have been observed. Cyclic voltammetry measurements illustrate that the oxidation process consists of two steps. In addition to the oscillatory behavior, the system also exhibits bistability, in which the oxidation could be switched between a high and a low current density states with a temporal potential perturbation. The presence of inert ions with stronger absorption also induces transitions from oscillatory to steady reactions in the thiocyanate system.
Sm1.5Sr0.5MO4 (M=Ni, Co, Fe) Cathode Catalysts for Ammonia Synthesis at Atmospheric Pressure and Low Temperature
Authors: XU Gaochao , LIU Ruiquan 
Published: May 2009

AbstractSm1.5Sr0.5MO4 (M=Ni, Co, Fe) (SSM) catalysts were prepared by a sol‐gel method and characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was synthesized from wet hydrogen and dry nitrogen at atmospheric pressure and low temperature (25–100 °C) with applied voltage, using SSM as a cathode, Ni‐Ce0.8Sm0.2O2−δ (Ni‐SDC) as an anode, and silver‐platinum film as a current collector, Nafion proton exchange membrane as a proton permeating membrane. Several important factors on ammonia synthesis were investigated and the optimal synthetic temperature was found, at which the highest rate of evolution of ammonia was up to 1.05×10−8 mol·cm−2·s−1.
Spectroscopic Studies on the Binding of Bacteriophage Mequindox with Bovine Serum Albumin
Authors: ZENG Zhouhua , LIU Yi , HU Xianming , XU Zhenqiang , ZENG Kun 
Published: May 2009

AbstractFluorescence spectra and UV‐Vis absorption spectra have been used to study the binding of bacteriophage mequindox (MEQ) with bovine serum albumin (BSA), which performed a dynamic quenching process. The quenching constants and thermodynamic parameters at different temperatures were calculated. The binding was primarily driven by entropy, and hydrophobic forces also played a significant role. The distance between BSA and MEQ was estimated to be 4.5 nm based on the theory of F?rster's non‐radioactive energy transfer. Furthermore, synchronous fluorescence spectra and 3‐dimensional fluorescence spectra were used to figure out the configuration of BSA in the presence or absence of MEQ, which indicated that it was basically the same.
π Type Lithium Bond Interaction between Ethylene, Acetylene, or Benzene and Amido‐lithium
Authors: YUAN Kun , LIU Yanzhi , LÜ Lingling , ZHU Yuancheng , ZHANG Ji , ZHANG Junyan 
Published: May 2009

Abstract The optimization geometries and interaction energy corrected by basis set super‐position error (BSSE) of the lithium bond complexes between ethylene, acetylene, or benzene and amido‐lithium have been calculated at the B3LYP/6‐311++G∗︁∗︁ and MP2/6‐311++G∗︁∗︁ levels. And only one configuration was obtained for each lithium bond system. All the equilibrium geometries were confirmed to be stable state by analytical frequency computations. The calculations showed that all the N(2)–Li(4) bond lengths increased obviously and the red shift of N(2)–Li(4) stretching frequency occurred after complexes formed. The calculated binding energies with BSSE and zero‐point vibrational energy corrections of complexes I, II and III are −26.04, −24.86 and −30.02 kJ·mol−1 via an MP2 method, respectively. Natural bond orbital (NBO) theory analysis revealed that the three complexes were all formed with π type lithium bond interaction between ethylene, acetylene, or benzene and amido‐lithium.
Adsorption of Methane on Water under Hydrate Formation Conditions
Authors: PENG Baozi , SUN Changyu , LIU Peng , CHEN Guangjin 
Published: May 2009

AbstractThe variation of interfacial tension with pressure has been determined systemically for water in equilibrium with compressed methane at temperature from 274.2 to 282.2 K in the range of pressure from 0.1 to 10.1 MPa using the pendant‐drop method. The results show that the interface tension decreased with increasing pressure when temperature was specified. Pressure has a great influence upon the interface tension at higher pressure. The surface excess concentrations of methane on water at different temperatures and pressures were calculated. The results showed that higher pressure and lower temperature corresponded to higher adsorption concentration of methane. At the same time, the surface adsorption free energies of methane were also calculated, indicating that the adsorption of methane on water under hydrate formation condition is more preferable than that at 298.2 K.
Activity Coefficients for NaBr in Aqueous D‐Trehalose/D‐Cellobiose Solutions at 298.15 K
Authors: ZHUO Kelei , WANG Wenhao , CHEN Yujuan , WANG Jianji 
Published: May 2009

AbstractThe ionic mean activity coefficients of NaBr in trehalose‐water and cellobiose‐water mixtures have been experimentally determined at 298.15 K from electrochemical potential measurements by an electrochemical cell containing two ion selective electrodes (ISE), together with the activity coefficients of the disaccharides. The parameters C1 representing the pair interactions between the disaccharides and NaBr have been obtained. The interactions of NaBr with trehalose, cellobiose and glucose were compared and discussed in terms of their difference in the stereo‐structures.
Preparation and Storage of Silver Nanoparticles in Aqueons Polymers
Authors: SONG Weihong , ZHANG Xiaoxiao , YIN Hongzong , SA Panpan , LIU Xiaoyan 
Published: May 2009

AbstractSilver nanoparticles were obtained by a chemical reduction method using aqueous polymers as dispersant and characterized by UV‐Vis spectroscopy, transmission electron microscopy (TEM) and light‐scattering spectroscopy. Solid polymer films containing the silver nanoparticles were also prepared after evaporating the solvent, and then dried with existing polymer. The stability of the silver nanoparticles was compared between primary fresh silver nanoparticle solution and redissolved solid polymer films by UV‐Vis spectroscopy. The particle size ranged from 5 to 10 nm, and no obvious differences were found. Therefore, preparing solid nano‐Ag/polymer was a novel and useful method in storage of silver nanoparticles.
Monitoring of Methyldopa by Fast Fourier Transform Continuous Cyclic Voltammetry at Gold Microelectrode
Authors: NOROUZI Parviz , GANJALI Mohammad Reza , SHAHTAHERI Sayed Jamaleddin , DINARVAND Rasoul , HAMZEHPOOR Ali 
Published: May 2009

AbstractA continuous cyclic voltammetric study of methyldopa at gold micro electrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorpted at 400 mV, giving rise to change in the current of well‐defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest one of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal‐to‐noise ratio has significantly increased by application of discrete Fast Fourier transform (FFT) method, background subtraction and two‐dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10−7−1.0×10−11 mol·L−1 (r=0.9975) with a limit of detection and quantitation 0.004 nmol·L−1 and 0.03 nmol·L−1, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay methyldopa in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the methyldopa were considered.
Controlled Synthesis and Characterization of Monodisperse Fe3O4 Nanoparticles
Authors: SHI Rongrong , GAO Guanhua , YI Ran , ZHOU Kechao , QIU Guanzhou , LIU Xiaohe 
Published: May 2009

AbstractMonodisperse Fe3O4 nanoparticles were successfully synthesized through the thermal decomposition of iron acetylacetonate in octadecene solvent in the presence of oleic acid and oleylamine. The influences of experimental parameters, such as reacting temperature, amounts and kinds of surfactants, solvents, oleic acid and oleylamine, on the size and shape of monodisperse Fe3O4 nanoparticles were discussed. The phase structures, morphology, and size of the as‐prepared products were investigated in detail by X‐ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high‐resolution transmission electron microscopy (HRTEM). Magnetic property was measured using a vibrating sample magnetometer (VSM) at room temperature, which revealed that Fe3O4 nanoparticles were of ferromagnetism with a saturation magnetization (Ms) of 74.0 emu/g and coercivity (Hc) of 72.6 Oe.
Determination of Epinephrine by Flow Injection Analysis Coupled Ag(III) Complex‐Luminol Chemiluminescence Detection
Authors: BAI Jiangbo , SHI Hongmei , ZHANG Yingze , TIAN Dehu , XU Xiangdong , KANG Weijun 
Published: May 2009

AbstractA new Ag(III) complex‐luminol chemiluminescent system which was applied to the determination of epinephrine is firstly reported. Based on the enhancing effect of epinephrine on the chemiluminescence reaction of luminol with [Ag(HIO6)2]5− in alkaline solution, a highly sensitive chemiluminescence (CL) detection by flow injection analysis (FIA) was developed for epinephrine. Under the optimum conditions, CL intensity was proportional to concentration of epinephrine in the 1.0×10−9–1.0×10−7 mol·L−1 range. The limit of detection was 8.0×10−10 mol·L−1 for epinephrine (3δ), with a relative standard deviation (n=11) of 2.9% for 1.5×10−8 mol·L−1 epinephrine. The method validation was done with epinephrine determinations in commercial pharmaceutical products. The mechanism of the reactions was also discussed.
Separation of Aminobenzoic Acids by Gold Nanoparticle‐ modified Capillary Electrophoresis
Authors: YAN Hongtao , LI Tuo , GUO Yanli 
Published: May 2009

AbstractA novel method for the separation of aminobenzoic acids by capillary electrophoresis was developed. The capillary was modified with gold nanoparticles. The effect of gold nanoparticles on the resolution and selectivity of separation was investigated. The influence of separation voltage, pH and buffer concentration on the separation of aminobenzoic acids was also examined. It was found that the presence of gold nanoparticles improved the precision of the analysis and increased the separation efficiency. Under the optimized experiment conditions, aminobenzoic acids were separated and determined. Linearity was established over the concentration range 0.5–40 µg·mL−1 with correlation coefficients of 0.9978–0.9992. The detection limits (S/N=3) were from 0.1 to 0.5 µg·mL−1.
Separation of Immunoglobulin in Conjunction with High Performance Liquid Chromatography Using Poly(vinyl ester resin) Monolith
Authors: YANG Guanqun , YANG Gengliang , LIU Haiyan , BAI Ligai , FENG Xiaojuan , YANG Xinru 
Published: May 2009

AbstractUsing vinyl ester resin both as the monomer and the crosslinker, 2,2‐azobis(2‐methylpropionitrile) (AIBN) as initiator, poly(vinyl ester resin) monolithic column was prepared to separate the immunoglobulin G (IgG) and yolk of eggs (IgY) from human plasma and egg yolk by HPLC respectively. The influence of concentration and pH of mobile phase on the chromatographic performance was investigated. Scanning electron microcopy showed that the poly(vinyl ester resin) monolithic stationary phase had a through‐pore structure. Dynamic capacity of IgG on the polymeric monolithic column was investigated. The monolithic column had good flow‐through properties and high resolution. The maximum adsorptive amount of IgG was 144 µg·g−1.
Facile Synthesis of 1,2,3,4‐Tetrahydrobenzo[b][1,8]‐naphthyridin‐2‐one via Baylis‐Hillman Adducts
Authors: CHEN Dongdong , XU Jing , YANG Chunhao , XIE Yuyuan 
Published: May 2009

AbstractVarious benzo[b][1,8]naphthyridin‐2‐ones were synthesized by a one‐pot tandem reduction‐double cyclization from the corresponding (Z)‐ethyl 4‐cyano‐5‐(2‐nitrophenyl)‐pent‐4‐enoates, which were easily prepared via Johnson‐Claisen rearrangement from Baylis‐Hillman affixtures of 2‐nitrobenzaldehydes. The procedure has the advantages of easy handling and seperation under mild and green conditions, and the overall yields are moderate.
Synthesis and Bioactivity of Some New 2‐(Alkoxy carbonyl alkyl)‐6‐bromo‐3,4‐dihydro‐3‐(α‐methyl benzyl)‐2‐oxo‐benzo[e] [2H‐1,3,2‐oxazaphosphinine] Derivatives
Authors: SRINIVASULU K. , SURESH KUMAR K. , HARI BABU B. , STEPHEN BABU M. F. , NAGA RAJU C. , SURESH REDDY C. 
Published: May 2009

AbstractSynthesis of some new 2‐(alkoxy carbonyl alkyl)‐6‐bromo‐3,4‐dihydro‐3‐(α‐methyl benzyl)‐2‐oxo‐3‐benzo‐ [e][2H‐1,3,2‐oxazaphosphinine] derivatives was accomplished through a two step process, which involves the condensation of 2‐[(α‐methylbenzyl amino)methyl]‐4‐bromophenol (1) with phosphorus oxychloride in equimolar quantities in the presence of triethylamine in dry toluene in 50–55 °C producing the corresponding intermediate (2), and subsequent reaction with the amino acid alkyl ester in dry tetrahydrofuran in the presence of triethylamine at different temperatures. They exhibited significant antibacterial and fungal activity.
Preparation and Application of Perchloric Acid Supported on Alumina (Al2O3‐HClO4) to the Synthesis of α‐(α‐Amidobenzyl)‐β‐naphthols
Authors: SHATERIAN Hamid Reza , KHORAMI Fahimeh , AMIRZADEH Azita , GHASHANG Majid 
Published: May 2009

AbstractPreparation of perchloric acid supported on alumina and its primary application as a solid supported heterogeneous catalyst to the synthesis of α‐(α‐amidobenzyl)‐β‐naphthols by a one‐pot, three‐component condensation of benzaldehydes, β‐naphthol and acetamide or benzamide under thermal solvent‐free conditions were described. The present methodology offers several advantages such as simple procedure, shorter reaction time, and excellent yields.