bluuebunny/crossref_metadata_2025_split huggingface dataset:
Separation of the Phenoxy Acid Herbicides and Their Enantiomers by Capillary Zone Electrophoresis in Presence of Highly Sulphated Cyclodextrins
Authors: Malik Ashok Kumar , Aulakh Jatinder Singh , Fekete Agnes , Schmitt‐Kopplin Philippe 
Published: May 2015

AbstractThe study of the chiral compounds and their fate in the environment is receiving an increasing attention — enantiomeric ratios are being measured and enantioselective degradation processes are being reported. It is particularly important with the toxic compounds like the pesticides, which are being freely used in the environment to control the harmful pests. Capillary zone electrophoresis was used for the chiral and mutual separation of four phenoxy acid herbicides using highly sulphated cyclodextrins (HSCD) in the buffer. The CE runs were performed with reverse polarity (anode in the outlet vial) using the acidic ammonium formate buffer (20 mmol, pH 3). Under these conditions of suppressed the electroendoosmotic flow (EOF), the analytes are mobilized to the anode by entering into host guest relation with the migrating negatively charged sulphated cyclodextrin. The phenoxy acid herbicides selected for the purpose were fenoprop, dicloprop, mecoprop and 2,4‐DB. The α‐HSCD and β‐HSCD have been tested as resolving agents in the CE for the separation of the enantiomers of the herbicides. Though the chiral separation of the dicloprop and mecoprop were achieved with α‐HSCD but it was not able to resolve fenoprop. With β‐HSCD the required base line separation was achieved. Potential difference selected was 10 kV. The limit of detection (S/N= 3) achieved in present case is 0.15 ppm for fenoprop, 0.14 ppm for dicloprop and mecoprop and 0.11 ppm for 2,4‐DB.
Investigation of the Reaction of Gold(III) with 2‐[2‐(4‐Dimethylamino‐Phenyl)‐Vinyl]‐1,3,3‐Trimethyl‐3H‐Indolium. Application for Determination of Gold
Authors: Serbin Rastislav , Bazel Yaroslav R. , Torok Marcel , Havel Josef , Balogh Ioseph S. , Kormosh Zholt O. , Holéczyová Gabriela , Andruch Vasil 
Published: May 2015

AbstractA new, simple, rapid, sensitive, efficient and low‐cost spectrophotometric procedure for the determination of gold was developed. The method is based on the reaction of [AuCl4]− with 2‐[2‐(4‐dimethylaminophenyl)‐vinyl]‐1,3,3‐trimethyl‐3H‐indolium reagent to form a colored ion associate extractable by various organic solvents. The molar absorptivity of the ion associates is in the range (5.7–9.2) × 104 L mol−1 cm−1 depending on the extractant. Butyl acetate was chosen as the extractant. The optimum reaction conditions were established: pH 2–4, concentration of the dye reagent (0.8–1.5) × 10−4 mol L−1. The determination of gold is not hindered even by a 1000‐fold concentration of Ni and Co; a 500‐fold concentration of Pb and Zn; a 100‐fold concentration of Bi, Cu, Cd, Pt, Rh and Ru; or a 20‐fold concentration of Ag. The established method was applied to the determination of gold in model samples and enriched polymetallic ores.
Synthesis and Characterization of Novel Arylaldehyde (Arylketone)‐(4‐Substituted phenyl‐5‐Substituted phenoxy‐Methyl‐4H‐1,2,4‐Triazole‐3‐yl)‐Thiol Acetyl Hydrazones
Authors: Zhang Heng‐Wen , Li Yan‐Ping , Liu Chen‐Jiang , Li Hai‐Long , Sun Wen‐Li 
Published: May 2015

AbstractFourteen novel arylaldehyde (arylketone)‐(4‐substituted phenyl‐5‐substituted phenoxy‐methyl‐4H‐1,2,4‐triazole‐3‐yl)‐thiol acetyl hydrazone derivatives (5a‐5g, 6a‐6g) were synthesized by 4‐substituted phenyl‐5‐substituted phenoxy‐methyl‐1,2,4‐triazole‐3‐thione as starting material according to substructure link principle, followed by thioetherification, hydrazide hydrazone reaction. The structures of these compounds were confirmed by IR, 1H NMR and elemental analysis. Crystal structure of compounds 1b and 6d were determined by the X‐ray diffraction.
Geometric Effects on Conductance in Single Molecule Electron Transport Junctions
Authors: Hsieh Shang‐Chieh , Mai Fur‐Der , Jang Soonmin , Tang Hong‐Yi , Li Feng‐Yin 
Published: May 2015

AbstractWe studied electron transport properties of a dithiol‐benzene molecule covalently bonded between two gold electrodes by combining ab initio calculations for the central molecule and a green function method to calculate electron transport. Due to the large computational demand, this type of calculations usually involves certain ways of simplification. The simplification commonly used is to fix the contact surface of the electrodes by ignoring the disturbance of the Au contact surface by contacting with the central molecule, i.e. without scattering region relaxation. In this study, we intended to resolve the difference between models with and without the above simplification. The large conductance found in our models without scattering region relaxation is due to the highly symmetric arrangement of the Au contact surface and those layers near the contact. The disturbance of the Au contact surface by the contact of the central molecule is important since the increase of the Au‐S bond and the distortion of the Au atom on the FCC site can lower the transmission coefficient between the two electrodes. In order to obtain better results, the model should include scattering region relaxation. However, when such relaxation is not applicable or demands too much calculation resource, the center molecule of the electronic transport junction should be at least optimized by the calculation level including electronic correlation, i.e. post‐HF methods.
The π‐Bonding Trend in VIB M(CO)6 Observed by NMR Spectroscopy — A Natural Bond Orbital View
Authors: Wang Shao‐Pin , Yan Ker‐Ming , Hsu Wen‐Yi , Huang Min‐Ying , Wu Hui‐Ying 
Published: May 2015

AbstractAnalysis of carbonyl's 2π orbital populations, [2π], obtained by NMR relaxation time experiments of VIB M(CO)(ẽ6‐C6H6) reveals the 3d < 4d < 5d trend for M r̊ CO back‐donation, as reported values of [2π] for VIB M(CO)5(quinuclidine). The same analysis performed on Mn(CO)3(ẽ5C5H5) and Re(CO)3(ẽ5‐C5H5) also gives 3d < 5d order of back‐donation. The distinctive 3d ∼ 5d > 4d trend reported for VIB M(CO)6 has been investigated by second‐order perturbation theory analysis within the natural bond orbital (NBO) scheme to search for orbital‐based explanations. Besides the conventional dπ r̊ 2π donor‐acceptor (DA) interaction in the trend 3d < 4d < 5d, the other DA interaction arising from three‐center‐hyperbond (3CHB) hyperconjugation has been found in the trend 3d >> 5d ∼ 4d. Within the VIB M(CO)6 family, this 3CHB hyperconjugation is so much higher in Cr(CO)6 than in W(CO)6 as to render the overall 2π populations exhibiting the 3d ∼ 5d > 4d trend.
Improved Catalytic Performance of Pt Supported on Multi‐Wall Carbon Nanotubes as Cathode for Direct Methanol Fuel Cell Applications Prepared by Dual‐Stepped Surface Thiolation Processes
Authors: Chen Tsan‐Yao , Lin Tsang‐Lang , Chen Chien‐Chung , Chen Chieng‐Ming , Chia‐Fu Chen 
Published: May 2015

AbstractThis study develops a simple surface modification process for modifying the MWCNT surface by thiolation reaction after the conventional nitric acid treatment for strong interface attachment of Pt NPs and improved dispersion onto MWCNTs. The thiolated MWCNTs (Pt/MWCNTs) showed significant improvement of methanol electro‐oxidation activity compared with that treated only by nitric acid solution. The prepared electrode with thiolated MWCNTs was used as the cathode for assembling MEA for DMFC single‐cell applications. Testing results indicate that the thiolated MWCNT cathode can improve the power density of MEA by more than 300% (from 4.6 to 20.6 mW cm−2) compared with that treated only by conventional nitric acid reactions. The dual‐step modification process for MWCNT surface treatment showed significant improvement over the convention nitric acid treatment and can be successfully used in DMFC applications.
Preparation of Silica Supported Tin Chloride: As a Recyclable Catalyst for the Silylation of Hydroxyl Groups with HMDS
Authors: Niknam Khodabakhsh , Zolfigol Mohammad Ali , Saberi Dariush , Molaee Hajar 
Published: May 2015

AbstractSilica‐supported tin chloride [SiO2‐Sn(Cl)4‐n] has been prepared by mixing tin chloride with activated silica gel in toluene under refluxing conditions for one day. A range of primary, secondary, and tertiary alcohols as well as phenolic hydroxyl groups were converted into their corresponding trimethylsilyl ethers with hexamethyldisilazane in the presence of catalytic amounts of silica‐supported tin chloride at room temperature. An excellent chemoselective silylation of hydroxyl groups in the presence of other functional groups was also observed. This catalyst could be recycled and reused fifteen times without loss of efficiency.
Efficient Synthesis of Optically Pure (+)‐Bezene Diol Epoxide and (+)‐Conduramine A‐1
Authors: Chang Yuan‐Kang , Lo Hong‐Jay , Yan Tu‐Hsin 
Published: May 2015

AbstractIn this paper, we develop a concise approach to (+)‐benzene diol epoxide and (+)‐conduramine A‐1 based upon the utilization of the C2‐symmetric L‐tartaric acid as a chiral building block.
Molecular Structure and a Density Functional Theoretical Study on 2‐Nitroimino‐5‐Nitro‐Hexahydro‐1,3,5‐Triazine (NNHT)
Authors: Zhan Jiao‐Qiang , Ma Hai‐Xia , Xu Kang‐Zhen , Chen Yong‐Shi , Hu Rong‐Zu 
Published: May 2015

Abstract2‐Nitroimino‐5‐nitro‐hexahydro‐1,3,5‐triazine (NNHT), was synthesized and its structure was determined by single‐crystal X‐ray diffraction. The crystal is monoclinic, space group P21/c with crystal parameters of a = 9.4031(13) Å, b = 8.5891(12) Å, c = 9.0200(13) Å, β = 91.213(2)°, V = 728.33(18) Å3, Z = 4, F(000) = 392, Dc = 1.734 g/cm3. The experimental geometry of NNHT was input to Gaussian‐03W program and optimized using DFT‐B3LYP/6‐311++G** method. The IR frequencies and NMR chemical shift were carried out and compared well with those of the experimental. The atomic net charges and the population analysis are discussed. The heat of formation (HOF) for NNHT was evaluated by designing an isodesmic reaction. The detonation velocity (D) and detonation pressure (P) were estimated by using the well known Kamlet‐Jacobs equation, based on the theoretical HOF.
Ultrasound‐Assisted One‐Pot Synthesis of Octahydroquinazolinone Derivatives Catalyzed by Acidic Ionic Liquid [Tbmim]Cl2/AlCl3
Authors: Niralwad Kirti S. , Shingate Bapurao B. , Shingare Murlidhar S. 
Published: May 2015

AbstractAcidic ionic liquid [tbmim]Cl2/AlCl3 catalysed an efficient synthesis of octahydroquinazolinone derivatives under ultrasound‐irradiation. This method provides several advantages such as environment benign, high yields and simple work‐up procedure.
A New Spectrophotometric Method for the Determination of Ascorbic Acid Using Leuco Malachite Green
Authors: Tiwari Kishore K. 
Published: May 2015

AbstractA new simple and sensitive and selective spectrophotometric method has been developed for the determination of ascorbic acid (AA) at trace level using a new reagent, leuco malachite green (LMG). AAreacts with potassium iodide‐iodate solution under acidic conditions to liberate iodine and the liberated iodine selectively oxidizes LMG to MG dye. The colour of the dye was measured at 620 nm. Beer's law is obeyed over the concentration range of 0.8–8 iμg μAA per 25 mL of final solution (0.032–0.32 ppm). The apparent molar absorptivity and Sandell's sensitivity of the method were found to be 2.98 × 105 l mol−1 cm−1, 0.0042 μg cm−2, and respectively. Statistical treatment of the experimental results indicates that the method is precise and accurate. The method is free from interference of common ions and many of the ingredients commonly found in pharmaceuticals. The reliability of the method was established by parallel determination against Leucocrystal violet (LCV) method. The method described was satisfactorily applied for the determination of AA in fruit juices, pharmaceuticals and biological samples.
Efficient Methyl Esterification Using Methoxyl Silica Gel as a Novel Dehydrating Reagent
Authors: Li Jian‐Guo , Peng Yan‐Qing 
Published: May 2015

AbstractMethoxyl silica gel was prepared readily by the treatment of silica chloride with methanol. By using methoxyl silica gel as a dehydrating agent, carboxylic acids reacted with methanol in the presence of a protonic acid such as 12‐phosphotungstic acid afforded the corresponding methyl esters in excellent yields.
Photophysics of Single PPV Derivative Polymers
Authors: Liang J. J. , Hsu J. H. , Lim T. S. , White Jonathon David 
Published: May 2015

AbstractConjugated polymers are unique subjects composed of many excitons localized at individual segments. Migration of excitation is strongly correlated with the chain conformation. We studied the PPV derivative polymers, MEH‐PPV and DOO‐PPV, with different chain lengths to probe the relation between the conformation of, and exciton migration in, single polymers. Photo‐quenching of individual conjugated segments was used to provide information on the exciton migration process. A phenomenological model based on the polymer as a collection of conjugated segments has been developed to explain the observation. The purpose of this paper is not to provide an exhaustive account of research in the field but rather to emphasis the unique contributions of the group of Prof. W. S. Fann.
Thermodynamic and Kinetic Studies of a Stable Imperfect DNA Triplex by Spectroscopic and Calorimetric Methods
Authors: Wey Ming‐Tsai , Lyu Ping‐Chiang , Kan Lou‐Sing 
Published: May 2015

AbstractAn imperfect DNA triplex, containing a pyrimidine/purine duplex with two sites of purine/pyrimidine base pair inversions, is formed and recognized. The unusual triplex is examined for the possibility of triplex DNA formation in a living system by way of non‐ideal sequence matching. The duplex part of it consists of a DNA oligomer with 17 nucleotidyl units, 5′‐TTCTTCTGATTCTCTCC‐3′ (C), which has two purine bases flanked by fifteen pyrimidine bases. The sequence of oligomer C is picked from a segment of cell cycle protein cdc25 gene (696 to 712) in Pneumocystis jirovecii, a yeast‐like parasitic fungus, which can cause pneumonia (PCP) in patients with impaired immunity. The complementary oligomer, 5′‐GGAGAGAATCAGAAGAA‐3′ (W), forms a DNA duplex WC with C, accompanied by CG/GC and TA/AT base pair inversions, in contrast to homo pyrimidine/purine duplexes. A third strand, 5′‐CCTCTCTTAGTCTTCTT‐3′ (H), combines with WC, to give an imperfect, but stable, triplex WCH+.UV absorption, circular dichroism, and native gel electrophoresis mobility shift assay are used to monitor the reactions at each stage. The triplex is stable in mild acidic solution, with a 1:1:1 stoichiometric ratio and a UV melting temperature (Tm) of 47.3 °C at pH 4.5. Isothermal titration calorimetry (ITC) and surface Plasmon resonance (SPR) unravel the thermodynamic information (ΔH = −123.1 kcal mol−1, ΔS = −378 cal mol−1K−1 and ΔG = −10.5 kcal mol−1) and kinetic rate constants (ka = 3.71 × 104 M−1 s−1 and kd = 7.49 × 10−4 s−1), respectively, for the WCH+ triplex formation process. WCH+ is termed an imperfect triplex since it contains two non‐canonical, non‐purine/purine/pyrimidine or non‐pyrimidine/purine/pyrimidine, base triads in the middle. This is the first time an imperfect but stable triplex, containing two purine bases in the middle of a pyrimidine‐rich strand (H), is formed and studied. The fact that an imperfect but stable DNA triplex can be formed gives great promise for drug design through more flexible targeting capabilities with much less stringent requirements, e.g., designs against Pneumocystis jirovecii using triplex formation in our example.
Spectroscopic Study of Organic Light‐Emitting Polymers: A Review
Authors: Chang Railing , Hayashi Michitoshi , Lin S. H. 
Published: May 2015

AbstractIn this review paper, we theoretically investigate the optical properties of the organic light‐emitting polymer (OLEP). Despite of its enormous size, OLEP is described well by the oligomer model because of the imperfect backbone structure. By using the molecular exciton theory, we calculate the energy level of S1 states and Huang‐Rhys factor of oligomer which decrease with its chain length. The spectral profiles for oligomer thus can be readily calculated and used to explain the absorption and PL for OLEP in dilute solution with a chain length distribution described by a Gaussian function. Moreover we show that the luminescence of OLEP in high concentration solution as well as thin film is mainly contributed by the interchain states. In the ultrafast time‐resolved PL spectrum, we propose a model in which the dynamic processes such as energy transfer, charge transfer, and vibrational relaxation are treated in an equal‐footing manner, and find that in the high energy region the states in a thin film of OLEP is dominated by the intrachain species. In addition, we discuss the nonradiative transitions occurring in OLEP.
One‐Pot Three‐Component Synthesis of 6‐Bromoquinolines and 6‐Iodoquinolines
Authors: Wu Li‐Qiang , Wang Xiao , Ma Wei‐Wei , Yan Fu‐Lin 
Published: May 2015

AbstractThree‐component one‐pot synthesis of some novel 6‐bromoquinolines 5a‐5h involving the treatment of 2‐aminobenzophenone, α‐methylene carbonyl compounds, and tetrabutyl‐ammonium tribromide was achieved, and this reaction was extended to the preparation of 6‐iodoquinolines 6a‐6e by a three‐component reaction 2‐aminobenzophenone, α‐methylene carbonyl compounds, and benzyltrimethylammonium dichloroiodate in the presence of ZnCl2.
A Simple Method to Prepare Methacrylate‐Based Capillary Monolithic Column Using Microwave Irradiation
Authors: Zhang Yu‐Ping , Chen Na , Gong Wen‐Jun , Yang Sheng‐Kai 
Published: May 2015

AbstractA methacrylate‐based monolith was initially prepared in fused‐silica capillary, using microwave irradiation. The electrophoretic and chromatographic behaviors of the prepared capillary monolithic columns were comparatively evaluated in the modes of pressure‐assisted capillary electrochromatography, capillary electrochromatography and low pressure‐assisted liquid chromatography. Baseline separation of the model analytes was, respectively, achieved with the lowest theoretical heights up to 17.0 μm, 28.4 μm and 16.3 μm for thiourea. A scanning electron micrograph of a cross‐section of the capillary column showed that the monolith was formed in the center of the capillary and adhered to the column inner wall.
Determination of Magnesium and Calcium in Biological Samples by Potentiometric Stripping Analysis
Authors: Wu Xian‐Li , Zhou Hong‐Bi , Wang Shu‐Jie , Ye Bao‐Xian 
Published: May 2015

AbstractA new and simple method for determination of calcium and magnesium in human plasma and hair samples was investigated by using potentiometric stripping analysis. The replacement reactions between Ca2+ and Zn‐EGTA (Ethylene glycol‐bis‐(2‐aminoethyl)tetraacetic acid) complex and between Mg2+ and Zn‐EDTA (Ethylenediamine tetraacetic acid disodium salt) complex were utilized. The determinations were carried out in NH4Cl‐NH3 buffer solutions of pH 9.54 for calcium and of pH 10.18 for magnesium, respectively. Potential and time data were digitally converted into dtdE−1, and E was plotted vs. dtdE−1. Quantitative analysis was carried out by the method of standard additions. Linearity for determination of magnesium was found to be in the range of 6∼120 μg L−1 with a correlation coefficient of 0.997 (n = 6); and for determination of calcium in the range of 10∼250 μg L−1 with a correlation coefficient of 0.995 (n = 6). The detection limit of 4 μ gL−1 was found for both magnesium and calcium determination. This proposed method has been used for determining calcium and magnesium in biological samples with good recoveries and well accord with the results of Inductively Coupled Plasma‐Atomic Emission Spectrometry (ICP‐AES).
Turning Low Barrier Hydrogen Bonds on and Off
Authors: Lankau Timm , Yu Chin‐Hui 
Published: May 2015

AbstractThe hydrogen bond in the [HDihH‐Fda]+ ion (HDih: 4,5‐dihydro‐1H‐imidazole, Fda: 1‐fluoro‐N,N‐dimethylmethaneamine) can be an ordinary single well hydrogen bond (HB) or a low barrier hydrogen bond (LBHB) depending on the orientation of the CH2F group in the Fda molecule. Both domains on the cluster's potential energy surface are well separated from each other by a 10 kcal/mol high barrier, which turns the CH2F group into a switch for the LBHB. The conformers with a LBHB are generally higher in energy than their counterparts with a standard HB, which suggests that the LBHB is not necessarily the more stable bond.
Preparation of Heteropoly Acid/Porous Hybrid Materials and Investigation of their Catalytic Behavior in the Synthesis of Perimidine
Authors: Zendehdel M. , Mobinikhaledi A. , Alikhani H. , Jafari N. 
Published: May 2015

AbstractA series of hybrid heteropoly acids (HPA) were prepared. The HPA/NaY and HPA/NaY/MCM‐41 hybrids of the synthesized catalysts were characterized using XRD, BET, TGA, SEM and FT‐IR techniques. The results show that reasonable amount of HPA in HPA/NaY and HPA/NaY/MCM‐41 hybrids remains even after washing with water, which indicates that heteropoly anions were strongly bonded to the porous materials. The catalytic properties of the hybrid catalysts were examined for the preparation of 2‐(4‐nitrophenyl)‐2,3‐dihydro‐1H‐perimidine. The yield for perimidine by different catalysts was in order of HPA/NaY > HPA/NaY/MCM‐41 > NaY > HPA > MCM‐41.
Molecular Complexation between Iodine(III) Chloride and Meso‐tetraarylporphrins: Synthesis, Spectroscopic Characterization and Photoluminescence Study
Authors: Dehghani Hossein , Sahba Reyhaneh , Afrooz Malihe , Mollaei Halimeh 
Published: May 2015

AbstractIodine(III) chloride and free base para‐substituted meso‐tetraarylporphyrins (H2t(4‐Xp)p, X = OCH3, CH3,CH(CH)3, H, Cl) react at mild conditions for formation of [(ICl3)H2t(4‐Xp)p] molecular complexes. The very close correspondence between the UV‐VIS and (1H, 13C) NMR spectra of these complexes and molecular complexes of porphyrins with various acceptors indicated that two lone pairs of the pyrrolenine nitrogens in the tilted porphyrin macrocycle bonded to an iodine(III) center of ICl3.
Capillary Electrophoresis Determination of Berberine in Pharmaceuticals with End‐Column Electrochemiluminescence Detection
Authors: Du Jian‐Xiu , Wang Min 
Published: May 2015

AbstractCapillary electrophoresis with end‐column electrochemiluminescence (ECL) detection was applied to the determination of berberine, which causes an enhancement of the ECL of tris(2,2‐bipyridyl)ruthenium(II). The assay is accomplished within 4 min with an injection volume of 3.3 nL. The linear analytical range is from 2.0 × 10−8 to 1.0 × 10−6 g mL−1 with a detection limit of 5 × 10−9 g mL−1. The relative standard deviations of the ECL signal and the migration time are 4.4% and 2.7% for 5.0 × 10−7 g mL−1 berberine solution (n = 7). The method was applied to the determination of berberine in tablets and in rhizoma coptidis.