1-甲基-3,5-二苯基吡唑啉在氯化铜催化下的氧化脱氢反应(Ⅱ)——计量反应与氧分子的作用阶段

我们在合成1-甲基-3,5-二苯基吡唑(MDPP)的过程中,发现氯化铜、氯化钴等化合物对1-甲基-3,5-二苯基吡唑啉(H₂MDPP)的氧化脱氢反应具有优异的催化性能,对以氯化铜为催化剂的反应机理进行了初步研究,获得了反应过程中形成铜(Ⅱ)H₂MDPP、铜(Ⅱ)MDPP和铜(Ⅱ)H₂MDPP分子氧配合物的证据。另外,在催化氧化反应体系中曾检测到一价铜,这显然是氯化铜的还原产物,故本文对氯化铜与H₂MDPP的计量反应及在催化反应中氧分子参与作用的阶段进行了研究。     

Measurement of absolute absorption cross sections for nitrous acid (HONO) in the near-infrared region by the continuous wave cavity ring-down spectroscopy (cw-CRDS) technique coupled to laser photolysis

Absolute absorption cross sections for selected lines of the OH stretch overtone 2ν(1) of the cis-isomer of nitrous acid HONO have been measured in the range 6623.6-6645.6 cm(-1) using the continuous wave cavity ring-down spectroscopy (cw-CRDS) technique. HONO has been generated by two different, complementary methods: in the first method, HONO has been produced by pulsed photolysis of H(2)O(2)/NO mixture at 248 nm, and in the second method HONO has been produced in a continuous manner by flowing humidified N(2) over 5.2 M HCl and 0.5 M NaNO(2) solutions. Laser photolysis synchronized with the cw-CRDS technique has been used to measure the absorption spectrum of HONO produced in the first method, and a simple cw-CRDS technique has been used in the second method. The first method, very time-consuming, allows for an absolute calibration of the absorption spectrum by comparison with the well-known HO(2) absorption cross section, while the second method is much faster and leads to a better signal-to-noise ratio. The strongest line in this wavelength range has been found at 6642.51 cm(-1) with σ = (5.8 ± 2.2) × 10(-21) cm(2).     

Stereochemical elucidation and total synthesis of dihydropacidamycin D, a semisynthetic pacidamycin.

Hydrogenation of the C(4') exocyclic olefin of the pacidamycins has been shown to produce a series of semisynthetic compounds, the dihydropacidamycins, with antimicrobial activity similar to that of the natural products. Elucidation of stereochemistry in the pacidamycins has been completed through a campaign of natural product degradation experiments in combination with the total synthesis of the lowest-molecular weight dihydropacidamycin, dihydropacidamycin D. The stereochemical identities of the tryptophan and two alanine residues contained in pacidamycin D have been shown to be of the natural (S) configuration, and the unique 3-methylamino-2-aminobutyric acid contained in this series of antibiotics has been shown to be of the (2S,3S) configuration. Finally, the stereochemistry obtained by hydrogenation of the C(4')-C(5') exocyclic olefin has been shown to be (R) at the C(4') nucleoside site.     

Determination of cadmium and copper with ET-AAS after electrochemical deposition on a graphite electrode

The electrodeposition of cadmium and copper on a special graphite disk electrode has been performed at controlled potential. The electrode with the deposit has been inserted into the graphite atomizer HGA-400 by an adapted automatic sampler for the final determination by ET-ASS. The sensitivity of determination has been 0.371 (microg l(-1))(-1) for cadmium and 0.025 (microg l(-1))(-1) for copper for 2 min electrodeposition and increased linearly with the time of deposition. The limit of detection (3s(bl)) has been 7.9 ng l(-1) Cd(2+) and 0.11 microg l(-1) Cu(2+) for 2 min deposition and it has been improved with increased time of electrodeposition. The technique has been applied to the determination of both metals in seawater and to speciation in the presence of EDTA complexing agent.     

Application of long-lived luminescence for detection in liquid chromatography

Summary Quenched and sensitized lanthanide luminescence as detection in liquid chromatography has been investigated. An important advantage in comparison with phosphorescence is that the long-lived luminescence as applied does not require deoxygenation of the samples. In order to obtain a high luminescence intensity Tb(III) complexes with acetylacetonate have been formed, after which indirect excitation of Tb(III) can be realized via the ligands. The potential of Tb(III) luminescence as a detection method in ion chromatography has been shown for chromate, which is an efficient quencher. Sensitizing of the Tb(III) luminescence has been applied for thiol-containing analytes. These compounds are derivatized with maleimidyl salicylic acid to complexes that sensitize the Tb(III) luminescence. From a comparison of the results obtained with normal fluorescence detection and time-resolved sensitized Tb(III) luminescence detection it has become clear that the last method has a higher sensitivity, but in particular a higher selectivity.     

Fluorimetric determination traces of aluminium in soil extracts

Salicylaldehyde picolinoylhydrazone (SAPH) form a fluorescent complex with aluminium (lambda(ex) = 384 nm, lambda(em) = 468 nm) in acidic medium (stoichiometry 1:3, Al:SAPH). Two procedures based on the direct or standard additions methods has been proposed for the determination of concentrations down to 1-2 mug/dm(3) of Al(III). The effects of 72 ions in the method has been evaluated and different masking agent reactions have been tested. The method has been used satisfactorily for the determination of aluminium at a level of mug/dm(3) in acetate extracts of several agricultural soils. The method has been compared favourably with ICP spectroscopy emission.     

Determination of catechin isomers in human plasma subsequent to green tea ingestion using chiral capillary electrophoresis with a high-sensitivity cell

A simple and reliable analytical electrophoretic method using chiral capillary electrophoresis (CCE) with a high-sensitivity cell of special design has been established for simultaneous determination of (+)-catechin (C) and (-)-epicatechin (EC) in aqueous and human plasma media. The application of a capillary with high-sensitivity cell has led to an improvement of 10-fold and 5-fold time-corrected peak area over a standard cell and a capillary with bubble cell, respectively. Analysis has involved the electrophoretic separation of C and EC in less than 4.0 min at 210 nm. The running buffer consist of 50.0 mmol L(-1) borate buffer with 1.0 mmol L(-1) beta-cyclodextrin at pH 8.5. CCE system has been proved for its intended use by applying procedure starting from calibration of CE instrument into validation of all experimental parameters. The resolution between catechin isomers under optimal conditions has been found to be more than 3.0. The detection limits of C and EC have been calculated to be 3.2 and 1.0 ng mL(-1), respectively. Good linearity has been obtained with correlation coefficient (r(2)) ranging between 0.995 and 0.996 at 99% confidence level (CL). Application of the proposed method to human plasma after ingestion of green tea has successfully been achieved and has statistically been proved. The unchanged amounts of C and EC in plasma were about 17.4 and 1.8% of the administered dose after 2 h of starting tea ingestion. The detection limits of C and EC in human plasma at 210 nm were 4.1 and 1.5 ng mL(-1), respectively.     

一系列多核Mo(W)-Cu(Ag)-S簇合物的低热固相合成、成簇规律和机理的研究

本文报道了一系列多核Mo(W)-Cu(Ag)-S族合物的低热固相合成, 发现硫代钼(钨)酸铵与铜(银)的成簇规律主要与固相反应温度密切相关, 提出了四核至七核Mo(W)-Cu(Ag)-S簇合物的可能成簇机理。     

In-situ heating study on the structural change of surfactant-templated germanium oxide mesostructure

Mesostructured germanium oxide has been well-synthesized by using a surfactant-templated approach under basic hydrothermal conditions. The cationic surfactant cetyltrimethylammonium bromide (CTAB) has formed nanotubes with uniform diameter of about 3.2 nm. Blanket-like morphology of the as-prepared sample has been observed with transmission electron microscopy (TEM). High-resolution TEM image reveals that the nanotubes are connected with inorganic germanium oxide and have self-assembled into periodic mesostructure. In-situ heating X-ray diffraction (XRD) patterns confirm that the germanium oxide is in amorphous phase in the temperature range from room temperature (RT) to 700 degrees C. In-situ heating small-angle X-ray scattering (SAXS) presents the mesostructural change with temperature. The local atomic structures around germanium atom have been obtained with in-situ heating X-ray adsorption fine structure (XAFS) techniques. The stability of this mesostructure has been determined to be correlated with the cationic surfactant CTAB. The structural evolution from the GeO 2/NaOH aqueous solution, the as-prepared sample to the sample heated at 700 degrees C, has been described, and the formation mechanism of mesostructured germanium oxide has been discussed.     

Hydrogen and higher shell contributions in Zn2+, Ni2+, and Co2+ aqueous solutions: an X-ray absorption fine structure and molecular dynamics study

A detailed investigation of the hydration structure of Zn2+, Ni2+, and Co2+ in water solutions has been carried out combining X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. The first quantitative analysis of EXAFS from hydrogen atoms in 3d transition metal ions in aqueous solutions has been carried out and the ion-hydrogen interactions have been found to provide a detectable contribution to the EXAFS spectra. An accurate determination of the structural parameters associated with the first hydration shell has been performed and compared with previous experimental results. No evidence of significant contributions from the second hydration shell to the EXAFS signal has been found for these solutions, while the inclusion of the hydrogen signal has been found to be important in performing a quantitative analysis of the experimental data. The high-frequency contribution present in the EXAFS spectra has been found to be due to multiple scattering (MS) effects inside the ion-oxygen first coordination shell. MD has been used to generate three-body distribution functions from which a reliable analysis of the MS contributions to the EXAFS spectra of these systems has been carried out.     

Geometrical structure of benzene and naphthalene: ultrahigh-resolution laser spectroscopy and ab initio calculation

Geometrical structures of the isolated benzene and naphthalene molecules have been accurately determined by using ultrahigh-resolution laser spectroscopy and ab initio calculation in a complementary manner. The benzene molecule has been identified to be planar and hexagonal (D(6h)) and the structure has been determined with accuracies of 2 × 10(-14) m (0.2 mA?; 1 A? = 1 × 10(-10) m) for the C-C bond length and 1.0 × 10(-13) m (1.0 mA?) for the C-H bond length. The naphthalene molecule has been identified to be symmetric with respect to three coordinate axes (D(2h)) and the structure has been determined with comparable accuracies. We discuss the effect of vibrational averaging that is a consequence of zero-point motions on the uncertainty in determining the bond lengths.     

Evaluation of some as-triazines and re-evaluation of PDT and ferrozine as reagents for spectrophotometric determination of ruthenium

A sensitive method for the spectrophotometric determination of ruthenium with the ferroinyielding as-triazines has been developed. This method has several advantages; complete reduction of ruthenium species to ruthenium(II) can be achieved by the recommended procedure, which shortens the colour development time, saves the unnecessary use of several-fold excess of the reagent and the molar absorptivity is increased significantly. A few of the new as-triazines together with the commercially available Ferene(R) have been evaluated as ruthenium(II) chromogens. 3-(2-Pyridyl)-5,6-diphenyl-as-triazine (PDT) and ferrozine, a sulphonated derivative of PDT, have been re-evaluated by the new method. It has been observed that the as-triazine acting as a bidentate ligand forms a tris-complex with ruthenium(II) similar to its reaction with iron(II).     

Preparation and properties of a new chelating resin containing 1-nitroso-2-naphthol as the functional group

A macroreticular polystyrene-based chelating ion-exchanger containing 1-nitroso-2-naphthol as the functional group has been synthesized. The exchange-capacity of the resin for a number of metal ions such as copper(II), iron(III), cobalt(II), nickel(II), palladium(II) and uranium(VI) as a function of pH has been determined. The sorption and elution characteristics for palladium(II) and uranium(VI) have been thoroughly examined with a view to utilizing the resin for separation and concentration of uranium and palladium. Uranium(VI) has been separated from a mixture of ten other metal ions by sorption on the chelating resin and selective elution with 0.5M sodium carbonate. Palladium(II) has been separated from various metal ions by selective sorption on the resin in 1M hydrochloric acid medium.     

Strongly coupled ruthenium-polypyridyl complexes for efficient electron injection in dye-sensitized semiconductor nanoparticles

Dynamics of interfacial electron transfer (ET) in the ruthenium-polypyridyl complex [{bis(2,2'-bpy)-(4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol)} ruthenium(II) hexafluorophosphate] (Ru-cat)-sensitized TiO(2) nanoparticles has been investigated using femtosecond transient absorption spectroscopy detecting in the visible and near-infrared region. It has been observed that Ru-cat is coupled strongly with the TiO(2) nanoparticles through its pendant catechol moiety. Electron injection has been confirmed by direct detection of electrons in the conduction band, cation radical of the adsorbed dye, and a bleach of the dye in real time as monitored by transient absorption spectroscopy. A single-exponential and pulse width limited (<100 fs) electron injection has been observed, and the origin of it might have been from the nonthermalized excited states of the Ru-cat molecule. The result gave a strong indication that the electron injection competes with the thermalization of the photoexcited states due to large coupling elements for the forward ET reaction. Back-ET dynamics has been determined by monitoring the decay kinetics of the cation radical and injected electron and also from recovery kinetics of the bleach of the adsorbed dye. It has been fit with a multiexponential function, where approximately 30% of the injected electrons are recombined with a time constant of <2 ps, again indicating large coupling elements for the charge recombination reaction. However, our results have shown relatively long-lived charge separation in the Ru-cat/TiO(2) system as compared to other organic dye-sensitized TiO(2) nanoparticles with similar interactions.     

Thermodynamic parameters for the molecular inclusion reaction of dulcin with beta-cyclodextrin. spectrofluorimetric determination of dulcin

The inclusion of dulcin in alpha- and beta-cyclodextrin has been studied by fluorescence spectroscopy. To quantitatively describe complex formation between the beta-cyclodextrin and dulcin, an association constant of 290 M(-1) at 21 degrees was obtained. The thermodynamics associated with the complex formation between dulcin and beta-cyclodextrin in aqueous solution has been studied. The obtained value of DeltaG(0) = -13.7 kJ/mole at 21 degrees , together with DeltaH(0) = -33.6 +/- 2.3 kJ/mole and DeltaS(0) = -67.2 +/-8.3 Jmole(-1) K(-1) indicate that dulcin has a very marked tendency to associate with beta-cyclodextrin in water. The inclusion complex of dulcin in beta-cyclodextrin has been used to determine dulein in the range 0.13-5 mug/ml the method has been applied to determine dulcin in soft drinks.     

Low temperature heat capacity and magnetic properties of UF3

The low temperature heat capacity of UF(3) has been measured using an adiabatic low temperature calorimeter in the temperature range from 10 to 350 K. These data are complemented at the lowest temperature region with data obtained with a Quantum Design PPMS-14 device in the temperature range from 0.5 to 20 K. Good agreement between both techniques has been found, and from these experimental results the absolute entropy of UF(3) at 298.15 K has been determined as 126.8 ± 2.5 J K(-1) mol(-1). On the basis of the specific heat data and the magnetization measurements performed on a SQUID device, a transition at 1.59 K attributed to Curie temperature of a ferromagnetic transition has been found in this study. This observation makes UF(3) a unique compound with an unusually low ferromagnetic ordering temperature.     

Functionalized electrospun mats from styrene-maleic anhydride copolymers for immobilization of acetylcholinesterase

A series of electrospun mats of styrene-maleic anhydride copolymers has been functionalized by modification with two types of spacers - a polymer with a flexible hydrophilic polyether chain (Jeffamine® ED) and a rigid low-molecular-weight spacer (р-phenylenediamine). The successful modification of the microfibrous mats with these bifunctional compounds has been proved by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. In a further step, acetylcholinesterase (AChE) has been covalently immobilized onto the modified mats using glutaraldehyde as a binding agent. The amount of bound protein and the specific activity of the immobilized AChE have been determined. The highest activity has been displayed by AChE covalently bound to Jeffamine-modified microfibrous mats. Moreover, the immobilized AChE is characterized by enhanced thermal and storage stability as compared to the free enzyme.     

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol from hydrochloric acid solutions

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol from 3 M hydrochloric acid solutions (with chloroform as a diluent) has been studied. Optimal extraction conditions have been found. The reagent has been shown to extract efficiently metal ion from solutions containing 3 M hydrochloric acid due to formation of coordination bond between gold(III) and the N4 atom of the triazole ring. The coordination mechanism of gold(III) extraction has been proposed on the basis of the data obtained. Concentration constants of extraction have been calculated, and the thermodynamic parameters of extraction have been determined.     

Triazole linked picolylimine conjugate of calix[6]arene as a sequential sensor for La3+ followed by F-

A new 1,3,5-tris-triazole linked picolylimine conjugate of calix[6]arene (L) has been shown to be selective toward La(3+) by turn on fluorescence with ～70-fold enhancement and emits blue, with a minimal detection limit of 65 ± 5 ppb (490 nM). The species of recognition has been modeled computationally to have a monocapped twisted square antiprism with a N(6)O(3) binding core about La(3+). The in situ complex of L with La(3+) recognizes F(-) via fluorescence quenching. The reversible response of sensing La(3+) and F(-) sequentially by L has been demonstrated.     

Analysis of pair interaction in a bipolar mesogen 4‐(4‐hydroxylbutyloxy)‐4′‐cyano‐biphenyl: A comparative study based on semiempirical and DFT methods

Structure of 4‐(4‐hydroxylbutyloxy)‐4′‐cyano‐biphenyl (H4CBP) molecule has been optimized using density functional B3LYP with 6‐31G (d) basis set taking crystallographic geometry as input. Using the optimized geometry, electronic structure of the H4CBP molecule has been evaluated on the basis of semiempirical methods and DFT calculations. Intermolecular interaction energy between a pair of H4CBP molecules has been evaluated by using Rayleigh–Schrodinger perturbation theory modified with multicentered multipole expansion method for the electrostatic part while dispersion and repulsion terms have been calculated using Kitaigorodskii formula. The results obtained through semiempirical and DFT calculations have been compared for various interacting conditions, viz.: (a) stacking, (b) in‐plane, and (c) terminal interactions. A comparative analysis of the results has been carried out with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011