Four-membered ring cyclic ketene –O,O–, –O,S–, –O,N–, –S,S–, –S,N–, and –N,N–acetals and their corresponding cations: a computational study

A systematic computational study of four-membered cyclic ketene –O,O–, –O,S–, –O,N–, –S,N– and –N,N-acetals as well as their protonated analogs have been performed at the second order M?ller Plesset level with a polarized triple zeta basis set. The main purpose of this study was to make predictions about the nucleophilicity of these systems and the variations in nucleophilicity with the hetero atoms. Our calculations suggest that all six target molecules are good nucleophiles, and that the N,N analog is the strongest and the S,S analog the weakest nucleophile. Our results include molecular geometries, bond lengths, proton affinities, vibrational frequencies, and calculated charges.     

Reactivity of the Ge–H,Sn–H,P–H,and Se–H Bonds in Radical Abstraction Reactions

The experimental data for the liquid- and gas-phase reactions of atoms and radicals with organoelement compounds R _{n – 1}E–H

Reinvestigation of the paracetamol–caffeine,aspirin–caffeine,and paracetamol–aspirin phase equilibria diagrams

Many drug candidates are poorly soluble. The formation of solid dispersion can improve their solubility, consequently their bioavailability. For this purpose, the use of eutectic mixtures is well known in the pharmaceutical field. At the eutectic composition, both components are in reduced particle size and well dispersed. In this work, we focus on the combination of paracetamol, aspirin, and caffeine, which is highly effective for the treatment of migraine headache pain. We have reinvestigated the paracetamol–caffeine, aspirin–caffeine, and paracetamol–aspirin phase equilibria diagrams taking into account the polymorphism of caffeine, paracetamol, and aspirin. The three phase diagrams are determined using X-ray diffraction and the differential scanning calorimetry from the binary mixtures. It is concluded that the paracetamol–caffeine and aspirin–caffeine systems are similar and exhibit two invariants, one eutectic and one metatectic. The paracetamol–aspirin phase diagram reveals the formation of one eutectic. The composition of the three eutectics formed is confirmed by the related Tamman’s triangles. No compound formation is found in the three systems.     

Application of CE–ICP–MS and CE–ESI–MS in metalloproteomics: challenges,developments, and limitations

Application of capillary electrophoresis (CE) as a high-resolution separation technique in metalloproteomics research is critically reviewed. The focus is on the requirements and challenges involved in coupling CE to sensitive element and molecule-specific detection techniques such as inductively coupled plasma mass spectrometry (ICP–MS) or electrospray ionisation mass spectrometry (ESI–MS). The complementary application of both detection techniques to the structural and functional characterisation of metal-binding proteins and their structural metal-binding moieties is emphasised. Beneficial aspects and limitations of mass spectrometry hyphenated to CE are discussed, on the basis of the literature published in this field over the last decade. Recent metalloproteomics applications of CE are reviewed to demonstrate its potential and limitations in modern biochemical speciation analysis and to indicate future directions of this technique.     

Cryoscopic Studies of the Uranyl Sulfate–Water, Uranyl Nitrate–Water, and Uranyl Nitrate–Nitric Acid–Water Systems

Freezing point lowerings of aqueous solutions of uranyl sulfate in the concentration range m 0.40 mol-kg^–1 and the activity and osmotic coefficients, which were calculated using the Pitzer equations for 2:2 electrolytes, are presented. Crystallization temperatures are reported for 0 to 13 molar nitric acid and 10–150 g uranium per liter uranyl nitrate–nitric acid–water solutions.     

Design,synthesis, and characterization of fullerene–peptide–steroid covalent hybrids

The present study reports the synthesis, spectral characterization, self-assembly properties, and preliminary in vitro study of antioxidant capacity of two triple covalent hybrids consisting of fullerene C₆₀, peptide, and steroidal moiety. Previously synthesized fulleropyrrolidinic acid and pregnenolone were connected by peptide linker using a multistep DCC/DMAP and/or EDC/HOBT esterification/amidation procedure. The hybrids were characterized by comparative analysis of spectroscopic data obtained from FTIR, UV–vis, HRMS, and extensive NMR experiments (¹H, ¹³C, COSY, HSQC, and HMBC). The self-assembling properties and morphology of triads samples prepared by drop-drying method were examined by scanning electron microscopy (SEM). Preliminary in vitro antioxidant activity was studied by Ferrous ion Oxidation-Xylenol orange (FOX) method.     

Bulk properties and hydration numbers of components of water–salt,water–urea,and water–urea–salt systems

With an increase in the concentration of additives, the hydration numbers of compounds decrease. Thus, in a saturated 54.6% solution, urea loses approximately 3/4 of the initial amount of water, forming an aquacomplex of the composition (NH₂)₂CO?H₂O. In a supersaturated 44% solution, the sodium chloride aquacomplex is dehydrated by 2/3, and in a supersaturated 67% solution, sodium sulfate is dehydrated by 5/6. The density of these solutions is 1.354÷1.360 g/cm³ (44% NaCl) and 1.800÷1.849 g/cm³ (67% Na₂SO₄). In a saturated urea solution, NaNO₃, NaCl, and Na₂SO₄ complexes lose 53÷55% of hydration water. It is shown that the interactions in the binary water–urea system somewhat increase the hydration number of the salts (structural hydration). The hydration water density, a structurally important characteristic, increases in the series of solutions of urea, NaNO₃, NaCl, and Na₂SO₄. In the same series of additives, the excess volume of binary water–urea and water–salt systems becomes more negative.     

Contracted polarization functions for the atoms Ca, Ga–Kr, Sr, and In–Xe

 Contracted Gaussian-type function sets are proposed for polarization functions of the atoms Ga–Kr and In–Xe. We also report polarization functions for Ca and Sr. A segmented contraction scheme is used for its compactness and computational efficiency. The contraction coefficients and orbital exponents are fully optimized to minimize the deviation from accurate atomic natural orbitals. The present polarization functions yield more than 99% of atomic correlation energies predicted by accurate natural orbitals of the same size. Received: 23 February 2001 / Accepted: 19 April 2001 / Published online: 13 June 2001     

离子色谱法测定生活饮用水中的F~–,Cl~–,SO_4~(2–)和NO_3~–

建立了电导检测–离子色谱法同时测定生活饮用水中F–,Cl–,SO42–,NO3–的方法。选择30 mmol/L Na OH溶液为淋洗液,流量为1.40 m L/min,检测器电流为106 m A。F–的线性范围为0.15~2.0 mg/L,Cl–,SO42–,NO3–的线性范围为3.00~40.0 mg/L,4种离子的线性相关系数均大于0.999 5。F–,Cl–,SO42–,NO3–的方法检出限分别为0.02,0.13,0.14,0.02 mg/L,加标回收率在95.2%~103.0%之间。对环境标准204715进行了平行测试,各阴离子测定值均在标准值的不确定度范围内,测定结果的相对标准偏差小于2%(n=6)。该方法灵敏、准确、快速,可用于生活饮用水中F–,Cl–,SO42–,NO3–的同时测定。     

Donor–acceptor perylenediimide–ferrocene conjugates: synthesis,photophysical, and electrochemical properties

Donor–acceptor, perylenediimide–ferrocene conjugates have been synthesized by Suzuki, and Sonogashira coupling reactions. The photophysical and electrochemical properties of these conjugates are discussed. It has been shown that fluorescence as well as the electron affinity of the perylenediimide can be tuned by attaching the appropriate ferrocenyl derivatives.     

Analysis of Deoxynivalenol,Nivalenol, Zearalenone in Food by LC–APCI–MS

The detection of mycotoxins is an important task for analytical analysis, as they are a source of contaminants in foods today. The very small amounts of toxic mycotoxins (zearalenone, deoxynivalenol) make it important to determine the most reliable analytical methods. There are several options for the detection of mycotoxins, LC–API–MS techniques being the most common ones. The aim of the present determination is to give an overview on the application of LC–(API)-MS in the analysis of frequently occurring and highly toxic mycotoxins, such as deoxynivalenol, nivalenol and zearalenone, in organic foods. The limits of these three toxins in foods are very low: deoxynivalenol 1,250 μg kg^?1, nivalenol 0.9 μg kg^?1 of body weight, zearalenone 100 μg kg^?1.     

Tetra-nuclear copper complex having P–N–P ligand to P–O–P ligand – synthesis,structural, and mechanistic studies

We report the synthesis and structures of three copper(I) complexes, [Cu₄(μ₃-Cl)₂(μ₂-Cl)₂{μ₂-(2,6-Me₂C₆H₃N(PPh₂)₂)}₂] (2), [Cu₄(μ₃-Cl)₂(μ₂-Cl)₂{μ₂-(Ph₂POPPh₂)}₂] (4), and [Cu₂(μ₂-Cl)₂(μ₂-PPh₂OPPh₂)(η¹-Ph₂PP(=O)Ph₂)(PPh₃)] (5), and one cobalt complex, [(CoCl₂){μ₂-2,6-Me₂C₆H₃N(PPh₂)₂}₂][CoCl₃NH₂(2,6-Me₂Ph)] (3). Tetra-nuclear copper complex 2 was prepared in good yield by the reaction of bis(diphenylphosphino)-2,6-dimethylaniline [2,6-Me₂C₆H₃N(PPh₂)₂] (1) with copper(I) chloride along with triphenylphosphine in methanol. Adding a calculated amount of water and dichloromethane mixture (1?:?10) to 2 produced a second tetra-nuclear copper(I) complex, 4, with a P–O–P backbone, along with a small amount of the unsymmetrical copper(I) complex 5. The cobalt complex 3 was obtained by reaction of 1 with cobalt(II) chloride. The solid-state structures of 2–5 were established by single-crystal X-ray diffraction analysis. In the solid state, both 2 and 4 form a tetra-nuclear copper core. In the ³¹P{¹H} NMR study, we observed the conversion of 2, with P–N–P backbone, to 4, with P–O–P backbone.     

New ciprofloxacin–dithiocarbamate–benzyl hybrids: design,synthesis, antibacterial evaluation,and molecular modeling studies

Research on Chemical Intermediates - We designed and synthesized a series of new ciprofloxacin–dithiocarbamate–benzyl hybrids 5a–n as potential antibacterial agents. All of the...     

Synthesis,characterization and electrocatalytic activity for ethanol oxidation of carbon supported Pt,Pt–Rh,Pt–SnO2 and Pt–Rh–SnO2 nanoclusters

Nanoclusters of Pt, Pt–Rh, Pt–SnO₂ and Pt–Rh–SnO₂ were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO₂/C catalyst: solid solution of Rh in Pt and SnO₂. The activity of Pt–Rh–SnO₂/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO₂/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H₂SO₄ concentrations (0.02–0.5 M) showed that Pt–Rh–SnO₂/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application.     

Thermochemistry of Pd–In,Pd–Sn and Pd–Zn alloy systems

The standard enthalpy of formation of several Pd–M alloys (M = In, Sn and Zn) has been measured using a high temperature direct drop calorimeter. The reliability of the calorimetric results has been determined and supported by using different analytical techniques: light optical microscopy, scanning electron microscopy equipped with electron probe microanalysis (EPMA with EDS detector) and X-ray powder diffraction analysis. The values of Δ_fH (kJ/mol atoms) for the following phases were obtained for the formation in the solid state at 300 K: PdIn (49 at.%In): ?69.0 ± 1.0; Pd₂In₃ ?57.0 ± 1.0; Pd₃In₇: ?43.0 ± 1.0; PdSn₂: ?50.0 ± 1.0; Pd₂Zn₉ (77 at.%Zn): ?33.7 ± 1.0; Pd₂Zn₉ (78 at.%Zn): ?34.0 ± 1.0; Pd₂Zn₉ (80 at.%Zn): ?35.0 ± 1.0. The results show exothermic values which increase from the Pd–Zn to the Pd–Sn and Pd–In systems; the data obtained have been discussed in comparison with those available in literature.     

Electronic, optical, and charge transfer properties of donor–bridge–acceptor hydrazone sensitizers

The ground state geometries have been computed by using density functional theory (DFT) at B3LYP/6-31G*, B3LYP/6-31G**, and PCM-B3LYP/6-31G* level of theories. The highest occupied molecular orbitals (HOMOs) are delocalized on whole of the molecule and the lowest unoccupied molecular orbitals (LUMOs) are localized on the tricarbonitrile. The lowest HOMO and LUMO energies have been observed for Dye1 while highest for Dye4. The LUMO energies of Dye1–Dye4 are above the conduction band of TiO₂ and HOMOs are below the redox couple. The absorption spectra have been computed in solvent (methanol) and without solvent by using time-dependant DFT at TD-B3LYP/6-31G*, TD-B3LYP/6-31G**, and PCM-TD-B3LYP/6-31G* level of theories. The calculated maximum absorption wavelengths of the spectra in methanol are in good agreement with experimental evidences. The maximum absorption wavelengths of new designed sensitizers are red shifted compared to parent molecule. The electronic coupling constant and electron injection have been computed by first principle investigations. The improved electronic coupling constant and electron injection revealed that new modeled systems would be efficient sensitizers.     

Glass transition, fragility, and structural features of amorphous nickel–tellurate–vanadate samples

The experimental FTIR spectra and DSC curves of the ternary 40TeO₂–(60?x)V₂O₅–xNiO glasses with 0 ≤ x ≤ 30 (in mol%) have been investigated. The glass transition properties that have been measured and reported in this paper, include the glass transition temperature (T _g), glass transition width (ΔT _g), heat capacity change at glass transition (ΔC _P) and Fragility (F). Thermal stability, fragility, and glass-forming tendency of these glasses have been estimated. Also, Poisson’s ratio (μ) and IR spectra of the presented systems have been investigated, to determine relationship between chemical composition and the thermal stability or to interpret the structure of glass. In addition, Makishima and Makenzie’s theory was applied for determination of Young’s modulus, bulk modulus, and shear modulus, indicating a strong relation between elastic properties and structure of glass. In general, results of this work show that glasses with x = 0 and 30 have the highest shear and young’s modulus which make them as suitable candidate for the manufacture of strong glass fibers in technological applications; but it should be mentioned that glass with x = 30 has higher handling temperature and super resistance against thermal shock.     

LC–MS–MS Determination of Rotenone, Deguelin, and Rotenolone in Human Serum

For the first time we report a rapid and sensitive LC–MS–MS method for quantification of rotenone, deguelin, and rotenolone in human serum. The analytical procedure involves extraction with ethyl acetate without further clean-up. The active ingredients were separated on a C₈ reversed-phase column by isocratic elution. Eleven simultaneous transitions of precursor ions were monitored. Excellent selectivity and sensitivity enables quantification and identification of low levels of rotenoids (LOD 2 ng mL^?1, LOQ 5 ng mL^?1) in human serum.     

Sputtered,electroless, and rolled palladium–ceramic membranes

Three techniques were used to produce palladium–ceramic (Pd–ceramic) composite membranes for hydrogen separation and production. They are sputtering, electroless deposition and rolling of thin Pd alloy films over ceramic porous tubes.After studying and developing the three coating techniques, an extensive testing and characterizing work was carried out on these thin film composite membranes. The results show that in the sputtered (0.5–5 μm) and electroless (2.5–20 μm) composite membranes, the thermal cycling of the hydrogenated metallic layer produces membrane failures. Such failures are characterized by crack formation and metal film peeling. This fact has been explained by an evaluation of the shear stresses at the metal–ceramic interface due to the differential elongation between the palladium (Pd) coating and the ceramic support under thermal cycling and hydrogen loading. The rolled membranes (50–70 μm), however, because of the particular coating solution, have shown a complete hydrogen selectivity and good chemical and physical stability in long-term tests.