Hydrothermal synthesis,thermal decomposition and optical properties of Fe2F5(H2O)(Htaz)(taz)(Hdma)

Crystal structure of Fe₂F₅(H₂O)(Htaz)(taz)(Hdma) which crystallizes in the triclinic system space group $\text{P}\overline{1}$ with unit cell parameters a = 8.8392(5) Å, b = 9.1948(5) Å, c = 9.5877(5) Å, α = 82.070(3)°, β = 63.699(3)°, γ = 89.202(3)°, Z = 2, and V = 690.91(7) ų, was synthesized under hydrothermal conditions at 393 K for 72 h, by a mixture of FeF₂/FeF₃, 1,2,4-triazole molecule (Htaz), and hydrofluoric acid solution (HF 4%) in dimethylformamide solvent (DMF). The main feature of this material is the coexistence of two oxidation states for iron atoms (Fe²⁺, Fe³⁺) in the unit cell, which associate by opposite fluorine corners of FeF₅N and FeF₂N₄ octahedra, and/or triazole molecule which originates the 2D produces material. The structure determination, performed from single crystal X-ray diffraction data, lead to the R₁/_WR₂ reliability factors 0.031/0.087. Thermal stability studies (TG/DTG/DTA) show that the decomposition provides in the temperature range 473–773 K and no mass loss was detected before 473 K. Mass spectrometry (MS) has been used. The optical absorption of the solid was measured at the corresponding λ_max using UV–vis diffuse-reflectance spectrum.     

Quaterpolymerization of Ethylene,Propylene, Dicyclopentadiene,and Methylcyclopentadienyl-5-endo-norborn-2-enyl-methane

Abstract

The quaterpolymerization of methylcyclopentadienyl-5-endo-norborn-2-enyl-methane with ethylene, propylene, and either endo- or exo-dicyclopentadiene was studied by using the catalyst system VAcac₃-Et₂AlCl. The influence of catalyst and polyenes concentrations, catalyst modifiers, and other polymerization parameters on the general properties of quaterpolymers was investigated. The polymers obtained showed a random distribution of the comonomeric units and the ability to covulcanize with 1,4-cis-polyisoprene.     

Binary and Ternary Copper(II) Complexes with NIPAAm/IA Copolymers and Aminoacids: Interpretation of UV‐Visible Spectra and Cyclic Voltammograms

The complex formations of homopolymers and copolymers of poly(N‐isopropyl acrylamide) (PNIPAAm), polyacrylamide (PAAm) and poly(itaconic acid) (PIA) with Cu(II) ions in aqueous solutions were studied by using UV‐visible spectra in the region of 200–1100 nm and cyclic voltammograms between ?0.800 V and 0.600 V. According to the optical and electrochemical spectra of the polymer‐ and copolymer‐Cu(II) complexes and their ternary complexes with alanine, i.e., absorptions and the shifts in the wavelength of the maximum absorptions, currents and potentials of the peaks in the pH range of 3–12, the intensities of anodic and cathodic peak currents of polymers containing IA groups decrease with increasing pH and they show maximum absorptions at lower wavelengths than do the homopolymers used in this work. The peak point of the visible band shifts from 800 to 650 nm, with increasing pH, while the intensity of the third anodic peak observed after pH=4 increases in the case of both Ala‐Cu(II) and its ternary solution with P(NIPAAm‐co‐IA, 9.8 mol%). Both the pH‐dependent shifts of maximum absorptions and the appearence of the third anodic peaks as the pH raised were interpreted as a presence of tetracoordinated Cu(II) complexes in the solution and on the electrode surface, involving combined carboxyl, amide and amine interaction.     

Kinetic Study on Models of the Noncatalyzed Reaction Between α, ω -Dicarboxypolyamide-11 and α, ω -Dihydroxypolyoxyalkylenes

The kinetics of the noncatalyzed reaction between α, ω -dicarboxypoly-amide-11 and α, ω -dihydroxypolyoxyalkylenes is investigated by using the reactions of 11-dodecylamidoundecanoic acid with 1-dodecanol, 2-tridecanol, α-dodecyl-ω-hydroxypolyoxyethylene or α-dodecyl-ω;-hydroxypolyoxypropylene as models. Kinetic data fit a 3rd overall order (2 in acid and 1 in alcohol). Rate constants and activation parameters are determined and compared.     

Influence of amidoammonium calix[4]resorcinarenes on methyl orange protolytic equilibrium: supramolecular indicator systems

Here, we report on the study of cationic amidoammonium calix[4]resorcinarenes 1–5 of various lipophilicity capable of binding acid–base indicator methyl orange (MO). We identified the contributions of macrocycle aggregation and conformational mobility in the binding of MO. The effective pK_a values of bound MO systematically decrease as the size and the packing density of the aggregates increase with an increase in calixresorcinarene lipophilicity. Consideration of a series of macrocycles clearly shows that large aggregates form most stable complexes, binding guests not on individual level but as aggregates. It was found that the most stable MO complex with 5 is formed due to electrostatic binding with ammonium groups of the macrocycle and incapsulation of MO in a hydrophobic layer of the aggregates. We have shown that competitive binding of MO and cationic surfactants by aggregates of 5 is suitable for visual/spectrophotometric detection of colourless anionic substrates.     

Synthesis and anion binding of 2-arylazo-meso-octamethylcalix[4]pyrroles

2-Arylazo-5,5,10,10,15,15,20,20-octamethylcalix[4]pyrroles (azo-OMCPs) have been synthesised by the reaction of calix[4]pyrrole with aryldiazonium chloride in 15–45% yields. The solution-state binding studies of the synthesised hosts were investigated by absorption spectroscopy and ¹H NMR in DMSO and CDCl₃, respectively. These receptors, appended with electron-donating and electron-withdrawing groups, displayed enhanced affinity and selectivity for fluoride anion. Well-defined colour change in the visible region of the spectrum was observed upon addition of fluoride ion in DMSO solution of azo-OMCPs. Detailed NMR studies in CDCl₃ revealed that azo-OMCPs with nitro and chloro groups have higher binding affinity for fluoride ion.

     

Prediction of CL-20 chemical degradation pathways,theoretical and experimental evidence for dependence on competing modes of reaction

Highest occupied and lowest unoccupied molecular orbital energies, formation energies, bond lengths and FTIR spectra all suggest competing CL-20 degradation mechanisms. This second of two studies investigates recalcitrant, toxic, aromatic CL-20 intermediates that absorb from 370 to 430?nm. Our earlier study (Struct. Chem., 15, 2004) revealed that these intermediates were formed at high OH^? concentrations via the chemically preferred pathway of breaking the C–C bond between the two cyclopentanes, thereby eliminating nitro groups, forming conjugated π bonds, and resulting in a pyrazine three-ring aromatic intermediate. In attempting to find and make dominant a more benign CL-20 transformation pathway, this current research validates hydroxylation results from both studies and examines CL-20 transformations via photo-induced free radical reactions. This article discusses CL-20 competing modes of degradation revealed through: computational calculation; UV/VIS and SF spectroscopy following alkaline hydrolysis; and photochemical irradiation to degrade CL-20 and its byproducts at their respective wavelengths of maximum absorption.     

紫外光谱法测定乙酸乙烯酯中的对苯二酚

采用紫外光谱法测定乙酸乙烯酯中对苯二酚含量时,乙酸乙烯酯中的有机杂质会对测试结果产生影响.其中乙醛、丙酮对测试结果的影响程度基本呈线性递增关系,而醋酸甲酯、醋酸乙酯对测试结果不会产生影响.     

An on‐line sample pretreatment technique for the HPLC analysis of plant samples

A continuous‐flow, on‐line sample pretreatment technique using a silica gel microsyringe extractor has been developed. All steps including extraction, separation, clean‐up, and concentration occur in the microsyringe. The overall sample pretreatment process takes <10 min per sample. Different polarity chemicals in the plant sample are successively extracted and separated, and analyzed in parallel using HPLC–UV and HPLC–UV–MS/MS. Polycyclic aromatic hydrocarbons, alkylphenols, and plant hormones were determined as model compounds for nonpolar, intermediate polarity, and polar fractions, respectively. All the parameters that influence the extraction and separation efficiency of the microsyringe extractor have been optimized and evaluated. Under the optimized conditions, recoveries of target compounds ranged from 78.4 to 101.9%, the RSD was <12.8% and the square of the correlation coefficient was >0.99. Complex plant samples of Sambucus Mandshurica Kitag have been tested using this method. Fluorene, phenanthrene, pyrene, and plant hormones were detected in all the samples, and concentrations ranged from 24.2–34.9, 43.8–67.1, 25.9–29.2, and 14.5～110.8 ng/g, respectively.