Structure and Magnetic Properties of a Novel Two‐Dimensional Complex from 1, 3, 5‐Benzenetricarboxylate and Neodymium(III) — {[Nd(1, 3, 5‐benzenetricarboxylate)(H2O)4] · H2O}n

A unique neodymium(III) complex, {[Nd(BTC)(H₂O)₄] · H₂O}_n (BTC = 1, 3, 5‐benzenetricarboxylate), was obtained from the reaction between Nd(ClO₄)₃ · xH₂O and Na₃BTC. Coordination bonds, hydrogen bonds, and π‐π stacking form a supramolecular structure with a novel, two‐dimensional framework. The temperature‐dependent magnetic susceptibilities were analyzed by the Curie‐Weiss law; the following values were found C = 1.32, θ = —18.3 K, respectively.     

Physico-chemical characterization of nanofiltration membranes.

This study presents a methodology for an in-depth characterization of six representative commercial nanofiltration membranes. Laboratory-made polyethersulfone membranes are included for reference. Besides the physical characterization [molecular weight cut-off (MWCO), surface charge, roughness and hydrophobicity], the membranes are also studied for their chemical composition [attenuated total reflectance Fourier spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS)] and porosity [positron annihilation spectroscopy (PAS)]. The chemical characterization indicates that all membranes are composed of at least two different layers. The presence of an additional third layer is proved and studied for membranes with a polyamide top layer. PAS experiments, in combination with FIB (focused ion beam) images, show that these membranes also have a thinner and a less porous skin layer (upper part of the top layer). In the skin layer, two different pore sizes are observed for all commercial membranes: a pore size of 1.25-1.55 angstroms as well as a pore size of 3.20-3.95 angstroms (both depending on the membrane type). Thus, the pore size distribution in nanofiltration membranes is bimodal, in contrast to the generally accepted log-normal distribution. Although the pore sizes are rather similar for all commercial membranes, their pore volume fraction and hence their porosity differ significantly.     

Reactions of the ionized enol tautomer of acetanilide: elimination of HNCO via a novel rearrangement

The reactions of ionised acetanilide, C(6)H(5)NH(=O)CH(3)(.+), and its enol, C(6)H(5)NH(OH)=CH(2)(.+), have been studied by a combination of tandem mass spectrometric and computational methods. These two isomeric radical cations have distinct chemistries at low internal energies. The keto tautomer eliminates exclusively CH(2)=C=O to give ionised aniline. In contrast, the enol tautomer loses H-N=C=O, via an unusual skeletal rearrangement, to form predominantly ionised methylene cyclohexadiene. Hydrogen atom loss also occurs from the enol tautomer, with the formation of protonated oxindole. The mechanisms for H-N=C=O and hydrogen atom loss both involve cyclisation; the former proceeds via a spiro transition state formed by attachment of the methylene group to the ipso position, whereas the latter entails the formation of a five-membered ring by attachment to the ortho position. The behaviour of labelled analogues reveals that these two processes have different site selectivities. Hydrogen atom loss involves a reverse critical energy and is subject to an isotope effect. Surprisingly, attempts to promote the enolisation of ionised acetanilide by proton-transport catalysis were unsuccessful. In a reversal of the usual situation for ionised carbonyl compounds, ionised acetanilide is actually more stable than its enol tautomer. The enol tautomer was resistant to proton-transport catalysed ketonisation to ionised acetanilide, possibly because the favoured geometry of the encounter complex with the base molecule is inappropriate for facilitating tautomerisation.     

负载稀土型酸活化膨润土的酯化催化活性

负载稀土型酸活化膨润土的酯化催化活性李永绣，冯天泽，胡平贵，何小彬，辜子英，廖荣辉（南昌大学化学系南昌３３００４７）关键词稀土，膨润土，催化酯化可用稀土、膨润土单独作酯化催化剂，但活性不高［１～３］。本文将稀土用离子交换的方法负载到酸活化膨润土中，寻...     

Chemistry of O-Benzoquinones and Masked O-Benzoquinones I. Diels-Alder Reactions of O-Benzoquinones with Dimethyl Acetylenedicarboxylate and Phenylacetylene

Diels-Alder reactions of six o-benzoquinones with dimethyl acetylenedicarboxylate has been examined. The yields of adducts vary with the natures of the o-benzoquinones, 3,4-Di-n-propyl-(1c), 3,6-di-n-propyl (1d). 3. 4-diallyl-(1e) and 3, 6-diallyl-o-benzoquinone (1f) are found to give bicyclic a-diketones exclusively without the formation of 1,4-dioxine derivatives, the yields ranging from 20 to 70%. In the case of 4, 5-dimethoxy-o-benzoquinone, dimethyl 4, 5-dimethoxyphthalate is produced in 42% yield, presumably derived from the decomposition of the corresponding initially formed α-diketone. 3, 6-Di-n-propyl-4, 5-dimethoxy-o-benzoquinone deteriorates without addition to dimethyl acetylenedicarboxylate upon heating. The additions of o-benzoquinones 1c , 1d and 1f to phenylacetylene are also studied. The yields of adducts, α-diketones, range from 23% to 82%.     

Alkanethiolate self-assembled monolayers as functional spacers to resist protein adsorption upon Au-coated nerve microelectrode

Alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths were adsorbed upon Au-coated nerve microelectrodes and employed as protein-resistant spacers. The microelectrode spiraled as a cuff type can be used for restoring motor function via electrical stimulation on the peripheral nerve system; however, an increase of electrode impedance might occur during implantation. In this work, a thin-film SAMs treatment upon Au/polyimide (PI) surface of the microelectrode provided a hydrophobic characteristic, which retarded protein adsorption at the initial stage and subsequent pileup (or thickening) process. The protein-resistant effect exhibited comparable SAMs of different chain lengths adsorbed upon Au/PI surfaces. The increase of electrode impedance as a function of protein deposition time was mainly correlated with the addition of reactance that was associated with the pileup thickness of the deposited protein. Particularly, the SAMs-modified surface was capable to detach a significant portion of the accumulated protein from the protein-deposited SAMs/Au/PI, whereas the protein-deposited layers exhibited firm adhesion upon Au/PI surface. It is therefore very promising to apply thin-film SAMs adsorbed upon Au-coated surface for bioinvasive devices that have the need of functional electrical stimulations or sensing nerve signals during chronic implantation.     

From D-glucose to biologically potent L-hexose derivatives: synthesis of alpha-L-iduronidase fluorogenic detector and the disaccharide moieties of bleomycin A2 and heparan sulfate

A novel and convenient route for the synthesis of biologically potent and rare L-hexose derivatives from D-glucose is described. Conversion of diacetone-alpha-D-glucose (14) into 1,2:3,5-di-O-isopropylidene-beta-L-idofuranose (19) was efficiently carried out in two steps. Orthogonal isopropylidene rearrangement of compound 19 led to 1,2:5,6-di-O-isopropylidene-beta-L-idofuranose (27), which underwent regioselective epimerization at the C3 position to give the L-talo- and 3-functionalized L-idofuranosyl derivatives. Hydrolysis of compound 19 under acidic conditions furnished 1,6-anhydro-beta-L-idopyranose (35) in excellent yield, which was successfully transformed into the corresponding L-allo, L-altro, L-gulo, and L-ido derivatives via regioselective benzylation, benzoylation, triflation and nucleophilic substitution as the key steps. Applications of these 1,6-anhydro-beta-L-hexopyranoses as valuable building blocks to the syntheses of 4-methylcoumarin-7-yl-alpha-L-iduronic acid and the disaccharide moieties of bleomycin A(2) as well as heparan sulfate are highlighted.     

Titrimetric determination of thiocyanate and thiosulphate ions by oxidation with iodine in alkaline solution

Thiocyanate (2.7-90 mug) and thiosulphate (4.5-90 mug) ions are oxidized by iodine in alkaline media to sulphate ions. After acidification, the excess of iodine is extracted into chloroform, and the iodide ions formed in the redox reaction subjected to an amplification reaction. Either a titrimetric or a spectrophotometric finish may be used. Each thiocyanate and thiosulphate ion results in the ultimate production of 19 and 24 iodine molecules, respectively.     

Analysis of CL-20 in environmental matrices: water and soil

Analytical techniques for the detection of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo(5.5.0.05,9.03,11)dodecane (CL-20) in water and soil are developed by adapting methods traditionally used for the analysis of nitroaromatics. CL-20 (a new explosives compound) is thermally labile, exhibits high polarity, and has low solubility in water. These constraints make the use of specialized sample handling, preparation, extraction, and analysis necessary. The ability to determine the concentrations of this new explosive compound in environmental matrices is helpful in understanding the environmental fate and effects of CL-20; understanding the physical, chemical, and biological fate of CL-20; and can be used in developing remediation technologies and determining their efficiency. The toxicity and mobility of new explosives in soil and groundwater are also of interest, and analytical techniques for quantitating CL-20 and its degradation products in soil and natural waters make these investigations possible.