盐水振荡研究的新发现

在对化学振荡的研究中,无论是溶液均相氧化还原形成的振荡反应,还是界面扩散受阻形成的界面振荡,都普遍采取各种电极法来监测。前文[1,2]研究了各种不同电极监测液膜振荡的变化,本文将讨论不同的电极方法在监测盐水振荡现象过程中的新发现。1970年,地球物理学家Martin[3]发现把     

电化学合成铜配合物的研究

采用金属铜为"牺牲"阳极,首次在无隔膜电解槽中,电化学溶解金属铜一步制备了纳米CuO前体Cu(OEt)2, Cu(OBu)2, Cu(acac)2, Cu(OEt)(acac), Cu(OBu)(acac) (acac为乙酰丙酮基).产物通过红外光谱(FT-IR)、拉曼光谱(Raman spectrum)进行表征.同时讨论了影响电合成铜醇盐及其配合物的关键因素.实验表明,防止阳极钝化,温度控制在30～50 ℃,采用有机胺溴化物为导电盐, 电极电位控制在0.8～1.2 V之间,可以提高电合成效率.实验同时表明Cu(acac)2, Cu(OEt)(acac), Cu(OBu)(acac)可作为制备含铜纳米材料前驱体.     

Molecular Rectangle Formed by Head-to-tail Self-Assembly of 1-(Dipyrrin-2-yl)-1-(dipyrrin-3-yl)methane

Summary. 1-(Dipyrrin-2-yl)-1-(dipyrrin-3-yl)methane, the N-confused analog of biladiene-ac, is prepared by condensation of 2,3-dipyrromethane with two molecules of 2-formylpyrrole in dichloromethane in the presence of hydrogen bromide. Self-assembly of the ligand with Zn(II) in dichloromethane and methanol offers a dinuclear dimeric complex with a ligand:metal ratio of 2:2. X-Ray crystal structure analysis reveals two ligands bound through a head-to-tail pattern to two zinc centers to form a severely distorted helical conformation, which has the shape of a rectangle.     

Study of the concentration and separation of cadmium with microcrystalline phenolphthalein modified by crystal violet

A new method for cadmium separation and concentration with microcrystalline phenolphthalein modified by crystal violet (CV) was developed in the paper. In the presence of potassium iodide (KI) and CV, cadmium are quantitatively absorbed on microcrystalline phenolphthalein in the pH range 1.0-6.0 as the forms of water-insoluble ion-associated complexes (CdI₃⁻)·(CV⁺) and (CdI₄²⁻)·(CV⁺)₂. Effect of different parameters such as phenolphthalein amount, stirring time, the concentration of CV and KI, various salts and metal ions was studied in detail. During the present study, a significant enhancement of the extraction of cadmium was observed. Cd(II) can be completely separated from Zn(II), Fe(II), Co(II), Ni(II), Mn(II), Cr(III) and Al(III) in this microcrystalline system and well concentrated without the interference of these metal ions at high level. The possible reactive mechanism of cadmium concentration has been discussed. Analytical results obtained by this new method were very gratifying.     

A specific colorimetric cysteine sensing probe based on dipyrromethane-TCNQ assembly

A new charge-transfer complex, consisting of dihydroxymethyl di-(2-pyrrolyl)methane and tetracyanoquinodimethane (TCNQ), has been designed to high selectively distinguish cysteine from other amino acids in water/organic solvent mixtures through the visual color change from blue to nearly colorless. The excellent system properties make the supramolecular assembly a highly selective colorimetric probe for monitoring cysteine.     

NMR Study of the Stoichiometry, Stability, and Ligand Interchange of Silver Ion-Hexathia-18-crown-6 Complex in Binary Dimethyl Sulfoxide Solvent Mixtures at 300 K

Proton NMR was used to study the complexation reaction between silver ion and hexathia-18-crown-6 in a number of binary mixed solvents of dimethyl sulfoxide with acetonitrile and methanol. Formation constants for the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. The influence of solvent composition on the stability of the resulting complex is discussed. The exchange kinetics of Ag⁺-hexathia-18-crown-6 in 70-30 wt.% dimethyl sulfoxide-acetonitrile and 75-25 wt.% dimethyl sulfoxide-methanol were studied by proton NMR line-shape analysis. In both solvent mixtures, the exchange of thiacrown ether between the free and complexed sites was found to proceed via a dissociative pathway. The exchange rates and the activation parameters E _a, H , S, and G for the ligand exchange were determined and the influence of solvent properties on these parameters discussed.     

金属蛋白研究中几个值得注意的动向

本文叙述了金属蛋白和金属酶研究中近年来几个值得注意的发展动向，即与金属离子相关的疾病（特别是神经退行性疾病）、金属离子在蛋白质的折叠、聚集和装配中的作用，金属伴侣分子、金属蛋白的设计和构建、金属蛋白与DNA相互作用。     

Mo、W金属氧化物对CH4/CO2重整Ni基催化剂性能的影响

用XRD、XPS、元素分析、TEM和活性评价等方法研究过渡金属氧化物MoO3和WO3对SiO2负载的Ni基催化剂物理化学性质和CH4/CO2重整制合成气催化性能的影响.结果表明,在负载型的镍催化剂中,MoO3和WO3的添加一方面提高了Ni的核外电子密度,减弱了对CH4深度裂解积炭;另一方面使催化剂表面镍的相对浓度降低,结构上起到了隔离、分散金属颗粒的作用,氧的相对浓度升高,有效提高了催化剂的抗烧结和抗积炭能力,显示出较好的催化稳定性.     

Optical sensors for determination of heavy metal ions

A review is given on optical means for single shot testing (probing) as well as continuous monitoring (sensing) of heavy metal ions (HMs). Following an introduction into indicator based approaches, we discuss the types of indicator dyes and polymeric supports used, as well as existing sensing schemes for HMs. The wealth of information is compiled in the form of tables and critically reviewed. Notwithstanding the tremendous work performed so far, it is obvious that still severe limitations do exist in terms of selectivity, limits of detection, dynamic ranges, applicability to specific problems, and reversibility. On the other hand, such sensors have found — and will find — their application whenever rapid and cost-effective testing is required, where personnel is scarce or unskilled, and in field tests. Despite their limitations, the number of such sensors (and of irreversible probes) for HMs is likely to increase in future.     

新型大位阻取代茂钛,锆化合物的合成及其谱学性质

通过１－环庚烯基锂与６，６－二烷基富烯发生环外双键的加成反应形成的大取代茂锂试剂与ＭＣｌ４（Ｍ＝Ｔｉ，Ｚｒ）反应，合成了１２个含或不含手性碳的大位阻取代茂金属有机化合物，并研究了它们的１ＨＮＭＲ，ＥＩＭＳ和ＩＲ．