EDTA对新型多胺螯合树脂选择性吸附Cu(Ⅱ)的影响机制

结合溶液体系Cu-EDTA形态分析,研究了广泛pH值下EDTA对多胺螯合树脂(PAMD)选择性吸附Cu(Ⅱ)的影响规律。酸性条件(2.0pH7.0)下,随pH值升高,Cu(Ⅱ)的吸附量先增大后减小,显示出受游离EDTA离子形态变化的明显影响,这与阴离子络合态铜(CuHEDTA-和CuEDTA~(2-))与质子化氨基的静电作用相关。碱性条件(7.0pH12.0)下,随pH值升高,Cu(Ⅱ)的吸附量逐步增大并趋于稳定,这主要是因为作用机制由去质子化氨基与EDTA络合态铜形成三元络合物(7.0pH9.5)转变为去质子化氨基直接置换EDTA络合态铜中EDTA配体的方式(9.5pH12.0),进而增加了PAMD树脂对Cu(Ⅱ)的选择性吸附性能。另外,无机盐离子促进了PAMD树脂对EDTA络合态铜的配体置换作用,提高了Cu(Ⅱ)的选择性吸附性能。在盐、碱共存体系中Cu(Ⅱ)对EDTA的选择性系数高达73.1,可作为常见有机络合重金属离子选择性去除的新方法。     

以三(2-氨基乙基)胺为核的PAMAM与Zn2+的络合作用研究

以三(2-氨基乙基)胺为核,通过发散法合成了不同代数的树状聚酰胺胺(PAMAM),并利用FT-IR、1H NMR等技术对合成的产物进行表征,结果表明所合成产物的分子结构与理论结构相符。合成的PAM-AM具有大量的伯胺、叔胺和酰胺,可以作为Zn2+的络合剂。采用荧光分光光度法研究了PAMAM与Zn2+的络合作用,探讨了PAMAM的代数、Zn2+与PAMAM的摩尔比、溶液pH值、反应时间和温度对络合的影响。结果表明PAMAM的代数越高,所络合的Zn2+数目越多,且与理论值相符;随着Zn2+与PAMAM摩尔比的增加,络合形式发生变化;溶液pH值对络合体系有显著影响,强酸性条件下,PAMAM的伯胺和叔胺被质子化,H+取代Zn2+,Zn2+从络合体系中释放出来,这为PAMAM的循环利用提供了理论依据;另外,反应时间和温度对PAMAM与Zn2+的络合也有一定影响,延长反应时间和升高反应温度均使络合程度增加。     

金纳米粒子在氨基表面上的组装-pH值的影响

用原子力显微镜（AFM）和表面增强喇曼光谱（SERS）研究了pH值对金纳米粒子在Au／巯基苯胺自组装膜表面上组装效果的影响．AFM结果表明，金纳米粒子在表面上的覆盖度随pH值表现出规律性的变化，巯基苯胺自组装膜的SERS强度随pH值的变化也有类似的趋势．在磁性环境下，氨基未质子化，金粒子难以组装上，而在酸性条件下，氨基质子化带正电，金粒子与基底容易结合．我们认为金纳米粒子和氨基之间的作用属于静电力，pH值同时影响膜表面氨基的质子化程度和金纳米粒子表面的带电量．     

功能化烯胺的合成(Ⅰ):混合溶剂中硫脲催化α,β-邻位氨基溴转变成α,β-脱氢氨

建立了一种简单有效的合成功能化烯胺的新方法.在有机小分子硫脲的催化下(50 mol%),在混合溶剂中[CH2Cl2/DMF=1∶1(V/V)],室温下各种α,β-邻位氨基溴的酮和α,β-邻位氨基溴的酯均能几乎定量的转变成相应的α,β-脱氢氨类化合物(收率90%～99%).硫脲催化邻位氨基溴转变成α,β-脱氢氨类化合物的新方法,具有反应条件温和、操作简便、收率高、催化剂廉价易得等特点.全文共考察了32种不同结构α,β-邻位氨基溴的酮和α,β-邻位氨基溴的酯反应情况,证明该方法具有广泛的适应性.实验中发现,α,β-邻位氨基溴的酮和α,β-邻位氨基溴的酯在发生消除反应时,要经过一个形成氮丙啶的中间过程,再由氮丙啶的开环反应形成最终产物(α,β-脱氢氨类化合物).因此不论反应底物为α-氨基-β-溴结构还是α-溴-β-氨基结构,通过分子内的亲核取代反应所形成的氮丙啶结构单元具有相似的立体结构,而氮丙啶的开环具有区域专一性,因此所得到的最终产物也具有区域专一性(烯键上的氨基均处在羰基的α-位).所提出的硫脲催化邻位氨基溴转变成α,β-脱氢氨的可能机理,很好地解释了该反应的区域专一性.所有的产物结构均经过了1H NMR,13C NMR及高分辨质谱的确证.     

稀土-漂蓝6B的络合吸附波研究Ⅱ

在pH6.0的0.1mol/L NaAc-HAc底液中,稀土离子可与ECAB生成1:2的络合物。取样交流极谱峰高下降格数与稀土浓度在1×10~(-6)—2×10~(-5)mol/L范围内成线性关系。由于与稀土离子配位的ECAB的络合基团恰好就是氧化还原基团,故在极谱上没有新峰出现,只有ECAB峰电流的下降。电极还原反应的最终产物是ECAB的负碳离子,它快速质子化后形成无色的具四面体结构的分子。     

Cd(ATZ)4( H2O)2] ( PA)2· 2H2O的合成、晶体结构和热分解机理研究

合成了以 5 -氨基四唑为配体的镉配合物 [Cd(ATZ) 4(H2 O) 2 ](PA) 2 ·2H2 O ,并对其进行了晶体结构测定 .测定结果表明 ,该配合物分子具有中心对称性 ,每个Cd2 +分别与 2个水分子中的氧原子和 4个 5 -氨基四唑 (ATZ)分子中的 4-位氮原子配位 ,形成六配位畸变八面体结构 ;在配合物分子间存在大量氢键 ,增加了整个晶体结构的稳定性 .通过DSC和TG -DTG分析 ,提出了标题化合物的热分解机理     

金属硫蛋白MT-2a与Cd(Ⅱ)和Cu(Ⅰ)络合的电喷雾质谱表征

采用电喷雾质谱法(ESI-MS)研究金属硫蛋白(MT,存在α和β两种结构域)-2a与金属离子Cd和Cu的络合作用.MT-2a由反相色谱分离纯化制得,并以电喷雾质谱鉴别.通过ESI-MS考察MT-2a与不同量的Cd和Cu的络合,结果表明,Cd能够优先与MT的α结构域络合,形成M2+4S11结构,并且该络合过程存在着明显的协同效应;Cd与MT的β结构域的络合形式为M2+4S9,其呈现出明显的随机松散络合特性;Cu优先与MT的β结构域络合,其络合形式由Cu4逐渐过渡到更高结合态;在Cu含量较高的条件下,Cu与MT呈现出多种络合方式.     

Cu(Ⅱ)-N,N-二(2-00羧基苯基)-2,6-吡啶二甲酰胺配合物的光谱性质及结构

本文通过紫外-可见吸收光谱和荧光光谱,在乙醇溶液中(pH=7～8)研究了Cu(Ⅱ)离子与N,N-二(2-羧基苯基)-2,6-吡啶二甲酰胺(BCPD)的相互作用.结果表明溶液中二者以1∶1的化学计量比形成配合物,表观结合常数为(4.59+0.05)× 106 mo1-1·L.由Cu(Ⅱ)离子与BCPD在甲醇中反应合成了1∶1型铜配合物[Cu(Ⅱ)(BCPD)]2-· 2[(C2H5)3NH]+·CH3OH,用元素分析、单晶X射线衍射等手段对配合物的结构进行了表征.晶体属于单斜晶系,P21/c空间群α=1.290 90(12) nm,b=1.855 19(19) nm,c=1.752 31(16) nm,β=122.920(2)°.BCPD以吡啶氮、两个去质子化的酰胺氮原子和2个羧基与Cu(Ⅱ)配位,形成五配位畸变四方锥构型.     

金属硫蛋白加质子常数及与Cd(II)络合常数测定

用pH计和Cd离子选择电极测定了金属硫蛋白的加质子常数及其与Cd(Ⅱ)的络合常数, 用改进的简化络合模型处理实验结果, 得到了去金属硫蛋白(apo MT)中6类不同的加质子基团的数目及其加质子常数。对Cd(Ⅱ)滴定数据的计算表明, MT中两个结构域——α和β对Cd(Ⅱ)的络合常数相差约1000倍。从热力学定量描述了MT中两个结构域结合金属离子选择优先顺序。     

金属硫蛋白加质子常数及与C_d(Ⅱ)络合常数测定

用pH计和Cd离子选择电极测定了金属硫蛋白的加质子常数及其与Cd(Ⅱ)的络合常数,用改进的简化络合模型处理实验结果,得到了去金属硫蛋白(apo MT)中6类不同的加质子基团的数目及其加质子常数。对Cd(Ⅱ)滴定数据的计算表明,MT中两个结构域——α和β对Cd(Ⅱ)的络合常数相差约1000倍。从热力学定量描述了MT中两个结构域结合金属离子选择优先顺序。     

Complexes of cadmium ion with guanine bases detected by electrospray ionization mass spectrometry

The complexations of cadmium ion with guanine bases were detected by electrospray ionization mass spectrometry (ESI-MS). In order to explore the toxicity of cadmium, such as oxidative stress to DNA and carcinogenesis, it is very important to determine the interactions between the cadmium ion and nucleotide. The analysis of mixed cadmium ion-guanosine aqueous solution (molar ratio 1 : 9) using ESI-MS (cone voltage 20 V) showed the presence of various cadmium complex ions, such as [n (guanosine) + Cd](2+) (n = 3-8), [2guanine + Cd](2+), [guanosine + guanine + Cd](2+) and [guanosine + 2guanine + Cd](2+). The observed [2guanine + Cd](2+), [guanosine + guanine + Cd](2+) and [guanosine + guanine + Cd](2+) ions are formed through the dissociation of the N-glycoside bond at the interface of ESI-MS. For deoxyguanosine and ethylguanine, similar cadmium complexes were observed. However, the complexes between the cadmium ion and 8-hydroxydeoxyguanosine were not detected. Furthermore, when a higher molar ratio (Cd : guanosine) or cone voltage were used, more of the monovalent ion peaks, such as [Cd(guanine - H)(2) + H](+) and [Cd(guanosine - H)(2) + H](+), were observed and a decrease in the abundance of the divalent ions, such as [n(guanosine)+Cd](2+), occurred.     

A Copper（Ⅱ）-cadmium（Ⅱ） Heterometallic Hexanuclear Complex：[Cd_4Cu_2（pdc）_4（H_2O）_（14）]（H_3pdc=3,5-Pyrazoledicarboxylic Acid）

The title complex 1,[Cd 4 Cu 2 (pdc) 4 (H 2 O) 14 ] (H 3 pdc=3,5-pyrazoledicarboxylic acid),has been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex 1 crystallizes in triclinic,space group P1 with a=0.67235(10),b=1.27935(18),c=1.28569(17) nm,α=112.633(2),β=102.971(3),γ=97.089(2)o,V=0.9673(2) nm 3,C 20 H 32 Cd 4 Cu 2 N 8 O 30,M r=1441.22,D c=2.474 g/cm 3,μ(MoKα)=3.356 mm 1,F(000)=698,S=1.003,Z=1,the final R=0.0471 and wR=0.0748 for I > 2σ(Ⅰ).In 1,two deprotonated 3,5-pyrazoledicarboxylic acids (pdc 3),one copper(Ⅱ) ion and one cadmium(Ⅱ) ion firstly form a pyrazole-bridged Cu II Cd II dinuclear unit,two of which related by an inversion center are connected by another two cadmium(Ⅱ) ions through chelating carboxylate groups to construct the copper(Ⅱ)-cadmium(Ⅱ) heterometallic hexanuclear complexes.Plenty of hydrogen bond interactions existing in the system further lead to a three-dimensional (3D) supramolecular framework.     

Assessing effects of pH,metal ion and natural organic matter on identification and determination of reduced glutathione by cathodic stripping voltammetry

The effects of pH, metal ions (i.e. Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺) and natural organic matter (i.e. Suwannee River natural organic matter standard [SRNOM]) on determination of thiol (i.e. reduced glutathione [GSH]) by cathodic stripping voltammetry were evaluated. pH was the most critical parameter to influence GSH voltammogram (i.e. peak shape, position and height). In presence of Cu and Cd, secondary peaks were found at [metal]/GSH > 1 due to formation of GSH complexes at pH = 8.0 (Cu and Cd) and 2.5 (Cu only). On the other hand, Pb showed negligible influence on GSH voltammogram at pH 8.0 and 2.5 within [Pb]/[GSH] = 0.01–2.0. Zn significantly reduced GSH peak height at pH 2.5 at [Zn]/[GSH] = 0.01–2.0. SRNOM peak significantly overlapped with GSH peak at pH 8.0 and [SRNOM] > 1 mg L^?1 but was clearly separated from the GSH peak at pH 2.5. However, at pH 2.5, the presence of metal ions and/or SRNOM significantly underestimated GSH concentration (recovery = 21–69%), likely due to metal complexation with GSH and/or SRNOM adsorption onto Hg electrode. The effects of metal ions were minimised by the addition of EDTA. The interference induced by SRNOM adsorption was reduced as the [SRNOM] was reduced to 1 mg L^?1 and the recovery was improved to 98%.     

Electrospray ionization studies of transition-metal complexes of 2-acetylbenzimidazolethiosemicarbazone using collision-induced dissociation and ion-molecule reactions

The complexes of transition-metal ions (M2+, where M = Fe, Co, Ni, Cu, Zn, Cd, and Hg) with 2-acetylbenzimidazolethiosemicarbazone (L) are studied under electrospray ionization (ESI) conditions. The ESI mass spectra of Fe and Co complexes showed the complex ions corresponding to [M+2L-2H]+, and those of Ni and Zn complexes showed [M+2L-H]+ ions, wherein the metal/ligand ratio is 1:2 and the oxidation state of the central metal ion is +3 in the case of Fe and Co and +2 in the case of Ni and Zn. The Cd and Cu complexes showed preferentially 1:1 complex ions, i.e., [M+L-H]+ or [M+L+Cl]+, whereas Hg formed both 1:1 and 1:2 complex ions. During formation of the above complex ions one or two ligands are deprotonated after keto-enol tautomerism, depending on the nature and oxidation state of central metal ion. The structures and coordination numbers of the metal ions in the complex ions were studied by their collision-induced dissociation spectra and ion-molecule reactions with acetonitrile or propylamine in the collision cell. Based on these results it is concluded that Fe, Co, Ni and Zn form stable octahedral complexes, whereas tetrahedral or square planar complexes are formed preferentially for other metals. In addition, the Cu complex showed a [2L+2Cu-3H]+ ion with a Cu-Cu bond.     

Synthesis, characterization, and crystal structures of three new divalent metal carboxylate-sulfonates with a layered and one-dimensional structure

Hydrothermal reactions of 5-sulfoisophthalic acid (HO(3)SC(6)H(3)-1,3-(CO(2)H)(2), H(3)L) with M(II) carbonate (or oxide) and 4,4'-bipyridine (4,4'-bipy) (or 2,2'-bipyridine, 2,2'-bipy) resulted in three new metal carboxylate-sulfonate hybrids, namely, [CdL(H-4,4'-bipy)] (1) and [Cd(3)L(2)(2,2-bipy)(4)(H(2)O)(2)].2H(2)O (2) with layered structures and [ZnL(H-4,4'-bipy)(H(2)O)].2H(2)O (3), whose structure features a one-dimensional double chain. The cadmium(II) ion in complex 1 is seven-coordinated by five carboxylate oxygen atoms and one sulfonate oxygen atom from four ligands and a unidentate 4,4'-bipyridine. The interconnection of the cadmium(II) ions through bridging carboxylate-sulfonate ligands resulted in the formation of a <002> double layer with the bipyridyl rings orientated toward the interlayer space. Complex 2 has a different layered structure. Cd(1) is seven-coordinated by two bidentate chelating carboxylate groups from two ligands, a bidentate chelating 2,2'-bipy and an aqua ligand, and Cd(2) is octahedrally coordinated by two bidentate chelating 2,2'-bipy's, a sulfonate oxygen, and an aqua ligand. The coordination geometry around Cd(3) is similar to that of Cd(1) with the aqua ligand being replaced by an oxygen atom from the sulfonate group. The carboxylate-sulfonate ligand acts as pentadentate ligand, bridging with three cadmium(II) ions. The bridging of cadmium(II) ions through the carboxylate-sulfonate ligands resulted in the formation of <006> and <003> layers; the 2,2'-bipy molecules and [Cd(2)(2,2'-bipy)(2)(H(2)O)] cations are orientated to the interlayer space. Complex 3 features a 1D metal carboxylate-sulfonate double chain along the diagonal of the a- and b-axes. The zinc(II) ion is octahedrally coordinated by four carboxylate O atoms from three ligands, a unidentate 4,4'-bipy, and an aqua ligand. Each pair of zinc(II) ions is bridged by two carboxylate groups from two ligands to form a dimer, and such dimeric units are interconnected by bridging ligands to form a double chain. The sulfonate group of the carboxylate sulfonate ligand remains noncoordinated and forms a number of hydrogen bonds with aqua ligands as well as lattice water molecules.     

Surface reaction strategy for Raman probing trace cadmium ion

Prevalent contamination of water by cadmium ion (Cd²⁺) brings environmental risk, which threatening to human health including renal dysfunction, reduced lung capacity, and some cancers. It calls for rapid, sensitive and selective protocol to analyze Cd²⁺ on field. In this work, specific Raman probe is rationally designed by gold nanoparticles (AuNPs) functionalized with tripeptide glutathione (GSH) and Rhodamine 6G (R6G) (denoted as R6G/GSH/AuNPs), which is explored for indirectly determining trace Cd²⁺ in river water. Based on chelating interaction between GSH and Cd²⁺ to form tetrahedral Cd(SG)_4, which trends easy detachment from R6G/GSH/AuNPs. With increasing Cd²⁺ concentration, the Raman probe without protection of GSH happens due aggregation and Raman signal of R6G increases correspondingly. The R6G/GSH/AuNPs-based Raman detection of Cd²⁺ in river water shows rapidness, excellent sensitivity, selectivity and good repeatability. Limit of detection of 10 ppb with a widely linear range of 0.5–20 ppm could be achieved. It could be perspective that such Raman probe could be extended to be used for on-site monitoring trace Cd²⁺ in river water system.     

Cd(II), Zn(II), and Pd(II) complexes of an isoindoline pincer ligand: consequences of steric crowding

The sterically crowded isoindoline pincer ligand, 6'-MeLH, prepared by condensation of 4-methyl-2-aminopyridine and phthalonitrile, exhibits very different reaction chemistry with Cd2+, Zn2+, and Pd2+. Three different ligand coordination modes are reported, each dependent upon choice of metal ion. This isoindoline binds to Cd2+ as a charge-neutral, zwitterionic, bidentate ligand using imine and pyridine nitrogen atoms to form the eight-coordinate fluxional complex, Cd(6'-MeLH)2(NO3)2. In the presence of Zn2+, however, loss of a pyridine arm occurs through solvolysis and tetrahedrally coordinated complexes are formed with coordination of pyrrole and pyridine nitrogen atoms. Reaction with Pd2+ produces the highly distorted, square planar complex Pd(6'-MeL)Cl in which a deprotonated isoindoline anion coordinates as a tridentate pyridinium NNC pincer ligand.     

Development of highly sensitive cadmium iondashselective electrodes by titration method and its application to cadmium ion determination in industrial waste water

Characteristics of cadmium iondashselective electrode made cadmium sulphide (CdS)-silver sulphide (Ag(2)S) mixture were studied. CdS-Ag(2)S mixtures were obtained by gas/solid-phase reaction between silver-cadmium mixed powder and hydrogen sulphide gas (dry method) and by ionic reaction between cadmium-silver mixed ions and sulphide ion (wet method). As a result, it was found that the CdS-Ag(2)S mixture had to be made in the condition of excess existence of sulfur and had better regulate the excess sulfur quantity minimum, for the CdS-Ag(2)S pressed membrane gave a good Nernstian response against the cadmium ion concentration change. As the best way, CdS-Ag(2)S mixture was obtained by adding sulphide ion solution to 5 mol% cadmium ion and 95 mol% silver ion mixed solution while measuring silver sulphide (Ag(2)S) electrode potential as an indicator electrode. According to the reaction was stopped when the potential variation from the initial potential in the sulphide ion solution reached at 87-116 mV which the sulphide ion concentration became 10(-3) - 10(-4) of the initial concentration, the cadmium ion membrane pressed diameter of 8 mm and thickness of 2 mm showed a Nernstian response from 10(-8) to 10(-1) M of cadmium ion concentration. Furthermore, aiming to its application for industrial waste water, masking buffer for interfering metal ions such as lead ion (Pb(2+)) and copper ion (Cu(2+)), which were possibly coexisted and to adjust total ionic strength and pH of sample was developed. The present Cd(2+) iondashselective electrode was applied to the determination of Cd(2+) in the industrial waste water. The good regression line with correlation factor of 0.984 was obtained compared with the conventional atomic absorption spectroscopy.     

Cadmium(II) N-acetylcysteine complex formation in aqueous solution

The complex formation between Cd(II) ions and N-acetylcysteine (H(2)NAC) in aqueous solution was investigated using Cd K- and L(3)-edge X-ray absorption and (113)Cd NMR spectroscopic techniques. Two series of 0.1 M Cd(II) solutions with the total N-acetylcysteine concentration c(H2NAC) varied between 0.2-2 M were studied at pH 7.5 and 11.0, respectively. At pH = 11 a novel mononuclear [Cd(NAC)(4)](6-) complex with the average Cd-S distance 2.53(2) ? and the chemical shift δ((113)Cd) = 677 ppm was found to dominate at a concentration of the free deprotonated ligand [NAC(2-)] > 0.1 M, consistent with our previous reports on cadmium tetrathiolate complex formation with cysteine and glutathione. At pH 7.5 much higher ligand excess ([HNAC(-)] > 0.6 M) is required to make this tetrathiolate complex the major species. The (113)Cd NMR spectrum of a solution containing c(Cd(II)) = 0.5 M and c(H2NAC) = 1.0 M measured at 288 K showed three broad signals at 421, 583 and 642 ppm, which can be attributed to CdS(3)O(3), CdS(3)O and CdS(4) coordination sites, respectively, in oligomeric Cd(II)-NAC species with single thiolate bridges between the cadmium ions.     

Simultaneous femtomole determination of cysteine, reduced and oxidized glutathione, and phytochelatin in maize (Zea mays L.) kernels using high-performance liquid chromatography with electrochemical detection

Thiol compounds such as cysteine (Cys), reduced (GSH) and oxidized (GSSG) gluathione, and phytochelatins (PCs) play an important role in heavy metal detoxification in plants. These thiols are biological active compounds whose function is elimination of oxidative stress in plant cells. The aim of our work was to optimise sensitive and rapid method of high-performance liquid chromatography coupled with electrochemical detector (HPLC-ED) for determination of the abovementioned thiol compounds in maize (Zea mays L.) kernels. New approach for evaluation of HPLC-ED parameters is described. The most suitable isocratic mobile phase for the separation and detection of Cys, GSH, GSSG and PC2 consisted of methanol (MeOH) and trifluoroacetic acid (TFA). In addition, the influence of concentrations of TFA and ratio of MeOH:TFA on chromatographic separation and detection of the thiol compounds were studied. The mobile phase consisting from methanol and 0.05% (v/v) TFA in ratio 97:3 (%; v/v) was found the most suitable for the thiol compounds determination. Optimal flow rate of the mobile phase was 0.18 ml min(-1) and the column and detector temperature 35 degrees C. Hydrodynamic voltammograms of all studied compounds was obtained due to the selection of the most effective working electrodes potentials. Two most effective detection potentials were selected: 780 mV for the GSSG and PC2 and 680 mV for determination of Cys and GSH. The optimised HPLC-ED method was capable to determine femtomole levels of studied compounds. The detection limits (3 S/N) of the studied thiol compounds were for cysteine 112.8 fmol, GSH 63.5 fmol, GSSG 112.2 fmol and PC2 2.53 pmol per injection (5 microl). The optimised HPLC-ED method was applied to study of the influence of different cadmium concentrations (0, 10 and 100 microM Cd) on content of Cys, GSH, GSSG and PC2 in maize kernels. According to the increasing time of Cd treatment, content of GSH, GSSG and PC2 in maize kernels increased but content of Cys decreased. Decreasing Cys concentration probably relates with the increasing GSH and phytochelatins synthesis.