A comparative study of four 20-membered N_2S_4-crown ethers as ionophores for polymeric membrane silver selective electrodes

Four 20-membered N_2S_4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag^+-selective electrodes.Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag^+ ions.The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione(C) with 2-nitrophenyl octyl ether(o-NPOE) as solvent in a poly(vinyl chloride)(PVC) membrane matrix sho...

Synthesis and Selective Coloration of Monoaza Crown Ethers Bearing Picrylamino-type Side Arms for Alkali Metal Salts and Methylamine

N-pivot lariat ethers with picrylamino group as a chromophore (1, 2 and 3) have been prepared by reaction of N-(4-aminoaryl)monoaza crown ethers with picryl chrolide, and the selective coloration of 1, 2 and 3 for alkali metal salts and amines has been studied by UV-Vis spectra.

On an Expression of Extraction Constants without the Interfacial Equilibrium-Potential Differences for the Extraction of Univalent and Divalent Metal Picrates by Crown Ethers into 1,2-Dichloroethane and Nitrobenzene

An idea on interfacial equilibrium-potential differences () which are generated for the extraction of univalent metal picrate (MPic) and divalent ones (MPic2) by crown ethers (L) into high-polar diluents was improved. These potentials were clarified with some experimental extraction-data reported before on the M = Ag(I), Ca(II), Sr(II) and Ba(II) extraction with 18-crown-6 ether (18C6) and benzo-18C6 into 1,2-dichloroethane (DCE) and nitrobenzene (NB). Consequently, it was demonstrated that the? values from the extraction-experimentally obtained logKD,Pic ones are in agreement with or close to those calculated from charge balance equations in many cases, where the symbol, KD,Pic, denotes an individual distribution constant of Pic﹣ into the DCE or NB phase. Also, it was experimentally shown that extraction constants based on the overall extraction equilibria do not virtually contain the? terms in their functional expressions.

Spectral Properties of Extracted Complexes of MetalPicrates with Crown Ethers

The investigation on UV-visible spectra of species formed by extracting some metal picrates with benzo-15-crown-5(B15C5) and dibenzo-18-crown-6(DB18C6) verified that there are some interactions of picrate anion with K+, Na+ and rare earth ions in loaded organic phase. By the study of the charge transfer band and absorption spectra of picrate anion, it can be determined whether an ion pair has been formed and either a 1 : 1 contact ion pair or a 1 : 2 crown-separated ion pair involved in organic phase can be distinguished for an ion-pair extraction.

Synthesis and Crystal Structure of Potassium Crown Ether Tetrathiosquarate

Slow diffusion of diethylether into a concentrated solution of K2C454.H20 and two equivalents of 18-crown-6 in pyridine affords dark orange crystals of bis（potassium{18-crown-6}）（3-cyclobutene-1,2-dithione-3,4-dithiolate） [K（C12H2406）]2（CnS4）. The crystal structure determination （monoclinic, P 2t/n, a = 12.2095（8） A, b = 11.3263（8） A, c = 14.0552（7） A, fl = 101.032（3）~, Z = 2） shows the presence of C4S42 - ions with almost undistorted D4h symmetry having C-C bond lengths of 1.442（10） A and 1.478（8） A and C-S bond lengths of 1.651（8） A and 1.664（7） A. Since the K＋ ions are shielded in a half-spherical way by the crown ether ligands, the crystal structures is built of centrosymmetric molecular entities [（18-crown-6）K（C4S4）K（18-crown-6）]. The K＋ ions have eight of coordination number, C4S42- acts as a chelating and bridging ligand towards two K＋ with K-S distances of 3.434（2） A and 3.380（2） A.

Molecular Design of Crown Ethers. 19~1. Synthesis of Novel Disulfide and Diselenide-Bridged Bis (benzo-12-crown-4)s and their Ag^+ Selective Electrode Properties

Two novel heteroatom-bridged his (benzo-12-crown-4 ether)s, i.e. his [2-nitro-4,5 (1,4,7,10-tetraoxadecamethylene) disulfide 1 and diselenide 2, have been synthesized. X ray crystallographic structure was obtained for 1. Ion selective electrodes (ISE) for Ag+, containing 1 and 2 in PVC membrane as neutral carriers, were prepared, and their selectivity coefficients for Ag^+ (K_(Ag.M)^(pot)) were determined against other heavy metal ions, alkali and alkaline-earth metal ions. and ammonium ion. These ISEs showed excellent Ag^+ selectivities, log K_(Ag.M)^(pot) ≤ -3.8, against most of the interfering canons examined, except for Hg^+.

Mechanism of Li^(+)/Na^(+)separation by crown ether and butyrate acid root

Lithium is critical for economic growth since it is the primary component of batteries.Na^(+)is one of the main impurity ions in solution during the separation and enrichment of Li^(+).According to the size-matching effect between the cavities of crown ethers and Li+,crown ethers can selectively adsorb Li^(+).Herein,1,8-dihydroxyl-4,4,5,5-tetramethylbenzo-14-crown-4 was synthesized and used to extract lithium from a Li^(+)/Na^(+)mixed solution.Density functional theory(DFT)was used to explore the properties of complexes with M062X.The results show that the interactions between crown ethers and metal ions are due to electrostatic attraction.Hydroxyl functional groups can synergistically extract Li^(+)/Na^(+)from solutions with the oxygen atom in the crown ether ring.The stability of the complex is also enhanced by van der Waals interactions between the butyrate acid root and crown ether.1,8-dihydroxyl-4,4,5,5-tetramethylbenzo-14-crown-4 has a stronger interaction with lithium butyrate than with sodium butyrate for most conformations.The adsorption selectivity for Li+is proportional to the number of ether oxygen atoms that interact with Li^(+).The Li^(+)extraction efficiency increases from 3.93%to 20.93%in lithium hydroxide solution with the presence of butyrate acid root.When the butyrate acid root is added to the mixed Li^(+)/Na^(+)solution,the Li^(+)extraction efficiency increases from 6.54%to 31.20%,while the Li^(+)/Na^(+)separation coefficient decreases from33.25 to 1.32.

Crown ether-thiourea conjugates as ion transporters

Na^(+),Cl^(‒)and K^(+)are the most abundant electrolytes present in biological fluids that are essential to the regulation of pH homeostasis,membrane potential and cell volume in living organisms.Herein,we report synthetic crown ether-thiourea conjugates as a cation/anion symporter,which can transport both Na+and Cl^(–)across lipid bilayers with relatively high transport activity.Surprisingly,the ion transport activities were diminished when high concentrations of K+ions were present outside the vesicles.This unusual behavior resulted from the strong affinity of the transporters for K^(+)ions,which led to predominant partitioning of the transporters as the K^(+)complexes in the aqueous phase preventing the transporter incorporation into the membrane.Synthetic membrane transporters with Na^(+),Cl^(‒)and K^(+)transport capabilities may have potential biological and medicinal applications.

Pseudo-crown ether having AIE and PET effects from a TPE-CD conjugate for highly selective detection of mercury ions

A new tetraphenylethylene-cyclodextrin (TPE-CD) conjugate with a linkage composed of long triethylene glycol chain and triazole ring on the CD rim has been designed and synthesized. The TPE-CD conjugate exists in a stretched form in DMSO and enhances its fluorescence after addition of a small amount of water due to aggregation-induced emission (AIE) effect. However, in the presence of a large amount of water, the TPE unit will enter the cyclodextrin cavity to form a folded self-inclusion compound. In the self-inclusion compound, not only nitrogen-containing pseudo-crown ether is formed but also arouses photo-induced electron transfer (PET) process from nitrogen atoms of triazole ring to TPE unit and quenches the fluorescence although more aggregation occurs in more water. This is the first finding that TPE-macrocycle conjugate can form pseudo-crown ether and has both the AIE phenomenon and the PET effect. Interestingly, only mercury ion arouses the fluorescence recover of the self-inclusion compound by entering the pseudo-crown ether cavity and blocking the PET process by binding to the nitrogen atoms, while other tested metal ions almost have no effect on the fluorescence. Therefore, the TPE-CD conjugate can be used for the highly selective fluorescence "Turn-On" detection of Hg^(2+).

Molecular design of crown ethers .18.~1 Cationextractability and selectivities of selena-13- to 14-crown-4

Three selena-crown-4 derivatives have been prepared and their cation hinting abilities and selectivities with alkali and heavy metal ions have been evaluated by solvent extraction of aqueous metal picrates to show the highest Ag+ extractability for novel benzo-selena-14-crown-4 (2,3-benzo-7, 12-diselena-1, 4-dioxacyclotetradecane-2-ene) over any other crown ethers.

Investigation on the extraction of strontium ions from aqueous phase using crown ether-ionic liquid systems

The extraction of strontium ions using DCH18C6 as the extractant and various ionic liquids (ILs) as solvents has been investigated. The distribution ratio of Sr2+ can reach as high as 103 under certain conditions, much larger than that in DCH18C6/n-octanol system. The extraction capacity depends greatly on the structure of ionic liquids. In IIs-based extraction systems, the extraction efficiency of strontium ions is reduced by increasing the concentration of nitric acid and can also be influenced directly by the presence of Na+ and K+ in the aqueous phase. It is confirmed that the extraction proceeds mainly via a cation-exchange mechanism.

CdI₂Extraction with 18-Crown-6 Ether into Various Diluents: Classification of Extracted Cd(II) Complex Ions Based on the HSAB Principle

CdI2 in water was extracted with 18-crown-6 ether (L) into 10 diluents at 298 K. The following equilibrium constants were determined or evaluated: some extraction constants (Kex/mol-3·dm9 & Kex,ip/mol-2·dm6 for CdLI2, Kex±/mol-2·dm6 for CdLI+ with I-, & Kex2±/mol-1·dm3 for CdL2+ with 2I-), conditional distribution constants (KD,I for I-, KD,CdLI for CdLI+, & KD,CdL for CdL2+) between the two phases, and an ion-pair formation constant (K1,org/mol-1·dm3) for CdLI+ and that (K2,org/mol-1·dm3) for CdLI2 in the organic (org) phases. Using the K1,org and K2,org values, acidities of the complex ions, CdL2+ and CdLA+ (A- = I-, Br-, & Cl-), in the 11 diluents were classified by applying the HSAB rule. Especially, the CdLA+ ions were classified as the soft acids in 9 diluents. Also, molar volumes (Vj/cm3·mol-1) of j = CdLI2 and CdL2+ were determined with the regular-solution-theory plot of logKex,ip vs. logKD,L and its pseudo-plot of logKD,CdL, respectively. Here, KD,L denotes the distribution constant of L between the two phases. So, sizes among CdLA2 and CdL2+ were compared by using the Vj values. Additionally, some distribution equilibrium potentials (dep/V) between the water and org bulk phases were topically calculated from an equation of KD,I with KSD,I, where the symbol KSD,I shows a standard distribution constant of I- at dep = 0 V for a given diluent.

PRIMARY AMINE DRUG SELECTIVE ELECTRODES WITH SPECIAL CROWN ETHERS AS NEUTRAL CARRIERS*

Ionophores selectively sensitive to primary amines have been synthesized which display low potentiometric selectivity coefficients for K^+, Na^+ and NH_4^+ ions, secondary and tertiary amines as well as quaternary ammonium ions. These ionophores include macrocyclic polyethers with dinaphthyl subunits and azocrown ether with nitrogen donor atoms. The feasibility of these ionophores for preparing primary amine drug selective electrodes was investigated in detail. Practically usable PVC membrane electrodes sensitive to primary amine drugs, such as mexiletine, dopamine, metaraminol and tryptamine, and aliphatic primary amines have been prepared with these ionophores as neutral carriers. Direct potentiometric methods for assaying these drugs have been proposed by using the prepared electrodes. The proposed primary amine drug selective electrodes are remarkably superior to those based on ion-associates. Compared with the electrodes based on common ethers, the interference by K^+, Na^+ and NH_4^+ ions is substantially reduced. A digital simulation of the electrochemical process concerning the membrane transport was performed and some interesting conclusions have been drawn.

噻吩−冠醚基共价有机聚合物的制备及钯离子吸附性能研究

贵金属钯(Pd)由于独特的物理和化学性质,在催化、新能源、医疗、环境保护等领域中发挥着关键作用。钯矿的全球储量稀少且不可再生,因此钯的分离回收对实现可持续发展和资源的循环利用具有重要意义。通过席夫碱反应制备两种由三噻吩基团和冠醚基团作为骨架的共价有机聚合物(COPs):B-18C6-COP和B-24C8-COP,并通过静态吸附法评价两种材料对钯离子的吸附性能。研究结果显示,B-18C6-COP和B-24C8-COP在酸性条件下表现出较好的稳定性,在1 mol/L HNO_(3)浓度下,对钯离子的吸附容量分别为109.41、96.26 mg/g。同时,在与其他10种竞争离子共存时,两种材料均显示出对钯离子的高选择性。此项工作提供了一类对钯离子具有优异选择性的吸附剂,为钯离子的回收利用提供了新的思路。

冠醚功能化改性及其对金属离子分离研究进展

大环化合物作为超分子化学的重要结构化合物,在生物医药、环境科学及分子材料科学等领域应用广泛。冠醚作为第一代大环化合物,其内部独特的环状结构可与金属离子发生络合作用,从而实现对金属离子的选择性识别及分离,广泛应用于分离材料。综述了冠醚的种类及对金属离子选择性分离的机理,并就其合成离子印迹聚合物的表面印迹原理进行了总结。由于外界环境刺激能够影响冠醚的离子印迹状态,综述了冠醚在光和磁两个方面的离子印迹响应修饰及其在吸附材料和膜材料中对金属离子吸附性能的研究进展。结果表明,经冠醚功能化改性后,吸附材料和膜材料表面的选择性吸附位点增多,与金属离子络合的表面活性提高,从而有利于其对金属离子的选择性识别及分离。最后,对冠醚在今后的研究中存在的成本、性能测试及毒性富集等问题进行了讨论,并对冠醚以后的研究发展做出展望,为冠醚提取金属离子的应用提供研究方向。

低浓度轻稀土离子的选择性萃取分离

本文研究了采用1,7-二氮杂15冠5醚(2N15C5)从多离子共存的复杂硫酸盐体系中选择性萃取分离轻稀土离子的过程。结果表明:水相中的高浓度杂质离子主要通过诱导稀土硫酸钠盐沉淀的生成来影响复杂硫酸盐体系的稳定性,从而降低2N15C5对轻稀土离子的选择性萃取分配比。在水相pH<2.0、[SO_(4)^(2-)]/Σ[RE^(3+)]<10、相比R_(O/A)=2∶1、混相时间10 min的情况下,轻稀土离子组与重稀土离子组的单级萃取分离系数可达23.0023,经5级逆流萃取处理后,对应的累积萃取分离系数可达36.7016。该分组萃取分离法可从离子吸附型稀土矿原地浸出尾液中选择性萃取分离低浓度轻稀土离子,负载有机相经稀盐酸洗杂、乙二胺四乙酸溶液反萃处理后可得到轻稀土富集液,轻稀土离子的综合收率为83.98%。

LINEAR POLYSILOXANE WITH DIBENZO-18-CROWN-6 MOIETIES AS LIQUID MEMBRANE CARRIER

A modified method of preparing crown functionalized linear polysiloxane has been described. 4'-Allyldibenzo-18-crown-6 was subjected to hydrosilylation with methyldichlorosilane, followed by polycondensation with silanol-terminated polydimethylsiloxane to give the title crown functionalized linear polysiloxane. The transport properties of sodium, potassium, and ammonium salt through a bulk liquid membrane system using the new type of crown functionalized linear polysiloxane as a carrier were investigated. It is worthy to point out that the carrier can be used repeatedly at least six runs with no apparent change in the transport rate of potassium ion.

A New Chromogenic Diester-calix[4]crown Receptor for Ca^(2+)

A diester-calix[4]crown-4-ether bearing mono (azophenol) moiety shows a larger spectral change toward Ca2+ than other alkali and alkaline eafth cations.

冠醚交联聚砜膜的制备及其锂镁分离性能

为解决冠醚化合物用于传统液-液萃取分离锂镁时冠醚易于流失的问题,以二氨基二苯并14-冠-4(DAB14C4)和氯甲基聚砜(CMPSf)为原料,采用反应-相转化一锅法制备冠醚交联聚砜膜(DAB14C4-cr-PSf)。考察交联反应温度、反应时间、热处理时间及反应液中冠醚浓度等因素对DAB14C4-cr-PSf膜中冠醚固载量的影响,探究DAB14C4-cr-PSf膜对Li^(+)的选择吸附性及锂镁分离性能。结果表明:当交联反应时间为8 h、反应温度为45℃、70℃热水处理1.5 h、冠醚质量分数为0.5%时,DAB14C4-cr-PSf膜达到最佳冠醚固载量(0.190 mmol/g);在Flow-through模式下,DAB14C4-cr-PSf对Li^(+)的吸附量(QLi)及锂镁分离因子(α)分别为8.55 mg/g和5.96;当有K^(+)、Na^(+)等离子共存时,DAB14C4-cr-PSf膜对于Li^(+)/K^(+)、Li^(+)/Na^(+)和Li^(+)/Mg^(2+)的分离因子分别为11.41、10.50和5.69,表明DAB14C4-cr-PSf膜对Li^(+)具有选择性吸附能力,且Li^(+)/Mg^(2+)的分离性能几乎不受干扰离子影响。

修饰敏感载体PVC膜离子选择性电极的构建研究

以聚氯乙烯(PVC)作为基质,18-冠-6-醚作为离子识别体,苯二甲酸二辛酯(DOP)作为增塑剂,制备出透明的氨氮离子选择性传感膜,适配离子选择性电极。实验结果表明,18-冠-6-醚可能部分会被增塑剂所结合,在冠醚添加量为12 mg的用量下制备的选择性敏感膜性能较好;并且随着苯丙乳液的加入,能够较好增强选择性膜的稳定性;由于BB-6苯丙乳液的掺杂加入,能有效提高敏感膜对钾离子的抗干扰能力。