Effect of some potassium selective crown ethers on the permeability and structure of a phospholipid membrane

The effect of some new crown ethers on the cation efflux and phase transition parameters of dipalmitoyl phosphatidylcholine liposomes was studied. The effects were correlated with the lipophilicity of the crown ethers. The results indicate that the presence of two crown ring structures in one crown ether molecule is a prerequisite for the increase of ion permeability of liposomes. The effective crown ethers decrease the temperature, enthalpy and cooperativity of the gel-to-liquid crystalline phase transition. The crown ethers increase membrane permeability for potassium and, to a lesser extent, for rubidium and sodium. The ratio of permeability increase for potassium/rubidium significantly correlates with the lipophilicity of the crown ethers.     

Silver complexes with large crown ethers in propylene carbonate

The complex formation between large crown ethers – e.g. dibenzo-30-crown-10 – and Ag⁺ in propylene carbonate has been studied using potentiometric and calorimetric titrations. The values of the reaction enthalpies with larger crown ethers than 18-crown-6 especially with dibenzo-30-crown-10 indicate that more than six donor atoms are taking part in the interaction with the complexed cation. The values of the reaction entropies of the largest crown ethers examined indicate the high sterical requirements of the complex formation. Obviously large crown ethers are able to encapsulate the complexed cation. The effectiveness of the encapsulation however depends upon the ring size and flexibility of the crown ethers.     

Sulfur containing noncyclic and macrocyclic ligands for the complexation of Ag+ in acetone and propylene carbonate

Complex formation between silver(I) and noncyclic and macrocyclic ligands containing sulfur donor atoms was studied in propylene carbonate and acetone as solvents. Stability constants and reaction enthalpies were measured by means of potentiometric and calorimetric titrations. The noncyclic ligand with nitrogen and sulfur donor atoms forms a more stable complex than the dithiacrown ethers. With increasing ring size of the crown ethers the stability constants and the values of the reaction enthalpy increase. The values of the reaction entropy are nearly constant.     

Liquid Membrane Separations of Metal Cations Using Macrocyclic Carriers

Abstract

The selectivity in water and methanol solvents of macrocyclic crown ether ligands toward univalent and bivalent cations is well known. Incorporation of these ligands into chloroform liquid membranes separating water and salt solution phases results in a system showing selective cation transport. The cation transport rates of single cations across these liquid membranes have been correlated with equilibrium constant values for cation-macrocycle interaction in methanol. This correlation has been extended to binary cation mixtures of Cs⁺ with Li⁺, Na⁺, K⁺, and Rb⁺. A model for cation transport from these cation mixtures has been reduced to an equation which gives good agreement between measured and predicted transport rates across our liquid membranes.     

硫杂冠醚对Ag(I)和Tl(I)的萃取

基于冠醚的配位化学及软硬酸碱理论,设计并合成了五种硫杂冠醚,系统研究了其对Ag(I)和Tl(I)两种软酸离子的络合能力.模拟计算结果表明,五种冠醚与Ag(I)和Tl(I)络合后构型均发生了转变,且结构优化后的五种冠醚与Ag(I)络合过程的ΔG和ΔU均较负,表现出了一定的配位能力,而与Tl(I)络合过程的ΔG和ΔU均接近...     

Binding of the cationic fluorophore Auramine-0 to neutral and charged poly(vinylbenzo-18-crown-6) in water

Summary The cationic fluorophore Auramine-0 strongly interacts with poly(vinylbenzo-18-crown-6), a polymer which in water behaves as a typical polysoap. The intrinsic binding constant at 25°C was found to be 2.2 × 10⁴ M^–1. The binding can be modified by adding crown ether-complexable cations such as K⁺ or Cs⁺. Complexation converts the neutral polycrown ether into a polycation causing repulsion of the cationic fluorophore and a decrease in the observed fluorescence. There is some indication that the cation of the dye specifically interacts with a crown ligand.     

The association constant of macrocyclic ether–cation interactions in 1,4-dioxane/water mixtures. III. Effect of temperature on the binding

The association constant, K_a of Na⁺ with [12]crown-4, [15]crown-5 and [18]crown-6 crown ethers were determined in a binary mixture, 1,4-dioxane/water (50/50) using a Na⁺ ion selective electrode at different temperatures. K_a values were determined with the relationship, 1/K_a [L_o]^n+m–1 = (1–nP′)ⁿ(1–mP′)^m/P′, for various stoichiometries, (n:m), where P′ is the mole fraction of the complexed cation. The exothermic association constants and the thermodynamic data for cation–macrocycle complexes explained in terms of Eigen–Winkler binding mechanism are given. The binding power found for Na⁺, however, was the highest with [18] crown-6.     

RADIUM SEPARATION THROUGH COMPLEXATION BY AQUEOUS CROWN ETHERS AND ION EXCHANGE OR SOLVENT EXTRACTION

ABSTRACT

The effect of three water-soluble, unsubstituted crown ethers (15-crown-5 (15C5), 18-crown-6 (18C6) and 21-erown-7 (21C7) on the uptake of Ca, Sr, Ba and Ra cations by a sulfonic acid cation exchange resin, and on the extraction of the same cations by xylene solutions of dinonylnaphthalenesulfonic acid (HDNNS) from aqueous hydrochloric acid solutions has been investigated. The crown ethers enhance the sorption of the larger cations by the ion exchange resin, thereby improving the resin selectivity over calcium, a result of a synergistic interaction between the crown ether and the ionic functional groups of the resin. Similarly, the extraction of the larger alkaline earth cations into. xylene by HDNNS is strongly synergized by the presence of the crown ethers in the aqueous phase. Promising results for intra-Group IIa cation separations have been obtained using each of the three crown ethers as the aqueous ligands and the sulfonic acid cation exchange resin. Even greater separation factors for the radium - calcium couple have been measured with the crown-ethers and HDNNS solutions in the solvent extraction mode. The application of the uptake and extraction results to the development of radium separation schemes it discussed and a possible flowchart for the determination of ²²⁶Ra/²²⁸Ra in natural waters is presented.

     

Spacer-chromoionophores — polymethine dye substituted aza-crown ethers with increased complexation ability

Aromatic aldehyde derivatives of N-phenyl-aza-15-crown-5 ( 2 ), N-phenyl-aza-18-crown-6 ( 8 ), and benzo-15-crown-5 ( 10 ) are condensed with malononitrile and 2-amino-1,1,3-tricyano-1-propene to give light yellow to orange colored crown ether derivatives 4 , 5a , 9a , 11 , and 12 . 5a and 9a were acylated with ethyl chloroformate to give the magenta colored dyes 5b and 9b , respectively. By condensation of N-(4-nitrosophenyl)-aza-15-crown-5 3 with 2-amino-1,1,3-tricyano-1-propene the magenta dye 6a is obtained. Acylation of 6a with ethyl chloroformate leads to the deep blue colored dye 6b . In these derivatives the nitrogen or oxygen atoms of the crown ethers are part of the chromophoric system, and binding properties are affected. Further chromophoric derivatives of aza-crown ethers are studied in which these are separated from the chromophoric moiety by a spacer. N-(ω-chloroalkyl)-N-alkylanilines 14a-c were attached to aza-15-crown-5 13a-c and aza-18-crown-6 13b-c to yield the spacer crown ether derivatives 15a-c and 16a-c , respectively. The formylated spacer crown ether derivatives 17a-c and 18b were condensed with 2-amino-1,1,3-tricyano-1-propene to give the orange spacer-chromoionophores 19a-c and 20 . In these crown ether derivatives the extended conjugation is interrupted by the spacer, and good binding properties are obtained. The complex formation constants of the crown ether derivatives with Na⁺ and K⁺ are determined using ¹H NMR spectroscopy.     

The Synerqistic Solvent Extraction of Manganese by Macrocyclic Crown Ethers in Combination with Didodecylnaphthalene Sulfonic Acid: Effect of Macrocycle Substituents

Abstract

Crown ethers in combination with organophilic cation exchangers synergize the extraction of certain metai ions from aqueous solutions, and their selectivity has been thought largely dependent on the correspondence between the crown other's cavity diameter and the metal ion diameter. This work focuses on two crown ethers, tert. -butylbenzo -15-crown-5 (tBB15C5). and tert, -butylcyclohexano 15-crown-5 (tBC15C5) each of which has a cavity diameter of 1.7 to 2.2 × 10^?10 m. and their extraction of Mn²⁺ (ionic diameter 1.4 to 2.2 × 10^?10 m) from aqueous nitrate solutions. The organophilic cation exchanger used was didodecylnaphthalene sulfonic acid (HDDNS). The data show no observable complexes of the manganese salt of HDDNS     

新型冠醚及其超分子配合物研究的新进展

介绍了冠醚化学的产生、发展及应用,详细介绍了：几种新型臂式冠醚及其超分子金属配合物的合成;取代冠醚及其金属配合物的合成及应用;新型氮杂冠醚及其金属配合物的合成及应用。并对冠醚化学的发展进行了展望。     

Cation Transport Through Liquid Membranes Mediated by Photoreactive Crown Ethers. Effects of Alkali Metal Cations on Their Photoreactivities and Transporting Properties

Photoreactivities and cation transporting properties of monomeric, dimeric, and polymeric crown ethers which contain cinnamoyl residues were investigated. Photochemical cycloaddition reaction of the cinnamoyl moieties was accelerated by NaCl or KCl for the dimeric and polymeric derivatives but not for the monomeric one. The dimeric and polymeric crown ethers after irradiation in the presence of KCl showed a significant enhancement in the transport rates for Rb⁺ cation.     

The influence of cation complexation in NaClO3 and KClO3 by crown ethers on the electronic structure of salts studied by 35Cl-N.Q.R. method

Me^⊕ (Me = Na; K) cations in MeClO₃ chlorates were complexed by crown ethers (CE): 12C4, 15C5 and 18C6 in solution. In the solid phase we could obtain only Na(15C5)ClO₃ and K(18C6)ClO₃ complexes significant shift in ³⁵Cl-n.q.r. frequency with respect to the frequency of pure sodium and potassium chlorates was observed. The shifts at 77K were –2.879 MHz for Na(15C5)ClO₃ and –1.004 for K (18C6)ClO₃. For other reaction mixtures the ³⁵Cl-n.q.r. frequencies observed were the same as for the appropriate pure chlorates which confirmed that the expected complexation in the solid phase had not occurred. The investigation described in this paper proved a rapid increase in selectivity of crown ethers at the transition from the solution to the solid state. Moreover, in the solid phase of Me(CE)ClO₃ complexes a significant increase was found in the shielding effect of the Me^⊕ cation by the surrounding crown ether.     

Selectivity in Stripping of Alkali-Metal Cations from Crown Ether Carboxylate Complexes

Abstract

The potential of crown ethers (macrocyclic polyethers) as the next generation of specific extracting agents for metal ions was markedly enhanced by the introduction of crown ethers which bear pendent proton-ionizable groups (1–5). It has been shown that metal ion extraction does not require concomitant transfer of an aqueous phase anion into the organic medium (6). For potential practical applications of these proton-ionizable crown ethers in which hard aqueous phase anions (chloride, nitrate, sulfate) would be involved, this factor is of immense importance. In addition, the combination of ion binding cavities possessing fixed dimensions with protonionizable groups creates novel bifunctional chelating agents. A final factor is the case with which extracted metal ions may be stripped from the organic phase by shaking with aqueous mineral acid.     

Synthesis,Oxygenation and Catalytic Oxidation Performance of Crown Ether‐Containing Schiff Base‐Transition Metal Complexes

Mono‐Schiff bases containing a crown ether ring ( HL ¹ , HL ² , HL ³ and HL ⁴ ) and their transition metal complexes were synthesized and characterized by ¹H NMR, IR, and mass spectroscopy as well as elemental analysis. The oxygenation constants (K) of Schiff base‐Co(II) complexes were measured over the range of −5 to +25 °C, and the values of ΔH° and ΔS° were calculated based on these K values. Using Mn(III)‐Schiff base complexes, the biomimetic catalytic oxidation of styrene to benzaldehyde was carried out with 100% selectivity. Comparison of this complex with analogues not containing a crown ether moiety clearly demonstrated the influence of crown ether ring on the dioxygen affinities and biomimetic catalytic oxidation performance of the Schiff base complexes.     

高效液相色谱手性冠醚固定相的制备研究

冠醚是具有空腔且非常好的识别能力的大环聚醚化合物。系统地研究了将R-(3,3′-二溴基-1,1′-二萘基)-20-冠-6涂覆在粗制硅胶、精制硅胶、大孔硅胶、苯环修饰粗制硅胶、苯环修饰精制硅胶、苯环修饰大孔硅胶、十八烷基修饰粗制硅胶、十八烷基修饰精制硅胶、十八烷基修饰大孔硅胶、氨丙基修饰粗制硅胶表面制备10种不同支撑体的手性固定相用于苯甘氨酸和对羟基苯甘氨酸的拆分研究。研究表明大孔硅胶以及氨丙基修饰硅胶直接涂覆冠醚的柱皆不能拆分这两种氨基酸,另外硅胶表面是否修饰、以及修饰的基团对手性柱的分离能力具有影响,不同来源的硅胶也强烈地影响着手性柱的拆分效率。     

Flüssig-Flüssig-Extraktion von Metallionen mit Lariatethern

Liquid-Liquid-Extraction of Metal Ions with Lariat Ethers . Lariat ethers of various ring size and substitution are synthesized and characterized by physical data and chemical analysis. The extraction behaviour of the crown compounds towards Na⁺, K⁺, Cs⁺ and Ag⁺ in a picric acid solution has been investigated. The extraction contants for 1:1 and 1:2 complexes are determined using the equilibrium distribution data. The results show that the flexible side chain in the investigated compounds has in no case a positive effect on the metal picrate extraction.     

Microscopic details of the sensing ability of 15-crown-5-ether functionalized poly(bithiophene)

Host-guest interactions between alkali ions (Li⁺, Na⁺ and K⁺) and a functionalized poly(bithiophene) with a 15-crown-5-ether covalently linked to two adjacent thiophene rings have been analyzed using theoretical methods. Results indicate that the considerable conformational flexibility of the polymer backbone is reduced when the cation accommodates in the cavity of the macrocycle. The enthalphic and entropic contributions to the binding have been estimated using quantum mechanical calculations and molecular dynamics trajectories, respectively. The enthalpic term becomes more favorable when the size of the cation decreases, while the entropy calculated for the “free state → bound state” process decreases when the size of the cation increases. On the other hand, calculated atomic-centered charges reflect that the π-conjugated system of the conducting polymer undergoes a partial oxidation upon the binding process. Moreover, the accommodation of the alkali cation in the macrocycle produces an increase of both the ionization potential and the lowest π-π^∗ transition energy of the polymer.     

Study of the synthesis of chitosan derivatives containing benzo‐21‐crown‐7 and their adsorption properties for metal ions

Three new chitosan crown ethers, N‐Schiff base‐type chitosan crown ethers (I, III), and N‐secondary amino type chitosan crown ether (II) were prepared. N‐Schiff base‐type chitosan crown ethers (I, III) were synthesized by the reaction of 4′‐formylbenzo‐21‐crown‐7 with chitosan or crosslinked chitosan. N‐Secondary amino type chitosan‐crown ether (II) was prepared through the reaction of N‐Schiff base type chitosan crown ether (I) with sodium brohydride. Their structures were characterized by elemental analysis, infrared spectra analysis, X‐ray diffraction analysis, and solid‐state ¹³C NMR analysis. In the infrared spectra, characteristic peaks of C?N stretch vibration appeared at 1636 cm^?1 for I and 1652 cm^?1 for II; characteristic peaks of N? H stretch vibration appeared at 1570 cm^?1 in II. The X‐ray diffraction analysis showed that the peaks at 2θ = 10° and 28° disappeared in chitosan derivatives I and III, respectively; the peak at 2θ = 10° disappeared and the peak at 2θ = 28° decreased in chitosan‐crown ether II; and the peak at 2θ = 20° decreased in all chitosan derivatives. In the solid‐state ¹³C NMR, characteristic aromatic carbon appeared at 129 ppm in all chitosan derivatives, and the characteristic peaks of carbon in C?N groups appeared at 151 ppm in chitosan crown ethers I and III. The adsorption and selectivity properties of I, II, and III for Pd²⁺, Au³⁺, Pt⁴⁺, Ag⁺, Cu²⁺, and Hg²⁺ were studied. Experimental results showed these adsorbents not only had good adsorption capacities for noble metal ions Pd²⁺, Au³⁺, Pt⁴⁺, and Ag⁺, but also high selectivity for the adsorption of Pd²⁺ with the coexistence of Cu²⁺ and Hg²⁺. Chitosan‐crown ether II only adsorbs Hg²⁺ and does not adsorbs Cu²⁺ in an aqueous system containing Pd²⁺, Cu²⁺, and Hg²⁺. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1886–1891, 2002     

Studies of the Size-Selective Extraction of Alkali Metal Ions by the Synergistic Extraction System,Crown Ether-DI(2-Ethylhexyl) Phosphoric Acid-Benzene

Abstract

In order to take practical advantage of the size-selective cation-coordinating ability of the cyclic polyethers (crown ethers), experiments seeking a means of avoiding the problem of solubilizing a mineral-acid anion in a nonpolar organic diluent were performed. Mixtures of several known extractants and crown ethers were tried. Results presented indicate that organic soluble cation exchangers mixed in solution with crown ethers produce a synergistic extractant mixture that largely exhibits the size-selective properties expected of the crown ether. Data are presented for the extraction of macro concentrations of alkali metals by di(2-ethylhexyl) phosphoric acid—dicyclohexyl-18-crown-6 mixtures at a single pH, and at nonloading condition(σ metal cone < 0.04 M) as a function of pH, 2 to 6. In both cases potassium is synergized most strongly presumably because of its best fit to the crown ether cavity. Other data indicate, however, that the size-fit principle is not as consistent for all alkali metal ions and crown ethers as for potassium and dicyclohexyl-18-crown-6. Other effects such as competition for ion hydration and aqueous-phase distribution of the complex may have important effects that have not been elucidated.