Extraktion von alkali- und erdalkalimetallionen mit (sym-dibenzo-14-krone-4-oxy)- und (sym-dibenzo-16-krone-5-oxy)-carbonsäuren

(Extraction of alkali on alkaline earth metal ions with (sym-dibenzo-14-crown-4-oxy)- and (sym-dibenzo-16-crown-5-oxy)-carboxylic acids.)The extraction of lithium, sodium, potassium, calcium and some other metal ions with dibenzo-4-crown-4-oxy- and dibenzo-16-crown-5-oxycarboxylic acids containing the groups -CH₂COOH, -(CH₂)₂COOH, -(CH₂)₃COOH, -CH(C₂H₅)COOH and -CH(C₄H₉)COOH was studied. The extraction increases as a function of the lipophilic character of the carboxylic acid group. Calcium, barium and strontium ions are better extracted than Li⁺, Na⁺ and K⁺; there are only small differences among the alkaline earth metal ions. Evaluated from the extraction data, the composition of the extracted species was 1:1 (metal/ligand) for Li⁺, and 1:2 for CaCa²⁺; Na⁺ and K⁺ favour the formation of 1:2 complexes with dibenzo-14-crown-4-derivatives bbut 1:1 complexes with dibenzo-16-crown-5-oxy-carboxylic acids. The dependence of the distribution ratio on pH does not provide unequivocal evidence for the composition of the extracted compounds.     

Electrochemical studies on ion-selective polymer membrane electrodes

The selectivity and response of neutral carrier based polymer membrane electrodes are investigated via exchange current measurements for systems containing valinomycin, dibenzo-18-crown-6, and plasticizer alone in a polyvinyl chloride matrix. Using a transient galvanostatic step method, apparent exchange current densities of 1.3 X 10^?3 A/cm², 5.4 X 10^?6 A/cm², and 2.2 X 10^?9 A/cm² were obtained with K⁺ as the primary ion for the three types of membranes, respectively. Preliminary results indicate that the exchange current data obtained with this technique are complementary to the potentiometric response observed for the membranes studied.     

Cation transport at 25°c from binary Na+Mn+, Cs+Mn+ and Sr2+Mn+ nitrate mixtures in a H2OCHCl3H2O liquid membrane system containing a series of macrocyclic carriers

Cation fluxes from binary mixtures of either Na⁺, Cs⁺ or Sr²⁺ with other alkali metal cations, alkaline earth metal cations, and Pb²⁺ through a H₂OCHCl³H₂O bulk liquid membrane system containing one of several macrocyclic carriers have been determined Nitrate salts were used in all cases. The most selective transport of Na⁺ over all other cations studied was found with the carrier cryptand [2.2.1]. Selective transport of Na⁺ relative to Li⁺, Cs⁺ and the alkaline earth cations was found with cryptand [2.2.2B] and cryptand [2.2.2D]. The ligands 21-crown-7 and dibenzo-24-crown-8 showed selective transport of Cs⁺ over the second cation in all cases. Several macrocycles showed selectivity for Sr²⁺ over the second cation with the macrocycle 1,10-diaza-18-crown-6 showing the highest selectivity for this cation of all ligands studied. Relative fluxes from binary cation mixtures are rationalized in terms of macrocycle cavity size, donor atom type and ring substituents.     

Sodium ion-selective membrane electrode based on a new crown ether

A sodium ion-selective PVC membrane electrode based on di(o-methoxy)stilbenzo-24-crown-8 is reported. The electrode gives a near-Nernstian response in the range 9×10^?6–1×10^?2 M sodium ion and can be used in the pH range 5–8.5. Selectivity coefficients are 1.8×10^?1 (K⁺), 2.0×10^?4 (Li⁺) 2.5×10^?2 (NH⁺₄) and about 10^?4 for Mg²⁺, Ca²⁺ and Ba²⁺.     

Stability of Complexes of NH4 + with 18-Crown-6, Dicyclohexyl-18-Crown-6, Dibenzo-18-Crown-6 and Dibenzo-24-Crown-8 in Water Saturated Nitrobenzene

From extraction experiments with ²²Na tracer, the exchange extraction constants corresponding to the NH₄ ⁺(aq) + NaL⁺ (nb)NH₄L⁺(nb) + Na⁺ (aq) equilibrium taking place in the two-phase water-nitrobenzene system (L = 18-crown-6, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and dibenzo-24-crown-8; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the NH₄L⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the order dibenzo-24-crown-8 (DB24C8) < dibenzo-18-crown-6 (DB18C6) < dicyclohexyl-18-crown-6 (DCH18C6) < 18-crown-6 (18C6).     

Ion transport numbers in crown-containing polymers

The predominant participation of anions of sorbed electrolytes in electrical charge transfer in polymers was demonstrated based on measurement of the transport numbers of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Tl⁺, and NO₃ ^–ions through homogeneous polymer membranes containing dibenzo-18-crown-6 or dibenzo-24-crown-8. The coordination reaction of the cations with the crown ethers in the polymer phase is the cause of the decrease in the proportion of cations in electrical charge transfer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 310–314, February, 1990.     

1,4,7,10-Tetraoxacyclododecane(12-Crown-4) as Neutral Carrier for Lithium Ion in Lithium Ion Selective Electrode

Abstract

1,4,7,10-Tetraoxacyclododecane (12-crown-4) (I) and its lithium complex (II) are used as neutral carriers for lithium ion in polyvinylchloride membrane ion selective electrodes. The lithium response varies with concentration, being near Mernstian at low (10^?5-10^?4 M) concentrations and sub-Nernstian (24-28 aV) at higher concentrations (10^?3 M). The selectivity coefficients K_Li ^Pot _M for II are: Na⁺ (0.12), K⁺ (0.66), Cs⁺ (0.15), Mg²⁺ (1.6 × 10^?4), Ca²⁺ (3.1 × 10^?4), Ba²⁺ (9.5 × 10^?7), NH⁺ ₄ (9.0 × 10^?2), H⁺ (2.2).     

Ionophores in Rubidium Ion‐Selective Membrane Electrodes

Binaphthyl‐based crown ethers incorporating anthraquinone, benzoquinone, and 1,4‐dimethoxybezene have been synthesized and tested for Rb⁺ selective ionophores in the poly(vinyl chloride) (PVC) membrane. The membrane containing NPOE gave a better Rb⁺ selectivity than those containing either DOA or BPPA as a plasticizer. The response was linear within the concentration range of 1.0×10^?5–1.0×10^?1 M and the slope was 54.7±0.5 mV/dec. The detection limit was determined to be 9.0×10^?6 M and the optimum pH range of the membrane was 6.0–9.0. The ISE membrane exhibits good selectivity for Rb⁺ over ammonium, alkali metal, and alkaline earth metal ions. Selectivity coefficients for the other metal ions, log K^Pot were ?2.5 for Li⁺, ?2.4 for Na⁺, ?2.0 for H⁺, ?1.0 for K⁺, ?1.2 for Cs⁺, ?1.6 for NH₄⁺, ?4.5 for Mg²⁺, ?5.0 for Ca²⁺,?4.9 for Ba²⁺. The lifetime of the membrane was about one month.     

Effect of structural variations of dibenzocrown ether resins and their acyclic analogues upon ion-pair sorption of alkali metal salts from aqueous and aqueous methanol solutions

Abstract

Ion-pair sorption of alkali metal salts from aqueous and aqueous methanol solutions by acyclic and cyclic dibenzopolyether resins possessing different side arm groups such as hydroxy, methoxy and carboxy has been investigated. The results reveal that both sorption selectivity and efficiency are influenced by: (1) the methanol content of the aqueous sample solution; (2) the acyclic or cyclic nature of the polyether unit; (3) the conformational positioning of the side arm group with respect to the crown ether cavity; and (4) the identity of the counteranion species of the alkali metal salt. For sym-(C₃H₇)(R′)dibenzo-16-crown-5 resins, the sorption selectivity and efficiency increased as the R′ group was varied: -OCH₃ < -OH < -OCH₂CO₂H. The highest sorption efficiency and Na⁺ selectivity was obtained for sym-(propyl)dibenzo-16-crown-5-oxyacetic acid resin (7) in which the pendent carboxylic acid group is oriented over the crown ether cavity. The use of a less hydrated anion in the alkali metal salt species enhances the ion-pair efficiency: SO₄ ^2- < NO₃ ^?, Cl^?, Br^? < I^? < SCN^?. Monovalent metal selective sorption was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂ and CaCl₂ by resin 7.     

Complex Formation of Potassium Hexachloroplatinate with 18-Crown-6 and Dibenzo-18-Crown-6 in Acetonitrile

The products of the reactions between potassium hexachloroplatinate {K₂PtCl₆} and 18-crown-6 or dibenzo-18-crown-6 in acetonitrile were studied. Pure crystalline compounds [2K·2(18-crown-6)· 2CH₃CN]²⁺·[PtCl₆]^2-·2H₂O, [2K·dibenzo-18-crown-6·CH₃CN]^{2 +}·[PtCl₆]^{2 -}, and [2K·dibenzo-18-crown-6·CH₃CN]^{2 +}·[Pt₂Cl₁₀]^{2 -} were obtained. Physicochemical properties of these compounds were studied, and their near- and far-IR IR spectra and thermogravimetric curves were considered. The composition of the complexes is determined by metal:ligand molar ratio and crown ether nature. It was found that acetonitrile is coordinated via the nitrogen atom.     

Extraction of microamounts of calcium into nitrobenzene using hydrogen dicarbollylcobaltate in the presence of dibenzo-21-crown-7 and dibenzo-24-crown-8

Extraction of microamounts of calcium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of dibenzo-21-crown-7 (DB21C7) and dibenzo-24-crown-8 (DB24C8) has been investigated. The equilibrium data have been explained assuming that the complexes HL⁺, CaL²⁺, CaL₂²⁺ and CaHL₂³⁺ (L = DB21C7, DB24C8) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.     

Preparation and crystal structure of bis(dibenzo-18-crown-6)-(tetrachlorocuprato(II)-Cl,Cl′, Cl″, Cl‴)dipotassium diaqua(dibenzo-18-crown-6)potassium dichlorocuprate(I)-dibenzo-18-crown-6

New mixed complex compound bis(dibenzo-18-crown-6)(tetrachlorocuprato(II)-Cl, Cl′, Cl″, Cl?) dipotassium diaqua(dibenzo-18-crown-6)potassium dichlorocuprate(I)dibenzo-18-crown-6 [(CuCl₄)[K(Db18C6)]₂]·[K(Db18C6)(H₂O)₂]⁺·[CuCl₂]^?·Db18C6 was prepared and its structure was studied by the X-ray structural analysis. The structure was found to be disordered. The asymmetric part of its unit cell contains 1/4 of each of its four components. For a given [CuCl₄]^2? anion its Cu²⁺ cation is disordered over two equally probable positions and its independent Cl atom is disordered over three positions differing by occupancy. In this structure two [K(Db18C6)]⁺ fragment of the complex molecule and the complex cation [K(Db18C6)(H₂O)₂]⁺ are of guest-host type with K⁺ cation as the guest. In this structure the statistically disordered alternating cations and Db18C6 molecules form infinite chains. The statistically disordered [CuCl₂]^? anions also form infinite chains.     

Polarographic Study of Thallium(I) Complexes with Large Crown Ethers in Binary Acetonitrile-Water Mixtures

The complexation reactions between the Tl⁺ ion and large crown ethers dibenzo-30-crown-10 (DB30C10), dibenzo-27-crown-9 (DB27C9), dibenzo-24-crown-8 (DB24C8) and dibenzo-21-crown-7 (DB21C7) were studied in different acetonitrile-water mixtures at 25°C using an a.c. polarographic technique. The stoichiometry and stability of the complexes were determined by monitoring the shift in peak potential of the polarographic waves of the metal ion against the crown concentration. In all solvent mixtures used, the stability of the resulting 1:1 complexes was found to vary in the order DC24C8 » DB30C10 > DB21C7 > DB27C9 > DB24C8. There is an inverse relationship between the complex formation constants and the amount of water in the mixed solvent. In all cases, a linear relation was observed between log K_f and the mole fraction of acetonitrile in its mixtures with water.     

Determination of caesium microamounts by isotope dilution with substoichiometric separation

Selectivity of isotope dilution analysis with substoichiometric separation for caesium determination has been investigated. Caesium can be extracted with a substoichiometric amounts of bis 1,2-dicarbollylcobaltate in nitrobenzene in the presence of dibenzo-18-crown-6. The method is selective. Other metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺, Fe³⁺, Al³⁺) do not interfere.     

Applications of Macrocyclic Polyethers in Analytical Sensors and Ion Separation

Artificial macrocyclic polyethers were synthesized and applied as neutral carriers for ion-selective PVC membrane electrodes, ion-chromatographic packing materials, extractants and adsorbents for ion separation, coating materials for piezoeletrical membrane sensors for organic species, and ion-transport carriers through liquid membranes. Ion-selective electrodes such as those for K⁺ Na⁺, UO₂²⁺, Cs⁺, Pb²⁺, Fe³⁺, Hg²⁺ and Ag⁺ ions based on crown ether-phosphotungstic acid (PW) precipitates and dithio crown ethers respectively were prepared and showed good sensitivity and selectivity. Crown ether-PW precipitates were applied as adsorbents of rare-earth ions and some common heavy-metal ions. Some rare-earth ions were easily extracted with crown ethers, especially 15-crown-5. Poly(stytene/divinyl benzene) cryptand-22 resin was synthesized and applied as a bifunctional stationary phase of ion chromatography to separate bom cations and anions, even some organic carboxylate geometric isomers. Crown ethers such as mono-benzo-15-crown-5 was successfully applied as a coating material on piezoelectric quartz membrane sensors for some organic species. The oscillation frequency of the crown-ether quartz-membrane sensor was sensitive to organic vapours such as amines and alcohols. Upon adsorption of organic species on the crown-ether quartz membrane, the oscillation frequency of the sensor decreased obviously. Special crown ether such as dibenzo-16-crown-5-oxyacetic acid, decyl-cryptand-22 and 1, 4-dihydro-pyridine-18-crown-5 were synthesized and successfully applied as ion-transport carriers (ionophores) for transport of Na⁺ K⁺ and Mg²⁺ ions through liquid membranes.     

Stabilities in Water of Alkali Metal Ion Complexes with Dibenzo-24-crown-8 and Dibenzo-18-crown-6 and Their Transfer Activity Coefficients from Water to Nonaqueous Solvents

Stability constants K _ML for the 1:1 complexes of Na⁺, K⁺, Rb⁺, and Cs⁺ with dibenzo-24-crown-8 (DB24C8) and dibenzo-18-crown-6 (DB18C6) in water have been determined by a capillary electrophoretic technique at 25°C. The K _ML sequence is Na⁺ < K⁺ < Rb⁺ < Cs⁺ for DB24C8 and Na⁺ < K⁺ > Rb⁺ > Cs⁺ for DB18C6. Compared with DB18C6, DB24C8 exhibits higher selectivity for K⁺ over Na⁺, but lower selectivity for K⁺, Rb⁺, and Cs⁺. To evaluate the solvation of the complexes in water, their transfer activity coefficients sH₂O between polar nonaqueous solvents and water have been calculated. The sH₂O values provide the following information: interactions with water of the metal ions and of the crown-ether oxygens are greatly reduced upon complexation and the complexes undergo hydrophobic hydration in water; the character of each alkali metal ion in solvation is more effectively masked by DB24C8 than by DB18C6, because of the larger and more flexible ring structure of DB24C8. Solvent effects on the complex stabilities are discussed on the basis of the sH₂O values.     

Synthesis and applications of (5-substituted benzimidazolo)-benzo-15-crown-5 and 4,4′-bis-benzimidazolo-dibenzo-15-crown-5 for the colorimetric detection of Au3+

In the present work, we have reported the synthesis of benzimidazoles functionalized crown ether derivatives of 4-formyl benzo-15-crown-5/4,4′-diformyl dibenzo-15-crown-5 and substituted diamine pyridine using sulfamic acid as a catalyst in DMSO. These molecules are used for the colorimetric determination of Au³⁺ selectively among other metal cations such as Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Au³⁺ and Ag⁺ ions_.     

Bifunctional Ion‐Selective Electrode Based on C60‐Cryptand 22 for Silver and Iodine Ions

Fullerence C60‐cryptand 22 was prepared and successfully applied as the electric carrier in the PVC electrode membrane of a bifunctional ion‐selective electrode for cations, e.g., Ag⁺ ions as well as anions, e.g., I^? ions. The bifunctional ion‐selective electrode based on C60‐cryptand 22 can be applied as a Silver (Ag⁺) ion selective electrode with an internal electrode solution of 10^?3 M AgNO₃ in water (pH = 6.3), or as an Iodide (I^?) ion selective electrode with an acidic internal electrode solution of 10^?4 M KI_(aq) (pH = 2) in which the cryptand 22 is protonated, and the C60‐cryptand 22 is changed to C60‐Cryptand22–H⁺ and becomes an anionic electro‐carrier to absorb the I^? ion. The Ag⁺ ion selective electrode based on C60‐cryptand 22 gave a linear response with a near‐Nernstian slope (59.5 mV decade^?1) within the concentration range 10^?1‐10^?3 M Ag⁺_(aq). The Ag⁺ ion electrode exhibited comparatively good selectivity for silver ions, over other transition‐metal ions, alkali and alkaline earth metal ions. The Ag⁺ ion selective electrode with good stability and reproducibility was successfully used for the titration of Ag⁺_(aq) with Cl^? ions. The Iodide (I^?) Ion selective electrode based on protonated C60–cryptand22‐H⁺ also showed a linear response with a nearly Nernstian slope (58.5 mV decade^?1) within 10^?1 ‐ 10^?3 M I^? _(aq) and exhibited good selectivity for I^? ions and had small selectivity coefficients (10^?2–10^?3) for most of other anions, e.g., F^? , OH^?, CH₃COO^?, SO₄^2?, CO₃^2?, CrO₄^2?, Cr₂O₇^2? and PO₄^3? ions.     

Synthesis and crystal structure of aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)-(tetrachlorocuprato(II)-Cl)potassium

New mixed complex compound aqua(dibenzo-18-crown-6)potassium (dibenzo-18-crown-6)(tetrachlorocuprato(II)-Cl)potassium, [K(CuCl₄)(Db18C6)]^? · [K(Db18C6)(H₂O)]⁺, is synthesized and its crystal structure is studied by the method of x-ray structural analysis. The structure includes two independent complex ions, both of guest-host type: two cations K⁺ are located in the respective cavities of the Db18C6 crown-ligand (one in each) and each is coordinated by all its six O atoms and one Cl atom of the anion-ligand [CuCl₄]^2? or O atom of the ligand water molecule. Coordination of these two K⁺ cations is completed to hexagonal pyramidal one by formation by each of unusually weak coordination bond K⁺ → π(\(C\dddot - C\)) with two C atoms of respective benzene ring in the neighboring Db18C6 ligand. In this crystal structure the complex anions and cations form dual infinite chains via these coordination bonds and interionic O-H?Cl hydrogen bonds.     

Study of Bulk Membrane Transport of Some Heavy Metal Cations Using Three Macrocyclic Ligands Containing Oxygen and Nitrogen Heteroatoms

The transport experiments of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺ and Pb²⁺ metal cations were carried out by dibenzo-18-crown-6 (DB18C6), dibenzyl-diaza-18-crown-6 (Dibenzyl-diaza-18C6) and di-tert-butyl-dibenzo-18-crown-6 (Di-tert-butyl-DB18C6) using chloroform (CHCl₃), 1,2-dichloroethane (1,2-DCE) and nitrobenzene (NB) organic solvents as liquid membranes. The source phase contained equimolar concentration of these metal cations and the source and receiving phases being buffered at pH=5 and pH=3, respectively. The obtained results show that the selectivity and the efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membranes in these experiments. A good selectivity was observed for silver (I) ion by dibenzyl-diaza-18C6 in all membrane systems. Dibenzo-18C6 and di-tert-butyl-DB18C6 showed the highest transport efficiency for cobalt (II) ion. The effect of stearic acid on transport efficiency was also investigated and the results show that the efficiency of transport of the heavy metal cations increases in the presence of this organic acid.