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.     

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.

     

Ligands for selective metal ion extraction: A molecular modeling approach

We present a density functional theory (DFT) based study on interaction of alkali metal cations (Li⁺ and Na⁺) with macrocyclic crown ethers of different ring sizes. The minimum energy structures, binding energies, and binding enthalpies of crown ether–cation complexes have been determined with a correlated hybrid density functional, namely Becke’s three-parameter functional, B3LYP using a split valence basis function, 6-311++G(d, p). Geometry optimizations for all the crown ether–cation complexes were carried out with several initial guess structures based on semi-empirical PM3 optimized results. For both metal ions, the calculated values of binding energy and binding enthalpy increase with the increase in size of the crown ether ring, i.e. with the increase in the number of donor oxygen atoms in crown ether. The calculated values of gas phase binding energy for lithium ions are always higher than those for sodium ions in the case of all macrocyclic crown ethers studied at present. The calculated values of binding enthalpy are in good agreement with the reported experimental data.     

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     

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.     

Photo and thermal properties of cinnamoyl Pluronic F‐127

Cinnamoyl chloride was covalently attached to the ends of Pluronic F‐127 chains. The molar ratio of cinnamoyl groups to Pluronic F‐127 of the cinnamoyl Pluronic F‐127 (Cin‐Plu) was calculated to be about 1:1 on a ¹H NMR spectrum. The melting point (around 52 °C) of Cin‐Plu was somewhat less than that (around 55 °C) of Pluronic F‐127. Furthermore, the melting point of Cin‐Plu decreased to around 50 °C on UV irradiation. The micellization temperature of Pluronic F‐127 was around 15 °C and it was affected neither by the covalent attachment of cinnamoyl chloride nor the UV irradiation. On the other hand, Pluronic F‐127 solution (22% w/v) in distilled water became a gel at around 28 °C and Cin‐Plu solution (22% w/v) at around 39 °C. The elevation in the gelation temperature is possibly because the cinnamoyl group interferes with the intermolecular hydrophobic interaction of propylene oxide blocks, a main cause for the gelation. Cin‐Plu solution (22% w/v) which had been subjected to UV irradiation (365 nm, 400 W) for 3 h exhibited no gelation temperature but a gradual increase in viscosity when the solution temperature increased from 17 °C to 37 °C, possibly due to the coexistence of dimeric Cin‐Plu and monomeric Cin‐Plu. © 2013 Society of Chemical Industry     

Potentiometric and Thermodynamic Studies of 2-Acrylamidosulfamethazine and Its Metal Complexes in Monomeric and Polymeric Forms

2-Acrylamidosulfamethazine (ASM) was synthesized and characterized by elemental analyses and IR spectroscopy. Proton-monomeric ligand dissociation and metal-monomeric ligand stability constants of ASM with some metal ions were determined potentiometrically in 0.1 M KCl and 40% (v/v) ethanol–water mixture. In the presence of 2,2-azobisisobutyronitrile as an initiator, the dissociation and stability constants of ASM were determined in polymeric form (PASM). The influence of temperature on the dissociation of ASM and the stability constants of their complexes in monomeric and polymeric forms were precisely studied. The pK^H value of PASM was found to be higher than ASM, which indicates that the vinyl group in the monomeric form decreases the electron density on nitrogen and hence reduces the N–H bond strength. The stability constants of the metal complexes in polymeric form are higher than those of the monomeric form. This reveals that the ligand in a polymeric form may be considered as a better complexing agent.     

Polymer Complexes XLIV. Potentiometric and Thermodynamic Studies of Monomeric and Polymeric Complexes Containing 2-Acrylamido-2-methylpropanesulfonic Acid

Proton-monomeric ligand dissociation and metal-monomeric ligand stability constants of 2-acrylamido-2-methyl-1-propanesulfonic acid with several metal ions were determined potentiometrically in water and 0.1 M KCl. In the presence of 2,2-azobisisobutyronitrile as an initiator, the dissociation and stability constants of AMS were determined for the polymeric form (PAMS). The influence of temperature on the dissociation of AMS and the stability constants of their complexes in monomeric and polymeric forms were studied. The vinyl group in the monomeric form decreases the electron density and hence reduces the N–H bond strength (lower pK^H ₂ value). The stability constants of the metal complexes in the polymeric form (better complexing agent) are larger than those of the monomeric form.     

Polymer Complexes XXXV. Potentiometric and Thermodynamic Studies of Monomeric and Polymeric Complexes Containing 2-Acrylamidosulphamethoxazole

Summary 2-Acrylamidosulphamethoxazole (ASM) was synthesized and characterized by elemental analyses, IR and ¹H NMR spectra. Proton-monomeric ligand dissociation and metal-monomeric ligand stability constants of ASM with some metal ions were determined potentiometrically in 0.1 M KCl and 40 % (vh) ethanol-water mixture. In the presence of 2,2-azobisisobutyronitrile as initiator, the dissociation and stability constants of ASM were determined in polymeric form (PASM). The influence of temperature on the dissociation of ASM and the stability constants of their complexes in monomeric and polymeric forms were precisely studied. The pK₂^H value of PASM was found to be higher than ASM, this means that the vinyl group in the monomeric form decreases the electron density and hence reduces the N-H bond strength. The stability constants of the metal complexes in polymeric form are higher than those of the monomeric form. This reveals that the ligand in a polymeric form is considered as a better complexing agent.     

Chemical modification of chitosan: Synthesis and characterization of chitosan‐crown ethers

Four novel Schiff‐type chitosan (CTS)‐crown ethers were synthesized through a reaction between ? NH₂ in CTS or crosslinked chitosan (CCTS) and ? CHO in 4′‐formylbenzo‐crown ethers, and four secondary‐amino‐type CTS‐crown ethers were prepared through the reduced reaction of NaBH₄, respectively. Their structures were characterized by elemental analysis, Fourier transform infrared (FTIR) spectra analysis, solid‐state ¹³C‐NMR analysis, and X‐ray diffraction (XRD) analysis. The elemental analysis results showed that the percentage of nitrogen in all CTS‐crown ethers were lower than that of CTS or CCTS. From the FTIR data of CTS, CCTS, and CTS‐crown ethers I–VIII, we saw that the characteristic peaks of C?N, N? H, and Ar appeared and that the characteristic peaks of pyranoside in the chain of CTS or CCTS were not destroyed. The XRD spectra demonstrated that CTS‐crown ethers I–VIII gave lower crystallinities than CTS or CCTS, which indicated that these compounds were considerably more amorphous than CTS or CCTS. In the solid‐state ¹³C‐NMR spectra, all of these CTS‐crown ethers had a particular peak of aromatic at 128 or 129 ppm, and the greatest difference between Schiff‐type CTS‐crown ethers and secondary‐amino‐type CTS‐crown ethers was that the Schiff‐type CTS‐crown ethers had the particular peak of C?N, which disappeared in secondary‐type CTS‐crown ethers. All these facts confirmed that the structures of CTS‐crown ethers I–VIII were as expected. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2221–2225, 2003     

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.     

Effect of Ring-Size Variation within Dibenzocrown Ether Resins upon Ion-Pair Sorption of Alkali-Metal Cations from Aqueous and Aqueous Methanol Solutions

Abstract

A batch analysis method has been developed for evaluation of metal salt sorption by crown ether polymers. Selectivity in competitive alkali-metal chloride sorption by a series of formaldehyde condensation polymers of dibenzocrown ethers is influenced by the relationship between the crown ether cavity size and metal ion diameter, as well as the degree of hydration of the metal salt. Effective and selective sorption of KCl from the other alkali-metal chlorides was obtained with a dibenzo-18-crown-6 resin. Excellent sorption selectivity for the monovalent metal chlorides was noted for competitive ion-pair sorption of NaCl, KCl, MgCl₂, and CaCl₂ by this resin. This resin was examined as a stationary phase for selective column separation of KCl from alkali-metal chlorides and of KCl and NaCl from alkali-metal and alkaline-earth chloride mixtures in 80% methanol—20% water.     

Effect of Crown Ethers on Sr2+, Ba2+, and Ra2+ Uptake by Tunnel‐Structure Ion Exchangers

Abstract

The effect of 15‐crown‐5 and 18‐crown‐6 ethers on the uptake of alkaline earth cations by tunnel‐structure ion exchangers polyantimonic acid (PAA) and cryptomelane manganese dioxide (CMD) was examined. In the case of PAA, 15‐crown‐5 and especially 18‐crown‐6 strongly influence the uptake of Sr²⁺ vs Ba²⁺ and Ra²⁺. For separation of the Ra²⁺‐Ba²⁺ pair, the effect of the crown ethers is insignificant. In CMD a small difference in complex formation between crown ethers and Ba²⁺ and Ra²⁺ gives an increase of separation. This effect is observed especially in 15‐crown‐5 solutions.     

Protonation of Macrocyclic Polyethers

Proton affinity of various “crown” ethers is discussed. Equations are given for simultaneous calculation of the complexation and the dissociation constants from conductivity data. pK^f in 1.2-dichloroethane is 8.6 and 8.3, respectively, for the cis-syn-cis and the cis-anti-cis isomers of dicyclohexyl-18-CR-6, the most basic among the investigated “crown” ethers. pK^f = 8.2 for the mixture of these isomers in acetonitrile (AN). The effect of water on pK^f of “crown” ethers in aprotic solvents is discussed. It is suggested that a monohydrate of the “oxonium-crown” rather than a “hydronium-crown” may be formed. The proton binding capacity of “crown” ethers may be applied for extraction of acids and in catalysis. Dicyclohexyl-24-CR-8 has been found to be an equally effective extractant for HNO₃ as the Dicyclohexyl-18-CR-6.     

On the Mechanism of the Thermal Polymerization of Linseed Oil

The monomeric and polymeric glycerides present in thermally polymerized linseed oils can be separated quantitatively by molecular distillation. Analysis of the fatty acids of monomeric and polymeric glycerides indicate the occurence of intra- and intermolecular condensations respectively. Whereas in the former reaction, leading to the formation of bicyclic, dimeric fatty acid groups within the orginal glycerides, no increase in the molecular weight of the oil takes place, in the latter one, characterized by an increase in the molecular weight, fatty acids of different glyceride molecules are involved. It is shown, however, that the overall increase in molecular weight is due to the dimeric glycerides which are formed by interesterification reactions between glyceride monomers containing dimeric fatty acid groups, the latter resulting from intramolecular condensation.     

阳离子防膨剂的室内性能评价研究

介绍了粘土稳定剂的分类和防膨机理,通过膨胀仪测量了KCI、阳离子聚丙烯酰胺、大阳离子聚合物PTA和小阳离子聚合物NW粘土防膨剂在不同浓度下粘土的静态膨胀量,综合比较哪种防膨剂效果更好。     

Potentiometric and thermodynamic studies of vinylacetic acid and its metal complexes in monomeric and polymeric forms

Proton–monomeric ligand dissociation and metal–monomeric ligand stability constants of vinylacetic acid (VA) with some metal ions were calculated potentiometrically in 0.1M KCl. Also, in the presence of 2,2′‐azobisisobutyronitrile as initiator, the proton–polymeric ligand dissociation and metal–polymeric ligand stability constants were calculated. The effect of temperature on the dissociation of VA and the stability of its formed complexes were studied in monomeric and polymeric forms. The corresponding thermodynamic functions were derived and discussed. The dissociation process was nonspontaneous, endothermic, and entropically unfavorable. The formation of the metal complexes was found to be spontaneous, endothermic, and entropically favorable. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 952–956, 2005     

Selective ion exchange polymers

The current trends in the synthesis of selective ion exchange polymers are presented in the order of functional polymers incorporating oxygen, nitrogen, phosphorous and sulfur ligands and also macrocyclic ligands. Chelating ion exchange polymers incorporating hydroxyoximes, aminophenols, polyethyleneimines, selective anion exchange resins incorporating pseudocrown ethers, or isothiourea groups and polymeric crown ethers are discussed in detail.     

Wechselwirkungen in Kristallen. 136. Protonierte Di(pyrid-2-yl)amin-Salze mit verschiedenen Anionen: Monomeres Tetraphenylborat sowie Bis(trifluormethylsulfonat), dimeres Squarat und polymeres Chlorid-Dihydrat

Interactions in Crystals. 136. Protonated Dipyridylamine Salts with Different Anions: Monomeric Tetraphenylborate as well as Bis(trifluormethylsulfonate), Dimeric Squarate and Polymeric Chloride Dihydrate Di(pyrid-2-yl)amine is monoprotonated by acetic, squaric as well as hydrochloric acid and diprotonated by trifluoromethylsulfonic acid. To explore the anion and hydrogen-bridge dependency of its salts, crystals of the monomeric tetraphenylborate, the dimeric squarate as well as the bis(trifluoromethylsulfonate) and the polymeric chloride hydrate have been grown and their structures determined: Separated by bulky tetraphenylborate anions, pyrid-2-yl(2′-pyridinium) amine cation contains an intramolecular hydrogen bridge N^⊕H…︁N and is slightly folded. The squarate salt dimer exhibits additional bridges, N H…︁O^⊖ and O H…︁O. The severely twisted di(2-pyridinium)amine dication is connected to its trifluormethylsulfonate counter anions by altogether three H-bridges, two N^⊕H…︁O and one N H…︁O. The chloride dihydrate crystallizes in layers of 16-membered rings, formed from three Cl anions and five water molecules. The diversity of the hydrogen-bridge dominated salt structures is discussed based on comparison with selected literature examples and on PM3 calculations.     

Hydrogen-bonded polymer complexes of macrocycles containing a pyridyl moiety and carboxyl-functionalized polystyrenes An approach to H-bonded rotaxanes

Summary Copolystyrenes complexed with macrocyclic compounds through hydrogen bonding have been synthesized by the copolymerization of styrene with the complex of 4-vinylbenzoic acid and crown ethers containing a 2,6-pyridyl moiety. The glass transition temperatures of the copolymeric complexes are significantly lower than that of the simple copolymer, which shows that the carboxylic acid groups in the polymer backbone do not intermolecularly dimerize. The UV absorption spectra of polymeric complexes suggest that they have complex structures similar to that of the low-molecular-weight complexes of 4-ethylbenzoic acid and the crown ethers. Received: 31 March 1999/Accepted: 27 April 1999