Proton-ionizable crown compounds. 11. Synthesis of macrocyclic ligands containing two sulfonamide groups and chloro substituents or pyridine subcyclic units and a preliminary study of cation transport by three of these ligands

Five new macrocyclic ligands each containing two sulfonamide groups have been prepared. Three of these compounds contain one or two chloro substituents and the other two have one or two pyridine subcyclic units. A seventeen-membered ring ligand (4) was found to be an excellent transport agent for all alkali metal cations in a water-methylene chloride-water bulk liquid membrane system when the pH of the source phase was 13 or higher. The chlorine-substituted analog (5) was a poor transport agent for the alkali metal cations possibly because the chlorine atom blocked entry to the macrocycle cavity. An open-chain analog containing two sulfonamide groups was particularly effective in transporting cesium ions.     

Sulfonamides as ionophores for ion-selective electrodes. II. Macrocyclic ligands containing two sulfonamide groups as ionophores

Ten macrocyclic compounds (1–10), each containing two sulfonamide groups have been incorporated into PVC membrane electrodes as ionophores. Their selectivity towards alkali and alkaline earth metal cations has been studied and compared to selectivities found in cation transport experiments.     

Proton ionizable crown compounds. 18. Comparison of alkali metal transport in a H2O-CH2Cl2-H2O liquid membrane system by four proton-ionizable macrocycles containing the dialkylhydrogenphosphate moiety

The macrocycle-mediated fluxes of alkali, alkaline earth, and several transition metal cations have been determined and compared in a H₂O-CH₂Cl₂-H₂O liquid membrane system using four water-insoluble macrocycles containing a dialkylhydrogenphosphate moiety. Transport of alkali metal cations by these ligands was greatest from a source phase pH = 12 or above into an acid receiving phase (pH = 1.5). Very low fluxes were observed for the transport of the alkaline earth cations and all transition metal ions studied except Ag⁺ and Pb²⁺ which were transported reasonably well by these new macrocycles.Deceased: September 5, 1987.     

Binding mechanisms of nano-baskets toward alkali metals

Thirty-four nano-basket derivatives of di-ionizable calix[4]arene conformers in nine scaffolds bearing two pendant groups of N-(R)-sulfonyl carboxamides were synthesized and examined using isothermal titration calorimetry. The binding mechanisms of synthesized conformers toward alkali metal cations were evaluated and two main interactions were assessed including cation?C?? interaction between alkali metal and the aromatic unit of conformer as well as the strong binding ion?Cdipole interaction between nitrogen atoms in the pendant groups and alkali cation. The ITC data revealed that the bindings of cone and partial-cone conformers toward alkali metal cations exhibited one-step mechanism, while both 1,2 alternate conformer bounds the alkali metal cations in a two-step mechanism.     

Solvent Extraction of Alkali Metal Picrates by Lipophilic Cyclodextrin Derivatives

Lipophilic cyclodextrin (CD) derivatives were prepared to extract alkali metal cations from a water phase into an organic phase. The extraction equilibrium constant, K ex, was determined by the solvent extraction method using UV absorption spectroscopy. Hydroxyl groups at the carbons in the 2,6-positions of CD molecules were dipropylated to add the hydrophobicity for dissolving into organic solvents, and furthermore hydroxyl groups at the carbons in the 3-position of these derivatives were acylated as complexing sites with the alkali metal cations. These CD derivatives formed a 1 : 1 complex with alkali metal cations, except for the case of Li+, and transported the alkali metal cations from a water phase into a benzene phase. The initial concentrations of alkali metal cation and picrate anion in the water phase and that of the CD derivatives in the organic phase strongly influenced the extraction equilibrium. Extraction of the alkali metal cation by the derivative without acyl groups was not detected. K ex values of these CD derivatives are of the same order of magnitude as or larger than those of crown ethers. The order of the K ex values in all cases is Li+ < Na+ < K+ Rb+ Cs+, although these CD derivatives have no special selectivity for the alkali metal cations. The cation extraction mechanism was interpreted by an induced-fit mechanism.     

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes

A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.     

Chemical modification of the surface of a sulfonated membrane by formation of a sulfonamide bond

This paper describes a novel approach for the surface modification of a cation-exchange membrane, bearing sulfonate groups, by a cationic layer. The modification procedure involved the chlorosulfonation of the sulfonate groups of the base membrane with thionyl chloride, followed by a reaction with a diamine to yield a sulfonamide bond and a terminal amine. The latter could be quaternized by reaction with methyl iodide or protonated by soaking in acidic media. The membranes were characterized in detail by attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies as well as elemental analysis to confirm that the above reactions occurred. The selectivity of these membranes toward the electrochemically assisted transport of protons versus Zn2+ metallic cations was determined during an electrodialysis in a two-compartment electrochemical cell. The data indicate a significant decrease of the transport of the metallic cations following modification of the membrane with the cationic layer. The later allows for the transport of protons from the catholyte to the anolyte compartment with much improved selectivity since the divalent cations are excluded from the membrane due to the electrostatic barrier of the cationic layer.     

Proton-ionizable crown compounds. 12. Proton-Coupled selective membrane transport of Li+ using a proton-ionizable pyridono macrocycle

The macrocycle-mediated fluxes of several alkali metal cations have been determined in a H₂O-CH₂Cl₂-H₂O liquid membrane system. Water-insoluble proton-ionizable macrocycles of the pyridono type were used. The proton-ionizable feature allows the coupling of cation transport to reverse H⁺ transport. This feature offers promise for the effective separation and/or concentration of alkali metal ions with the metal transport being driven by a pH gradient. A counter anion in the source phase is not co-transported. The desired separation of a particular metal ion involves its selective complexation with the macrocycle, subsequent extraction from the aqueous phase to the organic phase, and exchange for H⁺ at the organic phase-receiving phase interface. Factors affecting transport which were studied include ring size, source phase pH, and receiving phase pH. Lithium was transported at a rate higher than that of the other alkali metals in both single and competitive systems using a 15-crown-5 pyridono carrier.     

Effect of ion-exchanged alkali metal cations on the photolysis of 2-pentanone included within ZSM-5 zeolite cavities: a study of ab initio molecular orbital calculations

The Norrish Type I and Type II reactions in the photolysis of 2-pentanone included within the alkali metal cation-exchanged ZSM-5 zeolite have been investigated by experimental and theoretical approaches. Changes in the molecular environment of the zeolite cavities by exchanging the cations had significant effects not only on the adsorption state but also on the photochemical reactions of the ketones included within the zeolite cavities. The yields of the photolysis decreased and the ratio of the Type I/Type II reactions increased, respectively, by changing the ion-exchanged cations from Cs⁺ to Li⁺. The observed IR and phosphorescence spectra of the adsorbed ketones and the ab initio molecular orbital calculations of this host-guest system indicate that the ketones interact with two different adsorption sites, i.e. the surface OH groups and alkali metal cations, while the interaction between the ketones and cations increased by changing the cations from Cs⁺ to Li⁺. Molecular orbital calculations were also carried out and indicated that the zeolite framework promotes the delocalization of the charge density of the alkali metal cations which can modify the interaction between the adsorbed ketones and cations, resulting in significant changes in the photolysis of these ketones.     

Cation binding properties of photodimerizable polymers bearing benzodiglyme units

The polymers which have glyme units as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the radical polymerization of corresponding monomers. The alkali cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were strongly dependent on the length of glyme chains. When irradiated with ultraviolet light, the cinnamoyl groups caused dimerization in dilute solutions. Although the photodimerization of the polymers with relatively short glyme chains enhanced their cation binding ability, the photodimerization of the polymers bearing long glyme chains reduced their cation binding ability. The use of alkali metal cations as templates emphasized the effect of photodimerization on the cation binding properties. The effect of alkali metal cations on the quantum yields of the photodimerization of the polymers showed that two or more benzodiglyme units took part in the binding of one cation. The polymers bearing benzodiglymes, crown ethers, and cinnamoyl moieties were also prepared by the radical copolymerization of the corresponding monomers. It was found that the crown ether units of the copolymers predominantly participated in the cation binding. The photodimerization of the copolymers with suitable alkali metal cations as templates strongly enhanced their cation binding ability.     

Pseudo cyclic ionophores: ‘Binary-effect’ of quinolinyloxy groups at both ends of oligoethylene glycols on the conformational stabilization of their complexes with alkali metal salts

A series of noncyclic neutral ionophores has been synthesized by the reaction of oligoethylene glycol dihalides with 8-quinolinol. Complexation properties for alkali metal picrates were evaluated from solvent extraction and bulk liquid membrane transport experiments. Complexation profiles of the newly synthesized ionophores with a hexyl chain were similar to those of their homologues without the hexyl chain in the extraction experiments. Among them, the pentaethylene glycol derivatives showed the highest extraction efficiency and selectivity towards potassium ion. From the¹H NMR spectra (400 MHz), the change in chemical shifts of the aromatic protons upon the addition of alkali metal thiocyanates suggested the existence of a stabilization effect which is caused by intramolecular stacking conformations between the quinoline rings during complexation. Aryl stacking interactions depend on the size of the cations and on the chain length of the oligoethylene glycol. The relationship between transport ability towards alkali metal cations and lipophilicity of these ionophores is also discussed.     

Binding and Ionophoric Properties of Polythioamide Compounds. Ag(I) and Hg(II) Selectivities

The synthesis of tetrathiolactams and related di- and tetrathioamide compounds is described. The formation constants of their heavy-metal complexes are determined by using the strong UV absorption of the thioamide chromophore. Extraction and transport abilities of tetrathioamide ionophores show selectivities for Ag(I) and Hg(II) cations over alkali, alkaline-earth or other heavy metal cations including transition metals such as Co(II).     

The synthesis and coordination properties of new macrocyclic polyethers

A new type of macrocyclic polyethers has been synthesized. It consists of an azacrown ether as mother ring, e.g. 1,7-dioxa-4,10-diaza-cyclododecane (1a) or 1,7,10,16-tetraoxa-4,13-diazacycloocatadecane (1b), and two side chains attached on the two nitrogen atoms of 1a or 1b. A number of these new crown ethers are obtained by alkylation of the two secondary amino groups of 1a or 1b with corresponding halides, BrCH₂(CH₂OCH₂)_nCH₂OR, in the presence of potassium carbonate. The crown-alkali metal complex thus obtained is hydrolyzed by acid. In order to obtain pure crown ether the reaction mixture is treated with tetramethylammonium hydroxide and followed by solvent extraction. The ability of complexing alkali cations of macrocyclic polyethers in terms of the equilibrium constant have been studied by the method of solubilities of salts in chloroform. It is shown that the size of the mother ring, the number of oxygen atoms either in the ring or in the side-chains, and the ionic radius of the alkali metal are the factors governing the stability of the metal complexes. Most of these new crown ethers possess high ability for alkali metal complexation some of them, such as N,N′- di-β-methoxyethyl-1,7-dioxa-4,10-diaza-cyclododecanc (13a), possesses higher selectivity for Na+ and K+ ions than 18-crown-6- and 4,4′(5′)-dimethylbenz-30-crown-10.     

Two-component polymer films of palladium and fullerene with covalently linked crown ether voids: effect of cation binding on the redox behavior

Redox active films have been generated via electrochemical reduction in a solution containing palladium(II) acetate and fulleropyrrolidine with covalently linked crown ethers, viz., benzo-15-crown-5 and benzo-18-crown-6. In these films, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. Films show ability to coordinate alkali metal cations from the solution. Therefore, in solutions containing salts of alkali metal cations, benzo-15-crown-5-C₆₀/Pd and benzo-18-crown-6-C₆₀/Pd films are doped with cations coordinated by crown ether moiety and anions of supporting electrolyte which enter the film to balance positive charge. These films are electrochemically active in the negative potential range due to the reduction of the fullerene moiety. Reduction of the polymer is accompanied by the transport of supporting electrolyte ions between solution and solid phase. In solution containing alkali metal salts, the process of film reduction is accompanied by the transport of anions from the film to the solution. In the presence of tetra(alkyl)ammonium salts, transport of cations from the solution to the film takes place during the polymer reduction.     

Proton-ionizable crown compounds. 13. Synthesis and structural studies of crown compounds containing the triazole subcyclic unit and lipophilic substituents

Eight new macrocyclic polyether ligands containing the proton-ionizable triazole subcyclic unit have been prepared. Most of these compounds contain octyl, benzo or cyclohexano lipophilic groups. The unsubstituted triazolo-18-crown-6 ( 5 ) formed an unusual complex with silver ion. The crystal structure of this silver complex showed one crown complexed with one silver cation and two associated silver nitrate molecules. The new lipophilic triazolo-crowns are being tested as cation carriers for alkali and other metal cations in a bulk liquid membrane system.     

Synthesis and complexing properties of bis-crown ethers incorporating benzo-15-crown-5 and metallocene

Bis-crown ethers in which the benzo-15-crown-5 units were linked to 1,1′-positions of metallocene (M = Fe or Ru) with amide, ester, or ? C? C? bonds were synthesized. Complexing ability of the compounds with alkali, alkali earth, and transition metal cations were measured by the solvent extraction method. The results showed that these crown ethers had high affinity toward alkali metal cations (Li⁺, Na⁺, K⁺, and Rb⁺) and heavy-metal cations (Ag⁺ and Tl⁺). The difference of complexing ability for metal cations between ferrocene and ruthenocene derivatives could not be detected significantly. The extractability of metallocene-bis-crown ethers for metal cations was more larger than that of the corresponding mono-crown ethers, and irregular increments of extractability were explained by assuming the existence of a mixture of 1:1 and 2:1 complexes.     

Cation-directed synthesis of tungstosilicates. 1. Syntheses and structures of K10A-alpha-[SiW9O34].24H2O,of the sandwich-type complex K10.75[Co(H2O)6]0.5[Co(H2O)4Cl]0.25A-alpha-[K2(Co(H2O)2)3(SiW9O34)2].32H2O and of Cs15[K(SiW11O39)2].39H2O

The influence of the nature of alkali metal cations on the structure of the species obtained from the trivacant precursor A-alpha-[SiW(9)O(34)](10-) has been studied. Starting from the potassium salt 1, K(10)A-alpha-[SiW(9)O(34)].24H(2)O, the sandwich-type complex 2, K(10.75)[Co(H(2)O)(6)](0.5)[Co(H(2)O)(4)Cl](0.25)A-alpha-[K(2)(Co(H(2)O)(2))(3)(SiW(9)O(34) )(2)].32H(2)O, has been obtained. The crystal structures of these two compounds consist of two A-alpha-[SiW(9)O(34)](10-) anions linked by a set of potassium (1) or cobalt plus potassium cations (2), and the relative orientation of the two half-anions is the same. Attempts to link two A-alpha-[SiW(9)O(34)](10-) anions by tungsten atoms instead of cobalt failed whatever the alkali metal cation. Moreover, the nondisordered structure of Cs(15)[K(SiW(11)O(39))(2)].39H(2)O is described. Two [SiW(11)O(39)](8-) anions are linked through a potassium cation with a "trans-oid" conformation, and the potassium occupies a cubic coordination site.     

Infrared spectrum of the hyponitrite dianion, N(2)O(2)2-, isolated and insulated from stabilizing metal cations in solid argon.

Ultraviolet irradiation of a rigid 7 K argon matrix containing alkali or alkaline earth metal atoms and NO(2) isolated from each other by one or two layers of argon forms N(2)O(2)2-dianions insulated from two M(+) cations by argon atoms, and visible photolysis reverses this electron-transfer process likely involving the N(2)O(2)(-) anion intermediate. The isolated N(2)O(2)2- dianion is identified from isotopic substitution and isotopic mixtures, which show that the new 1028.5 cm(-1) metal independent absorption involves two equivalent NO subunits. DFT calculations predict a strong 1078.1 cm(-1) fundamental for the Li(NO)(2)Li molecule and isotopic frequency ratios in excellent agreement with the observed values, which provides a model for the matrix dianion system. The spectrum of solid Na(2)N(2)O(2) exhibits a 1030 cm(-1) infrared band, which strongly supports the present N(2)O(2)2- dianion assignment. The electrostatic stabilization of N(2)O(2)2-, which is probably unstable in the gas phase, is made possible by metal cations separated by one or two insulating layers of argon in the rigid 7 K matrix.     

Thermodynamic quantities of surface formation of aqueous electrolyte solutions X. Aqueous solution of 2:1 valence-type salts

The behaviors of a series of calcium halides and of alkali earth metal chlorides in the air/water surface region were studied in comparison with those of alkali metal halides by measuring the surface tension increments of solutions. The effect of salts with divalent cations on the surface tension increments is more pronounced than that of uni-univalent salts, but there are some similarities between these two types. It seems that the anions cause a marked effect on surface tension which is proportional to the magnitude of hydration in the bulk water. We also observed a decrease in the entropy change of surface formation with increasing concentration. The importance of an electrical double layer at the surface is discussed in relation to these surface tension increments.     

Alkali cation binding of polymers with different sized crown ethers and photodimerizable units

The polymers which have different sized crown ethers as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the cationic copolymerization of corresponding monomers. The crown–cation complexation ratio (1:1 or 2:1) was investigated by measuring quantum yields ? of the photodimerization of the crown-connected cinnamoyl units in the presence of alkali metal chlorides and also by measuring the shift of λ_max of alkali metal picrates in THF on addition of the crown polymers. A significant 1:2 complex formation of alkali cations with two different sized crown ether units in the side chain of the polymers was confirmed. The alkali metal cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were markedly different from those expected from the combination of polymers of same ring-size crown ether units. When irradiated with ultraviolet (UV) light, the cinnamic acid ester groups of the polymers caused dimerization even in dilute solutions. The cation binding ability of the polymers was largely enhanced by the photodimerization of the cinnamoyl moieties with suitable template cations.