Extraction Of Alkali Metal Cations Research Articles

Alkali metal cation complexation by 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds

Alkali metal cation extraction behaviour for two series of 1,3-alternate, mono-ionisable calix[4]arene-benzocrown-6 compounds is examined. In Series 1, the proton-ionisable group (PIG) is a substituent on the benzo group of the polyether ring that directs it away from the crown ether cavity. In Series 2, the PIG is attached to one para position in the calixarene framework, thereby positioning it over the crown ether ring. Competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform shows high Cs+ efficiency and selectivity. Single-species extraction pH profiles of Cs+ for Series 1 and 2 ligands with the same PIG are very similar. Thus, association of Cs+ with the calixcrown ring is more important than the position of the PIG relative to the crown ether cavity. Solid-state structures of two unionised ligands from Series 2 are presented. Also described is a crystal containing two different ionised ligand–Cs+ complexes.

Nano-baskets of Calix[4]-1,3-crown in Emulsion Membranes for Selective Extraction of Alkali Metal Cations

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of diacid calix[4]-1,3-crowns-4,5 were synthesized, and their inclusion-extraction parameters were optimized including the calixcrown scaffold (4.4%, by mass) as the carrier/demulsifier, the commercial kerosene as diluent in membrane, sulphonic acid (0.2 mol·L−1) and ammonium carbonate (0.4 mol·L−1) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300 r·min7minus;1), and initial solute concentration (100 mg·L−1). The selectivity of membrane over more than ten interfering cations was examined and the results reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98%-99%.

Inclusion desalination of alkali metal cations by emulsion liquid membranes and nano-baskets of p-tert-calix[4]arene bearing di-[N-(X)sulfonyl carboxamide] and di-(1-propoxy) in para-cone conformation

Nano-assisted inclusion separation of alkali metal cations from basic aqueous solutions was reported by inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixarene in the selective and efficient separation of alkali metal cations as both the carrier and the surfactant. For this aim, four derivatives of p-tert-calix[4]arene bearing different sulfonamide moieties were synthesized and their inclusion–extraction parameters were optimized including the calixarene scaffold 3 (4wt.%) as the carrier/demulsifier, the commercial kerosene as diluent in membrane, sulphonic acid (0.2M) and ammonium carbonate (0.4M) as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed (300rpm), and initial solute concentration (100mg/L). The selectivity of membrane over more than ten interfering cations was examined and the results revealed that under the optimized operating condition, the degree of inclusion–extraction of alkali metal cations was as high as 98–99%.

Sterically congested, geminal aryl-substituted, proton-ionizable sym-dibenzo-16-crown-5 lariat ethers: synthesis and alkali metal cation extraction

Three series of proton-ionizable sym-dibenzo-16-crown-5 ethers with sterically demanding 1- naphthyl, 2-naphthyl, and 9-phenanthryl geminal groups are synthesized and characterized. Variation of the proton-ionizable group includes oxyacetic acid and N-(X)sulfonyl oxyacetamide units with X = Me, Ph, C6H4-4-NO2, and CF3. For the latter series, variation of X provides 'tunable' acidity of the ligand. The metal ion-complexing properties of the proton-ionizable sym- (aryl)dibenzo-16-crown-5 compounds are probed by competitive solvent extraction of alkali metal cations from aqueous solutions into chloroform.

Liquid–Liquid Extraction of Alkali Metal Cations by Calix[4]crowns with Pendant Groups

The selective liquid–liquid extraction of alkali metal cations from the aqueous phase to the organic phase was carried out by using calix[4]crowns bearing two pendant groups with donor sites. It was found that calix[4]crown‐4 and calix[4]crown‐5 extractants with two pendant groups exhibit higher extraction efficiency than the parent compounds and possess obvious selectivity for Na+ and K+, respectively.

Ion Extraction of Alkali Metal Cations by a Calix[4]arene Bearing Two Ester Groups

Ion Extraction of Alkali Metal Cations by a Calix[4]arene Bearing Two Ester Groups

New mono-ionizable, Li+-selective calix[4]arenes

A series of new mono-ionizable cone calix[4]arenes, with either a pendent carboxylic acid or a N-(X-sulfonyl)carboxamide group, is synthesized and their alkali metal cation extraction behavior determined and compared with that for conformationally mobile analogues. These new proton-ionizable, cone calixarenes exhibit good (for the sulfonylcarboxamides) to excellent (for the carboxylic acid) Li+-selectivity. Surprisingly, the Li+-selectivity decreases on going from the conformationally flexible to the cone ionophores due to enhanced Na+ binding by the latter. During the ligand synthesis, unusual behavior of cone tributoxy-N-(trifluoromethylsulfonyl)carbamoylmethoxy-p-tert-butylcalix[4]arene suggests a strong tendency for molecular association.

Effect of structural variation within lipophilic N-(X)sulfonyl carbamoyl lariat ethers on the selectivity and efficiency of competitive alkali metal cation extraction into chloroform.

Sixteen lipophilic N-(X)sulfonyl carbamoyl lariat ethers with polyether ring sizes of 12-crown-4, 14-crown-4, 15-crown-5, and 18-crown-6 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Variation of the electron-withdrawing properties of X in the series of methyl, phenyl, 4-nitrophenyl, and trifluoromethyl allows the influence of the acidity of the C(O)NHSO2X group in the side arm upon extraction efficiency and selectivity to be assessed. With X = trifluoromethyl, effective alkali metal cation extractions from acidic, neutral, and basic aqueous solutions are achieved. When the crown ether rings are 14-crown-4, 15-crown-5, and 18-crown-6, selectivities for Li+, Na+, and K+, respectively, are observed. Results are compared with those reported for analogous lariat ether carboxylic acids and phosphonic acid monoethyl esters.

Novel caesium-selective, 1,3-alternate calix[4]arene-bis(crown-6-ethers) with proton-ionizable groups for enhanced extraction efficiencyElectronic supplementary information (ESI) available: HSQC spectra for Na+ and Cs+ complexes of ionized 7, and graphs for Cs+ extraction. See http://www.rsc.org/suppdata/p2/b1/b109638a/

Synthesis of a series of novel 1,3-alternate calix[4]arene-bis(crown-6-ethers) with a proton-ionizable group (PIG) located in front of one crown ether cavity is reported. Variation of the X group in the N-(X-sulfonyl)carbamoyl substituent on the calixbiscrowns provides variation of acidity of the PIG. NMR spectroscopic studies demonstrate that the position of the PIG within the molecule allows it to participate in cooperative metal ion coordination by the ligand. In solvent extraction of alkali metal cations from aqueous solutions of varying pH into chloroform, the novel ionophores possess enhanced efficiency relative to a non-ionizable analog, while retaining high Cs+ selectivity. The Cs+ extraction constants of the proton-ionizable calixbiscrowns are proportional to their acidities. Under the conditions employed, 1 ∶ 1 complexes of the ionized calixbiscrowns with Cs+ are the dominant species extracted into the organic phase.

Chromogenic lariat ethers for selective alkali metal cation recognition.

Twelve new proton-ionizable, picrylamino-type chromogenic lariat ethers derived from dibenzo-14-crown-4, dibenzo-16-crown-5 and dibenzo-19-crown-6 demonstrate good selectivity and remarkable color response upon extraction of alkali metal cations from basic aqueous solutions into chloroform.

Influence of structural variation in room-temperature ionic liquids on the selectivity and efficiency of competitive alkali metal salt extraction by a crown ether.

An improved method for the preparation of 1-alkyl-3-methylimidazolium hexafluorophosphates provides a series of room-temperature ionic liquids (RTILs) in which the 1-alkyl group is varied systematically from butyl to nonyl. For competitive solvent extraction of aqueous solutions of alkali metal chlorides with solutions of dicyclohexano-18-crown-6 (DC18C6) in these RTILs, the extraction efficiency generally diminished as the length of the 1-alkyl group was increased. Under the same conditions, extraction of alkali metal chlorides into solutions of DC18C6 in chloroform, nitrobenzene, and 1-octanol was undetectable. The extraction selectivity order for DC18C6 in the RTILs was K+ > Rb+ > Cs+ > Na+ > Li+. As the alkyl group in the RTIL was elongated, the K+/ Rb+ and K+/Cs+ selectivities exhibited general increases with the larger enhancement for the latter. For DC18C6 in 1-octyl-3-methylimidazolium hexafluorophosphate, the alkali metal cation extraction selectivity and efficiency were unaffected by variation of the aqueous-phase anion from chloride to nitrate to sulfate.

ChemInform Abstract: New Lipophilic Crown Ethers with Intraannular Carboxylic Acid Groups: Synthesis and Alkali Metal Cation Extraction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Design, synthesis and cation-binding properties of novel adamantane- and 2-oxaadamantane-containing crown ethers

The synthesis of a series of adamantane- and 2-oxaadamantane-functionalized crown ethers 1– 7 is described. Alkali metal picrate extraction profiles have been determined for these novel ionophores. The ability of crown ethers 1– 7 to extract the alkali metal picrates was compared with that of benzo-15-crown-5 and 18-crown-6. Also, Na +- and K +-transport, the ability of ionophores l– 3 to transport Na +- and K + across a bulk liquid membrane was measured. The results of alkali metal cation extraction experiments showed that the complexation properties of crown ethers 1 and 2 are comparable to that of benzo-15-crown-5 and 18-crown-6, respectively. Crown ether 3 showed enhanced extractability for all cations but lower selectivity compared to 18-crown-6. However, adamantano-crown ethers 4– 7 showed almost negligible extraction capability toward any of the alkali cations. The observed differences among the complexation abilities of the ionophores 1– 3 and 4– 7 are rationalized on the basis of the results of a molecular modeling study of their corresponding K + complexes.

New lipophilic crown ethers with intraannular carboxylic acid groups: Synthesis and alkali metal cation extraction

A six-step synthetic route to four lipophilic crown ethers with intraannular carboxylic acid groups and ring sizes of 15-crown-4, 18-crown-5, 21-crown-6 and 24-crown-7 is described. Eight new polyether compounds that bear inward-facing bromo and formate ester substituents are prepared as synthetic intermediates. Selectivities and efficiencies of the four new lipophilic crown ether carboxylic acids in competitive alkali metal cation extraction from aqueous solutions into chloroform are evaluated.

Effect of Structural Variation within Lipophilic Lariat Ether Phosphonic Acid Monoesters on the Selectivity and Efficiency of Competitive Alkali Metal Cation Extraction into Chloroform

Lipophilic lariat ether phosphonic acid monoethyl esters with systematic crown ether ring size variation from 12-crown-4 to 24-crown-8 are utilized for competitive alkali metal cation extractions from aqueous solutions into chloroform. Effective alkali metal cation extraction from weakly acidic, neutral, and basic aqueous solutions is achieved. With 4, 5, and 6 oxygens in the crown ether rings, selectivities for Li(+), Na(+), and K(+), respectively, are observed. An 18-crown-6 phosphonic acid monoester exhibits excellent extraction selectivity for K(+) with K(+)/Li(+) and K(+)/Na(+) > 100. The lipophilic group attachment site, as well as the crown ether ring size, is shown to influence the extraction selectivity for the lariat ether phosphonic monoesters.

Metal ion extraction by lariat ethers with ‘tunable’ proton-ionizable groups

Abstract

Lariat ethers with a novel proton-ionizable group. Synthesis and solvent extraction of alkali metal cations

V. J. Huber, S. N. Ivy, J. Lu and R. A. Bartsch, Chem. Commun., 1997, 1499 DOI: 10.1039/A703106H

1,3‐Alternate Calix[4]arenecrown‐5 Conformers: New Synthetic Ionophores with Better K+/Na+ Selectivity than Valinomycin

AbstractNew 25,27‐dialkoxycalix‐[4]arenecrown‐5 conformers 8, 10, and 11 have been synthesized and studied. The compounds 8a and 8b, fixed in 1,3‐alternate structure, have been obtained in 57 and 40% yield, respectively, by reaction of the corresponding 25,27‐dialkoxycalix[4]arenes 7a–b with tetraethylene glycol di‐p‐toluenesulfonate in the presence of Cs2CO3. The cone 10a and 10b and the partial cone 11 conformers were obtained by selective demethylation of the 25,27‐dimethoxycalix[4]arenecrown‐5 (6a) and subsequent dialkylation with NaH/DMF and KOtBu/THF, respectively. In the solid state (X‐ray), compound 6a adopts a flattened cone conformation, which is also found to be most abundant in CD3CN and CD3OD solution. Upon complexation with potassium picrate compound 6a was converted quantitatively into the 1,3‐alternate conformation. All new ligands synthesized were used in the extraction of alkali metal cations from H2O into CHCl3, and as active components in supported liquid membranes and in chemically modified field effect transistors. Results were compared to those obtained with with the natural antibiotic valinomycin 1. All ligands showed high selectivity for potassium. Ligand 8a, fixed in the 1,3‐alternate conformation, is more selective than valinomycin and shows the highest K+/Na+ selectivity known so far.

Extraction of Alkali Metal Cations by Lipophilic Dibenzo-14-crown-4-carboxylic Acids

Abstract The extraction of alkali metal cations by the lipophilic crown ether, bis-t-octylbenzo-14-crown-4 (BOB14C4), three derivatives of BOB14C4 having pendant carboxylic acid sidearms, and a lipophilic carboxylic acid, 2-methyl-2-heptylnonanoic acid (HMHN) was studied by two-phase potentiometric titration and ion-chromatography. The lipophilic, ionizable crown ethers, BOB14C4-acetic acid (BOB14C4AA), BOB14C4-propanoic acid (BOB14C4PA), and BOB14C4-oxyacetic acid (BOB14C4OAA) extract cations efficiently from aqueous mixed alkali metal chloride solutions into 1-octanol by an ion-exchange mechanism in the range p[H] > 7, as does HMHN. The mode of attachment of the ionizable sidearm, via an ether linkage (BOB14C4OAA) versus a carbon linkage (BOB14C4AA and BOB14C4PA), has a significant effect on the cation selectivity and extraction efficiency of these extractants. BOB14C4 exhibits no p[H] dependent extraction behavior and has no significant effect on the extraction of alkali metal cations by HMHN in a mixture of these two compounds. Although BOB14C4AA and BOB14C4PA extract cations at lower p[H] than HMHN, all three compounds exhibit similar selectivity for Li+ over Na+, K+, Rb+ and Cs+. A significant reversal in selectivity is observed with BOB14C4OAA, which extracts Na+ and K+ selectively over Li+, Rb+, and Cs+ and at significanty lower p[H] than BOB14C4AA, BOB14C4PA, or HMHN. The unique behavior of BOB14C4OAA may be attributed to the presence of the ether linkage between the crown ether and the pendant carboxylic acid.

Synthesis of photoresponsive crown ethers having a phosphoric acid functional group as anionic cap and their selective complexing abilities toward alkali metal cations

New photoresponsive crown ethers (3a, 3b and 3c) connected to ionizable phosphoric acid moieties by an azobenzene skeleton have been synthesized. The trans isomers are isomerized to the cis isomers by UV irradiation and the cis isomers are reversibly thermally isomerized to the trans isomers. The complexing abilities of these compounds have been estimated by measuring the cis to trans thermal isomerization rate in the presence of various alkali metals and tetramethylammonium ions and by the competitive extraction of alkali metal cations. The first-order rate constant for the thermal isomerization of cis-3a to trans-3a is remarkably suppressed in the presence of Na+ and the extraction ability of cis-3a for Na+ was greatly enhanced. In contrast, the recovery of trans-3c from cis-3c was significantly suppressed by Li+ and the extraction of Li+ by cis-3c was greatly and selectively enhanced.