Ion formation in fast atom bombardment mass spectrometry: a divided probe investigation of gas-phase reactions

Some ion-formation processes during fast atom bombardment (FAB) are discussed, especially the possibility of reactions in the gas phase. Divided (two halves) FAB probe tips were used for introducing two different samples into the source at the same time. Our results showed [M + A]⁺ ions (where M = crown ethers and A = alkali metal ions), can be produced, at least in part, in the gas phase when crown ethers and sources of alkali metal ion are placed on two halves of the FAB probe tip. The extent of this ion formation depends on the volatility of the crown ether and on steric factors. Cluster ions such as (M + LiCl)Li⁺, (2M + LiCl)Li⁺, [2M + K]⁺ and [2M + Na]⁺ are also observed to form in the gas phase. Unimolecular decompositions contribute to some ions detected in FAB. When the alkali ion salt and the crown ether are mixed together the probability of [M + A]⁺ ion formation increases significantly, regardless of the volatility of the crown ether.     

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.     

Synthesis and Complexing Properties of <Emphasis Type="Italic">N,N</Emphasis>′-Bis(2-hydroxyethyl) Diaza Crown Ethers

The stability constants of complexes of 12-, 15-, and 18-membered diaza crown ethers, N,N′-dimethyl diaza crown ethers, and N,N′-bis(2-hydroxyethyl) diaza crown ethers with alkali and alkaline-earth metal ions in 95% aqueous methanol at 25°C were determined. The stability of the complexes of unsubstituted diaza crown ethers with alkali metal cations is low, probably because of stabilization of the exo,exo conformation of the ligands due to interaction of the nitrogen lone electron pairs with the solvent. The complexes with the double-charged cations are appreciably more stable. N,N′-Dimethyl diaza crown ethers form stable complexes with all the ions studied. As compared to the dimethyl derivatives, N,N′-bis(2-hydroxyethyl) diaza crown ethers form more stable complexes with the Na⁺, K⁺, Ca²⁺, Sr²⁺, and Ba²⁺ ions, which is due to participation of the side hydroxyethyl groups in the coordination.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 665–669.Original Russian Text Copyright © 2005 by Kulygina, Vetrogon, Basok, Luk’yanenko.     

Determination of orders of relative alkali metal ion affinities of crown ethers and acyclic analogs by the kinetic method

Ladders of relative alkali ion affinities of crown ethers and acyclic analogs were constructed by using the kinetic method. The adducts consisting of two different ethers bound by an alkali metal ion, (M₁ + Cat + M₂)⁺, were formed by using fast atom bombardment ionization to desorb the crown ethers and alkali metal ions, then collisionally activated to induce dissociation to (M₁ + Cat)⁺ and (M₂ + Cat)⁺ ions. Based on the relative abundances of the cationized ethers formed, orders of relative alkali ion affinities were assigned. The crown ethers showed higher affinities for specific sizes of metal ions, and this was attributed in part to the optimal spatial fit concept. Size selectivities were more pronounced for the smaller alkali metal ions such as Li⁺, Na⁺, and K⁺ than the larger ions such as Cs⁺ and Rb⁺. In general, the cyclic ethers exhibited greater alkali metal ion affinities than the corresponding acyclic analogs, although these effects were less dramatic as the size of the alkali metal ion increased.     

冠醚聚合物的研究 Ⅱ.以聚硫醚为主链的硫杂冠醚聚合物的合成及其络合性能

 本文报道了一种合成硫杂冠醚聚合物的新方法。以聚(2′-氯乙基-2,3-环硫丙基醚)为预聚物与二巯基化合物通过大分子反应直接环化,一步法合成了四种以聚硫醚为主链的新型硫杂冠醚聚合物(PD1-PD4)。并测定了它们对Ag⁺、Au³⁺)、Pd²⁺、Pt⁴⁺、Cu²⁺、Hg²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Mg²⁺、K⁺、Ns⁺等金属离子的络合性能。结果表明:它们除不络合K⁺、Na⁺、Mg²⁺、Pb²⁺外,对其它八种离子有不同程度的络合,其中对Ag⁺、Au³⁺、Pd²⁺等贵金属离子的络合容量较高。     

Cation exchange properties of crown ether-phosphotungstic acid precipitates

Precipitate formation between phosphotungstic acid and crown ethers is a general phenomenon, producing solids with selective ion exchange behavior for the alkali metal ions. Distribution coefficients for Li⁺, Na⁺, K⁺, and Cs⁺ were measured for a series of these precipitates with different crown ethers. The sorption data are more complicated than for the corresponding phosphomolybdates and indicate a variability in the number of exchangeable sites with H⁺ and M⁺ concentration. The crown ether used markedly affects the cation selectivity of the phosphotungstate precipitates.     

Fine‐tuning of electromembrane extraction selectivity using 18‐crown‐6 ethers as supported liquid membrane modifiers

Selectivity of electromembrane extractions (EMEs) was fine‐tuned by modifications of supported liquid membrane (SLM) composition using additions of various 18‐crown‐6 ethers into 1‐ethyl‐2‐nitrobenzene. Gradually increased transfer of K⁺, the cation that perfectly fits the cavity of 18‐crown‐6 ethers, was observed for EMEs across SLMs modified with increasing concentrations of 18‐crown‐6 ethers. A SLM containing 1% w/v of dibenzo‐18‐crown‐6 in 1‐ethyl‐2‐nitrobenzene exhibited excellent selectivity for EMEs of K⁺. The established host–guest interactions between crown ether cavities in the SLM and potassium ions in donor solution ensured their almost exhaustive transfer into acceptor solution (extraction recovery ～92%) within 30 min of EME at 50 V. Other inorganic cations were not transferred across the SLM (Ca²⁺ and Mg²⁺) or were transferred negligibly (NH₄⁺, Na⁺; extraction recovery < 2%) and had only subtle effect on EMEs of K⁺. The high selectivity of the tailor‐made SLM holds a great promise for future applications in EMEs since the range of similar selective modifiers is very broad and may be applied in various fields of analytical chemistry.     

Density Functional Theory Study of Selectivity of Crown Ethers to Li+ in Spent Lithium-Ion Batteries Leaching Solutions

It is a challenge to recover lithium from the leaching solution of spent lithium-ion batteries, and crown ethers are potential extractants due to their selectivity to alkali metal ions. The theoretical calculations for the selectivity of crown ethers with different structures to Li ions in aqueous solutions were carried out based on the density functional theory. The calculated results of geometries, binding energies, and thermodynamic parameters show that 15C5 has the strongest selectivity to Li ions in the three crown ethers of 12C4, 15C5, and 18C6. B15C5 has a smaller binding energy but more negative free energy than 15C5 when combined with Li⁺, leading to that the lithium ions in aqueous solutions will combine with B15C5 rather than 15C5. The exchange reactions between B15C5 and hydrated Li⁺, Co²⁺, and Ni²⁺ were analyzed and the results show that B15C5 is more likely to capture Li⁺ from the hydrated ions in an aqueous solution containing Li⁺, Co²⁺, and Ni²⁺. This study indicates that it is feasible to extract Li ions selectively using B15C5 as an extractant from the leaching solution of spent lithium-ion batteries.     

Selective reagents in chemical ionization mass spectrometry: Tetramethylsilane with ethers

Chemical ionization mass spectra of several ethers obtained with He/(CH₃)₄Si mixtures as the reagent gases contain abundant [M + 73]⁺ adduct ions which identify the relative molecular mass. For the di-n-alkyl ethers, these [M + 73]⁺ ions are formed by sample ion/sample molecule reactions of the fragment ions, [M + 73 ? C_nH_2n]⁺ and [M + 73 ? 2CnH_2n]⁺. Small amounts of [M + H]⁺ ions are also formed, predominantly by proton transfer reactions of the [M + 73 ? 2CnH_2n]⁺ or [(CH₃)₃SiOH₂]⁺ ions with the ethers. The di-s-alkyl ethers give no [M + 73] ⁺ ions, but do give [M + H]⁺ ions, which allow the determination of the relative molecular mass. These [M + H]⁺ ions result primarily from proton transfer reactions from the dominant fragment ion, [(CH₃)₃SiOH₂]⁺ with the ether. Methyl phenyl ether gives only [M + 73]⁺ adduct ions, by a bimolecular addition of the trimethylsilyl ion to the ether, not by the two-step process found for the di-n-alkyl ethers. Ethyl phenyl ether gives [M + 73]⁺ by both the two-step process and the bimolecular addition. Although the mass spectra of the alkyl etherr are temperature-dependent, the sensitivities of the di-alkyl ethers and ethyl phenyl ether are independent of temperature. However, the sensitivity for methyl phenyl ether decreases significantly with increasing temperature.     

Structural and Chemical Features of Extraction with Crown Ethers

Unlike linear extracting agents, in the extraction of metal salts from aqueous solutions of inorganic acids with crown ethers, the inclusion compounds, whose composition depends on several external and internal factors, go to the organic phase. The study of the molecular structure of the formed complexes by X-ray diffraction analysis showed that adducts of crown ethers with inorganic acids are host–guest complexes in which the hydroxonium ion is in the polyether macrocycle cavity. When the aqueous phase contains metal ions capable of displacing the hydroxonium ions from the macrocycle (K⁺, Pb²⁺, Hg²⁺, Sr²⁺, NH₄ ⁺), complexes containing metal cations as the guest in the macrocycle cavity, according to X-ray diffraction data, go to the organic phase. In addition, metals forming ionic associates (AuCl₄ ^-, FeCl₄ ^-, GaCl₄ ^-) in an aqueous solution are extracted with crown ethers in accordance with the anion-exchange mechanism. A system in which traces of metals in the 2 M HNO₃ +5 M HCl mixture serve as the aqueous phase was proposed for estimation of the general extraction ability of crown ethers. Such a system can be used for metal extraction via any possible mechanism. The stereochemical peculiarities of the extraction ability of crown ethers (compared to linear molecules) can be used for selective extraction and separation of metals.     

Cation-crown ether complex formation in water. II. Alkali and alkaline earth cations and 12-crown-4, 15-crown-5, and 18-crown-6

The stability constants and the partial molal volume and isentropic partial molal compressibility changes of complex formation between cations and crown ethers in water at 25°C are presented. The cations involved are Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, and Ba²⁺, and the crown ethers are 12-crown-4, 15-crown-5, and 18-crown-6. Values of V of complex formation have been discussed in terms of two simple models, one based on the scaled particle theory, and the others on the Drude-Nernst continuum model. The results indicate that the charge of the potassium cation in 18-crown-6 is especially well screened from the water. On this basis hydration numbers of complexed cations have been calculated. This shows that the size of the cation compared to the crown ether hole is important for the contacts between complexed cations and water.     

Study of Host-Guest Complexation of Alkaline Earth Metal Ion,Aluminum Ion and Transition Metal Ions with Crown Ethers by Fast Atom Bombardment Mass Spectrometry

Complexations of crown ethers with alkali metal ions have been investigated extensively by FAB mass spectrometry over the past decade, but very little attention has been paid to reactions of crown ethers with other classes of metal ions such as alkaline earth metal ions, transition metal ions and aluminum ions. Although fast atom bombardment ionization mass spectrometry has proven to be a rapid and convenient method to determine the binding interactions of crown ethers with metal ions, problems in reliabilities for quantitative measurements of” binding strength for the host-guest complexes have been described in the literature. Thus, in this paper, applications of FAB/MS for investigating the complexation of crown ethers with various classes of metal ions is discussed. Extensive fragmentations for neutral losses such as C₂H₄O or C₂H₄ molecules from the host-guest complexes could be observed. The reason is attributed to the energetic bombardment processes of FAB occuring in the formation of these complexes. Complexes of cyclen with metal ions also show neutral losses of C₂H₄NH molecules leading to fragment ions. Transition metal ions usually form (Crown + MCl)⁺ type of ions, alkaline earth metal ions can form both (Crown + MCl)⁺ and (Crown + MOH)⁺ type of ions. But for aluminum ions, only (Crown + Al(OH)₂)⁺ type of ions could he observed.     

Mass spectrometric investigation of the side-arm lariat effect of ortho- and para-methoxyphenoxymethyl-15-crown-5 in the gas phase

Mixtures of unsubstituted 15-crown-5 and its analogues containing ortho- and para-methoxyphenoxymethyl substituents with sodium salts were investigated by matrix assisted laser desorption/ionization (MALDI) mass spectrometry. Peaks of cationized molecules [M+Na]⁺ and cluster ions [2M+2Na+An]⁺, where M is the crown ether molecule and An is monobasic acid anion, were observed in the mass spectra. It was shown that an increase of the shielding degree of the sodium cation in complexes with crown ethers, i.e., the lariat effect, led to a significant decrease in the intensity of peaks of the cluster ions.     

Ion–molecule reactions between organometallic ions and crown ethers in the gas phase

Ion–molecule reactions of the metal-containing ions LM⁺ (L = (acac)₂, acac, C₆H₆, C₅H₅; M = In, Ga, Co, Fe, Ni, Cr, Mn, Pd, Rh, Tl, La, Pr, Yb, Nd) with crown ethers in the gas phase were studied. Two major reactions were observed: adduct formation and substitution of a metal atom ligand by a crown ether. The relative abundances of the two reactions depends on the ease with which the metal atom may be reduced. Ligand substitution can involve hydrogen rearrangements with loss of acetylacetone or cyclopentadiene for crown ethers having mobile H atom(s). The use of ion–molecule reactions in the structural characterization of crown ethers and transition metalcontaining ions is discussed.     

Synthesis and crystal structure of dinitroxyl crown ether biradical with indole groups in the side chains

Dinitroxyl crown ether biradical, 4,13-bis[2-hydroxy-3-(2,2,4,4-tetramethyl-3-oxylo1,2,3,4-tetrahydro-γ-carbol-9-yl)propyl]-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane, was synthesized and studied by X-ray structural analysis and ESR spectroscopy. The ESR spectra in aqueous and aqueous-alcoholic solutions show a triplet with ^a N = 1.65±0.05 mT. This triplet is retained in the presence of Na⁺, K⁺, and Mg²⁺ ions. On addition of Ca²⁺ ions, the triplet is transformed into the quintet because of the change in the conformation of the crown ether biradical and decrease in the distance between the nitroxyl groups. The new crown ether biradicdl containing hydrophobic indole groups may be used for studying the mechanism of Ca²⁺ ion transport in biomembranes by ESR spectroscopy.     

Imidazo-benzo-15-crown-5 ethers bearing arylthienyl and bithienyl moieties as novel fluorescent chemosensors for Pd and Cu

Novel fluorescent ionophores bearing imidazo-arylthienyl or imidazo-bithienyl π-conjugated bridges functionalized with one or two fused benzo-15-crown-5 ethers as receptor units are reported. The sensing ability of the compounds in the presence of metallic cations (Li⁺, Na⁺, K⁺, Ca²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Pd²⁺, and Hg²⁺) and fluoride ion was studied in MeCN/DMSO solutions by absorption and emission spectroscopy. The experimental results indicate that all compounds could act as selective fluorimetric sensors for Cu²⁺ and Pd²⁺ and also for the fluoride ion, in the case of the bis-substituted crown ether derivatives.     

Preparation and Application of Cholesteryl‐Benzo‐15‐Crown‐5/Cholesteryl Mixed Liquid Crystals

Various mixed liquid crystals containing crown ether‐cholesteryl liquid crystal, benzo‐15‐crown‐5‐COO‐C₂₇H₄₅ (B15C5‐COOCh), with various common cholesteric liquid crystals, e.g., cholesteryl chloride, cholesteryl benzoate and cholesteryl palmitate, were prepared and studied using polarizing microscopy and differential scanning calorimetry. Investigating the concentration effect of B15C5‐COOCh in mixed liquid crystals revealed that the addition of B15C5‐COOCh resulted in wider phase transition temperature ranges of these cholesteryl liquid crystals. The stability of these B15C5‐COOCh/cholesteryl mixed liquid crystals was studied using comprehensive graphic molecular modeling computer programs (Insight II and Discover) to calculate their molecular energy and stability energy. The effect of salts, e.g. Na⁺, Co³⁺, Y³⁺ and La³⁺, on the transition temperature range of the mixed liquid crystals was also investigated. The crown ether cholesteric liquid crystal B15C5‐COOCh was applied both as a surfactant and an ion transport carrier to transport metal ions through liquid membranes. Cholesteryl benzo‐15‐crown‐5 exhibited distinctive characteristics of a surfactant and the critical micellar concentration (CMC) of the surfactant was investigated by the pyrene fluorescence probe method. Cholesteryl benzo‐15‐crown‐5 was successfully applied as a good ion transport carrier (Ionophore) to transport various metal ions, e.g. Li⁺, Na⁺, La³⁺, Fe³⁺ and Co³⁺, through organic liquid membranes. The transport ability of the cholesteryl benzo‐15‐crown‐5 surfactant for these metal ions was in the order: Co³⁺ ≥ Li⁺ > Fe³⁺ > Na⁺ > La³⁺.     

Absorption and fluorescence properties of acridinones,thioacridinones, aminoacridines and related crown ethers

We report a study on the absorptive and emissive properties of 9‐acridinones, 9‐thioacridinones and 9‐aminoacridines including six crown ether derivatives. The effect of solvents and of the addition of cations (Na⁺, K⁺, Ca2⁺ and Mg2⁺) on these properties has been studied. The absorption of the crown ether derivative of 9‐thioacridinone is sensitive to solvents while the fluorescence of crown ethers derived from 9‐aminoacridines shows some specificity towards cations. Empirical modeling was used to discuss the emission characteristics of these compounds.     

聚合物假冠醚研究 (II)新型聚合物的合成、吸附特性与绿色应用

合成了两种假冠醚型聚合物。研究了聚合物对金属离子的静态吸附性能。结果表明,聚合物对Ag+,Pb2+,Hg2+ 表现出良好的吸附特性,且聚合物B的吸附能力优于聚合物A。吸附实验表明,除冠醚氧原子参与配位外,-CH2OH的氧原子亦参与了配位。聚合物B对Ag+的吸附过程中存在着明显的氧化还原现象,Ag+ 被还原为Ago,而聚合物分子中的 -CH2OH被氧化成为 -COOH。已初步将研究成果应用于本化学实验室的绿色化建设中。     

Synthesis,characterization, and ion‐complexing properties of polymers displaying densely packed arrays of crown‐ethers as lateral substituents

We report the synthesis and ion‐binding properties of four poly(crown‐ethers) displaying either one or two crown‐ethers (15‐crown‐5 or 18‐crown‐6) on every third carbon alongside the backbone. The polymers were synthesized by living anionic ring‐opening polymerization of disubstituted cyclopropane‐1,1‐dicarboxylates monomers. Cation binding of the polychelating polymers and corresponding monomers to Na⁺ and K⁺ was evaluated by picrate extraction and isothermal calorimetry titration. This novel family of poly(crown‐ethers) demonstrated excellent initial binding of the alkali ions to the polymers, with a higher selectivity for potassium. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2337–2345