Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li⁺, Na⁺, K⁺, and Cs⁺ ions and the study of the influence of alkali metal cations on CO₂ adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs⁺) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO₂ adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li⁺ or K⁺ cations.     

Selective complexation of alkali metal ions and nanotubular cyclopeptides: a DFT study

A density functional theory based on interaction of alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) with cyclic peptides constructed from 3 or 4 alanine molecule (CyAla3 and CyAla4), has been investigated using mixed basis set (C, H, O, Li⁺, Na⁺ and K⁺ using 6-31+G(d), and the heavier cations: Rb⁺ and Cs⁺ using LANL2DZ). The minimum energy structures, binding energies, and various thermodynamic parameters of free ligands and their metal cations complexes have been determined with B3LYP and CAM-B3LYP functionals. The order of interaction energies were found to be Li⁺ > K⁺ > Na⁺ > Rb⁺ > Cs⁺ and Li⁺ > Na⁺ > K⁺ ? Rb⁺ > Cs⁺, calculated at CAM-B3LYP level for the M/CyAla3 and M/CyAla4 complexes, respectively. Their selectivity trend shows that the highest cation selectivity for Li⁺ over other alkali metal ions has been achieved on the basis of thermodynamic analysis. The main types of driving force host–guest interactions are investigated, the electron-donating O offers lone pair electrons to the contacting LP* of alkali metal cations.     

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.     

A DFT/PCM Study on the Affinity of Salinomycin to Bind Monovalent Metal Cations

The affinity of the polyether ionophore salinomycin to bind IA/IB metal ions was accessed using the Gibbs free energy of the competition reaction between SalNa (taken as a reference) and its rival ions: [M⁺-solution] + [SalNa] → [SalM] + [Na⁺-solution] (M = Li, K, Rb, Cs, Cu, Ag, Au). The DFT/PCM computations revealed that the ionic radius, charge density and accepting ability of the competing metal cations, as well as the dielectric properties of the solvent, have an influence upon the selectivity of salinomycin. The optimized structures of the monovalent metal complexes demonstrate the flexibility of the ionophore, allowing the coordination of one or two water ligands in SalM-W₁ and SalM-W₂, respectively. The metal cations are responsible for the inner coordination sphere geometry, with coordination numbers spread between 2 (Au⁺), 4 (Li⁺ and Cu⁺), 5/6 (Na⁺, K⁺, Ag⁺), 6/7 (Rb⁺) and 7/8 (Cs⁺). The metals’ affinity to salinomycin in low-polarity media follows the order of Li⁺ > Cu⁺ > Na⁺ > K⁺ > Au⁺ > Ag⁺ > Rb⁺ > Cs⁺, whereas some derangement takes place in high-dielectric environment: Li⁺ ≥ Na⁺ > K⁺ > Cu⁺ > Au⁺ > Ag⁺ > Rb⁺ > Cs⁺.     

Synthesis of novel chromogenic azocalix[4]arenemonoquinones and their binding with alkali metal cations

Five new chromogenic azocalix[4]arenemonoquinones have been synthesized, characterized and examined for their interaction with alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) by UV-visible spectroscopic and cyclic voltammetric techniques. It has been determined that 4a selectively exhibits a significant bathochromic shift in its UV-visible spectrum on interaction with potassium ion in comparison to its treatment with other alkali metal cations. The binding stoichiometry of 4a and potassium ion was established to be 1:1 with an association constant of 3.27 × 10⁴ M^?1. Cyclic voltammetric experiments in 4:1 dichloromethane-acetonitrile also revealed a significant anodic shift (ΔE _(1/1′) = 115 mV) of the original redox waves of 4a on interaction with potassium ion.     

Spectrophotometric studies of alkali and alkali earth metal ions complexes of mono amino derivative of calix[4]arene

The synthesis and complexive abilities of 5,11,17-tris(tert-butyl)-23 amino-25,26,27,28-tetra-propoxycalix[4]arene towards alkali cations Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and alkali earth cations Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ in methanol-chloroform mixture have been evaluated at 25°C, using UV-Vis spectrophotometric techniques. The results showed that the ligand is capable to complex with all the cations by 1: 1 metal to ligand ratios. The selectivity presented considering the calculated formation constants are in the order Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ and Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ with the ligand.     

Fluoride complexes of the alkali metal ions

Measurements by fluoride ion-selective electrode potentiometry on the very weak monofluoride complexes of the alkali metal ions in aqueous solution at 25°C and an ionic strength of 1M indicate their stability constants lie in the order Li⁺ > Na⁺ > K⁺ > Rb⁺ ? Cs⁺. Data at varying ionic strengths and temperatures were used to calculate infinite dilution stability constants and enthalpies and entropies of complexation for LiF and NaF.     

Probing the interaction of alkali and transition metal ions with bradykinin and its des-arginine derivatives via matrix-assisted laser desorption/ionization and postsource decay mass spectrometry

The complexes of the peptides (Pep) bradykinin (RPPGFSPFR), des-Arg¹-bradykinin, and des-Arg⁹-bradykinin with the metal (M) ions Na⁺, K⁺, Cs⁺, Cu⁺, Ag⁺, Co²⁺, Ni²⁺, and Zn²⁺ are generated in the gas phase by matrix-assisted laser desorption/ionization and the structures of the corresponding [Pep + M⁺]⁺ or [Pep − H⁺ + M²⁺]⁺ cations are probed by postsource decay (PSD) mass spectrometry. The PSD spectra depend significantly on the metal ion attached; moreover, the various metal ions respond differently to the presence or absence of a basic arginine residue. The Na⁺ and K⁺ adducts of all three peptides mainly produce N-terminal sequence ions upon PSD; the fragments observed point out that these metal ions are anchored by the PPGF segment and not the arginine residue(s). In contrast, the adducts of Cu⁺ and Ag⁺ show a strong dependence on the position of Arg; complexes of des-Arg¹-Pep (which contains a C-terminal Arg) produce primarily y_n ions whereas those of des-Arg⁹-Pep generate exclusively a_n and b_n ions. These trends are consistent with Cu⁺ ligation by Arg’s guanidine group. The [Pep + Cs⁺]⁺ ions mainly yield Cs⁺; a second significant fragmentation occurs only if a C-terminal arginine is present and involves elimination of this arginine’s side chain plus water. This reaction is rationalized through a salt bridge mechanism. The most prominent PSD products from [Pep − H⁺ + Co²⁺]⁺ and [Pep − H⁺ + Ni²⁺]⁺ contain at least one phenylalanine residue, revealing a marked preference for these divalent metal ions to bind to aromatic rings; the fragmentation patterns of the complexes further suggest that Co²⁺ and Ni²⁺ bind to deprotonated amide nitrogens. The coordination chemistry of Zn²⁺ combines features found with the divalent Co²⁺/Ni²⁺ as well as the monovalent Cu⁺/Ag⁺ transition metal ions. Generally, the structure and fragmentation behavior of each complex reflects the intrinsic coordination preferences of the corresponding metal ion.     

Synthesis of macrocyclic tetraamides derived from α-amino acids and their investigations using ESI-MS technique

Chiral α,ω-diesters react under high-pressure conditions (10 kbar) with α,ω-diamines to give chiral cyclic tetraamides of C₂-symmetry. The complexation properties of tetraamides towards alkali metal cations (Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺) were estimated on the basis of ESI-MS spectra.     

An Imine‐Based Molecular Cage with Distinct Binding Sites for Small and Large Alkali Metal Cations

The synthesis of a cylindrical, imine‐based cage composed of two trimeric metallamacrocycles is described. The cage acts as a heterotopic receptor for alkali metal cations. The small cations Li⁺, Na⁺, and K⁺ bind to the outside of the cage with good selectivity for Li⁺, whereas the larger cations Rb⁺ and Cs⁺ are bound inside the cage to form unusual π complexes with a good selectivity for Cs⁺. Negative heterotopic cooperativity between the two binding sites is observed. The complexation of Cs⁺ is associated with a color change, which enables the cage to be used as a specific sensor for Cs⁺.     

Isosteric heats of adsorption of carbon dioxide on zeolite MCM-22 modified by alkali metal cations

Adsorption isotherms of carbon dioxide were measured on cation-exchanged (Li⁺, Na⁺, K⁺, Cs⁺) MCM-22 zeolite with the molar ratio of Si/Al=15 and series of Na-MCM-22 of Si/Al molar ratios varying in the range from 15 to 40 at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO₂ adsorption, isosteric heats of adsorption were calculated. The obtained dependences of isosteric heats related to the amount of CO₂ adsorbed have provided detailed insight into the interaction of carbon dioxide molecule with alkali metal cations.     

Impact of the alkali cation on the electrocatalytic oxidation of urea and benzyl alcohol on nickel electrode

The effect of electrolyte alkali metal cations (Li⁺, Na⁺, or K⁺) on the electro-oxidation of urea and benzyl alcohol on NiOOH catalyst has been investigated by means of cyclic voltammetry and chronoamperometry in the presence of an electrolyte containing LiOH, NaOH, or KOH. The catalytic activity toward the electro-oxidation of urea and benzyl alcohol was found to increase in the sequence Li⁺ < Na⁺ < K⁺. This activity's difference is partly caused by different surface blockage abilities by OH–M⁺(H₂O)_x (M: Li, Na, K) clusters, which is similar to many electrocatalytic reactions on Pt reported previously, additionally, incorporation of various cations to the catalyst may induce the activities difference as well.     

Photophysical and photochemical processes in zeolite cavities: The effects of ion-exchanged alkalimetal cations on the excited states of xanthone and the photolysis of 2-pentanone

The characteristics properties of xanthone phosphorescence and of 2-pentanone photolysis in alkali metal cation-exchanged zeolites have been investigated to clarify the effect of the micro-environment of host-adsorbents on the photophysical and photochemical properties of guest-molecules in restricted void spaces. The enhancement of the phosphorescence yields of xanthone included in zeolites is observed by changing the exchangeablealkali metal cation from Li⁺ to Cs⁺. Simultaneously, the phosphorescence lifetimes were observed to continuously shorten by changing the cation from Li⁺ to Cs⁺. These results suggest that the external heavy-atom effect deriving from the alkali metal cations on the singlet-triplet transitions of xanthone molecules stabilized on alkali metal cations in the order of Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The yields for the photolysis of 2-pentanone included in zeolites increase with changing the alkali metal cation from Li⁺ to Cs⁺. IR investigations of the adsorption state of 2-pentanone indicate that strength of the interaction between the alkali metal cations and 2-pentanones decreases by changing the cation from Li⁺ to Cs⁺, which results in a longer lifetime of 2-pentanone. The selectivity of propylene formation is dramatically increased by changing the cation from Li⁺ to Cs⁺. The enhanced formation of propylene is asociated with the hydrogen absorption from propyl radicals by lattice oxygen, their basicity increasing by changing the cation from Li⁺ to Cs⁺. Thus, these changes in the zeolite cavities modified by exchanging cations caused significant effects not only on the excited state but also on the following chemical reactions of ketones.     

Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid–Liquid Interface

The facilitated transfer of alkali metal ions (Na⁺, K⁺, Rb⁺, and Cs⁺) by 25,26,27,28‐tetraethoxycarbonylmethoxy‐thiacalix[4]arene across the water/1,2‐dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half‐wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li⁺ ion was not observed across the water/1,2‐dichloroethane interface, the facilitated transfers were observed by formation of 1 : 1 (metal:ionophore) complex for Na⁺, K⁺, and Rb⁺ ions except for Cs⁺ ion. In the case of Cs⁺ a 1 : 2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na⁺, K⁺, Rb⁺, and Cs⁺, were estimated as 6.52, 7.75, 7.91 (log β₁°), and 8.36 (log β₂°), respectively.     

Intermetallic Competition in the Fragmentation of Trimetallic Au–Zn–Alkali Complexes

Cationization is a valuable tool to enable mass spectrometric studies on neutral transition‐metal complexes (e.g., homogenous catalysts). However, knowledge of potential impacts on the molecular structure and catalytic reactivity induced by the cationization is indispensable to extract information about the neutral complex. In this study, we cationize a bimetallic complex [AuZnCl₃] with alkali metal ions (M⁺) and investigate the charged adducts [AuZnCl₃M]⁺ by electrospray ionization mass spectrometry (ESI‐MS). Infrared multiple photon dissociation (IR‐MPD) in combination with density functional theory (DFT) calculations reveal a μ³ binding motif of all alkali ions to the three chlorido ligands. The cationization induces a reorientation of the organic backbone. Collision‐induced dissociation (CID) studies reveal switches of fragmentation channels by the alkali ion and by the CID amplitude. The Li⁺ and Na⁺ adducts prefer the sole loss of ZnCl₂, whereas the K⁺, Rb⁺, and Cs⁺ adducts preferably split off MCl₂ZnCl. Calculated energetics along the fragmentation coordinate profiles allow us to interpret the experimental findings to a level of subtle details. The Zn²⁺ cation wins the competition for the nitrogen coordination sites against K⁺, Rb⁺, and Cs⁺ , but it loses against Li⁺ and Na⁺ in a remarkable deviation from a naive hard and soft acids and bases (HSAB) concept. The computations indicate expulsion of MCl₂ZnCl rather than of MCl and ZnCl₂.     

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.     

Complex formation of alkali and alkaline earth metal ions with cryptands containing thiourea units as a part of macrocyclic framework in aqueous methanol

The stability constants (K_s) of the complexes of alkali and alkaline earth metal ions with new type of the cryptands containing one or two thiourea moieties in one of the bridges were determined by means of pH-metric measurements in 95% aqueous methanol at 25 °C. Cryptands studied do not show any regular alteration of complexes stability depending on the mutual relation of cryptand cavity and cation sizes. In all cases, they form the most stable complexes with K⁺ along the series of alkali metal ions and with cations of Ba²⁺ or Sr²⁺ in the series of alkaline earth ions independently of variations of their structure. The log K_s values for K⁺, Sr²⁺ and Ba²⁺ vary in limits 3.51-5.90, 2.29-7.05 and 2.35-7.51, respectively, depending on the cryptands structure. The complexes stability of the studied cryptands increases in the order Li⁺ < Na⁺ (Cs⁺) < Cs⁺ (Na⁺) < Rb⁺ < K⁺ and Mg²⁺ < Ca²⁺ < Sr²⁺ (Ba²⁺) < Ba²⁺ (Sr²⁺). However, cryptands containing at least one oxygen atom between the nitrogen bridgehead and group of thiourea form considerably more stable complexes with respect to cryptands in which thiourea group connected with nitrogen bridgeheads via ethylenic chain. The origins of the cryptands complexation behavior are discussed in terms of ligands and complexes structural features.     

Solvent extraction of calcium and strontium into nitrobenzene by using hydrogen dicarbollylcobaltate in the presence of polypropylene glycol PPG 425

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺(aq) + Cs⁺(org) ⟺ M⁺(org) + Cs⁺(aq) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (M⁺ = Li⁺, H₃O⁺, Na⁺, NH₄⁺ \hbox{NH}_{4}{}^{+} , Ag⁺, Tl⁺, K⁺, Rb⁺; aq = aqueous phase, org = FS 13 phase) were evaluated. Furthermore, the individual extraction constants of the M⁺ cations in the mentioned two-phase system were calculated; they were found to increase in the series of Li⁺ < H₃O⁺ < Na⁺< NH₄ ⁺ \hbox{NH}_{4}{}^{ + } < Ag⁺ < Tl⁺ < K⁺ < Rb⁺ < Cs⁺.     

Ion Chromatography on Poly(Crown Ether)-Modified Silica Possessing High Affinity For Sodium

Abstract

Stationary phases which have great affinity for Na⁺ were synthesized by incorporating 12-crown-4 polymer on silica gel for liquid chromatography of alkali and alkaline-earth metal ions. The stationary phases interact with Na+ most strongly of all alkali metal ions as expected, and the retention times on liquid chromatography of alkali metal ions were in the sequence Li⁺ < Cs⁺ < Rb⁺ < K⁺ < Na⁺. On the stationary phase, a mixture of Li⁺, Na⁺, and K⁺ can be separated completely by the elution with water/methanol mixture. By the use of spherical type silica gel instead of irregular type one and by effective end-capping of the residual silanol groups, the peak symmetry was improved significantly.     

一种基于硫杂杯[4]芳烃的高效银离子载体

合成了基于下缘含有酰肼基团的硫杂杯芳烃衍生物的银离子载体1,其核磁研究证实硫杂杯芳烃以1,3-交替构象存在,并且通过非竞争萃取实验和竞争萃取实验研究了它对碱金属和过渡金属离子（Li⁺, Na⁺, K⁺, Cs⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Ag⁺）的键合能力和选择性。实验结果表明：将酰肼基团引入1,3-交替构象的硫杂杯芳烃骨架的下缘可以提高其对Ag⁺的键合能力和选择性,同时,对Cu²⁺的萃取能力较弱,对碱金属离子和其它的重金属离子几乎没有萃取能力。进一步的核磁滴定和电喷雾质谱实验显示化合物1与银离子形成配合物的配合计量比为1：1,由此推断主要由“N-Ag⁺”配位键以及硫杂杯芳烃骨架的协同作用构成了化合物1与银离子的配合模式。