Functionalized SBA-15 mesoporous silica in ion chromatography of alkali,alkaline earths,ammonium and transition metal ions

The retention properties of a SBA-15 mesoporous silica functionalized with –(CH₂)₃COOH groups, synthesized by a co-condensation route, were investigated for the ion chromatography of different cationic species. A systematic study on the effect of different eluent compositions containing non-complexing (methanesulfonic acid) or complexing (oxalic or pyridine-2,6-dicarboxylic acids) eluents, in the presence of organic modifiers (CH₃CN, CH₃OH, CH₃NH₂) on the retention of cations (Li⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Sr²⁺, Ba²⁺, NH₄⁺, Cu²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Co²⁺, Pb²⁺, Fe³⁺) chosen as model analytes and for their environmental importance, allowed us to elucidate the mechanisms (cation-exchange or complexation) involved in the retention on the SBA-15 phase. For the first time separations of cations on SBA-15 based stationary phases are investigated, providing the basis for further development of mesoporous silica chemistry for in-flow ion-exchange applications.     

Luminescence properties of Cu+ in zeolites. In situ study of thin layers

Thin layers of zeolites A and X with different alkali cations partially exchanged by Cu²⁺ have been prepared on glass or quartz supports. X-ray powder diffraction of these samples yield surprisingly good patterns. A sample chamber for in situ luminescence spectroscopy is described which allows the monitoring of the luminescence of Cu⁺ during the reduction of Cu²⁺, as a function of the reducing gas, the pretreatment, the water content and other parameters. Such luminescence measurements have shown that Cu²⁺ is reduced with CO and with H₂ to some extent already at room temperature. The first electronic absorption observed in Cu⁺ zeolites occurs in the near UV and is attributed to a Cu⁺ (4s^*) ← zeolite-oxygen lone-pair LMCT transition. Out of this charge transfer state luminescence occurs with a large Stokes shift which is caused by structural relaxation. The position of the emission depends on the alkali co-cations. In zeolite A this shift is correlated with the size of the unit cell. No correlation has been observed in zeolite X. The luminescence intensity is remarkably influenced by the degree of hydration going through a pronounced maximum that depends on the co-cation and on the type of zeolite.     

Adsorption de CO2 par des zeolithes X echangees par des cations bivalents

Adsorption of carbon dioxide by X zeolites exchanged with bivalent cations. The adsorption of carbon dioxide by X zeolites exchanged by Mg²⁺, Sr²⁺, Zn²⁺ and Cu²⁺ cations was studied by thermogravimetry. The corresponding isosteric heats of adsorption decrease with the filling of pore volume, except for Cu(63)X. This evolution of the heat indicates a specific interaction between cations present within supercages and CO₂ molecules. Several models have been used in order to describe the experimental isotherms. The best fit of sorption isotherm data was obtained with the Sips model.     

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.     

ICT-based Cu(II)-sensing 9,10-anthraquinonecalix[4]crown

A series of calix[4]arene-based chromogenic sensors bearing the 9,10-anthraquinone moiety have been synthesized and examined for their abilities to recognize various cations such as Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Cd²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺, Hg²⁺, Pb²⁺, Co²⁺, and Cu²⁺ by UV-vis spectroscopy. In acetonitrile, the presence of Cu²⁺ induces the formation of the 1:1 ligand/metal complex, which exhibits a new absorption band centered at 450 nm, and leads to an obvious color change from yellow to red.     

Thermodynamik der Metallkomplexbildung mit Polyoxadiazamacrocyclen

Ligands of the type H_3-nN(CH₂CH₂OCH₂CH₂OCH₂CH₂)_nNH_3?n with n values from 1 to 3 have been investigated. The stability constants and the heat evolved by formation of the 1:1 complexes of Na⁺, K⁺, Rb⁺, Tl⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cd²⁺, Ag⁺, Hg²⁺ and Pb²⁺ have been determined. The complex formation is discussed in terms of ΔH and ΔS taking into consideration the radii of the cations. In contrast with the normal trend, for the A cations, complex formation is exothermic and almost exclusively favoured by the reaction enthalpy.     

Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

In this study, IR studies of the coadsorption of ethanol and CO on Cu⁺ cations evidenced the transfer of electrons from ethanol to Cu⁺, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu⁺ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu⁺_exch also produced ethene, but in this case, the ethene was bonded to Cu⁺ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm⁻¹ was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu⁺_exch and bigger amounts of Cu⁺_ox, Cu²⁺_exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH₃COO⁻). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu⁺_ox and Cu²⁺ (Cu²⁺_exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu₂O as well as zeolites, in which the contribution of Cu⁺_ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu²⁺_ox (the role of Cu⁺_ox could not be elucidated), but Cu⁺_ox was the oxygen donor in the acetate formation.     

A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu<Superscript>2+</Superscript> cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu²⁺ over a wide range of other cations. The solution of 1 (10 μmol/L) upon addition of Cu²⁺ displayed distinguishing pink color compared with other cations including K⁺, Ni²⁺, Ca²⁺, Mn²⁺, Na⁺, Sr²⁺, Zn²⁺, Co²⁺, Cd²⁺, Mg²⁺, Cr³⁺, Ag⁺, and Ba²⁺, indicating the sensitivity and selectivity of 1 to Cu²⁺. Thus, the advantage of this assay is that naked-eye detection of Cu²⁺ becomes possible. Moreover, among these metal ions investigated, only Cu²⁺ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl₂ in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu²⁺ revealed the formation of a 2:1 metal-ligand complex through the metal coordination interaction. Supported by the National Natural Science Foundation of China (Grant Nos. 20872101 & 20772086)     

Cation exchange, interlayer spacing, and thermal analysis of Na/Ca-montmorillonite modified with alkaline and alkaline earth metal ions

Na-montmorillonites were exchanged with Li⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, while Ca-montmorillonites were treated with alkaline and alkaline earth ions except for Ra²⁺ and Ca²⁺. Montmorillonites with interlayer cations Li⁺ or Na⁺ have remarkable swelling capacity and keep excellent stability. It is shown that metal ions represent different exchange ability as follows: Cs⁺?>?Rb⁺?>?K⁺?>?Na⁺?>?Li⁺ and Ba²⁺?>?Sr²⁺?>?Ca²⁺?>?Mg²⁺. The cation exchange capacity with single ion exchange capacity illustrates that Mg²⁺ and Ca²⁺ do not only take part in cation exchange but also produce physical adsorption on the montmorillonite. Although interlayer spacing d ₀₀₁ depends on both radius and hydration radius of interlayer cations, the latter one plays a decisive role in changing d ₀₀₁ value. Three stages of temperature intervals of dehydration are observed from the TG/DSC curves: the release of surface water adsorbed (36?C84?°C), the dehydration of interlayer water and the chemical-adsorption water (47?C189?°C) and dehydration of bound water of interlayer metal cation (108?C268?°C). Data show that the quantity and hydration energy of ions adsorbed on montmorillonite influence the water content in montmorillonite. Mg²⁺-modified Na-montmorillonite which absorbs the most quantity of ions with the highest hydration energy has the maximum water content up to 8.84%.     

A Thermodynamic Study Between 18-Crown-6 with Mg2+, Ca2+, Sr2+and Ba2+ Cations in Water–Methanol and Water–Ethanol Binary Mixtures Using The Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations with the macrocyclic ligand, 18-Crown-6 (l8C6) in water–methanol (MeOH) binary systems as well as the complexation reactions between Ca²⁺ and Sr²⁺ cations with 18C6 in water–ethanol (EtOH) binary mixtures have been studied at different temperatures using conductometric method. The conductance data show that the stoichiometry of all the complexes is 1:1. It was found that the stability of 18C6 complexes with Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations is sensitive to solvent composition and in all cases, a non-linear behaviour was observed for the variation of log K _f of the complexes versus the composition of the mixed solvents. In some cases, the stability order is changed with changing the composition of the mixed solvents. The selectivity order of 18C6 for the metal cations in pure methanol is: Ba²⁺ > Sr²⁺ > Ca²⁺ > Mg²⁺. The values of thermodynamic parameters (Δ H _c ° and Δ S _c °) for formation of 18C6–Mg²⁺, 18C6–Ca²⁺, 18C6–Sr²⁺ and 18C6–Ba²⁺complexes were obtained from temperature dependence of the stability constants. The obtained results show that the values of (Δ H _c ° and Δ S _c °) for formation of these complexes are quite sensitive to the nature and composition of the mixed solvent, but they do not vary monotonically with the solvent composition.This revised version was published online in July 2005 with a corrected issue number.     

Analytical study of highly condensed non ionic surfactants. Separation on cation exchangers

Summary This study was aimed at optimizing the separation of non-ionic surfactants, resulting from the condensation of ethylene oxide with natural fatty alcohols in the C₁₆ and C₁₈ range (saturated and unsaturated), and presenting a high degree of condensation, i.e. 20 and 25 ethylene oxide units (Brij 99 and KM 25). The cation exchange stationary phase is a partially ionized silica, conditioned in different ways. We have studied the influence of the nature of cations on the separation selectivity. Cations studied included alkali metals (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺), alkaline earth metals (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), transition metals (Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Cu²⁺), and quaternary ammonium (NH ₄ ⁺ , NMe ₄ ⁺ ) ions as well as a proton (acetic acid). The influences of ionic strength, pH and addition of cosolvent were examined. A study of the influence of temperature on the system selectivity evidenced a strong interdependance of these two parameters. The optimized conditions [mobile phase: CH₃CN/H₂O (92/8), pH 7.4, sodium acetate 5.10^–3 M; temperature gradient between 25 and 50°C] allowed for the first time the distributions of Brij 99 and KM 25 to be obtained.     

Degree of Binding of Double-Charged Cations in Solutions of 2-Acrylamido-2-Methylpropanesulfonate Copolymers

The degree of binding of Mg^{2 +}, Ca²⁺, Sr²⁺, and Ba²⁺ cations with polysulfonate anions in aqueous solutions of 2-acrylamido-2-methylpropanesulfonate polymers and their binary mixtures with acrylamide and N-vinylpyrrolidone with various molecular characteristics was studied by the Terayama-Wall viscometric procedure.     

Cation Complexation by a Lower Rim Calix(4)arene Derivative: Structural,Electrochemical and Thermodynamic Studies

The synthesis and characterization (¹H and ¹³C NMR) of a partially substituted lower rim p-tert-butylcalix(4)arene, namely, 5,11,17,23-tetra-4-tert-butyl-25,27-bis(diethylphosphate amino)ethoxy-26,28-dihydroxycalix[4]arene (1), are reported. The solution thermodynamics of the ligand in a variety of solvents at 298.15?K was investigated through solubility (hence standard Gibbs energy of solution) measurements while the calorimetric technique was used to derive the standard solution enthalpy. These data were used to calculate the standard entropy of solution. An enthalpy–entropy compensation effect is shown and, as a result, slight variations are observed in the transfer Gibbs energies of this ligand from the reference to other solvents. ¹H NMR, conductance and calorimetric measurements were carried out to establish the degree of interaction of the ligand with univalent (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺ and Ag⁺) and bivalent (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Hg²⁺, Cu²⁺, Zn²⁺) cations in acetonitrile, methanol, N,N-dimethylformamide and propylene carbonate. No complexation was found between this ligand and univalent cations in these solvents. As far as the bivalent cations are concerned, interaction between 1 and these cations was found only in acetonitrile. The versatile behaviour of this ligand with bivalent cations in this solvent is reflected by the formation of complexes of different stoichiometry. Thus the interaction of 1 with alkaline-earth (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) and Pb²⁺ metal cations leads to the formation of 1:2 (cation:ligand) complexes. However, for other bivalent metal cations (Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺) the complex stoichiometry was found to be 1:1. The results are discussed in terms of the key role played by acetonitrile in processes involving calix[4]arene derivatives.     

A diamide-diamine based Cu chromogenic sensor for highly selective visual and spectrophotometric detection

A diamide-diamine based sensor 3 possessing anthracene-9,10-dione as a chromogenic moiety has been synthesized and demonstrates a highly selective colour change from red to blue with Cu²⁺ for visual detection of Cu²⁺ (5-50 μM). Other metal ions, viz. Fe²⁺, Cr³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations do not lead to any change in colour and their presence does not interfere with the visual and quantitative analysis of Cu²⁺. The selective deprotonation of an aryl amine NH by Cu²⁺ is responsible for a bathochromic shift and significant colour changes. Significantly, the stability of the 3·Cu²⁺ complex between pH 7 and 12 allows Cu²⁺ estimation under neutral and basic conditions.     

Adsorptive removal of halo-olefinic impurities from 1,1,1,3,3-pentafluoropropane over ion-exchanged Y zeolites

Various metal cations exchanged Y zeolites were prepared via the exchange of NaY zeolite with aqueous solutions containing K⁺, Ca²⁺, Cu²⁺, La³⁺ and Ce³⁺ cations, respectively. The influence of the extra-framework cations nature of these ion-exchanged Y zeolites on their adsorption performance for a low content of halo-olefinic impurities, mainly including 1-chloro-3,3,3-trifluoro-1-propene (HCFC-1233zd), 1-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224zb) and 2-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224xe), in the 1,1,1,3,3-pentafluoropropane (HFC-245fa) product after distillation was investigated. HCFC-1233zd impurity can be substantially removed from HFC-245fa product feed via the adsorption over multivalent metal cations and Cu⁺ cation exchanged Y zeolites, which is ascribed to the formation of π-adsorption complexes between HCFC-1233zd and zeolites, rather than over alkaline metal cations exchanged Y zeolites. Among multivalent metal cations exchanged Y zeolites, CeY has the highest adsorption capacity for HCFC-1233zd and best regeneration performance, due to its lowest density of strong Brønsted and weak Lewis acid sites as well as high framework stability during the regeneration. Regardless of the cations introduced in Y zeolite used as an adsorbent, HCFC-1224zb and HCFC-1224xe impurities are not obviously removed from HFC-245fa product feed via the adsorption, maybe due to more halogen atoms linked with the double bond in them comparing with HCFC-1233zd.     

Complexation Studies of a Calix[4](aza)crown and Crystal Structure of its Magnesium Complex

A systematic study of extraction properties and complexation behaviour of the calix[4](aza)crown 1 towards alkaline earth (Mg²⁺, Ca²⁺,Sr²⁺, Ba²⁺) and transition metal (Co²⁺, Ni²⁺, Cu²⁺,Zn²⁺) cations is presented. The binding behaviour of 1 was also investigated by ¹H-NMR and the crystal structure of the 1:1 complex with Mg²⁺ isdescribed.     

Study on the equilibrium in the MCl2?CH3OH?H2O System (M = Sr2+, Ba2+) at 25°C and 50°C

Studies on the equilibrium in the system MCl₂? CH₃OH? H₂O at 25°C and 50°C (M = Sr²⁺, Ba²⁺) show that the dehydration in the water-methanol systems proceeds stepwise and all possible lower crystal hydrates may be obtained at 25°C depending on the molar ratio for the mixed solvent. The dehydration and solvation processes in the three-component system MCl₂? CH₃OH? H₂O (M = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) have been considered in general and compared with those in the bromide system.     

Host-guest complexation : 43. Synthesis and binding properties of a macrocycle composed of two phenanthrolines and two sulfonamide units

Treatment of 2,9-bis(chloromethyl)-1,10-phenanthroline with toluenesulfonamide and K₂CO₃ in HCON(CH₃)₂ gave macro-cycle 1 (21%) composed of two phenantroline units bonded to each other through two CH₂N(Ts)CH₂ bridges. The 18-membered inner ring system contains six nitrogens, each of which is separated by two carbons. A crystal structure of 1.2H₂O indicated the two faces of the phenanthrolines approach each other to place their four nitrogens nearly in a plane bridged by a water dimer held in position by bifurcated hydrogen bonds. The two ArSO₂N groups are turned outward, and the hydrogens of their attached CH₂ groups are oriented inward toward the water dimer, which serves as a guest. Complexation was indicated by addition of a variety of salts to a solution of 1 in (CD₃)₂SO, which casued changes in the ¹H NMR by as much as 1.5 ppm. Complexing ions include Li⁺. Na⁺, K⁺, Rb⁺, Cs⁺, NH₄⁺ , Ag⁺, Cu⁺ , Tl⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ noncomplexing ions are Mg²⁺, Ca²⁺ , Sr²⁺ , Ba²⁺ , UO₂²⁺, and Ce³⁺. A correlation between the chemical shifts of the CH₃ and tolyl aryl protons of the host and the ionic radii of the guests is interpreted in terms of three different host conformations in the various complexes. Equilibrations of the guest cations between 1 and cryptaplexes of Na⁺ , K⁺, Rb⁺, Cs⁺, and NH₄⁺ picrates in (CD₃)₂SO provided the following estimates of the -ΔG° values of binding of these salts by 1: 8.4, 8.5, 6.8, <3.5, and 8.85 kcal mol^-1, respectively.     

Antimicrobial Properties of Zeolite-X and Zeolite-A Ion-Exchanged with Silver,Copper, and Zinc Against a Broad Range of Microorganisms

Zeolites are nanoporous alumina silicates composed of silicon, aluminum, and oxygen in a framework with cations, water within pores. Their cation contents can be exchanged with monovalent or divalent ions. In the present study, the antimicrobial (antibacterial, anticandidal, and antifungal) properties of zeolite type X and A, with different Al/Si ratio, ion exchanged with Ag⁺, Zn²⁺, and Cu²⁺ ions were investigated individually. The study presents the synthesis and manufacture of four different zeolite types characterized by scanning electron microscopy and X-ray diffraction. The ion loading capacity of the zeolites was examined and compared with the antimicrobial characteristics against a broad range of microorganisms including bacteria, yeast, and mold. It was observed that Ag⁺ ion-loaded zeolites exhibited more antibacterial activity with respect to other metal ion-embedded zeolite samples. The results clearly support that various synthetic zeolites can be ion exchanged with Ag⁺, Zn²⁺, and Cu²⁺ ions to acquire antimicrobial properties or ion-releasing characteristics to provide prolonged or stronger activity. The current study suggested that zeolite formulations could be combined with various materials used in manufacturing medical devices, surfaces, textiles, or household items where antimicrobial properties are required.     

Application of localized reactivity index in combination with periodic DFT calculation to rationalize the swelling mechanism of clay type inorganic material

Clays are layered alumino-silicates. Clays swell and expand in aqueous solution. This property governs the usage of these materials in synthesis of nano-composites and is a source of many of its catalytic applications. We used both localized and periodic calculations within the realm of density functional theory (DFT) on a series of monovalent (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺), and divalent (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) cations, to monitor their effect on the swelling of clays. The activity order obtained for the exchangeable cations among all the monovalent and divalent series studied is: Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ > Cs⁺ > Rb⁺ > Na⁺ > Li⁺ > K⁺. We have studied two types of clays, montmorillonite and beidellite, with different surface structures and with/without water using periodic calculations. We have calculated the layer spacing at the first, second and third hydration shells of exchangeable cation, to compare with the experimentald-spacing values to correlate with humidity. A novel quantitative scale is proposed in terms of the intermolecular relative nucleophilicity of the active cation sites in their hydrated state through Fukui functions using hard-soft acid base (HSAB) principle. Finally, a swelling mechanism is proposed. This is a unique study where a combination of periodic and localized calculations has been performed to validate the capability of reactivity index calculations in material designing.