Azo calix[4]arene based neodymium(III)-selective PVC membrane sensor

We found that the PVC membrane, containing azo calix[4]arene is a suitable ionophore, exhibited a Nernstian response for neodymium (Nd³⁺) ions (with slope of 19.8 ± 0.2 mV decade⁻¹ for the triply charged ion) over a wide linear range of 4.0 × 10⁻⁸ to 1.0 × 10⁻¹ mol L⁻¹ with a detection limit 1.0 × 10⁻⁸ mol L⁻¹, a relatively fast response time, in the whole concentration range (<10 s), and a considerable life time at least for four months in the pH range of 4.0-8.0. Furthermore, the electrode revealed high selectivity with respect to all the common alkali, alkaline earth, transition and heavy metal ions, including the members of the lanthanide family other than Nd³⁺. Concerning its applications, it was effectively employed for the determination of neodymium ions in industrial waste water as well as in lake water.     

Liquid-liquid extraction of thorium (IV) with hexaacetato calix(6)arene

Thorium(IV) was quantitatively extracted at pH 7.5 with 0.0001M of hexaacetato calix(6)arene in toluene and after stripping with 0.05M nitric acid, it was determined spectrophotometrically at 545 nm with thoron. Thorium(IV) was separated from commonly associated elements in fission products like uranium(VI), cesium(I), lead(II), strontium(II) and cerium(IV) in varying proportions. The method is simple, rapid, selective and applicable for the microgram concentrations of thorium(IV).     

Simultaneous preconcentration of uranium(VI) and thorium(IV) from aqueous solutions using a chelating calix[4]arene anchored chloromethylated polystyrene solid phase

A new chelating polymeric sorbent is developed using Merrifield chloromethylated resin anchored with calix[4]arene-o-vanillinsemicarbazone for simultaneous separation and solid phase extractive preconcentration of U(VI) and Th(IV). The “upper-rim” functionalized calix[4]arene-o-vanillinsemicarbazone was covalently linked to Merrifield resin and characterized by FT-IR and elemental analysis. The synthesized chelating polymeric sorbent shows superior binding affinity towards U(VI) and Th(IV) under selective pH conditions. Various physico-chemical parameters that influence the quantitative extraction of metal ions were optimized. The optimum pH range and flow rates for U(VI) and Th(IV) were 6.0-7.0 and 1.0-4.0 ml min⁻¹ and 3.5-4.5 and 1.5-4.0 ml min⁻¹, respectively. The total sorption capacity found for U(VI) and Th(IV) was 48734 and 41175 μg g⁻¹, respectively. Interference studies carried out in the presence of diverse ions and electrolyte species showed quantitative analyte recovery (98-98.5%) with lower limits of detection, 6.14 and 4.29 μg l⁻¹ and high preconcentration factors, 143 and 153 for U(VI) and Th(IV), respectively. The uptake and stripping of these metal ions on the resin were fast, indicating a better accessibility of the metal ions towards the chelating sites. The analytical applicability of the synthesized polymeric sorbent was tested with some synthetic mixtures for the separation of U(VI) and Th(IV) from each other and also from La(III), Cu(II) and Pb(II) by varying the pH and sequential acidic elution. The validity of the proposed method was checked by analyzing these metal ions in natural water samples, monazite sand and standard geological materials.     

Titanocene dichloride route to a tetranuclear oxo-bridged monocyclopentadienyl titanium(IV) calix[4]arene complex

Lithiation of p-tBu-calix[4]arene followed by reaction with titanocene dichloride affords a novel tetranuclear titanium(IV) monocyclopentadienyl complex, wherein a single calix[4]arene in a cone conformation provides O-phenoxy coordination to four titanium atoms, with additional mu-oxo bridging between titanium centres in an eight membered ring.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

A coated wire-type lead(II) ion-selective electrode based on a phosphorylated calix[4]arene derivative.

The preparation of a lead-selective electrode based on 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(diphenylphosphinoylmethoxy)calix[4]arene (1) as an ionophore is reported. The plasticized PVC membrane containing 30% PVC, 57% ortho-nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 9% ionophore 1 was directly coated on a graphite electrode. It exhibits a nearly Nernstian slope of 28.0 +/- 0.2 mV decade(-1) over a concentration range of 1 x 10(-5) - 1 x 10(-2) mol dm(-3) with a detection limit of 1.4 x 10(-6) mol dm(-3). The response time of the electrode was found to be ca. 17 s. The potential of the sensor was independent of the pH variation in the range 3.5 - 5.0. The selectivity of the electrode performance towards lead ions over Th4+, La3+, Sm3+, Dy3+, Y3+, Ca2+, Sr2+, Cd2+, Mn2+, Zn2+, Ni2+, Co2+, NH4+ Ag+, Li+, Na+ and K+ ions was investigated. The prepared electrode was used successfully as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for Pb2+ measurements in various synthetic water samples spiked with lead nitrate was also checked.     

Synthesis of molybdenocene(IV) and tungstenocene(IV) tropolonato complexes: Its derivative containing calix[4]arene moiety

The cationic di-μ-hydroxo dinuclear complexes of molybdenocene and tungstenocene [Cp₂M(μ-OH)₂MCp₂]⁺ (Cp = η-C₅H₅; M = Mo or W) react with tropolone to afford corresponding tropolonato complexes [Cp₂M(trop)]⁺ (trop = C₇H₅O₂). The products were investigated by IR, ¹H NMR, and ¹³C NMR spectroscopy as well as by X-ray crystallography (M = W). The structure shows that the central metal is surrounded by a distorted tetrahedral array of the two centers of cyclopentadienyl ligands and the two oxygen atoms of tropolonato ligand. The reaction has been extended to the synthesis of calix[4]arene receptor functionalized at the 1,3-positions of the upper rim with two tropolonato-molybdenocene centers.     

Extraction of technetium(vii) by calix[4]arene tetraketones and tetraesters from acidic and basic media

Tetrasubstituted on the lower rim calix[4]arenes, containing carbonyl and ester groups, and existing in a cone conformation are selective and efficient extracting agents for Tc^VII extraction from both acidic and basic solutions.     

Synthesis and Conformational Properties of Bis（calix [4] arene）

The bis(calix [4] arene)3 was synthesized in moderate yield by the reaction of p-tert-butylcalix [4] arene (1) with 1,4-bis(chloromethyl) benzene (2). The conformation of all alkylated product 4 was investigated by the variable-temperature ^1H-NMR.     

Solid-phase extractive preconcentration and separation of lanthanum(III) and cerium(III) using a polymer-supported chelating calix [4] arene resin

In the present paper, solid-phase extractive preconcentration and separation of lanthanum(III) and cerium(III) using calix[4]arene-o-vanillinsemicarbazone immobilized on a polymeric matrix, a Merrifield peptide resin, is proposed. The diamino derivative of calix[4]arene was first diazotized and coupled with o-vanillinsemicarbazone to obtain a new “upper-rim” functionalized calix[4]arene-o-vanillinsemicarbazone. It was then covalently linked to the Merrifield peptide resin and characterized by FT-IR and elemental analysis. Quantitative studies were carried out by spectrophotometry and ICP-AES with a relative standard deviation of 1.7%. Various physicochemical parameters like pH, concentration of eluting agents, flow rate, total sorption capacity, metal-ligand stoichiometry, exchange kinetics, preconcentration factor, distribution coefficient, breakthrough capacity, resin stability, and effect of electrolytes and associated metal ions have been studied. The uptake and stripping of these metal ions on the resin was fast, indicating a better accessibility of La(III) and Ce(III) towards the chelating sites. Detection limits corresponded to three times the standard deviation of the blank (3σ_B) and amounted to 3.05 and 6.86 μg/L, along with preconcentration factors of 153 and 133 for La(III) and Ce(III), respectively. The robustness of the procedure is demonstrated by the recoveries obtained (>97.5%) for La(III) and Ce(III) in the presence of several cations and anions. The proposed method was satisfactorily applied to the separation of La(III) and Ce(III) from each other and also from U(VI) and Th(IV) by sequential acidic elution and varying pH. The validity of the method was tested by analyzing these metal ions in monazite sand and standard geological materials. The text was submitted by the authors in English.     

Electrochemical oxidation of a tetraester calix[4]arene

The electrochemical oxidation of tetraethyl ester p-tert-butyl calix[4]arene 1 was observed in acetonitrile solution at a platinum electrode, using either cyclic or square wave voltammetry. The oxidation occurred in a number of processes, with the lowest, process I at a peak potential of 1.10 V vs. Ferrocene, being the best defined response. This was attributed to the one-electron oxidation of the aryl ether functionality present in the calixarene and so should provide a route to the electrochemical detection of calixarenes in non-aqueous mixtures. The oxidation behaviour was dependent on the presence of alkali metal cations in solution. Shifts in the oxidation potentials observed were in good agreement with the order of selectivity for the alkali metal cations.     

Supramolecular interaction between water-soluble calix[4]arene and ATP--the catalysis of calix[4]arene for hydrolysis of ATP

The catalysis effect of water-soluble calix[4]arene C[4] (calix[4]arene-5,11,17,23-tetrasulfonate) on hydrolysis of ATP in aqueous solution was studied by HPLC. Using laser photolysis and pulse radiolysis, the supramolecular interaction between water-soluble calix[4]arene and ATP was investigated.     

Binucleating behaviour of a proximally-diphosphinated calix[4]arene

The long diphosphine 5,11-diphenylphosphanyl-25,26-dipropyloxy-27,28-bis(2-propenyloxy) calix[4]arene (cone) (5), in which the two phosphorus atoms are separated by a semi-rigid linking unit, was prepared in four steps starting from calix[4]arene. Reaction of 5 with AuCl(SEt(2)) or [RuCl(2)(p-cymene)](2) led to calixarenes bearing two metallated pendant arms, [5·(AuCl)(2)] and [5·{RuCl(2)(p-cymene)}(2)], respectively. In the presence of AgBF(4) or [Ni(C(5)H(5))(1,5-cyclooctadiene)]BF(4), diphosphine 5 displayed a marked tendency to form oligomeric material, but under high dilution conditions dimeric species were obtained selectively. The inability of 5 to form chelate complexes was further illustrated by its reaction with [PdCl(2)(1,5-cyclooctadiene)(2)], which led quantitatively to a rare complex in which a diphosphine spans across the dinuclear [PdCl(μ-Cl)(2)PdCl] unit.     

Self-assembly of meso-tetrakis(4-N-ethylpyridiniurmyl) porphyrin and tetracarboxyl-phenyl calix[4]arene

Novel dimeric capsules are generated from the noncovalent assembly of 5, 10, 15, 20-tetrakis(4-N-ethylpyridiniurmyl)prophyrin (TEPyP) and tetracarboxyl-phenyl calix[4]arene. The self-assembly system was investigated based on UV-Vis absorption and fluorescent spectra. The factors affecting the interaction process including pH and concentration were examined in detail. The association constants between TEPyP and calix[4]arene were determined by the nonlinear least squares fit. The results showed that the basic medium is favourable to the interaction and electrostatic interaction was determinate in the processes of self-assembly process. The related mechanism was discussed.     

Aminolysis reaction of calix [ 4 ] arene esters and crystal structures and conformational behaviors of calix[4]arene amides

We first make use of aminolysis of calix[4]arene esters to synthesize calix[4]arene amides. When the two ethyl esters of the calix[4]arene esters are aminolysized, the 1, 3-amide derivative is formed selectively. The crystal structures of the calix-[4]arene with two butyl amide (3b) and four butyl amide moieties (4b) were determined. The intermolecular hydrogen bonds make 4b form two-dimensional net work insolid state. The 1H NMR spectra prove that 3b is of a pinched cone conformation, while 4b and tetraheptylamide-calix[4]arene (6b) take fast interconversion between two C2v isomers in solution and appear an apparent cone conformation at room temperature. As decreasing temperature, the interconversion rate decreases gradually and, finally, the interconversion process is frozen at Tc = -10℃, which makes both conformations of 4b and 6b the pinched cone structures. The hydrogen bond improves the interconversion barrier, and the large different values of the potential barrier between 6b and 4b (or 6b) may     

Fluoride sensing with a PCT-based calix[4]arene

Novel calix[4]arene-based anion sensor 1 with two coumarin units attached via amido functions acting also as binding sites is presented. Complexation of F⁻ by PCT-based 1 causes selectively red-shift in UV-vis absorption and in fluorescence emission due to H-bonding followed by deprotonation of NH-amide groups.     

Unsymmetrical calix[4]arene bisporphyrin Pacman

[structure: see text] The synthesis of a Pacman heterobisporphyrin associating an octaethyl porphyrinatozinc (ZnOEP) energy donor and a triaryl porphyrinatozinc (ZntPP) energy acceptor around a calix[4]arene spacer is described. Contrary to previous symmetrical architectures, correlations between the chromophores in the unsymmetrical calixarene bisporphyrin Pacman scaffold can now be observed in ROESY experiments. Independent of the excitation wavelength, only the luminescence of the ZntPP moiety was observed corresponding to quenching of the OEP moiety's emission.     

Preferential axial protonation in a zwitterionic calix[4]arene

[structure: see text] Calixarene 3, substituted at two methylene bridges by dimethylamino groups, exists in the crystal and in polar solvents as a zwitterion, with the axial dimethylamino group protonated.     

Study on thermal decomposition of calix[6]arene and calix[8]arene

Thermal decomposition kinetics of calix[6]arene (C6) and calix[8]arene (C8) were studied by Thermogravimetry analysis (TG) and Differential thermal analysis (DTA). TG was done under static air atmosphere with dynamic heating rates of 1.0, 2.5, 5.0, and 10.0 K min⁻¹. Model-free methods such as Friedman and Ozawa–Flynn–Wall were used to evaluate the kinetic parameters such as activation energy (E _a) and pre-exponential factors (ln A). Model-fitting method such as linear regression was used for the evaluation of optimum kinetic triplets. The kinetic parameters obtained are comparable with both the model-free and model-fitting methods. Within the tested models, the thermal decomposition of C6 and C8 are best described by a three dimensional Jander’s type diffusion. The antioxidant efficiency of C6 and C8 was tested for the decomposition of polypropylene (PP).