Synthesis and binding properties of polymeric calix[4]arene nitriles

Two new polymers containing pendant calix[4]arene units with nitrile functionalities at their lower rim have been synthesized via radical initiated reactions involving a vinylic monomer 6 {5,11,17,23-tetra-tert-butyl-25,26,27-tris(cyanomethoxy)-28-(2-acryloyloxy) ethoxycalix[4]arene} and with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. The complexation studies were made by using liquid–liquid extraction procedures. It has been deduced from the observations that both polymers show a good selectivity towards Hg²⁺ like their precursor 5,11,17,23-tetra-tert-butyl-25,26,27-tricyanomethoxy-28-(2-hydroxy)ethoxycalix[4]arene 5, which supports their utility as adsorbents or potential candidate materials for fabricating membranes and sensors, which can separate or detect Hg²⁺ metal ions in a high selectivity.     

Electrochemical behavior of p-tert-butyl calix[8]arene in CH2Cl2

The electrochemical behavior of p-tert-butyl calix[8]arene has been investigated by cyclic voltammetry. The result shows that there is an irreversible electrochemical oxidative wave when the potential ranges from −0.3 to 1.6 V versus Ag/0.1 M AgNO₃ in acetonitrile (Ag/Ag⁺). At 25 °C, the peak potential is ca. 1.43 V (versus Ag/Ag⁺) at scan rate of 0.05 V s⁻¹. The number of the electrons transferred in the electrochemical reaction is four. The diffusion coefficient of p-tert-butyl calix[8]arene is 2.8 × 10⁻⁵ cm² s⁻¹. The diffusion activation energy is 12.3 kJ mol⁻¹.     

Spectrophotometric and electrochemical behavior of a novel azocalix[4]arene derivative as a highly selective chromogenic chemosensor for Cr

In this study, a novel azocalix[4]arene derivative, 5,11,17-tris[(1-naphtyl)azo]-25,26,27,28-tetrahydroxy-calix[4]arene (NAC4) bearing napthyl groups on the upper rim was synthesized. Its complexation behavior for alkali, alkaline-earth and various heavy metal ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Hg²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Co²⁺, Fe²⁺, Cr³⁺, Ag⁺) was investigated by spectroscopic and voltammetric methods. This chemosensor exhibits decreased absorbance in the presence of Hg²⁺ and a unique absorbance quenching effect only for Cr³⁺. In addition, a new absorption band centered at 565 nm with the formation of the 1:1 host–guest complex (Cr³⁺-NAC4) was observed in the case of Cr³⁺, leading to an obvious color change from light orange to dark lilac. In voltammetric experiments, Cr³⁺ ions decreased voltammetric peaks of NAC4, whereas no significant changes occurred in the presence of the other metal ions. The Benesi–Hildebrand method was used to determine a logarithmic value of 3.76 for the association constant of the complex between Cr³⁺ and NAC4.     

Modification of poly acrylic acid using calix[4]arene derivative for the adsorption of toxic heavy metals

Poly acrylic acid (PAA) was grafted with p‐t‐butyl calix[4]arene diamine (distal cone) (2) to adsorb toxic heavy metal and alkali metal cations. The grafting method includes the amidation reaction of PAA with calixarene diamine derivative 2 which was carried out in N,N‐dimethylformamide (DMF) and N–methyl‐2‐pyrrolidone (NMP) as solvents. The modified PAAs (PAA‐C1 and PAA‐C2) were characterized by FTIR, ¹H‐NMR, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). PAA‐C1 and PAA‐C2 were used to evaluate the sorption properties of some toxic heavy metal cations (Co²⁺, Cu²⁺, Cd²⁺, Hg²⁺), alkali metal cations (Na⁺, K⁺, Cs⁺), and Ag⁺. Results showed that the modified PAAs were good sorbents for heavy metal and alkali metal cations. The main goal of this project is to design hydrophobically modified PAA that is suitable for ion selective membranes and chemical sensor devices for adsorption of toxic heavy metals. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of new optically active polymers carrying calix[4]arene and amino acid units in the main chain and their binding properties towards toxic heavy metals

BACKGROUND: A series of novel optically active polymers containing upper rim calix[4]arene was prepared from the polycondensation reaction of calix diamine derivative 2 with two optically active diacid chlorides. RESULTS: The optically active compounds were prepared from the reaction of a pyromellitic dianhydride with two chiral amino acids. The optically active polymers were obtained in a yield of 80–86% and had an inherent viscosity of 0.20–0.26 dL g^?1. The polymers were characterized using Fourier transform infrared and ¹H NMR spectroscopy and elemental analysis. Studies of the complexation of the polymers towards some alkali metal and toxic transition metal cations were performed using solid–liquid sorption procedures and comparisons made with the starting monomer. CONCLUSION: It is evident from the complexation studies that the polymers investigated are good polymeric ionophores for alkali metal cations like Na⁺ and K⁺, for Ag⁺ and for toxic heavy metal cations such as Cu²⁺, Co²⁺, Cd²⁺ and Hg²⁺. These polymers are good candidates for use in chiral stationary phases for separation of enantiomers in ionic media, as well for removing metal ions. Copyright © 2009 Society of Chemical Industry     

Novel linear molecular aggregation tethered by hydrogen-Bonded interaction within the crystalline calix[4]arene derivatives

Single crystals of two calix[4]arene derivatives, that is, 5,11,17,23-tetra-tert-butyl- 25,27-bis[2-[N-(3-methoxy-4-methoxy-benzylidene)-amino]ethoxy]-26,28- dihydroxy calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[3- pyridine carbonyl-amino]ethoxy]-26,28-dihydroxy calix[4]arene (2), were prepared and their crystal structures have been determined by X-ray crystallographic study. As compared with calix[4]arene derivative 1 possessing CN functional group, compound 2 bearing the NH group could form not only intermolecular hydrogen bonds between the hydrogen atom in NH group and the oxygen atom in CO of an adjacent calix[4]arene molecule, but also intramolecular hydrogen bonds between the N—H⋯OC moieties in solid state, giving a rare linear molecular aggregation.     

Electrochemical response of ferrocenium filled calix[4]arene capsules in solution and immobilized on gold

Hydrogen-bonded dimers of tetra-urea calix[4]arenes are able to include ferrocenium ions as a guest. Heterodimeric capsules are exclusively formed in 1:1 mixtures of tetra-arylurea calix[4]arene 1 with tetra-tosylurea calix[4]arene 2. Sulfide groups attached via spacers on the urea rim of 1 allow their binding to metal surfaces rendering simultaneously their dissociation more difficult. Thus, the electrochemical response of encapsulated ferrocenium could be studied in a self-assembled monolayer (SAM) in addition to the solution electrochemistry with cyclic voltammetry. The stability of the electrochemically active monolayers was tested after a heat treatment (225 °C for 30 min in N₂ atmosphere) and multiple cycling (up to 1200 cycles), which could be required for a possible application as molecular based information storage.     

1,3-ALTERNATE-THIACALIX[4]ARENE-BASED DIMER: SYNTHESIS AND INCLUSION BEHAVIOR

Synthetic approaches to flexible and adaptable thiacalix[4]arene dimer, in which the thiacalix[4]arene units constrain 1,3-alternate conformation, by molecular assembly are presented. The thiacalix[4]arene dimer shows high affinity toward Cs⁺ and K⁺ ions. Encapsulation of Cs⁺ by the internal cavity of the dimer strongly suggests that the size match factor drives the process. On the other hand, the K⁺ is encapsulated by the thiacalix[4]arenes units by supramolecular interaction (cation-π).     

A useful approach toward the synthesis and metal extractions with polymer appended thioalkyl calix[4]arenes

This article describes a convenient method for the synthesis of two new polymeric resins via nucleophilic substitution reactions involving 5,11,17,23-tetrakis[(propylthio)methyl]-25,26,27,28-tetrahydroxycalix[4]arene 4, and 5,11,17,23-tetrakis[(methylthio)methyl]-25,26,27,28-tetrahydroxycalix[4]arene 6, as precursors with Merrifield's resin. The extraction studies were made using both liquid-liquid extraction and solid-liquid batchwise sorption procedures. The calix[4]arene based polymeric resins have high extraction ability toward metal cations and Na₂Cr₂O₇ as compared to their monomeric precursors.     

Electrochemical oxidation of <Emphasis Type="Italic">p</Emphasis>-sulfonated calix[8]arene

The water-soluble p-sulfonated sodium salt of calix[8]arene (III) was synthesized. The product was characterized by FT-IR, NMR and UV–Vis spectra.Then the electrochemical behaviors of p-sulfonated sodium salt of calix[8]arene in NaAc+HAc (pH = 4) buffer solution was studied. In aqueous solution, p-sulfonated calix[8]arene can be oxidized when the potential is more than 0.7 V vs SCE. It was confirmed that the reaction was a two-electron irreversible electrochemical reaction. The transfer coefficient, α, was measured as 0.7. At 25°, the diffusion coefficient of p-sulfonated calix[8]arene was determined as 8.6 × 10⁻⁷ cm² s⁻¹. The diffusion activation energy of p-sulfonated calix[8]arene was 18.9 kJ mol⁻¹ at pH = 4.     

Highly Lipophilic,Mono-ionizable Calix[4]arene-benzocrown-6 Extractants for Removal of Radiocesium from Nuclear Wastes

A series of lipophilic, proton-ionizable calix[4]arene-benzocrown-6 compounds with calixarene units locked in the 1,3-alternate conformation was prepared for evaluation of their potential as radiocesium ion extractants. Upon ionization of the pendant acidic function, the ligand provides the requisite anion for the formation of an electroneutral extraction complex, thereby markedly increasing Cs⁺ extraction efficiency. To enhance the lipophilicity, each proton-ionizable calix[4]arene-crown-6 ligand bears a (2-ethylhexyl)benzo unit and two octyl groups. By use of radiotracer techniques for Cs⁺ and Na⁺ and ICP spectrometry for K⁺, the ligands were evaluated in terms of the efficiency and selectivity with which they extract Cs⁺ from aqueous solutions into toluene. Supplementary materials are available for this article. Go to the publisher's online edition of Solvent Extraction and Ion Exchange to view the supplementary file.     

Methacrylated calix[4]arene phosphonic acids as functionalized crosslinker for radical polymerization

We describe the synthesis of 5,11,17,23‐tetra‐tert‐butyl‐25,27‐dioxypropylphosphonic acid‐26,28‐dimethacryloyloxy‐calix [4]arene and 5,11,17,23‐tetra‐tert‐butyl‐25‐oxypropylphosphonic acid‐27‐hydroxy‐26,28‐dimethacryloyloxy‐calix[4]arene starting from para‐tert‐butyl‐calix[4]arene. The complete reaction was proved by matrix‐assisted laser desorption ionization time of flight mass spectrometry and nuclear magnetic resonance spectroscopy. The influence of these compounds on the kinetics of the radical polymerization of methyl methacrylate was shown by dilatometry. Furthermore, the adhesive properties of dental adhesives containing these calix[4]arene derivatives were investigated. Copyright © 2012 Society of Chemical Industry     

Synthesis and evaluation of extraction ability of calix[4]-crown-6 cone conformer and its oligomeric analogue

The synthesis of the cone conformers of 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-nitrobenzyloxy)-26,28-dihydroxy]-calix[4]-arene (2), 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-nitrobenzyloxy)]calix[4]arene-crown-6 (3) and 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-aminobenzyloxy)]calix[4]arene-crown-6 (4) containing polymerizable side arms, along with their oligomeric analogue 5, is reported. Extraction studies with monomers 3 and 4 and the oligomer 5 show no difference in their extraction behavior and selectivity, whereas, ionophore 2 is a poor extractant for alkali metal cations. These observations suggest that, substitution of side arms on the lower rim of calix moiety can enhance the calix[4]-crown-6 cone conformers function to extract alkali metal cations in two phase extraction systems.     

Calix[4]arene‐tetranitrone as crosslinker in dental composite materials

The synthesis of a functionalized calix[4]arene bearing 1,3‐dipolaric nitrone groups ( 5 ) has been carried out. The reaction of N‐methylhydroxylamine or N‐propylhydroxylamine with the carbonyl group of 5,11,7,23‐tetraformyl‐25,26,27,28‐tetraalkoxycalix[4]arene leads to calix[4]arenes bearing a nitrone function at each of the four para‐positions. Via 1,3‐dipolar cyclo‐addition of acrylic acid methyl ester with the nitrone functions of 5 , subsequently an upper rim‐substituted tetraisoxalidinecalix[4]arene is quantitatively synthesized. Further, the minimization of shrinkage of a dental filling depending on the amount of calix[4]arene‐tetranitrone is discussed. Copyright © 2011 Society of Chemical Industry     

氨基硫脲基新型杯[4]芳烃衍生物的合成

通过1,3-环氧丙基杯[4]烃与硫代氨基脲开环反应,合成硫代氨基脲基杯[4]芳烃衍生物,研究了其对阳离子的吸附性能后发现,与其他氨基杯芳烃相比,该衍生物对铜离子的吸附性能较好,并且有很好的选择性。     

Synthesis,extraction, and adsorption properties of calix[4]arene‐poly(ethylene‐glycol) crosslinked polymer

Novel calix[4]arene‐poly(ethylene glycol) crosslinked polymer (CCP) has been synthesized by the polycondensation reaction between a p‐tert‐butylcalix[4]arene derivative and dihydroxyl capped poly(ethylene glycol) (DHPEG, M_n = 1000) catalyzed by neodymium tosylate. The hydrogel, consisted of 66.9% water and 33.1% CCP, can selectively extract aromatic organic molecules from aqueous solution according to the diameter of the guest molecules, which infers that the diameter of the calix[4]arene cavity is about 5.4 Å and the conformation of calix[4]arene units altered from cone conformation to 1,3‐alternate conformation during the polycondensation reaction. Furthermore, CCP can also adsorb naphthalene from gas phase, showing much higher capacity than active carbon does, which may have some potential applications in the field of separation and environment protection. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chromogenic sensing of Cu(II) by imino linked thiacalix[4]arene in mixed aqueous environment

Thiacalix[4]arene based imino receptors 4–5 carrying azophenol appendage have been synthesized and studied for their binding abilities towards different metal ions (Li⁺, Na⁺, K⁺, Cd²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺ and Hg²⁺). Receptor 4 showed selective chromogenic sensing for Cu²⁺ ions in mixed aqueous conditions (THF:H₂O, 9:1 v/v).     

Multiwalled carbon nanotube-4-tert-butyl calix[6]arene composite electrochemical sensor for clenbuterol hydrochloride determination by means of differential pulse adsorptive stripping voltammetry

The electrochemical behavior of clenbuterol hydrochloride (CLB) was studied at a multiwalled carbon nanotube-4-tert-butyl calix[6]arene composite chemically modified electrode by means of cyclic voltammetry, electron impedance spectroscopy, and differential pulse adsorptive stripping voltammetry. Surface characterization of the electrode was carried out by means of SEM. The results revealed that 4-tert-butyl calix[6]arene along with multiwalled carbon nanotubes demonstrated a high sensitivity for determination of CLB. Employing differential pulse adsorptive stripping voltammetry allowed a linear response over the concentration range of 1.99?×?10^?8–4.76?×?10^?5?M with a detection limit of 1.38?×?10^?9?M for CLB. The described method has been applied for the estimation of CLB in biological fluids such as urine and serum.     

几种新型杯[4]芳烃衍生物的合成

以对叔丁基苯酚为起始原料,通过缩合、一步取代反应合成了对叔丁基杯[4]芳烃的衍生物,两步取代反应合成了对叔丁基杯[4]芳烃的衍生物。用FT-IR,^1HNMR,FAB-MS对产物的结构进行了表征。     

Extraction of Pb2+ with p-tert-butylcalix [4]-, [5]-, [6]Arene Carboxylic Acid Ligands and their Monomeric Counterpart: A Thermodynamic Approach

Studies on extraction equilibrium constants at different temperatures and thermodynamic parameters of solvent extraction of Pb²⁺ ion with carboxylic acid derivatives of different ring size calixarenes and structure related monomeric compound have been carried out. The extraction equilibrium constants corresponding to calix[n]arene (n?=?4, 5, 6) derivatives decrease in the order [5]arene > [6]arene > [4]arene. In all cases, the complexation process is primarily enthalpy driven. The favorable enthalpic contribution for extraction of Pb²⁺ is in the order hexamer ≈ monomer > tetramer > pentamer. However, the unfavorable entropic loss follows the order: monomer > hexamer > tetramer > pentamer. Overall stability of the host-guest complex is the function of entropy-enthalpy compensation and the free energy of complexation is minimum for the pentamer, followed by tetramer ≈ hexamer and monomer. Although the carboxylic acid derivative of calix[4]arene is more preorganized than the calix[5]arene derivative, extraction of Pb²⁺ ion with the tetramer passes through greater entropic loss than that with the pentamer and the degree of preorganization of calix[4]arene derivative is far from perfect for the complexation and extraction of Pb²⁺ ion. As compared to tetrameric and hexameric counterparts, the structural features of the carboxylic acid derivative of calix[5]arene prior to complexation contribute much to interact with the Pb²⁺ ion and form a thermodynamically stable complex. Supplementary materials are available for this article. Go to the publisher's online edition of Solvent Extraction and Ion Exchange to view the supplemental file.