ABSORPTIVE IONOPHORES FOR Fe3+ CATION BY PARENT CALIX[n]ARENES

The absorption of Fe³⁺ ion from the aqueous phase to the solid phase was carried out by using p-tert-butyl calix[6]arene (L₁), calix[6]arene (L₂), p-tert-butyl calix[8]arene (L₃), and calix[8]arene (L₄). The effect of varying pH upon the absorption capability of parent calixarenes was examined. It was found that the compounds (L₁, L₂, L₃, and L₄) showed the highest extractability toward Fe³⁺ ion at 4.5–5.4. The calixarene L₂ shows a strong binding ability to Fe³⁺ ion. Based on the continuous variation method, calixarene L₂ formed 1:1 complex with Fe³⁺ ion.     

The Synthesis of Nitrogen-Containing Calixarene Derivatives and their Interactions with Lead Ions

Several new nitrogen-containingcalixarene derivatives have been synthesized andtheir ion-binding properties investigated byUV spectroscopy and solventextraction. These derivatives include5,11,17,23-tetra-t-butyl-25,26,27,28-tetrakis(piperidinocarbonylmethoxy)calix[4]arene (5),5,11,17,23,29,35,41,47-octa-t-butyl-49,50,51,52,53,54,55,56-octa(piperidinocarbonylmethoxy)calix[8]arene (6) and5,11,17,23,29,35,41,47-octa-t-butyl-49,50,51,52,53,54,55,56-octa(N,N-diethyl-car-bamoyl-methoxy)calix[8]arene(7). The UV spectra of and 7revealed they had an ability to transform tight lead picrate ionpairs into separated ones by complexationwith Pb²⁺ in tetrahydrofuran.Both derivatives give 1 : 1 complexes with Pb²⁺. Extraction studies showed that these derivativescould efficiently extract Pb²⁺ (as picrate salts) from the aqueous phase into chloroform. Theextractability of these derivatives were also compared with that ofthe oxygen-containing ester derivative calix[8]arene 2 and the other two nitrogen-containingcompounds 8 and 9.     

Liquid-liquid extraction of transition and alkali metal cations by a new calixarene: Diphenylphosphino calix[4]arene methyl ether

The liquid-liquid extraction of various metal ions by a diphenylphosphino calix[4]arene (1) using picrate counter ion has been studied and compared with those ofp-tert-butyl-calix[4]arene methyl ether (2) and triphenylphosphine (3). The calixarene 1 shows strong binding ability to almost all metal cations examined, but calixarene 2 shows little ability to extract any of them. Based on the continuous variation method, calixarene 1 formed 1: 2 complexes with copper(II) ion.     

Supramolecular Detoxification of Colchicine through Electrochemical Recognition

The complex characteristics of p-sulfonated calix[n]arene and colchicine were examined using various techniques. Cyclic voltammetry indicated that the structural matching and electrostatic interactions were the dominant stabilizing factors for the host–guest complexes. The method showed a long linear voltammetric range for p-sulfonated calix[4]arene from 1?×?10^?8 to 1?×?10^?6?mol?L^?1 with a detection limit of 3?×?10^?9?mol?L^?1. Ultraviolet absorption spectroscopy confirmed that a 1:1 ratio complex was formed. Molecular mechanics showed that the benzene ring of colchicine entered the p-sulfonated calix[4]arene cavity. The solubility of colchicine increased with the p-sulfonated calix[4]arene concentration 50-fold from 0.13 to 6.4?mol?L^?1. The simulation of cell membrane permeability indicated that colchicine was released from the colchicine-p-sulfonated calix[4]arene complex and entered the hydrophobic micelles. These results show that p-sulfonated calix[4]arene is suitable as a drug carrier for colchicine. This work has expanded applications of drug loading, transport, and targeted release for the treatment of gout.     

杯芳烃接枝超细SiO2的制备及其对Cu2+、Ag+萃取性能的研究

通过对杯[4]芳烃以及杯[6]芳烃上缘进行烯丙基化和硅氢加成2步衍生化反应得到硅氢化杯[4]芳烃以及硅氢化杯[6]芳烃,再将这2种硅氢化杯芳烃衍生物分别接枝到超细SiO₂上。在不同的pH值条件下,就2种杯芳烃接枝超细SiO₂衍生物对水合Cu²⁺及Ag⁺的萃取性能进行了研究。结果表明,与对叔丁基杯芳烃相比较,杯芳烃接枝超细SiO₂衍生物对Cu²⁺和Ag⁺的萃取率都有所提高,其中杯[4]芳烃接枝超细SiO₂对Ag⁺的最高萃取率达到98.78%,杯[6]芳烃接枝超细SiO₂对Cu²⁺的最高萃取率达到67.74%。     

Outer-sphere interactions between octahedral chiral cobalt(iii) complexes and water-soluble calixarenes

The structures and stability of outer-sphere associates of sulfonate derivatives of thiacalix[4]arene and calix[4]resorcinarene with coordinatively saturated cobalt(iii) bis- and tris-chelates ([Co(L-His)₂]⁺, [Co(en)₂ox]⁺, [Co(en)₃]³⁺, and [Co(dipy)₃]³⁺) were compared based on the data from UV, CD, 1D ¹H NMR, and 2D (2D NOESY) ¹H NMR spectroscopy and conductometry. Outer-sphere association is accompanied by partial penetration of the chelate rings of the complexes into the hydrophobic cavity of calixarene, which induces changes in the spectroscopic and spectropolarimetric properties of the cobalt(iii) complexes.     

Intermolecular Complexation Between p-Sulfonated Calix[4,6,8]arene Sodium and Neutral Red

The inclusion complexation behavior of the dye guest molecule neutral red with three kinds of water-soluble p-sulfonated calix[n]arene sodium (n=4,6,8) was investigated. p-Sulfonated calix[4,6,8]arene sodium (pSC4, pSC6, pSC8) can react with neutral red to form inclusion complexes, which were confirmed by UV-vis absorption and fluorescence spectroscopy. Fluorescence spectroscopy experiments were performed in pH=4.6 acetic buffer solutions at 25 °C to calculate the stability constants (K _S) for the stoichiometric 1:1 inclusion complexes of pSC4, pSC6 and pSC8 with neutral red. The thermodynamic parameters for the inclusion complexes were determined through a van’t Hoff analysis. Formation of the inclusion complexes of pSC4, pSC6 and pSC8 with neutral red was driven by favorable enthalpic changes with their accompanying negative entropy changes. The complex stability constants monotonically increased with the number of phenolic units in the calixarene ring, which was attributed mainly to electrostatic interactions and hydrogen bonding, rather than to the cavity size.     

Synthesis and Properties of New Thiacalixarene Derivatives with Palladium Ion

Three new thiacalix[4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,27-di(2-hydroxyethoxy)-26,28-dihydroxythiacalix-{}[4]arene (2), 5,11,17,23-tetra-tert-25, 26,27,28-tetrakis[(methylcarboxyl)methoxy]thiacalix[4]arene (3),5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-hydroxy-1-propanoxy)thiacalix[4]arene (4), were synthesized for the first time. The coordination properties of thiacalix[4]arene(1) and its derivatives (2 and 4) were investigated by detecting the interactions betweenthese compounds and two palladium complexes, cis-[Pd(en)(H₂O)₂]²⁺ and cis-[Pd(dtco-3-OH)(H₂O)₂]²⁺, by means of electrospray ionization mass spectrometry (ESI-MS) technique.     

New Calix[4]arene‐Cored Peripherally Functionalized Dendrimers: Synthesis and Conformational Characteristics

New calixarene‐based dendrimers, containing calix[4]arene as the core and different generations of Fréchet‐type poly(benzyl ether) dendrons as building blocks, which possess either Br‐atoms or COO^tBu groups at their surface were synthesized and presented herein for the first time. The new calix[4]arene‐cored dendritic macromolecules were fully characterized and found to prefer strictly the cone conformation.     

The impact of the lanthanide contraction on the structure of complexes of a calix[4]arene trisamide

The syntheses of samarium, holmium, and ytterbium complexes of a tris-amide calix[4]arene are described, and the resulting structures are compared with the previously reported gadolinium complex. The syntheses involved the reaction of 5,11,17,23-tetra-tert-butyl-24-hydroxy-26,27,28-tris(diethylcarbamoylmethoxy)calix[4]arene with the appropriate lanthanide picrate hydrate. Structural studies demonstrated that a picrate anion acts as a quasi-bidentate ligand with Sm (and Gd), is unidentate in the Ho complex, but is found in the second coordination sphere for the smallest lanthanide cation (Yb) investigated.     

Solid State Confinement of Ferrocene by Calixarenes

Combinations of ferrocene with unsubstituted calix [n]arenes, n =4 and 5, in toluene afford crystalline inclusion complexes (calix[4]arene) ₃ (ferrocene) [hexagonal, a =14.7797(4), c =18.4400(4) Å, P6M₃/m , ρ = 1.389 g.cm ^?1 , Z =2, R ₁ =0.0963 (on 1401 observed data [ I >2 σ ( I )])] as a lattice-type inclusion complex, and (calix[5]arene)(toluene) _0.55 (ferrocene) _0.45 [monoclinic, a =9.6908(8), b =15.069(1), c =22.957(1) Å, β = 90.155(5)°, P2₁/m , ρ =1.318 g.cm ^?1 , Z =4, R ₁ =0.1005 (on 3130 observed data [ I >2 σ ( I )])], that shows endo -cavity complexation of ferrocene by the calixarene.     

Calix[n]arene/Ti(IV) complexes as active catalysts in aldol reaction of Chan's diene

The aldol condensation of Chan's diene with benzaldehyde is catalyzed by only 8% mol of the calix[n]arene/Ti(O-i-Pr)₄ complexes. Studies have revealed that the size of calixarene molecule and the number of hydroxyl groups affected the efficiency of the reaction. The reaction conditions (solvent and temperature) have been examined.     

Chromophoric Water-Soluble Tetrakis(4-Carboxyphenylazo)-calix[4]arene: Binding of Arylammonium Ions and Benzene

The interaction of water-solubletetrakis(4-carboxyphenylazo)calix[4]arene with N,N,N trimethylarylammoniumiodides and benzene was investigated in order to correlate the effect ofanilinium salts on the binding properties of the cup-shaped hydrophobiccavity with the monolayer spreading behavior of a series of amphiphilicanalogs. Whereas multiple binding is observed for N,N,N-trimethylaniliniumiodide and benzene, NMR titration oftetrakis(4-carboxyphenylazo)calix[4]arene withN,N,N-trimethyl-N-(2-naphthyl)ammonium iodide indicates 2 : 1 complexationwithin the cavity of the calixarene with binding constants of K₁ = 8024 M^-1and K₂ = 3134 M^-1.     

Pyrazole Based Mono‐ and Di‐Substituted Half Sandwich d6 Platinum Group Metal Complexes: Synthesis and Spectral Characterization

Reactions of pyrazole based ligand and halide bridged arene d⁶ metal precursors resulted a series of mono and di‐substituted pyrazole based half sandwich d⁶ metal complexes. In general, they are formulated as [(arene)MLCl₂] [M = Ru, arene = benzene ( 1 ), p‐cymene ( 2 ), arene = Cp*, M = Rh ( 3 ) and Ir ( 4 )] and [(arene)ML₂Cl] [M = Ru, arene = benzene ( 5 ), p‐cymene ( 6 ), arene = Cp*, M = Rh ( 7 ) and Ir ( 8 )]. All these complexes were characterized by various spectroscopic techniques (IR, ¹H NMR, ESI‐MS, and UV/Vis). The molecular structures were confirmed by single‐crystal X‐ray diffraction technique. Spectroscopic studies revealed that complexation i.e., mono‐ and di‐substitution occurred by the ratio‐based reaction between pyrazole ligand and metal precursor through the neutral nitrogen rather than protic nitrogen. In these complexes deprotonation of the protic nitrogen does not occur unlike the other complexes containing pyrazole derivatives, in which the pyrazole ligand is anionic.     

Calixarene-based metalloporphyrins: molecular tweezers for complexation of DABCO

We investigated the formation of host-guest complexes between zinc porphyrins covalently attached to calixarenes via amidic bonds and a small bidentate ligand bearing two nitrogen atoms. Depending upon the calixarene structure (S vs CH₂ bridges), the ligand 1,4-diazabicyclo[2.2.2]octane (DABCO) is complexed by metalloporphyrin units by two different ways. While the thiacalix[4]arene prefers an intramolecularly closed cavity with a binding constant of (1.0±0.1)×10⁷ M⁻¹ in CHCl₃ at 294 K (stoichiometry 1:1), the classical calix[4]arene forms a complex by ligation of both porphyrin units separately (stoichiometry 2:1). The differences observed can be rationalized in terms of cavity size and the preorganization due to intramolecular hydrogen bonding of the calixarene lower rim.     

Structures and properties of solvated and unsolvated isopropyl functionalised calix[4]arenes

The tetra-isopropyl ethers of calix[4]arene and p-t-butylcalix[4]arene have been isolated in the cone conformation, and structurally characterised as chloroform solvates. Thermogravimetric analysis demonstrated that the parent isopropylcalix[4]arene solvate is significantly more stable than the p-t-butylcalix[4]arene analogue, retaining the solvent up to a temperature of 125°C. It was found that the calix[4]arene ether sublimes at atmospheric pressure, and solvent-free crystals appropriate for structure determination were produced at reduced pressure. The p-t-butylcalix[4]arene ether was also isolated without solvent in the lattice, but in this case the calixarene was crystallised from acetone, as sublimation did not produce crystals of sufficient quality.     

Synthesis and study of binuclear calix[4]arene Schiff base Co(II) complexes as catalyst in the presence of PhIO for the catalytic oxidation of olefin

The binuclear Co(II) complexes of calix[4]arene substituted 2-vanillin (R₁) and 2-hydroxy naphthaldimine (R₂), Schiff bases (Co₂L¹ and Co₂L²) have been synthesized, characterized and employed as models to mimic monooxygenase in the catalytical oxidation of olefins. The kinetic mathematical model (oxygen rebound mechanism) for olefin cleavage catalyzed by the complexes has been proposed. The results show that, compared to the calix[4]arene-free analogous, the mono and multinuclear complexes of calix[4]arene Schiff bases as catalyst exhibit high activity in the olefin catalytic oxidation.     

Electrochemical properties of outer-sphere associates of bipyridyl and sepulchrate metal complexes with (thia)calix[4]arenes

The electrochemical one-electron reduction (oxidation) of bipyridyl metal complexes ([Co(bipy)₃]³⁺, [Cr(bipy)₃]³⁺, [Fe(bipy)₃]²⁺, [Ru(bipy)₃]²⁺ (as well as Co(III) sepulcrate)) with water-soluble (thia)calix[4]arenes has been studied by means of cyclic voltammetry. It has been shown that [M(bipy)₃]^3+/2+ bind to (thia)calix[4]arenes via sulfonate groups of the upper rim. Oxidized forms bind stronger than reduced ones leading to reduction (oxidation) of half-wave cathodic shift. The effect of predominant stabilization of oxidized forms of metal complexes for carboxylated calix[4]arene is stronger than for thiacalix[4]arene (ΔΔG₀?=???7.8?÷???12.5 and ??3.7 kJ/mol, respectively). The redox-switchable outer-sphere binding of Co(III) sepulchrate via lower rim of carboxylated calix[4]arene has been revealed using cyclic voltammetry. The binding constants of outer-sphere associates based on calix[4]arenes and unstable metal complexes ([Co(sep)]²⁺, [Ru(bipy)₃]³⁺, [Co(bipy)₃]²⁺) have been calculated for the first time using ¹H NMR titration and cyclic voltammetry data.

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Polymer Supported Calix[4]arene Schiff Bases: A Novel Chelating Resin for Hg2+ and Dichromate Anions

This article describes the synthesis and characterization of two new calix[4]arene Schiff bases and their polymeric resins. The extraction properties of these “proton switchable extractants” with alkali, transition, post transition metal cations and for dichromate anions are reported. The two new calix[4]arene based Schiff bases (5 and 6) have been synthesized from 5,17‐diformyl‐25,27‐dipropoxy‐26,28‐dihydroxycalix[4]arene (4) by treatment with 3‐amino‐methylpyridine and 1,8‐diaminooctane in two separate reaction flasks following the same procedure. Compounds 5 and 6 have been appended to a polymeric resin by treatment with Merrifield resin through a nucleophilic substitution reaction. The receptor compounds (3 and 5–8) do not extract alkali metal cations, but show some selectivity toward transition metal cations, and a particularly high selectivity to Hg²⁺ and Pb²⁺. The protonated forms of all of the calixarene‐based receptors are good extractants for transferring Cr₂O₇ ^2?/HCr₂O₇ ^? anions from an aqueous into a dichloromethane layer.