Removal of Chromium Anions with Nanofiltration-Complexation by Using p-Sulfonated Calix[4]arene

This article describes the removal of chromium anions from aqueous solutions by using nanofiltration-complexation consisting of pilot-scale nanofiltration equipment (Osmonics Sepa CF Membrane Cell) and water-soluble p-sulfonated calix[4]arene ligand. For the determination of optimum removal conditions of the chromium anions, the effect of pH, ligand cavity size, and foreign anions on the retention of the chromium anions in nanofiltration-complexation system was also evaluated. The results showed that water-soluble p-sulfonated calix[4]arene was an effective and selective ligand for the chromium anions over Cl^? , SO₄ ^2 ?  and NO₃ ^?  anions in nanofiltration-complexation system at pH 9.4.     

一对含有苯甲醛基修饰的杯芳烃异构体的晶体结构以及它们与铽离子配位的光物理性质

Two calix[4]arene isomers with benzaldehyde moieties, i.e., 5,11,17,23-tetra-tert-butyl-25,27-bis[2-(o-formyl-phenoxy)ethoxy]-26,28-dihydroxycalix[4]arene (3) and 5,11,17,23-tetra-tert-butyl-25,27-bis[2-(p-formylphenoxy)-ethoxy]-26,28-dihydroxycalix[4]arene (4), were synthesized according to a newly designed route in high yields, and their crystal structures have been determined by X-ray crystallographic study. The photophysical behavior on complexation of calix[4]arene derivatives 3 and 4 with terbium(Ⅲ) nitrate was investigated in anhydrous acetonitrile at 25℃ by UV-Vis and fluorescence spectroscopies. The crystallographic structure of 3 indicated that the eight oxygen atoms formed a preorganized ionophoric cavity due to intramolecular π-π stacking, which could encapsulate lanthanide ions tightly. In sharp contrast, the compound 4 formed a linear array by intermolecular π-π stacking, hence the oxygen atoms of pendant arms could not coordinate with metal ions, giving a poor binding ability to Tb^3 . The absorption spectra of 3 with Tb^3 showed clearly a new broad intense absorption at 385nm. Interestingly, the narrow emission line spectrum has also been observed for compound 3 with Tb^3 , and the results obtained were discussed from the viewpoint of energy transfer mechanism between host structures and the properties of lanthanide ions.     

Cation- and anion-assisted binding of triethylenediamine by zinc bisporphyrinates

The complexation of zinc calix[4]arene or calix[4]pyrrole bisporphyrinates with alkali metal cations, halide anions, and triethylenediamine was studied by ¹H NMR spectroscopy. It was established that the binding of molecules and/or charged particles by various fragments of calix[4]arene and calix[4]pyrrole porphyrins are interrelated processes. This makes it possible to use one process (for example, complexation of the calix[4]arene fragment of the macrocycle with alkali metal cations or complexation of the calix[4]pyrrole fragment with halide ions) as a tool for controlling another process (complexation of the porphyrin fragments of the macrocycle with neutral molecules).     

Novel Ca-selective merocyanine-type chromoionophore derived from calix[4]arene-diamide

The synthesis and calcium-selective chromogenic ion binding properties of benzothiazolium derivative of calix[4]arene are described. The merocyanine-type ionophore derived from calix[4]arene-diamide showed selective chromogenic properties toward Ca²⁺ ions in aqueous methanol. The compound showed significant Ca²⁺ ion dependent changes in UV-vis spectral properties in the presence of other physiologically important metal ions (Na⁺, K⁺, and Mg²⁺). The pH sensitive chromogenic behavior also suggests that the compound can be used as a sensitive pH indicator around pH 6.5.     

para‐Sulfonated Calixarenes Used as Synthetic Receptors for Complexing Photolabile Cholinergic Ligand

The water‐soluble tetra‐, hexa‐ and octasulfonated calix[4]arenes, calix[6]arenes, and calix[8]arenes 1 – 3 , respectively, were investigated as potential synthetic receptors for photolabile cholinergic ligand A , a photolytic precursor of choline. Ligand A is a bifunctional molecule carrying a photolabile 2‐nitrobenzyl group at one end and a choline moiety at the other end. Results from NMR studies have shown that calixarenes 1 – 3 form stable 1 : 1 complexes with A , having similar binding potential to that observed with the cholinergic enzymes acetylcholinesterase and butyrylcholinesterase. Further studies have suggested that calix[8]arene forms a ditopic complex by binding concomitantly to both the cationic choline moiety and the aromatic photolabile group of A , whereas calix[4]arene and calix[6]arene form monotopic complexes with A . The ditopic complex between calix[8]arene and A results from mutually induced fitting process, while the monotopic complexes between calix[4]arene and A can be regulated by pH: at neutral pH, calix[4]arene specifically binds the cationic choline moiety, while, at acidic pH, it complexes unselectively both the cationic choline moiety and the aromatic group of A . Our results show that para‐sulfonated calixarenes are versatile artificial receptors which bind in various ways to the bifunctional photolabile cholinergic ligand A , depending on their size, geometry, and state of protonation.     

新型间苯二酚杯芳烃硫脲衍生物对阴离子的识别

通过间苯二酚杯芳烃连续三步反应, 以较高产率合成了分子中连有8个和12个硫脲端基的间苯二酚杯芳烃的酰胺衍生物. 用紫外可见光谱法研究了两个代表性化合物4,6,10,12,16,18,22,24-八[6-(苯基硫脲基)-己氨甲酰基甲氧基]-2,8,14,20-四苯基杯[4]间苯二酚芳烃(THBC)和4,6,10,12,16,18,22,24-八[2-(苯基硫脲基)-1-甲基乙基-1-氨甲酰基甲氧基]-2,8,14,20-四苯基杯[4]间苯二酚芳烃(TPBC), 对各种阴离子(AcO^－, H₂PO₄^－, HSO₄^－, H₂PO₄^2－, C₁₂H₂₅-C₆H₄-SO₃^－, Cr₂O₇^2－, B₄O₇^2－, Cl^－, Br^－)的识别性能, 结果表明它们对AcO^－, H₂PO₄^－, HSO₄^－等阴离子有较好的配位作用, 能形成1∶3的配合物.     

Luminescence behavior of a water soluble calix[4]arene derivative complex with terbium ion(III) in gelation solution

The complexation luminescence behavior of a water soluble calix[4]arene derivative, 5,11,17,23-tetra-sulfonate-25,26,27,28-tetra-carboxymethoxycalix[4]arene (L) with lanthanoid ion (Tb(3+)) has been investigated in gelation solution at 25 degrees C by using UV-vis and fluorescence spectra. The results obtained indicated that the water soluble calix[4]arene derivative can form an efficient energy transfer complex with terbium ion(III). The fluorescence of L x Tb(3+)complex is partially quenched by gelatin in gelation solution. The quenching intensity is related to the concentration and the hydrolysis degree of gelatin. Absorption and fluorescence spectra analysis show that the -COO(-) groups on gelatin have a definite binding ability to Tb(3+), and then, gelatin could compete binding with calix[4]arene derivative upon complexation with Tb(3+), leading to the relative fluorescence quenching of the formation complex of terbium(III) ion with calix[4]arene derivative.     

Calix[4]arene based molecular probe for sensing copper ions

A novel calix[4]arene based molecular probe for metal ions has been designed, synthesized and evaluated. Studies on its binding with different metal ions reveal a noticeable naked eye color change, bathochromic shift in absorption spectrum and remarkable enhancement in fluorescence emission in the presence of Cu²⁺ only. The role of calix[4]arene scaffold for selective recognition of Cu²⁺ has been demonstrated by repeat evaluation and analysis of an appropriate reference molecule. A rational explanation for fluorescence enhancement in 3 on interaction with copper has been suggested.     

Phenyl-calix[4]arene-based fluorescent sensors: cooperative binding for carboxylates

Tetrakis-(4-carbamoylphenyl)-substituted and tetrakis-(4-amidophenyl)-substituted calix[4]arenes as well as the monomeric biphenylcarbamate have been synthesized as fluorescent receptors for anion sensing. Their binding properties with various anions including F-, CH3COO-, Ph-COO-, and H2PO4- were investigated by fluorescence titrations, Job plot experiments, 1H NMR spectroscopies, and ESI-MS measurements. Importantly, we have found that calix[4]arene-based sensors exhibit greatly enhanced binding affinity and selectivity toward carboxylates. The binding associations of tetrakis-(4-carbamoylphenyl)-substituted calix[4]arene for carboxylates are 1-2 orders of magnitude greater than those of the monomeric biphenylcarbamate sensor. Such an enhancement in the binding affinity and selectivity is attributed to the cooperative binding of the multiple ligating groups as revealed from the ab inito DFT calculations. Although tetrakis-(4-amidophenyl)-substituted calix[4]arene exhibited relatively weaker binding affinity toward anions, its superior binding selectivity for acetate ion over fluoride ion is evident. Our results also suggest that carbamate functionality is a useful H-bond donor for hydrogen-bonding interactions in molecular recognition and supramolecular chemistry.     

Fluorescence switch-on sensor for Cu by an amide linked lower rim 1,3-bis(2-picolyl)amine derivative of calix[4]arene in aqueous methanol

A highly selective fluorescence switch on sensor, L for detecting Cu²⁺ has been synthesized by introducing a bis-(2-picolyl)amine moiety at the lower rim of a calix[4]arene platform via amide linkage. Binding properties of L toward ten different biologically relevant Mⁿ⁺ ions have been studied by fluorescence and absorption spectroscopy in methanol and aqueous methanol. L was found to detect Cu²⁺ selectively down to a concentration of 196 and 341 ppb, respectively, in methanol and 1:1 aqueous methanol even in the presence of other metal ions. The composition of the complex has been found to be 1:1 based on the Job plot and is further confirmed by ESI MS. The role of calix[4]arene platform as well as the pre-organized binding core in the selective recognition of Cu²⁺ has been demonstrated by studying appropriate reference molecules. The possible modes of binding of L with Cu²⁺ have been modeled by computational calculations. L and its Cu²⁺ complex could very well be differentiated based on the nano-structural features observed in SEM and AFM.     

Anion‐binding properties of two calix[4]arene derivatives containing two ferrocene imine or ferrocene amine units at the upper rim

Calix[4]arene derivatives containing ferrocene units at the upper rim have been synthesized and their anion‐binding and sensing investigated towards anions such as chloride, bromide and hydrogen sulfate by cyclic voltammetry. Electrochemical studies show that these redox‐active ligands electrochemically recognize chloride and bromide anions. These compounds have excellent selectivity for chloride and bromide ions, in the comparison with hydrogen sulfate anion. With ferrocenyl Schiff base calix[4]arene 1 an anodic shift as large as 302 mV is observed on addition of four equivalents of Cl⁻ anion. Also electrochemical and UV–vis spectroscopic titrations ferrocenyl calix[4]arene derivatives 1 with chloride and bromide ions and 2 (only with Cl⁻) indicate a 1:1 binding‐stiochiometry. Copyright © 2011 John Wiley & Sons, Ltd.     

Complexation of Calix[4]arene With Alkali Metal Cations: Conformational Binding Selectivity and Cation-π Driven Inclusion

Hartree-Fock, second order Møller-Plesset perturbation theory, and density functional theory calculations were carried out to analyse the complexation of calix[4]arene with cationic species including H + and the alkali metal cations (Li + , Na + , K + , Rb + , and Cs + ). Special emphasis has been placed on conformational binding selectivity, and on the structural characterization of the complexes. Li + and Na + cations are located in the calix[4]arene lower rim. The larger cations (K + , Rb + , and Cs + ) complex preferentially with the calix[4]arene cone conformer, and their endo (inclusive) complexation is driven by cation- ~ interactions, leading in the case of K + to a structure that reflects a preferential interaction with two phenol rings. The endo complexation of Cs + with calix[4]arene is in agreement with X-ray diffraction data.     

BODIPY appended cone-calix[4]arene: selective fluorescence changes upon Ca binding

BODIPY appended new calix[4]arene diethyl ester (1) has been synthesized in the cone conformation. With respect to fluorescence intensity changes upon metal ion complexation, 1 shows a Ca²⁺ ion selectivity over other metal cations. Presence of two proximal hydroxyl groups and two facing ethyl esters in BODIPY-calix[4]arene were observed to play an important role in exhibiting its selective Ca²⁺ ion binding.     

The Preorganization Effect of the Calix[4]arene Platform on the Extraction Properties of Acetylhydrazide Groups with Transition Metal Ions

The binding properties of the cone conformer of O,O,O,O-tetrakis[hydrazinocarbonylmethyl]-4-tert-butylcalix[4]arene, the cone and the 1,3-alternate conformers of the corresponding thia analogue have been evaluated by means of liquid–liquid extraction for a large variety of metal ions. The extraction constants and the stoichiometries of the complexes formed have been determined. Comparison of the extraction properties of calix[4]arenes with their acyclic monomeric analogue clearly demonstrated, that the preorganization of acetylhydrazide groups on the calix[4]arene platform is the cause for a significant improvement of its binding properties. The presence of additional “soft” nitrogen binding sites in acetylhydrazide derivatives of calix[4]arenes compared to their amide derivatives leads to a shift from their classical selectivity for alkali and alkaline earth cations to transition metals. The cone conformer of tetrathiacalix[4]arene shows higher selectivity in a series of d-metal ions compared with its “classical” analogue. The 1,3-alternate conformer exhibits an excellent extraction selectivity for Cu²⁺ and Hg²⁺.     

Design and Synthesis of Calixarene‐Based Bis‐alkynyl‐Bridged Dinuclear AuI Isonitrile Complexes as Luminescent Ion Probes by the Modulation of Au⋅⋅⋅Au Interactions

Two calixarene‐based bis‐alkynyl‐bridged Au^I isonitrile complexes with two different crown ether pendants, [{calix[4]arene‐(OCH₂CONH‐C₆H₄C≡C)₂}{Au(CNR)}₂] (R=benzo[15]crown‐5 ( 1 ); R=benzo[18]crown‐6 ( 2 )), together with their related crown‐free analogue 3 (R=C₆H₃(OMe)₂‐3,4) and a mononuclear gold(I) complex 4 with benzo[15]crown‐5 pendant, have been designed and synthesized, and their photophysical properties have been studied. The X‐ray structure of the ligand, calix[4]arene‐(OCH₂CONH‐C₆H₄C?CH)₂ has been determined. The cation‐binding properties of these complexes with various metal ions have been studied using UV/Vis, emission, ¹H NMR, and ESI‐MS techniques, and DFT calculations. A new low‐energy emission band associated with Au???Au interaction could be switched on upon formation of the metal ion‐bound adduct in a sandwich fashion.     

INTERACTION OF METAL IONS WITH TWO NEW CALIX[4, 8]ARENE DERIVATIVES

Abstract

Two new calixarene derivatives: 5,11,17,23-tetra-t-butyl-25,26,27,28-tetrakis-(piperidinocarbo-nylmethyoxy)calix[4]arene (L⁴) and 5,11,17,23,29,35,41,47-octa-t-butyl-49,50,51,52,53,54,55, 56-octa-(piperidinocarbonylmethoxy)calix[8]arene (L⁸), which show good binding abilities to metal ions, were synthesized by the reaction of the corresponding calixarene derivatives with piperidine. The ligand L⁴ is capable of separating a tight ion-pair formed by Pb²⁺ and the picrate anion in THF. The interactions of the new ligands (Lⁿ n = 4, 8) with Na⁺, Pb²⁺ and Cd²⁺, in the presence or absence of picrate, were investigated by ¹H NMR and electrospray mass spectrometry. It is found that L⁴ reacts with these metal ions to form a unique complex which can be described as [M^m+L⁴]^m+ while L⁸ forms a variety of complexes depending on whether there are picrate anions in solution. [M^m+L⁸]^m+ is formed in the absence of the picrate, and two complexes, [PbL⁸]·CH₃CN·H₂O and [PbNaL⁸]³⁺, are formed in the presence of the picrate. The higher conformational flexibility and larger macro-ring size of L⁸ account for the fact that it forms a variety of complexes as compared with L⁴.     

Outer-sphere association of p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene with cobalt(III) tris(dipyridyl): the effect on the spectral and electrochemical properties of the latter

According to the 1H NMR and X-ray data, the outer-sphere association of [Co(dipy)3]3+ with cyclophanic anions p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene is accompanied by the inclusion of the dipyridyl moiety of the former into the cavities of the cyclophanic anions in aqueous and aqueous-DMSO solutions and in the solid state. The first-step dissociation of p-sulfonatothiacalix[4]arene does not change the inclusion mode, but the increase in DMSO content leads to a shallower inclusion of [Co(dipy)3]3+. The electrochemical property changes of [Co(dipy)3]3+ with both receptors undergoing ion pairing indicate the stabilization of the tris(dipyridyl) cobalt complexes in lower oxidation states. The effect of the cyclophanic anions on the cyclic voltammograms of [Co(dipy)3]3+ correlates with the efficiency of binding of the latter with tetrasulfonatomethylated calix[4]resorcinarene and p-sulfonatothiacalix[4]arene.     

A new fluorogenic mono-ionizable calix[4]arene dansylcarboxamide as a selective chemosensor of soft metal ions, Tl and Hg

A new fluorogenic calix[4]arene containing one pendent N-dansylcarboxamide group has been synthesized. The ligand demonstrates selective optical recognition of Tl⁺ and Hg²⁺ in solvent extraction from aqueous solutions with high content of Na⁺. Complexation of Tl⁺ and Hg²⁺ produces contrasting changes in the fluorescence spectrum of this sensor. Partial cone is the dominant calixarene conformation in the complex with Tl⁺.     

基于四丹磺酰胺杯[4]芳烃的汞离子荧光化学传感器

我们方便地合成了上沿修饰四丹磺酰胺基团的杯[4]芳烃衍生物1,发现该化合物在含50％水的乙腈中显示出对汞离子高选择性和灵敏性的识别作用,竞争实验表明多数金属离子对其检测干扰较小。机理研究结果表明荧光萃灭源于由丹磺酰胺基团到汞离子的光致电子转移过程。另外,通过研究1和1-Hg2+的荧光衰减实验,以及对比双丹磺酰胺杯[4]芳烃2和单丹磺酰胺杯[4]芳烃3对汞离子的识别作用,发现化合物1的四丹磺酰胺基团具有很好的预组织和协同作用。化合物1对汞离子的检测限为3.41×10-6 mol·L-1,这可以使1成为一个潜在的汞离子荧光化学传感器。     

Synthesis and binding properties of carboxylphenyl-modified calix[4]arenes and cytochrome c

Two novel carboxylphenyl-modified calix[4]arenes, tetrakis-carboxylphenylcalix[4]arene (TCPC) and 1,3-bis-carboxylphenylcalix[4]arene (BCPC), as well as a corresponding analogue for comparison, tetrakis-phenylcalix[4]arene (TPC), have been synthesized by palladium-catalyzed Suzuki cross-coupling of arylboronic acid and tetrabromocalix[4]arene as a key step. The binding properties of these calix[4]arene derivatives with bovine heart cytochrome c (cyt c) in dimethylformamide (DMF) was investigated by fluorescence spectroscopy. The binding affinity in the order of TCPC > BCPC ? TPC reflects a clear dependence on the number of carboxyl ligating groups attached onto a receptor and suggests the electrostatic force may be the predominant factor driving the complexing process. The stable 1:1 complexes of TCPC and BCPC with cyt c were evidenced with the binding constants of 3.15 × 10⁶ and 5.85 × 10⁵ L mol⁻¹, respectively. Due to a large overlap between the emission spectrum of TCPC and the absorption spectrum of cyt c, and a short interaction distance (estimated to be 5.6 nm) between them, the fluorescence quenching of TCPC upon complexation with cyt c is attributed to an efficient energy transfer.