Calix[4] open-chain crown ether-modified, vinyl-functionalized hybrid silica monolith for capillary electrochromatography

A novel calix[4] open-chain crown ether (p-tert-butylcalix[4]arene-1,3-bis(allyloxyethy) ether)-modified, organic-inorganic hybrid silica-based monolithic column possessing vinyl ligands for CEC is described. The monolithic silica matrix containing a vinyl functionality was synthesized by in situ cocondensation of tetramethoxysilane (TMOS) and vinyltrimethoxysilane (VTMS) via sol-gel process and chemically modified with calix[4] open-chain crown ether by free radical polymerization procedure using alpha, alpha'-azobisisobutyronitrile (AIBN) as an initiator. Morphology of the monolithic column was examined by SEM and the successful incorporation of calix[4] open-chain crown ether to the vinyl-hybrid monolith was characterized by infrared (IR) spectra. Compared with an unmodified vinyl-hybrid monolithic column, slightly stronger EOF at pH >7.5 was observed for this monolithic column due to the ionization of phenolic hydroxyls on the lower rim of calix[4]arene. VTMS/TMOS ratios in the reaction mixture were varied and 1:4 was found to be optimum to obtain homogeneous monolith with good permeability. The performance of the column was evaluated by nucleotides, beta-blockers, neurotransmitters, and PAHs as test solutes and compared with that of unmodified vinyl-hybrid monolithic column. Greatly improved column performance was obtained due to the host-guest interaction and intermolecular hydrogen bonding provided by the calix[4] open-chain crown ether moiety. The column efficiencies for neurotransmitters and nucleotides are up to 120 000 and 110 000 plates/m, respectively. Migration time and theoretical plate number reproducibilities were reasonable with RSDs less than 1.0 and 1.8% each for within column runs and not more than 7.2 and 8.6% each for column-to-column measurements, using four nucleotides as test solutes.     

基于杯［4］芳烃探头的固相微萃取-毛细管电泳法测定尿样中的兴奋剂普萘洛尔异构体

采用溶胶-凝胶法制备了一种双缩水甘油基杯［4］芳烃羟基硅油探头,运用自行设计的反萃取装置实现了顶空固相微萃取与毛细管电泳的离线联用,结合超声反萃取和场放大进样技术成功地测定了尿样中兴奋剂普萘洛尔异构体的含量。实验考察了固相微萃取条件和反萃取条件对测定结果的影响,比较了杯［4］芳烃探头与商品化探头对于尿样中普萘洛尔异构体的萃取性能,结果表明基于杯［4］芳烃探头的固相微萃取过程能够实现满意的净化效应与预富集效应。利用毛细管电泳-二极管阵列检测器对加标尿样中普萘洛尔异构体测定的线性范围为0.05~10 mg/L,检测限为8~10 μg/L,相对标准偏差小于6.5%(n=6),两种异构体的加标回收率为86%~107%(n=5)。该探头的可重复使用(＞150次)性能良好。     

含酰胺和席夫碱单元的杯[4]芳烃衍生物的合成与配合性能

杯[4]-1,3-二乙酸乙酯衍生物1与水合肼反应生成杯[4]芳烃酰肼衍生物2, 然后进一步与相应的芳醛反应, 高产率地合成了三个新型的含酰胺和席夫碱单元的杯[4]芳烃衍生物3a～3c和一例新型杯[4]冠醚4. 阳离子萃取实验表明新型杯芳烃衍生物比只含有酰胺基或席夫碱基的杯芳烃衍生物有更强的软金属离子配合性能, 杯[4]冠醚4还对Ag^＋有较好的选择性萃取能力.     

Lower-rim versus upper-rim functionalization in di-ionizable calix[4]arene-crown-5 isomers. Synthesis and divalent metal ion extraction

Two series of di-ionizable calix[4]arene-crown-5 isomers in the cone conformation are synthesized to probe the effect of the pendant acidic group location on their metal ion extraction properties. In one series, the ionizable groups are attached to the lower rim of the calix[4]arene scaffold, which orients them near the crown ether cavity. In the second series, the ionizable groups are connected to the upper rim positioning them away from the crown ether ring, but close to the hydrophobic pocket of the calix[4]arene unit. The metal ion extraction behaviors of the two series of ligands are compared in extractions of alkaline earth metal cations, Hg²⁺, and Pb²⁺.     

Stilbene-bridged 1,3-alternate calix[4]arene crown ether for selective alkali ion extraction

A series of stilbene-bridged calix[4]arenes was synthesized through an intramolecular reductive McMurry coupling of bisbenzaldehyde calix[4]arene in high yields. Tetra- and pentaethylene glycol chains were tethered to the phenolic groups of calix[4]arene to form stilbene-bridged calix[4]arene crown-5 and crown-6, respectively. The presence of stilbene bridge over the calix[4]arene rim effectively prevented the connection of the polyether chains in the cone conformation resulting in the exclusive formation of 1,3-alternate stilbene-bridged calix[4]arene crown product. Compared to the cone analogues, the 1,3-alternate calix[4]arene crown ethers showed a greater extraction ability and selectivity toward Cs⁺.     

Bis(crown ether) and Azobenzocrown Derivatives of Calix[4]arene. A Review of Structural Information from Crystallographic and Modelling Studies

The association within one molecule ofcalix[4]arene and crown ether moieties leads toligands with new complexing properties. In particular,calix[4]arene bis(crown-6) and some of itsderivatives have been shown to be highly selectiveextractants for caesium ions. This review presents thebackground of the study and the results of crystalstructure determinations and molecular modellingcalculations performed during the investigation of twomolecular families, the bis(crown ether) and theazobenzocrown derivatives of calix[4]arene.     

Preliminary study of the stability of calix[4]arene crown compounds under radiolysis

The extraction of (135)Cs from high activity waste arising from reprocessing of spent fuel can be achieved by using calix[4]arene crown compounds. The radiolytic degradation of calix[4]arene crowns as well as their solvent, o-nitrophenyloctyl ether (NPOE), was studied using electrospray ionization mass spectrometry (ESI-MS) (that formed Cs(+) or Na(+) adducts) in nitric acid, as well as by chemical ionization tandem mass spectrometry (MS/MS) experiments. The structures of major degradation products were identified with MS and specifically labelled nitric acid. Although NPOE and calix[4]arene crowns alone are relatively stable, under simulated conditions resembling the real industrial processes involving radiolysis in the presence of nitric acid, several products resulting from nitration and oxidation were observed.     

Synthesis and metal ion complexation studies of proton-ionizable calix

A series of novel N-chromogenic calix[4]arene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calix[4]arene azacrown ethers were prepared by reacting 25,27-dipropyloxy-26,28-bis(5-chloro-3-oxapentyloxy) calix[4]arenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calix[4]arene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calix[4]arene azacrown ether in moderate yield. These compounds show high potassium selectivity over other metal ions as shown by two-phase extraction, bulk liquid membrane, and 1H NMR studies on a ligand-metal complex. It is assumed that the OH of the chromogenic group attached on nitrogen can assist the complexation by encapsulation of the metal.     

Synthesis of an unsymmetrically doubly bridged calix[4]arene in the 1,3-alternate conformation

We report the synthesis of the first calix[4]arene constrained to a 1,3-alternate conformation by one crown ether and one di-aza-benzo crown ether bridgings. Preliminary binding properties are also given.     

三苄基杯[6]芳烃固相微萃取复合涂层的研制及其应用

采用溶胶-凝胶方法制备了三苄基杯[6]芳烃/羟基硅油(C[6]/OH-TSO)固相微萃取(SPME)探头, 通过对多环芳烃和酞酸酯(PAEs)的分析考察了新型C[6]/OH-TSO探头的性能. 结果表明: 杯[6]芳烃SPME探头对这些非极性和弱极性的芳香化合物有很好的萃取效果和选择性, 具有耐高温、使用寿命长等特点. 建立了SPME与气相色谱-氢火焰(GC-FID)联用测定化妆品中PAEs的方法. 该方法检测限低, 重现性好(RSD＜9%), 线性范围宽(2～3个数量级). 回收率在83.42%～98.85%之间.     

Development of a Sol-Gel Procedure for Preparation of a Diglycidyloxycalix[4]arene Solid-Phase Microextraction Fiber with Enhanced Extraction Efficiency

5,11,17,23-Tetra-tert-butyl-25,27-dihydroxy-26,28-diglycidyloxycalix[4]arene (diglycidyloxy-C[4]) has been synthesized and used for preparation of a sol-gel solid-phase microextraction fiber with enhanced extraction efficiency. The sol-gel procedure was developed using a sol solution containing diglycidyloxy-C[4] as organic component and both tetraethoxysilane and 3-aminopropyltriethoxysilane (KH-550) as precursors. No additional catalysts were used and no centrifugation was performed. Diglycidyloxy-C[4] was highly chemically reactive toward KH-550 even at room temperature, which increased the calixarene content of the coating, simplified the sol-gel procedure, reduced the sol-gel reaction time, enhanced the polarity of the coating, and improved extraction performance. The sol-gel mixture also had very good coating properties and was highly uniformly distributed on the surface of the fiber; because of these characteristics several fibers could be prepared from one sol-gel solution. Efficient extraction of trace analytes (µg L^?1 levels) from aqueous samples was accomplished using this kind of new fiber. Very low detection limits (ng L^?1 level) were achieved for most polar (aromatic amines and phenols) and nonpolar (polycyclic aromatic hydrocarbons) aromatic compounds by SPME followed by gas chromatography with flame ionization detection. The new coating had excellent solvent and thermal (350 °C) stability. Lifespan was also good—a fiber could be used more than 300 times in headspace SPME without substantial changes in the properties of the coating.     

Synthesis of novel chiral Schiff base and amino alcohol derivatives of calix[4]arene and chiral recognition properties

In the present study, the synthesis and liquid phase extraction properties towards some amino acid methylesters and amino alcohols of Schiff base and amino alcohol substituted calix[4]arene are reported. The Schiff base substituted calix[4]arene 5 has been synthesized via condensation reaction involving 5,17-diformyl-11,23-di-tert-butyl-25,27-di[3-(4-formylphenoxy)propoxy]-26,28 dihydroxycalix[4]arene 4 and (R)-(?)-2-phenylglycine methyl ester in CHCl₃:MeOH. To give the amino alcohol substituted calix[4]arene 6, the synthesized chiral compound 5 was reduced by LiAlH₄. The new chiral Schiff base and amino alcohol derivatives of calix[4]arene have been characterized by a combination of FT-IR, ¹H NMR, ¹³C NMR, FAB-MS and elemental analysis. Also, the extraction behaviors of 5 and 6 towards some selected amino acid methylesters and amino alcohols have been studied by liquid–liquid extraction.     

Potassium Sensing Calix[4]arene Crown Ethers

1,3-Alternate calix[4]arene crown-5 (1) and corresponding biscrown-5 (2) were synthesized and the complexation behavior with alkali metal ions examined. For both 1 and 2, potassium ion was selectively extracted from aqueous phase into organic phase over other alkali metal ions based on two phase extraction experiment. The complexation ratio between calix[4]arene biscrown-5 (2), in which two crown cavities connect to the calix[4]arene framework by 1,3-alternate fashion and potassium metal ion is found to 1:1 by proton NMR spectroscopy and extraction equilibria. Association constants (logK_a) for 1 and 2 were determined to give 2.51 and 3.49, respectively.     

新型席夫碱基杯[4]冠醚衍生物的合成

杯[4]-1,3-二酯衍生物与水合肼反应后再与二水杨醛二甘醚发生"1 1"分子间缩合,高产率合成了新型席夫碱基杯[4]冠醚衍生物,其结构经1HNMR,IR,MS和元素分析表征。     

Competitive Self and Induced Aggregation of Calix[4]arene Ethers and Their Interaction with Pinacyanol Chloride and Methylene Blue in Nonaqueous Media

Long chain calix[4]arene ethers have been examined for aggregation in nonaqueous solvents by using UV-vis molecular absorbance spectroscopy. It has been observed that tetraalkylated (alkyl = hexadecyl and octadecyl, respectively) calix[4]arene ethers tend to aggregate in chloroform and tetrahydrofuran, possibly via π–π stacking interactions of the phenyl moieties, and the aggregation process appears to be facilitated by the alkyl chains. The analogous dialkylated compounds do not show any self-aggregation, plausibly due to strong hydrogen bonding between the –OH and the –O– of calix aryl ether which seems to disrupt the aggregation process. Addition of the anionic surfactant sodium dodecylsulfate (SDS) appears to hinder the aggregation process in nonpolar chloroform but the same surfactant facilitates aggregation in the polar tetrahydrofuran. The cationic surfactant (cetyltrimethyl ammonium bromide) and the nonionic surfactant (Brij-35) have no effect on this aggregation process. Unexpectedly, SDS induces aggregation of dialkylated calix[4]arene ethers in chloroform. It has been observed that the aggregated form of the tetraalkylated calix[4]arene ethers tend to increase the dimerization efficiency of cationic dyes (pinacyanol chloride and methylene blue) in chloroform.     

Cesium-ion selective electrodes based on calix[4]arene dibenzocrown ethers

Four calix[4]arene dibenzocrown ether compounds have been prepared and evaluated as Cs(+)-selective ligands in solvent polymeric membrane electrodes. The ionophores include 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-6 1, 25,27-bis(1-alkyloxy)calix[4]arene dibenzocrown-7s 2 and 3, and 25,27-bis(1-propyloxy)calix[4]arene dibenzocrown-8 4. For an ion-selective electrode (ISE) based on 1, the linear response concentration range is 1x10(-1) to 1x10(-6) M of Cs(+). Potentiometric selectivities of ISEs based on 1-4 for Cs(+) over other alkali metal cations, alkaline earth metal cations, and NH(4)(+) have been assessed. For 1-ISE, a remarkably high Cs(+)/Na(+) selectivity was observed, the selectivity coefficient (K(Cs,Na)(Pot)) being ca. 10(-5). As the size of crown ether ring is enlarged from crown-6 (1) to crown-7 (2 and 3) to crown-8 (4), the Cs(+) selectivity over other alkali metal cations, such as Na(+) and K(+), is reduced successively. Effects of membrane composition and pH in the aqueous solution upon the electrode properties are also discussed.     

Evidence for Dual Pathway in Through‐Space Singlet Energy Transfers in Flexible Cofacial Bisporphyrin Dyads

Flexible “pacman” scaffolds built upon a calix[4]arene platform bearing a [18]crown‐6 ether and either two OH functions or two OPr groups at the lower rim have been used to generate donor–acceptor (D–A) dyads incorporating a zinc–porphyrin donor and a free‐base porphyrin acceptor. Through‐space singlet energy transfer (SET) in the D–A dyads was studied by time‐resolved fluorescence spectroscopy. Although the effects of conformational changes are well documented when the chromophores switch from a non‐cofacial to a cofacial arrangement, little is known about flexible pacman scaffolds in which the changes are limited to the distance between the chromophores. The known SET rates for reported, geometrically well‐defined, rigid pacman D–A dyads were used as calibration to estimate the D–A distances in the flexible pacman dyads. Due to the flexibility of the calix[4]arene spacer, the D–A dyads adopt a “closed” or “open” geometry that is tuned by intramolecular hydrogen bonds (O? H???[18]crown‐6 ether) and by solvent interactions. Changes in the SET rates between the open and closed geometries were surprisingly less dramatic than expected, and are explained by a dual SET pathway that is specific to the calix[4]arene platform. Time‐resolved fluorescence studies support the hypothesis that, for the “open” conformer, the preferred through space SET pathway (i.e., at the shortest distance) is located within the calix[4]arene cavity through the cofacial phenyl groups. For the “closed” conformer, the preferred through space SET route is located between the zinc and free‐base porphyrins.     

N-硫脲基套索杯[4]冠醚与四硫脲基杯[4]芳烃的合成

控制反应物的物质的量比, 杯式对叔丁基杯[4]-1,3-二乙酸乙酯衍生物1与5或50倍二乙烯三胺反应, 分别得到杯[4]氮杂冠醚2和开链的氮杂杯[4]芳烃衍生物3. 化合物2和3进一步与异硫氰酸苯酯反应得到首例侧链含硫脲基的套索杯[4]氮杂冠醚4和含4个硫脲基的杯[4]芳烃衍生物5, 产率为92%和87%. 新化合物的结构与构象经元素分析、红外、质谱、核磁共振谱等表征证实.     

Solid-phase microextraction coupled with capillary electrophoresis for the determination of propranolol enantiomers in urine using a sol-gel derived calix[4]arene fiber

A new type of diglycidyloxy-calix[4]arene coated fiber made by sol-gel method was initially prepared for capillary electrophoresis (CE) sample pretreatment. By using headspace solid-phase microextraction (SPME) combined with a novel back-extraction facility coupled off-line to capillary zone electrophoresis (CZE), the simultaneous determination of propranolol enantiomers in human urine was achieved. The clean up effect and preconcentration effect were realized for the first time without derivatization during the SPME process in terms of these strong polarity and thermal stable compounds. Ultrasonic back-extraction and field amplified sample injection (FASI) technologies were employed. Extraction and back-extraction parameters were optimized. Preconcentration of the sample by calix[4]arene fiber based SPME and FASI increased the sensitivity, yielding a limit of detection (LOD) of 0.01microg/ml by CZE-diode array detection (DAD). Method repeatability (RSD<6.5%) and fiber reusability (>150 extraction procedures) were observed over a linear range (0.05-10microg/ml) in urine samples. Based on the superior thermal stability, high alkali- and solvent-resistant ability, marvelous repeatability and long lifetime of the novel fiber, this SPME-FASI-CZE procedure could meet the demand of minimum required performance limit (MRPL) set by the World Anti-doping Agency (WADA) for the detection of propranolol in urine samples.     

对叔丁基杯[10]冠醚的合成

首次合成一系列杯[10]冠醚。通过将对叔丁基杯[10]芳烃和乙二醇双对甲苯磺酸酯或多甘醇双对甲苯磺酸酯在K2CO3/甲苯或Cs2CO3/丙酮体系中反应,得到一系列杯[10]冠醚:1,2-杯[10]冠-4、1,3-杯[10]冠-2、1,2-,1,3-杯[10]冠-3、1,4-杯[10]冠-4、和1,6-杯[10]冠-4。