冠醚的分子设计(XX)——含硫、硒杂环的苯并-15-冠-5的合成及其对阳离子的选择性

冠醚可以选择性配位金属离子 ,形成主 -客体或超分子配合物 .因此 ,冠醚的分子设计、合成 ,尤其是对金属离子的配位能力一直是化学研究领域的热点之一 [1] .为了得到高选择性的功能体系 ,控制主 -客体的配位作用 ,人们开展了广泛的冠醚合成及其配位作用的研究[2～ 4 ] .然而 ,含杂环的苯并冠醚研究较少[5～ 9] .我们曾报道了一系列冠醚对金属离子的配位能力和配位选择性 ,给出了有意义的结果[10 ,11] .本文报道两种新型苯并 -五元含硫、硒杂环 -苯并 -1 5 -冠 -5 (3 )和 (4 )的合成及其对苦味酸碱金属和重金属的萃取性能和选择性 .1　实验部…     

基于荧光硅球的克伦特罗快速定量免疫层析试纸条的研制

采用荧光硅球为标记物制备了快速定量检测克伦特罗(CLE)的荧光硅球免疫层析试纸条。通过正交实验得到最优荧光硅球抗体标记量、硅球垫抗体标记物用量以及检测线抗原浓度。在最优条件下,试纸条线性范围为0.28~3.3 mg/L。猪尿样品CLE加标回收率为81.7%~101%,表明此试纸条可实现猪尿中CLE残留的快速定量检测。     

Thermodynamics of the molecular and chiral recognition of cycloalkanols and camphor by modified beta-cyclodextrins possessing simple aromatic tethers

The complex stability constants (K(S)) and thermodynamic parameters (DeltaG degrees, DeltaH degrees, and TDeltaS degrees ) for 1:1 inclusion complexation of beta-cyclodextrin (beta-CD) derivatives, 6-O-phenyl-beta-CD (2) 6-O-(4-formyl-phenyl)-beta-CD (3), 6-O-(4-nitrophenyl)-beta-CD (4), 6-O-(4-bromophenyl)-beta-CD (5), 6-O-(4-chlorophenyl)]-beta-CD (6), and 6-O-(4-hydroxybenzoyl)-beta-CD (7) with representative guest molecules, cyclic alcohols (cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol), (+/-)-borneol, and (+/-)-camphor, have been determined by means of titration microcalorimetry in an aqueous phosphate buffer solution (pH = 7.20) at 298.15 K. The results obtained indicate that the introduction to beta-CD of an aromatic ring bearing different substituent groups significantly enhances the molecular binding ability and moderately alters the chiral discrimination ability for the guests examined here, displaying the highest enantioselectivity of up to 4.01 for the inclusion complexation of 6 with (+/-)-camphor. The enhanced molecular/chiral discrimination ability caused by derivatization is attributed solely to increased positive entropy changes due to the expanding hydrophobic interaction and desolvation effects. The binding modes of host-guest interactions derived from ROESY spectroscopy data show that the resulting complex of 4 and (+)-borneol possesses better induced-fit interaction as compared to (-)-borneol, which is responsible for the enhanced molecular/chiral recognition ability.     

Inclusion Complexation Thermodynamics of Acridine Red and Rhodamine B by Natural and Novel Oligo(ethylenediamine) Tethered Schiff Base β-Cyclodextrin

A series of Schiff base -cyclodextrin derivatives 2–5 with an oligo(ethylenediamine)tether have been newly synthesized and their inclusion complexation behavior has beenassessed and discussed thermodynamically, employing acridine red (AR) and rhodamine B (RhB) as representative guests. Fluorescence spectrophotometric titrations have been performed in methanol-water (1 : 2) phosphate buffer solution (pH = 7.20) at 25.0–45.0 °C in order to obtain the complex stability constants (K_S) and the thermodynamic parameters ( H° and T S°) for the stoichiometric 1 : 1 inclusion complexation of two guests with the native and modified -cyclodextrins ( 1 and 2–5). As compared with theparent -cyclodextrin 1, all of the chemical modifications to the primary side of -cyclodextrins examined led to substantial decreases for rhodamine B and marked increases for acridine red in complex stability, which are elucidated in terms of the induced-fit interaction and the complementary geometrical relationship between the host -cyclodextrins and guest molecules, as well as the length of the linking chain of -CD derivatives. The induced circular dichroism spectral analyses of these -cyclodextrin derivatives indicated that the aromatic moiety in modified -cyclodextrins is not embeded into the hydrophobic cavity ofcyclodextrin. The inclusion complexation of 2–5 with acridine red possess higher binding constants than that with rhodamine B, which are solely attributed to the increased enthalpic gain. Thermodynamically, the inclusion complexation with the modified -cyclodextrins 2–5 is absolutely enthalpy-driven for acridine red, while for complexation with rhodamine B is mainly entropy-driven.     

Synthesis of Double-Armed Benzo-15-crown-5 and Their Complexation Thermodynamics with Alkali Cations

A series of double-armed benzo-15-crown-5 lariats (3–8) have been synthesized by the reaction of 4′, 5′-bis(bromomethyl)-benzo-15-crown-5 (2) with 4-hydroxybenzaldehyde, phenol, 4-chlorophenol, 4-methoxyphenol, 2-hydroxybenzaldehyde, and 4-acetamidophenol in 43 ~ 82% yields, respectively. The complex stability constants (K _S) and thermodynamic parameters for the stoichiometric 1:1 and/or 1:2 complexes of benzo-15-crown-5 1 and double-armed crown ethers 3–8 with alkali cations (Na⁺, K⁺, Rb⁺) have been determined in methanol–water (V/V=8:2) at 25 °C by means of microcalorimetric titrations. As compared with the parent benzo-15-crown-5 1, double-armed crown ethers 3–8 show unremarkable changes in the complex stability constants upon complexation with Na⁺, but present significantly enhanced binding ability toward cations larger than the crown cavity by the secondly sandwich complexation. Thermodynamically, the sandwich complexations of crown ethers 3-8 with cations are mostly enthalpy-driven processes accompanied with a moderate entropy loss. The binding ability and selectivity of cations by the double-armed crown ethers are discussed from the viewpoints of the electron density, additional binding site, softness, spatial arrangement, and especially the cooperative binding of two crown ether molecules toward one metal ion.     

Synthesis of Some Selenacrown Ethers and the Thermodynamic Origin of Their Complexation with C60

Two new selenacrown ethers, i.e., N,N′-dimethyl-1,11-diaza-4,8,14,18,-tetraselenacycloicosane (1) and 7,11-diseleno-2,3,15,16,-dibenzo-1,4,14,17,20,23-hexaoxacyclopentacosane (2), have been synthesized and characterized by elemental analysis and UV, and ¹H-NMR spectroscopy. An X-ray crystallographic structure was obtained for 1. UV-spectrophotometric titrations have been performed in CCl₄ solution at 25–50 °C to obtain the complex stability constants (K_s) and the thermodynamic parameters (ΔH⁰ and TΔS⁰) for the stoichiometric 1:1 complexation of [60]-fullerene (C60) with the crown ethers 1–4. The obtained K_s values together with that reported for dicyclohexano-24-crown-8 (5) reveal that, the more the heteroatom numbers in crown ether ring are, and the larger the cavity sizes of crown ethers are, the higher theK_svalues for complexation with C60 are. Thermodynamically, the complexation of C60 with 1–5 is absolutely enthalpy-driven in CCl₄, while the complex stability is governed by the entropy term.     

Molecular Recognition Thermodynamics of Steroids by Novel Oligo(aminoethylamino)-β-cyclodextrins Bearing Anthryl: Enhanced Molecular Binding Ability by Co-inclusion Complexation

Three -cyclodextrin (-CD) derivatives bearing anthracene group (2–4) were synthesized by the condensation of 9-anthracenecarboxylic acid with the corresponding oligo(aminoethylamino)--CDs in 33–36% yields and their original conformations and binding behavior with steroid molecules were investigated by using spectroscopic techniques and isothermal calorimeter. The combination of induced circular dichroism (ICD) and 2D NMR spectra reveals that the anthryl group attached to -CD is itself included in cavity and the chain length of oligo(aminoethylamino) decides the orientation of the anthryl located in the cavity to some extent, directly affecting the binding ability with guest molecules. Calorimetric titration has been performed at buffer aqueous solution (pH 7.2) at 25 °C to give the binding constants (K_S) and thermodynamic parameters for 11 inclusion complexation of modified -CDs 2–4 and representative steroids, i.e., cholate, deoxycholate, glycocholate, and taurocholate. Possessing the sidearm with appropriate length, 3 gives the highest stability constant of 22485± 15 M^–1 for the complexation with deoxycholate molecule, which may be ascribed to the co-inclusion interactions between the host and guest. As compared with parent -CD 1 upon complexation with steroids, hosts 2–4 with different chain lengths enhanced the binding ability and significant molecular discrimination, which are discussed comparatively and globally from the viewpoint of thermodynamics. Furthermore, we establish the correlation between the conformation of the resulting complexes and the thermodynamic parameters obtained.     

Binding ability and self-assembly behavior of linear polymeric supramolecules formed by modified beta-cyclodextrin

[structure: see text] The binding ability and self-assembly behavior of molecular interpenetration by newly synthesized mono[6-O-(4-formyl-phenyl)-beta-cyclodextrin has been investigated, revealing the formation mechanism of modified cyclodextrin from solution aggregation to solid linear polymeric supramolecules.     

Molecular Recognition and Cooperative Binding Ability of Fluorescent Dyes by Bridged Bisβ-cyclodextrin)s Tethered with Aromatic Diamine

A novel bridged bis(β-cyclodextrin),m-phenylenediimino-bridged bis(6-imino-6-deoxy-β-cyclodextrin) (2), was synthesized by the reaction of m-phenylenediamine and 6-deoxy-6-formyl-β-cyclodextrin. The inclusion complexation behavior of the novel bridged bis(β-cyclodextrin) 2,as well as native β-cyclodextrin (1),p-phenylenediamino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (3) and 4,4'-bianilino-bridged bis(6-amino-6-deoxy-β-cyclodextrin) (4) with representative fluorescent dye molecules, i.e., acridine red (AR), neutral red (NR), Rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonate (ANS) and sodium 6-toluidino-2-naphthalenesulfonate (TNS), was investigated at 25 °C in aqueous phosphate buffer solution (pH 7.20) by means of fluorescence, and circular dichroism, as well as 2D NMR spectrometry. The spectrofluorometric titrations have been performed to calculate the complex stability constants (K_S) and Gibbs free energy changes (Δ G°) for the stoichiometric 1 : 1 inclusion complexation of 1–4 with fluorescent dye molecules. The results obtained demonstrated that bis(β-cyclodextrin)s 2–4 showed much higher affinities toward these guest dyesthan native β-cyclodextrin 1. Typically, dimer 2 displayed the highest binding ability upon inclusion complexation with ANS, affording 35 times higher K_S value than native β-cyclodextrin. The significantlyenhanced binding abilities of these bis(β-cyclodextrin)s are discussed from thebinding mode and viewpoints of size/shape-fit concept and multiple recognition mechanism.     

Controllable DNA condensation through cucurbit[6]uril in 2D pseudopolyrotaxanes

2D pseudopolyrotaxanes containing beta-cyclodextrins and cucurbit[6]urils can induce DNA condensation, and the number of cucurbit[6]urils threaded onto the side chains of beta-cyclodextrins plays important roles in this process.