新型三脚架苯甲醛苯腙醋酸根选择性比色化学传感器

本文合成了一个新的基于三脚架苯甲醛苯腙的能够选择地检测醋酸根离子的比色化学传感器1。用紫外可见吸收光谱证实了受体1在二甲基亚砜溶液中对醋酸根离子高选择的键合能力超越了其它阴离子。和其他所研究的阴离子相比,其在二甲基亚砜中紫外可见吸收光谱对具有高选择性醋酸根离子的存在显示了应答,当存在（2´10^-5mol·dm^-3）醋酸根离子时其溶液的颜色也由黄色变化到蓝色。当用其他不同的客体阴离子（F^-, Cl^-, Br^-, I^-, H₂PO₄ ^–和 OH^-）处理受体1时,仅出现了很小的紫外可见吸收光谱变化。受体1对醋酸根的结合常数 K_ass为1.69´ 10⁴。     

Novel Hydrazone‐Based Tripodal Sensors: Single Selective Colorimetric Chemosensor for Acetate in Aqueous Solution

A series of novel tripodal colorimetric anion sensors based on hydrazone CHN NH groups have been synthesized and their recognition behavior with anionic guests has been studied. In DMSO solutions, sensors 1 and 2 show colorimetric responses for F⁻, H₂PO⁻₄ and AcO⁻, while in DMSO/H₂O (9:1, V/V) solutions, sensor 1 shows single selectivity for AcO⁻. ¹H NMR titration confirms that the tripodal sensors could bind anions through the collaboration of three hydrazone groups and anions residing in the central cavity of the sensors.     

Modulation of Excited‐State Proton Transfer of 2‐(2′‐Hydroxyphenyl)benzimidazole in a Macrocyclic Cucurbit[7]uril Host Cavity: Dual Emission Behavior and pKa Shift

The effect of the macrocyclic host, cucurbit[7]uril (CB7), on the photophysical properties of the 2‐(2′‐hydroxyphenyl)benzimidazole (HPBI) dye have been investigated in aqueous solution by using ground‐state absorption and steady‐state and time‐resolved fluorescence measurements. All three prototropic forms of the dye (cationic, neutral, and anionic) form inclusion complexes with CB7, with the largest binding constant found for the cationic form (K≈2.4×10⁶ M ^?1). At pH≈4, the appearance of a blue emission band upon excitation of the HPBI cation in the presence of CB7 indicates that encapsulation into the CB7 cavity retards the deprotonation process of the excited cation, and hence reduces its subsequent conversion to the keto form. Excitation of the neutral form (pH≈8.5), however, leads to an increase in the keto form fluorescence, indicating an enhanced excited‐state intramolecular proton‐transfer process for the encapsulated dye. In both the ground and excited states, the two pK_a values of the HPBI dye show upward shifts in the presence of CB7. The prototropic equilibrium of the CB7‐complexed dye is represented by a six‐state model, and the pH‐dependent changes in the binding constants have been analyzed accordingly. It has been observed that the calculated pK_a values using this six‐state model match well with the values obtained experimentally. The changes in the pK_a values in the presence of CB7 have been corroborated with the modulation of the proton‐transfer process of the dye within the host cavity.     

Tunability of anion binding strength based on acyl-thiourea receptors containing isatin group

Some acyl-thiourea derivatives containing isatin group were synthesized and their interactions with anions were investigated using UV–vis spectroscopy and ¹H NMR titrations in DMSO and DMSO-d₆, respectively. These compounds have a same molecular framework, functionalising with different groups lead to different anion binding strength of these receptors. Receptor 1 showed a higher binding affinity for AcO⁻ than for F⁻, due to the cooperative multiple hydrogen bond interactions of AcO⁻ with the acyl-thiourea group and N–H group in the indole unit of receptor 1. Displacing the N–H proton in the indole unit with –CH₃ group, receptor 2 showed no obviously discriminative responses for F⁻, AcO⁻ and H₂PO₄⁻ due to lack of such additional binding. In the case of receptor 3, which was functionalised with strong electron-withdrawing group, it showed selectively chromogenic response for F⁻ based on double deprotonation of the receptor in DMSO, whereas AcO⁻ and H₂PO₄⁻ induced single deprotonation only.     

基于分子内电荷转移的阴离子比率荧光分子探针

设计合成了一种基于4-甲基-1-羟基二苯甲酮对硝基苯腙的比色和比率荧光阴离子受体1。此类受体以羟基和腙单元为识别位点,以硝基苯基为信号报告基团。向受体1的DMSO溶液中加入AcO-、H2PO4-、F-后,溶液颜色由黄色变为紫红色,而加入所研究的其它阴离子则无变化,从而实现对AcO-、H2PO4-、F-这三种离子的裸眼识别。利用紫外-可见吸收光谱、荧光光谱考察了其与AcO-,H2PO4-,F-,Cl-,Br-,I-等阴离子的识别作用。1H NMR滴定为受体分子与阴离子之间氢键作用本质提供了有力证据。     

Fatty Acid Carboxylate‐ and Anionic Surfactant‐Controlled Delivery Systems That Use Mesoporous Silica Supports

We report the preparation of a MCM‐41 mesoporous material that contains the dye [Ru(bipy)₃]Cl₂ (bipy=bipyridine) inside the mesopores and functionalised with suitable binding groups at the entrance of the pores. Solids S1 – S3 were obtained by the reaction of the mesoporous material with N‐methyl‐N′‐propyltrimethoxysilylimidazolium chloride, N‐phenyl‐N′‐[3‐(trimethoxysilyl)propyl]thiourea, or N‐phenyl‐N′‐[3‐(trimethoxysilyl)propyl]urea, respectively. A study of the dye delivery of these systems in buffered water (pH 7.0, 2‐[4‐(2‐hydroxyethyl)piperazin‐1‐yl]ethanesulfonic acid (HEPES), 10^?3 mol dm^?3) in the presence of a family of carboxylate ions was carried out. In the interaction of the anions with the surface of the solids, the response depends on the characteristics of the binding groups (i.e., imidazolium, urea and thiourea) at the pore outlets and their specific interaction with the corresponding anion. The interaction of long‐chain carboxylate ions with the binding sites at the surface of the solids resulted in a remarkable inhibition of the delivery of the dye. This inhibition was observed clearly for the dodecanoate anion, whereas the octanoate, decanoate, cholate, deoxycholate, glycodeoxycholate and taurocholate anions induced a certain pore blockage that varied according to the solid studied. The interaction of smaller anions, such as acetate, butanoate, hexanoate and octanoate, with the solids had no effect on the dye release process. The possible use of the gating system for the chromo‐fluorogenic detection of anionic surfactants through selective dye delivery inhibition was also explored. Molecular dynamic simulations that use force‐field methods have been made to theoretically study the capping carboxylate mechanism. The calculations are in agreement with the experimental results, thus allowing a representation of the dye delivery inhibition in the presence of long‐chain carboxylate ions.     

An exclusive fluoride receptor: fluoride-induced proton transfer to a quinoline-based thiourea

A new quinoline-based tripodal thiourea has been synthesized, which exclusively binds fluoride anion in DMSO, showing no affinity for other anions including chloride, bromide, iodide, perchlorate, nitrate, and hydrogen sulfate. As investigated by ¹H NMR, the receptor forms both 1:1 and 1:2 complexes yielding binding constants of 2.32(3) (in log β₁) and 4.39(4) (in log β₂), respectively. The quinoline groups are protonated by fluoride-induced proton transfer from the solution to the host molecule. The 1:2 binding is due to the interactions of one fluoride with NH binding sites of urea sites and another fluoride with secondary ⁺NH binding sites within the tripodal pocket. The formation of both 1:1 and 1:2 complexes has been confirmed by theoretical calculations based on density functional theory (DFT).     

Attachment of anthraquinone derivatives to glassy carbon and the electrocatalytic behavior of the modified electrodes toward oxygen reduction

The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with anthraquinones was studied using cyclic voltammetry (CV) and the rotating disk electrode (RDE) technique. Two methods were used in surface modification. The first method comprised immersion of the polished or anodically pretreated GC electrode in a solution containing 9,10-anthraquinone-2-carboxylic acid (AQ-2-COOH) or its anion (AQ-2-COO⁻) in dimethylsulfoxide (DMSO) or 9,10-anthraquinone-2-ethanoic acid (AQ-2-CH₂COOH) or its anion (AQ-2-CH₂COO⁻) in N,N-dimethylformamide (DMF). Alternatively, the surface of the GC disk was modified by anodic oxidation of AQ-2-COOH or AQ-2-COO⁻ in DMSO or AQ-2-CH₂COOH in DMSO or DMF or AQ-2-CH₂COO⁻ in DMF. The modified electrodes showed electrocatalytic activity toward oxygen reduction in 0.1 M acetate buffer pH (4.8), 0.1 M phosphate buffer (pH 8) and 0.1 M NaOH. Atomic force microscopy (AFM) examination of the modified electrodes was carried out and the differences in surface morphology of various modifications were in evidence.     

A sandwich anion receptor by a BODIPY dye bearing two calix[4]pyrrole units

A novel dicalix[4]pyrrolyl-substituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye I with an absorption peak at approximately 670 nm and an emission peak at about 690 nm was prepared. As an anion receptor, I displayed a red shift in absorption spectra and fluorescence quenching in varying degrees in the presence of F⁻, AcO⁻, H₂PO₄⁻, or Cl⁻. Compared with the parent calix[4]pyrrole, a representative anion receptor, I exhibited a stronger affinity to these anions due to the formation of a sandwich complex through multiple hydrogen-bonding interactions.     

基于杯[4]芳烃的对N-乙酰基-天冬氨酸盐对映选择性识别的荧光传感器

合成了携带有丹磺酰基荧光团和（1R,2R）- 或（1S,2S）-1,2-二苯基乙二胺键合单元的双臂杯[4]芳烃手性阴离子受体（1和2）。通过荧光光谱检测了受体对手性氨基酸阴离子的键和能力。非线型曲线拟合的结果表明受体（1或2）与N-乙酰基-L或D－天冬氨酸盐通过多重氢键的相互作用形成了1：1的络合物。并且展现了对N-乙酰基天冬氨酸盐对映体良好的对映选择性的荧光识别（受体1： K_ass(D)/ K_ass(L)=6.74;受体2： K_ass(L)/ K_{ass (D)}=6.48）。明显不同的荧光响应说明受体1和2能被用作为对N-乙酰基天冬氨酸盐的荧光化学传感器。     

A Comparative Study of Complexation of β-Cyclodextrin,Calix[4]arenesulfonate and Cucurbit[7]uril with Dye Guests: Fluorescence Behavior and Binding Ability

The complexation behaviors of acridine red (AR), neutral red (NR) and rhodamine B (RhB) dye guest molecules by three kinds of supramolecular hosts, including β-cyclodextrin (β-CD), calix[4]arene tetrasulfonate (C4AS) and cucurbit[7]uril (CB[7]), have been investigated by means of fluorescence spectra in aqueous citrate buffer solution (pH 6.0). The results obtained show that the three hosts, possessing different types of cavity, lead to various complexation-induced fluorescence of dye guests, and present different binding ability and molecular selectivity. The complexation stability constants decrease in the order of NR > AR > RhB for C4AS and CB[7] hosts, while in the order of RhB > AR > NR for β-CD host. Particularly, CB[7] displays the strongest binding ability with NR (K _S = 33300 M^? 1), and provides the molecular selectivity of 4.8 for NR/AR pairs. Although the binding ability of C4AS for present dye guests is weaker than CB[7], but the molecular selectivity of the two hosts are nearly equivalent. β-CD shows stronger binding ability with RhB (K _S = 5880 M^? 1) as comparison with CB[7] and C4AS. Furthermore, the solvent effects and salt effects during the course of complexation have also been investigated.     

Molecular Ionics of Anion Receptor Molecules: A Microcalorimetric Study

The coordination of divalent and monovalent inorganic anions to synthetic polyammonium receptors is investigated in aqueous solution around neutral pH by titration calorimetry and NMR spectroscopy. High-affinity 1:1 complexes are formed by a pyrrole type cryptand (1) with sulfate and phosphate, characterized by association constants of almost 107 M^-1. Affinities close to 105 M^-1 are found for polyazacryptands (3 and 4) exhibiting F^-/Cl^- selectivity. The binding affinities and the anion selectivities are mainly caused by the charges of ligands and anions, which is discussed on the basis of simple calculations of the electrostatic contribution to the anion/receptor interactions. The binding of all investigated anions is exothermic at 298.2 K. The contribution of the large negative ΔH values to the free energy of anion binding of the pyrrole type ligand is partially compensated by marked negative ΔS values. These unfavorable entropic contributions are attributed to the additional inclusion of water molecules in the anion/receptor complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Protonation and Anion Binding Properties of Aromatic Bis-Urea Derivatives—Comprehending the Proton Transfer

A series of aromatic bis-urea derivatives was prepared and their proton dissociation, as well as anion binding properties in DMSO were investigated. To this end, UV/Vis and ¹H NMR spectroscopies and computational methods were employed. The synthesized molecules differed in the relative position of the urea moieties (ortho- and meta-derivatives) and in the functional groups (−H, −CH₃, −OCH₃, −NO₂) in the para-position of the pendant phenyl groups. Remarkably high acidities of the compounds (logK₁^H≈14), were ascribed primarily to the stabilizing effect of the aromatic subunits. Quantum chemical calculations corroborated the conclusions drawn from experimental data and provided information from the structural point of view. Knowledge regarding protonation properties proved to be essential for reliable quantitative determination of anion binding affinities. Studied receptors were selective for acetate and dihydrogen phosphate among several anions. Formation of their complexes of 1:1 and 1:2 (ligand/anion) stoichiometries was quantitatively characterized. Proton transfer was taken into account in the course of data analysis, which was especially important in the case of AcO⁻. ortho-Receptors were proven to be more efficient acetate binders, achieving coordination with all four NH groups. The meta-analogues preferred dihydrogen phosphate, which acted as both hydrogen bond donor and acceptor. Cooperative binding was detected in the case of 1:2 H₂PO₄⁻ complexes, which was assigned to formation of interanionic hydrogen bonds.     

Synthetic Receptors with Micromolar Affinity for Chloride in Water

A water-soluble coordination cage was obtained by reaction of Pd(NO₃)₂ with a 1,3-di(pyridin-3-yl)benzene ligand featuring a short PEG chain. The cavity of the metal-organic cage contains one nitrate anion, which is readily replaced by chloride. The apparent association constant for chloride binding in buffered aqueous solution is K_a=1.8(±0.1)×10⁵ M⁻¹. This value is significantly higher than what has been reported for other macrocyclic chloride receptors. The heavier halides Br⁻ and I⁻ compete with binding or self-assembly, but the receptor displays very good selectivity over common anions such as phosphate, acetate, carbonate, and sulfate. A further increase of the chloride binding affinity by a factor of 3 was achieved using a fluorinated dipyridyl ligand.     

Study on Synthesis and Binding Ability of a New Anion Receptor Containing NH Binding Sites

A new colorimetric recognition receptor 1 based on the dual capability containing NH binding sites of selectively sensing anionic guest species has been synthesized. Compared with other halide anions, its UV/Vis absorption spectrum in dimethyl sulfoxide showed the response toward the presence of fluoride anion with high selectivity, and also displayed dramatic color changes from colorless to yellow in the presence of TBAF （5 × 10^-5 mol/L）. The similar UV/Vis absorption spectrum change also occurred when 1 was treated with AcO^- while a little change with H2PO^-4 and OH^-. Receptor 1 has almost not affinity abilities to Cl^-, Br^- and I^-. The binding ability of receptor 1 to fluoride with high selectivity over other halides contributes to the anion size and the ability of forming hydrogen bonding. While the different ability of binding with geometrically triangular （AcO^-）, tetrahedral （H2PO^-4 ） and linear （OH^-） anions maybe result from their geometry configuration.     

Anion exchange in trimethyl‐ and triphenyltin complexes with chromogenic ligands: solution equilibria and colorimetric anion sensing

A series of organotin(IV) compounds R₃Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F⁻, Cl⁻, Br⁻, AcO⁻, H₂PO₄⁻). Equilibrium constants for a complete set of reactions between R₃Sn(A) with A = 2‐amino‐4‐nitrophenolate (ANP) or 4‐nitrophenolate and anions (X⁻) involving formation of complexes R₃Sn(A)(X)⁻ and substitution products R₃Sn(X) and R₃Sn(X)₂⁻ were determined by UV‐vis and ¹H NMR titrations in MeCN and DMSO. The binding selectivity was AcO⁻ > F⁻ > H₂PO₄⁻ > Cl⁻ ≫ Br⁻ in both solvents and both for R = Me and Ph with higher affinity for R = Ph. Compounds with A = ANP were found to have the optimum properties as anion sensors allowing optical detection of F⁻, AcO⁻ and H₂PO₄⁻ anions in the 5–100 µM range by appearance of an intense absorption band of free ANP resulting from its substitution with the analyte. Selectivity and affinity of anion interactions with R₃Sn(ANP) are similar to those for thiourea receptors, but the organotin receptor produces a much larger naked eye detected optical signal, operates equally well in nonpolar and polar solvents and tolerates the presence of up to 20% vol. of water in DMSO. Copyright © 2011 John Wiley & Sons, Ltd.     

Colorimetric ��naked-eye�� sensor for anions based on conformational flexible tripodal receptor

A new tripodal receptor for anion sensing based on amide-pyridinium as recognition site and nitro-benzene as signaling unit was designed and successfully synthesized. This receptor showed high selectivity and strong binding affinity toward AcO^? over the investigated anions, especially over H₂PO₄ ^?. Addition of AcO^? induced clear color change of solution from colorless to yellow, realizing the ??naked-eye?? detection. UV?CVis and ¹H NMR experiments indicated the selectivity might origin from the synergistic effects arising from hydrogen bonding, electrostatic interactions and conformational change.     

Al selective an efficient colorimetric receptor derived from 5-aminouracil

An interference-free naked-eye recognition of Al³⁺ at its micromolar level has been done in 5% aqueous DMSO solution employing a Schiff base 5-[(2-hydroxy-5-nitro-benzylidene)-amino]-1H-pyrimidine-2,4-dione (receptor 1) which is an intramolecular charge transfer (ICT) probe. The pyrimidine and nitrophenyl groups serve as electron rich (donor) and deficient (acceptor) pockets in receptor 1 exhibiting a broad ICT band at 434 nm (olive green). The concomitant additions of Al³⁺ as its chloride salt to the 5 × 10⁻⁵ M aqueous DMSO solution of the receptor 1 lead hypsochromic shifting of its ICT band to 395 nm (colorless). The same ICT band undergoes a marginal bathochromic shifting (6 nm) along with a hyperchromic shift on separate additions of a basic anion like F⁻, CH₃COO⁻ and H₂PO₄⁻ to the receptor 1 and faced almost similar fate on concomitant additions of Al³⁺ as mentioned above.     

Anion Recognition Using Novel and Colorimetric Tweezer Receptors:1,3-Phenylenedi(carbonylhydrazone) in Aqueous-organic Binary Solvents

本文设计合成了2种新型的间苯二甲酰腙类钳形受体。在DMSO和DMSO-H2O混合溶液中,通过紫外可见光谱分别考察了受体分子3a对F-, Cl-, Br-, I-, AcO-, HSO4-, H2PO4-和ClO4-的相互作用。结果表明,在DMSO溶液中,受体3a对F-,CH3COO-和H2PO4-有显著识别效果,溶液颜色由无色变为黄色,实现裸眼检测。在15%H2O-85%DMSO含水体系中,3a可高选择性识别CH3COO-。1H NMR滴定表明过量F-的加入使受体分子3a发生脱质子作用,探讨了主客体之间的作用机理。并直接用于水相中无机醋酸盐的直接显色检测。     

A novel, simple, colorimetric receptor based on 2′,4′-dinitrophenylhydrazone for acetate ion in organic medium

A novel 1,3-di(2′,4′-dinitrophenylhydrazone)-5-nitrobenzene receptor has been synthesized by simple steps with good yields. The anion recognition properties were studied by ultraviolet-visible (UV-Vis) spectroscopy. The results showed that the receptor had a higher affinity to F^?, CH₃COO^? and H₂PO ₄ ^? , but no evident binding with Cl^?, Br^?, and I^?. Upon addition of the three former anions to the receptors in dimethyl sulphoxide (DMSO) at 298.2 ± 0.1 K, the solution exhibited an obvious color change from yellow to mauve that could be observed by the naked eye, thus the receptor could act as a fluoride ion sensor even in the presence of other halide ions. The UV-Vis data indicates that a 1:1 stoichiometry complex formed through hydrogen-bonding interactions between receptor and anions. The hydrogen bond between phenylhydrazone –NH and acetate or fluoride anion was determined on the basis of ¹H nuclear magnetic resonance (NMR) experiments.