酰氨基硫脲类新型分子钳受体的合成及其对氟离子的识别性能研究

本文设计并高产率合成了三种新型阴离子识别受体化合物,它们对F-的识别选择性较卤素其他阴离子的高。其对F-的识别性能通过紫外—可见光谱和核磁共振氢谱进行了检测,光谱数据表明,在DMSO溶液中受体与F-通过氢键相互作用形成1:1配合物。与以前我们报道的受体化合物相比,由于此类分子钳受体化合物具有更多的阴离子识别位点,因此具有更好地阴离子识别性能。     

含硫脲和酰胺单元的新型杯［4］芳烃中性氟离子受体

Two-armed neutral anion receptors (4,5), calix[4]arenes beating thiourea and amide binding sites, were prepared and examined their anion-binding ability by the UV-vis spectra. The results of non-linear curve fitting and Job plot indicate that 4 or 5 forms 1：1 stoichiometry complex with fluoride by hydrogen bonding interactions. Receptors 4 and 5 have an excellent selectivity for fluoride but have no binding ability with acetate, dihydrogen phosphate and the halogen anions (Cl^-,Br^-,I^-).     

硫脲类阴离子受体的研究进展

阴离子识别是超分子化学研究的重要内容之一,其关键环节是构筑可识别阴离子的结合受体,后者以非共价键力如静电作用、疏水作用、氢键等与阴离子结合.本文详细评述了近5年来硫脲类阴离子识别受体的设计、结构及其阴离子识别作用的研究进展.     

Macrocyclic anion receptors based on directed hydrogen bonding interactions

Natural anion receptors use charge-neutral dipoles to bind small anions with high affinities and selectivities. A convergent and rigid display of hydrogen bond donors such as amide, thiourea and urea functional groups in macrocyclic scaffolds would be one of the most efficient ways to create synthetic anion receptors that mimic natural ones. In this article, we present examples of natural anion receptors and discuss the synthesis of neutral macrocyclic receptors and their anion binding properties.     

Investigating the imidazolium–anion interaction through the anion-templated construction of interpenetrated and interlocked assemblies

The interaction between imidazolium cations and coordinating anions is investigated through the anion‐templated assembly of interpenetrated and interlocked structures. The orientation of the imidazolium motif with respect to anion binding, and hence the hydrogen bond donor arrangement, was varied in acyclic receptors, interpenetrated assemblies, and the first mono‐imidazolium interlocked systems. Their anion recognition properties and co‐conformations were studied by solution‐phase ¹H NMR investigations, solid‐state structures, molecular dynamics simulations, and density functional theory calculations. Our findings suggest that the imidazolium‐anion binding interaction is dominated by electrostatics with hydrogen‐bonding contributions having weak orientational dependence.     

A Halogen‐Bonding Bis‐triazolium Rotaxane for Halide‐Selective Anion Recognition

A systematic study on the anion‐binding properties of acyclic halogen‐ and hydrogen‐bonding bis‐triazolium carbazole receptors is described. The halide‐binding potency of halogen‐bonding bis‐iodotriazolium carbazole receptors was found to be far superior to their hydrogen‐bonding bis‐triazolium‐based analogues. This led to the synthesis of a mixed halogen‐ and hydrogen‐bonding rotaxane host containing a bis‐iodotriazolium carbazole axle component. The rotaxane’s anion recognition properties, determined by ¹H NMR titration experiments in a competitive aqueous solvent mixture, demonstrated the preorganised halogen‐bonding interlocked host cavity to be halide‐selective, with a strong binding affinity for bromide.     

Simple urea/thiourea sensors for the biologically important ions

Two anion receptors 1 and 2 with a nitrophenyl group as a signaling group and urea/thiourea as a binding group were synthesized and their anion binding abilities were examined. The receptor 1 formed the hydrogen-bonded complex with various anions except fluoride. However, the receptor 2 immediately formed deprotonated receptor with various anions. Therefore, they operated based on a hydrogen bonding and an acid?Cbase equilibrium. In addition, the receptor 1 proved to be an efficient and selective naked-eye detector for the fluoride ion.     

Anion recognition and sensing in organic and aqueous media using luminescent and colorimetric sensors

This review article focuses primarily on the work carried in our laboratories over the last few years using luminescent and colorimetric sensors, where the anion recognition occurs through hydrogen bonding in organic or aqueous solvents. This review begins with the story of the discovery of fluorescent photoinduced electron transfer (PET) sensors for anions using charged neutral urea or thiourea receptors where both fluorescent and NMR spectroscopic methods monitored anion recognition. This work led to the development of dual luminescent and colorimetric anion sensors based on the use of the ICT based naphthalimide chromophore, where ions such as fluoride gave rise to changes in both the fluorescence and the absorption spectra of the sensors, but at different concentrations. Here, the former changes were due to hydrogen bonding interactions, whereas the latter was due to the deprotonation of acidic protons, giving rise to the formation of the bifluoride anion (HF₂⁻). Modification of the 4-amino-l,8-naphthalimide moiety has facilitated the formation of colorimetric anion sensors that work both in organic or aqueous solutions. Such charge neutral receptor motifs have also been incorporated into organic scaffolds with norbomyl and calixarene backbones, which have enabled us to produce anion directed self-assembled structures.     

Dual Role of the 1,2,3‐Triazolium Ring as a Hydrogen‐Bond Donor and Anion–π Receptor in Anion‐Recognition Processes

Several bis(triazolium)‐based receptors have been synthesized as chemosensors for anion recognition. The central naphthalene core features two aryltriazolium side‐arms. NMR experiments revealed differences between the binding modes of the two triazolium rings: one triazolium ring acts as a hydrogen‐bond donor, the other as an anion–π receptor. Receptors 9²⁺?2BF₄ ^? (C₆H₅), 11²⁺?2BF₄ ^? (4‐NO₂?C₆H₄), and 13²⁺?2BF^4? (ferrocenyl) bind HP₂O₇^3? anions in a mixed‐binding mode that features a combination of hydrogen‐bonding and anion–π interactions and results in strong binding. On the other hand, receptor 10²⁺?2 BF₄ ^? (4‐CH₃O?C₆H₄) only displays combined Csp₂?H/anion–π interactions between the two arms of the receptors and the bound anion rather than triazolium (CH)⁺???anion hydrogen bonding. All receptors undergo a downfield shift of the triazolium protons, as well as the inner naphthalene protons, in the presence of H₂PO₄^? anions. That suggests that only hydrogen‐bonding interactions exist between the binding site and the bound anion, and involve a combination of cationic (triazolium) and neutral (naphthalene) C?H donor interactions. Theoretical calculations relate the electronic structure of the substituent on the aromatic group with the interaction energies and provide a minimum‐energy conformation for all the complexes that explains their measured properties.     

阴离子荧光受体研究进展

本文总结了近年来阴离子荧光受体的研究进展和荧光化学传感的主要机理,主要 介绍以下3类受体的设计合成及其在阴离子识别中的应用:(1)以氢键或静电作用键合阴 离子的受体(包括酰胺、脲及硫脲、胍盐和硫脲盐、五员杂环);(2)含金属和路易斯酸的受体;(3)以竞争键合机制识别阴离子的"化学传感体系".     

Thiourea Based Tweezer Anion Receptors for Selective Sensing of Fluoride Ions

Three 3,3＇-di（4-substituted-phenyl）-1,1＇-isophthaloylbis（thiourea） compounds were designed as novel neutral anion receptors, and synthesized by simple steps in good yields. The single crystal structure of receptor 1 shows that a solvent molecule was captured by the host molecule through intermolecular hydrogen bonding. Moreover, it was self-assembled as a supramolecular system for the presence of abundant inter- and intramolecular hydrogen bonding and π-π interactions between phenyl groups. Their application as anion receptors has been examined by UV-Vis and ^1H NMR spectroscopy, showing that they had a higher selectivity for fluoride than other halides. The host and guest formed a 1 ： 1 stoichiometry complex through hydrogen bonding interactions in the first step, then following a process of deprotonation in presence of an excess of F^- in the solvent of DMF.     

Crystallographic and Solution Anion Binding Studies of Bis-amidofurans and Thiophenes

A variety of furan and thiophene amide and thioamide cleft type anion receptors have been synthesised and crystallographically characterised. Unlike 2,5-diamidopyrrole anions, analogous 2,5-diamidofurans and thiophenes do not interlock in the solid state. The anion binding properties of these receptors have been investigated in DMSO/0.5% water solution using ¹H NMR titration techniques. Solution studies and solid-state evidence suggests that the thiophene receptors may utilise a thiophene CH hydrogen atom for hydrogen bond formation to anions with a 2,4-diamidothiophene showing similar anion binding affinities to a 2,5-diamidopyrrole.     

Thermodynamic Study of Dihydrogen Phosphate Dimerisation and Complexation with Novel Urea‐ and Thiourea‐Based Receptors

Complexation of dihydrogen phosphate by novel thiourea and urea receptors in acetonitrile and dimethyl sulfoxide was studied in detail by an integrated approach by using several methods (isothermal titration calorimetry, ESI‐MS, and ¹H NMR and UV spectroscopy). Thermodynamic investigations into H₂PO₄^? dimerisation, which is a process that has been frequently recognised, but rarely quantitatively described, were carried out as well. The corresponding equilibrium was taken into account in the anion‐binding studies, which enabled reliable determination of the complexation thermodynamic quantities. In both solvents the thiourea derivatives exhibited considerably higher binding affinities with respect to those containing the urea moiety. In acetonitrile, 1:1 and 2:1 (anion/receptor) complexes formed, whereas in dimethyl sulfoxide only the significantly less stable complexes of 1:1 stoichiometry were detected. The solvent effects on the thermodynamic parameters of dihydrogen phosphate dimerisation and complexation reactions are discussed.     

Chloride‐Anion‐Templated Synthesis of a Strapped‐Porphyrin‐Containing Catenane Host System

The synthesis, structure and anion‐recognition properties of a new strapped‐porphyrin‐containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor–acceptor and coordinative pyridine–zinc interactions. The [2]catenane incorporates a three‐dimensional, hydrogen‐bond‐donating anion‐binding pocket; solid‐state structural analysis of the catenane?chloride complex reveals that the chloride anion is encapsulated within the catenane’s interlocked binding cavity through six convergent CH????Cl and NH???Cl hydrogen‐bonding interactions and solution‐phase ¹H NMR titration experiments demonstrate that this complementary hydrogen‐bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution.     

Synthesis,photophysical and NMR evaluations of thiourea-based anion receptors possessing an acetamide moiety

The synthesis and photophysical evaluation of three diaryl thiourea-based anion receptors (4–6) for comparison with their urea counterparts (1–3) is outlined. These anion receptors posses an acetamide functionality on one of the aryl groups and an electron-withdrawing CF₃ group on the other. By varying the position of the acetamide group, in the o-, m- and p-positions of 4–6, respectively, the anion binding ability was both tuneable and found to be, in some cases, significantly different from that seen for the urea analogues 1–3. The binding affinities of the receptors 4–6, as well as the binding stoichiometries, were evaluated using UV–vis absorption spectroscopy in MeCN. However, these receptors were not sufficiently emissive to quantify the anion recognition using fluorescence. The results confirmed strong binding of these receptors to anions such as fluoride, acetate, phosphate, pyrophosphate and chloride. Nevertheless, the overall results obtained did not conform to the anticipated trends seen for 1–3, which is most likely due to the enhanced binding affinity of the thiourea analogues 4–6. The binding interactions were also investigated by using ¹H NMR which confirmed that these receptors interacted with the anions in a stepwise manner, where the primary anion binding interaction occurred at the thiourea side, which led to an activation of the acetamide moiety towards the second anion binding interaction, an example of an allosteric activation mode.     

Anion recognition by a family of quinoline-functionalised bis-amide hosts in solid state and in solution

The interaction between a series of bidentate, amide-functionalised 8-oxyquinoline receptors and coordinating anions is investigated. Anion recognition properties and conformations were studied by solid-state structures, Hartree–Fock calculations and solution-phase ¹H NMR investigations. Our findings suggest that the amide-oxyquinoline motif coordinates anions and water with a well-defined, consistent geometry involving multiple hydrogen bonds. Solution studies of the neutral receptors reveal the unprotonated oxyquinoline ring to indirectly contribute to anion binding by the adjacent amide NH groups despite being unable to directly participate through hydrogen bonding.     

New Tetrafunctionalized Cone Calix[4]arenes as Neutral Hosts for Anion Recognition

Abstract

The synthesis and anion binding properties of several new cone calix[4]arenes having different flexibility and tetrafunctionalized at the upper rim with various type of hydrogen bonding donor groups such as thioureas (1–3), trifluoroacetamides (4, 5) and perfluorinated alcohols (6) are reported. The results obtained show that thiourea receptors are the most effective in the complexation of all anions and that the rigid cone compound 2 is more efficient than the mobile cone analog 1 in the binding of spherical anions, whereas the reverse is true for the complexation of tetrahedral H₂PO₄ ^? anion.     

Urea/thiourea-based colorimetric chemosensors for the biologically important ions: efficient and simple sensors

Some colorimetric anion sensors have been synthesized where 4-nitrophenyl was treated as a signaling unit and urea/thiourea moieties as binding sites. The receptors, effectively and selectively, recognized the biologically important F⁻ and carboxylate anions from other anions such as Cl⁻ and Br⁻ in DMSO.     

Recognition of carboxylate and dicarboxylates by azophenol–thiourea derivatives: a theoretical host–guest investigation

Geometries of azophenol–thiourea derivative complexes with acetate, oxalate, malonate, succinate, glutarate, adipate, pimelate, suberate and azelate were carried out using the integrated MO:MO method. The binding and complexation energies of these complexes were derived from the ONIOM(B3LYP/6-31G(d):AM1) calculations. The relative stabilities of the complexes of azophenol–thiourea derivatives with carboxylate guests are reported. The binding interactions of the azophenol–thiourea receptor 1, 2 and carboxylate guests are described as multipoints hydrogen bonding, where the amine and phenolic hydrogen atoms of receptors act as hydrogen bond donors in complex with acetate and all amine-hydrogen and phenolic hydrogen atoms act as hydrogen bond donors in complex with dicarboxylate guests. Thermodynamic properties of binding interactions between receptors 1, 2 and their preorganizations and complexations are also reported.     

Molecular association in polyethylene glycol

Summary Existence of intra and intermolecular hydrogen bonds has been confirmed in the literature. Present reduced viscosity studies of PEG solution in urea and thiourea also confirm the view of the presence of the molecular association of PEG in water by intermolecular hydrogen bonding as well as of the existence of intramolecular hydrogen bonding in PEG molecules. The existence of intramolecular hydrogen bonding is more appreciated in the case of PEG solution in relatively smaller concentration of urea and thiourea. The presence of urea and thiourea is responsible for the breaking of hydrogen bonds which result in the change of molecular size and conformation.

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Zusammenfassung Das Auftreten von intra- und intermolekularen Wasserstoff bindungen bei Polymeren wird in der Literatur schon bestätigt. Wir zeigten an Polyäthylenglycollösungen in Wasser mit und ohne Harnstoff und Thioharnstoff, daß sich die Existenz von solchen Wasserstoffbrücken in vorliegendem Falle ebenfalls bestätigen läßt.

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