Unique fluoride anion complexation in basic media by 5,5-dioxophenothiazine bis(phenylurea) and bis(phenylthiourea)

The anion recognition properties of the newly synthesized 5,5-dioxophenothiazine bis(phenylurea) and bis(phenylthiourea) were investigated in acetonitrile using UV–vis spectroscopy. While most of the studied anions were bound only by the neutral receptors, fluoride and acetate were complexed even by the deprotonated ones.     

Synthesis and anion recognition studies of new ureylbenzamide-based receptors

A new group of ureylbenzamide-based receptors (1–4) has been synthesized; its binding affinity and capacity to form supramolecular complexes in solution with different anions have been investigated. For designing these receptors, it was considered a combination of the positions of the urea and amide groups (ortho and meta), and the chromophore groups naphthyl and nitrophenyl, yielding four receptors. The position and chromophore structure affected the acidity of the urea and amide hydrogens in the order 4>3>2>1. All the spectroscopic studies showed a significant change of 1 and 2 compared with 3 and 4 in the presence of different TBAX salts in acetonitrile. The ¹H-NMR spectra show a preferential interaction of the anions with the urea group in receptors 1 and 2 due to the less steric hindrance, while there is a cooperative interaction of amide group in receptors 3 and 4 due to the closeness of both groups.     

Synthesis and anion recognition properties of pyrrole-bearing acyclic receptors

A new series of acyclic anion receptors (1-4) based on methyl 5-(aminomethyl)-1H-pyrrole-2-carboxylate were designed and synthesized. The anion recognition properties of these receptors were examined by ¹H NMR spectroscopy and rationalized by density functional theoretical calculation. Receptor 1 displays the highest affinity and selectivity for anionic guests mainly due to the intramolecular hydrogen bonds and rigid molecular geometry.     

Tripodal naphthalene ether ligand: Solid-state anion recognition and fluorescence studies

The simple tripodal amine ligand Tris-[2-(naphthalen-1-yloxy)-ethyl]-amine (L₁) was screened for anion recognition. Four crystal structures confirmed the inorganic as well as organic anion recognition in the solid state. Solid-state structures are results of supramolecular self-assembly and 3D molecular network involves C–HO and C–Hπ bonding in the crystal lattice. In the solid state, it forms a strong C–HCl and C–HO type interactions with the anions. This anion recognition was also confirmed by steady state fluorescence spectroscopy. In complex 4, L₁ is confined between 2D hydrogen bonded sheet formed by pyromellitic acid anion. L₁ shows unusually high selectivity toward nitrate in solution resulting in both a dramatic color change and a concomitant quenching of luminescence.     

Size complementarity in anion recognition by neutral macrocyclic tetraamides

Comparison of the anion binding properties of a series of uncharged macrocyclic tetraamides reveal significant effects of the receptor's size on the strength of its anion complexes. This study allowed for estimation of the optimal size of a macroring for complexation of common anions.     

Synthesis and enantiomeric recognition studies of a novel 5,5-dioxophenothiazine-1,9 bis(thiourea) containing glucopyranosyl groups

A novel optically active 5,5-dioxophenothiazine-1,9 bis(thiourea) containing glucopyranosyl groups was synthesized and its enantiomeric recognition properties were examined towards the enantiomers of tetrabutylammonium salts of chiral α-hydroxy and N-protected α-amino acids using UV–vis spectroscopy.     

硫脲类阴离子受体的设计合成与阴离子识别

硫脲类化合物具有生物活性,是优良的氢键供体,与阴离子特别是含氧阴离子形成氢键配合物。本文设计合成了系列二苯基硫脲衍生物,通过取代基效应调控硫脲衍生物分子内电转移过程,阴离子与硫脲基团结合后,增强了分子内供体的给电子能力,进一步促进电荷转移过程,据此识别不同的阴离子。由于主体分子与阴离子间形成氢键的能力及阴离子碱性的差异,可达到选择性结合的目的。     

A novel calix[4]arene fluorescent receptor for selective recognition of acetate anion

A novel bridged fluorescent calix[4]arene with 1,8-diaminoanthracene and glycine at the upper rim has been prepared, which exhibited selective recognition towards AcO⁻ over other anions such as F⁻, Cl⁻, Br⁻, , , I⁻ and by fluorescence spectroscopy and ¹H NMR method.     

Multi-step regulation of anion recognition by redox-active pseudocryptand

We synthesized an artificial redox-active Fe-pseudocryptand as an anion receptor to respond to electrochemical oxidation and reduction. Spectroscopic study and X-ray crystallography showed that the assembled urea chains and the isocyanuric platform generate an anion-binding cavity through favorable multiple hydrogen bonds and anion-π interactions. As the positive charge of the Fe center increases, the anion affinity is effectively increased due to an enhanced electrostatic interaction between the Fe atom and the anionic guest. This is the first efficient multi-step regulation of Cl⁻ selective anion recognition by the redox-active pseudocryptand.     

Spectroscopic and spectrometric studies of anion recognition with calix[4]pyrroles in different reaction conditions

The binding studies of calix[4]pyrroles (1–6) with fluoro, chloro, bromo, iodo and sulphato anions generated from normal-tetrabutylammoniumfluoride, normal-tetrabutylammoniumchloride, normal-tetrabutylammoniumbromide, normal-tetrabutylammoniumiodide, and normal-tetrabutylammoniumsulphate respectively were investigated by electrospray ionization mass spectrometry (ESI-MS) in dichloromethane–acetonitrile in negative ion mode. The efficacy of a particular calix[4]pyrrole to bind with anions was found maximum at low cone voltage of the instrument, at high cone voltage the binding was suppressed due to removal of anion from the cavity of the macrocycles. The binding strength was found inversely proportional to the size of anion for a particular calix[4]pyrrole. The fragmentation pattern of calix[4]pyrrole was observed at higher cone voltage of ESI-MS and was interpreted. The association constants of calix[4]pyrroles and anions obtained from electronic transition studies were in good agreement with that observed from ¹H NMR titration studies.     

5,5-Diaryldipyrromethanes: syntheses and anion binding properties

A two-step synthesis of 5,5-diaryldipyrromethanes in good yields is described. The adopted synthetic strategy can be used to tune the substituent at the meso-carbon very easily by choosing the Grignard reagent of interest. Further, the influence of the incorporation of various diaryl units at the meso-carbon atom in the inherent anion binding affinities of the dipyrromethanes through hydrogen bonding was discussed.     

A novel neutral receptor for selective recognition of H2PO 4 −

A new urea-based receptor was designed to selectively recognize H₂PO₄⁻ among other anions (such as F^-, Cl^-, Br^-, I^-, OH^-, AcO^-) in organic solvent (DMSO) through intermolecular hydrogen bonding. Addition of anions to the receptor caused changes in UV–vis spectrum which provided the first indication of its anion binding ability. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Simple indole-based colorimetric sensors with electron-withdrawing chromophores: Tuning selectivity in anion sensing

Three simple colorimetric anion sensors (1, 2, and 3) containing anthrone, 1,3-indanedione, and malononitrile as signaling chromophores and an indole binding site have been designed and synthesized. The introduction of electron-withdrawing groups can not only provide chromogenic signal output, but also tune the sensitivity and selectivity of indole-based anion sensors by electron push–pull features. Their anion binding and sensing properties were investigated in detail by dramatic color changes, UV–vis absorption, and ¹H NMR. As results revealed, sensor 1 showed high selectivity for F⁻ over AcO⁻ and H₂PO₄⁻ with a distinct change in color due to the deprotonation of indole NH group. The excellent selectivity of 1 for F⁻ can be attributed to the fitness in the acidity of its NH-group, which is tuned to be able to distinguish the subtle difference in the affinity of F⁻, AcO⁻, and H₂PO₄⁻ to NH proton.     

一种双腙受体的合成及阴离子识别性能研究

设计合成了一种含双腙类阴离子受体1(5-甲基双水杨醛-2,4-二硝基苯腙)。用紫外-可见吸收光谱、荧光光谱考察了其与AcO-,H2PO4-,F-,Cl-,Br-和I-阴离子的作用。当加入AcO-、F-和H2PO4-时,受体分子1的吸收光谱发生明显的红移,与此同时溶液颜色由浅粉色变为紫色,而加入其他阴离子则无变化。通过在DMSO-d6核磁滴定实验进一步研究受体1和F-相互作用的本质。     

The anion recognition properties of Schiff base or its reductive system based on 2,2′-bipyridine derivatives

Two novel artificial receptors, 2,2′-bipyridine derivatives containing phenol group, have been designed and synthesized. The interaction of the receptors containing Schiff base or its reductive system with biologically important anions was determined by UV–vis and ¹H NMR titration experiments. Results indicate that receptors 1 and 2 show the strong binding ability for dihydrogen phosphate (H₂PO₄⁻), fluoride (F⁻), acetate (AcO⁻) and almost no binding ability for chloride (Cl⁻), bromide (Br⁻), iodide (I⁻). At the same time, the strongest binding ability of receptor 1 for H₂PO₄⁻ among studied anions is not influenced by the existence of other anions; as well as receptor 2 for F⁻. In addition, the binding ability of receptor 1 (Schiff base system) with various anions is stronger than that of receptor 2 (the reductive Schiff base system) due to the difference of electronic effect.     

Experimental and computational studies of anion recognition by pyridine-functionalised calixarenes

Calix[4]arene-based receptors linked to amide and pyridine moieties have been synthesised in four steps from calix[4]arene, and characterised by ¹H and ¹³C NMR spectroscopy. The recognition properties of these receptors towards different anions were evaluated using ¹H NMR and computational studies. The receptors show modest selectivities towards dihydrogen phosphate versus carboxylates.     

A [2]catenane containing an upper-rim functionalized calix[4]arene for anion recognition

A novel [2]catenane is synthesized in good yield from an upper-rim functionalized calix[4]arene macrobicycle and a nitro-substituted isophthalamide threading component in the presence of a chloride anion template via a ring-closing metathesis (RCM) reaction. After halide anion template removal the resulting catenane host exhibits a high degree of selectivity for chloride in competitive organic solvent mixtures.     

An efficient thiourea-based colorimetric chemosensor for naked-eye recognition of fluoride and acetate anions: UV-vis and HNMR studies

An efficient colorimetric chemosensor with a thiourea binding site and 2-amino-6-nitrobenothiazole as a signaling unit has been synthesized by dithiocarbamate approach. The chemosensor has been utilized for selective recognition of fluoride and acetate anions in dry DMSO solution by UV-vis and ¹H NMR titration experiments. The chemosensor has shown naked-eye sensitivity for both the anions in solution.     

Molecular recognition studies with a simple dipyrrinone

We present our investigations of 2-ethyl-3-methyl-(10H)-dipyrrin-1-one, its self-association, and anion binding properties. This receptor is easily accessible in a facile single step synthesis with a straightforward workup. An examination of the concentration dependence of the dipyrrinone NH chemical shifts in CDCl₃ and (CDCl₂)₂ over the temperature range from −20 °C to 100 °C determined the self-association constant to be 3850 M⁻¹. Molecular recognition studies have shown that it has a preference for guests with an OH moiety, such as hydrogen sulfate (HSO₄⁻) and carboxylic acids (RCO₂H).