Anion Binding Ability Research Articles

The anion recognition properties of hydrazone derivatives containing anthracene

A series of artificial receptors, hydrazone derivatives containing anthracene, have been designed and synthesized. The interaction of these receptors with biologically important anions was determined by UV–vis, fluorescence and 1H NMR titration experiments and theoretical investigation. Results indicate that the receptor ( 1) without NO 2 shows no binding ability for various anions. The other receptors ( 2 and 3) show the highest binding ability for acetate (AcO −) among studied anions (fluoride (F −), dihydrogen phosphate (H 2PO 4 −), chloride (Cl −), bromide (Br −), iodide (I −)); and the binding ability for AcO − is not interfered by the existence of other anions. The additions of AcO −, F − and H 2PO 4 − can arouse different degrees of fluorescence quenching. 1H NMR titration shows that the interaction between the receptor 2 and F − firstly depends on the hydrogen-bond formation; later the interacted site NH is deprotonated and the added F − forms hydrogen bond with the near CH in Schiff base. Moreover, visual color changes accompany guest binding, enabling this system to act as colorimetric anion sensors.

Synthesis, structural characterization, and anion binding ability of sterically congested adamantane-calix[4]pyrroles and adamantane-calixphyrins

Novel adamantane derivatives of calix[4]pyrroles 4– 8 and calixphyrin 9 have been synthesized. The structure of 8 has been characterized by X-ray powder diffraction and the structure of 9 by single crystal X-ray analysis. Whereas calixphyrin 9 does not bind anions, analogous calyx[4]pyrrole 8 forms a complex with Cl − in the DMSO solution and in the solid state. The solid state complexation has been accomplished on grinding in a mill, which is the first example of complex formation with an anion in the solid state.

Selective Colorimetric Fluoride Sensor: A Heteroditopic Receptor Combining Pyrrolic Amide with Urea

AbstractA heteroditopic anion receptor, bearing one pyrrolic amide site and a urea site, has been synthesized. UV‐Vis spectrum studies in CH3CN solution revealed that the receptor had higher anion binding ability than the homoditopic one. A naked‐eye detectable color change, from colorless to yellow, of the receptor solution took place when fluoride was added, which indicates that the receptor has potential application to selective colorimetric fluoride sensing.

Anion recognition properties of the neutral receptors bearing amide macrocycle

Abstractmagnified imageNeutral classes of amide‐based macrocycle have been synthesized and the anion binding abilities are assessed by UV‐vis titration and 1H nmr experiments. Results indicate that higher anion binding abilities are observed for H2PO4−, F− and AcO−, but almost no affinity for Cl−, Br−, I− and OH−. The 1H nmr spectra shows that the interactions between the receptors and fluoride anion depend on two factors, respectively: one is depend on hydrogen bonding, the other on deprotonation.

Study on Anion Electrochemical Recognition Based on a Novel Ferrocenyl Compound with Multiple Binding Sites

A novel ferrocenyl anion receptor N, N, N, N-(dimethyl, ethyl, ferrocenecarboxylic amidodimethylene) ammonium fluoborate 2 with multiple binding sites was synthesized. Its anion recognition behaviors were investigated by CV, 1H NMR and UV-vis spectrum. It was found that the combination of two interactions enforced the anion binding ability and the binding selectivity of 2 to phosphate anion. The effects of scan rate on the CV curves of 2 with phosphate were also investigated. In different scan rate, the CV curves kept stable which indicated the strong binding between 2 and phosphate. According to relationships of peak potential, peak currents and scan rate of 2 binding with phosphate, the kinetic parameters of electrode process such as diffusion coefficient Dapp, surface transfer coefficient alphan alpha, and standard rate constant k0 were calculated.

Gradual Transition from NH···Pyridyl Hydrogen Bonding to the NH···O Tape Synthon in Pyridyl Ureas

We report the synthesis and X-ray crystal structures of a series of pyridyl ureas of the type currently topical in anion binding and supramolecular gelation applications, along with their anion-binding ability in solution. The structures of the simple pyridyl ureas are dominated by urea···N(pyridyl) hydrogen bonding, because of steric congestion of the urea carbonyl by intramolecular CH···O interations. However, introducing a further competing synthon in the form of alkenic or π-stacking interactions causes a gradual changeover, through a number of interesting intermediate hydrogen bonding motifs, to the urea α-tape arrangement.

Calix[4]arene‐Based Enantioselective Fluorescent Sensors for the Recognition of N‐Acetyl‐aspartate

AbstractTwo‐armed chiral anion receptors (1 and 2), calix[4]arenes bearing dansyl fluorophore and (1R,2R)‐ or (1S,2S)‐1,2‐diphenylethylenediamine binding sites, were prepared and examined for their chiral amino acid anion binding abilities by the fluorescence spectra in dimethylsulfoxide (DMSO). The results of non‐linear curve fitting indicate that 1 or 2 forms a 1:1 stoichiometry complex with N‐acetyl‐L‐ or D‐aspartate by multiple hydrogen bonding interactions, exhibiting good enantioselective fluorescent recognition for the enantiomers of N‐acetyl‐aspartate, [receptor 1:Kass(D)/Kass(L)=6.74; receptor 2:Kass(L)/Kass(D)=6.48]. The clear fluorescent response difference indicates that receptors 1 and 2 could be used as a fluorescent chemosensor for N‐Acetyl‐aspartate.

Anion binding properties of indolylmethanes

The anion binding properties of the indolylmethanes (1) were investigated by 1H-NMR spectroscopy in CDCl3. Tris(3-methylindol-2-yl)methane (1a) selectively bound a chloride anion the over other tested anions (Br−, I−, HSO4−, and NO3−). In contrast, analogous compounds, phenyl bis(3-methylindol-2-yl)methane (1b), 2-hydroxyphenyl bis(3-methylindol-2-yl)methane (1c), tri(indol-3-yl)methane (1d), and phenyl di(indol-2-yl)methane (1e), showed a low anion binding ability and selectivity. These results indicate that the number and a position of the binding sites (indole NH protons) of the indolylmethanes are important factors for the formation of the complex with an anion. The high binding ability and selectivity of 1a toward a chloride anion is attributed to the proper size of the binding pocket for a chloride anion and the formation of multiple hydrogen bonds between the three indole NH protons and a chloride anion. The anion affinity of 1a was significantly affected by the cation component of quaternary ammonium salts, indicating that it is ion pair binding and not solely anion binding.

Visible Colorimetric Sensor for Fluoride Ion Based on o-Phenylenediamine

A new chromogenic receptor based on 1,2-phenylene derivative containing thiourea moieties is synthesized and examined for its anion binding ability by UV–Vis and 1H NMR studies. The results show that the receptor has selective colorimetric sensing of fluoride over all other anions like chloride, bromide, iodide, nitrate, hydrogen sulphate and acetate.

Ferrocene‐based derivative bearing phenol group recognitive sites: efficient H2PO4− receptor

AbstractTwo artificial receptors, bearing ferrocene and phenol groups, were synthesized and their anion‐binding properties were evaluated for F−, Cl−, Br−, I−, AcO− and $\hbox{H}_{2}\hbox{PO}_{4}^{-}$ by UV–vis, 1H NMR titration and cyclic voltammetry experiments in order to research the effect of different substituents on anion‐recognition properties. Results indicate that the anion binding abilities can be effectively tuned by introducing a nitro group in the ortho position of the phenyl ring of the receptors, and the most obvious effect is for $\hbox{H}_{2}\hbox{PO}_{4}^{-}$. Copyright © 2007 John Wiley & Sons, Ltd.

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.

Conformational Control of Selectivity and Stability in Hybrid Amide/Urea Macrocycles

The anion-binding properties of two similar hybrid amide/urea macrocycles containing either a 2,6-dicarboxamidophenyl or a 2,6-dicarboxamidopyridine group are compared. Significant differences in anion affinity and mode of interaction with anions are attributed to the presence of intramolecular hydrogen bonds in the pyridine system. In fact, remarkably, the phenyl macrocycle undergoes amide hydrolysis under neutral conditions in DMSO/water. The anion binding abilities of the receptors are compared to those of acyclic analogues of the macrocycles that show that the phenyl receptor behaves in a similar fashion to acyclic urea-containing receptors (i.e., showing little selectivity amongst oxo anions), whilst the pyridine-containing receptor shows a high affinity and selectivity for carboxylates.

Colorimetric and fluorescence sensing of anions using thiourea based coumarin receptors

Thiourea-containing coumarins 1, 2 have been designed and synthesized via reaction of 6-aminomethylcoumarin and the corresponding isothiocyanates. Their anion-binding ability has been examined using UV–vis, fluorescence and 1H NMR. The anion recognition takes place through charge neutral thiourea receptor sites with concomitant fluorescence quenching of the coumarin moiety with 1 showing a strong binding to C 6H 5COO − over F − with a distinct change in color.

Selective Colorimetric Sensing of Cyanide Ions Over Fluoride Ions by Calix[4]arene Containing Thiourea Moieties

A new calix[4]arene derivative in 1,3-alt conformation containing thiourea moieties is synthesized and examined for its anion binding ability by UV-Vis and 1H NMR studies. The results show that the receptor has selective colorimetric sensing of cyanide over all other anions like fluoride, chloride, bromide, iodide, nitrate, hydrogen sulphate, dihydrogenphosphate and acetate. Keywords: Anion sensing, colorimetric, calix[4]arene, thiourea, recognition

Anion Binding versus Intramolecular Hydrogen Bonding in Neutral Macrocyclic Amides

Although amide groups are important hydrogen-bond donors in natural and synthetic anion receptors, studies on structure-affinity relationships of amide-based macrocyclic receptors are still very limited. Therefore, we synthesized a series of macrocyclic tetraamides 5-8 derived from 1,3-benzenedicarboxylic (isophthalic) acid and aliphatic alpha,omega-diamines of different lengths. (1)H NMR titrations in DMSO solution show that the anion affinity of these receptors decreases with increasing size of the macrocycle irrespective of the anion, and this suggests a minor role of geometric complementarity. Comparison with their previously studied pyridine congeners reveals that the isophthalic acid based macrocycles are less potent, in contrast to what was found for simple model diamides. Combined theoretical and experimental structural studies were carried out to determine the reasons behind this behaviour. The results show that the unexpectedly low anion binding ability of the isophthalic acid-based receptors is due to the self-complementary nature of the isophthalic bis-amide fragments: when two such moieties are present within a sufficiently flexible macrocycle, they adopt syn-anti conformations and bind each other by two strong intramolecular hydrogen bonds that close the macrocyclic cavity. Nevertheless, anion binding is able to break these hydrogen bonds and switch a macrocycle into a convergent all-syn conformation. Despite the ill-preorganized conformation, 20-membered receptor 6 is better than either its open-chain analogue (macrocyclic effect) and/or its isomer having differently placed carbonyl groups. The crystal structures of four anion complexes of the macrocyclic receptors are reported. X-ray studies and solution NMR data confirmed the inclusive nature of the complexes and pointed to strong involvement of aromatic CH hydrogen atoms in anion binding.

The recognition and sensing of anions by a novel phenanthroline-bridged diamide

A novel neutral anion recognition receptor 1 with the additional capability of selectively sensing anionic guest species has been synthesized and examined for its anion-binding abilities by UV–vis absorption spectroscopy. The results of nonlinear curve fitting and Job plot indicate that 1 forms 1:1 stoichiometric complexes with fluoride, chloride, bromide, iodide, and acetate, respectively. Their UV–vis absorption spectra in DMSO indicate the presence of anions such as F –, Cl –, Br–, I–, and AcO– with high affinity ability and selectivity toward F –, and also show dramatic colour changes from colourless to yellow in the presence of TBAX (1× 10–5 mol/L, X= F –, Cl –, Br–, I –, and AcO–). Receptor 1 has almost no affinity abilities for H2PO4– and OH–. Key words: phenanthroline-bridged diamide, synthesis, UV–vis spectrum, anion recognition.

New Neutral Receptors for Fluoride Based on Calix[4]arene Bearing Thiourea and Amide

Two-armed neutral anion receptors (4, 5), calix[4]arenes bearing 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-).

Density functional theory studies of β-substituent effect on conformational preference and anion binding ability of calix[4]pyrroles

The conformational features and anion-binding properties of a series of β-octasubstituted calix(4)pyrroles have been investigated by the BLYP method of density functional theory with the 6-31+G** basis set both in the gas phase and in CH2Cl2 solution. The calculations demonstrated that adjusting the electronic properties of β-substituents on the pyrrole rings do change the anion-binding ability of calix(4)pyrroles. With the BLYP/6-31+G** method in CH2Cl2 solution, the relative binding energies follow the order of electron withdrawing abilities of the substituents, i.e. CN (18kcal/mol) >> Cl (7 kcal/mol) > Br (4 kcal/mol) > H (0 kcal/mol). Calculations also indicate that the energy difference between the most stable 1,3-alternate conformation and the least stable cone-conformation that is for anion-binding is increased by electron-withdrawing β-substituents CN, Cl, and Br. Further analysis on dipyrromethane models reveals that the destabilization of the cone-conformation is mainly caused by electrostatic interactions between the β-substituents on the adjacent pyrrole rings. Our results thus provide useful information for designing stronger and more efficient calix(4)pyrrole-based anion binding receptors.

A fluorescence-active 1,3-bis(isothiouronium)-derived naphthalene exhibiting versatile binding modes toward oxoanions in aqueous MeCN solution: new methodology for sensing oxoanions

A unique binding property of the PET (photoinduced electron transfer) sensor 1 is described, in which a naphthalene moiety at the 1,3-positions is attached by isothiouronium units that serve as anion-binding units. Fluorescence emission ( λ max=339 nm) was significantly switched on at an excitation wavelength of 279 nm upon recognition of anion in 6% (v/v) H 2O/MeCN solution at 25 °C. Titration curves with HPO 4 2− and AcO − differ greatly; that with HPO 4 2− shows a stoichiometric 2:1 host-to-guest binding, whereas that with AcO − shows a biphasic 1:1 and 1:2 host-to-guest binding, reflecting principally the charged shapes of the oxoanions. This finding is attributable to the plural built-in isothiouronium units with a high anion-binding ability, and suggests a new way to develop fluorescent sensors for oxoanion recognition.

Calix[4]arenes containing thiourea and amide moieties: neutral receptors towards alpha,omega-dicarboxylate anions.

Two-armed neutral anion receptors (4,5), were prepared and examined for their anion-binding ability using UV-vis, fluorescence and 1H NMR spectra in DMSO. The results of non-linear curve fitting indicate that 4 or 5 form 1 : 1 stoichiometric complexes with dicarboxylate anions by multiple hydrogen bonding interactions and the sensitivity for recognition of dicarboxylate depends on the chain length of these dicarboxylate anions. Receptors 4 and 5 have no binding ability with acetate, dihydrogen phosphate and the halogen (Cl-, Br-, I-) anions. This demonstrates that receptors 4 or 5 could be used as chemical sensors for some special dicarboxylate anions.