Thiourea Binding Site Research Articles

Selective and sensitive colorimetric cyanide recognition in aqueous medium and food samples based on Ni(II) complex chemosensor

Since cyanide is highly toxic that can lead to respiratory arrest and death, it is important to develop practical diagnostic methods for the sensing of cyanide. In this study, the colorimetric sensing of cyanide was achieved by a nickel complex (NiC) sensor with thiourea binding sites. NiC was prepared and characterized by 1H NMR, single-crystal X-ray crystallography, FTIR, and Mass spectra. When the cyanide and sulfide ions were added to NiC sensor, the color changed from light yellow to canary yellow and pale yellow to golden yellow, respectively. NMR titration results confirmed that the colorimetric response toward cyanide resulted from the deprotonation and formation of a guest–host complex. A binding mechanism is proposed based on the mass spectra, 1H NMR titration, and stoichiometry studies. The binding constant and detection limit of the NiC sensor toward cyanide was also investigated. The detection limits of NiC toward cyanide and sulfide reached 35.4 nM and 28.7 nM, respectively, lower than the World Health Organization (WHO)-allowed cyanide concentration in drinking water. The NiC complex possesses high selectivity to cyanide and sulfide through deprotonation of the –NH- protons. The detection of trace amounts of cyanide ions in natural food samples, such as cassava flour and sprouting potatoes, was also achieved by the NiC sensor.

An aniline trimer-based multifunctional sensor for colorimetric Fe3+, Cu2+ and Ag+ detection, and its complex for fluorescent sensing of L-tryptophan

The detection of metal ions and amino acids by the aniline oligomer-based receptor has not been reported yet, to the best of our knowledge. In this study, an efficient multifunctional cation-amino acid sensor (CAS) with aniline moiety and chiral thiourea binding site was synthesized by the reaction of aniline trimer and (S)-(+)-1-phenyl ethyl isothiocyanate. CAS can sense Fe3+, Cu2+, Ag+ ions, and L-tryptophan. These results can be recognized by the naked eye. The appropriate pH range for the quantitative analysis of Fe3+, Cu2+, and Ag+ by CAS in DMSO/water (30vol% water) was evaluated. The interaction between CCS and metal ions was analyzed by 1H NMR titration. The detection limits of CAS for the Cu2+, Ag+, and Fe3+ were 0.214, 0.099, and 0.147μM, respectively. Moreover, the CASCu2+ complex can act as a turn-on fluorescence sensor for L-tryptophan. On the contrary, there is no response upon the addition of other amino acids, such as L-histidine, L-proline, L-phenylalanine, L-threonine, L-methionine, L-tyrosine, and L-cystine to CASCu2+ complex.

Proximity-Induced Reactivity and Product Selectivity with a Rationally Designed Bifunctional Peptide Catalyst

Cooperative catalytic systems are making significant advances in modern organic synthesis due to the potential to combine multiple catalytic cycles or enable enzyme-like proximity effects. We report the rational design of a bifunctional helical peptide catalyst that displays an imidazolidinone catalyst in close proximity to a thiourea binding site and enables proximity-enhanced reactivity and selectivity. The helical structure of the peptide and the binding of both reactants are shown to be essential for enhanced reactivity in Diels–Alder and indole alkylation reactions, and up to 28 000 catalyst turnovers are achieved. A variety of Lewis basic functional groups facilitate binding and proximity-enhanced reactivity, and product selectivity is observed that cannot be achieved in the absence of the peptide template.

A new dinuclear ferrocene with amide–thiourea binding sites for dual electrochemical sensing to Hg(II) and anions

A new dinuclear ferrocene-base receptor bearing amide and thiourea binding sites, 1, was prepared and characterized by X-ray crystal structure analysis. This receptor shows a dual electrochemical sensing to Hg(II) and anions. Upon the addition of Hg(II), its redox potential shows a positive shift for the mercury-promoted intramolecular cyclic guanylation mechanism. In addition, 1 also shows distinctive electrochemical sensing to H2PO4− over other anions with a large negative shift of its redox potential for N–H…anion hydrogen bond interaction between anion and 1.

Colorimetric anion sensor based on receptor having indole- and thiourea-binding sites

A new colorimetric sensor having nitro-substituted indole and bisthiocarbonohydrazone units for selective fluoride and acetate ions has been designed and synthesized.

Selective Extraction and Efficient Binding in a Protic Solvent of Contact Ion Triplets by Using a Thiourea‐Based Bis‐Calix[6]arene Receptor

AbstractWe report a D3h‐symmetric tail‐to‐tail bis‐calix[6]thiourea 5 that displays two divergent cavities triply connected by thiourea linkages. This calix[6]tube was efficiently synthesized through a [1+1] macrocyclization reaction and characterized by X‐ray diffraction analysis. The binding properties of this heterotritopic receptor were evaluated in a protic environment (i.e., CD3OD/CDCl3) through NMR studies. Thus, bis‐calix[6]thiourea 5 exhibits a remarkable ability in the cooperative complexation of an anion sandwiched between two ammonium ions, a high selectivity for ammonium sulfate salts being observed. The anion is bound through multiple hydrogen‐bonding interactions at the thiourea binding site and is in contact with the two ammonium ions accommodated in the cavities. The resulting quaternary complexes are rare examples of cascade complexes involving organic cations. Moreover, when wrapping around the anion, the thiourea linkers adopt a helical shape and the resulting chirality is sensed by the bound cations. In comparison with the parent amido‐ or urea‐based bis‐calix[6]arenes 1 and 2, bis‐calix[6]thiourea 5 behaves as a much more efficient receptor for organic ion triplets. This strengthening of the binding properties is likely due to the higher acidity of the thiourea groups and to their poor ability to self‐associate. Interestingly, we have obtained the first X‐ray structure of a bis‐calix[6]arene‐based cascade complex. It shows that these host–guest complexes are stabilized through a dense network of hydrogen‐bonding interactions. Finally, although sulfate salts are better recognized in CD3OD/CDCl3, the selective extraction of ammonium nitrate salts from water to chloroform was evidenced through NMR studies. This remarkable result can be rationalized by the weaker hydration of the nitrate anion and its good geometrical complementarity with the tris‐thiourea binding site.

Novel Polymeric Adsorbents Bearing Amide, Pyridyl, Azomethine and Thiourea Binding Sites for the Removal of Cu(II) and Pb(II) Ions from Aqueous Solution

Novel polyamides bearing pyridyl and azomethine groups as pendant pyridylformylimino groups along with thioamide moieties in the polymer backbone were synthesized using 4-pyridylformylimino-N-(phenyl,2′,5′-dicarboxylic acid) with 4,4′-(bisthiourea)benzidine and 4,4′- diaminodiphenyl methane through one pot phosphorylation polymerization technique. The optimization of experimental conditions and parameters including pH, adsorbent dosage, contact time, and initial metal ion concentration for the removal of heavy metal has also been investigated. Kinetic studies showed that the pseudo second order rate equation fits well with experimental values. The FT-IR spectrum indicated that the pyridine, amide, amide carbonyl, and azomethine groups were the major binding sites with metal ions. The maximum adsorption capacities of the resin for Cu(II) and Pb(II) evaluated from Langmuir models were 389.9 and 403.1 mg/g, respectively. Desorption studies revealed that Cu(II) and Pb(II) can be easily removed by treating metal ion adsorbed resins with 0.1 M H2SO4 or 0.1 M HCl. The adsorption-desorption process was a reversible process, which indicates that the polyamides are promising adsorbents for heavy metal removal from aqueous medium.

Toxidermie bulleuse sévère avec nécroépidermolyse en dialyse péritonéale : rôle de l’icodextrine ?

A simple, novel anion receptor based on 4-hydroxy-3-(N-phenyl-thiourea-N′-nitrilo-methylidynyl)-azobenzene with hybrid –OH and thiourea binding sites was synthesized and characterized. Anion binding character was determined using visual inspection, UV–vis, fluorescence and 1H NMR analyses. The addition of F−, AcO− and H2PO4− resulted in a marked red shift of the charge-transfer absorbance band (Δλ = 140 nm, from 340 nm to 480 nm) accompanied by a color change from light yellow to orange.

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

Two mesitylene based neutral receptors 1 and 2 bearing two thiourea binding sites were constructed as fluorescent probes for sensing dicarboxylates. Their binding affinities toward dicarboxylates, aspartate and glutamate have been investigated in acetonitrile solution by fluorescence titration experiments. Both fluorescent sensors exhibited some ability to discriminate the antipodal forms of aspartate and glutamate.

An excellent fluoride sorption behavior of modified amberlite resin

The article describes a convenient method for the modification of Amberlite XAD-4™ resin by introducing thio-urea binding sites onto the aromatic rings. The modified (ATU) resin has been employed for the quantitative sorption of fluoride ions in batch as well as column experiments. The parameters (i.e. pH, contact time, etc.) were optimized and desorption of fluoride ions was fulfilled by using 0.01 M HCl solution. The equation isotherms such as Langmuir, Freundlich, Dubinin–Radushkevich (D–R) and Temkin were also successfully applied to model the experimental data. The sorption capacity of the ATU resin was found as 3.286 mmol g −1. From the D–R isotherm parameters, it has been calculated that the uptake of fluoride ion by ATU resin occurs through ion exchange sorption mechanism. The study will contribute toward the remediation of fluoride polluted areas as well as in the various fields of materials science.

Tryptophan receptors containing acridine-based thiourea

Four derivatives of acridine and acridinium compounds (L1, L2, L1H and L2H) comprised thiourea-binding sites were synthesised. The binding abilities of receptors L1, L2, L1H and L2H towards amino acids (l-Trp, l-Phe, l-Leu, l-Ala and l-Gly) were studied by 1H NMR spectroscopy, UV–vis and fluorescence spectrophotometry. Hydrogen bonding interactions between thiourea-binding site of the ligand and the carboxylate groups in zwitterionic amino acids were found to be the main interactions driving complexation to take place. The stoichiometry of 1:1 ligand to amino acid was observed in all cases. Neutral ligands L1 and L2 showed weak binding towards all studied amino acids. The cyclic ligand L1 showed better binding ability towards tryptophan (Trp) than the acyclic ligand L2 did (K for Trp is 307 and 266 M− 1 for L1 and L2, respectively). Interestingly, binding abilities of the protonated ligands, L1H and L2H, towards studied amino acids, especially Trp (K for Trp is 3157 and 2873 M− 1 for L1H and L2H, respectively), were increased due to R–COO− …H…N+–acridinium interactions. Calculated structures of L1H·Trp and L2H·Trp showed that the polyglycol moiety in L1H provided a hydrophobic cavity for binding Trp resulting in a stronger binding affinity of L1H over L2H.

An efficient thiourea-based colorimetric chemosensor for naked-eye recognition of fluoride and acetate anions: UV–vis and 1HNMR 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.

Fluorescent sensing of anions based on excited state intramolecular proton transfer in N-(3-hydroxy-2-naphthamido)-N′-phenylthiourea

A neutral N-amidothiourea-based excited state intramolecular proton transfer (ESIPT) anion receptor bearing an o-hydroxynaphthamide fluorophore and a thiourea binding site, N-(3-hydroxy-2-naphthamide)-N′-phenylthiourea (1a), was designed and synthesized. Fluorescence and absorption response of 1a toward anions were assessed in acetonitrile. IR and NMR experiments indicated that the “OH⋯O=C” intramolecular hydrogen bond (IHB) in 1a was weak so that it only exhibited the short-wavelength normal emission other than ESIPT fluorescence. Due to the high anion binding affinity of the N-amidothiourea binding site and the formation of a hydrogen binding network in the 1a-anion complex, 1a underwent structural change upon anion binding that strengthens the “OH⋯O=C” IHB, leading to the ESIPT and the observation of the long-wavelength ESIPT emission whereas the normal fluorescence is quenched. On the basis of NMR and fluorescence titrations and control experiments with model compounds, a sensing mechanism of the anion-binding-induced ESIPT was proposed.

A novel chromo- and fluorogenic dual responding H 2PO 4− receptor based on an azo derivative

A simple, novel anion receptor based on 4-hydroxy-3-( N-phenyl-thiourea- N′-nitrilo-methylidynyl)-azobenzene with hybrid –OH and thiourea binding sites was synthesized and characterized. Anion binding character was determined using visual inspection, UV–vis, fluorescence and 1H NMR analyses. The addition of F −, AcO − and H 2PO 4 − resulted in a marked red shift of the charge-transfer absorbance band (Δ λ = 140 nm, from 340 nm to 480 nm) accompanied by a color change from light yellow to orange.

A Simple Colorimetric and Fluorescent Anion Sensor Based on 4-Amino-1,8-naphthalimide: Synthesis and its Recognition Properties

A neutral 4-amino-1,8-naphthalimide-based anion receptor 1 containing a thiourea binding site was synthesized by simple steps. Its recognition capabilities for various anions were investigated by UV–vis, fluorescence and 1H NMR spectra, which showed that compound 1 could effectively and selectively recognize F− and AcO− over other anions (Cl− , Br− , I− , , , ). In particular, a moderate color change (from greenish yellow to bright yellow) and significant fluorescence quenching were synchronously observed upon addition of F− or AcO− . Nonlinear curve fitting and Job plot method established the formation of 1:1 hydrogen-bonding complex between compound 1 and the bound anions.

N,N′-Bis(benzamido)thioureas as anion receptors

Abstract A series of N,N′-bis(substituted-benzamido)thioureas (3a–e, substituent = p-OEt, p-Me, H, p-Cl, and m-Cl) was designed as anion receptors based on their double hydrogen bonding interaction with anions. NMR and X-ray crystal structural analyses revealed that in these receptor molecules the benzamido moiety serving as a spectral signal reporter and the thiourea moiety as anion binding site were decoupled by the twisted N–N single bond and the two thioureido and amido NH protons experienced differed electronic environment. Yet the absorption spectra of 3a–e in acetonitrile in the presence of anions such as AcO−, F−, and H2PO4− underwent substantial changes by the appearance of a new band at ca. 325 nm, which is red-shifted by ca. 60 nm, and of a clear isosbestic point at 270 nm, suggesting that anion binding led to the communication between thiourea binding site and benzamido signal reporter via probably a conformational change around the N–N bond. The new band energies were found correlating linearly with the Hammett constant of the substituent with a slope of −0.361 eV, indicative of the charge-transfer character of the absorption band. The binding constants for AcO− and F− of 3a–e were obtained at not less than 107 M−1 orders of magnitude, which are much higher than those of the corresponding N,N′-bisarylthioureas. We suggest that anion binding to the thiourea moiety in 3a–e switches on charge transfer in the anion-receptor binding complex, which reinforces anion binding and therefore results in a dramatically enhanced binding affinity of the receptors. The symmetric N,N′-bis(benzamido)thioureas were therefore found better in anion binding and sensing than N-benzamidothioureas.

Fluoride-selective colorimetric sensor based on thiourea binding site and anthraquinone reporter

A structurally simple colorimetric sensor, N-4-nitrobenzene-N′-1′-anthraquinone-thiourea (1), for anions was synthesized and characterized by 1H NMR, ESI mass and IR methods. In acetonitrile, the addition of F− changed 1 solution from colorless to yellow. In the presence of other anions such as CH3CO2−, H2PO4−, HSO4− and Cl−, however, the absorption spectrum of 1 was slightly red shifted with no obvious color changes observed. The association constants of anionic complexes followed the order of F−≫CH3CO2−>H2PO4−>HSO4−>Cl−>Br−, which was different from the order of anion basicity. AM1 calculation results indicated that the most stable configuration of 1 existed in the Z–E-conformation with a six-membered ring via intramolecular hydrogen bond. This made thiourea moiety of 1 in an unfavorable conformation to bond with oxygen-anionic substrates such as CH3CO2− and H2PO4−, thus leading to a high selectivity and sensitivity for the detection of F−.

A Highly Selective Chromogenic and Fluorogenic Chemosensor for Fluoride Ion

Abstract The thiourea binding site anchored to fluorescent 4-amino-1,8-naphthalimide signaling subunit is a highly selective and sensitive chromogenic and fluorogenic reagent for fluoride anion sensing.

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-).

Efficient and simple colorimetric fluoride ion sensor based on receptors having urea and thiourea binding sites.

[structure: see text] Novel colorimetric receptors for selective fluoride ion sensing containing anthraquinone as chromogenic signaling subunit and urea (N,N' '-(9,10-dihydro-9,10-dioxo-1,2-anthracenediyl)bis[N'-phenyl])/thiourea (N,N' '-(9,10-dihydro-9,10-dihydro-9,10-dioxo-1,2-antrhacenediyl)bis[N-phenyl]) binding sites have been reported. These receptors have shown no affinity for other halide ions (Cl-, Br-, and I- ions). Well-defined color change in the visible region of the spectrum was observed upon addition of fluoride ion in DMSO/CH3CN solution of the receptors 1 and 2.