A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection,Naked‐Eye Recognition,and Elimination of Cyanide Ions

A new bimetallic Fe^II–Cu^II complex was synthesized, characterized, and applied as a selective and sensitive sensor for cyanide detection in water. This complex is the first multifunctional device that can simultaneously detect cyanide ions in real water samples, amplify the colorimetric signal upon detection for naked‐eye recognition at the parts‐per‐million (ppb) level, and convert the toxic cyanide ion into the much safer cyanate ion in situ. The mechanism of the bimetallic complex for high‐selectivity recognition and signaling toward cyanide ions was investigated through a series of binding kinetics of the complex with different analytes, including CN^?, SO₄^2?, HCO₃^?, HPO₄^2?, N₃^?, CH₃COO^?, NCS^?, NO₃^?, and Cl^? ions. In addition, the use of the indicator/catalyst displacement assay (ICDA) is demonstrated in the present system in which one metal center acts as a receptor and inhibitor and is bridged to another metal center that is responsible for signal transduction and catalysis, thus showing a versatile approach to the design of new multifunctional devices.     

A novel and synthetically facile coumarin-thiophene-derived Schiff base for selective fluorescent detection of cyanide anions in aqueous solution: Synthesis,anion interactions,theoretical study and DNA-binding properties

A colorimetric and fluorescent chemosensor (chemosensor 2) for the detection of cyanide anions in aqueous solution has been designed and synthesized in high yield. The sensing mechanism of the chemosensor was verified via UV–vis, fluorimetric, and NMR titrations, and was theoretically explained using DFT and TD-DFT calculations. The chemosensor could optically discriminate the presence of fluoride ions over other anions by a color change from yellow to red with an enhancement of pink fluorescence in DMSO. However, it showed strong green fluorescence when CN^? was added to a mixture of DMSO/water (6:4 v/v). Thus, the chemosensor can be employed in selective detecting of CN^? besides other interference anions (F^?, AcO^? and H₂PO₄^?) in aqueous solution. Moreover, 2 can be used to detect CN^? at a concentration as low as 0.32?μM, which is lower than the WHO guideline (2.7?μM) for cyanide. A low quantity of CN^? (1.08?μM) can be detected and quantified using the prepared chemosensor. Moreover, the UV–vis and fluorescence spectroscopy studies of the interactions between 2 and dublex DNA revealed intercalative binding of calf thymus DNA to the chemosensor.     

Naked Eye Detection of Carbonate,Hydroxide, and Cyanide Ions with 1,4′‐Diazaflavonium Bromides: A Simple Spectrophotometric Method for Cyanide Determination

Anion sensor properties of N‐alkyl‐substituted 1,4′‐diazaflavonium bromides in methanol–water were evaluated by UV–vis spectrometry. Pronounced changes were observed in the absorption spectra of all compounds for only OH^?, CO₃^2?, and CN^? among F^?, Cl^?, Br^?, I^?, OH^?, CO₃^2?, NO₃^?, PO₄^3?, CN^?, SO₄^2?, HSO₄^?, HCO₃^?, SCN^?, NO₂^?, and P₂O₇^2? ions. Two new absorption bands at 385 and 685 nm accompanying the distinct color change for OH^?, CO₃^2?, and CN^? ions were observed in case of all compounds. The color changes were from pink to blue for CO₃^2? and OH^? ions and from pink to purple for CN^? ion. Thanks to the distinct color change, the compounds can be used as selective colorimetric anion sensors. Linear changes of absorbance of N‐heptyl‐substituted compound at 385 nm as a function of the ion concentration were used to determine CN^? ion in water samples. Detection and quantification limits of the proposed method were 0.94 and 2.82 mg/L, respectively.     

Reaction‐Based Ratiometric Chemosensor for Instant Detection of Cyanide in Water with High Selectivity and Sensitivity

A highly selective chemosensor 1 based on an acylhydrazone group as binding site and naphthalene group as the fluorescence signal group were described, which could instantly detect CN^? in water with specific selectivity and high sensitivity. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the carbonyl group, which could be confirmed by ¹H NMR, ¹³C NMR, ESI‐MS and DFT calculations. The addition of CN^? to sensor 1 induced a remarkable color change from colorless to yellow and generated a blue fluorescence, these sense procedure could not interfered by other coexistent competitive anions (F^?, Cl^?, Br^?, I^?, AcO^?, H₂PO₄^?, HSO₄^?, ClO₄^?, SCN^?, S^2?, NO₃^? and SO₄^2?). The detection limits were 5.0×10^?7 M and 2.0×10^?9 M of CN^? using the visual fluorescent color changes and fluorescence spectra changes respectively, which is far lower than the WHO guideline of 1.9×10^?6 M . Test strips based on sensor 1 were fabricated, which could act as a convenient and efficient CN^? test kit to detect CN^? in pure water for “in‐the‐field” measurement.     

Novel calix[4]arene based metallo-supramolecular complex for recognition of cyanide ions in aqueous medium

A novel bis-naphthalimidocalix[4]arene-Cu(II) supramolecular complex has been observed to provide an efficient recognition system for CN^? ions in aqueous medium. The binding stoichiometry of bis-naphthalimidocalix[4]arene and copper ion has been found to be 1:1 while that for bis-naphthalimidocalix[4]arene-Cu(II) and cyanide ion it has been determined to be 1:2.     

Optical detection of cyanide by palladium(II)-dithiazolopyridine probe at the parts per billion level

Abstract

The ensemble of 2,6-bis(2-chlorophenyl)dithiazolo[4,5-b:5',4'-e]pyridine 1 with Pd²⁺ ions (1?Pd²⁺) was prepared for the detection of cyanide ions (CN^¯) in 50% aqueous methanol. Among the tested metal ions, only Pd²⁺ sensitively induced the red shift of the absorption bands and the complete decrease of fluorescence emission. The detection limit toward Pd²⁺ was 2?ppb. The ensemble 1?Pd²⁺ selectively and rapidly detected a low concentration of cyanide ions by a colorimetric change (40?ppb) as well as a “turn-on” fluorescent response (5?ppb). Job’s plot revealed the complex formation with 1:1 stoichiometry. The binding and replacement mode of 1?Pd²⁺ and CN^¯ were also confirmed by ¹H NMR titrations and IR analysis. In general, a fast and selective recognition of CN^¯ is reported.     

Naked-eye detection of cyanide ions in aqueous media based on an azo-azomethine chemosensor

The optical and colorimetric properties of a new chemosensor 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino)methyl)phenol (L) for cyanide ions were investigated by the naked-eye detection and UV–vis spectroscopy. This receptor reveals visual changes toward CN⁻ anions in aqueous media. No significant color changes were observed upon the addition of any other anions. The cyanide recognition properties of the receptor through proton-transfer were monitored by UV–vis titration and ¹H NMR spectroscopy. The binding constant (K_a) and stoichiometry of the formed host–guest complex were calculated by the Benesi–Hildebrand (B–H) plot and Job's plot method, respectively. The detection limit of the probe towards CN⁻ was 1.03 × 10⁻⁶ mol L⁻¹, which is lower than the maximum value of cyanide (1.9 × 10⁻⁶ mol L⁻¹) permitted by the World Health Organization in drinking water. Thus, this chemosensor was sensitive enough to detect cyanide in aqueous solutions. ¹H NMR experiments were conducted to investigate the nature of interaction between the receptor and CN⁻ anions. Notably, the designed sensor can be applied for the rapid detection of cyanide anions in the basic pH range and also under physiological conditions, for practical purposes for a long duration. The sensing behavior of the receptor was further emphasized by computational studies. Quantum-chemical calculations and molecular studies via Density Functional Theory (DFT) were carried out to supplement the experimental results.     

A Reversible Dual Mode Chemodosimeter for the Detection of Cyanide Ions in Natural Sources

Herein, we report the synthesis of two indolium probes 1 and 2 based on anthracene and pyrene derivatives and their interactions with various anions. Of these probes, the pyrene conjugate 2 acts as a dual colorimetric and fluorescent chemodosimeter for the selective and sensitive detection of cyanide ions. The detection limit of probe 2 for CN^? ions was found to be 10 ppb (30 nM ). The nature of interaction has been thoroughly studied through various techniques such as ¹H NMR and IR spectroscopy, HRMS, and isothermal calorimetric (ITC) studies. These studies confirm that probe 2 forms a 1,2‐adduct in the presence of CN^? ions. Kinetic studies using probe 2 showed the completion of the reaction within 15 s with a rate constant of k′=0.522±0.063 s^?1_. This probe can be coated on a solid surface (dipstick) and a polymer matrix for the on‐site analysis and quantification of endogenous cyanide ions in natural sources such as Indian almonds.     

A Novel Dielectric-Barrier-Discharge Loop Reactor for Cyanide Water Treatment

A novel dielectric-barrier-discharge (DBD) loop reactor was designed for the efficient degradation of cyanide anion (CN^?) in water. The circulation of cyanide water as a falling film through plasma gas discharge zone enhanced gas–liquid mass and energy transfer and induced formation of H₂O₂ which was associated with the efficient destruction of CN^?. It was observed that among different discharge gases, the CN^? degradation rate decreased in the order of Ar > air > H₂/air mixture. Depending on discharge voltage, the treatment time for complete removal of 100 ppm CN^? in this DBD loop reactor is in the range 120–300 min. The dose of Cu²⁺ catalyst in combination with in situ production of H₂O₂ enhanced the destruction of CN^? apparently in this DBD loop reactor. The treatment time for complete degradation of 100 ppm CN^? decreased from 180 min with Ar DBD discharge alone to 40 min with 40 mg/L dose of Cu²⁺ ion in water, making it an efficient means to degrade cyanide water.     

A highly selective and sensitive dual-channel chemosensor for cyanide based on sulfahydrazone derivative

A colorimetric and fluorescent cyanide probe bearing naphthol and sulfahydrazone groups has been designed and synthesized. This structurally simple probe displays a rapid response and high selectivity for cyanide in DMSO/EtOH (v/v = 2:8) solution. The addition of CN^? to the sensor p-toluenesulfonyl-2-hydroxy-1-naphthylhydrazone (L3) induced a remarkable color change from pale-yellow to yellow, and green fluorescence changed to yellow. The ¹H NMR titration and DFT calculations suggested that the selective sensing process is based on a nucleophilic addition reaction of cyanide to imine. Test strips based on sensor L3 were fabricated, which could act as a convenient and efficient test kit to detect CN^? for “in-the-field” measurements.     

A simple and efficient anionic chromogenic chemosensor based on 2,4-dinitrodiphenylamine in dimethyl sulfoxide and in dimethyl sulfoxide–water mixtures

Solutions of 2,4-dinitrodiphenylamine (1) in dimethylsulfoxide (DMSO) are colorless but upon deprotonation they become red. Addition of various anionic species (HSO₄^?, H₂PO₄^?, NO₃^?, CN^?, CH₃COO^?, F^?, Cl^?, Br^?, and I^?) to solutions of 1 revealed that only CN^?, F^?, CH₃COO^?, and H₂PO₄^? led to the appearance of the red color in solution. The presence of increasing amounts of water in solutions containing 1 made it progressively selective toward CN^? and the system with the addition of 4.3% (v/v) of water was highly selective for CN^? among all anions studied. The experimental data collected indicated that proton transfer from 1 to the anion occurs, and a model was used to explain the experimental results, which considers two 1:anion stoichiometries, 1:1 and 1:2. For the latter, the data suggest that the anion forms firstly a hydrogen-bonded complex with a second anion equivalent necessary for the abstraction of the proton, with the formation of a [HA₂]^? complex. The study performed here demonstrates the important role of the environment of the anion and 1 for the efficiency of the chromogenic chemosensor. Besides the different affinities of each anion for water, the solvation of both the anion and 1 is responsible for reducing the interaction between these species. In small amounts, water or hydrogen-bonded DMSO–water complexes are able to stabilize the conjugated base of 1 through hydrogen bonding, making 1 more acidic, which explains the change from 1:1 and 1:2 toward 1:1 1:anion stoichiometry upon addition of water. In addition, water is able to solvate the anion and also 1, which hinders the formation of 1:1 hydrogen-bonded 1:anion complexes prior to the abstraction of the proton.     

A Post‐Synthetically Modified MOF for Selective and Sensitive Aqueous‐Phase Detection of Highly Toxic Cyanide Ions

Selective and sensitive detection of toxic cyanide (CN^?) by a post‐synthetically altered metal–organic framework (MOF) has been achieved. A post‐synthetic modification was employed in the MOF to incorporate the specific recognition site with the CN^? ion over all other anions, such as Cl^?, Br^?, and SCN^?. The aqueous‐phase sensing and very low detection limit, the essential prerequisites for an effective sensory material, have been fulfilled by the MOF. Moreover, the present detection level meets the standard set by the World Health Organization (WHO) for the permissible limit of cyanide concentration in drinking water. The utilization of MOF‐based materials as the fluorometric probes for selective and sensitive detection of CN^? ions has not been explored till now.     

A simple Schiff base as ‘naked eye’ and fluorescent ‘on–off’ sensor for detecting cyanide in mixed aqueous solution

A simple Schiff base sensor (L₁) derived from N-(1-naphthyl) ethylenediamine dihydrochloride was designed and synthesised by simple chemistry procedures. The sensor exhibited a visible colour change observed by both colorimetric and fluorimetric responses for cyanide ion in aqueous solution. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the imine group of the sensor with a 1?:?1 binding stoichiometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN^? test kits and the sensor L₁ is a good way to detect hydrogen cyanide in aqueous extracts of sprouting potatoes.     

Catalytic Reduction of CN−, CO,and CO2 by Nitrogenase Cofactors in Lanthanide‐Driven Reactions

Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN^?), carbon monoxide (CO), and carbon dioxide (CO₂) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI₂) and 2,6‐lutidinium triflate (Lut‐H) are employed as a reductant and a proton source, respectively. Driven by SmI₂, the cofactors catalytically reduce CN^? or CO to C₁–C₄ hydrocarbons, and CO₂ to CO and C₁–C₃ hydrocarbons. The C? C coupling from CO₂ indicates a unique Fischer–Tropsch‐like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN^?, CO, and CO₂ by isolated cofactors suggests the possibility to develop nitrogenase‐based electrocatalysts for the production of hydrocarbons from these carbon‐containing compounds.     

Bithiophene triarylborane dyad: An efficient material for the selective detection of CN− and F− ions

A new fluorescent chemosensor based on bithiophene coupled dimesitylborane (BMB-1) was synthesized and characterized. BMB-1 was used for colorimetric and turn-on fluorescent sensing of cyanide (CN⁻) and fluoride (F⁻) ions, in the presence of other competitive anions in an aqueous (CH₃CN–H₂O) medium. BMB-1 showed a hypsochromic shift (blue shift) with addition of CN⁻ and F⁻ ions in absorption studies. The lower detection level of CN⁻ and F⁻ ions is 1.37 × 10⁻⁹ and 1.75 × 10⁻⁹ M, respectively. The BMB-1 binding mechanism is based on the nucleophilic addition of CN⁻ and F⁻ ions in the internal charge transfer transition of bithio moiety to the boranylmesitylene unit, and the color changes were observed under UV light. This result is further confirmed by Fourier transform infrared spectroscopy, mass spectrometry and density functional theory calculations. Also, the BMB-1 probe is found to be a good adsorbent for the removal of F⁻ ions in real water samples using the adsorption technique.     

Aroyleneimidazophenazine: A Sensitive Probe for Detecting CN− Anion and its Solvatochromism Effect

A novel electron‐deficient heteroacene 15H‐pyrazino[2″,3″:3′,4′]pyrrolo[1′,2′:1,2]imidazo[4,5‐b]phenazin‐15‐one ( 1 ) has been successfully synthesized and characterized. Compound 1 can selectively recognize CN^? and F^? over other 10 anions including BF₄^?, PF₆^?, Cl^?, SO₄^2?, NO₃^?, I^?, H₂PO₄^?, ClO₄^?, Ac^?, and Br^? in CHCl₃/DMF mixed solvents with dual responses, including absorption signals and fluorescent “turn‐off” effects. CN^? and F^? can be distinguished by the completely quenched fluorescence (for CN^?) and partially reduced fluorescence (for F^?). Especially, compound 1 exhibits higher sensitivity to CN^? than F^? with the response concentration as low as 5.0 × 10^?6 mol/L. Moreover, compound 1 shows very interesting solvatochromism effect, and the CHCl₃ solution of compound 1 is sensitive to triethylamine, and its emission could change from green to red upon the addition of triethylamine, which is attributed to the n–π intermolecular charge‐transfer interaction.     

Pyridinium‐Fused Pyridinone: A Novel “Turn‐on” Fluorescent Chemodosimeter for Cyanide

A new chemodosimeter based on pyridinium‐fused pyridinone iodide ( PI ) has been obtained through a “clean reaction” method. This compound can detect CN^? in aqueous solution with a high selectivity and rapid response. The detection of CN^? occurs through the nucleophilic attack of CN^? on the C?N bond, which induces the destruction of the π‐conjugation on the pyridinium ring. Support of this detection mechanism was obtained by ¹H NMR titration, HR‐MS, and DFT calculations. Upon the addition of 10 equivalents CN^? to a solution of PI in THF/H₂O (1:1, v/v), a 57‐fold enhancement in fluorescence intensity was observed at the maximum emission wavelength of 457 nm. Meanwhile, the maximum absorption wavelength was also blue‐shifted from 447 nm to 355 nm. Other common anions such as BF₄^?, PF₆^?, F^?, Cl^?, Br^?, I^?, H₂PO₄^?, ClO₄^?, CH₃COO^?, NO₂^?, N₃^?, and SCN^? had little effect on the detection of CN^?. The response time of PI for CN^? was less than 5 seconds. The detection limit was calculated to be 5.4×10^?8 M , which is lower than the maximum permission concentration in drinking water (1.9 μM ) set by the World Health Organization (WHO).     

Crystal structures and DNA-binding properties of PrIII complexes derived from 8-hydroxyquinoline-2-carboxaldehyde and three aroylhydrazines

Pr^III and three synthesized ligands, 8-hydroxyquinoline-2-carboxaldehyde-(benzoyl)hydrazone, 8-hydroxyquinoline-2-carboxaldehyde-(2′-hydroxybenzoyl)hydrazone, and 8-hydroxyquinoline-2-carboxaldehyde-(isonicotinyl)hydrazone, respectively, can form binuclear Pr^III complexes with 1?:?1 metal-to-ligand stoichiometry and nine-coordination at Pr^III indicated by X-ray crystal structural analyses. Ligands are dibasic tetradentate, binding to Pr^III through the phenolate oxygen, nitrogen of quinolinato unit, the C=N of methylene, and ^–O–C=N– enolized and deprotonated from O=C–NH– of the aroylhydrazone side chain. One DMF binds orthogonally to the ligand plane from one side to the metal ion, while another DMF and a bidentate nitrate simultaneously bind from the other. Dimerization of the monomeric unit occurs through the phenolate oxygen leading to a central planar four-membered (PrO)₂ ring. The crystal structures are similar to each other and to other nine-coordinate lanthanide complexes with geometry of distorted edge-sharing mono-capped square-antiprism of [LnL(NO₃)(DMF)₂]₂ (Ln = La^III, Nd^III, Sm^III, Eu^III, Tb^III, Dy^III, Ho^III, and Er^III) except for Yb^III with eight-coordinate Yb^III center with distorted edge-sharing dodecahedron of [YbL(NO₃)(DMF)]₂, derived from 8-hydroxyquinoline-2-carboxaldehyde and aroylhydrazines. The ligands and Pr^III complexes can bind to calf thymus DNA through intercalation with binding constants at 10⁵ M^?1 and probably be used as potential antitumor drugs.     

Some analytical applications of aromatic sulfonyl haloamines: Determination of thiocyanate and cyanide ions in metal complexes and salts and thiosemicarbazide in metal complexes with bromamine-T

A simple, rapid, and accurate method for the determination of thiocyanate and cyanide ions in metal complexes and salts, and thiosemicarbazide (TSC) in Zn, Cd, Hg, Ni, Pt, and Pd metal complexes with excess of bromamine-T has been developed. The oxidation involves eight- and two-electron changes, respectively, with NCS^? and CN^? ions and a 12-electron stoichiometry per TSC molecule, in 0.1–0.2 N NaOH medium. The proposed method could be employed for computing the number of thiocyanate, cyanide, and TSC ligands in the respective complexes. The aromatic sulfonyl haloamine, bromamine-T, has been prepared and characterized by uv, ir, and FT NMR ¹H and ¹³C spectral data and its mass spectrum.     

Study by fluorescence of calix[4]arenes bearing heterocycles with anions: highly selective detection of iodide

The present work describes a study of complexation efficiency of calix[4]arenes bearing benzoimidazolyl, benzothiazolyl, and benzoxazolyl heterocycles (5–7) towards several anions. The binding ability of calixarene derivatives 5–7 towards selected anions of different molecular geometries such as: F^?, HSO₄ ^?, I^?, N₃ ^?, NO₃ ^?, NO₂ ^?, SCN^?, ClO₄ ^?, Br^?, CN^?, Cl^?, CH₃COO^? CF₃SO₃ ^? in methanol, has been investigated by fluorescence spectroscopic techniques, all anions were used as tetrabutylammonium salts to avoid possible complexation of cationic species by the derivative calix[4]arenes. Fluorescent chemosensor ability of these three calixarene derivatives was highly selective for iodide in contrast with other anions studied. The best chemosensor found, corresponds to compound 7, with an association constant of 2.01 × 10⁴ mol^?1 L and a detection limits of 0.22 ppm for iodide.