Addition Of Cyanide Ion Research Articles

Miniaturized dual-wavelength β-correction spectrophotometric probe for sensitive detection of cyanide in water via formation of cyano dithizone adduct

Cyanide toxicity in water significantly threatens public health and the environment. To address this, a miniaturized simple, low-cost, selective and sensitive direct dual wave β-correction spectrophotometric probe has been established for cyanide detection in water. The dual-wavelength β-correction spectrophotometry enhances the selectivity and sensitivity of the probe in the presence of interfering species. The assay relies a highly selective nucleophilic addition of cyanide ions to dithizone (H2Dz) as chromogenic reagent in aqueous media of pH 6.8–7.2, forming a red-colored cyano H2Dz adduct. The electronic spectrum of the formed adduct displays a sharp absorption peak at λmax = 480 nm, enabling precise colorimetric detection. The molar absorptivity and Sandell’s sensitivity index for the cyano H2Dz adduct with and without β-correction spectrophotometry were 5.62 × 103, and 1.79 × 103 L mol−1 cm−1, and 0.002 and 0.0033 µg cm−2, respectively. Beer’s law and Ringbom’s plots are valid in the range 0.01–5.0 and 0.06–2.0 µg mL−1 CN– concentration, respectively. The limits of detection (LOD) and quantification (LOQ) improved from 1.03 × 10−1 and 3.13 × 10−1 μg/mL using ordinary spectrophotometry to 2.8 × 10−2 and 8.7 × 10−2 μgmL−1 employing β-correction spectrophotometry. The probe offers rapid response, good anti-interference ability, reproducibility, and cost-effectiveness. The probe was successfully applied for detection of trace levels of cyanide ions in water with good repeatability. It has been also validated in water samples with good recoveries (99.2 ± 5.02 %). The experimental Student t test (texp = 1.2–1.5) was lower than the critical (texp = 2.78) at 95 % probability (n = 5). The stoichiometry and mechanism of formation of the cyano adduct were assigned and addressed.

A highly sensitive colorimetric and fluorometric sensor for the detection of cyanide

Certain anions play a vital role in metabolic reactions in our body, but the cyanide ion is highly toxic and poisonous to humans, animals, and the environment even at extremely low concentrations. To detect CN−ions, a highly sensitive electron donor-π-acceptor molecular system (IC) was designed based on the carbazole electron donor and 1,3-indanedione electron acceptor. The IC molecular probe was synthesized through simple organic transformations with good yields and characterized by all spectroscopic methods, including single-crystal X-ray diffraction. The IC probe molecule absorbs in the UV–visible region (200–550 nm), and fluorescence emission encompasses 400–750 nm with LE and CT emission bands. A systematic study suggests that the addition of cyanide ions caused both longer wavelength absorption bands and CT fluorescence emission intensity to decrease. Cyanide ion detection can be visualized with the naked eye, where the yellow color of the IC probe solution changes to colorless upon adding cyanide ion solution. Both UV–visible and fluorescence emission spectral changes with the addition of cyanide ions are attributed to the nucleophilic addition of cyanide at the vinylic carbon, which is confirmed by the 1H NMR, HRMS and fluorescence lifetime studies. The cyanide ion detection limit of the IC has been estimated to be 0.43 µM, far below the WHO permissible limit for cyanide ion concentration in potable water, thus broadening the utility of the IC probe in detecting cyanide in Tapioca. A prototype TLC testing strip has been fabricated for the qualitative determination of cyanide in THF/water medium.

Tailoring bisindolyl methane derivatives for dual applications: Substituent-directed probing of cyanide ions and anti-tubercular activity

A pair of bisindolyl methane (BIM) compounds (1 and 2) were designed and their colorimetric response towards cyanide (CN−) ions were investigated in detail. In aqueous medium, the compound with single nitro-substituent (1) showed blue-shifted absorption maxima upon addition of cyanide ion, resulting in change in solution color from pink to yellow. On the contrary, the compound with three nitro functional groups (2), exhibited hypochromic shift along with initial, blue-shifted absorption maxima (color changed from pink to yellow to colourless). The mechanistic investigation indicated that the former observation could be attributed by cyanide-mediated hydrogen bonding interaction (or deprotonation), while the latter might be caused due to the Michael addition reaction. Interestingly, at alkaline pH, chemodosimetric interaction was observed with both the probe molecules. However, the rate of interaction was much faster for compound 2 than that observed for 1. A change in the mode of binding of a specific analyte, merely by changing the number of un-reactive substituents, is not much known in the literature. However, it will be extremely beneficial for future engineering of more efficient sensory systems. Furthermore, a library of BIM compounds with various number of nitro groups at different positions (total twelve) were synthesized for evaluation of anti-tubercular activity. Fortunately, some of the compounds were found to be as equally effective as the commercially available anti-tuberculosis drug, ethambutol (MIC: 1.56 µg/mL), whereas the compound 2 displayed a better anti-tubercular response (MIC: 0.78 µg/mL). This observation was further rationalized by docking studies with M. tuberculosis DprE1 in complex with the non-covalent inhibitor QN118.

Rapid, Sensitive, and Selective "ON-OFF" Detection of Fe3+ Ions Using Novel Acetalophanes and Their Applications in Real Samples.

Three novel acetalophanes 1a-c have been designed, synthesized and characterized. The receptors 1b-c, featuring bulky anthracene groups, displayed significant selectivity for Fe3+ ions, resulting in a turn-off fluorescence mode in a DMF-buffer solution. Conversely, the non-steric probe 1a could serve as a versatile sensor for the simultaneous detection of Fe3+ and Cu2+ ions in MeOH-buffer solution. The sensing mechanism for the capability of 1a was demonstrated to be different, as evidenced by the addition of cyanide ions. The probes with Fe3+ exhibited a sensing mechanism that resulted in the deprotection of acetals to the corresponding starting materials, as confirmed by 1H NMR, IR spectra and TLC analysis. The attractive features of these practical and efficient sensors are selectivity, sensitivity (limit of detection = 0.15µM by 1a, 0.16µM by 1b and 0.14µM by 1c), rapid response (less than 5 s). The on-site monitoring of various real samples, including well water, apricot, and green tea, proved to be successful for the quantitative and cost-effective detection of Fe3+. The method demonstrated good precision, even in the presence of other interfering materials.

A distinctive and proficient fluorescent switch for ratiometric recognition of the menacing cyanide ion: biological studies on MDA-MB-231 cells.

A new fluorescent ratiometric switch (BOHB) was developed for swift and selective detection of cyanide ions in aqueous media without any interference from other competitive anions. Upon gradual addition of cyanide ions into the probe solution, a prominent fluorescence color change from yellow to cyan was observed under a UV chamber. The fluorescence changes thus observed were ratiometric, and the detection limit of this new probe was found to be (22.1 ± 0.89) μM, suggesting that the efficiency of BOHB for the detection of cyanide ions is brilliant even at a minute level. The blue shift in fluorescence intensity upon the addition of cyanide ions was attributed to the deprotonation mechanism of acidic protons present in BOHB. This phenomenon was further explored using 1H-NMR study, which supported the mechanism. Further, stability study was performed over a period of 5 days to prominently establish the stability of BOHB. The probe is also highly capable of recognizing CN- within a very short time-span (almost 15 seconds), thereby making it a brilliant fluorescent switch for the swift recognition of CN-. Furthermore, BOHB was employed for real water sample analysis to display its practical application. Besides, the easy-to-prepare dipstick experiment provides a simple, reusable and recyclable protocol for the suitable qualitative identification of CN-. Lastly, triple negative breast adenocarcinoma (MDA-MB-231) cells were made susceptible to CN- sensing in a biological system, thereby making BOHB a biomarker tool.

A reaction based carbazole-indolium conjugate probe for the selective detection of environmentally toxic ions.

A nucleophilic addition based chemodosimeter was designed and synthesized with a carbazole donor and an indole acceptor. The addition of a cyanide ion to an electron-deficient indole moiety disrupts the acceptor-donor relationship, resulting in noticeable color shifts and spectrum differences in both the absorption and emission profiles. The design has a D-π-A molecular arrangement. Selectivity was investigated in 90% aqueous DMSO solution of probe CI with various anions such as SCN-, PF6-, NO3-, N3-, I-, HSO4-, CN-, H2PO4-, F-, HS-, ClO4-, Cl-, Br-, and AcO-. An intermolecular charge transfer (ICT) band at 506 nm in the UV-visible spectra vanished and the intensity of emission was quenched at 624 nm upon the addition of CN- ions. These outcomes demonstrate the effective nucleophilic addition of cyanide ions to the electron-deficient indole moiety of the probe, resulting in the formation of a new adduct in which the ICT transition is interrupted when π conjugation is blocked. The Job plot, 1H NMR spectroscopy, and HRMS analysis confirmed the formation of a new product. An outstanding response was shown by paper test strips made using probe molecules for the easy detection of cyanide ions in aqueous solutions. Besides, the probe selectively senses cyanide ions in different water samples.

A unique triple–channel fluorescent probe for discriminative detection of cyanide, hydrazine, and hypochlorite

Herein, the first triple-channel fluorescent probe, TTB, excited at the same wavelength (λex = 360 nm) in the same sensing medium for the detection and discrimination of cyanide, hydrazine, and hypochlorite, is disclosed. While a fluorescent white color appeared (λem = 470 nm) with the addition of cyanide ion into the probe solution, upon addition of hydrazine and hypochlorite, green (λem = 503 nm) and orange (λem = 585 nm) fluorescent colors, respectively, were observed. A naked-eye detection for the three ions was documented. With the appearance of orange color, a mega Stokes shift of 175 nm was observed. The probe exhibited excellent selectivity and lower detection limits of 0.24 μM, 4.1 nM and 0.27 μM, and dynamic ranges of 0.0–2.0 μM, 0.0–0.05 μM and 0.0–2.0 μM for cyanide, hydrazine and hypochlorite, respectively. The sensing mechanism was investigated through computational studies before and after the addition of cyanide, hypochlorite, and hydrazine, applying density functional theory (DFT), along with the calculation of optical properties by time-dependent DFT (TD-DFT) method. The results were found to be in good agreement with the experimental values. Remarkably, the probe, TTB, successfully detected cyanide, hydrazine, and hypochlorite in complex water samples. Moreover, the detection of cyanide was successfully performed in apricot kernels, as well as hypochlorite in fruits and vegetables.

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion.

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. 1H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN- system may be reversed upon the addition of Ag+/ Cu2+ ions up to 5 consecutive cycles. Moreover, DPOC coated "test strips" were prepared for visual detection of cyanide ions.

Nitrogen-rich silicon quantum dots: facile synthesis and application as a fluorescent 'on-off-on' probe for sensitive detection of Hg2+ and cyanide ions.

The sensitive and reliable detection of Hg2+ and CN- as harsh environmental contaminants are of great importance. In view of this, a novel 'on-off-on' fluorescent probe based on nitrogen-rich silicon quantum dots (NR-SiQDs) has been designed for sensitive detection of Hg2+ and CN- ions in aqueous medium. NR-SiQDs were synthesized using a facile, one-step, and environment friendly procedure in the presence of 3-aminopropyl trimethoxysilane (APTMS) and ascorbic acid (AA) as precursors, with l-asparagine as a nitrogen source for surface modification. The NR-SiQDs exhibited strong fluorescence emission at 450 nm with 42.34% quantum yield, satisfactory salt tolerance, and superior photostability and pH stability. The fluorescence emission was effectively quenched using Hg2+ (turn-off) due to the formation of a nonfluorescent stable NR-SiQDs/Hg2+ complex, whereas after the addition of cyanide ions (CN- ), Hg2+ ions could be leached from the surface of the NR-SiQDs and the fluorescence emission intensity of the quenched NR-SiQDs fully recovered (turn-on) due to the formation of highly stable [Hg(CN)4 ]2- species. After optimizing the response conditions, the obtained limits of detection were found to be 53 nM and 0.46 μM for Hg2+ and CN- , respectively. Finally, the NR-SiQD-based fluorescence probe was utilized to detect Hg2+ and CN- ions in water samples and satisfactory results were obtained, suggesting its potential application for environmental monitoring.

Colorimetric detection of cyanide ions using Schiff base derived chemosensor

Cyanide ion sensing is essential owing to its extreme toxicity and poisoning in environment. Schiff base derived chemosensor 3 ((E)-1-(1-(2-hydroxy-5-methylphenyl)ethylidene)-4-(4phenylthaizol-2-yl)semicarbazide), was synthesized by condensation reaction of 4-(4-phenylthiazole-2-yl)semicarbazide with 1-(2-hydroxy-5-methylphenyl)ethenone.for colorimetric detection of cyanide ions. Chemosensor 3 was characterized by NMR studies. The absorbtion studies were carried out in dimethyl formamide (DMF) solution and shows strong absorbtion bands in 280–350 nm region. Addition of cyanide ions into DMF solution of chemosensor 3 results in visually detectable color changes from colorless to yellow due to the formation of hydrogen bonded adduct. A good linearity in the range of 1.66 µM to 11.6 µM with limit of detection value (LOD) 0.5 µM was observed.

Cyanine-based Fluorescent Probe for Cyanide Ion Detection.

Cyanine-based probe-possessing indolium iodide and indole unit were synthesized in two-step with easy available raw material: a potential probe for the cyanide ion detection. The detecting ability of the probe was investigated and confirmed by a visual and instrumental approach. A noticeable color change from orange to colorless obtained only for cyanide ions and other added ions does not impart any changes visually and through UV and Fluorescence technique. To confirm the mechanism of sensing 1H-NMR recorded. From the result, the peak belonging toN-methyl displayed an upfield shift from 4.01 δ ppm to 2.74 δ ppm due to the disappearance of indolium iodide ion and the olefin protons peaks were shifted from 7.19 to 6.17 and 8.70 to 7.20 δ ppm confirms the nucleophilic addition of cyanide ion to the probe. Test kit from filter paper prepared for the real-time monitoring cyanide ion. The prepared strip is effective in detecting cyanide ion with a visual color change.

Development of simple imine based probe for selective fluorescent cyanide sensing with red-emission in solid and solution phases

In the present work, an easy to make imine based receptor (3,3′(((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(2-aminomaleonitrile)) (CNA) has been synthesized in good yield and characterized by spectral methods. CNA showed rapid, selective and sensitive naked-eye dual channel response (colorimetric and fluorogenic) towards cyanide ion. The receptor exhibited instantaneous colour change upon addition of cyanide ion based on deprotonation of phenolic –OH moiety in neat DMSO, 30% aq. DMSO and solid media. Interestingly, CNA showed red-emission (640 nm < λem < 677 nm) upon treatment with cyanide ion in all these media. Limit of detection of CNA for cyanide ion was determined to be 0.5 μM, which is much lower than the permissible limit of cyanide in drinking water as recommended by the World Health Organization. The fabricated cotton swabs and test strips demonstrated excellent selectivity towards cyanide ion in aqueous solution. Further, CNA is suitable for dual channel detection of cyanide ion in food materials. Furthermore, the observable colour change of the probe upon binding with cyanide ion has successfully been integrated with a smartphone Colour Picker app to estimate cyanide ions.

A simple imine as a dual-channel chemosensor for detection of CN− and HS− ions via different mechanisms in organic and aquo-organic media

An imine based easy to make receptor (R) has been synthesized and characterized, which senses CN− and HS− ions selectively and sensitively in neat DMSO and H2O:DMSO (60:40 v/v) media. Upon treatment with these ions, the receptor exhibited instantaneous colour change from yellow to colourless and a fluorescence enhancement and these optical changes are easily detected by direct visualization. Further, other competitive anions didn’t display any observable colour and fluorescence changes, indicating the receptor's high selectivity towards CN− and HS− ions. The nucleophilic addition of cyanide ion to the imine bond induces an increase in fluorescence, while HS− ion triggered cleavage of the imine bond, producing enhancement in fluorescence in both the media. The limits of detection for CN− and HS− ions were calculated to be 0.9 and 0.7 μM, respectively, which are lower than the permissible limit of these ions in drinking water set by the World Health Organization (WHO). The receptor has fruitfully been applied for the detection of these ions in live HeLa cells.

Triphenylamine-thiophene dyad as a Chemodosimeter for specific recognition of cyanide ions in aqueous solutions

Triphenyl amine-thiophene conjugated with benzothialzole derivative TP-1 have been synthesized and explored as new colorimetric and turn-on fluorescent Chemodosimeter for cyanide anions. The probe TP-1 showing a discrete visible color change from dark yellow to colorless and subsequently the fluorescence intensity gets increased after addition of the cyanide anions, it's very selective towards cyanide ions. The probe is showing the increase in fluorescence with cyanide ions in the linear range 1–100 μM. The limit of detection for cyanide ions by the probe TP-1 was found to be 4.24 × 10−8 M. The observed absorption, fluorescence changes was further supported by density functional theory calculations and the internal charge transfer mechanism is takes place while addition of cyanide ions. Further low cytotoxic behavior of TP-1 makes the probe feasible for live cell detection of cyanide ions.

5'-Hydroxymethyl fluorescein: A colorimetric chemosensor for naked-eye sensing of cyanide ion in a biological fluid.

A two-step synthetic method to prepare a highly sensitive and selective chemosensor 5'-hydroxymethyl fluorescein (5'-HMF) is described herein. This sensor was explored as a colorimetric sensor for naked-eye detection of cyanide ion in the biological fluid as well as in organic and aqueous media. The addition of cyanide ion to 5'-HMF resulted in a rapid change in color in aqueous medium from light green to dark fluorescent green, and in acetonitrile from light pink to purple. A significant bathochromic shift in the absorption spectra enables cyanide ion to be detected by naked eyes in water and acetonitrile without any interference of the competing anions such as, AcO-, F- and SCN- in aqueous solution. Using the 1HNMR titration experiments and Job's plot from absorbance spectroscopy, the interaction of CN- ion with 5'-HMF has been investigated and binding stoichiometry was found to be 1:2 (5'-HMF to CN-). The limit of detection (LOD) of the sensor for CN- was 3.68μM in water with a linearity (R2=0.9923) in the range of 0.50 to 30.0μM concentration assuming 1:2 (5'-HMF to CN-) binding stoichiometry. In addition, the sensor 5'-HMF sensed the CN- ion in human saliva with the LOD as 7.0μM in aq. medium.

Ruthenium-based phosphorescent probe for selective and naked-eye detection of cyanide in aqueous media

A simple molecular phosphorescent Ru(II) probe P1 has been synthesized by the reaction of 5-aldehyde-2,2′-bipyridine with ruthenium(II) chlorides under mild conditions. The probe upon interaction with different cation and anion showed high selectivity and sensitivity for cyanide ion (CN‒) through phosphorescence “turn-on” response in aqueous solution (60% water) with a detection limit of 0.75 μM. The significant phosphorescence enhancement (~ 30-fold) is attributed to the nucleophilic addition of cyanide ion to the aldehyde groups of the ruthenium complex in 3 : 1 stoichiometry, in which a naked-eye sensitive orange red color of solution changed to a yellow. The generation of cyanohydrin species through nucleophilic addition has been confirmed by 1H NMR, FT-IR and mass spectra. Based on the color change of the solution, a visual colorimetric strip was prepared, which also showed good detection performance on cyanide ion with quick response time. The prominent efficiency of the Ru(II) probe proved the potential possibility of application in biosystems relating with cyanide ion.

Synthesis, characterization and DFT studies of complexes bearing [Re(CO)3]+ core and reactivity towards cyanide ion

Mononuclear rhenium(I) complexes having fac-[Re(CO)3]+ core of general formula fac-[Re(CO)3(L)Cl] have been synthesized in excellent yield by reacting [Re(CO)5Cl] with L1 and L2in a ratio of 1:1 in toluene under inert atmosphere. Here L1 and L2 are N-((quinolin-2-yl)methylene)-9H-fluoren-2-amine and N-((anthracen-10-yl)methylene)quinolin-8-amine respectively. Spectroscopic measurements such as NMR, ESI-MS and IR spectroscopy were used to ensure the formations of desired complexes. Molecular structures of fac-[Re(CO)3(L1)Cl] and fac-[Re(CO)3(L2)Cl] were confirmed by single-crystal X-ray diffraction. The ligands are emissive whereas the metal complexes are weak emitter. A remarkable change in absorption as well as emission behavior was observed in complex 2 upon addition of cyanide ion. Interruption in intraligand charge transfer in complex 2 is the probable reason for the obvious change in spectral response of the same. 1H NMR titration was performed as the evidence of the previously stated fact. The ground and excited-state geometries, absorption properties of rhenium(I) complexes were examined by DFT and TDDFT methods. The natural transition orbital (NTO) and analysis reveal the nature of excitations.

Desing of optical chemosensors for detection of cyanide ions in water environments

Molecular interactions with various anions in the form of tetrabutylammonium salts in DMSO and DMSO-aqueous mixture were studied spectrophotometrically. It turned out that the solutions of 1-hydroxy-2-acylaminoanthraquinones in DMSO, originally yellow, became dark purple with the addition of cyanide, fluoride, phosphate, and acetate ions. The addition of other salts did not cause changes in the absorption spectra. When switching to aqueous DMSO, a contrasting color change in the solution was observed only with the addition of the cyanide ion. The stability constants of the complexes and the metrological characteristics of the processes were determined. On the basis of 1hydroxy-2-benzoylaminoanthraquinone, colorimetric test strips were made and tested for the detection of CN-ions in an aqueous medium.

Rational design and application of a fluorogenic chemodosimeter for selective detection of cyanide in an aqueous solution via excimer formation.

A new quinone-benzothiazole imine based chemodosimeter (R) was rationally designed, synthesized and characterized using NMR and mass spectral techniques. The receptor colorimetrically senses cyanide in aq. HEPES buffer: DMF (2:8 v/v) solution with an instantaneous colour change from yellow to bluish green. An enhancement of fluorescence intensity at 429 nm with excimer formation is also observed after addition of cyanide to the receptor, which is accompanied with a colour change from yellow to blue under UV lamp. Nucleophilic addition of cyanide to imine C-atom inhibits intra-molecular charge transfer (ICT) transition, which is responsible for the excimer formation. This chemical reaction is confirmed by 1H NMR titration. The receptor binds with two equivalents of cyanide with a binding constant of 5.55 × 104 M-1. The limit of detection (LOD) of cyanide by the receptor is found to be as low as 69 nM, which is much lower than the acceptable limit of cyanide in drinking water as set by the WHO (1.9 μM). Electrochemical studies support the termination of ICT transition upon addition of cyanide ion. Theoretical studies substantiate experimental findings and excimer formation. The receptor fluorometrically detects cyanide present in tap water and food materials such as cassava flour, almond and potato.

A novel dendritic polymer based turn- off fluorescence sensor for the selective detection of cyanide ion in aqueous medium

Porphyrin cored polyepichlorohydrin (POR-PECH) dendritic polymer was identified as an efficient turn-off fluorescence probe for selective determination of cyanide ion in aqueous medium. The dendritic polymer showed strong red fluorescence at 656 and 718 nm which was quenched in the presence of cyanide ion. POR-PECH showed high selectivity towards cyanide ion over other relevant anions including Cl−, Br−, F−, I−, NO2−, NO3−, CH3COO−, SO32−, CO32−, SCN−, HCO3−, HPO42−, H2PO4− etc. The proposed sensor is highly selective, sensitive which showed quick response towards cyanide ion. The limit of detection of proposed method was found to be 1.2 μM which was admirably lower than the maximum allowed cyanide content in drinking water (1.9 μM) as recommended by WHO. Back folding of self assembled porphyrin cored PECH dendritic chains by the addition of cyanide ion caused the quenching of fluorescence. The time resolved fluorescence life time, FE-SEM image and DFT studies supported the quenching mechanism.