Potentiometric measurements of hydrogen and cyanide ions in buffered media

A Carbazole Acrylonitrile Substituted Turn-On Fluorescence Chemosensors for Cyanide Ion and its Application to Real Sample Analysis

An efficient probe (E)-2-(benzo[d]thiazol-2-yl)-3-(9-ethyl-9 H-carbazol-3-yl)acrylonitrile (CZ-BTZ) for selective fluorescence "turn-on" response with cyanide (CN-) ion sensor was developed by simple Knoevenagel condensation of 9-ethyl-9 H carbazole-3-carbaldehyde with 2-(benzo[d]thiazol-2-yl) acetonitrile. The sensing ability of probe CZ-BTZ was tested with different inorganic anions through spectrophotometric and spectrofluorimetric methods. The UV-vis and fluorescence spectral studies show the formation of a new adduct between CZ-BTZ and CN- by appearing with a new absorbance band at 350 nm and "turn-on" fluorescence at 535 nm in CH3CN: H2O (8:2, v/v, pH 7.2). The absorbance and fluorescence study reveals the formation of 1:1 (CZ-BTZ: CN-) stoichiometry adducts with an estimated association constant of 2.04 × 105 M-1. The probe CZ-BTZ could detect CN- down to 4.19 nM without much interference, much lower than the WHO limit (1.9 µM) in drinking water. The sensing mechanism of CZ-BTZ with CN- ions was studied using FTIR, ESI mass analysis, and DFT calculation. Further, the probe was applied to analyse CN- ions' real-time food sample analysis.

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.

Nucleophilic Approach to Cyanide Sensing by Chemosensors

Cyanide anion has wide use in industrial areas; however, it has a high toxic effect on the environment as waste. Moreover, plant seeds contain cyanide that is often consumed by human beings. Therefore, many studies are carried out to determine cyanide. Especially, optical sensors showing colorimetric and fluorimetric changes have been of considerable interest due to their easy, cheap, and fast responses. This review discusses recent developments in the colorimetric and fluorimetric detection of cyanide by nucleophilic addition to different types of receptors via the chemodosimeter approach. The sensitivity and selectivity of the sensors have been reviewed for changes in absorption and fluorescence, naked-eye detection, real sample application, and detection limits when interacting with cyanide.

A CH-Controlled Colorimetric Probe Based on Anthracene Carboximide for Near-Infrared Cyanide Detection

A chemical sensor that can induce near-infrared red-shifted response represents a promising strategy for the design and development of anion probes. In this work, novel CH-controlled colorimetric probe 3 based on anthracene carboximide was developed for near-infrared detection of cyanide. Probe 3 consisted of CHCN binding site to anthracene carboximide fluorophore, and showed a significant visual change from yellow-green (535 nm) to deep violet (825 nm) with a larger redshift (≈ 290 nm) and fluorescence quenching at 480 nm and 520 nm upon interacting with cyanide. Job curves determined 1:1 binding stoichiometry of probe 3 with cyanide. Additonally, probe 3 detected cyanide ion conveniently in aqueous solution and could be reused after trifluoroacetic acid treatment. Colorimetric test paper was used to detect cyanide in aqueous solutions. The C-H deprotonation sensing mechanism was confirmed by ¹H NMR titration. The near-infrared detection of cyanide by CH-controlled probes was founded for the first time.

Aggregation-induced emission enhancement (AIEE)-active tetraphenylethene (TPE)-based chemosensor for CN. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021;245:118928. [PMID: 32950857 DOI: 10.1016/j.saa.2020.118928]

An aggregation-induced emission enhancement (AIEE)-active fluorescent sensor has been successfully designed and synthesized, combining the AIE effect of tetraphenylethylene (TPE) with the cyanide acceptor of phenanthro[9,10-d]imidazole. The sensor exhibits not only the property of AIEE in DCM/n-hexane or THF/H₂O, but also the phenomenon of mechanofluorochromic (MFC). It displays large Stokes shift (107 nm) due to the intramolecular charge transfer (ICT) process. The cation of CN^- boosts the ICT process to make the greater Stokes shift (184 nm) with the fluorescent color vary from blue-green to sodium-yellow and visually turning from light yellow to dark yellow in the naked eyes. The results of Job's plot, ESI-MS and the DFT calculations provide the stoichiometric ratio and electronic properties of the sensor. Furthermore, the sensor could be applied to qualitative and quantitative detection of CN^- on test paper strips.

Novel cyanide supramolecular fluorescent chemosensor constructed from a quinoline hydrazone functionalized-pillar[5]arene

Herein, we report a simple and novel approach for the design of fluorescent chemosensor through the self-assembly of functionalized monomer molecules. According to these approach, a novel supramolecular fluorescent chemosensor (SPMS) was successfully constructed by self-assembly of a quinoline hydrazone functionalized pillar[5]arene monomer PM. Interestingly, upon the addition of CN^-, the solution of SPMS instantly shows dramatic fluorescent enhancement and emitting bright blue emission. Meanwhile, the fluorescence quantum yields show distinct increase from 0.0582 of SPMS to 0.3952 of SPMS + CN^-. The detection limit (LOD) of SPMS for CN^- is 9.70 × 10^-8 M, which indicated high sensitivity. Moreover, the SPMS is selective for CN^- even in the presence of other anions, the fluorescent detection process of SPMS for CN^- was not interfered by other competitive anions (F^-, Cl^-, Br^-, I^-, N₃^-, OH^-, SCN^-, HSO₄^-, AcO^-, H₂PO₄^- and ClO₄^-). Notably, in the CN^- sensing process, the self-assembly structure of the supramolecular chemosensor SPMS didn't show any disassembly. This work provides a novel approach for instant detection of CN^- through a self-assembled supramolecular fluorescent chemosensor in aqueous system. Moreover, the test strips based on SPMS were fabricated, which could serve as convenient and efficient CN^- test kits.

A Highly Selective Chemosensor for Cyanide Derived from a Formyl-Functionalized Phosphorescent Iridium(III) Complex

A new phosphorescent iridium(III) complex, bis[2',6'-difluorophenyl-4-formylpyridinato-N,C4']iridium(III) (picolinate) (IrC), was synthesized, fully characterized by various spectroscopic techniques, and utilized for the detection of CN(-) on the basis of the widely known hypothesis of the formation of cyanohydrins. The solid-state structure of the developed IrC was authenticated by single-crystal X-ray diffraction. Notably, the iridium(III) complex exhibits intense red phosphorescence in the solid state at 298 K (ΦPL = 0.16) and faint emission in acetonitrile solution (ΦPL = 0.02). The cyanide anion binding properties with IrC in pure and aqueous acetonitrile solutions were systematically investigated using two different channels: i.e., by means of UV-vis absorption and photoluminescence. The addition of 2.0 equiv of cyanide to a solution of the iridium(III) complex in acetonitrile (c = 20 μM) visibly changes the color from orange to yellow. On the other hand, the PL intensity of IrC at 480 nm was dramatically enhanced ∼5.36 × 10(2)-fold within 100 s along with a strong signature of a blue shift of the emission by ∼155 nm with a detection limit of 2.16 × 10(-8) M. The cyanohydrin formation mechanism is further supported by results of a (1)H NMR titration of IrC with CN(-). As an integral part of this work, phosphorescent test strips have been constructed by impregnating Whatman filter paper with IrC for the trace detection of CN(-) in the contact mode, exhibiting a detection limit at the nanogram level (∼265 ng/mL). Finally, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were performed to understand the electronic structure and the corresponding transitions involved in the designed phosphorescent iridium(III) complex probe and its cyanide adduct.

Intracellular detection of Cu(2+) and S(2-) ions through a quinazoline functionalized benzimidazole-based new fluorogenic differential chemosensor

A new quinazoline functionalized benzimidazole-based fluorogenic chemosensor H3L is synthesized and fully characterized by conventional techniques including single crystal X-ray analysis. It acts as a highly selective colorimetric and fluorescence sensor for Cu(2+) ions in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Reaction of H3L with CuCl2 forms a mononuclear copper(ii) [Cu(Cl)(H2L)(H2O)] (H2L-Cu(2+)) complex which is characterized by conventional techniques and quantum chemical calculations. Electronic absorption and fluorescence titration studies of H3L with different metal cations show a distinctive recognition only towards Cu(2+) ions even in the presence of other commonly coexisting ions such as Li(+), Na(+), K(+), Mg(2+), Ca(2+), Fe(2+), Fe(3+), Mn(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+) and Hg(2+). Moreover, H2L-Cu(2+) acts as a metal based highly selective and sensitive chemosensor for S(2-) ions even in the presence of other commonly coexisting anions such as F(-), Cl(-), Br(-), I(-), SO4(2-), SCN(-), AcO(-), H2PO4(-), PO4(3-), NO3(-), ClO4(-), NO2(-), HSO4(-), HSO4(2-), S2O3(2-), S2O8(2-), CN(-), CO3(2-) and HCO3(-) in DMF/0.02 M HEPES (1 : 1, v/v, pH = 7.4) medium. Quantification analysis indicates that these receptors, H3L and H2L-Cu(2+), can detect the presence of Cu(2+) and S(2-) ions at very low concentrations of 1.6 × 10(-9) M and 5.2 × 10(-6) M, respectively. The propensity of H3L as a bio-imaging fluorescent probe for detection of Cu(2+) ions and sequential detection of S(2-) ions by H2L-Cu(2+) in Dalton lymphoma (DL) cancer cells is also shown.

Coumarin benzothiazole derivatives as chemosensors for cyanide anions

Four coumarin benzothiazole derivatives, N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (1), (Z)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide (2), 7-(diethylamino)-N-(benzo[d]thiazol-2-yl)-2-oxo-2H-chromene-3-carboxamide (3) and (Z)-7-(diethylamino)-N-(3-methylbenzo[d]thiazol-2(3H)-ylidene)-2-oxo-2H-chromene-3-carboxamide) (4), have been synthesized. Their crystal structures, photophysical properties in acetonitrile and recognition properties for cyanide anions have been investigated. All the compounds are generally planar, especially compound 1 exhibits perfect planarity with dihedral angle between benzothiazolyl group and coumarin group being only 3.63°. Coumarin benzothiazole compounds 1 and 3 can recognize cyanide anions by Michael addition reaction and compound 3 exhibits color change from yellow to colorless and green fluorescence was quenched completely, which can be observed by naked eye. Coumarin benzothiazolyliden compound 4 can recognize cyanide anions with fluorescence turn-on response based on the copper complex ensemble displacement mechanism.

A triphenylamine-based colorimetric and “turn-on” fluorescent probe for detection of cyanide anions in live cells

A triphenylamine–hemicyanine dye was developed as a colorimetric and turn-on fluorescent probe for detection of cyanide with high sensitivity and selectivity.

Rapid sodium cyanide depletion in cell culture media: Outgassing of hydrogen cyanide at physiological pH

During the course of in vitro studies on cyanide exposure with SH-SY5Y human neuroblastoma cells, we found that sodium cyanide (NaCN) up to a concentration of 10 mM had no significant toxic effect under our culture conditions. Further investigation of this apparent cyanide resistance revealed that the sodium cyanide was being rapidly depleted from the cell culture medium. Cyanide was interacting with constituents of the cell culture medium and was somehow being detoxified or removed from solution. The reaction of cyanide with cell culture media in 96-well culture plates reduced cyanide concentrations rapidly (80-90% in 2 h at 37 degrees C). Running the same reaction in capped tubes significantly reduced cyanide loss from solution. Incubation of cyanide with individual constituents of the cell culture medium in solution showed that glucose, phenol red, and amino acids all acted to detoxify or remove cyanide from solution. When amino acids or buffers were incubated with sodium cyanide in aqueous solution at pH 7.4, hydrogen cyanide (HCN) was found to degas from the solutions. We compared HCN outgassing over a range of pH values. As expected, HCN remained very soluble at high pH, but as the pH was reduced to 7.0, the rate of HCN formation and outgassing increased dramatically. Acid-base reactions involving cyanide and proton donors, such as amino acids and other cell culture media constituents, at physiological pH result in rapid HCN outgassing from solution at 37 degrees C. These results indicate that previous in vitro cyanide toxicity studies done in standard culture media with prolonged incubation times using gas-exchanging culture containers might have to be reevaluated in light of the fact that the effective cyanide concentrations in the culture media were significantly lower than reported.

Mechanism of action of sodium cyanide on rat diaphragm muscle

The effects of sodium cyanide (NaCN) were investigated on the contractile and electrophysiological properties of rat diaphragm muscles in vitro. Sodium cyanide (0.1-1.0 mM) produced an initial potentiation of directly elicited twitch tensions, followed by a slow progressive depression. The potentiation and depression were both dependent on the NaCN concentration and stimulation frequency. Muscles exposed to NaCN exhibited marked reductions of creatine phosphate concentration, but ATP levels were not significantly lowered. Sodium cyanide had no effect on the resting potential, input resistance or action potential, indicating that the toxicity of the metabolic inhibitor is not mediated by alterations of membrane excitability or passive electrical properties. Sodium cyanide reduced the amplitude of contractures elicited by 70 mM K(2)SO(4), suggesting that the actions of NaCN cannot be explained by a failure of action potentials to propagate across the muscle surface or within t-tubular membranes. Sodium cyanide suppressed the first phase of the caffeine contracture, an observation consistent with an impaired release of, or reduced sensitivity to, sarcoplasmic reticular Ca(2+), but did not alter the amplitude of the second phase, which represents rigor following ATP depletion. These results, in conjunction with those of previous studies, suggest that the depression in muscle tension following exposure to NaCN may result from alterations in Ca(2+) homeostasis, intracellular acidosis or from accumulation of one or more products of phosphocreatine breakdown.