Showing papers on "Cyanide published in 2011"

Colorimetric probes based on anthraimidazolediones for selective sensing of fluoride and cyanide ion via intramolecular charge transfer.

Abstract: Probes based on anthra[1,2-d]imidazole-6,11-dione were designed and synthesized for selective ion sensing. Each probe acted as strong colorimetric sensors for fluoride and cyanide ions and exhibited intramolecular charge transfer (ICT) band, which showed significant red-shifts after addition of either the F(-) or CN(-) ion. One of the probes (2) showed selective colorimetric sensing for both cyanide and fluoride ions. In organic medium, 2 showed selective color change with fluoride and cyanide, whereas in aqueous organic medium it showed a ratiometric response selectively for cyanide ion.

Poisoning the Oxygen Reduction Reaction on Carbon-Supported Fe and Cu Electrocatalysts: Evidence for Metal-Centered Activity

Abstract: Whether or not the active sites for the oxygen reduction reaction (ORR) in electrocatalysts based on carbon-supported transition-metal complexes are metal-centered has become controversial, especially for heat-treated materials. Some have proposed that the transition metal only serves to form highly active sites based on nitrogen and carbon. Here, we examine the oxygen reduction activity of carbon-supported iron(II) phthalocyanine (FePc) before and after pyrolysis at 800 °C and a carbon-supported copper(II) complex with 3,5-diamino-1,2,4-triazole (CuDAT) in the presence of several anions and small-molecule poisons, including fluoride, azide, thiocyanate, ethanethiol, and cyanide. CuDAT is poisoned in a manner consistent with a Cu-based active site. Although FePc and pyrolyzed FePc are remarkably resilient to most poisons, they are poisoned by cyanide, indicative of Fe-based active sites.

Controlled Intramolecular Electron Transfers in Cyanide-Bridged Molecular Squares by Chemical Modifications and External Stimuli

Abstract: A series of cyanide bridged Fe−Co molecular squares, [Co2Fe2(CN)6(tp*)2(dtbbpy)4](PF6)2·2MeOH (1), [Co2Fe2(CN)6(tp*)2(bpy)4](PF6)2·2MeOH (2), and [Co2Fe2(CN)6(tp)2(dtbbpy)4](PF6)2·4H2O (3) (tp = hydrotris(pyrazol-1-yl)borate, tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate, bpy =2,2′-bipyridine, dtbbpy =4,4′-di-tert-butyl-2,2′-bipyridine), were prepared by the reactions of [Fe(CN)3(L)]− (L = tp or tp*) with Co2+ and bidentate ligands (bpy or dtbbpy) in MeOH. In the molecular squares, Fe and Co ions are alternately bridged by cyanide ions, forming macrocyclic tetranuclear cores. Variable temperature X-ray structural analyses and magnetic susceptibility measurements confirmed that 1 exhibits two-step charge-transfer induced spin transitions (CTIST) centered at T1/2 = 275 and 310 K in the solid state. The Fe and Co ions in 1 are the low-spin (LS) Fe(III) and high-spin (HS) Co(II) ions, described here in the high-temperature (HT) phase ([FeIIILS2CoIIHS2]) at 330 K, while a low-temperature (LT) phase ([FeIILS2...

A Review of Acute Cyanide Poisoning With a Treatment Update

Abstract: Cyanide causes intracellular hypoxia by reversibly binding to mitochondrial cytochrome oxidase a(3). Signs and symptoms of cyanide poisoning usually occur less than 1 minute after inhalation and within a few minutes after ingestion. Early manifestations include anxiety, headache, giddiness, inability to focus the eyes, and mydriasis. As hypoxia progresses, progressively lower levels of consciousness, seizures, and coma can occur. Skin may look normal or slightly ashen, and arterial oxygen saturation may be normal. Early respiratory signs include transient rapid and deep respirations. As poisoning progresses, hemodynamic status may become unstable. The key treatment is early administration of 1 of the 2 antidotes currently available in the United States: the well-known cyanide antidote kit and hydroxocobalamin. Hydroxocobalamin detoxifies cyanide by binding with it to form the renally excreted, non-toxic cyanocobalamin. Because it binds with cyanide without forming methemoglobin, hydroxocobalamin can be used to treat patients without compromising the oxygen-carrying capacity of hemoglobin.

Rational design of a dual chemosensor for cyanide anion sensing based on dicyanovinyl-substituted benzofurazan.

Abstract: A dicyanovinyl-substituted benzofurazan derivative (C1) was prepared as an efficient ratiometric chemosensor for cyanide anion detection in aqueous acetonitrile solution. Mechanism studies suggested that the nucleophilic addition of cyanide to the α-position of the dicyanovinyl group blocked the ICT progress of C1 and induced remarkable emission and absorption shift.

Turn-On Fluorescence Sensing of Cyanide Ions in Aqueous Solution at Parts-per-Billion Concentrations

Abstract: Cyanide is a highly toxic anion that has become a key component of many industrial processes. It is also produced naturally by a number of higher plants, which use it as a protection against predators. Release of this anion in the environment and an increase in the farming and consumption of cyanogenic plants such as cassava have served to spark a renewed interest in methods that can be used to sense the presence of this anion, especially in aqueous media. One of the current strategies adopted for the design of cyanide sensors is based on the use of electrophilic organic derivatives, which interact with the cyanide anion through formation of a new covalent bond. Although advantageous properties have been discovered, only a limited number of receptors function in water. f,m,7] Some of these receptors necessitate basic pH and high cyanide concentrations. Because of these limitations, strategies that rely on the use of Lewis acidic derivatives have been considered. Such derivatives include zinc–porphyrins, iron–hemes, corrins, and transition-metal complexes that interact with the cyanide anion through formation of a strong coordination bond. This approach, which is typically characterized by elevated binding constants, has been successfully applied to the detection of cyanide at the ppm level. Some of these receptors have also been shown to be compatible with biological matrices, making the detection of cyanide possible directly in plants. As demonstrated by a series of recent contributions, three-coordinate boranes possessing an accessible boron center can also be used as sensors for cyanide anions. Whereas neutral boranes can only be used in mostly organic environments, we and others have demonstrated that the incorporation of peripheral cationic groups in such compounds could be used to enhance their cyanide ion affinity. Although the cyanide affinity displayed by some of these boranes is very high, their practical use remains limited by the nature of the photophysical response observed during the recognition event. Indeed, cyanide coordination leads to population of the empty p orbital of boron, thus quenching the absorbance and fluorescence of the triarylboron chromophore. The turn-off rather than turn-on response observed in these complexes is not ideal from an analytical point of view and constitutes one of the major limitations affecting the practical use of cationic boranes as cyanide sensors. In order to overcome this limitation, we have now synthesized para-phenylene phosphonium borane/fluorophore conjugates, which behave as highly sensitive fluorescence turn-on sensors for the cyanide anion in aqueous solutions. Reaction of p-Ph2P-C6H4-BMes2 (Mes=mesityl) with 9bromomethyl anthracene in toluene, which was heated to reflux, afforded [1]Br in 82% yield (Scheme 1). A similar reaction involving p-Ph2P-C6H4-BMes2 and N-(3-bromo-

Hydrogenation of solid hydrogen cyanide HCN and methanimine CH2NH at low temperature

Abstract: Context. Hydrogenation reactions dominate grain surface chemistry in dense molecular clouds and lead to the formation of complex saturated molecules in the interstellar medium.Aims. We investigate in the laboratory the hydrogenation reaction network of hydrogen cyanide HCN.Methods. Pure hydrogen cyanide HCN and methanimine CH2 NH ices are bombarded at room temperature by H-atoms in an ultra-high vacuum experiment. Warm H-atoms are generated in an H2 plasma source. The ices are monitored with Fourier-transform infrared spectroscopy in reflection absorption mode. The hydrogenation products are detected in the gas phase by mass spectroscopy during temperature-programmed desorption experiments.Results. HCN hydrogenation leads to the formation of methylamine CH3 NH2 , and CH2 NH hydrogenation leads to the formation of methylamine CH3 NH2 , suggesting that CH2 NH can be a hydrogenation-intermediate species between HCN and CH3 NH2 . Conclusions. In cold environments the HCN hydrogenation reaction can produce CH3 NH2 , which is known to be a glycine precursor, and to destroy solid-state HCN, preventing its observation in molecular clouds ices.

Burning vegetation produces cyanohydrins that liberate cyanide and stimulate seed germination

Abstract: Cyanide is well known for its toxicity towards living organisms. Many plants use cyanide as a defensive agent against herbivores, releasing it through the enzymatic hydrolysis of endogenous cyanogenic compounds. At low concentrations, cyanide has been proposed to have a regulatory role in many plant processes including stimulation of seed germination. However, no ecological role for cyanide in seed germination has been established. In the present study, we show that burning plant material produces the cyanohydrin, glyceronitrile. We also show that, in the presence of water, glyceronitrile is slowly hydrolysed to release cyanide that stimulates seed germination of a diverse range of fire-responsive species from different continents. We propose that glyceronitrile serves as an ecological store for cyanide and is an important cue for stimulating seed germination and landscape regeneration after fires.

Solid-state emissive triarylborane-based BODIPY dyes: photophysical properties and fluorescent sensing for fluoride and cyanide ions.

Abstract: We disclose two novel BODIPY dyes, which contain the bulky substituent, [(4-dimesitylboryl)phenyl]ethynyl at 2- and 2,6-positions. The steric bulkiness of the boryl group is effective to suppress the intermolecular interaction in the solid state and thus these two compounds display intense fluorescence not only in solution but also in the solid state. In addition, the BODIPY dyes display sensitive fluorescence responses to fluoride and cyanide anions through the complexation with the boron center of the boryl group and the subsequent decomposition of the BODIPY core, illustrating their potential uses for the fluorescence sensing of fluoride and cyanide ions.

A TD‐DFT study on the cyanide‐chemosensing mechanism of 8‐formyl‐7‐hydroxycoumarin

Abstract: Proton transfer (PT) and excited-state PT process are proposed to account for the fluorescent sensing mechanism of a cyanide chemosensor, 8-formyl-7-hydroxycoumarin. The time-dependent density functional theory method has been applied to investigate the ground and the first singlet excited electronic states of this chemosensor as well as its nucleophilic addition product with cyanide, with a view to monitoring their geometries and spectrophotometrical properties. The present theoretical study indicates that phenol proton of the chemosensor transfers to the formyl group along the intramolecular hydrogen bond in the first singlet excited state. Correspondingly, the nucleophilic addition product undergoes a PT process in the ground state, and shows a similar structure in the first singlet excited state. This could explain the observed strong fluorescence upon the addition of the cyanide anion in the relevant fluorescent sensing mechanism.

Highly Selective and Sensitive Detection of Cyanide by a Reaction-Based Conjugated Polymer Chemosensor

Abstract: Based on a specific nucleophilic addition reaction with cyanide, a dicyano-vinyl-containing conjugated polymer (P1) has been designed and synthesized as a colorimetric and fluorescent chemosensor for cyanide anion. The combination of advantages of both reaction-based sensors and conjugated polymer sensors offers its highly sensitive and selective recognition of CN(-). The addition of CN(-) to P1 solution induced a change in the solution color from yellow-green to colorless, while no color change could be observed in presence of other common anions, by which CN(-) can be identified from other anions directly with the naked eye. At the same time, a 31.6-fold fluorescence quenching was achieved upon adding CN(-) into P1 solution. The fluorescence quenching has shown a linear response to CN(-) in the concentration range of 0.5-30 mu M. Furthermore, its detection limit for CN(-) can be as low as 14 ppb, which is among the best results for the fluorescent conjugated polymer-based cyanide chemosensors. Compared with its small molecular counterpart, P1 exhibits higher sensitivity and selectivity, wider linear region, and faster response.

A Selective, Sensitive, and Chromogenic Chemodosimeter for Cyanide Based on the 1,1′-Binaphthyl Scaffold

Abstract: A highly selective chemodosimeter 1 for cyanide based on the 1,1′-binaphthyl skeleton is described which demonstrated significant visual change and a low limit of detection. Interestingly, a reversible process triggered successively by CN– and Au3+ is also observed and determined by fluorescence, UV–vis spectra, 1H NMR titration, and ESI–MS.

Cyanide intoxication as part of smoke inhalation--a review on diagnosis and treatment from the emergency perspective

Abstract: This paper reviews the current literature on smoke inhalation injuries with special attention to the effects of hydrogen cyanide. It is assumed that cyanide poisoning is still an overlooked diagnosis in fire victims. Treatment against cyanide poisoning in the emergency setting should be given based on the clinical diagnosis only. Oxygen in combination with a recommended antidote should be given immediately, the first to reduce cellular hypoxia and the second to eliminate cyanide. A specific antidote is hydroxycobalamin, which can be given iv. and has few side effects.

A Label‐Free Gold‐Nanoparticle‐Based SERS Assay for Direct Cyanide Detection at the Parts‐per‐Trillion Level

Abstract: Cyanide is an extremely toxic lethal poison known to humankind. Developing rapid, highly sensitive, and selective detection of cyanide from water samples is extremely essential for human life safety. Driven by the need, here we report a gold-nanoparticle-based label-free surface-enhanced Raman spectroscopy (SERS) system for highly toxic cyanide ion recognition in parts-per-trillion level and to examine gold-nanoparticle-cyanide interaction. We have shown that the SERS assay can be used to probe the gold nanoparticle dissociation process in the presence of cyanide ions. Our experimental data indicates that gold-nanoparticle-based SERS can detect cyanide from a water sample at the 110 ppt level with excellent discrimination against other common anions and cations. The results also show that the SERS probe can be used to detect cyanide from environmental samples.

Cyanides-Free Cyanation of Aryl Halides using Formamide

Abstract: A novel method for cyanation of aryl halides using formamide as a non-toxic cyanide source is reported. It is a single-step, solvent-free method wherein formamide itself acts as solvent as well as source of cyanide in the presence of phosphorus oxychloride and palladium acetate/xantphos catalyst. Aryl iodides as well as aryl bromides provided moderate to excellent yields of up to 93%.

Copper(I)‐Mediated Cyanation of Boronic Acids

Abstract: A simple cyanation reaction of boronic I acids with cuprous cyanide is achieved, providing nitriles in moderate to good yields. In the presence of copper(I) iodide, trimethylsilyl cyanide is also a good cyanating reagent. The reaction can be conducted on a 10-mmol scale. Thus, this new approach represents an exceedingly practical method for the synthesis of nitriles.

Tuning and Switching MLCT Phosphorescence of [Ru(bpy)3]2+ Complexes with Triarylboranes and Anions

Abstract: Four new Ru(II) complexes, [Ru(bpy)2(4,4′-BP2bpy)][PF6]2 (1), [Ru(t-Bu-bpy)2(4,4′-BP2bpy)][PF6]2 (2), [Ru(bpy)2(5,5′-BP2bpy)][PF6]2 (3), and [Ru(t-Bu-bpy)2(5,5′-BP2bpy)][PF6]2 (4) have been synthesized (where 4,4′-BP2bpy = 4,4′-bis(BMes2phenyl)-2,2′-bpy; 5,5′-BP2bpy = 5,5′-bis(BMes2phenyl)-2,2′-bpy (4,4′-BP2bpy); and t-Bu-bpy = 4,4′-bis(t-butyl)-2,2′-bipyridine). These new complexes have been fully characterized. The crystal structures of 3 and 4 were determined by single-crystal X-ray diffraction analyses. All four complexes display distinct metal-to-ligand charge transfer (MLCT) phosphorescence that has a similar quantum efficiency as that of [Ru(bpy)3][PF6]2 under air, but is at a much lower energy. The MLCT phosphorescence of these complexes has been found to be highly sensitive toward anions such as fluoride and cyanide, which switch the MLCT band to higher energy when added. The triarylboron groups in these compounds not only introduce this color switching mechanism, but also play a key role in the ...

Cyanide, a coproduct of plant hormone ethylene biosynthesis, contributes to the resistance of rice to blast fungus.

Abstract: Rice (Oryza sativa) plants carrying the Pi-i resistance gene to blast fungus Magnaporthe oryzae restrict invaded fungus in infected tissue via hypersensitive reaction or response (HR), which is accompanied by rapid ethylene production and formation of small HR lesions. Ethylene biosynthesis has been implicated to be important for blast resistance; however, the individual roles of ethylene and cyanide, which are produced from the precursor 1-aminocyclopropane-1-carboxylic acid, remain unevaluated. In this study, we found that Pi-i-mediated resistance was compromised in transgenic rice lines, in which ethylene biosynthetic enzyme genes were silenced and then ethylene production was inhibited. The compromised resistance in transgenic lines was recovered by exogenously applying cyanide but not ethephon, an ethylene-releasing chemical in plant tissue. In a susceptible rice cultivar, treatment with cyanide or 1-aminocyclopropane-1-carboxylic acid induced the resistance to blast fungus in a dose-dependent manner, while ethephon did not have the effect. Cyanide inhibited the growth of blast fungus in vitro and in planta, and application of flavonoids, secondary metabolites that exist ubiquitously in the plant kingdom, enhanced the cyanide-induced inhibition of fungal growth. These results suggested that cyanide, whose production is triggered by HR in infected tissue, contributes to the resistance in rice plants via restriction of fungal growth.

A highly sensitive and selective fluorescent probe for cyanide based on the dissolution of gold nanoparticles and its application in real samples.

Abstract: We report a simple fluorescence method for detection of cyanide sensitively and selectively based on the dissolution of polymer-coated gold nanoparticles by cyanide. The lowest concentration for quantification of cyanide ions was 3.0×10(-7) M, and other common anions nearly have no influence. Furthermore, several real water samples spiked with cyanide, including local groundwater, tap water, boiled water, and lake water, were analyzed, and the experimental results demonstrated that our sensing system worked well in the above water samples, with a good linear correlation.