Turn-on fluorescence sensing of cyanide ions in aqueous solution简

A sensitive fluorescent probe, 2,2＇-bisbenzimidazole （L）, for CN has been developed. This structurally simple receptor displays great selectivity for the cyanide anion over other common inorganic anions in an aqueous environment. In addition, further study demonstrates the lower detection of the fluorescence response of the sensor to CN is in 10 9 mol/L range. Thus, the present probe should be applicable as a practical system for the monitoring of cyanide concentrations in aqueous samples.     

A green synthesis of a simple chemosensor that could instantly detect cyanide with high selectivity in aqueous solution

A novel and simple cyanide chemosensor 2-(naphthalen-1-ylmethylene)malononitrile(L) was designed and synthesized via a green chemistry method in water without using any catalyst.The chemosensor showed an excellent sensitivity and selectivity for CN in aqueous solution.The detection limit could be as low as 1.6×10~7 moI/L(0.16μmol/L),which is far lower than the WHO guideline of 1.9μmol/L cyanide for drink water.     

A rapid responsive and highly selective probe for cyanide in the aqueous environment

A colorimetric and fluorescent cyanide probe based on 7-(trifluoroacetamino)coumarin has been prepared. This structurally simple probe displays rapid response and high selectivity for cyanide over other common anions in the aqueous solution. The sensing of cyanide was performed via the nucleophilic attack of cyanide anion to carbonyl of the probe with a 1:1 binding stoichiometry, which could be confirmed by Job’s plot, ¹H NMR, and MS studies. DFT/TDDFT calculations support that the fluorescence enhancement of the probe is mainly due to the ICT process improvement. The detection limit of the fluorescent assay for cyanide is as low as 0.3 μM in a rapid response of less than 30 s. Thus, the present probe should be applicable as a practical system for the monitoring of cyanide concentrations in aqueous samples.     

国内离子交换法处理氰化镉废水的现状及改进意见

本文对国内现行离子交换法处理氰化镀镉废水的工艺进行了探讨，提出了用络合理论将阴树脂由Ｃｌ－１型转变成ＣｄＣｌ４２－型后交换，便可提高对水中游离氰（ＣＮ－）的吸附能力，并能使氰、镉都得到回收利用。     

Solubility, complex formation, and redox reactions in the Tl2O3-HCN/CN(-)-H2O system. Crystal structures of the cyano compounds Tl(CN)3.H2O, Na[Tl(CN)4].3H2O, K[Tl(CN)4], and Tl(I)[Tl(III)(CN)4] and of Tl(I)2C2O4

Thallium(III) oxide can be dissolved in water in the presence of strongly complexing cyanide ions. Tl(III) is leached from its oxide both by aqueous solutions of hydrogen cyanide and by alkali-metal cyanides. The dominating cyano complex of thallium(III) obtained by dissolution of Tl2O3 in HCN is [Tl(CN)3(aq)] as shown by 205Tl NMR. The Tl(CN)3 species has been selectively extracted into diethyl ether from aqueous solution with the ratio CN-/Tl(III) = 3. When aqueous solutions of the MCN (M = Na+, K+) salts are used to dissolve thallium(III) oxide, the equilibrium in liquid phase is fully shifted to the [Tl(CN)4]- complex. The Tl(CN)3 and Tl(CN)4- species have for the first time been synthesized in the solid state as Tl(CN)3.H2O (1), M[Tl(CN)4] (M = Tl (2) and K (3)), and Na[Tl(CN)4].3H2O (4) salts, and their structures have been determined by single-crystal X-ray diffraction. In the crystal structure of 1, the thallium(III) ion has a trigonal bipyramidal coordination with three cyanide ions in the equatorial plane, while an oxygen atom of the water molecule and a nitrogen atom from a cyanide ligand, attached to a neighboring thallium complex, form a linear O-Tl-N fragment. In the three compounds of the tetracyano-thallium(III) complex, 2-4, the [Tl(CN)4]- unit has a distorted tetrahedral geometry. Along with the acidic leaching (enhanced by Tl(III)-CN- complex formation), an effective reductive dissolution of the thallium(III) oxide can also take place in the Tl2O3-HCN-H2O system yielding thallium(I), while hydrogen cyanide is oxidized to cyanogen. The latter is hydrolyzed in aqueous solution giving rise to a number of products including (CONH2)2, NCO-, and NH4+ detected by 14N NMR. The crystalline compounds, Tl(I)[Tl(III)(CN)4], Tl(I)2C2O4, and (CONH2)2, have been obtained as products of the redox reactions in the system.     

Adsorption behavior of copper and cyanide ions at TiO2-solution interface

Adsorption of both copper and cyanide ions in the absence and in the presence of their complexes at TiO2-solution interfaces was investigated. The objective of this study was to demonstrate the possibility of removing heavy metal ions, exemplified by Cu(II), from aqueous solution in the presence of a ligand, e.g., CN-. Several parameters such as pH and Cu(II) and CH- ion concentration that may affect the magnitude of copper and cyanide adsorption were studied. The equilibrium of Cu-CN speciation distribution in solution and stability constant calculations have been investigated to determine the adsorption behavior of Cu(II). Results revealed that free Cu(II) ions (in the absence of CN-) were completely separated at pH8, while the adsorption of free cyanide ions, in the absence of Cu(II), reached a maximum value of 48% at pH 7. For Cu-CN complexes, the presence of CN- in excessive amount with respect to Cu(II) retarded the adsorption of Cu(II). This is attributed to the formation of multivalent anionic cyano-copper complexes such as Cu(CN)2-(3) and Cu(CN)(3-)4.     

碘—淀粉络合物褪色光度法测定微量氰化物

研究了在 p H 7.0的混合磷酸盐缓冲溶液条件下 ,氰根使碘与淀粉形成的蓝色络合物褪色 ,络合物吸光度的降低值 ΔA与加入的氰根量成正比。 λmax=570 nm,氰根在 0～ 2 0 μg/2 5ml范围内呈良好的线性关系 ,检出限为 0 .52μg/2 5ml,其表观摩尔吸光系数为 2 .6× 1 0 4 ,方法成功地用于含氰废水中氰化物的测定。     

基于偶氮水杨醛酰腙的氰根比色检测探针的合成及性能

设计合成了一种基于酚羟基和氨基的酰腙类探针分子, 利用紫外-可见吸收光谱和核磁滴定考察了其对F^-, Cl^-, Br^-, I^-, CH₃COO^-, H₂PO₄^-, HSO₄^-, ClO₄^-, CN^-, SCN^-, SO^2-₄和NO^-₃等阴离子的识别作用. 结果表明, 当加入CN^-离子时主体溶液颜色由无色变为黄色, 而加入其它离子时主体溶液颜色不变, 说明该探针在DMSO/H₂O(体积比5: 5)体系中能选择性裸眼比色检测CN^-. 核磁滴定及质谱数据表明, 该探针与CN^-以1:1化学计量比结合, 该过程通过亲核加成方式完成.     

Investigating CN- cleavage by three-coordinate M[N(R)Ar]3 complexes

Three-coordinate Mo[N((t)Bu)Ar]3 binds cyanide to form the intermediate [Ar((t)Bu)N]3Mo-CN-Mo[N((t)Bu)Ar]3 but, unlike its N2 analogue which spontaneously cleaves dinitrogen, the C-N bond remains intact. DFT calculations on the model [NH2]3Mo/CN- system show that while the overall reaction is significantly exothermic, the final cleavage step is endothermic by at least 90 kJ mol(-1), accounting for why C-N bond cleavage is not observed experimentally. The situation is improved for the [H2N]3W/CN- system where the intermediate and products are closer in energy but not enough for CN- cleavage to be facile at room temperature. Additional calculations were undertaken on the mixed-metal [H2N]3Re+/CN- /W[NH2]3 and [H2N]3Re+/CN-/Ta[NH2]3 systems in which the metals ions were chosen to maximise the stability of the products on the basis of an earlier bond energy study. Although the reaction energetics for the [H2N]3Re+/CN /W[NH2]3 system are more favourable than those for the [H2N]3W/CN- system, the final C-N cleavage step is still endothermic by 32 kJ mol(-1) when symmetry constraints are relaxed. The resistance of these systems to C-N cleavage was examined by a bond decomposition analysis of [H2N]M-L1[triple bond]L2-M[NH2]3 intermediates for L1[triple bond]L2 = N2, CO and CN which showed that backbonding from the metal into the L1[triple bond]L2 pi* orbitals is significantly less for CN than for N2 or CO due to the negative charge on CN- which results in a large energy gap between the metal d(pi), and the pi* orbitals of CN-. This, combined with the very strong M-CN- interaction which stabilises the CN intermediate, makes C-N bond cleavage in these systems unfavourable even though the C[triple bond]N triple bond is not as strong as the bond in N2 or CO.     

The benzil-cyanide reaction and its application to the development of a selective cyanide anion indicator

The benzil-cyanide reaction is a cyanide-specific reaction that has been exploited to produce a colorimetric indicator for this toxic anion. This was done by producing a pi-extended analogue of benzil, 7, which is soluble in a 70:30 (v/v) mixture of methanol-water. In this medium, dilute solutions of 7 are yellow but produce colorless products when exposed to low concentrations of cyanide anion (> or = 1.7 microM; added as an aqueous NaCN solution), but no other common anions (e.g., OH(-), F(-), N3(-), benzoate(-), and H2PO4(-)). On the basis of these observations and supporting mechanistic analyses, it is concluded that the modified benzil system 7 is a promising cyanide anion indicator that is attractive in terms of its selectivity, ease-of-use, water compatibility, and the low, naked-eye discernible cyanide detection limit it provides.     

Quinone—cyanide reactions: their use for the determination of quinones and cyanide

Both quinones and cyanide can be determined in the μg—ng ml^-1 range by measuring the fluorescence of the addition products produced. The yield is low (except for the 2-sulfonic acid of 1,4-naphthoquinone) in aqueous solution and 1:1 DMSO:water is the recommended medium for determinations of quinones. The 2-sulfonic acid of 1,4-naphthoquinone permits the determination of trace amounts of cyanide in aqueous solution; there are few interferences.     

A highly selective and synthetically facile aqueous-phase cyanide probe

Disperse Orange 3 (4-(4-nitrophenylazo)aniline)-based chemosensor 1 has been prepared. This structurally simple receptor displays great selectivity for the cyanide anion over other common inorganic anions in aqueous environment and can detect cyanide in water sample at micromolar concentrations.     

Theoretical investigations of uranyl-ligand bonding: four- and five-coordinate uranyl cyanide, isocyanide, carbonyl, and hydroxide complexes

The coordination and bonding of equatorial hydroxide, carbonyl, cyanide (CN-), and isocyanide (NC-) ligands with uranyl dication, [UO2]2+, has been studied using density functional theory with relativistic effective core potentials. Good agreement is seen between experimental and calculated geometries of [UO2(OH)4]2-. Newly predicted ground-state structures of [UO2(OH)5]3-, [UO2(CO)4]2+, [UO2(CO)5]2+, [UO2(CN)4]2-, [UO2(CN)5]3-, [UO2(NC)4]2-, and [UO2(NC)5]3- are reported. Four-coordinate uranyl isocyanide complexes are the predicted gas-phase species while five-coordinate uranyl cyanide complexes are energetically favorable in aqueous solution. Small energy differences between cyanide and isocyanide complexes indicate the energetic feasibility of mixed cyanide and isocyanide complexes. A D2d uranyl tetrahydroxide is the dominant gas-phase and aqueous species, but formation of uranyl carbonyl complexes is seen to be exothermic in the gas-phase and endothermic in aqueous solution.     

Kinetic and thermodynamic studies on ligand substitution reactions and base-on/base-off equilibria of cyanoimidazolylcobamide, a vitamin B12 analog with an imidazole axial nucleoside

Ligand substitution reactions of the vitamin B12 analog cyanoimidazolylcobamide, CN(Im)Cbl, with cyanide were studied. Cyanide substitutes imidazole (Im) in the alpha-position more slowly than it substitutes dimethylbenzimidazole in cyanocobalamin (vitamin B12). The kinetics of the displacement of Im by CN- showed saturation behaviour at high cyanide concentration; the limiting rate constant was found to be 0.0264 s(-1) at 25 degrees C and is characterized by the activation parameters: DeltaH(not =) = 111 +/- 2 kJ mol(-1), DeltaS(not =) = +97 +/- 6 J K(-1) mol(-1), and DeltaV(not =) = +9.3 +/- 0.3 cm3 mol(-1). These parameters are interpreted in terms of an I(d) mechanism. The equilibrium constant for the reaction of CN(Im)Cbl with CN- was found to be 861 +/- 75 M(-1), which is significantly less than that obtained for the reaction of cyanocobalamin with CN- (viz. 10(4) M(-1)). pKbase-off for the base-on/base-off equilibrium was determined spectrophotometrically and found to be 0.99 +/- 0.05, which is about 0.9 pH units higher than that obtained previously in the case of cyanocobalamin. In addition, the kinetics of the base-on/base-off reaction was studied using a pH-jump technique and the data obtained revealed evidence for an acid catalyzed reaction path. The results obtained in this study are discussed in reference to those reported previously for cyanocobalamin.     

Determination of cyanide using a microbial sensor

A microbial cyanide sensor was prepared, consisting of immobilizedSaccharomyces cerevisiae and an oxygen electrode. When the electrode was inserted into a solution containing glucose, the respiration activity of the microorganisms increased. The change in the respiration activity is monitored with the oxygen electrode. When cyanide is added to the sample solution, the electron transport chain reaction of the respiration system in the mitochondria is inhibited, resulting in a decrease in respiration. The inhibition is caused by cyanide binding with respiration enzymes such as the cytochrome oxidase complex in the mitochondrial inner membrane. Therefore, the cyanide concentration can be measured from the change in the respiration rate. When the sensor was applied to a batch system at pH 8.0 and 30°C, the cyanide calibration curve showed linearity in the concentration range between 0.3 μM and 150 μM CN-.     

An unusually acidic methyl group directly bound to acridinium cation

9,10-Dimethylacridinium chloride (1: X = Cl) exhibited strong acidity of pH 3.90 (3.4 x 10(-3) M, 20 degrees C) in an aqueous solution. H-D exchange reaction of 1 in D2O indicated that protons in the 9-methyl group dissociated to generated H+ ions. This is a unique example of a methyl proton functioning as an acid. The acidity derives from the wider pi face in acridinium capable of delocalizing the newly formed negative charge upon proton dissociation. PM3 calculations provided stabilization factors (deltaDeltaH(f)o) between proton dissociated and undissociated forms of several N-heterocycles and also confirmed the acidity observed in acridinium.     

Über die Zersetzlichkeit komplexer Metallcyanide bei der Cyanidbestimmung in Abwasser

Serial studies on the behaviour of simple and complex cyanides against the attack of dilute sulphuric acid within the determination of “total cyanide” in waste water resulted in the cyanide complexes of zinc, cadmium, copper, nickel, iron(II) and iron(III) being decomposed quite rapidly by dilute sulphuric acid in the concentration range of ≦ 100 mg CN-/l. Consequently, in such cases the total amount of cyanide can be determined in the first 25 ml of the distillate.     

Lanthanide Complexes that Respond to Changes in Cyanide Concentration in Water

Cyanide ions are shown to interact with lanthanide complexes of phenacylDO3A derivatives in aqueous solution, giving rise to changes in the luminescence and NMR spectra. These changes are the consequence of cyanohydrin formation, which is favored by the coordination of the phenacyl carbonyl group to the lanthanide center. These complexes display minimal affinity for fluoride and can detect cyanide at concentrations less than 1 μm . By contrast, lanthanide complexes with DOTAM derivatives display no affinity for cyanide in water, but respond to changes in fluoride concentration.     

Mechanisms of catalyst poisoning in palladium-catalyzed cyanation of haloarenes. remarkably facile C-N bond activation in the [(Ph3P)4Pd]/[Bu4N]+ CN- system

Reaction paths leading to palladium catalyst deactivation during cyanation of haloarenes (eq 1) have been identified and studied. Each key step of the catalytic loop (Scheme 1) can be disrupted by excess cyanide, including ArX oxidative addition, X/CN exchange, and ArCN reductive elimination. The catalytic reaction is terminated via the facile formation of inactive [(CN)4Pd]2-, [(CN)3PdH]2-, and [(CN)3PdAr]2-. Moisture is particularly harmful to the catalysis because of facile CN- hydrolysis to HCN that is highly reactive toward Pd(0). Depending on conditions, the reaction of [(Ph3P)4Pd] with HCN in the presence of extra CN- can give rise to [(CN)4Pd]2- and/or the remarkably stable new hydride [(CN)3PdH]2- (NMR, X-ray). The X/CN exchange and reductive elimination steps are vulnerable to excess CN- because of facile phosphine displacement leading to stable [(CN)3PdAr]2- that can undergo ArCN reductive elimination only in the absence of extra CN-. When a quaternary ammonium cation such as [Bu4N]+ is used as a phase-transfer agent for the cyanation reaction, C-N bond cleavage in the cation can occur via two different processes. In the presence of trace water, CN- hydrolysis yields HCN that reacts with Pd(0) to give [(CN)3PdH]2-. This also releases highly active OH- that causes Hofmann elimination of [Bu4N]+ to give Bu3N, 1-butene, and water. This decomposition mode is therefore catalytic in H2O. Under anhydrous conditions, the formation of a new species, [(CN)3PdBu]2-, is observed, and experimental studies suggest that electron-rich mixed cyano phosphine Pd(0) species are responsible for this unusual reaction. A combination of experimental (kinetics, labeling) and computational studies demonstrate that in this case C-N activation occurs via an S(N)2-type displacement of amine and rule out alternative 3-center C-N oxidative addition or Hofmann elimination processes.     

Vapor and liquid phase detection of cyanide on a microchip

A capillary electrophoresis microchip is used to selectively and sensitively monitor cyanide levels in both vapor (HCN((g))) and aqueous (NaCN in drinking water) phases. Laser-induced fluorescence detection is applied using a violet diode laser to monitor the fluorescent isoindole derivative formed by the reaction of cyanide with 2,3-naphthalenedicarboxaldehyde (NDA) and taurine. Air sampling of hydrogen cyanide is achieved using a miniature impinger (2 mL), giving collection efficiencies as high as 79% for a sampling rate of 1.0 L/min and a 10 s sampling time (relative standard deviation RSD: 2.7% for n = 5). Following the addition of NDA and taurine to either the vapor phase impinger sample or an aqueous drinking water sample, the NDA/cyanide derivative can be detected in just over 40 s on the microchip, giving a detection limit of 0.56 microg/L and a linear dynamic range from 0.56 microg/L-2.4 mg/L. The detection limit for hydrogen cyanide in air was determined to be 2.3 ppb (mole%). On-chip derivatization of cyanide by NDA was successful, although a 50% decrease in signal intensity was observed due to insufficient time for completion of the reaction on the microchip. A number of different interferents were examined, and only iron(II) and chlorine showed any interference due to their capability for masking the presence of cyanide by reacting with free cyanide in solution.