Presence Of CN Research Articles

INFLUENCE OF CYANIDE ON REMOVAL OF COPPER ION FROM THE SOLUTION BY PHOTOCATALYTIC REDUCTION METHOD WITH TiO<sub>2</sub> SUSPENSION

The removal of Cu(II) by photoreduction method using TiO2 photocatalyst in the presence of CN- is reported. Photoreduction was carried by batch technique using UV lamp with 290-350 nm of wavelength. The research results indicate that the present of CN- ion gives different effects on the photoreduction effectiveness depends on the mole ratio of both ions. The addition of CN- less than 2 moles for each mole of Cu (II) ion can improve the photoreduction, and the photoreduction sharply goes down into very low degree when the mole number of CN- is increased up to 4, and by further enlarging the mole number into 6, the photoreduction degree remains constant. Furthermore, increasing solution pH generally leads to a decrease in the photoreduction. In the solution with pH 1, the maximal photoreduction degree is reached, while increasing pH from 1 to 9 has declined the photoreduction, and the photoreduction is totally inhibited at pH higher than 9. The effect of the solution pH is related with the speciation of Cu (II), CN- and TiO2 in the solution. Keywords: Photoreduction, copper, cyanide, TiO2 photocatalyst

Noncovalent Assembly of Picket-Fence Porphyrins on Nitrogen-Doped Carbon Nanotubes for Highly Efficient Catalysis and Biosensing

A water-insoluble picket-fence porphyrin was first assembled on nitrogen-doped multiwalled carbon nanotubes (CN(x) MWNTs) through Fe--N coordination for highly efficient catalysis and biosensing. Scanning electron micrographs, Raman spectra, X-ray photoelectron spectra, UV/Vis absorption spectra, and electrochemical impedance spectra were employed to characterize this novel nanocomposite. By using electrochemical methods on the porphyrin at low potential in neutral aqueous solution, the presence of CN(x) MWNTs led to the direct formation of a high-valent iron(IV)-porphyrin unit, which produced excellent catalytic activity toward the oxidation of sulfite ions. By using sulfite ions, a widely used versatile additive and preservative in the food and beverage industries, as a model, a highly sensitive amperometric biosensor was proposed. The biosensor showed a linear range of four orders of magnitude from 8.0x10(-7) to 4.9x10(-3) mol L(-1) and a detection limit of 3.5x10(-7) mol L(-1) due to the highly efficient catalysis of the nanocomposite. The designed platform and method had good analytical performance and could be successfully applied in the determination of sulfite ions in beverages. The direct noncovalent assembly of porphyrin on CN(x) MWNTs provided a facile way to design novel biofunctional materials for biosensing and photovoltaic devices.

Turn-on fluorescent cyanide sensor based on copper ion-modified CdTe quantum dots

A new fluorescent sensor for the sensitive and selective detection of cyanide (CN(-)) in aqueous media was developed herein. The sensing approach is based on CN(-)-modulated quenching behavior of Cu(2+) toward the photoluminescence (PL) of CdTe quantum dots (QDs). In the presence of CN(-), the PL of QDs that have been quenched by Cu(2+) was found to be efficiently recovered, which then allows the detection of CN(-) in a very simple approach. Experimental results showed that the pH of the buffer solution, concentration of copper ions, and size of CdTe QDs all influenced the response of the sensor to CN(-). Under the optimal conditions, a good linear relationship between the PL intensity and the concentration of CN(-) can be obtained in the range of 3.0 x 10(-7) to 1.2 x 10(-5) M, with a detection limit as low as 1.5 x 10(-7) M. In addition, the present fluorescent sensor possesses remarkable selectivity for cyanide over other anions, and negligible influences were observed on the cyanide detection by the coexistence of other anions or biological species (such as albumin and typical blood constituents). Therefore, we expect the proposed copper ion-modified QDs to be an efficient and reliable sensing system to monitor cyanide concentration in environmental or clinical applications.

Cubic Gyroid Frameworks in Mesostructured Metal Selenides Created from Tetrahedral Zn2+, Cd2+, and In3+ Ions and the [SbSe4]3- Precursor

We describe a new group of well-organized cubic mesostructured metal chalcogenides. They were obtained from the assembly of the tetrahedral [SbSe4]3- unit and the linking metal ions In3+, Zn2+, and Cd2+ in the presence of Cn (n = 12, 14, 16) pyridinium surfactants acting as structure-directing agents. The assembly of the cubic gyroid mesostructure is immediate upon mixing the reactants. The cubic structure, confirmed with X-ray diffraction and transmission electron microscopy, contains an infinitely extended M/Sb/Se network that defines a well-known periodic minimal surface known as the gyroid and possesses an Ia3d space group symmetry. The ion In3+ is a more versatile linking metal and can also form a hexagonal mesostructure by changing the surfactant concentration or carbon chain length. The pore−pore separations and pore sizes are a function of surfactant chain length in all cases. The cubic mesophases exhibit reversible ion-exchange properties, although the cubic symmetry cannot be retained. All meso...

A New Type of Dendritic [60]Fullerene–Metallo‐tetraphenylporphyrin Diads (M = Zn, Co)

AbstractThe synthesis of unsymmetrical malonates 19–23 terminated by a metallo‐tetraphenylporphyrin (M = ZnII, CoII, CoIII) and by Newkome‐type amide dendrons of generation two and three is reported. Cyclopropanation of C60 with the second‐generation dendrons 20 and 21 leads to the formation of fullerene monoadducts 24 and 25, representing a new type of dendritic diads. The establishment of Co in the oxidation sates of +II and +III was achieved by the treatment with Na2S2O4 or with O2 in the presence of CN– and SCN–, respectively, leading to the paramagnetic complex 26 and the diamagnetic axially coordinated complexes 27. Deprotection of the tert‐butyl groups terminating the dendritic branch of the diads 24 and 25 generates the corresponding water‐soluble systems 28 and 29. Due to their amphiphilic character micellar aggregates are formed in water. DOSY NMR measurements showed that the aggregates consisting of 28 have an average diameter of approximately 7 nm in a buffered D2O solution (pH = 7.2). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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 pH⩾8, 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.

Synthese, Kristallstruktur und spektroskopische Untersuchungen von Ba5(BO3)3CN

AbstractSynthesis, Crystal Structure, and Spectroscopic Investigations of Ba5(BO3)3CNBarium borate cyanide Ba5(BO3)3CN was synthesized at 1450 °C as coarsely crystalline colorless to pale yellow crystals by the reaction of BaCO3 with BN, barium and tungsten in tungsten crucibles using a radiofrequency furnace. The structure was solved by single‐crystal X‐ray diffractometry (Ba5(BO3)3CN, Z = 4, C2221, a = 1045.3(2), b = 1479.6(3), c = 798.9(2) pm, R1 = 0.0240, 1847 independent reflections, 91 refined parameters). Besides Ba2+ there are trigonal BO33− ions (B‐O 137 – 140 pm) and CN− ions (C‐N 114(2) pm). The presence of CN− ions unequivocally has been determined by observation of a sharp resonance at 2075 cm−1 in the single‐crystal raman spectrum.

A Heterobimetallic Ruthenium(II)−Copper(II) Donor−Acceptor Complex as a Chemodosimetric Ensemble for Selective Cyanide Detection

A trinuclear heterobimetallic Ru(II)-Cu(II) donor-acceptor complex, [Ru(II)((t)Bubpy)(CN)(4)-[Cu(II)(dien)](2)](ClO(4))(2) ((t)Bubpy = 4,4'-di-tert-butyl-2,2'-bipyridine; dien = diethylenetriamine) (1), has been synthesized and successfully used as an chemodosimetric ensemble for the specific detection of cyanide in aqueous DMF. X-ray crystallography, solid and solution IR spectroscopy, and conductivity measurements reveal that complex 1 is a one-dimensional polymer in the crystalline state and dissociates into its [Ru(II)((t)Bubpy)(CN)(2)[(CN)Cu(II)(dien)L](2)](2+) (L = solvent) monomeric units in polar solvents. The MLCT transition and luminescence properties of the solvatochromic [Ru(II)((t)Bubpy)(CN)(4)](2)(-) donor are perturbed by the coordination of two Cu(II) acceptors but restored in the presence of CN(-). Spectroscopic and mass spectrometric studies confirm the cleavage of the cyano bridge between Ru(II) and Cu(II) of the chemodosimetric ensemble after the binding of cyanide to the Cu(II) centers. The overall binding constant, K(B), between 1 and CN(-) is measured to be (7.39 +/- 0.23) x 10(6) M(-2). A detection limit of 1.2 microM (0.03 ppm) of CN(-) in aqueous DMF (pH 7.4) is achievable. Thermodynamic evaluation shows that the analyte specificity of chemodosimeter 1 is attributable to the relative stability of the donor-acceptor complex to that of adducts formed between the acceptor metal center and the analytes.

Cyanide inhibits the Na+/Ca2+ exchanger in isolated cardiac pacemaker cells of the cane toad

The effects of the metabolic inhibition on the activity of the Na+/Ca2+ exchanger (NCX) were studied in single isolated pacemaker cells from the cane toad. Ca2+ influx on NCX (reverse mode) was estimated by measuring the increase in intracellular calcium concentration ([Ca2+]i) in response to extracellular Na+-free solution. After application of 2 mM sodium cyanide for 3-5 min, the peak [Ca2+]i in Na+-free solution was significantly decreased from 377+/-42 nM to 260+/-46 nM, suggesting inhibition of NCX. To study Ca2+ efflux on NCX (forward mode), we recorded the tail currents on repolarization which were abolished by Ni2+ and by Na+-free solution. Cyanide decreased the amplitude of tail currents by 36+/-3%. To investigate the intrinsic properties of NCX during the metabolic inhibition, we used rapid application of caffeine to trigger sarcoplasmic reticulum Ca2+ release, which then stimulates NCX current (I(NCX) ). Both the caffeine-induced peak [Ca2+]i and the peak I(NCX) were reduced by cyanide exposure. When I(NCX) was plotted against [Ca2+], the slope of the decay phase was decreased in the presence of CN- to 44+/-8% of control, indicating that for a given [Ca2+]i there was less I(NCX) produced. These results show that cyanide (CN-) inhibits NCX activity at least partly through changes in the intrinsic properties of NCX. The inhibition of NCX probably contributes to the slower firing rate of pacemaker cells in CN-.

Selective response mechanism of a platinum disk electrode modified with polyacrylamide membrane conjugated with gallium(III) phthalocyaninate

A non-plasticized polyacrylamide polymer (PAA) coupled with (phthalocyaninato) gallium(III) ([Ga(pc)] +), PAA–[Ga(pc)], was first synthesized, and the potentiometric response behavior of this PAA–[Ga(pc)] modified platinum electrode to certain ions was examined in the non-aqueous solvents acetonitrile (AN), dimethylacetamide (DMA), and N-methylpyrrolidinone (NMP). The electrode showed a Nernstian or near-Nernstian response to CN − and F − in AN, DMA, and NMP, but it showed a non-thermodynamic response to Cl −and Br − in all the above solvents. Both spectrophotometric and cyclic voltammetric methods were used to investigation the reaction of [Ga(pc)] + with the ions in the solvents. The results revealed that the special selective response phenomena were due to the complex formation reactions of the ions with [Ga(pc)] +. The reaction mechanisms were determined on the basis of the shift of the maximum absorption peaks, the appearance of the new peaks on UV–vis spectra for [Ga(pc)] + in the presence of CN − and F − and the clear difference in the redox voltammogram for [Ga(pc)] + at the platinum electrode between the addition of F − and Br − in DMA. There were no obvious differences between the three solvents in terms of their influence on the complexing. It was concluded that the electrode might have applications in obtaining the solubility product of NaF in AN.

The effect of mitochondrial inhibitors on membrane currents in isolated neonatal rat carotid body type I cells

Inhibitors of mitochondrial energy metabolism have long been known to be potent stimulants of the carotid body, yet their mechanism of action remains obscure. We have therefore investigated the effects of rotenone, myxothiazol, antimycin A, cyanide (CN(-)) and oligomycin on isolated carotid body type I cells. All five compounds caused a rapid rise in intracellular Ca(2+), which was inhibited on removal of extracellular Ca(2+). Under current clamp conditions rotenone and CN(-) caused a rapid membrane depolarization and elevation of [Ca(2+)](i). Voltage clamping cells to -70 mV substantially attenuated this rise in [Ca(2+)](i). Rotenone, cyanide, myxothiazol and oligomycin significantly inhibited resting background K(+) currents. Thus rotenone, myxothiazol, cyanide and oligomycin mimic the effects of hypoxia in that they all inhibit background K(+) current leading to membrane depolarization and voltage-gated calcium entry. Hypoxia, however, failed to have any additional effect upon membrane currents in the presence of CN(-) or rotenone or the mitochondrial uncoupler p-trifluoromethoxyphenyl hydrazone (FCCP). Thus not only do mitochondrial inhibitors mimic the effects of hypoxia, but they also abolish oxygen sensitivity. These observations suggest that there is a close link between oxygen sensing and mitochondrial function in type I cells. Mechanisms that could account for this link and the actions of mitochondrial inhibitors are discussed.

Kinetic and thermodynamic studies on the cyanation reactions and base-on/base-off equilibria of alkyl-13-epicobalamins

Ligand substitution equilibria of two different 13-epicobalamins (X-13-epiCbl, X = NCCH2 and CN−) with cyanide have been studied. It was found that CN− substitutes the 5,6-dimethylbenzimidazole (DMBz) moiety in the α-position to form X(CN)Cbl-13epi, which for X = NCCH2 in the presence of CN− subsequently gives (CN)2Cbl-13epi. The kinetics of the displacement of DMBz by CN− showed saturation behaviour at high cyanide concentration and the limiting rate constants are characterized by the activation parameters: X = NCCH2, ΔH≠ = 83 ± 1 kJ mol−1, ΔS≠ = +77 ± 4 J K−1 mol−1, ΔV≠ = +13.3 ± 1.0 cm3 mol−1; X = CN−, ΔH≠ = 106 ± 1 kJ mol−1, ΔS≠ = +82 ± 4 J K−1 mol−1 and ΔV≠ = +14.8 ± 0.5 cm3 mol−1. These parameters are interpreted in terms of a limiting D mechanism. The rate constants for the displacement of DMBz in the case of the 13-epicobalamins were found to be slower than those obtained in the case of the analogous alkylcobalamins, and consequently, the thermodynamic equilibrium constants for the 13-epicobalamins were found to be smaller than those obtained in the case of the alkylcobalmins. This clearly shows the effect of the epimerization of the e-side chain attached to the C-13 of the corrin ring on the rate and equilibrium constants for these ligand displacement reactions.

Hydroxylamine reductase activity of the hybrid cluster protein from Escherichia coli.

The hybrid cluster protein (HCP; formerly termed the prismane protein) has been extensively studied due to its unique spectroscopic properties. Although the structural and spectroscopic characteristics are well defined, its enzymatic function, up to this point, has remained unidentified. While it was proposed that HCP acts in some step of nitrogen metabolism, a specific role for this enzyme remained unknown. Recent studies of HCP purified from Escherichia coli have identified a novel hydroxylamine reductase activity. These data reveal the ability of HCP to reduce hydroxylamine in vitro to form NH(3) and H(2)O. Further biochemical analyses were completed in order to determine the effects of various electron donors, different pH levels, and the presence of CN(-) on in vitro hydroxylamine reduction.

ChemInform Abstract: The Bio-organometallic Chemistry of Active Site Iron in Hydrogenases

Abstract The recent X-ray crystal structure determinations of several hydrogenase enzymes have engaged the organometallic community owing to the presence of CN − and CO ligands bound to iron in the active sites. This review focuses primarily on the structural features of these metalloproteins and discusses synthetic efforts to develop small molecule models of the active sites. Specific attention is given to the use of infrared spectroscopy as an additional tool to probe different enzyme states. In addition, structurally dissimilar complexes which show some ability to facilitate either dihydrogen uptake or production, are reviewed as possible functional models. Insights from earlier work with metal hydride chemistry and recent theoretical studies are discussed in terms of functional mechanistic proposals.

Chemical properties of the Pd4(dppm)4(H)2(2+) cluster and the homogeneous electrocatalytical behavior of hydrogen evolution and formate decomposition.

Two new reductive electrochemical (CO2 + H2O + 2e-; HCO2H + 2e-) and two new chemical methods (Al(CH3)3 + proton donor; NaO2CH) to prepare the title compound from Pd2(dppm)2Cl2 are reported. For the latter method, an intermediate species formulated as Pd2(dppm)4(O2CH)2(2+) is identified spectroscopically (1H NMR, 31P NMR, IR, and FAB-MS). Limited stability of the title compound in the presence of Cl- and Br- as counteranions is noticed and is due to sensitivity of the cluster toward nucleophilic attack of the halide ions. This result is corroborated by the rapid decomposition of these clusters in the presence of CN- to form the binuclear species Pd2(dppm)2(CN)4 and by the preparation of the stable salts [Pd4(dppm)4(H)2](X)2(X- = BF4-, PF6-, BPh4-). Upon a two-electron electrochemical reduction of this cluster to the neutral species (E1/2 = -1.42 V vs SCE in DMF) in the presence of 1 equiv of HCO2H, a highly reactive species formulated as [Pd4(dppm)4(H)3]+ is generated and characterized by 1H NMR, 31P NMR, and cyclic voltammetry. Subsequent addition of H+ (via RCO2H; R = H, CH3, CF3, C6H5) under the same reducing conditions, induces the homogeneous catalysis of H2 evolution. The turnover number is found to be 134 in 2 h, with no evidence for catalyst decomposition. This same species also exhibits a one-electron oxidation process (E1/2 = -0.61 V vs SCE in DMF) that induces the catalytical decomposition of formate (HCO2- --> CO2 + 1/2H2 + 1e-). This double catalysis from the same cluster intermediate is unprecedented.

Cyanide inhibition of chloride conductance across toad skin.

The effect of cyanide (CN(-)) on voltage-activated or cAMP-induced passive chloride conductance (G(Cl)) was analyzed in isolated toad skin. Comparatively low concentrations of CN(-) inhibited G(Cl) almost completely and fully reversibly, regardless of whether it was applied from the mucosal or serosal side. The IC(50) was 180 +/- 12 microm for voltage-activated G(Cl) and 305 +/- 30 microm for the cAMP-inducted conductance. At [CN] <100 microm, the initial inhibition frequently declined partly in the continuous presence of CN(-). Inhibition was independent of the presence of Ca(2+). Inhibition was stronger at more alkaline pH, which suggests that dissociated CN(-) is the effective inhibitor. The onset of the inhibition of voltage-activated or cAMP-induced G(Cl) by CN(-) occurred with half-times of 34 +/- 10 sec, whereas reversibility upon washout was twice as fast (18 +/- 7 sec). If [CN(-)] <200 microm was applied under inactivating conditions (serosa -30 mV), the reduction of G(Cl) was stronger upon subsequent voltage-activation than under steady-state activated conditions. This effect was essentially complete less than 30 sec after apical addition of CN(-), but G(t) recovered thereafter partially in the continuous presence of CN(-). Dinitrophenol inhibited G(Cl) similarly, while omission of oxygen did not affect it. These observations, as well as the time course of inhibition and the full reversibility, suggest that interference of CN(-) with oxidative phosphorylation and subsequent metabolic depletion is not the reason for the inhibition of G(Cl). We propose that the inhibition is directly on G(Cl), presumably by competition with Cl(-) at a rate-limiting site in the pathway. Location and molecular nature of this site remain to be identified.

Carbon nitride thin films and nanopowders produced by CO2laser pyrolysis

Nanocrystalline CNx particles and thin films were produced in a flow reactor system by the CO2 laser pyrolysis of sensitised NH3–N2O–C2 H2reactant gas mixtures. Depending on the substrate nature (silicon or quartz) the SEM and TED analysis of the CNx thin films revealed specific nucleation and growth morphologies of crystallites, resembling the β-C3 N4 phase. In the case of C3 N4 nanopowder synthesis, the relative concentration of the sensitisers (SF6 /C2 H4 ) was varied to minimise SF6 decomposition. The majority of the data obtained from powder analysis (XRD, XPS, and ir transmission measurements) suggests the presence of CN bonded phases and the formation of α-and β-C3 N4 structures.

Methylcyclopentadienyl-vanadium(III) complexes

[(MeCp)VCl 2(PEt 3) 2] ( 1) and [(MeCp) 2VCl] ( 4) (MeCp=η 5-C 5H 4CH 3) have been obtained from the reaction between VCl 3 and NaMeCp in THF in the presence ( 1) and absence ( 4), respectively, of PEt 3. The reaction of VCl 3 and NaMeCp in the presence of CN t-Bu yielded (impure) [(MeCp)VCl 2(CN t-Bu) 2] ( 3) and, as a by-product, [(MeCp) 2V(CN t-Bu) 2][VCl 4(THF) 2] ( 2). The crystal and molecular structures of 1, 2 and 4 have been determined.

Cyclopentadienyl dithiocarbamate and dithiophosphate molybdenum and tungsten complexes

Reactions of [MCp*Cl 4] (M=Mo, W; Cp*=η 5-C 5Me 5) with salts of the N, N-diethyldithiocarbamate [Et 2dtc] − and O, O′-diethyldithiophosphate [Et 2dtp] − anions yield the paramagnetic metal(V) complexes [MCp*Cl 3(Et 2dtc)] (M=Mo, W) and [MCp*Cl 3(Et 2dtp)] (M=Mo, W), respectively. Hydrolytic oxidation of both dithiocarbamate–molybdenum complexes with aqueous hydrogen peroxide leads to η 2-coordinated peroxo compounds [MoCp*Cl(O–O)O], which were also obtained from [MoCp*Cl 4]. The related complexes [MCp′Cl(O–O)O] (M=Mo, Cp′=η 5-C 5H 5; M=W, Cp′=η 5-C 5Me 5) were isolated in a similar way. Reduction of a THF solution of [MoCp*Cl 4] with one equivalent of 10% Na/Hg followed by the addition of one equivalent of ammonium dithiophosphate gives [MoCp*Cl 2(Et 2dtp)] which was also obtained via the reaction of [MoCp*Cl 3(Et 2dtp)] with MeMgCl, whereas reduction with three equivalents of Na/Hg in the presence of CN t Bu leads to the molybdenum(II) complex [MoCp*(Et 2dtp)(CN t Bu) 2] in high yield. All these compounds were characterized by elemental analysis, IR, 1H- and 13C-NMR spectroscopy, magnetic susceptibility measurements and the molecular structures of [Mo(η 5-C 5H 5)Cl(O–O)O] and [Mo(η 5–C 5Me 5)Cl 3{η 2-S 2P(OEt) 2}] were determined by X-ray diffraction studies.

AFM characterization of the structure of Au-colloid monolayers and their chemical etching

Modification of a glass support with triethoxy propylaminosilane yields an active interface for the assembly of Au colloids. The colloids are imaged by AFM using a low applied load (0.5–0.7 nN). The lateral Au-colloid dimensions, 33±3 nm, deviate from the particle dimensions determined by TEM (19±2 nm) and absorption spectroscopy (15 nm). This deviation is attributed to the intrinsic curvature of the AFM tip. Application of higher loads on the tip (3 nN) results in the sweeping of Au colloids from the monolayer. The Au colloid monolayer is etched in the presence of CN −. The etching proceeds by the initial coincidental etching of Au particles followed by the kinetically favored etching of particles at the edges of the etched domains. This provides means for the micro machining and the chemical manipulation of Au colloids of controlled spatial arrangement.