Showing papers on "Thiocyanate published in 2004"

A Binary Ionic Liquid Electrolyte to Achieve ≥7% Power Conversion Efficiencies in Dye-Sensitized Solar Cells

Abstract: For the first time ≥7% power conversion efficiencies under AM 1.5 sunlight have been acheived for photovoltaic devices with a binary ionic liquid electrolyte composed of 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium thiocyanate.

Relative potencies and additivity of perchlorate, thiocyanate, nitrate, and iodide on the inhibition of radioactive iodide uptake by the human sodium iodide symporter.

Abstract: The presence of perchlorate (ClO(4) (-)) in some U.S. drinking water supplies has raised concern about potential adverse thyroidal health effects, because ClO(4) (-) is known to competitively inhibit iodide uptake at the sodium iodide symporter (NIS). Humans are nutritionally and environmentally exposed to other competitive inhibitors of iodide uptake, including thiocyanate (SCN(-)) and nitrate (NO(3) (-)). The joint inhibiting effects of these three anions was studied by exposing Chinese hamster ovary cells stably expressing human NIS to varying concentrations of each anion separately, and in combination, and conducting measurements of (125)I(-) uptake. The entire data set was fit to a single Hill equation using maximum likelihood. The relative potency of ClO(4) (-) to inhibit (125)I(-) uptake at the NIS was found to be 15, 30 and 240 times that of SCN(-), I(-), and NO(3) (-) respectively on a molar concentration basis, with no evidence of synergism. These results are consistent with a common mode of action by these anions of simple competitive interaction, in which a concentration of any one of ClO(4) (-) SCN(-), and NO(3) (-), occurring either individually or as part of a mixture of the three anions, is indistinguishable from a concentration or dilution of either one of the remaining two ions in inhibiting iodine uptake at the NIS.

Crystal structure and magnetic interactions in nickel(II) dibridged complexes formed by two azide groups or by both phenolate oxygen-azide, -thiocyanate, -carboxylate, or -cyanate groups.

Abstract: Tridentate/tetradentate Schiff base ligands L1 and L2, derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L1)(μ1,1-N3)Ni(L1)(N3)(OH2)]·H2O (1), {[Ni(L1)(μ1,1-NCS)Ni(L1)(NCS)(OH2)][Ni(L1)(μ-CH3COO)Ni(L1)( NCS) (OH2)]} (2) {[2A][2B]}, [Ni(L1)(μ1,1-NCO)Ni(L1)(NCO)(OH2)]·H2O (3), and [Ni(L2-OMe)(μ1,1-N3)(N3)]2 (4), where L1 = Me2N(CH2)2NCHC6H3(O-)(OCH3) and L2 = Me2N(CH2)2NCHC6H3N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a μ1,1 mode and μ2-phenolate oxygen ion for 1−3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic sus...

End-to-end single cyanato and thiocyanato bridged Cu(II) polymers with a new tridentate Schiff base ligand: Crystal structure and magnetic properties

Abstract: A new tridentate Schiff base ligand HL (L = C14H19N2O), derived from the condensation of benzoylacetone and 2-dimethylaminoethylamine in a 1 ∶ 1 ratio, reacts with copper(II) acetate and cyanate, thiocyanate or azide, to give rise to several end-to-end polymeric complexes of formulae [CuL(µ1,3-NCO)]n1, [CuL(µ1,3-NCS)]n2 and the complex 3 has two crystallographically independent units of formula [CuL(N3)] in the asymmetric unit cell. Complex 3 exists in dimeric form rather than as a polymeric chain. Compound 1 is the first report of a singly end-to-end cyanate bridged polymeric chain of Cu(II) with a Schiff base as a co-ligand. There are many examples of double NCS bridged polymeric chains, but fewer singly bridged ones such as compound 2. We have characterized these complexes by analytical, spectroscopic, structural and variable temperature magnetic susceptibility measurements. The coordination geometry around the Cu(II) centers is distorted square pyramidal for 1 and 2 and square planar for complex 3. The magnetic susceptibility data show slight antiferromagnetic coupling for the polymers having J values −0.19 and −0.57 cm−1 for complexes 1 and 2 respectively. The low values of J are consistent with the equatorial–axial disposition of the bridges in the polymers.

Anaerobic growth of the haloalkaliphilic denitrifying sulfur-oxidizing bacterium Thialkalivibrio thiocyanodenitrificans sp. nov. with thiocyanate

Abstract: Two strains of obligate chemolithoautotrophic sulfur-oxidizing bacteria were isolated from soda-lake sediments by enrichment culture with thiocyanate and nitrate at pH 9.9. The isolates were capable of growth with thiocyanate or thiosulfate as electron donor, either aerobically or anaerobically, and with nitrate or nitrite as electron acceptor. Cyanate was identified as an intermediate of thiocyanate oxidation, while sulfate, ammonia and dinitrogen gas were the final products. The anaerobic growth on thiocyanate plus nitrate was much slower (mu(max)=0.006 h(-1)) than on thiosulfate plus nitrate (mu(max)=0.02 h(-1)), while growth yields were similar (4.8 and 5.1 g protein mol(-1), respectively). On the basis of their phenotypic and genetic properties, strains ARhD 1(T) and ARhD 2 are described as a novel species of the genus Thialkalivibrio, with the highest similarity to Thialkalivibrio denitrificans. The name Thialkalivibrio thiocyanodenitrificans sp. nov. is proposed for this novel species.

Accumulation of cyanide and thiocyanate in haemodialysis patients

Abstract: Background. Cyanide is a toxic agent, and its detoxification product, thiocyanate, may be a major pathogenetic substance in uraemia. Recent studies examining the myeloperoxidase(MPO)/thiocyanate system have suggested a link between thiocyanate and atherosclerosis. However, inaccuracies in conventional assays for cyanide and thiocyanate have limited the understanding of their metabolism in haemodialysis (HD) patients. Methods. We used high-performance liquid chromatography to measure cyanide in erythrocytes and thiocyanate in plasma in 43 HD patients and in a group of 46 healthy controls that included 15 current smokers. To clarify the metabolic conversion of cyanide to thiocyanate in uraemic patients, we also measured cysteine and sulfate. We then used stepwise regression analysis to analyse factors that determine erythrocyte cyanide and plasma thiocyanate. Results. Mean cyanide and thiocyanate were significantly greater in HD patients than in non-smoking controls. However, cyanide was far below lethal concentrations in dialysis patients. Thiocyanate was six to seven times greater in HD patients than in non-smoking controls, and decreases in thiocyanate following dialysis were only 19.3±3.5%. Multiple regression analysis showed a positive correlation between cyanide and thiocyanate in controls, but a negative correlation in HD patients. In patients, an inverse relationship between thiocyanate and BUN was also observed. Conclusions. The elevation of thiocyanate in patients undergoing dialysis probably is secondary to both limited efficiency of HD and deranged metabolism of cyanide and thiocyanate. Because thiocyanate is a preferred substrate for MPO, it may play a role in uraemic complications including cardiovascular events.

New Solvents for Cellulose. II. Ethylenediamine/Thiocyanate Salt System

Abstract: The ethylenediamine/thiocyanate salt system was found to be a new solvent for cellulose. The solubility, dissolution behavior, solution properties, and cellulose recovered from the solutions were investigated. The dissolution took place at room temperature, and the maximum solubility achieved was 16 % (w/w) for cellulose of DP210 in the ethylenediamine/sodium thiocyanate 54/46 (w/w). The dependence of cellulose solubility on DP is also described. Tracing the dissolution behavior of the cellulose by CP/MAS 13C NMR measurements revealed the polymorphic conversion of cellulose I to III to amorphous structure during the dissolution process. The cellulose dissolved was stable for 30 days storage at room temperature. Microscopic observations and steady-shear viscosity measurements of the solutions indicated mesophase formation of cellulose in the ethylenediamine/sodium thiocyanate system. This anisotrpoic phase appeared from ca. 10 % (w/w) cellulose with DP210 and greatly depended on the cellulose concentrations. Coagulation studies disclosed that cellulose II and amorphous cellulose were recovered from the cellulose/ethylenediamine/thiocyanate salt solutions when water and alcohol were used as a coagulant, respectively. It was suggested that this solvent system has high potential for cellulosic fiber and film formations.

Reactive sulfur species: aqueous chemistry of sulfenyl thiocyanates.

Abstract: Sulfenyl thiocyanate (RSSCN) derivatives of penicillamine (PENSCN) and glutathione (GSSCN) have been synthesized in situ at pH = 0 from equilibrium mixtures that consists of hypothiocyanous acid (HOSCN), thiocyanogen ((SCN)2), and trithiocyanate ((SCN)3-). The electrophilic thiocyanating agent N-thiocyanatosuccinimide (NTS) also reacts with PEN and GSH to yield the corresponding RSSCN derivatives. PENSCN and GSSCN were characterized by NMR, ES-MS, and IR spectroscopy. While stable at pH = 0, at higher pH the RSSCN derivatives decompose to give products that are consistent with hydrolysis and formation of reactive sulfenic acids.

Physicochemical features of rhodanese: A review

Abstract: Rhodanese is a multifunctional, mitochondrial, sulphur transferase that catalyses the detoxification of cyanide by sulphuration in a double displacement (ping pong) mechanistic reaction. It is widely distributed occurring in varieties of plants and animals, where it activity is modulated by a number of factors including differences in species, organs, sex, age and diet. The enzyme is a single polypeptide chain of 289 amino acids with molecular weight of up to 37,000. The active site of rhodanese contains a tryptophanyl residue in close proximity with an essential sulphahydryl group. Many methods for assaying rhodanese have been reported, the most prominent being the one based on the colorimetric estimation of thiocyanate formed from the reaction of cyanide and thiosulphate, catalysed by rhodanese.

A new lead(II) complex of 2,2′-bipyridine, acetate and thiocyanate ligands: synthesis, characterization and crystal structure of [Pb(bpy)(NCS)(CH3COO)] n

Abstract: A new lead(II) complex of 2,2′-bipyridine (bpy), acetate and thiocyanate has been synthesized and characterized by C H N elemental analysis, IR, 1H NMR, 13C NMR and 207Pb NMR spectroscopy. The structure of [Pb(bpy)(NCS)(CH3COO)] n was confirmed by X-ray crystallography. Single-crystal X-ray data show the complex to be a one-dimensional polymer as a result of thiocyanate ligand bridging with the basic repeating monomeric units [Pb(bpy)(NCS)(CH3COO)]. The Pb atom has an unsymmetrical five-coordinate geometry, being coordinated by two nitrogen atoms of bpy, two oxygen atoms of the acetate and one nitrogen atom of the thiocyanate anion. The arrangement of the bpy, acetate and nitrate ligands exhibits a coordination gap around the Pb(II) ion, occupied possibly by a stereoactive lone pair of electrons on lead(II), and the coordination around the lead atoms is hemidirected. There are π–π stacking interactions between the parallel aromatic rings.

Amperometric Sensor Used for Determination of Thiocyanate with a Silver Nanoparticles Modified Electrode

Abstract: A novel electrode modified with silver nanoparticles was fabricated. It is found that the reducibility of silver nanoparticles is higher than for bulk silver by comparing a silver nanoparticles modified electrode with a silver micro-disk electrode. When SCN- was added, a new oxidation peak occurred and the anodic peak current of silver nanoparticles decreased. The new anodic peak current is proportional to the thiocyanate concentration in the range of 5.0×10-7~4.0×10-4 mol/L in pH 6.0 NaH2PO4-Na2HPO4 buffer solutions (PBS). The detection limit (S/N=3) is 4×10-8 mol/L. This method has been applied to the determination of saliva (smoker and non-smoker).

Determination of Thiocyanate within Physiological Fluids and Environmental Samples: Current Practice and Future Trends

Abstract: As the toxicological and physiological importance of thiocyanate has become more and more evident during the past 20 years, there has been an increasing interest in this anion. Thiocyanate is a detoxication product of cyanide and its content in human saliva is considered as a biomarker for identification of nonsmokers and smokers. Chronically elevated levels of thiocyanate in body fluids are known to be toxic and its relation to local goiter, vertigo, or unconciousness has been pointed out. On the other hand, thiocyanate-containing waste discharged into rivers is harmful to aquatic life due to its degradation to cyanide in the presence of oxidants. Therefore, precise knowledge of the thiocyanate content in biological fluids and environmental samples is mandatory. An overview of the existing analytical methodologies for thiocyanate is presented and their advantages and limitations are highlighted. This review is intended not only to provide a comparison of the different methods employed, but also to make i...

Anion complexation by glycocluster thioureamethyl cavitands: novel ESI-MS-based methods for the determination of Ka values.

Abstract: A series of saccharide-thiourea functionalized cavitands was prepared in good yields (72-86 %) by reaction of a tetrakis(aminomethyl) cavitand with the thiocyanate derivatives of acetylated glucose, galactose, and cellobiose. The anion complexation behavior of the acetylated and deacetylated glycocluster thioureamethyl cavitands was studied with electrospray ionization mass spectrometry (ESI-MS) in acetonitrile and in a 1:1 acetonitrile/water mixture, respectively. All compounds show a preference for Cl-. A linear relationship was found between the square root of the intensity and the concentration of the formed host-guest complex. Based on this relationship, novel methods have been developed to determine Ka values, by means of direct titration and competition experiments.

Role of thiocyanate, bromide and hypobromous acid in hydrogen peroxide-induced apoptosis.

Abstract: We have previously reported that H2O2-induced apoptosis in HL-60 human leukemia cells takes place in the presence of chloride, requires myeloperoxidase (MPO), and occurs through oxidative reactions involving hypochlorous acid and chloramines. We now report that when chloride is replaced by the pseudohalide thiocyanate, there is little or no H2O2-induced apoptosis. Furthermore, thiocyanate inhibits H2O2-induced apoptosis when chloride is present at physiological concentrations, and this occurs at thiocyanate concentrations that are present in human serum and saliva. In contrast, bromide can substitute for chloride in H2O2-induced apoptosis, but results in a lower percent of the cells induced into apoptosis. Hypobromous acid is likely a short-lived intermediate in this H2O2/MPO/bromide apoptosis, and reagent hypobromous acid and bromamines induce apoptosis in HL-60 cells. We conclude that the physiologic concentrations of thiocyanate found in human plasma could modulate the cytototoxicity of H2O2 and its re...

Electrical Conductances and Viscosities of Tetrabutylammonium Thiocyanate in Acetonitrile in the Temperature Range 25–45 °C

Abstract: The electrical conductances and viscosities of the solutions of tetrabutylammonium thiocyanate (Bu 4 NCNS) in acetonitrile have been reported at 25, 30, 35, 40 and 45°C. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance (A 0 ), the association constant (K A ) and the association diameter (R). The viscosity data have been analyzed by the Jones-Dole equation for the associated electrolytes to evaluate the viscosity B-coefficients of the electrolyte. These data have also been analyzed by the transition-state treatment to obtain the contribution of the solutes to the free energy of activation for viscous flow of the solution. The ionic contributions to the limiting molar conductance (A 0 ), the viscosity B-coefficient and the free energy of activation for viscous flow have been estimated using the "reference electrolyte" tetrabutylammonium tetraphenylborate (Bu 4 NBPh 4 ). Slight ionic association was always found for this salt in this solvent medium. The tetrabutylammonium ion is found to be unsolvated whereas the thiocyanate ion undergoes solvation in acetonitrile in the temperature range investigated here.

Biosynthetic pathways to isocyanides and isothiocyanates; precursor incorporation studies on terpene metabolites in the tropical marine sponges Amphimedon terpenensis and Axinyssa n.sp.

Abstract: The biosynthetic origins of the isocyanide and isothiocyanate functional groups in the marine sponge metabolites diisocyanoadociane (1), 9-isocyanopupukeanane (10) and 9-isothiocyanatopupukeanane (11) are probed by the use of [14C]-labelled precursor experiments. Incubation of the sponge Amphimedon terpenensis with [14C]-labelled thiocyanate resulted in radioactive diisocyanoadociane (1) in which the radiolabel is specifically associated with the isocyanide carbons. As expected, cyanide and thiocyanate were confirmed as precursors to the pupukeananes 10 and 11 in the sponge Axinyssa n.sp.; additionally these precursors labelled 2-thiocyanatoneopupukeanane (12) in this sponge. To probe whether isocyanide-isothiocyanate interconversions take place at the secondary metabolite level, the advanced precursor bisisothiocyanate 17 was supplied to A. terpenensis, but did not result in significant labelling in the natural product isocyanide 1. In contrast, in the sponge Axinyssa n.sp., feeding of [14C]-9-isocyanopupukeanane (10) resulted in isolation of radiolabelled 9-isothiocyanatopupukeanane 11, while the feeding of [14C]-11 resulted in labelled isocyanide 10. These results show conclusively that isocyanides and isothiocyanates are interconverted in the sponge Axinyssa n.sp., and confirm the central role that thiocyanate occupies in the terpene metabolism of this sponge.

Ion-Selective Electrodes for Thiocyanate Based on the Dinuclear Zinc(II) Complex of a Bis-N,O-bidentate Schiff Base

Abstract: An ion selective electrode based on the dinuclear complex formed by two zinc(II) ions and two molecules of the bis-N,O-bidentate Schiff base 2,2′-[methylenebis(4,1-phenylenenitrilomethylidyne)]bisphenol exhibits thiocyanate selectivity with a good discrimination of nitrite, nitrate, and azide. The selectivities of electrode membranes with various compositions indicate that this potentiometric selectivity is based on the formation of a 1 : 1 complex between the thiocyanate anion and the dinuclear ionophore. The 2 : 1 ratio of thiocyanate ions and the dinuclear ionophore that results from higher ratios of cationic sites and ionophore worsens the selectivity, suggesting that binding of a thiocyanate to both zinc(II) centers of the dinuclear ionophore is not favorable. Interestingly, the selectivity patterns of these electrodes differ radically from that of a highly sulfate selective electrode based on a compound reported previously to be the analogous mononuclear 1 : 1 complex of zinc(II) and the same Schiff base. It is suggested that the previously reported 1 : 1 complex with zinc(II) may indeed have been a polymer of the same elemental composition.

Precious metal recovery using thiocyanate lixiviant

Abstract: Precious metal-containing mineral material is subjected to an acidic thiocyanate leach to dissolve the precious metal as a precious metal-thiocyanate complex. A feed of the thiocyanate leach solution may include a large molar ratio of ferric iron to thiocyanate. Precious metal may be removed from pregnant thiocyanate leach solution, such as by transferring precious metal from precious metal-thiocyanate complex to precious metal-cyanide complex and then loading the precious metal-cyanide complex onto an adsorbent material. Remaining cyanide in the thiocyanate leach solution may be converted to thiocyanate for additional leaching of precious metal.

Direct Synthesis of the Novel 2-D Mixed-ligands Lead(II) Complex, Crystal Structure of [Pb(4,4′-bpy)(NO3)(SCN)]n (4,4′-bpy = 4,4′-bipyridine): (A New Polymeric Compound with Three Bridged Ligand and Inactive Lone Pair)

Abstract: A lead(II) complex with three ligands, 4,4′-bipyridine (4,4′-bpy), nitrate, and thiocyanate, has been synthesized and characterized by CHN elemental analysis, IR-, 1H-, 13C- and 207Pb NMR spectrosc...