Showing papers on "Thiocyanate published in 2001"
TL;DR: A procedure was developed which works for both the synthesis of homonuclear 11 and the star-shaped heteronuclear clusters and the structures of all new compounds were determined unequivocally by single-crystal X-ray analyses.
Abstract: A simple template-mediated route, starting from triethalolamine 1, sodium hydride or caesium carbonate, and iron(III) chloride led to the six- and eight-membered iron coronates [Na c [Fe6[N(CH2CH2O)3]6]]+ (2) and [Cs c (Fe8[N(CH2CH2O)3]8]]+ (3). In the reaction of N-methyldiethanolamine 4 (H2L1) or N-(2,5-dimethylbenzyl)iminodiethanol 6 (H2L2) with calcium hydride followed by addition of a solution of iron(III) chloride, the neutral unoccupied coronands [Fe6Cl6(L1)6] (5) and [Fe6Cl6(L2)6] (7) were formed. Subsequent exchange of the chloride ions of 7 by bromide or thiocyanate ions afforded the ferric wheels [Fe6Br6(L2)6] (8) or [Fe6(NCS)6(L2)6] (9), respectively. Titration experiments of solutions of dianion (L1)2- with iron(III) chloride in THF revealed interesting mechanistic details about the self-assembling process leading to 5. At an iron/ligand ratio of 1:1.5 star-shaped tetranuclear [Fe[Fe(L1)2]3] (11) was isolated. However, at an iron/ligand ratio of 1:2, complex 11 was transformed into the ferric wheel 5. It was shown, that the interconversion of 5 and 11 is reversible. Based on the mechanistic studies, a procedure was developed which works for both the synthesis of homonuclear 11 and the star-shaped heteronuclear clusters [Cr[Fe(L1)2]3] (12) and [Al[Fe(L1)2]3] (13). The structures of all new compounds were determined unequivocally by single-crystal X-ray analyses.
181 citations
TL;DR: The results support a model for a single common binding site for halides and thiocyanate as substrates or as inhibitors near the delta-meso carbon of the porphyrin ring in myeloperoxidase.
Abstract: The 1.9 A X-ray crystal structure of human myeloperoxidase complexed with cyanide (R = 0.175, Rfree = 0.215) indicates that cyanide binds to the heme iron with a bent Fe−C−N angle of ∼157°, and binding is accompanied by movement of the iron atom by 0.2 A into the porphyrin plane. The bent orientation of the cyanide allows the formation of three hydrogen bonds between its nitrogen atom and the distal histidine as well as two water molecules in the distal cavity. The 1.85 A X-ray crystal structure of an inhibitory complex with thiocyanate (R = 0.178, Rfree = 0.210) indicates replacement of chloride at a proximal helix halide binding site in addition to binding in the distal cavity in an orientation parallel with the heme. The thiocyanate replaces two water molecules in the distal cavity and is hydrogen bonded to Gln 91. The 1.9 A structures of the complexes formed by bromide (R = 0.215, Rfree = 0.270) and thiocyanate (R = 0.198, Rfree = 0.224) with the cyanide complex of myeloperoxidase show how the presenc...
131 citations
TL;DR: This work presents a first direct proof of a “cyanate pathway” in pure cultures of thiocyanate-degrading bacteria and demonstrates that cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thIOCyanate.
Abstract: Three kinds of alkaliphilic bacteria able to utilize thiocyanate (CNS-) at pH 10 were found in highly alkaline soda lake sediments and soda soils. The first group included obligate heterotrophs that utilized thiocyanate as a nitrogen source while growing at pH 10 with acetate as carbon and energy sources. Most of the heterotrophic strains were able to oxidize sulfide and thiosulfate to tetrathionate. The second group included obligately autotrophic sulfur-oxidizing alkaliphiles which utilized thiocyanate nitrogen during growth with thiosulfate as the energy source. Genetic analysis demonstrated that both the heterotrophic and autotrophic alkaliphiles that utilized thiocyanate as a nitrogen source were related to the previously described sulfur-oxidizing alkaliphiles belonging to the gamma subdivision of the division Proteobacteria (the Halomonas group for the heterotrophs and the genus Thioalkalivibrio for autotrophs). The third group included obligately autotrophic sulfur-oxidizing alkaliphilic bacteria able to utilize thiocyanate as a sole source of energy. These bacteria could be enriched on mineral medium with thiocyanate at pH 10. Growth with thiocyanate was usually much slower than growth with thiosulfate, although the biomass yield on thiocyanate was higher. Of the four strains isolated, the three vibrio-shaped strains were genetically closely related to the previously described sulfur-oxidizing alkaliphiles belonging to the genus Thioalkalivibrio. The rod-shaped isolate differed from the other isolates by its ability to accumulate large amounts of elemental sulfur inside its cells and by its ability to oxidize carbon disulfide. Despite its low DNA homology with and substantial phenotypic differences from the vibrio-shaped strains, this isolate also belonged to the genus Thioalkalivibrio according to a phylogenetic analysis. The heterotrophic and autotrophic alkaliphiles that grew with thiocyanate as an N source possessed a relatively high level of cyanase activity which converted cyanate (CNO-) to ammonia and CO2. On the other hand, cyanase activity either was absent or was present at very low levels in the autotrophic strains grown on thiocyanate as the sole energy and N source. As a result, large amounts of cyanate were found to accumulate in the media during utilization of thiocyanate at pH 10 in batch and thiocyanate-limited continuous cultures. This is a first direct proof of a "cyanate pathway" in pure cultures of thiocyanate-degrading bacteria. Since it is relatively stable under alkaline conditions, cyanate is likely to play a role as an N buffer that keeps the alkaliphilic bacteria safe from inhibition by free ammonia, which otherwise would reach toxic levels during dissimilatory degradation of thiocyanate.
121 citations
TL;DR: It is proposed that EPO/SCN−/H2O2reaction products comprise a potential SH-targeted cytotoxic system that functions in striking contrast to HOCl, the highly but relatively indiscriminantly reactive product of the neutrophil myeloperoxidase system.
119 citations
TL;DR: It is concluded that at plasma concentrations of bromide and thiocyanate, hypobromous acid and oxidation products of thiOCyanate are produced by eosinophil peroxidase.
Abstract: Eosinophil peroxidase has been implicated in promoting oxidative tissue damage in a variety of inflammatory conditions, including asthma It uses H(2)O(2) to oxidize chloride, bromide and thiocyanate to their respective hypohalous acids The aim of this study was to establish which oxidants eosinophil peroxidase produces under physiological conditions By measuring rates of H(2)O(2) utilization by the enzyme at neutral pH, we determined the catalytic rate constants for bromide and thiocyanate as 248 and 223 s(-1) and the Michaelis constants as 05 and 015 mM respectively On the basis of these values thiocyanate is preferred 28-fold over bromide as a substrate for eosinophil peroxidase Eosinophil peroxidase catalysed substantive oxidation of chloride only below pH 65 We found that when eosinophil peroxidase or myeloperoxidase oxidized thiocyanate, another product besides hypothiocyanite was formed; it also converted methionine into methionine sulphoxide During the oxidation of thiocyanate, the peroxidases were present as their compound II forms Compound II did not form when GSH was included to scavenge hypothiocyanite We propose that the unidentified oxidant was derived from a radical species produced by the one-electron oxidation of hypothiocyanite We conclude that at plasma concentrations of bromide (20-120 microM) and thiocyanate (20-100 microM), hypobromous acid and oxidation products of thiocyanate are produced by eosinophil peroxidase Hypochlorous acid is likely to be produced only when substrates preferred over chloride are depleted Thiocyanate should be considered to augment peroxidase-mediated toxicity because these enzymes can convert relatively benign hypothiocyanite into a stronger oxidant
108 citations
TL;DR: In this article, four novel non-interpenetrating metal-organic co-ordination networks of the CdII-L-NCS− system have been prepared using potentially bridging nicotinic acid derivatives.
Abstract: Four novel non-interpenetrating metal–organic co-ordination networks of the CdII–L–NCS− system have been prepared using potentially bridging nicotinic acid derivatives L [nicotinic acid (HL1), nicotinamide (L2), isonicotinamide (L3), or isonicotinate (L4)]. Their crystal structures were determined by X-ray diffraction. In [Cd(SCN)2(HL1)2]·HL11 each pair of cadmium(II) ions is bridged by two inversely related μ-NCS−-N,S ligands to form infinite chains with the remaining two trans positions of six-co-ordinated Cd atoms being occupied by two HL1 ligands, which form head-to-head double hydrogen bonds using the unco-ordinated carboxyl groups between adjacent chains to form two-dimensional layers. Weak S ⋯ S interactions between the NCS− ligands extend the layers into a three-dimensional framework with the channels enclosing HL1 guest molecules, which are interlinked into chains through O–H ⋯ N hydrogen bonds. [Cd(SCN)2(L2)2]·H2O 2 and [Cd(SCN)2(L3)2] 3 are interesting in that they contain unprecedented 16-membered [Cd4(μ-SCN-N,S)4] rings in the two-dimensional sheets. Between the sheets N–H ⋯ O amide–amide hydrogen bonds extend the two-dimensional layers to three-dimensional structures. [Cd(SCN)(L4)(H2O)] 4 exhibits two-dimensional wave-like networks with bridging NCS− and L4 ligands using both ends in co-ordination. The results demonstrate that the structures of the CdII–L–NCS system deeply depend on the nature of the nicotinic acid derivatives L.
105 citations
TL;DR: In this article, the preparation, crystal structures and magnetic properties of four heteroleptic copper(II) complexes with 2,3-bis(2-pyridyl)pyrazine (dpp) and azide, cyanate or thiocyanate as ligands are reported.
86 citations
TL;DR: In this article, the distribution behavior of metal ions in an aqueous two-phase system formed from a polyethylene glycol and sodium sulphate in the presence of thiocyanate or iodide ion was studied.
76 citations
TL;DR: The proposed method was successfully applied to the determination of thiocyanate in various human serum, saliva and urine samples.
73 citations
TL;DR: In this article, the synthesis and X-ray characterization of a novel two-dimensional network of copper and nickel heteronuclear complexes with two different thiocyanate groups are reported.
Abstract: The synthesis and X-ray characterization of a novel two-dimensional network of copper(II) and nickel(II) heteronuclear complexes with two different thiocyanate groups are reported, together with a preliminary study of the magnetic properties.
68 citations
TL;DR: Adsorption and electrosorption behavior of ethyl xanthate and thiocyanate (SCN-) anions, individually and when they are together in a solution, were studied at high-area C-cloth electrodes by in situ UV spectroscopy in relation to development of methodologies for purification of industrial wastewaters.
Abstract: Adsorption and electrosorption behavior of ethyl xanthate (EtX-) and thiocyanate (SCN-) anions, individually and when they are together in a solution, were studied at high-area C-cloth electrodes by in situ UV spectroscopy in relation to development of methodologies for purification of industrial wastewaters. The employment of straightforward, yet demonstrably useful spectrophotometric techniques of kinetics and scanning kinetics is described. Adsorption isotherms of EtX- and SCN- were also derived. However, EtX- was found to decompose to a small extent during electrosorption on C-cloth and/or Au or Pt surfaces, causing some interference with the spectrophotometric analysis of SCN- at 215 nm. After long prior contact of the C-cloth with water, the adsorption rates of EtX- and SCN- are somewhat increased. Competitive adsorption studies show that SCN- ion does not become adsorbed on the C-cloth in the presence of EtX-, thus demonstrating a remarkable discriminatory effect.
TL;DR: It is indicated that ligand displacement from a low-spin Co(III) center in a ligand environment that resembles NHase is not prohibitively slow so as to disallow catalytic action in nonredox active cobalt metalloenzymes.
Abstract: To determine how a substitutionally inert metal can play a catalytic role in the metalloenzyme nitrile hydratase (NHase), a reactive five-coordinate Co III thiolate complex ((Co III (S2 Me2 N3(Pr,Pr)))(PF6 )( 1)) that resembles the active site of cobalt containing nitrile hydratase (Co NHase) was prepared. This was screened for reactivity, by using low-temperature electronic absorption spectroscopy, toward a number of biologically relevant "substrates". It was determined 1 will react with azide, thiocyanate, and ammonia, but is unreactive toward nitriles, NO, and butyrate. Substrate-bound 1 has similar spectroscopic and structural properties as (Co III (ADIT2))(PF6 )( 2). Complex 2 is a six-coordinate Co III complex containing cis-thiolates and imine nitrogens, and has properties similar to the cobalt center of Co NHase. Substrate binding to 1 is reversible and temperature- dependent, allowing for the determination of the thermodynamic parameters of azide and thiocyanate binding and the rates of ligand dissociation. Azide and thiocyanate bind trans to a thiolate, and with similar entropies and enthalpies (thiocyanate: ¢H )- 7.5 ( 1.1 kcal/mol, ¢S )- 17.2 ( 3.2 eu; azide: ¢H )- 6.5 ( 1.0 kcal/mol, ¢S )- 12.6 ( 2.4 eu). The rates of azide and thiocyanate displacement from the metal center are also comparable to one another (kd ) (7.22 ( 0.04) 10 -1 s -1 for thiocyanate and kd ) (2.14 ( 0.50) 10 -2 s -1 for azide), and are considerably faster than one would expect for a low-spin d 6 six-coordinate Co III complex. These rates are comparable to those of an analogous Fe(III) complex, demonstrating that Co(III) and Fe(III) react at comparable rates when in this ligand environment. This study therefore indicates that ligand displacement from a low-spin Co III center in a ligand environment that resembles NHase is not prohibitivly slow so as to disallow catalytic action in nonredox active cobalt metalloenzymes.
TL;DR: In this paper, Bimetallic thiocyanate complexes crystal materials belonging to ABTC structure type: ZnCd(SCN) 4 (A = Zn, Cd, Mn) which are potentially useful in second harmonic generation (SHG) were prepared.
Abstract: Bimetallic thiocyanate complexes crystal materials belonging to ABTC structure type: ZnCd(SCN) 4 and AHg(SCN) 4 (A = Zn, Cd, Mn) which are potentially useful in second harmonic generation (SHG) have been prepared. Their structural, optical and physicochemical properties are characterized by infrared spectroscopy, X-ray powder diffraction, vis/UV/NIR spectroscopy, SHG measurements and thermal analysis. The states of crystal growth solutions are discussed in this article. The crystals belong to tetragonal system with the space group I4 and exhibit SHG efficiencies over one order of magnitude higher than that of urea. Their transparency cutoffs lie in the UV region, and they possess good physicochemical stabilities.
TL;DR: The promising features of polymeric sulfoalkylbetaine interaction layers for separation and analysis of biological extracts was also manifested in an application involving purification of biologically active peptide-pheromone obtained from Enterococcus faecium.
Abstract: Macroporous monoliths containing N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPE) have been synthesized via in situ photopolymerization, yielding a stoichiometric balance between sulfur and nitrogen in the final polymer, which is indicative of a genuine strong/strong zwitterionic character. The chromatographic properties of these zwitterionic resins were evaluated with respect to the retention behavior of inorganic ions and proteins. The weak electrostatic nature of the interaction between the sulfobetaine monoliths and proteins provided a high selectivity between basic proteins and peptides. Elution was accomplished with low-ionic-strength fully aqueous mobile phases, whereby high recovery was obtained, even for hydrophobic proteins. Chaotropic ions such as perchlorate or thiocyanate were used as mobile phase modifiers to modulate the apparent ion exchange group density, thus introducing a route for the modulation of the ionic strength that is required to competitively elute the protein. The promising features of polymeric sulfoalkylbetaine interaction layers for separation and analysis of biological extracts was also manifested in an application involving purification of biologically active peptide-pheromone obtained from Enterococcus faecium.
TL;DR: A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier with high selectivity for thiocyanate relative to many common organic and inorganic anions is described.
Abstract: A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10–6 to 1.0 × 10–1 mol L–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10–7 mol L–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.
TL;DR: In this paper, the crystal structure of compound 3 has been solved, consisting of discrete monomeric cationic entities containing cobalt(III) ions in a distorted octahedral environment.
TL;DR: In this article, the preparation and crystal growth of MMTC have been investigated, and the crystal grown is characterized by infrared spectroscopy, differential thermal analysis, thermogravimetric analysis and transmission spectrum.
TL;DR: The combination reagent (dichloroiodo)benzene and lead(II) thiocyanate in dichloromethane effects oxidation of various enol silyl ethers, ketene silyL acetals, and beta-dicarbonyl compounds, thereby providing an efficient and convenient method for alpha-thiochenation of carbonyl andBeta-Dicarboneyl compounds.
Abstract: The combination reagent (dichloroiodo)benzene and lead(II) thiocyanate in dichloromethane effects oxidation of various enol silyl ethers, ketene silyl acetals, and beta-dicarbonyl compounds, thereby providing an efficient and convenient method for alpha-thiocyanation of carbonyl and beta-dicarbonyl compounds.
TL;DR: The reaction of equivalent quantities of (L)AuCl (L = tetrahydrothiophene, trimethylphosphine, 2,6-xylyl isocyanide or mesityl isocalide) and KSCN in CH2Cl2-water gave (L,Au(SCN) in excellent yield.
Abstract: The reaction of equivalent quantities of (L)AuCl (L = tetrahydrothiophene, trimethylphosphine, 2,6-xylyl isocyanide or mesityl isocyanide) and KSCN in CH2Cl2–water gave (L)Au(SCN) in excellent yield. The products were formed through Cl ↔ (SCN) anion exchange in the two-phase systems. Crystals of (THT)Au(SCN) contain short inter-ion Au⋯Au contacts (3.006 A) within chain polymers of alternating cations [Au(THT)2]+ and anions [(NCS)2Au]−. The crystal structure of (Me3P)Au(SCN) exhibits dimers based on short Au⋯Au contacts of 3.099 A. The dimers appear to aggregate further by long Au⋯S contacts giving a tetrameric motif. Molecules of (2,6-Me2C6H3NC)Au(SCN) crystallise as flat, centrosymmetric dimers with long intermolecular Au⋯Au and Au⋯S contacts. Although the general aurophilic motif of (2,4,6-Me3C6H2NC)Au(SCN) is similar to (2,6-Me3C6H3NC)Au(SCN), its structure has two different dimers formed from similar monomers. The crystal structure of 2,6-Me2C6H3NC was also characterised and (consistent with bonding theory of metal isocyanides) exhibited a CN bond which is slightly longer than in the gold(I) complex.
TL;DR: In this paper, the steric requirements of the methyl group at the o-position of the pyridyl-N donor were investigated for tetrahedral four-coordinate (T-4) complexes.
Abstract: Chelate complexation of 4,4,5,5-tetramethyl-2-(6-methyl-2-pyridyl)imidazolin-1-oxyl 3-oxide (NITmepy) and 4,4,5,5-tetramethyl-2-(6-methyl-2-pyridyl)imidazolin-1-oxyl (IMmepy) to cobalt(II) chloride (bromide) or zinc(II) chloride afforded tetrahedral four-co-ordinate (T-4) complexes, [MX2(NITmepy)] and [MX2(IMmepy)] (MX = CoCl (1 and 2), CoBr (1Br and 2Br) or ZnCl (3 and 4), respectively) containing either a six- or a five-membered chelate ring as determined by single-crystal X-ray analysis. The formation of such T-4 complexes arises from the steric requirements of the methyl group at the o-position of the pyridyl-N donor. The UV-vis-NIR spectra suggest that both complexes 1 and 2 in dichloromethane retain their solid state structure. In acetonitrile, however, 1 exists as an equilibrium mixture due to dissociation of the co-ordinated NITmepy, while 2 is stable. The ligand-field spin-allowed and spin-forbidden d–d transitions of 1 and 2 are not influenced by the coordinated radical ligands. The reaction of nickel(II) chloride and thiocyanate with IMmepy gave a dichloro-bridged dinuclear complex with a square pyramidal five-co-ordinate (SPR-5) geometry and an OC-6 complex, respectively, [{NiCl(IMmepy)}2(μ-Cl)2] (5) and [Ni(NCS)2(IMmepy)2] (6). The intramolecular magnetic interactions in 1 and 2 are estimated to be antiferromagnetic, whereas 5 and 6 give ferromagnetic interactions. Complex 3, with one-dimensional columns, forms a dimer so that a moderate intermolecular antiferromagnetic coupling is demonstrated, while complex 4 exists as a discrete molecule in the crystal and shows paramagnetic behaviour.
TL;DR: Temperature was ineffective at changing the selectivity of retention between anion of the same grouping, however, significant selectivity changes, including elution order reversal, could be achieved between anions from different groupings.
TL;DR: In this article, the crystal structure of the bis(μ-diethanolaminato) bis(isothiocyanato)dicopper(II) complex was determined by single crystal X-ray diffraction.
TL;DR: In this paper, two strains of bacteria that were known to be capable of degrading thiocyanate were isolated from the Youanmi gold mine in Western Australia and inoculated into a laboratory-scale rotating biological contactor, where degradation took place in low-nutrient water.
TL;DR: Phenothiazines have been used as redox indicators for the determination of Fe (II), Sn(II), U(IV), Mo(V), ascorbic acid, etc.
Abstract: Phenothiazines substituted in the 2 and 10 positions exhibit many valuable analytical properties. They are easily oxidized in acidic medium with a number of oxidants, e.g., K2Cr2O7, NH4VO3, Ce(SO4)2, KBrO3, KIO3, KIO4, NaNO2, H2O2, and chloramine T, with the formation of colored oxidation products. This property enable certain phenothiazines to be used as redox indicators for the determination of Fe(II), Sn(II), U(IV), Mo(V), ascorbic acid, etc. Oxidation reactions of phenothiazines were also used for their determination by spectrophotometric and flow injection methods. Some ions, such as iron, vanadium, iodide, or nitrite have a catalytic effect on the oxidation of phenothiazines. Owing to these properties several catalytic methods for the determination of metals, iodide, and nitrite have been proposed. Phenothiazines react in acidic media with platinum metals, e.g., Pd(II), Ru(III), and Pt(IV), the formation of colored complexes. They also react with thiocyanate anionic complexes of metals, e.g., Co(II)...
TL;DR: In this paper, the authors used Potassium-dicyclohexyl-18-crown-6 cation complex as an excellent carrier for the selective and efficient transport of mercury as HgCl42− complex anion through a chloroform bulk liquid membrane.
TL;DR: In this article, a copolymer of styrene and 4-vinylbenzyl thiocyanate (PST-co-VBT) was investigated with regard to changes of the refractive index under UV irradiation (λ = 254 nm).
Abstract: Poly(4-vinylbenzyl thiocyanate) (PVBT) and a copolymer of styrene and 4-vinylbenzyl thiocyanate (PST-co-VBT) were investigated with regard to changes of the refractive index under UV irradiation (λ = 254 nm). After irradiation, the refractive index n D of PVBT films increased from 1.629 to 1.660. In the case of the copolymer PST-co-VBT n D increased from 1.616 to 1.630. The change of the refractive index mainly resulted from the photoinduced isomerization of thiocyanate groups (SCN) to the corresponding isothiocyanates (NCS). The NCS groups formed in the irradiated zones were selectively modified with gaseous amines (ammonia, propylamnie, ethylenediamine, and hydrazine) to give thiourea derivatives vias an addition reaction. The gas phase modification induced further changes of the refractive index without any loss of the film quality (e.g. propylamine, Δn up to -0.026, an hydrazine, Δn up to +0.035). In addition, the thickness h of the polymer films increased by up to 21% as a result of the gas phase modification. In contrast, wet chemical treatment with bulky amines (1-methylnaphthyl-amine, 1-pyrenemthylamine) caused a considerable deterioration of the film quality. The variation of the refractive index in polymers such as PVBT and PST-co-VBT is of potential interest for holographic and the recordings and the setup of polymer based DFB lasers.
TL;DR: In this paper, five co-ordination polymers 2∞[(AgSCN)2L] (L = N,N,N′-bis(3-aminopropyl)ethylenediamine) have been synthesized and structurally characterized by single-crystal X-ray diffraction.
Abstract: Five co-ordination polymers 2∞[(AgSCN)2L] (L = 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane or 1,5-diaminopentane) and 2∞[(AgSCN)3L] (L = N,N′-bis(3-aminopropyl)ethylenediamine) have been synthesized and structurally characterised by single-crystal X-ray diffraction. Each complex contains one-dimensional staircase-like 1∞[(AgSCN)2] chains in which each thiocyanate ligand acts in the μ-N,S,S-bridging mode. Every silver(I) atom in the staircase-like chain is further co-ordinated by a terminal nitrogen atom of the amine ligand to furnish a highly distorted AgN2S2 tetrahedral geometry. Both ends of the amine ligands participate in co-ordination, extending the one-dimensional staircase-like 1∞[(AgSCN)2] chains to two-dimensional staircase-like or square-wave like 2∞[(AgSCN)2L] networks in 1–4, whereas adjacent chelating ethylenediamine entities of the amine ligands in 5 are further interlocked with the Ag2(μ-S-SCN)2 dinuclear cores, resulting in a different formula 2∞[(AgSCN)3L].
TL;DR: The lamellar coordination polymer (SCN) as discussed by the authors is a two-stage coordination polymer, in which staircase-like CuSCN double chains are bridged by thiacrown ether ligands, and it can be prepared in two triclinic modifications by reaction of 1,10DT18C6 in respectively benzonitrile or water.
Abstract: The lamellar coordination polymer [(CuSCN)2(μ-1,10DT18C6)] (1,10DT18C6 = 1,10-dithia-18-crown-6), in which staircase-like CuSCN double chains are bridged by thiacrown ether ligands, may be prepared in two triclinic modifications 1 a and 1 b by reaction of CuSCN with 1,10DT18C6 in respectively benzonitrile or water. Performing the reaction in acetonitrile in the presence of an equimolar quantity of KSCN leads, in contrast, to formation of the K+ ligating 2-dimensional thiocyanatocuprate(I) net [{Cu2(SCN)3}–] of 2, half of whose Cu(I) atoms are connected by 1,10DT18C6 macrocycles. The potassium cations in [{K(CH3CN)}{Cu2(SCN)3(μ-1,10DT18C6)}] (2) are coordinated by all six potential donor atoms of a single thiacrown ether in addition to a thiocyanate S and an acetonitrile N atom. Under similar conditions, reaction of CuI, NaSCN and 1,10DT18C6 affords [{Na(CH3CN)2}{Cu4I4(SCN)(μ-1,10DT18C6)}] (3), which contains distorted Cu4I4 cubes as characteristic molecular building units. These are bridged by thiocyanate and thiacrown ether ligands into corrugated Na+ ligating sheets. In the presence of divalent Ba2+ cations, charge compensation requirements lead to formation of discrete [Cu(SCN)3(1,10DT18C6-κS)]2– anions in [Ba{Cu(SCN)3(1,10DT18C6-κS)}] (4).
Schichtartige CuSCN-haltige Koordinationspolymere mit dem Alkalikationen koordinierenden Thiakronenether 1,10-Dithia-18-Krone-6
Das schichtartige Koordinationspolymer [(CuSCN)2(μ-1,10DT18C6)] (1,10DT18C6 = 1,10-Ditha-18Krone-6) enthalt treppenartige CuSCN-Doppelketten, die durch 1,10DT18C6-Liganden verbruckt sind. Zwei trikline Modifikationen 1 a und 1 b lassen sich durch die Umsetzung von CuSCN und 1,10DT18C6 in Benzonitril bzw. Wasser darstellen. Im Beisein einer aquimolaren Menge von KSCN fuhrt die Reaktion in Acetonitril dagegen zur Bildung des zweidimensionalen Thiocyanatocuprat (I)-Netzes [{Cu2(SCN)3}–] von 2. Die Halfte der hierin beteiligten Cu(I)-Atome werden durch 1,10DT18C6-Makrozyklen verbunden, die die K+-Gegenionen koordinieren. Diese werden in [{K(CH3CN)}Cu2(SCN)3(μ-1,10DT18C6)}] (2) von allen 6 potentiellen Donoratomen eines Thiakronenethers sowie von einem Thiocyanat-S- und einem Acetonitril-N-Atom umgeben. Unter analogen Bedingungen liefert die Umsetzung zwischen CuI, NaSCN und 1,10DT18C6 das Polymer [{Na(CH3CN)2}{Cu4I4(SCN)(μ-1,10DT18C6)}] (3), das verzerrte Cu4I4-Wurfel als charakteristische molekulare Baueinheiten enthalt. Diese werden durch Thiocyanat- sowie Thiakronenether-Liganden zu wellenartigen anionischen Schichten verbunden, die Na+-Kationen koordinieren. Im Beisein von Ba2+-Kationen bedingt der notwendige Ladungsausgleich die Bildung von diskreten Anionen [Cu2(SCN)3(1,10DT18C6-κS)]2– in [Ba{Cu(SCN)3(1,10DT18C6κS)}] (4).
TL;DR: A.C. DU PLESSIS, P. BARNARD, R.M. MUHLBAUER and K. NALDRETT 2001.
Abstract: C.A. DU PLESSIS, P. BARNARD, R.M. MUHLBAUER AND K. NALDRETT. 2001.
Aims: The aim of this investigation was to develop an empirical model for the autotrophic biodegradation of thiocyanate using an activated sludge reactor.
Methods and Results: The methods used for this purpose included the use of a laboratory scale activated sludge reactor unit using thiocyante feed concentrations from 200 to 550 mg l−1. Reactor effluent concentrations of <1 mg l−1 thiocyanate were consistently achieved for the entire duration of the investigation at a hydraulic retention time of 8 h, solids (biomass) retention of 18 h and biomass (dry weight) concentrations ranging from 2 to 4 g l−1. A biomass specific degradation rate factor was used to relate thiocyanate degradation in the reactor to the prevailing biomass and thiocyanate feed concentrations. A maximum biomass specific degradation rate of 16 mg−1 g−1 h−1 (mg thiocyanate consumed per gram biomass per hour) was achieved at a thiocyanate feed concentration of 550 mg l−1. The overall yield coefficient was found to be 0·086 (biomass dry weight produced per mass of thiocyanate consumed).
Conclusions: Using the results generated by this investigation, an empirical model was developed, based on thiocyanate feed concentration and reactor biomass concentration, to calculate the required absolute hydraulic retention time at which a single-stage continuously stirred tank activated sludge reactor could be operated in order to achieve an effluent concentration of <1 mg l−1. The use of an empirical model rather than a mechanistic-based kinetic model was proposed due to the low prevailing thiocyanate concentrations in the reactor.
Significance and Impact of the Study: These results represent the first empirical model, based on a comprehensive data set, that could be used for the design of thiocyanate-degrading activated sludge systems.
TL;DR: It is shown, using patch clamp recording from CFTR-transfected mammalian cell lines, that under steady-state conditions neitherSCN- conductance nor SCN- permeability show anomalous mole fraction behaviour, and that SCN conductance, permeability, and block of Cl- permeation can be reproduced by a rate theory model that assumes only a single intrapore anion binding site.
Abstract: Immediately following exposure to thiocyanate (SCN-)-containing solutions, the cystic fibrosis conductance regulator Cl- channel exhibits high unitary SCN conductance and anomalous mole fraction behaviour, suggesting the presence of multiple anion binding sites within the channel pore. However, under steady-state conditions SCN-conductance is very low. Here I show, using patch clamp recording from CFTR-transfected mammalian cell lines, that under steady-state conditions neither SCN- conductance nor SCN- permeability show anomalous mole fraction behaviour. Instead, SCN conductance, permeability, and block of Cl- permeation can all be reproduced by a rate theory model that assumes only a single intrapore anion binding site. These results suggest that under steady-state conditions the interaction between SCN- and the CFTR channel pore can be understood by a simple model whereby SCN- ions enter the pore more easily than Cl-, and bind within the pore more tightly than Cl-. The implications of these findings for investigating and understanding the mechanism of anion permeation are discussed.