Thiocyanate Systems Research Articles

From Cd(SCN)2(CH4N2S)2 to Cd(SCN)2(C4H6N2)2: Controlling Sulfur Content in Thiocyanate Systems Significantly Improves the Overall Performance of UV Nonlinear Optical Materials

AbstractCombining a strong second‐order nonlinear optical (NLO) effect (>1×KH2PO4 (KDP)), a large band gap (>4.2 eV), and a moderate birefringence in ultraviolet (UV) NLO crystals remains a formidable challenge. Herein, Cd(SCN)2(C4H6N2)2, the first example of a thiocyanate capable of realizing a phase‐matched UV NLO crystal material, is obtained by reducing the sulfur (S) content in the centrosymmetric (CS) structure of Cd(SCN)2(CH4N2S)2. Compared to the “shoulder‐to‐shoulder” one‐dimensional (1D) chain of Cd(SCN)2(CH4N2S)2, Cd(SCN)2(C4H6N2)2 has a different sawtooth 1D chain structure. Cd(SCN)2(CH4N2S)2 has second harmonic generation (SHG) inertia with a band gap of 3.90 eV and a UV cutoff edge of 342 nm, however, it possesses a large birefringence (0.35@546 nm). In contrast, the symmetry center breaking of Cd(SCN)2(C4H6N2)2 leads to remarkably strong SHG intensity (10 times that of KDP). Furthermore, it has a wide band gap (4.74 eV), short UV cutoff edge (234 nm), and moderate birefringence capable of phase matching (0.17@546 nm). This research indicates that thiocyanates are a promising class of UV NLO crystal materials, and that modulation of the sulfur content of CS thiocyanates is an effective strategy for the development of UV NLO crystals with excellent overall performances.

From Cd(SCN)2(CH4N2S)2 to Cd(SCN)2(C4H6N2)2: Controlling Sulfur Content in Thiocyanate Systems Significantly Improves the Overall Performance of UV Nonlinear Optical Materials.

Combining a strong second-order nonlinear optical (NLO) effect (>1×KH2PO4 (KDP)), a large band gap (>4.2 eV), and a moderate birefringence in ultraviolet (UV) NLO crystals remains a formidable challenge. Herein, Cd(SCN)2(C4H6N2)2, the first example of a thiocyanate capable of realizing a phase-matched UV NLO crystal material, is obtained by reducing the sulfur (S) content in the centrosymmetric (CS) structure of Cd(SCN)2(CH4N2S)2. Compared to the "shoulder-to-shoulder" one-dimensional (1D) chain of Cd(SCN)2(CH4N2S)2, Cd(SCN)2(C4H6N2)2 has a different sawtooth 1D chain structure. Cd(SCN)2(CH4N2S)2 has second harmonic generation (SHG) inertia with a band gap of 3.90 eV and a UV cutoff edge of 342 nm, however, it possesses a large birefringence (0.35@546 nm). In contrast, the symmetry center breaking of Cd(SCN)2(C4H6N2)2 leads to remarkably strong SHG intensity (10 times that of KDP). Furthermore, it has a wide band gap (4.74 eV), short UV cutoff edge (234 nm), and moderate birefringence capable of phase matching (0.17@546 nm). This research indicates that thiocyanates are a promising class of UV NLO crystal materials, and that modulation of the sulfur content of CS thiocyanates is an effective strategy for the development of UV NLO crystals with excellent overall performances.

Study on the Galvanic Interaction of Gold and Main Associated Minerals Based on Density Functional Theory

The galvanic interaction of gold and associated sulfide minerals in thiocyanate systems has a significant impact on gold leaching. The density functional theory was used to further reveal the galvanic interaction between gold and associated minerals. The electron transfer between gold and its associated minerals at different galvanic interaction distances was simulated. The results show that with the increase of the contact distance between pyrite and gold, the charge of pyrite increases, indicating that it is losing electrons gradually; the charge of arsenopyrite and chalcocite decreases with the rise of the contact distance between gold and pyrite, suggesting that they are gaining electrons. In addition, gold has the greatest influence on the gain and loss of electrons in pyrite and arsenopyrite and has the least influence on chalcocite. Through the calculation of the density of states, it is found that different distances of galvanic interaction have a great influence on the density of states of surface atoms under the action of pyrite and arsenopyrite with gold but have little effect on the density of states of surface atoms under the action of chalcocite with gold.

1D cadmium(II) thiocyanate systems: Synthesis and characterization of three new polymeric 1D cadmium(II) thiocyanato complexes

Abstract Three new cadmium(II) thiocyanato complexes, [{Cd(NCS)2(val)}·H2O]n 1, [Cd(NCS)2(3-ampy)2]n 2, and [Cd(NCS)2(pyrazolinone)]n 3, (val = d , l -valine, 3-ampy = 3-aminopyridine and pyrazolinone = 3-methyl-1-phenyl-2-pyrazolin-5-one) have been synthesized and structurally characterized. The X-ray structure analysis revealed di-μ-N,S thiocyanato bridges connecting cadmium centers in a 1D chain with the co-ligand blocking the remaining coordination sites. The structure of complex 1 features six coordinate Cd(II) centers, each cadmium is surrounded by two N atoms and two S atoms from two bridging N,S-thiocyanato groups giving rise to a zigzag 1D chain and two oxygen atoms of the alternating chelating μ-O,O′-valine that coordinates as zwitterionic terminal amino acid. The structure of complex 2 consists of octahedral Cd(II) centers, connected by di-μ-N,S-bridging NCS groups, thus forming a 1D chain system along the [1 0 1] direction. The amino-groups are forming one intra-chain N H⋯N hydrogen bond and one interchain N H⋯N hydrogen bond to N-atoms of adjacent chains. The structure of 3 reveals di-μ-N,S-NCS doubly bridged unusual penta-coordinated cadmium centers with the alternating monodentate pyrazolinone ligand blocking the fifth coordination site. IR spectra and thermal properties of complexes are reported.

Aqueous Phase Thiosulfate Removal Using Photo catalysis

Removal of thiosulfate (S2O32-, 200 mg/L) from simulated wastewater samples was investigated under varying co-pollutants and pH conditions employing the titanium dioxide (TiO2) mediated photocatalysis. For thiosulfate only studies higher substrate removal was noted at lower pH with a specific trend of pH 4 > pH 7 > pH 10. Furthermore, near complete thiosulfate removal was also achieved at pH 4. A similar thiosulfate removal trend was also noted for the binary thiosulfate & p-cresol and thiosulfate & thiocyanate systems at pH 4, indicating high photocatalysis process efficiency. However, thiosulfate removal from the mixed systems at pH greater than 4 was slower as compared to the respective thiosulfate only systems. Nevertheless for the binary thiosulfate & thiocyanate system, significant thiosulfate removal was noted even at pH 12 when the thiosulfate concentration was reduced to 40 mg/L.

Chemical characterization of the gallium(III) and indium(III) thiocyanate systems in aqueous and dimethylsulfoxide solution

The decomposition of the thiocyanate ion in acidic aqueous solution disturbs the complex formation reactions with gallium(III) and indium(III) to such an extent that any accurate stability constants cannot be obtained. Calorimetric studies have shown that several reactions besides the complex formation take place at the addition of thiocyanate to aqueous solutions of gallium(III) and indium(III). The origin of these reactions has not been possible to establish, but they seem to be metal ion dependent. An EXAFS study on an aqueous gallium(III) thiocyanate solution with excess thiocyanate showed the presence of hydrated gallium(III) ions and a small fraction of gallium(III) hydrolysis products at pH = 2. This shows that the complex formation between gallium(III) and thiocyanate is very weak in aqueous solution if it takes place at all. The thiocyanate ion is stable in aprotic solvents as dimethylsulfoxide, and complex formation studies of gallium(III) and indium(III) with thiocyanate can be performed in a normal way. One weak mononuclear complex is formed in the gallium(III)- and indium(III)-thiocyanate systems in dimethylsulfoxide under prevailing conditions with K 1 and Δ H 1 values of 30 ± 5 dm 3 mol − 1 and 9 ± 2 kJ mol − 1 , and 105 ± 9 dm 3 mol − 1 and 1.13 ± 0.05 kJ mol − 1 , respectively. An EXAFS study on gallium(III) thiocyanate in dimethylsulfoxide solution showed that the thiocyanate ion is coordinated through the sulfur atom with a Ga–S bond distance of 2.198(6) Å, and a change in the coordination number of gallium(III) from six to five, with a mean Ga–O bond distance of 1.902(6) Å to the four dimethylsulfoxide molecules.

Inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices by peroxidase systems

To study the bactericidal properties of the lactoperoxidase (LPER)-thiocyanate and soybean peroxidase (SBP)-thiocyanate systems at low pH, their efficiency for inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices, their effect on colour stability of the juices and interaction with ascorbic acid. Three-strain cocktails of E. coli and Shigella spp. in selected juices were supplemented with the LPER or SBP system. Within 24 h at 20 degrees C, the LPER system inactivated both cocktails by > or = 5 log10 units in apple, 2-5 log10 units in orange and < or = 1 log10 unit in tomato juices. In the presence of SBP, browning was significant in apple juice and white grape juice, slight in pink grape juice and absent in orange or tomato juice. Ascorbic acid protected E. coli and Shigella against inactivation by the LPER system, and peroxidase systems significantly reduced the ascorbic acid content of juices. Our results suggest a different specificity of LPER and SBP for SCN-, phenolic substrates of browning and ascorbic acid in acidic juices. The LPER system appeared a more appropriate candidate than the SBP system for biopreservation of juices. This work may open perspectives towards the development of LPER or other peroxidases as biopreservatives in acidic foods.

In vitro evaluation of antibacterial and antioxidant activities of the essential oil and methanol extract of endemic Zataria multiflora Boiss

The present study was conducted to evaluate in vitro antibacterial and antioxidant properties of essential oil and methanol extracts from a unique and endemic plant, Zataria multiflora Boiss. The antibacterial test results showed that the essential oil of the plant strongly inhibited the growth of all of the microorganisms studied especially the Gram-negative strains. The polar fraction of methanol extract has been effective against Gram-positive strains, while the non-polar fraction has shown activity similar to essential oil. The antioxidant potential of the samples was evaluated using two separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ammonium thiocyanate systems. Sub fractions of the methanol extract were able to reduce the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an IC 50 of 11.7 ± 1.58 and 16.2 ± 1.61 μg/ml, respectively for non-polar and polar ones, which the activity of the latter almost is equal to synthetic antioxidant BHA (18.2 ± 1.94 μg/ml). Inhibition values of linoleic oxidation were calculated to be 82.4% and 80.3% for the polar and non-polar fractions, respectively. The essential oil to be showed more inhibition (89.7 ± 2.5), similar to the synthetic antioxidants BHA (97.8 ± 2.94) and ascorbic acid (93.2 ± 2.1). The chemical composition of hydrodistilled essential oils of Z. multiflora was analyzed by GC/MS. A total of 25 compounds representing 99.78% of the oil were identified: thymol (37.59%), carvacrol (33.65%); para-cymene (7.72%), γ-terpinene (3.88%) and β-caryophyllene (2.06%) were the main components comprising 84.9% of the oil. Results here show that the essential oil and methanol extract of Z. multiflora possess antioxidant and antibacterial activity, and therefore it could be used as a natural preservative ingredient in food and/or pharmaceutical industries.

Synthesis, structure and bonding of cadmium(II) thiocyanate systems featuring nitrogen based ligands of different denticity

Complexes catena-[di(4-amino-pyridine)di(μ-S,N-thiocyanato)cadmium(II)], [ Cd ( μ - SCN ) 2 ( L 1 ) 2 ] 1 ∞ ( 1 ) , catena-[{(1-pyridine-2-yl-ethylene)-hydrazine}di(μ-S,N-thiocyanato)cadmium(II)], [ Cd ( μ - SCN ) 2 ( L 2 ) ] 1 ∞ ( 2 ) , and di-μ-S,N-thiocyanatobis{( N,N-diethyl- N′-(1-pyridine-2-yl-ethylidene)-ethane-1,2-diamine)( N-thiocyanato)cadmium(II)}, [Cd(NCS)(μ-SCN)(L 3)] 2 ( 3) have been synthesized by reacting cadmium acetate/NH 4SCN with 4-amino-pyridine (L 1), C 5H 4N–C(CH 3) NNH 2 (L 2), and C 5H 4N–C(CH 3) N–CH 2–CH 2–N(C 2H 5) 2 (L 3), respectively, in methanol. Characterization by single-crystal X-ray crystallography shows that in compounds 1 and 2 the cadmium atoms have a 4N2S-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric chains. Compound 3 is a centrosymmetric dimeric complex, with the cadmium atom pseudo octahedrally surrounded by a 5N1S coordination sphere. In compound 1 the crystal packing is controlled mainly by interchain N–H⋯N and C–H⋯π interactions between the aminopyridine moieties, whereas in complexes 2 and 3 π-stacking interactions between the pyridyl planes stabilize the interchain or intermolecular packing, respectively. Thiocyanate and pyridylimine chelation to metal center is also scrutinized with EHMO analysis.

Isentropic Compressibility of Aqueous and Methanolic Sodium Thiocyanate Solutions

The speed of sound in aqueous and methanolic sodium thiocyanate solutions was measured as a function of temperature (∼293.15 ≤ T/K ≤ 323.15) and concentration (∼0.0146 ≤ m/(mol kg-1) ≤ 17.328). The isentropic compressibility isotherms for aqueous sodium thiocyanate systems converge at a particular concentration characteristic of the primary hydration shell of the solute. For the methanolic sodium thiocyanate system isentropic compressibility isotherms vary smoothly with concentration. The primary solvation number of the thiocyanate ion has been estimated to be 12.8 in aqueous medium. The total primary solvation number of sodium thiocyanate in methanol medium was found to be 3.7.

The cobalt(II) and nickel(II) thiocyanate systems: a spectrophotometric study

The cobalt(II) and nickel(II) thiocyanate systems: a spectrophotometric study

Selective sorption of heavy metal thiocyanate complexes on crown ether resin

AbstractThe sorption behavior of heavy metal thiocyanate complexes was investigated for dibenzo‐18‐crown‐6 (DB18C6) resin and bis[2‐(o‐methoxyphenoxy)ethyl]ether (BMPE) resin. The DB18C6 resin showed a high sorption ability and the degree of zinc sorption increased significantly with thiocyanate concentration. This behavior was not observed for BMPE resin. The sorption behavior was influenced by the countercation species, and the degree of sorption of zinc ions showed the maximum when the potassium thiocyanate was used as a complexing salt. The sorbed species appear to be KZn(SCN)3, K2Zn(SCN)4 in the potassium thiocyanate system, and Zn(SCN)2 in the lithium thiocyanate system, respectively, according to analysis of the sorption equilibrium. Sodium and ammonium thiocyanate systems show an intermediate behavior of the two. The sorption selectivity for DB18C6 resin depended not only on the hydrophobic nature of heavy metal thiocyanate complexes but also on the stabilization of counter cation species with crown ether matrix, and the sorption selectively was found to be effectively controlled by countercation species according to the cation‐chelation mechanism.

ChemInform Abstract: Equilibrium and Enthalpy Measurements on the Copper(I) and Silver(I) Chloride, Bromide, Iodide and Thiocyanate Systems in Tetrahydrothiophene

Abstract Potentiometric and calorimetric measurements have been carried out for the determination of the stability constants and the enthalpy changes of the formation of copper(I) and silver(I) halide and thiocyanate complexes in tetrahydrothiophene (THT). THT is a sulfur donor solvent, which solvates the soft acceptors copper(I) and silver(I) well. THT has a low dielectric constant ϵ≈8, which affects the stability constants and the complex distribution, since the solvent has limited ability to neutralize ionic charges. Two mononuclear complexes are formed in all systems. The stabilities of the stepwise silver(I) halide complexes increase in the order Cl − − − . The stabilities of the first copper(I) halide complexes are almost identical, while the stabilities of the second copper(I) halide complexes follow the sequence Cl − >Br − − . The neutral complexes of these systems are considerably more stable in THT than in any other previously studied solvent, in spite of the strong solvating properties of THT. This is because the electrostatic forces become predominant in a solvent with a low dielectric constant where charges are neutralized through ion pair formation. The enthalpy changes of the formation of the first complexes are small and negative, except for copper- (I) chloride and iodide where small positive values are found. For all systems, the second complexes are formed in strongly endothermic reactions.

Equilibrium and enthalpy measurements on the copper(I) and silver(I) chloride, bromide, iodide and thiocyanate systems in tetrahydrothiophene

Potentiometric and calorimetric measurements have been carried out for the determination of the stability constants and the enthalpy changes of the formation of copper(I) and silver(I) halide and thiocyanate complexes in tetrahydrothiophene (THT). THT is a sulfur donor solvent, which solvates the soft acceptors copper(I) and silver(I) well. THT has a low dielectric constant ϵ≈8, which affects the stability constants and the complex distribution, since the solvent has limited ability to neutralize ionic charges. Two mononuclear complexes are formed in all systems. The stabilities of the stepwise silver(I) halide complexes increase in the order Cl −<Br −<I −. The stabilities of the first copper(I) halide complexes are almost identical, while the stabilities of the second copper(I) halide complexes follow the sequence Cl −>Br −<I −. The neutral complexes of these systems are considerably more stable in THT than in any other previously studied solvent, in spite of the strong solvating properties of THT. This is because the electrostatic forces become predominant in a solvent with a low dielectric constant where charges are neutralized through ion pair formation. The enthalpy changes of the formation of the first complexes are small and negative, except for copper- (I) chloride and iodide where small positive values are found. For all systems, the second complexes are formed in strongly endothermic reactions.

Enhancement of sensitivity of ion-exchanger absorptiometry by using a thick ion-exchanger layer

Enhancement of the sensitivity of ion-exchanger absorptiometry by the use of much thicker ion-exchanger layers than those previously employed has been investigated. Because the background attenuance due to light-scattering from the solid particle layer increases only moderately, whereas the net absorbance of the sorbed sample species increases greatly when the cell length is increased, a cell with at least 10-mm path-length may be effectively used without difficulty in most commercial spectrophotometers, giving at least ten times the sensitivity obtainable with a 1-mm cell. Since the background attenuance depends on the optical geometry, it can be lowered to some extent by using a particular type of spectrophotometer, and by placing a cylindrical mirror between the cell and the light-detector window or by setting the cell as close as possible to the window. The use of such long cells has been found to improve the sensitivity in the chromium—diphenylcarbazide, iron—1,10-phenanthroline, nickel—PAN, cadmium—PAR, bismuth—chloride and uranium—thiocyanate systems. Other methods may be similarly improved.

Phase behavior and conductivity in poly(ethylene oxide)–sodium thiocyanate systems

Observed phases and transition temperatures in mixtures of poly(ethylene oxide) and sodium thiocyanate (PEO–NaSCN) are described by a binary phase diagram. The components of this system are semicrystalline PEO which can dissolve salt up to a mole fraction Xs=0.023, and a crystalline complex of composition PEO3.5NaSCN (Xcc=0.22). The salt-deficient PEO component is normally formed by a eutectic reaction with eutectic temperature Te=63 °C. Conductivity of PEO–NaSCN mixtures is calculated assuming that only ions in the amorphous, liquidlike regions contribute to charge transport. This model predicts a positive discontinuity in conductivity on eutectic melting, and a sharp maximum in conductivity at low salt concentrations, in agreement with observed behavior.

ChemInform Abstract: Spectrophotometric Investigations of the Octahedral‐Tetrahedral Equilibria in Cobalt(II)‐Thiocyanate Systems in Aqueous Methanol (equilibrium constants of complex formation.

ChemInform Abstract: Spectrophotometric Investigations of the Octahedral‐Tetrahedral Equilibria in Cobalt(II)‐Thiocyanate Systems in Aqueous Methanol (equilibrium constants of complex formation.

Thermodynamics and Structures of Complexes in Solvents Coordinating through Nitrogen. III. Equilibrium and Enthalpy Measurements on the Copper(I) and Silver(I) Chloride, Bromide, Iodide and Thiocyanate Systems in Pyridine.

Thermodynamics and Structures of Complexes in Solvents Coordinating through Nitrogen. III. Equilibrium and Enthalpy Measurements on the Copper(I) and Silver(I) Chloride, Bromide, Iodide and Thiocyanate Systems in Pyridine.

Spectrophotometric investigations of the octahedral-tetrahedral equilibria in cobalt(II)-thiocyanate systems in aqueous methanol

Spectrophotometric investigations of the octahedral-tetrahedral equilibria in cobalt(II)-thiocyanate systems in aqueous methanol

Some stereochemical aspects of actinide coordination chemistry

Some stereochemical aspects of actinide coordination chemistry