Solvation of thiocyanate complexes of mercury(II) by 2-hexylpyridine from aqueous mineral acid solutions

The extraction of trace amounts of mercury(II) by 2-hexylpyridine dissolved in benzene from aqueous mineral acid solutions has been studied. The replacement of chloride, nitrate and sulfate ions by the potentially ambidentate, linear and less basic thiocyanate group offers interestingly high extraction coefficients. The value of the distribution coefficients may be lowered by complexing mercury with oxalate, thiosulfate, acetate or citrate ions in the aqueous phase. The possible mechanism of extraction has been discussed in the light of the results of extraction isotherms and slope analysis data. Distribution coefficients and separation factors of several metal ions relative to mercury(II) are reported for the three mineral acid systems and the possible removal of mercury along with some other inorganic pollutants from aqueous solutions is suggested.     

Liquid-liquid extraction of zinc from aqueous thiocyanate solutions with 5-(-4-pyridyl)nonane in benzene

5-(4-Pyridyl)nonane dissolved in benzene has been applied to the extraction of zinc, down to very low concentration (< 10(-6)M), from aqueous thiocyanate solutions. The metal can be quantitatively extracted from neutral and acidic thiocyanate solutions (up to 5M HCl, 0.25M HNO(3) or 0.25M H(2)SO(4)) in a single extraction. Equilibration times of 5 min are sufficient for almost complete extraction. The optimum thiocyanate concentration range is 0.05-0.5M. Among the common anions chloride exerts a slight depressing effect on extraction from neutral solution when present in high concentration. The extraction mechanism and the composition of the extracted complexes of zinc are discussed. The metal is predominantly extracted by means of a solvate mechanism. The effect of chloride, nitrate, sulphate, acetate, citrate, oxalate and ascorbate ions on the extraction of zinc is described. Several elements, including those of interest in separation of zinc, have been tested for extraction from O.1M KSCN at the optimal concentrations of the mineral acids, and the separation factors estimated.     

Studies on the solvent extraction of technetium from thiocyanate solutions in mineral acids

Technetium-99m, separated from fission molybdenum-99, has been studied as a component of liquid-liquid phase distribution equilibria. 5-(4-Pyridyl)nonane in a carrier diluent, benzene, has been used to study the distribution of the nuclide from thermodynamically suitable aqueous phases of electrolytes with and without sterically receptive thiocyanate ions. Efficient extraction of the metal can be accomplished in a variety of aqueous phase compositions. The separation factors with respect to molybdenum, under certain experimental conditions, are fairly high. The data have been utilized to effect clean separations of technetium from molybdenum.     

Solvation of thiocyanate complexes of tungsten(VI) by 5-(4-pyridyl) nonane from aqueous hydrochloric acid solutions

5-(4-Pyridyl)nonane has been evaluated as a solvent for trace amounts (<5·10^–5 M) of tungsten(VI) from aqueous chloride-thiocyanate solutions. Remarkable enhancements in metal extractability are observed on the addition of SCN^– to aqueous hydrochloric acid solutions. Extremal partition coefficients are obtained from 0.1 M HCl in 0.2 M KSCN. Diminutions of the metal extractability are produced by relatively high (>0.5 M) SCN^– concentrations and increased concentration of the supporting acid. Slope analysis data, under optimal parameters, indicates the most probable composition of the extractable species as WO₂(SCN)₂·2P_YN. Neutral anions do not have any significant effect on the D values. Behaviour of a number of metal ions has been checked using optimal aqueous conditions of extraction. The investigation shows that the reagent has a great potential for the preconcentration of a number of metal ions including the common toxins.     

Structures and magnetic properties of copper(II) complexes containing tetrakis(2-pyridyl)methane

We designed spiro-fused dinculear complexes using tetrakis(2-pyridyl)methane (py₄C) for the development of ground high-spin molecules. We attempted to prepare a dinuclear copper(II) complex [{Cu(hfac)₂}₂(py₄C)], where hfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, but we obtained [Cu(hfac)₂(py₄C)] and [Cu(hfac)(py₄C) · Cu(hfac)₃]. These molecular structures were determined by the X-ray crystal structure analysis.     

Copper Catalysed Oxygenation of Bis (2-pyridyl) methane and 6-Methyl-bis (2-pyridyl)methane to the Corresponding Ketones

The ligands (L) bis (2-pyridyl) methane (BPM) and 6-methyl-bis (2-pyridyl)methane (MBPM) form the three complexes CuL²⁺, CuL, and Cu₂L₂H with Cu²⁺. Stability constants are log K₁ = 6.23 ± 0.06, log K₂ = 4.83 ± 0.01, and log K (Cu₂L₂H + 2H²⁺ ? 2 CuL²⁺) = ?10.99 ± 0.03 for BPM and 4.56 ± 0.02, 2.64 ± 0.02, and ?11.17 ± 0.03 for MBPM, respectively. In the presence of catalytic amounts of Cu²⁺, the ligands are oxygenated to the corresponding ketones at room temperature and neutral pH. With BPM and 2,4,6-trimethylpyridine (TMP) as the substrate and the buffer base, respectively, the kinetics of the oxygenation can be described by the rate law with k₁ = (5.9 ± 0.2) · 10^?13 mol l^?1 s^?1, k₂ = (4.0 ± 0.6) · 10^?4 mol^?1 ls^?1, k₃ = (1.1 ± 0.1) · 10^?12 mol l^?1 s^?1, and k₄ = (9 ± 2) · 10^?14 mol l^?1 s^?1.     

Hydrothermal synthesis of a 2-(2-pyridyl)imidazole derivative and its copper(II) and zinc(II) complexes

The hydrothermal synthesis of a heterocyclic quaternary nitrogen compound, namely, 6,7-dihydro-pyrido[2′,1′:3,4]pyrazino[1,2-a]imidazol-5-ium-bromide monohydrate (LBr · H₂O) is reported. Various spectroscopic analyses were performed on the cationic heterocycle. Cu^II and Zn^II halide complexes of this novel ligand were prepared. The heterocycle and its complexes were characterized by single crystal X-ray diffraction analysis. Both complexes contain neutral [M^IILX₃] molecules, where the cyclic ligand (L⁺) is coordinated to the metal as a monodentate ligand. The Cu²⁺ complex has a distorted tetrahedral geometry, indicating an obvious steric effect from L⁺ on the chloride co-ligand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

4-(5-Nonyl)pyridine as an extractant for cobalt thiocyanate complexes from mineral acid solutions

The partition behaviour of cobalt into 4-(5-nonyl)pyridine (NPy) in benzene from aqueous hydrochloric, nitric and sulfuric acid media containing variable amounts of potassium thiocyanate is described. Cobalt is quantitatively extracted by NPy from 0.1–1M KSCN solutions at 0.01 M concentration of the mineral acids. The extraction mechanism and the possible compositions of the extracted species are discussed. The effects of foreign salts on the extraction of cobalt from three mineral acid solutions are reported. Several elements including those which are of some interest in connection with the separation of cobalt were tested for extraction from 0.01 M solutions of mineral acids 0.3 M with respect to KSCN and their factors for separation from cobalt were estimated.     

Tetrakis(4-pyridyl)porphyrin supramolecular complexes with cyclodextrins in aqueous solution

The formation of inclusion complexes of hydroxypropyl-beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin with 5,10,15,20-tetrakis(4-pyridyl)porphyrin (TpyP) has been studied in aqueous buffer solution (phosphate buffer pH = 7 and I = 0.01 M) to give a structural and spectroscopic characterization of a new class of potential sensitizers for photodynamic therapy. The interaction was investigated by a combination of UV/Vis absorption, fluorescence anisotropy, time-resolved fluorescence and circular dichroism. The experimental results point to the presence of the pigment in water in a monomeric complexed form. The fluorescence anisotropy measurements suggest that TpyP forms 1:1 complexes with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin, while 1:2 complexes are obtained with heptakis(2,6-di-O-methyl)-beta-cyclodextrin.     

Extraction of thiocyanate complexes of cobalt(II) by diphenyl-2-pyridylmethane in benzene from mineral acid solutions

Extraction of Co(II) by diphenyl-2-pyridylmethane (DPPM) in benzene form mineral acid solutions containing potassium thiocyanate has been studied at room temperature (23±2°C). Its extraction from mineral acids alone is rather poor. Optimal aqueous phase composition for the quantitative extraction of Co(II) by 0.1M DPPM is 0.1M acid+0.2M KSCN. Stoichiometric studies indicate that an ionic type complex, (DPPM·H)₂·Co(SCN)₄, is responsible for extraction. The metal can be back-extracted from the organic phase by aqueous acetate, citrate or oxalate solutions. Separation factors from other metals determined under optimal conditions reveal that Co(II) can be quantitatively separated from CsI), Sr(II), Cr(III), Ln(III), Zr(IV), Hf(IV), Cr(VI) and Tc(VII), Mo(VI), Zn(II), Au(III), Hg(II) and U(VI) are, however, coextracted and hence should be previously removed by other techniques or reagents.     

Crystal structures of copper(II) and zinc(II) complexes derived from 3-(2-pyridyl)pyrazole

Two dinuclear complexes [Zn(μ-L)(NO₃)(H₂O)]₂ (1) and [Cu₂(μ-L)₂(HL)₂](NO₃)₂(C₁₂H₈Br₂)_0.5·H₂O (2), (HL = 3-(2-pyridyl)pyrazole, C₁₂H₈Br₂ = 4,4′-dibromobiphenyl) are synthesized under hydrothermal conditions and characterized by elemental analysis and X-ray single crystal diffraction. Crystal data for 1: triclinic, \(P\bar 1\), a = 8.8478(7) Å, b = 15.0550(11) Å, c = 16.4310(12) Å, α = 107.588(4)°, β = 112.498(3)°, γ = 115.595(3)°, V = 2099.8(9) ų, Z = 2; for 2: triclinic, \(P\bar 1\), a = 7.2870(15) Å, b = 8.6840(17) Å, c = 9.3290(19) Å, α = 107.588(4)°, β = 112.498(3)°, γ = 115.595(3)°, V = 528.77(18) ų, Z = 1. Complex 1 and 2 are both dinuclear structures which are further packed into a 1D supramolecular chain and a 3D supramolecular framework via weak C–H…O hydrogen bond interactions respectively.     

Spectrophotometric determinationof zinc in cooking salts,tap and mineral waters with phenylglyoxal mono(2-pyridyl)hydrazone

The behaviour of phynylglyoxal mono(2-pyridyl)hydrazone (PGMPH) with various metal ions was studied by spectrophotometry. The reaction of zinc with PGMPH provides a sensitive and precise method for the determination of zinc in tap and mineral waters and in cooking salts. Zinc ion reacts with PGMPH at pH 7.2—8.5 in solutions containing 40% (v/v) ethanol to form a yellow-orange complex with maximum absorbance at 464—470 nm. The molar absorptivity of the 1:2 ZnPGMPH complex is 71 300 1 mol^?1 cm^?1. Interferences are considered in detail.     

Some lanthanide complexes of N-(2-pyridyl) acetamide

The complexes formed in the reaction between some lanthanide perchlorates and N-(2-pyridyl)acetamide (aapH) have been prepared and characterized. The compounds have the formulae [Ln(aapH)₄] (ClO₄)₃ (where Ln  Pr, Nd, Eu, Gd, Ho, Yb and Lu) and are solid crystalline substances. The new compounds were characterized by means of chemical analyses, molar conductivities, vibrational spectra, thermograviemetry and electronic absorption and emission spectra. The vibrational spectra and molar conductances indicate that the perchlorate groups are ionic and that aapH acts as a bidentate ligand through the carbonyl oxygen and the ring nitrogen. The PMR of La(aapH)₄ (ClO₄)₃ and [Lu(aapH)₄]ClO₄)₃ reveals that the ligands are planar and corroborates the vibrational evidence that they coordinate in a bidentate manner. The oscillator strength (P_exp) of the hypersensitive transition of the Nd(III) complex has been studied and the nephelauxetic effect has been evalauted. The emission of the Eu(III) complex at 77° is very intense and a tentative assignment of its symmetry has been made.     

Synthesis of tetrakis(2-pyridyl)methane: the first tetrapyridylmethane

Tetrakis(2-pyridyl)methane has been synthesized as the first member of tetrapyridylmethane family by nucleophilic aromatic substitution of 2-chloropyridine with tris(2-pyridyl)methyl anion in refluxing aromatic hydrocarbons; the use of 2-bromopyridine resulted in electron transfer giving rearranged dimer of tris(2-pyridyl)methyl radical.     

Unloaded polyurethane foams as solid extractants for some metal thiocyanate complexes from aqueous solution

Zinc, mercury, and indium are quantitatively extracted with unloaded polyurethane foams from aqueous thiocyanate solution. The unloaded polyester type foam will extract the thiocyanate complexes of the three metals as well as the polyether type. The extraction is strongly dependent on the thiocyanate concentration and is quantitative over a wide pH range.     

Tricarbonylrhenium(I) and -technetium(I) complexes with bis(2-pyridyl)phenylphosphine and tris(2-pyridyl)phosphine

(NEt₄)₂[Re(CO)₃Br₃] or (NEt₄)₂[Tc(CO)₃Cl₃] react with bis(2-pyridyl)phenylphosphine (PPhpy₂) or tris(2-pyridyl)phosphine (Ppy₃) under formation of neutral tricarbonyl complexes of the composition [M(CO)₃X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy₂ or Ppy₃). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt₄)₂[Re(CO)₃Br₃] by the addition of AgNO₃ in THF/water, and subsequent reaction of the resulting [Re(CO)₃(THF)₃](NO₃)with Ppy₃ yielded the complex [Re(CO)₃(NO₃)(Ppy₃-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.