Complexes of Zr<Superscript>IV</Superscript> and Hf<Superscript>IV</Superscript> with monolacunary Keggin-and Dawson-type anions

The reactions of the tetranuclear hydroxo complexes [M₄(μ₂-OH)₈(H₂O)₁₆]⁸⁺ (M = Zr or Hf) with the lacunary Keggin-type ([α-PW₁₁O₃₉]⁷⁻) and Dawson-type ([α ₂-P₂W₁₇O₆₁]¹⁰⁻) phosphotungstates in aqueous solutions produce the sandwich polyoxometalate complexes [M(α-PW₁₁O₃₉)₂]¹⁰⁻ (M = Zr (1) or Hf (2)) and [M(α ₂-P₂W₁₇O₆₁)₂]¹⁶⁻ (M = Zr (3) and Hf (4)). The complexes were isolated and structurally characterized as salts with potassium and dimethylammonium cations. The zirconium and hafnium atoms have a square antiprismatic coordination environment (coordination number is 8). In all complexes, the mutual arrangement of the ligands corresponds to the syn isomer. Hafnium complexes 2 and 4 are the first structurally characterized polyoxometalate complexes of this metal. The structures of the resulting compounds were confirmed also by ³¹P NMR spectroscopy in solution. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 214–218, February, 2007.     

Thiolate-bridged Trinuclear Heterobimetallic Complexes [Cd(μ-SPh-4-Me)4{M(PPh3)2}2] (M?=?Cu, Ag) and [Sn(μ-SPh)6(AgPPh3)2]

Abstract  

Reaction of the [Me₄N]₂[Cd(SPh-4-Me)₄] with two equivalents of [M(PPh₃)₂NO₃] afforded the neutral linear trinuclear complexes [Cd(μ-SPh-4-Me)₄{M(PPh₃)₂}₂] (M = Cu 1, Ag 2) in which two [M(PPh₃)₂]⁺ fragments chelate with the opposite edges of a tetrahedral [Cd(SPh-4-Me)₄]²⁻ moiety via the sulfur atoms of the Me-4-PhS⁻ species. Treatment of [Sn(SPh)₄] with two equivalents of [Ag(PPh₃)₂NO₃] gave the neutral linear trinuclear complex [Sn(μ-SPh)₆(AgPPh₃)₂] (3) that is composed of a central distorted SnS₆ octahedron sharing two opposite planes with two slightly distorted AgS₃P tetrahedrons. Complexes 2 and 3 are air and optically stable. Their nonlinear optical absorption and refraction were investigated under the same conditions. The nonlinear optical absorption and refraction of complex 2 were determined to be α ₂ = 3.11 × 10⁻¹¹ m/W and n ₂ = 4.15 × 10⁻¹² esu, respectively. The nonlinear optical absorption and refraction of complex 3 were determined to be α ₂ = 8.36 × 10⁻¹¹ m/W and n ₂ = 1.47 × 10⁻¹¹ esu, respectively.     

Kinetic and mechanistic studies on the electron-transfer reactions between diaquabisethylenediaminecobalt(III) and ethylenediaminetetraacetatocobaltate(III) with promazine in acidic aqueous media

The kinetics of the electron-transfer reactions between promazine (ptz) and [Co(en)₂(H₂O)₂]³⁺ in CF₃SO₃H solution ([Co^III] = (2–6) × 10⁻³ m, [ptz] = 2.5 × 10⁻⁴ m, [H⁺] = 0.02 − 0.05 m, I = 0.1 m (H⁺, K⁺, CF₃SO ₃ ⁻ ), T = 288–308 K) and [Co(edta)]⁻ in aqueous HCl ([Co^III] = (1 − 4) × 10⁻³ m, [ptz] = 1 × 10⁻⁴ m, [H⁺] = 0.1 − 0.5 m, I = 1.0 m (H⁺, Na⁺, Cl⁻), T = 313 − 333 K) were studied under the condition of excess Co^III using u.v.–vis. spectroscopy. The reactions produce a Co^II species and a stable cationic radical. A linear dependence of the pseudo-first-order rate constant (k _obs) on [Co^III] with a non-zero intercept was established for both redox processes. The rate of reaction with the [Co(en)₂(H₂O)₂]³⁺ ion was found to be independent of [H⁺]. In the case of the [Co(edta)]⁻ ion, the k _obs dependence on [H⁺] was linear and the increasing [H⁺] accelerates the rate of the outer-sphere electron-transfer reaction. The activation parameters were calculated as follows: ΔH ^≠ = 105 ± 4 kJ mol⁻¹, ΔS ^≠ = 93 ± 11 J K⁻¹mol⁻¹ for [Co(en)₂(H₂O)₂]³⁺; ΔH ^≠ = 67 ± 9 kJ mol⁻¹, ΔS ^≠ = − 54 ± 28 J K⁻¹mol⁻¹ for [Co(edta)]⁻.     

Syntheses, Structures, and Nonlinear Optical Properties of Two Crown-like Heteroselenometallic Compounds [Et4N]4[(μ5-WSe4)(CuX)5(μ-X)2] (X = Cl, Br)

Two isostructural crown-like heteroselenometallic cluster compounds, [Et₄N]₄[(μ₅-WSe₄)(CuX)₅(μ-X)₂] (X = Cl 1, Br 2), were prepared from the reactions of [Et₄N]₂[WSe₄] with CuX and [Et₄N]X· xH₂O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(μ₅-WSe₄)(Cu-X)₅(μ-X)₂]⁴⁻ anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe₄]²⁻ moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be α₂ = 6.15 × 10⁻¹⁰ m/W and n ₂ = 4.18 × 10⁻¹¹ esu, respectively.     

Syntheses,Structures and Properties of Three Heteonuclear Complexes Containing [V<Subscript>10</Subscript>O<Subscript>28</Subscript>]<Superscript>6−</Superscript> Units

Three heteonuclear complexes containing [V₁₀O₂₈]⁶⁻ units, {[Cu(pyr)(H₂O)₄]₂(H₃O)₂[V₁₀O₂₈] · 13.5H₂O}_n (1), {[Ni(pyr)(H₂O)₄]₂(H₃O)₂[V₁₀O₂₈] · 9.5H₂O}_n (2) and [Zn₂(H₂O)₁₄(V₁₀O₂₈)] · H₂PPZ (3) are synthesized and characterized by elemental analyses, IR, single crystal X-ray analyses. The complex 1 and 2 have the similar structures which are composed of the [V₁₀O₂₈]⁶⁻ cluster anion and 1D chain {[M (pyr)(H₂O)₄]²⁺}_n (M = Cu Ni) cations bridged by pyrazine. In the complex 3, Zn²⁺ with two coordination modes is bridged by water molecules to build 1D zigzag chains, and then is linked to the bridging oxygen atoms from [V₁₀O₂₈]⁶⁻ to generate a 2D grid architecture filled with the protoned piperazine (PPZ) molecules. In this paper, the magnetic properties of complex 2 are characterized.     

Outer-Sphere electron-transfer and the effect of linkage isomerism in the titanium(III) reduction of nitro-pentacyanocobaltate(III) and nitro-, and nitrito-pentaamminecobalt(III) complexes in aqueous acidic media

The reductions of [Co(CN)₅NO₂]³⁻, [Co(NH₃)₅NO₂]²⁺ and [Co(NH₃)₅ONO]²⁺, by Ti^III in aqueous acidic solution have been studied spectrophotometrically. Kinetic studies were carried out using conventional techniques at an ionic strength of 1.0 mol dm⁻³ (LiCl/HCl) at 25.0 ± 0.1 °C and acid concentrations between 0.015 and 0.100 mol dm⁻³. The second-order rate constant is inverse—acid dependent and is described by the limiting rate law:- k₂ ≈ k₀ + k[H⁺]⁻¹,where k=k′K_a and K_a is the hydrolytic equilibrium constant for [Ti(H₂O)₆]³⁺. Values of k₀ obtained for [Co(CN)₅NO₂]³⁻, [Co(NH₃)₅NO₂]²⁺ and [Co(NH₃)₅ONO]²⁺ are (1.31 ± 0.05) × 10⁻² dm³ mol⁻¹ s⁻¹, (4.53 ± 0.08) × 10⁻² dm³ mol⁻¹ s⁻¹ and (1.7 ± 0.08) × 10⁻² dm³ mol⁻¹ s⁻¹ respectively, while the corresponding k′ values from reductions by TiOH²⁺ are 10.27 ± 0.45 dm³ mol⁻¹ s⁻¹, 14.99 ± 0.70 dm³ mol⁻¹ s⁻¹ and 17.93 ± 0.78 dm³ mol⁻¹ s⁻¹ respectively. Values of K _a obtained for the three complexes lie in the range (1–2) × 10⁻³ mol dm⁻³ which suggest an outer-sphere mechanism.     

Development of efficient method for preconcentration and determination of copper, nickel, zinc and iron ions in environmental samples by combination of cloud point extraction and flame atomic absorption spectrometry

A cloud point extraction procedure for the preconcentration of copper, nickel, iron and zinc ions in various samples has been described. Analyte ions in aqueous phase are complexed with 3-((indolin-3-yl)(phenyl)methyl)indoline (IYPMI) and following centrifugation quantitatively extracted to the aqueous phase rich in Triton X-114. The surfactant-rich phase was dissolved in 2.0 mol L⁻¹ HNO₃ in methanol prior to metal content determination by flame atomic absorption spectrometry (FAAS). The effects of some parameters including, the concentrations of IYPMI, Triton X-114 and HNO₃, bath temperature, centrifuge rate and time were investigated on the recoveries of analyte ions. At optimum conditions, the detection limits of (3 SDb m⁻¹) of 1.6, 2.8, 2.1 and 1.1 ng mL⁻¹ for Cu²⁺, Fe³⁺, Ni²⁺ and Zn²⁺ along with preconcentration factors of 30 and enrichment factor of 48, 39, 34 and 52 for Cu²⁺, Ni²⁺, Fe³⁺ and Zn²⁺ respectively, were obtained. The proposed cloud point extraction has been successfully applied for the determination of metal ions in real samples with complicated matrix such as biological, soil and blood samples with high efficiency.      

Ternary ion-association complexes between the indium(III) - 4-(2-pyridylazo)resorcinol anionic chelate and some tetrazolium cations

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The optimum conditions for extraction of In(III) as a ternary complex, (TT⁺)[In(PAR)₂] or (MTT⁺)[In(PAR)₂], were found: pH, extraction time, concentration of PAR and concentration of TZS. The constants of extraction (K_ex), constants of association (β), constants of distribution (K_D) and recovery factors (R%) were determined. The apparent molar absorptivities in chloroform were calculated to be ɛ′₅₂₀=6.6×10⁴ L mol⁻¹ cm⁻¹ and ɛ′₅₁₅=7.1×10⁴ L mol⁻¹ cm⁻¹ for the systems with TTC (I) and MTT (II), respectively. Beer’s law was obeyed for In(III) concentrations up to 3.4 μg mL⁻¹ in both the cases. The limits of detection (LOD=0.07 μg mL⁻¹ I and LOD=0.12 μg mL⁻¹ II), limits of quantification (LOQ=0.24 μg mL⁻¹ I and LOQ=0.41 μg mL⁻¹ II) and Sandell’s sensitivities (SS) were estimated as well.      

Synthesis and Crystal Structures of Group 10 Metal Bis(dithiolate) Complexes Constructed by 2,3-Naphtho-15-Crown-5 or 2,3-Naphtho-18-Crown-6

Five novel 2,3-naphtho crown ether group 10 metal bis(dithiolate) complexes, [Na(N15C5)₂]₂[Pd(mnt)₂] (1), [Na(N15C5)]₂[Pd(i-mnt)₂] (2) and [K(N18C6)]₂[M(i-mnt)₂] (3 5) (where mnt = 1,2-dicyanoethylene-1,2-dithiolate, i-mnt = 1,1-dicyanoethylene-2,2-dithiolate and M = Ni, Pd, Pt for complexes 3–5, respectively), have been synthesized and characterized by elemental analysis, FT-IR, UV–Visible spectra and single crystal X-ray diffraction. X-ray diffraction analyses reveal that complexes 1 and 2 have different structural features while complexes 3–5 are structurally isomorphous. Complex 1 consists of two [Na(N15C5)₂]⁺ sandwich complex cations and one [Pd(mnt)₂]²⁻ anion, affording a zero-dimensional structure. For 2, the [Na(N15C5)]⁺ mono-capped complex cations act as the bridges linking the [Pd(i-mnt)₂]²⁻ anions into a 1D infinite chain through Na–N interactions and SȮFC and SȮFπ interactions are observed in the resulting chain. Complexes 3–5 all consist of two [K(N18C6)]⁺ complex cations and one [M(i-mnt)₂]²⁻ (M = Ni, Pd or Pt) anion and the complex molecules are linked into␣1D␣chains by the bridging K–O(ether) interactions between the adjacent [K(N18C6)]⁺ units. What’s novel is that the resulting chains are assembled into novel 2D networks through interchain π–π stacking interactions between the neighboring naphthylene moieties of N18C6. The stack model of naphthylene group in complexes 3–5 is discussed.     

Simultaneous determination of silicic acid, Ca, Mg and Al in mineral water and composite tablets by Ion chromatography

Summary A simple, selective and sensitive ion-chromatography method was investigated for simultaneously determining silicic acid, Ca²⁺, Mg²⁺, Al³⁺ and anions (Cl⁻ and NO ₃ ⁻ ) in real samples. It involved a single-column ion-chromatograph with sodium hydroxide-methanol-water eluent and conductometric detection. Cations were converted to complex anions by adding EDTA to the sample solution. A set of well-defined peaks of silicic acid, Ca²⁺, Mg²⁺, Al³⁺, Cl⁻ and NO ₃ ⁻ were obtained. Detection limits using 3.3σ (σ=standard deviation of blank solution) were 1.25×10⁻⁶ M for H₃SiO ₄ ⁻ , 1.32×10⁻⁶ M for Ca²⁺, 1.28×10⁻⁶ M for Mg²⁺, 1.33×10⁻⁶ M for Al³⁺, 1.31×10⁻⁶ M for Cl⁻ and 1.24×10⁻⁶ M for NO ₃ ⁻ . The method was successfully applied to analysis of mineral water and composite tablets.     

Two Novel Organic–Inorganic Hybrid Compounds Constructed from Anderson-type Clusters and Transition-Metal Complexes

Abstract  Two organic–inorganic hybrid compounds based on the Anderson-type clusters [TeMo₆O₂₄]⁶⁻, [(H₂O)₂Co(TeMo₆O₂₄)][(C₁₀N₂H₁₀)₂] · 9.5H₂O (1), [(C₁₀N₂H₉)Ni(H₂O)₃]₂[TeMo₆O₂₄] · 8.5H₂O (2), have been synthesized by hydrothermal reactions and characterized by elemental analyses, IR spectra, thermal stability analyses, and single-crystal X-ray diffraction. Compound 1 displays a 1D chain structure constructed from alternating [TeMo₆O₂₄]⁶⁻clusters and Co²⁺ along the a axis with two pendant ligands 4,4′-bpy (4,4′-bipyridine). Compound 2 is composed of [TeMo₆O₂₄]⁶⁻ clusters coordinated by [Ni(bpy)(H₂O)₃]²⁺ moieties, and a supramolecular architecture is further formed through extensive hydrogen bonds interactions. Graphical Abstract  Two organic–inorganic hybrid compounds based on the Anderson-type clusters [TeMo₆O₂₄]⁶⁻and the unit [M(4,4′-bpy)] have been synthesized under the hydrothermal conditions. Compound 1 displays a 1D chain structure constructed covalently from alternating polyoxoanions [TeMo₆O₂₄]⁶⁻ and Co²⁺ along the a axis with two pendant ligands 4,4′-bipyridine. Compound 2 is composed of [TeMo₆O₂₄]⁶⁻ polyoxoanion coordinated by [Ni(bpy)(H₂O)₃]²⁺ moieties and shows a 1D chain structure through the hydrogen bonds interactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis, structure, and characterization of a silicotungstate anion-supported organic-inorganic hybrid complex [Zn(2,2′-Bipy)3]1.5[SiW12O40Zn(2,2′-Bipy)2(OH)] · 0.25H2O

A new Keggin-type silicotungstate anion-supported organic-inorganic hybrid transition metal complex, [Zn(Bipy)₃]_1.5[SiW₁₂O₄₀Zn(Bipy)₂(OH)] · 0.25H₂O (I) (Bipy = 2,2′-bipyridine), has been synthesized by the hydrothermal method and characterized by elemental analysis, IR, UV, and EPR spectra, TG-DTA analysis, and single crystal X-ray diffraction. The structural analysis indicates that each structural unit of I consists of one [SiW₁₂O₄₀Zn(Bipy)₂(OH)]³⁻ heteropolyanion, one and a half isolated [Zn(Bipy)₃]²⁺ cations, and a quarter of crystal water molecule. The [Zn(Bipy)₂(OH)]⁺ unit is covalently bonded to one Keggin polyoxoanion [SiW₁₂O₄₀]⁴⁻ in the [SiW₁₂O₄₀Zn(Bipy)₂(OH)]³⁻ cluster. The EPR spectrum indicates the existence of Zn²⁺ with the high-spin state, and TG-DTA analysis exhibits that I has two steps of weight loss and the polyoxoanion framework is collapsed at 618°C.     

Mass Spectrometric Determination of Association Constants of Bovine Serum Albumin (BSA) with para-Sulphonato-Calix[n]arene Derivatives

Electrospray Ionization Mass Spectrometry (ESI/MS) has been used to determine the association constants (K_As) and binding stoichiometries for parent para-Sulphonato-calix[n]arenes and their derivatives with bovine serum albumin (BSA). K_A values were determined by titration experiments using a constant concentration of protein. K_A measurements were carried out in a methanol–formic acid solution. 5,11,17,23–tetra-Sulphonato-calix[4]arene (1a) and 25-mono-(2-aminoethoxy)-5,11,17,23-tetra-Sulphonato-calix[4]arene (1d) interact strongly with BSA showing 3 non-equivalent binding sites with K_A1 = 7.69 × 10⁵ M⁻¹, K_A2 = 3.85 × 10⁵ M⁻¹, K_A3 = 0.33 × 10⁵ M⁻¹ and K_A1 = 1.69 × 10⁵ M⁻¹, K_A2 = 2.94 × 10⁵ M⁻¹, K_A3 = 0.60 × 10⁵ M⁻¹, respectively. The strength of the interactions between the calixarene and BSA is inversely proportional to the size of macrocyclic ring: n = 4 > n=6>>n=8.     

The unmediated choline sensor based on layered double hydroxides in hydrogen peroxide detection mode

In this work, we have developed a novel choline biosensor on the basis of immobilization of choline oxidase (ChOx) by the attractive materials layered double hydroxides (LDHs). Amperometric detection of choline was evaluated by holding the modified electrode at 0.5 V (vs. SCE). Due to the special properties of LDHs ([Zn₃-Al-Cl]), such as chemical inertness, high porosity, and swelling property, the [Zn₃-Al-Cl]/ChOx modified electrode exhibited an enhanced analytical performance. The biosensor provided a linear response to choline over a concentration range from 3.7 × 10⁻⁶ to 6.3 × 10⁻⁴ M with a low detection limit of 3 × 10⁻⁷ M based on S/N=3. The apparent Michaelis-Menten constant was calculated to be 1.38 mM. In addition, the interaction between ChOx and LDHs has also been investigated using FT-IR spectroscopy.     

Electrocatalytic determination of dopamine in pharmaceutical and human serum samples by using [N,N′-bis(2-pyridine carboxamido)-1,2-benzene] nickel(II) modified carbon paste electrode

The main purpose of this study is to develop an inexpensive, simple, selective and especially sensitive modified carbon paste electrode (MCPE) for the determination of dopamine (DA) in pharmaceutical and human serum samples. The carbon paste electrode (CPE) has been modified by using [N,N′-bis(2-pyridine carboxamido)-1,2-benzene] nickel(II) complex (Ni(II)bpb) and the electrochemical behavior of the modified electrode has been studied by cyclic voltammetry. The modified electrode shows an excellent electrocatalytic effect on the oxidation of DA. Under optimum conditions, calibration plots are found to be linear in the range of 7.0 × 10⁻⁷−1.0 × 10⁻⁵ M (r ₂ = 0.9940) and 1.0 × 10⁻⁵−1.0 × 10⁻⁴ M (r₂ = 0.9945); the detection limit is 6.2 × 10⁻⁸ M. The preparation of MCPE is very easy. The electrode can be renewed by simple polishing. The proposed method shows good sensitivity, reproducibility (RSD ∼ 2.9%), high stability (more than two month) without any considerable change in response and recovery for the determination of DA. The prepared electrode has been successfully applied to the voltammetric determination of DA in pharmaceutical and biological samples. The article is published in the original.     

Determination of cadmium in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

The formation of a complex with 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) and cloud point extraction have been applied to the preconcentration of cadmium followed by its determination by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation were optimized. At pH 7.0, preconcentration of only 10 mL of sample in the presence of 0.05% TritonX-114 and 2.5 × 10⁻⁶ M 5-Br-PADAP enabled the detection of 0.04 μg/L cadmium. The enrichment factor was 21 for cadmium. The regression equation was A = 0.0439C(μg/L) + 7.2 × 10⁻³. The correlation coefficient was 0.9995. The precision for 10 replicate determinations at 10 μg/L Cd was 2.7% relative standard deviation (RSD). The proposed method has been applied to the determination of cadmium in water samples. The text was submitted by the authors in English.     

Kinetic and mechanism of alkene polymerization

Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C₆F₅)₃}₂]⁻ (1), [H₂N{(C₆F₅)₃}₂]⁻ and [M{CNB(C₆F₅)₃}₄]²⁻ (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe₂/1/AlBu ₃ ⁱ (SBI = rac-Me₂Si(Ind)₂) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl₂/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C₆F₅)₃}₂]⁻ > [H₂N{(C₆F₅)₃}₂]⁻ ≈ B(C₆F₅) ₄ ⁻ ≫ [MeB(C₆F₅)₃]⁻. The highest productivities were of the order of ca. 3.0 × 10⁸ g PP (mol Zr)⁻¹ h⁻¹ [C₃H₆]⁻¹, about 1.3–1.5 times higher than with B(C₆F₅) ₄ ⁻ as the counter anion. The titanium system CGCTiMe₂/1/AlBu ₃ ⁱ gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH₂SiMe₃)(μ-Me)B(C₆F₅)₃ and [(SBI)MCH₂SiMe ₃ ⁺ ...B(C₆F₅) ₄ ⁻ ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C₆F₅)₃ compound exists as a simple inner-sphere ion-pair, the B(C₆F₅) ₄ ⁻ compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the γ-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I _a) pathway. The text was submitted by the authors in English.     

Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 × 10⁻⁴ M; NaCl, 1.0% (w/v). LOD was 1.9 μg/L with a preconcentration factor of 10–20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.     

Hydrothermal synthesis and structural characterization of novel α-Keggin unit-supported Cu(II)- and Mn(II)-bipyridine complexes from a <Emphasis Type="Italic">tri</Emphasis>-lacunary precursor

Blue [{Cu(2,2′-bipy)₂}₂{α-SiW₁₂O₄₀}] (bipy = bipyridyl) (1) and pale yellow [Mn(2,2′-bipy)₃]₂[α-SiW₁₂O₄₀] (2) have been synthesized hydrothermally and characterized by IR spectroscopy and single crystal X-ray structure analysis. In 1, the [α-SiW₁₂O₄₀]⁴⁻ ion acts as a bridge between the two [{Cu(2,2′-bipy)₂]²⁺ moieties via coordination through the terminal oxygen atoms, while in 2, the [Mn(2,2′-bipy)₃]²⁺ ion balances the charge on the polyoxo anion without forming any covalent bond. To the best of our knowledge, this is the first example of transition metal-mediated transformation of [α-SiW₉O₃₄]¹⁰⁻ to [α-SiW₁₂O₄₀]⁴⁻. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A lanthanide sensitized chemiluminescence method of flow-injection for the determination of ulifloxacin and prulifloxacin

A lanthanide sensitized chemiluminescence method of flow-injection was developed for the determination of a new fluoroquinolone, ulifloxacin (UFX), and its prodrug prulifloxacin (PUFX). The proposed method was based on the remarkable chemiluminescence enhancement effect of UFX (PUFX) on KMnO₄−Na₂S₂O₄−Ln(III). Tb(III) ion was chosen from lanthanides because it showed the best sensitizing effect. Under optimized experimental conditions, the relative chemiluminescence intensity was in linear relationship with UFX and PUFX concentrations in the ranges of 1.0 × 10⁻⁸ − 5.0 × 10⁻⁶ M and 9.0 × 10⁻⁹ − 5.0 × 10⁻⁶ M, respectively. The minimum detectable value and relative standard deviation were 5.5 × 10⁻⁹ M, 1.5% for UFX and 7.0 × 10⁻⁹ M, 2.9% for PUFX, respectively. The proposed method was applied to the determination of UFX in spiked human serum and urine, and of PUFX in tablets with satisfactory results. The possible mechanism of chemiluminescence was also proposed. The text was submitted by the authors in English.