Die Kristallstrukturen von Pb4SeBr6, Pb5S2J6 und Pb7S2Br10

Crystal Structures of Pb₄SeBr₆, Pb₅S₂I₆, and Pb₇S₂Br₁₀. The crystal structures of Pb₄SeBr₆, Pb₅S₂I₆ and Pb₇S₂Br₁₀ have been determined from single crystal X-ray analyses. Unit cell data see “Inhaltsübersicht”. The compounds have common structural features with the pure halides of lead. In Pb₄SeBr₆ all Pb atoms have trigonal prismatic coordination by Br(Se), additional neighbours above the prism faces completing the coordination number to 7, 8 or 9. In Pb₅S₂I₆ some of the Pb atoms are surrounded by 6 I + 1 S or 5 I + 3 S in the same extended trigonal prismatic arrangement, others are in the centers of PbI₆ octahedra. Pb₇S₂Br₁₀ is isostructural with Th₇S₁₂ with statistical occupancy of part of the metal and nonmetal positions.     

Elektrochemische Synthese von Ag5Pb2O6

Electrochemical Synthesis of Ag₅Pb₂O₆ Ag₅Pb₂O₆ was prepared by anodic oxidation of silver in a PbO₂ suspension in an aqueous KOH solution. Phase purity was checked by a Rietveld‐fit of the X‐ray powder pattern, thermal and chemical analysis. The compound exhibits ionic conductivity. It' anisotropy leads to an orientation of the crystallites on the silver anode.     

Dilead mercury chromate(VI), Pb2HgCrO6

The structure of Pb₂HgCrO₆ (space group P) can be described as consisting of isolated [CrO₄]^2? tetrahedra and nearly linear [HgO₂]^2? dumb‐bells, which form layers of composition [HgCrO₆]^4?. These are intercalated with corrugated pseudo‐hexagonal Pb²⁺ layers. The Pb²⁺ cation is stereochemically active and has coordination 3+5.     

Synthesis and properties of Na6[Pb(S2O3)4] · 6H2O

Conditions for the synthesis of the water-soluble lead thiosulfate complex Na₆[Pb(S₂O₃)₄] · 6H₂O were determined. The complex synthesized was characterized by UV and IR spectroscopy and X-ray phase and thermal analyses. Thermolysis schemes were proposed on the basis of the IR and mass spectra of the thermal decomposition products.     

Stark-mixing effect on the 6p 2 1 S 0−6p 2 3 P 2 transition in Pb I

The intensity of the 531.5 nm electric-field-quench radiation has been measured on a thermal beam of neutral Pb atoms in the metastable 6p ^{2 1} S ₀ state. The measurement yields a Stark-mixing amplitude for transition between the 6p ^{2 1} S ₀ and 6p ^{2 3} P ₂ states. Combining this result with available experimental data sets an upper limit for the 6p 7s ³ P ₁ → 6p ^{2 1} S ₀ transition probability:A _ki <1.79·10³ s ^?1. Calculations for the 6p 7s → 6p ² and 6p 8s → 6p ², as well as transition rates of forbidden lines inside 6p ² configuration of PbI are presented and compared with existing experimental data.     

Structural Characterization of Pb6Sb6Se17

The ternary selenide Pb₆Sb₆Se₁₇ was synthesized hydrothermally from the binaries (PbSe and Sb₂Se₃) and crystallizes in the orthorhombic space group Pbam (a = 15.835(3), b = 24.043(5), c = 4.134(2)Å, Z = 2). The main building blocks of the crystal structure are ribbons made of square pyramidal [(Pb,Sb)Se₅] groups running along [010].     

Synthesis and Structure Determination of Ag5HgSbO6, Comparison with AgHg3SbO6 and Ag5Pb2O6

From solid state reactions of Ag₂O, HgO, and Sb₂O₃ at high temperatures under elevated oxygen pressures a new silver mercury antimonate, Ag₅HgSbO₆, has been obtained. According to a single crystal structure determination Ag₅HgSbO₆ crystallizes in space group P$\bar{3}$ 1c (no. 163) with a = 5.9263(4), c = 12.3023(7) Å, V = 374.18(4) ų, Z = 2, 498 independent reflections, R1 = 0.030, wR2 = 0.059 (I ≥ 2 σ (I). Ag₅HgSbO₆ consists of HgSbO₆ layers, analogous to BiI_3, which are separated by Kagome nets formed by Ag⁺ ions. Perpendicular to these layers and along the c axis linear strings of Ag⁺ ions run through the large voids of the layers. Accordingly, Ag₅HgSbO₆ adopts the Ag₅Pb₂O₆ type of structure where the lead positions are occupied by mercury and antimony alternatingly. The finding of mercury in octahedral coordination, particularly besides the lower charged Ag⁺ cations in linear coordination, which is also highly preferred by Hg²⁺ ions, is rather unexpected. Ag₅HgSbO₆ starts to decompose at 450 °C and, in contrast to subvalent and metallic Ag₅Pb₂O₆, the new compound is charge balanced and semiconducting (ρ = 5.7 Ωcm at ambient temperature, E_a = 0.047 eV).     

Ferroelectric phase transitions in Pb2xSn2(1-x)P2Se6 system

Heat capacities of the Pb_2xSn_2(1-x)P₂Se₆ crystals (x=0, 0.098, 0.251, 0.402 and 1.0) were measured using an adiabatic calorimeter at temperatures between 10 and 350 K. In the crystal of x=0, two heat capacity anomalies corresponding to the ferroelectric commensurate - intermediate incommensurate(C-IC) phase transition temperature T _i, and the incommensurate - paraelectric (IC-N) phase transition temperature T _c, were observed at 193.24±0.10 and 220.07±0.15 K, respectively. The phase transition temperatures decreased with an increase in Pb²⁺ concentration. The anomaly at Ti disappeared at x=0.251 in the mixed systems of the Pb_2xSn_2(1-x)P₂Se₆. In the crystal of Pb₂P₂Se₆ (x=1.0), no phase transition was observed. The normal heat capacities for the mixed crystals were determined by least squares fitting of the Debye and Einstein functions to the experimental data. The anomalous heat capacities gave the phase transition entropies of 8.5 and 1.5 J mol^-1 K^-1 for x=0. The large transition entropies are consistent with an order-disorder mechanism in the ferroelectric-paraelectric phase transitions in x=0. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kronenetherkomplexe von Blei(II). Die Kristallstrukturen von [PbCl(18-Krone-6)][SbCl6], [Pb(18-Krone-6)(CH3CN)3][SbCl6]2, and [Pb(15-Krone-5)2][SbCl6]2

Crown Ether Complexes of Lead(II). The Crystal Structures of [PbCl(18-Krone-6)][SbCl₆], [Pb(18-Krone-6)(CH₃CN)₃][SbCl₆]₂ und [Pb(15-Krone-5)₂][SbCl₆]₂ . [PbCl(18-crown-6)][SbCl₆] has been prepared in low yield besides [Pb(CH₃)₂(18-crown-6)][SbCl₆]₂ by the reaction of Pb(CH₃)₂Cl₂ with antimony pentachloride in acetonitrile solution in the presence of 18-crown-6, forming pale-yellow crystals. The other two title compounds are formed as colourless crystals by the reaction of PbCl₂ with antimony pentachloride in acetonitrile solutions in the presence of 18-crown-6 and 15-crown-5, respectively. The complexes were characterized by IR spectroscopy and by crystal structure determinations. [PbCl(18-crown-6)][SbCl₆]: Space group P2₁/c, Z = 8, 5 003 observed unique reflections, R = 0.046. Lattice dimensions at - 80°C: a = 1 386.9; b = 1 642.7; c = 2 172.1 pm, β = 92.95°. The lead atom in the cation [PbCl(18-crown-6)]⁺ is surrounded in an almost hexagonal-planar construction by the six oxygen atoms of the crown ether and an axially oriented Cl atom. [Pb(18-crown-6)(CH₃CN)₃][SbCl₆]₂: Space group P1 , Z = 2, 6 128 observed unique reflections, R = 0.076. Lattice dimensions at - 70°C: a = 1 228.0; b = 1 422.9; c = 1 463.2 pm, α = 69.08°; β = 65.71°; γ = 64.51°. In the cation [Pb(18-crown-6)(CH₃CN)₃]²⁺ the lead atom is coordinated by the six oxygen atoms of the crown ether and by the three nitrogen atoms of the acetonitrile molecules. The structure determination is restricted by disorder. [Pb( 15-crown-5)₂][SbCI₆]₂: Space group P6₃/m, Z = 6, 5 857 observed unique reflections, R = 0.059. Lattice dimensions at -70°C: a = b = 2 198.5; c = 1499.4 pm, α = β = 90°, γ = 120°. In the cation [Pb(l5-crown-5)₂]² the lead atom is sandwich-like coordinated by the ten oxygen atoms of the two crown ether molecules. The structure determination is restricted by disorder.     

Neubestimmung der Kristallstrukturen der Hexahydroxometallate Na2Sn(OH)6, K2Sn(OH)6 und K2Pb(OH)6

Redetermination of the Crystal Structures of the Hexahydroxometallates Na₂Sn(OH)₆, K₂Sn(OH)₆, and K₂Pb(OH)₆ Slow cooling down of hot saturated hydroxo stannate‐ resp. ‐plumbate solutions gives crystals of Na₂Sn(OH)₆, K₂Sn(OH)₆, and K₂Pb(OH)₆ well suited for an X‐ray structure determination. With these crystals the so far known crystal data were verified, determined more precisely and H‐positions found for the first time. The compounds crystallize rhombohedral in the space group R 3. The hexagonal unit cells contain three formula units with Na₂Sn(OH)₆: a = 5.951(1) Å, c = 14.191(2) Å, c/a = 2.384 K₂Sn(OH)₆: a = 6.541(1) Å, c = 12.813(4) Å, c/a = 1.959 K₂Pb(OH)₆: a = 6.625(1) Å, c = 12.998(2) Å, c/a = 1.962 The compounds are not isotypic whereas the atoms occupy in all three cases the same Wyckoff positions. Na₂Sn(OH)₆ has with an hcp packing of O a CdI₂ like superstructure with Na and Sn in octahedral interstices. Hydrogen bonds O–H…O–H play a role in solid K₂Sn(OH)₆ and K₂Pb(OH)₆. In these compounds the potassium ions are shifted from an octahedral coordination in an hcp packing of O. They have nine nearest O‐neighbours. The hydrogen bonds are investigated by Raman spectroscopy.     

Synthesis and Structure of the Double Oxide Pb6Re6O19

Pb₆Re₆O₁₉ oxide has been synthesized in a sealed evacuted silica tube and by high-pressure high-temperature technique. Its crystal structure, refined from X-ray powder data (a = 9.3162(1) Å, space group Pn3, R_I = 0.021, R_p = 0.067), is based on a three-dimensional network of Re₂O₁₀ groups linked together by corner sharing. The short Re–Re separation inside the Re₂O₁₀ groups (2.45 Å) indicates the presence of a metal-metal bonding.     

Complexation in Binary Pb(II)–Dithiooxamide System in Pb2[Fe(CN)6] Gelatin-Immobilized Matrices

Complexation processes that occur when hexacyanoferrate(II) immobilized in gelatin is brought into contact with aqueous solutions of dithiooxamide at pH 12 are studied. Unlike the binary metal ion–dithiooxamide systems studied so far, the final product in this case was Pb(II) sulfide, rather than the Pb(II) complex with the indicated ligand. Concentration of Pb(II) sulfide was shown to depend on dithiooxamide concentration in a solution in contact with the matrix. A scheme for the complexation process is proposed.     

Fluorescence quenching of acridinium and 6-methoxyquinolinium ions by Pb2+, Hg2+, Cu2+, Ag+ and hydrogen sulphide

The quenching of the fluorescene of cationic derivatives of 6-methoxyquinoline and acridine by various heavy metal cations and hydrogen sulphide ion have been studied in detail. Stern—Volmer constants were determined and quenching was found to be exclusively dynamic, except for the hydrogen sulphide ion, which acts as both a dynamic and static quencher. The highly efficient static quenching process is interpreted in terms of nucleophilic attack of hydrogen sulphide to the 9-position of acridinium ion, thereby destroying the conjugated system of the fluorophore.     

400例6个月婴儿发铅水平分析

报道了在惠东县妇幼保健院出生及进行儿童保健系统管理的 4 0 0名 6个月婴儿发铅含量的调查分析。结果显示 ,4 0 0名 6个月婴儿发铅含量为 ( 1 1 1 6± 2 81 )× 1 0 -6。其中≥ 1 0 5×1 0 -6者有 2 35人 ,占分析人数的 5 8 75 %。男女之间的发铅水平无显著差异。纯母乳和人工喂养的婴儿发铅水平有显著差异。同时高发铅者的体重与正常发铅者体重有显著差异。通过对 6个月婴儿发铅的检测 ,可早期发现高发铅的婴儿 ,及时采用干预措施 ,这对预防儿童铅中毒及保障儿童正常的生长发育是非常重要的。     

Exploration of Pb2+ Selective Behavior of Calix[6]arene Ester Derivative

The selective behavior of calix[n]arene ester derivatives in two-phase extraction systems using polarographic technique has been investigated. Calix[4]arene tetraester derivative shows remarkable Na⁺ over Pb²⁺ selectivity; whereas calix[6]arene hexaester derivative shows Pb²⁺ over Na⁺ selectivity. The interference of some selected cations (Na⁺, K⁺, Cu²⁺ and Mg²⁺) were also examined and no significant effect on the selectivity behavior as well as extraction ability of these ionophores was found except Na⁺. The study reveals for the first time that the calix[6]arene hexaester derivative is highly Pb²⁺ selective ionophore and can be employed in the field of sensor as well as separation science and technology. The work also highlights the usefulness of polarographic technique in trace metal determination.     

Pb2PtO4, a new platinum-lead oxide with edge-shared PtO6 octahedral chains

Pb₂PtO₄ was prepared by the solid state reaction between lead monoxide and platinum metal in the appropriate ratio at 690–720°C. It decomposed to PbO and Pt at 735°C. The symmetry is orthorhombic: a = 9.115(4), b = 7.941(4), c = 6.306(4) Å, Z = 2, space group Pbam. The crystal structure was solved by conventional methods to R = 0.049 using 851 independent reflections. The structure consists of chains of edge-shared PtO₆ octahedra extending along the c-axis direction. Lead atoms are stacked in rows in the channels between the chains. The conductivity of Pb₂PtO₄ is low (σ(300 K) ⋍ 10⁻⁵ (Ω · cm)⁻¹), in agreement with the presence of fully oxidized tetravalent platinum.