Weak Pb Research Articles

Inhibited superoxide‐induced halide oxidation with a bioactive factor for stabilized inorganic perovskite solar cells

AbstractActive oxygen highly affects the efficiency and stability of perovskite solar cells (PSCs) owing to the capacity to either passivate defects or decompose perovskite lattice. To better understand the in‐depth interaction, we demonstrate for the first time that photooxidation mechanism in all‐inorganic perovskite film dominates the phase deterioration kinetics by forming superoxide species in the presence of light and oxygen, which is significantly different from that in organic‒inorganic hybrid and even tin‐based perovskites. In all‐inorganic perovskites, the superoxide species prefer to oxidize longer and weaker Pb‒I bond to PbO and I2, leaving the much stable CsPbBr3 phase. From this chemical proof‐of‐concept, we employ an organic bioactive factor, Tanshinone IIA, as a superoxide sweeper to enhance the environmental tolerance of inorganic perovskite, serving as a “skincare” agent for anti‐aging organisms. Combined with another key point on healing defective lattice, the best carbon‐based all‐inorganic CsPbI2Br solar cell delivers an efficiency as high as 15.12% and superior stability against oxygen, light, humidity, and heat attacks. This method is also applicable to enhance the efficiency of p‒i‒n inverted (Cs0.05MA0.05FA0.9)Pb(I0.93Br0.07)3 cell to 23.46%. These findings not only help us understand the perovskite decomposition mechanisms in depth but also provide a potential strategy for advanced PSC platforms.

Two-photon absorption of FAPbBr3 perovskite nanocrystals

Perovskite nanocrystals (NCs) with high two-photon absorption (TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr3 NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr3 NCs is studied. The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr3 NCs, which was around 2.76 × 10−45 cm4⋅s⋅photon−1 at 800 nm. In addition, temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr3 NCs was 69.668 meV, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr3 NCs in optoelectronic devices.

Three types of passivators on the stabilization of exogenous lead-contaminated soil with different particle sizes

Study on the form partitioning and content of heavy metals in soil particles with different sizes is crucial for preventing and controlling heavy metals pollution, but few studies regard soil contaminated by heavy metals as a homogeneous body. In this study (Fig. 1), goat manure, lime and phosphate were used to stabilize exogenous lead (Pb). These soil passivators’ differential effects on total Pb and Pb with different chemical forms in soil particles of different sizes as well as Pb immobilization in soil were investigated. By passivation experiment in laboratory for 45 days, the passivation effect of the single and combined application treatments on exogenous Pb and partitioning characteristics were analyzed and compared. The characterization method of fine sand microstructure and mineral composition analysis was used. The results showed that the single application of P5 and combined application of LP5 had optimum passivation efficiency. The content of DTPA-Pb was reduced with P5 by 65.27% and the percentage of available Pb decreased significantly in soil particles of the four sizes. The content of TCLP-Pb and available Pb (weak acid extraction and reducible Pb) significantly decreased by 71.60 and 25.12% respectively after the application of LP5 in the original soil. Furthermore, most of the total Pb was enriched in coarse sand and clay, while its content was lower in fine sand and silt. The combined application treatment of GL5 significantly increased the content of weak acid extractable and reducible Pb in fine sand, silty sand and clay. Through SEM and XRD analysis, it was found that the diffraction peak of P5 treatment groups might be related to the formation of insoluble Pb that contained compounds, which were mainly mineral components, including quartz, feldspar and mica, and LP showed a big potential in the study on passivation of heavy metal Pb-contaminated soil in the natural environment. In conclusion, further studies on the different dosage and metal-contamination levels as well as different combination forms of passivators should be considered under natural conditions, the selection of suitable passivators according to soil texture is of great significance for remediation of Pb-contaminated soil.

Determination of residual dimethyl sulfoxide by high-resolution continuum source graphite furnace molecular absorption spectrometry

High-resolution continuum source molecular absorption spectrometry (HR-CSMAS) has been extended to the determination of sulfur-containing organic molecule, on the example of dimethyl sulfoxide (DMSO) as a residual solvent in CH3NH3PbI3 perovskite thin films. For this purpose, DMSO molecules were converted into CS molecules by pyrolysis in a graphite furnace at low temperature and the sulfur content was determined by measuring molecular absorption of CS at 258.055 nm. An aqueous solution of DMSO was used for calibration. A characteristic mass of 17 ng was achieved for S after pyrolysis at 160 °C by using Pd as a chemical modifier. Furthermore, the content of DMSO was normalized to that of Pb whereas the content of Pb was determined by reducing the Pb in the perovskite to metallic Pb with Zn powder and measuring absorption of the weak Pb line at 261.418 nm by high-resolution continuum source atomic absorption spectrometry (HR-CSAAS). The Pb content remained constant whereas the S/Pb molar ratio decreased with increasing annealing time. Our results open new opportunities for the characterization of residual DMSO in wide classes of materials.

From Decompression Melting to Mantle-Wedge Refertilization and Metamorphism: Insights from Peridotites of the Alag Khadny Accretionary Complex (SW Mongolia)

This study reports on mineral and bulk rock compositions of metaperidotites from the Alag Khadny accretionary complex in SW Mongolia, to reveal their nature and relationships with associated eclogites. The peridotites preserved original porphyroclastic textures and are composed of olivine, orthopyroxene relics, Cr-spinel, interstitial (not residual) clinopyroxene, and secondary chlorite, tremolite, olivine, Cr-magnetite, clinopyroxene, and antigorite. Cr-spinel has Cr# of 0.3–0.5, and primary olivine shows Mg# of 0.90–0.92. The pyroxenes are high-magnesian with low Al2O3 and Cr2O3. The bulk rocks have U-shaped normalized trace-element patterns with enrichment in LILE, L-MREE relative to HREE, and weak Pb–Sr peaks and Nb–Zr–Hf minima. Interstitial clinopyroxene exhibits V- and U-shaped normalized REE patterns with (La/Yb)N > 1 (Yb = 1.2–3 of chondritic values) and enrichment in fluid-mobile elements and Zr. HREE abundances of clinopyroxene can be simulated by 23–26% partial melting of depleted mantle starting at garnet-facies (6–8%) depths, followed by hydrous or anhydrous melting at spinel-facies depths L-MREE characteristics of clinopyroxenes can be simulated by further interaction of harzburgites with an island-arc basaltic melt in a supra-subduction environment. The association of hydrous secondary minerals in the Alag Khadny peridotites suggests their retrograde metamorphism at 1.6–2.0 GPa and 640–720 °C, similar to P–T conditions reported earlier for the spatially associated eclogites. This supports metamorphism of the Alag Khadny peridotites in a mantle wedge, followed by joint exhumation of peridotites and eclogites. Given the findings above and implying the regional geological background, we advocate for a sequential Neoproterozoic evolution the Alag Khadny harzburgites from (1) their formation by decompression partial melting in an Early Neoproterozoic or older spreading center of a mid-ocean or back-arc setting, and (2) refertilization by supra-subduction melts, followed by (3) Late Neoproterozoic–Early Cambrian hydrous-fluid metamorphism and juxtaposition with eclogites.

Langhofite, Pb2(OH)[WO4(OH)], a new mineral from Långban, Sweden

AbstractLanghofite, ideally Pb2(OH)[WO4(OH)], is a new mineral from the Långban mine, Värmland, Sweden. The mineral and its name were approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2019-005). It occurs in a small vug in hematite–pyroxene skarn associated with calcite, baryte, fluorapatite, mimetite and minor sulfide minerals. Langhofite is triclinic, space group P$\bar{1}$, and unit-cell parameters a = 6.6154(1) Å, b = 7.0766(1) Å, c = 7.3296(1) Å, α = 118.175(2)°, β = 94.451(1)°, γ = 101.146(1)° and V = 291.06(1) Å3 for Z = 2. The seven strongest Bragg peaks from powder X-ray diffractometry are [dobs, Å (I)(hkl)]: 6.04(24)(010), 3.26(22)(11$\bar{2}$), 3.181(19)(200), 3.079(24)(1$\bar{1}$2), 3.016(100)(020), 2.054(20)(3$\bar{1}$1) and 2.050(18)(13$\bar{2}$). Langhofite occurs as euhedral crystals up to 4 mm, elongated along the a axis, with lengthwise striation. Mohs hardness is ca. 2½, based on VHN25 data obtained in the range 130–192. The mineral is brittle, with perfect {010} and {100} cleavages. The calculated density based on the ideal formula is 7.95(1) g⋅cm–3. Langhofite is colourless to white (non-pleochroic) and transparent, with a white streak and adamantine lustre. Reflectance curves show normal dispersion, with maximum values 15.7–13.4% within 400–700 nm. Electron microprobe analyses yield only the metals Pb and W above the detection level. The presence of OH-groups is demonstrated with vibration spectroscopy, from band maxima present at ~3470 and 3330 cm–1. A distinct Raman peak at ca. 862 cm–1 is related to symmetric W–oxygen stretching vibrations. The crystal structure is novel and was refined to R = 1.6%. It contains [W2O8(OH)2]6– edge-sharing dimers (with highly distorted WO6-octahedra) forming chains along [101] with [(OH)2Pb4]6+ dimers formed by (OH)Pb3 triangles. Chains configure (010) layers linked along [010] by long and weak Pb–O bonds, thus explaining the observed perfect cleavage on {010}. The mineral is named for curator Jörgen Langhof (b. 1965), who collected the discovery sample.

Identifying Phase-Dependent Electrochemical Stripping Performance of FeOOH Nanorod: Evidence from Kinetic Simulation and Analyte-Material Interactions.

Metal hydroxide nanomaterials are widely applied in the energy and environment fields. The electrochemical performance of such materials is strongly dependent on their crystal phases. However, as there are always multiple factors relating to the phase-dependent electrochemistry, it is still difficult to identify the determining one. The well-defined crystal phases of α- and β-FeOOH nanorods are characterized through the transmission electron microscopy by a series of rotation toward one rod, where the cross-section shape and the growth direction along the [001] crystalline are first verified for 1D FeOOH nanostructures. The electrosensitivity of the two materials toward Pb(II) is tested, where α-FeOOH performs an outstanding sensitivity whilst it is only modest for β-FeOOH. Experiments via Fourier transform infrared spectroscopy, X-ray absorption fine structure (XAFS), etc., show that α-FeOOH presents a larger Pb(II) adsorption capacity due to more surficial hydroxyl groups and weaker PbO bond strength. The reaction kinetics are simulated and the adsorption capacity is found to be the determining factor for the distinct Pb(II) sensitivities. Combining experiment with simulation, this work reveals the physical insights of the phase-dependent electrochemistry for FeOOH and provides guidelines for the functional application of metal hydroxide nanomaterials.

Elastic and electronic origins of strain stabilized photovoltaic γ-CsPbI3.

All-inorganic cesium lead triiodide (CsPbI3) perovskite has been widely researched due to its outstanding photovoltaic properties. At room temperature, there are two orthorhombic CsPbI3 phases (black γ-CsPbI3 perovskite and yellow δ-CsPbI3 non-perovskite). In this study, these two polymorphic structures have been studied via density functional theory calculations in respect to their electronic and elastic properties. Our calculation results give full mapping of Young's moduli of the γ-CsPbI3 structure for all crystallographic orientations, which reveal that the optimum directions for stabilizing the γ-CsPbI3via strain are approximately along 〈012〉. Moreover, we found that these two polymorphs have distinct stiffness along respective octahedral chains due to their different kinds of octahedral connections. Furthermore, the calculated band structures and density of states disclose that both phases have direct bandgaps, and the bandgap of δ-CsPbI3 is much wider due to its weak Pb 6p-I 5p antibonding coupling in the conduction band and low octahedral connectivity. Our findings provide fundamental elastic and electronic insights which are instructive for strain engineering of photovoltaic γ-CsPbI3.

Winter chemical partitioning of metals bound to atmospheric fine particles in Dongguan, China, and its health risk assessment

To analyze the relationship between nanoparticles and the chemical forms in an urban atmospheric environment, metallic particles with different diameters were collected using a nanoparticle sampling system and analyzed for chemical and morphological characteristics, bioactivity, and the risk of carcinogenic and non-carcinogenic effects. The source of the atmospheric particles was analyzed based on the enrichment factor method, and the carcinogenicity of the atmospheric particles was analyzed using the health risk model. The partition contents of metals extractable by a weak acid, including As, Ca, Cd, Cs, Pb, Sr, and Zn, were in a range of 32.17–71.4%, with an average value of 47.07%. The content of oxides and reducible metals of all of the elements was generally low. Potassium was distributed mainly in the residual and weak-acid-extractable fractions. Barium had a high proportion of the oxidation state. Each fraction of Zn was basically the same, while the content of the weak-acid-extractable fraction was slightly higher. We found bio-access potential to be positively correlated with a high proportion of the weak acid extracts such as Mg, Sr, and Zn. We also found there to be a large weak-acid-extractable fraction (F1) and residual fraction (F4) and relatively enriched elements and strongly enriched elements, which means F1 and F4 may be the cause of enrichment. The hazard index (HI) and the total cancer risk (TCR) were far beyond the safety threshold when the diameter of the particle was in the range of 0.1–0.5 μm, indicating that the residents in Dongguan city were experiencing obvious non-carcinogenic and carcinogenic risks.

Somersetite, Pb8O(OH)4(CO3)5, a new complex hydrocerussite-related mineral from the Mendip Hills, England

ABSTRACTThe new mineral somersetite, has been found at Torr Works (‘Merehead quarry’) in Somerset, England, United Kingdom. Somersetite is green or white (typically it is similar visually to hydrocerussite-like minerals but with a mint-green tint), forms plates and subhedral grains up to 5 mm across and up to 2 mm thick. In bi-coloured crystals it forms very thin intergrowths with plumbonacrite. The empirical formula of somersetite is Pb8.00C5.00H4.00O20. The simplified formula is Pb8O(OH)4(CO3)5, which requires: PbO = 87.46, CO2= 10.78, H2O = 1.76, total 100.00 wt.%.The infrared spectrum of somersetite is similar to that of plumbonacrite and, to a lesser degree, hydrocerussite. Somersetite is hexagonal,P63/mmc,a= 5.2427(7),c= 40.624(6) Å,V= 967.0(3) Å3andZ= 2. The eight strongest reflections of the powder X-ray diffraction (XRD) pattern [d,Å(I)(hkl)] are: 4.308(33)(103), 4.148(25)(104), 3.581(40)(107), 3.390(100)(108), 3.206(55)(109), 2.625(78)(110), 2.544(98)(0.0.16) and 2.119(27)(1.0.17). The crystal structure was solved from single-crystal XRD data givingR1= 0.031. The structure of somersetite is unique and consists of the alternation of the electroneutral plumbonacrite-type [Pb5O(OH)2(CO3)3]0and hydrocerussite-type [Pb3(OH)2(CO3)2]0blocks separated by stereochemically active lone electron pairs on Pb2+. There are two blocks of each type per unit cell in the structure, which corresponds to the formula [Pb5O(OH)2(CO3)3][Pb3(OH)2(CO3)2] or Pb8O(OH)4(CO3)5in a simplified representation. The 2Dblocks are held together by weak Pb–O bonds and weak interactions between lone pairs.

Two New 3-D Lead(II) Coordination Polymers of Glycolic Acid with Luminescent Properties

Two new 3-D lead(II) coordination polymers [PbL]n (1, L = glycolic acid) and [Pb4L2L′2CdBr2]n (2, L′ = ethylene glycol) have been solvothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single crystal X-ray diffraction. 1 contains 1-D neutral [PbL]n chain with hemidirected tetrahedral geometry, which is further connected by weak Pb···O interactions to produce a 3-D network. 2 contains another 1-D neutral [Pb2LL′]n chain with hemidirected tetrahedral/trigonal–pyramidal geometry that is converted into 2-D neutral [Pb4L2L′2]n layer via weak Pb···O interactions. The layers of 2 are further bridged by unsaturated [CdBr2] complexes to form a 3-D heterobimetallic [Pb4L2L′2CdBr2]n framework. The L ligand of both 1 and 2 resulted from in-situ oxidation of L′ ligand during the solvothermal reaction. 2 represents the rare example of 3-D heterometallic organic framework based on the linkages of 2-D lead(II) carboxylates and cadmium(II) bromides. Their luminescent properties in the solid state and density functional theory calculations have been investigated.

Syntheses, crystal structures and fluorescent properties of three metal- tris(4′-carboxybiphenyl)amine frameworks

Triphenylamine and its derivatives have been widely concerned because of their excellent performance in the area of the photoelectric functional material. In this work, we chose a nanosized tris(4′-carboxybiphenyl)amine (H3TPA) as organic ligand. By employing the H3TPA ligand to assemble with M2+ (M = Zn, Cd, and Pb) ions, respectively, three metal-organic frameworks (FIR-43 to FIR-45, FIR denotes Fujian Institute of Research) have been synthesized under different solvent systems. FIR-43 exhibits a 3-connected two-dimensional (2D) network based on mononuclear [Zn(COO)3] second building unit (SBU). Unlike the anionic framework FIR-43, FIR-44 is a neutral 2D layer constructed by trinuclear [Cd3(COO)6] SBU and displays a (3,6)-NbSe2 topology structure. If the weak Pb–O interactions in the range of 2.79–2.88Å are considered, FIR-45 is a neutral 3D framework built by hexanuclear [Pb6(DMAE)6(COO)6] SBU (DMAE = N,N-dimethylethanolamine) and represents a (3,6)-connected (4·82)2(42·811·102) topology. Thermogravimetric analyses (TGA) and X-ray powder diffraction (PXRD) patterns were used to evaluate their thermal stability and phase purity. Photoluminescence studies showed that they exhibited strong emitting bands in the visible region with high quantum yields and long luminescent lifetimes.

The Lone-Pair Stereochemistry and Its Effect on Supramolecular Interaction of Dinuclear Pb(II) Dicarboxylate Compound With 2,6-Bis(benzimidazolyl)pyridine

A dinuclear Pb(II) dicarboxylate compound with 2,6-bis(benzimidazolyl)pyridine has been synthesized under hydrothermal condition. Single-crystal X-ray diffraction analysis shows that the arrangement of the half deprotonated H2bbp ligand and carboxylate groups displays a coordination gap around the Pb(II) ion, occupied possibly by a stereoactive lone pair of electrons on Pb(II) ion, the coordination environment around the lead atoms being hemidirected. The coordination sphere of a unique dinuclear Pb(II) complex is controlled by lone pair activity, weak Pb···O interactions, π-π interaction, and the hydrogen bond. Strong bathochromic shift effect on the solution and solid-state photoluminescence of complex is influenced by the above weak interactions. CCDC: 841895.

Crystal structure of tetra-kis-[μ2-2-(di-methyl-amino)-ethano-lato-κ(3) N,O:O]di-μ3-hydroxido-di-thio-cyanato-κ(2) N-dichromium(III)dilead(II) di-thio-cyanate aceto-nitrile monosolvate.

The tetra-nuclear complex cation of the title compound, [Cr2Pb2(NCS)2(OH)2(C4H10NO)4](SCN)2·CH3CN, lies on an inversion centre. The main structural feature of the cation is a distorted seco-norcubane Pb2Cr2O6 cage with a central four-membered Cr2O2 ring. The Cr(III) ion is coordinated in a distorted octa-hedron, which involves two N atoms of one bidentate ligand and one thio-cyanate anion, two μ2-O atoms of 2-(di-methyl-amino)-ethano-late ligands and two μ3-O atoms of hydroxide ions. The coordination geometry of the Pb(II) ion is a distorted disphenoid, which involves one N atom, two μ2-O atoms and one μ3-O atom. In addition, weak Pb⋯S inter-actions involving the coordinating and non-coordinating thio-cyanate anions are observed. In the crystal, the complex cations are linked through the thio-cyanate anions via the Pb⋯S inter-actions and O-H⋯N hydrogen bonds into chains along the c axis. The chains are further linked together via S⋯S contacts. The contribution of the disordered solvent aceto-nitrile mol-ecule was removed with the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] procedure in PLATON. The solvent is included in the reported mol-ecular formula, weight and density.

Extending the family of stable heavier carbenes: New tetrylenes based on N,N,O-ligands

A series of novel heavier carbene analogs 3–8, MeN(CH2CH2NTs)(CH2CR2O)M (M=Ge (3, R=H; 4, R=Ph), Sn (5, R=H; 6, R=Ph), Pb (7, R=H; 8, R=Ph)), was prepared by the interaction of M[N(SiMe3)2]2 (M=Ge, Sn, Pb) with substituted N,N,O-ligands, 1 and 2, MeN(CH2CH2NHTs)(CH2CR2OH) (1, R=H; 2, R=Ph). All the compounds were investigated by IR and multinuclear NMR spectroscopy and it was established that in a solution tin and lead compounds are agglomerated. An X-ray diffraction analysis of 3 revealed the monomeric structure with three-coordinated Ge atom. In contrast to germylenes, plumbylenes are associated in solid state. In the crystalline phase, the steric hindrance affects the degree of association. Thus, lead derivative 7 based on unsubstituted ligand, 1, forms dimers with strong bridging Pb–O bonding which further crystallize into chains. On contrary, plumbylene 8 based on phenyl substituted ligand, 2, is monomeric and only weak Pb⋯OSO contacts are observed is the solid state.

Formation of Zn(ii) and Pb(ii) coordination polymers of tetrakis(4-pyridyl)cyclobutane controlled by benzene and toluene

Reactions of Zn(NO3)2·6H2O with tetrakis(4-pyridyl)cyclobutane (tpcb) in MeOH followed by addition of benzene or toluene gave rise to two two-dimensional (2D) coordination polymers {[Zn(tpcb)(NO3)2]·2S}n (1: S = benzene; 2: S = toluene). The analogue reactions of Pb(NO3)2 with tpcb in similar solvent systems resulted in the formation of {[Pb(tpcb)0.5(NO3)2(MeOH)]·benzene}n (3) and [Pb(tpcb)(NO3)2(MeOH)]n (4), respectively. Slow evaporation of the MeOH solution containing Pb(NO3)2 and tpcb generated [Pb(tpcb)(NO3)2(H2O)]n (5). Compounds 1 and 2 show similar 2D networks but differ in their packing modes, namely “overlapping” and “crisscross” modes. Compound 3 exhibits a 3D porous framework in which its 1D channels are occupied by benzene molecules. Compound 4 consists of 1D [Pb(tpcb)(NO3)2(MeOH)]n chains which are linked by weak Pb⋯N secondary interactions to form a 2D gridlike network. Compound 5 has a 3D structure constructed by dinuclear [Pb2(tpcb)6(NO3)4(H2O)2] units and tpcb bridges with a Schlafli symbol of (4·62)·(42·610·82). The solvent effects may be ascribed to the formation of the five 2D and 3D coordination polymers 1–5. The inclusion of benzene and toluene molecules in the frameworks of 1 and 2 along with the time lengths of their crystal growth may provide an interesting approach to the selective separation of benzene and toluene.

BACKITE, Pb2Al(TeO6)Cl, A NEW TELLURATE MINERAL FROM THE GRAND CENTRAL MINE, TOMBSTONE HILLS, COCHISE COUNTY, ARIZONA: DESCRIPTION AND CRYSTAL STRUCTURE

Abstract Backite, Pb 2 Al(TeO 6 )Cl, is a new tellurate mineral from the Grand Central mine, Tombstone Hills, Cochise County, Arizona. It occurs as rosettes of hexagonal plates perched on microcrystalline quartz, associated with schieffelinite, oboyerite, and rodalquilarite. Backite is dark to pale blue-grey, moderately transparent with opacity increasing with intensity of color, has a very pale bluish-grey streak, an adamantine luster, and does not fluoresce under ultraviolet light. It has a perfect micaceous cleavage parallel to {001}. Mohs hardness is 2–3, and backite is brittle with a splintery fracture. The calculated density is 5.573 g/cm 3 . The indices of refraction are greater than 1.80, and grains are pleochroic in shades of blue-grey. Backite is trigonal, space group P 312, a 5.0441(7), c 9.4210(5) A, V 205.58(8) A 3 , Z = 1, c:a = 1:1.868. The six strongest lines in the X-ray powder diffraction pattern are as follows: d (A), I , ( h k l ): 3.193, 100, (012); 4.363, 55, (010); 2.521, 55, (013, 120); 1.555, 35, (132, 122); 1.978, 28, (022); 1.715, 20, (015, 124, 114). Chemical analysis by electron microprobe gave TeO 3 24.05, Al 2 O 3 7.07, PbO 63.74, S 1.15, Cl 2.28, O + Cl −1.09, sum 97.20 wt.% where the valence states of Te, Pb, and S were determined by crystal-structure analysis. The resulting empirical formula on the basis of 6 O anions is Pb 2.05 Al 1.00 Te 0.98 O 6 (Cl 0.46 S 0.26 ) and the endmember formula is Pb 2 AlTeO 6 Cl. The crystal structure of backite was solved by direct methods and refined to an R 1 index of 4.20% based on 422 observed reflections collected with a three-circle rotating-anode diffractometer using Mo K α X-radiation. In the structure of backite, Te and Al octahedra occupy the vertices of a 6 3 net and each octahedron shares three edges with three adjacent octahedra. These layers of octahedra repeat along the c direction and are linked by a thick slab of lone-pair stereoactive Pb 2+ cations and Cl − anions. The structure is held together in the c direction by long, weak Pb–Cl bonds, accounting for the perfect cleavage parallel to {001}.

Influence of the steric effect of flexible isomeric phenylenediacetic acids on the resultant lead(II) coordination polymers

To study the steric effect of the flexible dicarboxylate ligands on the resultant formations of coordination polymers (CPs), four new PbII CPs [Pb(1,2-pda)(H2O)]n (1), [Pb(1,3-pda)]n·nH2O (2), [Pb2(1,4-pda)2(H2O)]n·2nH2O (3a and 3b) have been produced by the isomeric phenylenediacetic acids (H2pda). The X-ray crystallography study reveals that CP 1 is a two-dimensional (2D) 4-connected sql (44.62) network via the weak Pb···O interactions built on 1D chain-like structure. CP 2 crystallizes in orthorhombic system with chiral space group P212121, showing a 4-connected sra (42.63.8) framework where a left-handed helical motif is formed by PbII ions and trans-1,3-pda ligands. More interestingly, CPs 3a and 3b are two true 3D polymorphs and have the different morphology. Topologically, the framework of 3a exhibits a 4-connected lon 66 motif, while that of 3b is a (4,6)-connected fsh (43.63)2(46.66.83) net. It is found that the three isomeric pda anions display the various coordination fashions in four CPs. The different structural arrangements show that the steric effect of the isomeric H2pda tectons has a positive role in directing the final products of PbII CPs. Also, the fluorescent properties of the CPs were studied in the solid state at room temperature.

Crystal structure of a novel synthetic compound, Pb2O(OH)I, and structure refinement of ‘iodolaurionite’, Pb(OH)I: hydroxo- and oxocentred units in Pb minerals and synthetic compounds

AbstractYellow needles of 'iodolaurionite', Pb(OH)I, and a novel compound Pb2O(OH)I, have been prepared by hydrothermal reactions of PbO and PbI2 at 170°C. The crystal structure of 'iodolaurionite', Pb(OH)I (orthorhombic,Pnma,a= 7.8244(8),b= 4.2107(4),c= 10.4724(10) Å,V= 345.03(6) Å3,Z= 4) has been refined toR1= 0.041 for 129 independent observed reflections. The structure is based on the OHPb3triangles sharing common edges to produce single [OHPb]+ chains extending along thebaxis and parallel to theabplane. The three-dimensional integrity of the structure is provided by the Pb–I bonds and the O–H···I hydrogen bonding. The structure is isotypic with that of laurionite, Pb(OH)Cl. The crystal structure of Pb2O(OH)I (monoclinic,C2/m,a= 13.711(3),b= 4.0975(10),c= 9.584(2) Å, β = 110.64(1)°,V= 503.9(2) Å3,Z= 4), has been solved by direct methods and refined toR1= 0.053 for 586 independent observed reflections. In the structure of Pb2O(OH)I, O(1)Pb4 tetrahedra link together by sharing edges and corners to form [OPb2]2+chains similar to those observed in sidpietersite. The O(2) atoms belong to hydroxyl groups attached to both sides of the chains to produce novel [O(OH)Pb2]+1D units. The [O(OH)Pb2]+units are extended parallel to thebaxis and lie within thebcplane. The [O(OH)Pb2]+units are linked together via hydrogen bonding in the (100) plane and by weak Pb–I bonds in the [100] direction. The [O(OH)Pb2]+ bands can be obtained from the [OPb] layer of OPb4tetrahedra present in the structure of tetragonal PbO (litharge). The continuous [OPb] layer has to be broken into [O2Pb2] bands containing 3- and 4-coordinated O atoms in the 1:1 ratio with subsequent protonation of the 3-coordinated O sites. Relations of Pb(OH)I and Pb2O(OH)I to known Pb hydroxy- and oxyhalides are described briefly.

Tin and lead phosphinothiolate derivatives. Crystal structures of [Ph3Sn{Ph2PC6H4S-2}], [Sn{PhP(C6H4S-2)2}2] and [Pb{Ph2P(O)C6H4S-2}2]·1/2CH3OH·2H2O complexes

The coordination capability of the phosphinothiol ligands Ph2PC6H4SH-2 and PhP(C6H4SH-2)2, towards two organotin (Ph3SnCl, Ph2SnCl2) and the organolead Ph2PbCl2 was studied. The complexes were characterized by microanalysis, FAB mass spectrometry, IR and NMR spectroscopy. Also, crystal structures of [Ph3Sn{Ph2PC6H4S-2}], [Sn{PhP(C6H4S-2)2}2] and [Pb{Ph2P(O)C6H4S-2}2]·1/2CH3OH·2H2O complexes have been determined. The structure of [Ph3Sn{Ph2PC6H4S-2}] complex shows the triphenyltin fragment coordinated to one monoanionic phosphinothiol ligand acting as monodentate through the thiolate sulfur atom with the tin ion in a tetrahedral environment. The crystal structure of [Sn{PhP(C6H4S-2}2] shows the metal ion in a distorted octahedral geometry. The geometry about the Pb in [Pb{Ph2P(O)C6H4S-2}2]·1/2CH3OH·2H2O complex is best described as distorted ψ−trigonal bipyramidal with the five position occupied by the active lone pair of metal. Intermolecular weak Pb-(η6-C6H5) interactions between the lead electron pair and phenyl rings are also observed.