High-yield preparation of rod-like CaSO<Subscript>4</Subscript>/Fe<Superscript>0</Superscript> magnetic composite for effective removal of Cu<Superscript>2+</Superscript> in wastewater

In this study, a simple approach was described for the fabrication of CaSO₄/Fe⁰ composite used as a novel adsorbent for the reductive removal of Cu²⁺ from aqueous solutions. The magnetic CaSO₄/Fe⁰ composite was prepared by a solid state reaction at 550 °C in the H₂ atmosphere using CaSO₄·2H₂O/α-FeOOH as a precursor. The structure and morphology of the as-synthesized magnetic composite were characterized by X-ray diffraction, field emission scanning electron microscopy and a superconducting quantum interference device, respectively. Results showed that the CaSO₄/Fe⁰ composite with a rod-like shape could be easily acquired from the CaSO₄·2H₂O/α-FeOOH precursor with the ratio of 1:0.5 at 550 °C in the H₂ atmosphere for 1 h. The CaSO₄/Fe⁰ composite exhibited enhanced performance relevant to the reductive removal of Cu²⁺. The removal amount of Cu²⁺ increased linearly with increasing of concentration of Cu²⁺ in wastewater. Possible removal mechanisms were proposed as follows: (1) the formation of Cu₂O by fast reduction of Cu²⁺ with Fe⁰ nanoparticles on interface of CaSO₄/Fe⁰ composite, (2) proper adsorption of Cu²⁺ on the surface of CaSO₄/Fe⁰ composite, (3) the hydrous iron oxide (HIO) such as Fe (OH)₃ and FeOOH in situ generated on the rest of CaSO₄/Fe⁰ composite could further adsorb Cu²⁺ from wastewater.     

Structure and some properties of [UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(C<Subscript>5</Subscript>H<Subscript>12</Subscript>N<Subscript>2</Subscript>O)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]

The complex [UO₂(SeO₄)(C₅H₁₂N₂O)₂(H₂O)] (I) was synthesized and studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are orthorhombic: a = 13.1661(3) Å, b = 16.4420(5) Å, c = 17.4548(6) Å, Pbca, Z = 8, R = 0.0423. The structural units of crystal I are chains with the composition coinciding with that of the compounds of the AB₂M ₃ ¹ crystal chemical group of the uranyl complexes (A = UO ₂ ²⁺ , B² = SeO ₄ ^2? , M¹ = C₅H₁₂N₂O and H₂O).     

Crystal and molecular structure of [Au(C<Subscript>14</Subscript>H<Subscript>24</Subscript>N<Subscript>4</Subscript>)][H<Subscript>3</Subscript>O](ClO<Subscript>4</Subscript>)<Subscript>4</Subscript>

The crystal and molecular structure of doubly protonated tetraazamacrocyclic complex of gold(III) [Au(C₁₄H₂₄N₄)][H₃O](ClO₄)₄ has been determined. The crystals are monoclinic: a = 11.158(2) Å, b = 8.243(1) Å, c = 14.756(2) Å; β = 98.65(1)°, V = 1341.8(3) ų, Z = 2, ρ(calc) = 1.134 g/cm³, space group P2₁/n. The structure is built of almost flat centrosymmetrical Au(C₁₄H₂₄N₄)]³⁺ and [H₃O]⁺ cations and [ClO₄]^? anions. The gold atom is coordinated with four nitrogen atoms of the ligand forming a flat square. The coordinated ligand is protonated at its γ-carbon atoms of the two six-membered chelate rings. The Au-N bond lengths are almost identical (the mean value is 1.994 Å). The six-membered rings of the complex contain C=N diimine bonds. The [H₃O]⁺ oxonium ion has H-bonds with the oxygen atoms of perchlorate ions.     

Reactivity of triangular oxalate cluster complexes [M<Subscript>3</Subscript>Q<Subscript>7</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>3</Subscript>]<Superscript>2−</Superscript> (M = Mo or W; Q = S or Se)

The reactions of the oxalate complexes [M₃Q₇(C₂O₄)₃]²⁻ (M = Mo or W; Q = S or Se) with Mn^II, Co^II, Ni^II, and Cu^II aqua and ethylenediamine complexes in aqueous and aqueous ethanolic solutions were studied. The previously unknown heterometallic complexes [Mo₃Se₇(C₂O₄)₃Ni(H₂O)₅]·3.5H₂O (1) and K₃{[Cu(en)₂H₂O]([Mo₃S₇(ox)₃]₂Br)}·5.5H₂O (2) were synthesized. In these complexes, the oxalate clusters serve as monodentate ligands. The K(H₂en)₂[W₃S₇(C₂O₄)₃]₂Br·4H₂O salt (3) was isolated from solutions containing Co^II, Ni^II, or Cu^II aqua complexes and ethylenediamine. The reaction of [Mo₃Se₇(C₂O₄)₃]²⁻ with HBr produced the bromide complex [Mo₃Se₇Br₆]²⁻, which was isolated as (Bu₄N)₂[Mo₃Se₇Br₆] (4). Complexes 1–3 were characterized by X-ray diffraction, IR spectra, and elemental analysis. The formation of 4 was detected by electrospray mass spectrometry. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1645–1649, September, 2007.     

Crystal structures of copper(II) complexes with methyliminodiacetate ions and 1,10-phenanthroline or imidazole [Cu(Phen)H<Subscript>2</Subscript>O][Cu(Mida)<Subscript>2</Subscript>]·2H<Subscript>2</Subscript>O and [Cu(Mida)Im]

Methyliminodiacetic acid (H₂Mida) and imidazole react with copper(II) to form crystals of the square pyramidal complex [Cu(Mida)Im]. One N and two O atoms of the Mida ligand (Cu-N 2.010(1) Å, Cu-O 1.955(1) Å, and 1.978(1) Å) and the imidazole N atom (1.950(1) Å) lie at the base of the pyramid. The carboxyl O atom of the neighboring complex lies at the apical position (2.411(1) Å); in this way the individual complexes are linked into infinite zigzag chains. Substitution of imidazole by 1,10-phenanthroline gave [Cu₂(Mida)₂(Phen)H₂O]·2H₂O crystals with two nonequivalent centrosymmetric octahedral anions [Cu(Mida)₂]^2? of face type (Cu-N 2.023 Å and 2.028(2) Å, Cu-O_ax 2.579 Å and 2.530(2) Å, Cu-O_bas 1.952 Å and 1.936(2) Å). The anions serve as bridges in chains between the [Cu(Phen)H₂O]²⁺ cation fragments to which they are bonded by their axial carboxyl groups. The Cu atom of the cation has a [4+1] environment (with the H₂O molecule lying on the axis of the pyramid, and with two N atoms of the ligand and two O atoms of the anions lying at the base).     

Structure of arsenic 8-mercaptoquinolinate: Synthesis and crystal structure of arsenic 4-methoxy-8-mercaptoquinolinate As[C<Subscript>9</Subscript>H<Subscript>5</Subscript>(OCH<Subscript>3</Subscript>)NS]<Subscript>3</Subscript>

Arsenic 4-methoxy-8-mercaptoquinolinate As[C₉H₅(4-OCH₃)NS]₃ (I) was synthesized and studied by X-ray diffraction. Crystals are trigonal: space group R3, a = b = 13.9867(4) Å, c = 12.4991(5) Å, γ = 120°, V = 2117.58(12) ų, ρ = 1.519 g/cm³, Z = 3. An arsenic atom in the crystal structure occupies a special position on axis 3. The structural unit of the crystal (neutral complex I) has symmetry C3. 4-Methoxy-8-mercaptoquinoline acts as a bidentate (N,S-) ligand. The coordination polyhedron of the arsenic atom is a symmetric octahedron (3S + 3N) or, with allowance for the lone electron pair, ψ-one-capped octahedron (3S + 3N + E). Bond lengths are as follows: As-S, 2.3179(7)Å; As…N 2.688(3) Å. The geometries of coordination polyhedra of arsenic atoms are compared in the crystal structures of As(C₉H₆NS)₃, As[C₉H₅(2-CH₃)NS]₃, and As[C₉H₅(4-CH₃)NS]₃.     

Effect of active impurities on the condensation of nanoparticles from supersaturated carbon vapor in the combined laser photolysis of C<Subscript>3</Subscript>O<Subscript>2</Subscript> and H<Subscript>2</Subscript>S

The effect of active H₂S, HS^·, and atomic hydrogen impurities on the condensation of highly supersaturated carbon vapor obtained in the combined laser photolysis of a mixture of C₃O₂ and H₂S diluted with argon was studied. The concentrations of carbon vapor, HS^·, and atomic hydrogen obtained in the laser photolysis of the mixture were determined using the absorption cross sections of C₃O₂ and H₂S molecules measured in this work and the measured amount of absorbed laser radiation. The time profiles of the sizes of growing nanoparticles synthesized in C₃O₂ + Ar and C₃O₂ + H₂S + Ar mixtures were measured using the laser-induced incandescence (LII) method. An improved LII model was developed, which simultaneously took into account the heating and cooling of nanoparticles and the temperature dependence of the thermophysical properties of nanoparticles, as well as the cooling of nanoparticles by evaporation and thermal emission. The size distributions of carbon nanoparticles formed in the presence and absence of active impurities were determined with the use of a transmission electron microscope. The final average size of carbon nanoparticles was found to decrease from 12 to 9 nm upon the addition of H₂S to the system, whereas the rate of nanoparticle growth decreased by a factor of 3, and the properties of nanoparticles changed. In particular, the translational energy accommodation coefficient for Ar molecules at the surface of carbon nanoparticles was found to decrease from 0.44 to 0.30. A comparison of the calculated total carbon balance at the early stage of nanoparticle formation with experimental data demonstrated that the reaction C + H₂S → HCS^· + H, which removes a portion of carbon vapor from the condensation process, has a determining effect on the carbon balance in the system. It was found that HS^· and atomic hydrogen affect the carbon balance in the system only slightly. Thus, the experimentally observed decrease in the rate of nanoparticle growth and in the sizes of nanoparticles can be explained by a decrease in the concentration of free carbon upon the addition of H₂S molecules to the system.     

Osmotic Coefficients of the Li<Subscript>2</Subscript>B<Subscript>4</Subscript>O<Subscript>7</Subscript>+LiCl + H<Subscript>2</Subscript>O System at <Emphasis Type="Italic">T</Emphasis>=273.15 K

Osmotic coefficients and water activities for the Li₂B₄O₇+LiCl+H₂O system have been measured at T=273.15 K by the isopiestic method, using an improved apparatus. Two types of osmotic coefficients, φ _S and φ _E, were determined. φ _S is based on the stoichiometric molalities of the solute Li₂B₄O₇(aq), and φ _E is based on equilibrium molalities from consideration of the equilibrium speciation into H₃BO₃,B(OH)₄⁻ and B₃O₃(OH)₄⁻. The stoichiometric equilibrium constants K _m for the aqueous speciation reactions were estimated. Two types of representations of the osmotic coefficients for the Li₂B₄O₇+LiCl+H₂O system are presented with ion-interaction models based on Pitzer’s equations with minor modifications: model (I) represents the φ _S data with six parameters based on considering the ion-interactions between three ionic species of Li⁺, Cl⁻, and B₄O₇²⁻, and model (II) for represents the φ _E data based on considering the equilibrium speciation. The parameters of models (I) and (II) are presented. The standard deviations for the two models are 0.0152 and 0.0298, respectively. Model (I) was more satisfactory than model (II) for representing the isopiestic data.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Refinement of the crystal structure of as-schwatzite Cu<Subscript>6</Subscript>(Cu<Subscript>5.26</Subscript>Hg<Subscript>0.75</Subscript>)(As<Subscript>2.83</Subscript>Sb<Subscript>1.17</Subscript>)S<Subscript>13</Subscript> (Aktash,Altai mountaines)

The crystal structure of As-schwatzite Cu₆(Cu_5.26Hg_0.75)(As_2.83Sb_1.17)S13 (Aktash deposit, Altai mountains) is refined. Tetrahedrally shaped dark-gray single crystals of the mineral belong to the cubic crystal system: I4¯3m space group, a = 10.2890(1) Å, V = 1089.2(1) ų, d = 4.99 g/cm³, Z = 2 for the composition Cu_11.26Hg_0.75As_2.83Sb_1.17S₁₃, R = 0.0177. The structure is based on the sphalerite-like framework comprising identically oriented (Cu,Hg)S₄ tetrahedra ((Cu,Hg)-S 2.3452(8) Å) and (As,Sb)S₃ pyramids ((As,Sb)-S 2.311(1) Å) sharing their vertices. The centers of [Cu₆] octahedra in the (000) and (1/2 1/2 1/2) positions coinciding with the centers of the “cluster” anionic vacancies [□]₄ are occupied by the so-called “thirteenth” sulfur atom. Quantum chemical calculations of the electron density are carried out for the [As₄S₁₃Cu₆]⁶ fragment. The calculation results confirm the presence of strain in the [As₄S₁₃Cu₆]⁶ moiety, which exists due to the support of the surrounding symmetric framework including the external sulfur atoms of the fragment. The possibility of inclusion of mercury into the framework, which is much richer in arsenic than in antimony, is demonstrated. High stability of the framework determines significant compression of the S-centered [SCu₆] octahedron in its interstices, bringing together copper atoms to 3.145(1) Å and shortening the Cu-S distances to 2.224(1) Å     

Crystal Structure of New One-Dimensional Triple Molybdate Na<Subscript>2</Subscript>K<Subscript>2</Subscript>Cu(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The title compound (disodium dipotassium copper(II) tris-[molybdate (VI)]) is prepared by form melt and characterized by single crystal X-ray diffraction and UV-vis spectroscopy. It crystallizes in the triclinic space group P-1 with a = 7.4946(8) Å, b = 9.3428(9) Å, c = 9.3619(9) Å, α = 92.591(7)°, β = 105.247(9)°, γ = 105.496(9)°, V = 604.7 ų, and Z = 2. Its structure is isotypic with that of Na₄Mn(MoO₄)₃. It is formed by Cu₂O₁₀ distorted bi-octahedral dimers linked by two bridging bidentate Mo₂O₄ tetrahedra and, additionally, two monodentate Mo₁O₄ tetrahedra to form Cu₂Mo₄O₂₀ units. These units are linked by the insertion of Mo₃O₄ tetrahedra to build infinite ribbons disposed along the c axis. All of these ribbons form a one-dimensional framework. Both K1 and K3 cations are located in the inversion center, and all the other atoms are at general positions. The structure model is supported by the bond valence sum (BVS) and charge distribution CHARDI methods. The Cu²⁺ cations adopt the [4+2] CuO₆ Jahn-Teller distortion giving rise to an intense d–d transition in the UV-vis absorption spectra.     

Ion state of atoms and the properties of perovskite-like compound CaCu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

The binding energies and valence state of atoms in the perovskite-like compound CaCu₃V₄O₁₂ have been determined using XPS spectroscopy. The stoichiometry of this phase is formulated as Ca²⁺Cu²⁺Cu ₂ ⁺ (V ₂ ⁵⁺ V ₂ ⁴⁺ O₁₂). Under an air atmosphere, the phase interacts with water vapor and oxygen. As a result, Ca(OH)₂ is formed on its surface, the Cu⁺ and V⁴⁺ ion concentrations decrease, and the Cu²⁺ and V⁵⁺ concentrations increase in association. Raman spectra show shortened cation-anion bond lengths and cation-anion-cation bond angles in CaCu₃V₄O₁₂ compared to perovskite CuVO₃; the two structures are alike. The electrical conductivity, magnetic susceptibility, thermal and sensor properties of CaCu₃V₄O₁₂ in aqueous salt solutions have been studied.     

Simultaneous Removal of H<Subscript>2</Subscript>S and Dust in the Tail Gas by DC Corona Plasma

The removal of hydrogen sulfide and dust simultaneously by the DC corona discharge plasma with a wire-cylinder reactor was studied at atmospheric pressure and room temperature. The outlet gases were analyzed by Fourier Transform Infrared. Chemical compositions of the dust collected from ground electrode were analyzed by X-ray fluorescence. The results showed that the DC corona discharge is effective in removing H₂S and dust simultaneously. The best H₂S conversion was gained with the 2 cm discharge gap. The lower inlet H₂S concentration, the higher conversion efficiency was gained at any specific input energy (SIE), while the energy yield was on the contrary. The removal efficiency of H₂S decreased gradually as oxygen concentration increased, which means that the H₂S decomposition mainly depends on direct electron collisions or short-living species, such as^·O, ^·OH radicals in the non-thermal plasma. At the initial stage, the conversion efficiency of H₂S increased with the increasing of relative humidity, but later decreased while the relative humidity keep increasing with the same SIE. Existing of dust can not only reduce the energy consumption of H₂S conversion and improve the removal efficiency, but also inhibit the yield of SO₂ for it can further react with some compounds in the dust. With the discharge gap of 2 cm, inlet H₂S concentration of 2400 ppm, O₂ Of 0.5 %, relative humidity of 41 %, dust content of 4000 ± 5 % mg/m³ and SIE of 600 J/L, the H₂S conversion reached 98.8 %, and the dust removal efficiency was close to 100 %.     

Novel large heteropolymetalate complexes formed from Ni(II) and cryptate [As<Subscript>4</Subscript>W<Subscript>40</Subscript>O<Subscript>140</Subscript><Superscript>28-</Superscript>

The heteropolytungstate (NH4)₂₀[Na2(H₂O)₂Ni(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀] · 61H₂O is obtained by the reaction of Na₂₇[NaAs₄W₄₀O₁₄₀] · 60H₂O with NiCl₂ · 6H₂O and NH₄Cl in pH≈4.0. The structure and chemical composition are determined by X-ray diffraction analysis and element analysis. The crystal data and main structure refinement are: a = 1.33135(18) nm, b = 1.9722(3) nm, c = 3.6430(5) nm, α = 78.010(2)°, β = 82.145(2)δ, γ = 74.385(2)°, V = 8.978(2) nm³, triclinic crystal system, space group: P1, Z = 2, R1 = 0.0512, and wR2 = 0.0684(I >2σ). The four S2 sites of the big cyclic ligand [As₄W₄₀O₁₄₀]^28- are occupied by two Na⁺ and two Ni²⁺ respectively, and each site supplies four O_d coordinating to metal ion. The coordination number of Ni²⁺ is six, and that of two Na⁺ is five and six respectively. The third Ni²⁺ locates outside the cyclic [As₄W₄₀O₁₄₀]^28- and connects with one O_d, and its coordination number is six.     

Theoretical study of the mechanism for C-H bond activation in spin-forbidden reaction between Ti<Superscript>+</Superscript> and C<Subscript>2</Subscript>H<Subscript>4</Subscript>

The mechanism of the spin-forbidden reaction Ti⁺(⁴F, 3d²4s¹) + C₂H₄→TiC₂H₂ ⁺ (²A₂) + H₂ on both doublet and quartet potential energy surfaces has been investigated at the B3LYP level of theory. Crossing points between the potential energy surfaces and the possible spin inversion process are discussed by means of spin-orbit coupling (SOC) calculations. The strength of the SOC between the low-lying quartet state and the doublet state is 59.3 cm⁻¹ in the intermediate complex IM1-⁴B₂. Thus, the changes of its spin multiplicity may occur from the quartet to the doublet surface to form IM1-²A₁, leading to a sig-nificant decrease in the barrier height on the quartet PES. After the insertion intermediate IM2, two distinct reaction paths on the doublet PES have been found, i.e., a stepwise path and a concerted path. The latter is found to be the lowest energy path on the doublet PES to exothermic TiC₂H₂ ⁺(²A₂) + H₂ products, with the active barrier of 4.52 kcal/mol. In other words, this reaction proceeds in the following way: Ti⁺+C₂H₄→⁴IC→IM1-⁴B₂→^4,2ISC→IM1-²A₁→[²TS_ins]→IM2→[²TS_MCTS]→IM5→TiC₂H₂ ⁺(²A₂)+H₂. Supported by ‘Qinglan’ Talent Engineering Funds by Tianshui Normal University.     

Synthesis of the mixed oxide catalysts based upon the nickel-copper hydrotalcites of the type Ni<Subscript>x</Subscript>Cu<Subscript>6-x</Subscript>Cr<Subscript>2</Subscript>(OH)<Subscript>16</Subscript>(CO<Subscript>3</Subscript>)×4H<Subscript>2</Subscript>O

Summary High resolution TG coupled to a gas evolution mass spectrometer has been used to study the thermal properties of a chromium based series of Ni/Cu hydrotalcites of formulae Ni_xCu_6-xCr₂(OH)₁₆(CO₃)×4H₂O where x varied from 6 to 0. The effect of increased Cu composition results in the increase of the endotherms and mass loss steps to higher temperatures. Evolved gas mass spectrometry shows that water is lost in a number of steps and that the interlayer carbonate anion is lost simultaneously with hydroxyl units. Differential scanning calorimetry was used to determine the heat flow steps for the thermal decomposition of the synthetic hydrotalcites. Hydrotalcites in which M²⁺ consist of Cu, Ni or Co form important precursors for mixed metal-oxide catalysts. The application of these mixed metal oxides is in the wet catalytic oxidation of low concentrations of retractable organics in water. Therefore, the thermal behaviour of synthetic hydrotalcites, Ni_xCu_6-xCr₂(OH)₁₆CO₃×nH₂O was studied by thermal analysis techniques in order to determine the correct temperatures for the synthesis of the mixed metal oxides.     

Novel 1,8-naphthalimide dye for multichannel sensing of H<Superscript>+</Superscript> and Cu<Superscript>2+</Superscript>

A novel 1,8-naphthalimide dye with simple structure has been produced by a facile synthetic method for colorimetric and fluorescent sensing of H⁺ and Cu²⁺. In CH₃CN/H₂O (1/1, v/v), the dye could monitor H⁺ using dual channels (ratiometric absorbance and fluorescence intensity change) from pH 6.2 to 12.0. Meanwhile, in the pH range of 1.9–5.2, the dye could also be used to detect Cu²⁺ using triple channels [ultraviolet–visible (UV–Vis) absorption, fluorescence intensity reduction, as well as fluorescence blueshift]. The detection limits for Cu²⁺ evaluated by colorimetric and fluorescent titration were 6.10 × 10^?7 and 2.62 × 10^?7 M, respectively. The dye exhibited specific selectivity and sensitivity for H⁺ and Cu²⁺ over various coexisting metal ions. Moreover, the sensing mechanism of the dye for H⁺ and Cu²⁺ was carefully examined.     

Crystal and molecular structures of two modifications of a chelate compound of Pb[(<Emphasis Type="Italic">iso</Emphasis>-C<Subscript>4</Subscript>H<Subscript>9</Subscript>)<Subscript>2</Subscript>PS<Subscript>2</Subscript>]<Subscript>2</Subscript>

A chelate compound Pb[(iso-C₄H₉)₂PS₂]² is synthesized. Using X-ray diffraction data, the crystal structures of two modifications of this compound are determined (X8 APEX diffractometer, MoK _α radiation, 14169 F _hkl , R = 0.0480 for the low temperature α-form and 6261 F _hkl , R = 0.0387 for the β-form studied at ambient temperature). The crystals are triclinic: a = 11.047(2) Å, b = 14.486(3) Å, c = 32.048(6) Å; α = 91.30(3)°, β = 99.73(3)°, γ = 101.61(3)°, V = 4942.9(17) ų, Z = 8, ρ_calc = 1.682 g/cm³ (α-modification) and a = 11.2124(5) Å, b = 14.6989(7) Å, c = 17.1644(6) Å; α = 109.393(1)°, β = 94.989(2)°, γ = 101.649(1)°, V = 2576.83(19) ų, Z = 4, ρ_calc = 1.613 g/cm³ (β-modification), space group \(P\bar 1\) for both polymorphs. The structures are molecular, coordination cores of PbS₄ are tetragonal pyramids with Pb atoms in the vertices and S atoms in the base. In both structures intermolecular Pb...S contacts yield supramolecular ensembles comprising by four molecules, where PbS₄₊₂ cores form planar aggregates of edge-sharing octahedra. The ensembles are joined by weak intermolecular S...S interactions resulting in the development of polymeric chains along the a axis.     

Synthesis,structural, spectral,thermal and comparative biological activity studies of [V<Subscript>2</Subscript>O<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The hydrothermal reaction of a mixture of V₂O₅, VCl₃, 2,5-pyridinedicarboxylic acid and diluted H₂SO₄ for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV ₂ ^IV O₂(SO₄)₂(H₂O)₆] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P2₁/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO₄ · xH₂O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO₄ · xH₂O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl₄, VO(acac)₂, VOSO₄ · xH₂O and [V(IV)OSO₄(H₂O)₄] · SO₄ · [H₂N(C₂H₄)₂NH₂] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor.