Synthesis,crystal structure of Gd(H2O)(C2O4)2 · NH4 and of La(C2O4)2 · NH4. Characterization of the Ln(H2O)(C2O4)2 · NH4 with Ln=Eu…Yb

Single crystals of two lanthanide complexes, presenting similar formula Ln(H₂O)_x(C₂O₄)₂ · NH₄ with Ln=La, x=0 and Ln=Gd, x=1, have been prepared, in closed system at 200 °C. The gadolinium complex is bi-dimensional. A layer is built by the packing of the basic unit, [Gd(C₂O₄)]₄. The gadolinium atoms are related only by bischelating oxalate ligands, the ammonium ion and the water molecule (bound to the gadolinium atom) are localized into the interlayer space. The lanthanum complex is tri-dimensional. The basic building unit remains approximately the same and the packing of these units form a layer. However, within these units, the lanthanum atoms are related by either an oxalate ligand or an edge. Moreover, an oxalate ligand assumes the connection between the layers. The ammonium ion is localized into two sets of intersecting channels. Pure phase of the gadolinium complex has been prepared at 100 °C and extended to some lanthanide elements, Eu…Yb. As the size of the lanthanide ionic radius is decreasing, it is noticeable that the a unit–cell constant follows an expansion pattern while the others two follow an usual contraction one. The thermal behavior of this family shows that the anhydrous compounds are obtained and that some water molecule is sorbed during the cooling. Thus, the anhydrous compounds present a relatively open-framework with some small micropores.     

Study of the state of uranyl orthovanadate (UO2)3(VO4)2·4H2O in aqueous solutions

The state of uranyl orthovanadate (UO₂)₃(VO₄)₂·4H₂O in aqueous solutions was studied by the methods of chemical analysis, X-ray diffraction, and IR spectroscopy. Uranyl vanadate is transformed into compounds of other composition and structure upon contact with aqueous phases of various acidity. Equilibrium constants of reactions occurring in heterogeneous systems (UO₂)₃(VO₄)₂·4H₂O-aqueous solution were calculated from the data on the solubility. Phase diagrams of bottom solid phases and of equilibrium aqueous solutions were constructed.     

Identification of the cobalt(II) chloride ‘mixed’ solvate Co4Cl8(H2O)4(MeCN)6: the ionic structure trans-[Co(H2O)2(MeCN)4] trans-[Co(H2O)2(MeCN)2(CoCl4)2]

The structure of the title compound features mononuclear octahedral Co^II cations, trans-[Co(H₂O)₂(MeCN)₄]²⁺, and trinuclear anions, trans-[Co(H₂O)₂(MeCN)₂(CoCl₄)₂]^2–; the latter centrosymmetric units contain a central octahedral Co(H₂O)₂(MeCN)₂ moiety with two tetrahedral [CoCl₄]^2– ligands. These two large ions are held in a network of intra- and inter-molecular hydrogen bonding.     

Application of the Ru(bipy)2(dpp)2+ / C2O4 2− electrochemiluminescence reaction to the determination of phenol

The electrochemiluminescence (ECL) of the ruthenium di(2,2′-bipyridine)- (4,7-diphenyl-1,10-phenanthroline) complex (Ru-bipy-dpp) produced on a glassy carbon electrode was studied by cyclic voltammetry. The anodic oxidation of Ru-bipy-dpp produces ECL in the presence of oxalate in oxygen-free aqueous solutions. Threefold ECL efficiencies were obtained for Ru-bipy-dpp relative to Ru(bipy)₃ as a standard. The ECL of Ru-bipy-dpp is quenched by both oxygen and phenol. The luminescence intensity was proportional to the concentration of phenol in the range of 5–100 μM. At a phenol concentration of 100 μM, the ECL of Ru-bipy-dpp peaking at 597 nm was completely quenched. Correspondence: Dan Xiao, College of Chemistry and Chemical Engineering, Sichuan University, Chengdu 610065, P.R. China     

Structure of the complex [trans-SnF4(H2O)2· (18-crown-6)· 2H2O]

The molecular and crystal structure of the title complex (I) obtained by addition of tin fluoride in a hydrofluoric acid solution to 18-crown-6 in methanol was investigated by X-ray structure analysis. The crystals are monoclinic, space group P2₁/n, a = 13.497(3), b = 7.806(2), c = 9.892(2) Å, β = 95.57(3)°, Z = 2 for C₁₂H₃₂F₄O₁₀Sn. In the polymer chain, the crown ether molecules alternate with the inorganic complexes [trans-SnF₄(H₂O)₂] and are linked to them by O-H...O type hydrogen bonds involving the intermediate water molecules. The weak C-H...F interactions bind the chains into the layers which are parallel to the xz plane.     

Synthesis and structure of the oxalatotetranitratouranylate complex (NH4)2[{UO2(NO3)2}2(μ4-C2O4)] · 2H2O

The reaction of diaquadinitratouranyl with ammonium nitrate in ethanol gave the single crystals of ((NH₄)₂[}UO₂(NO₃)₂}₂(μ₄-C₂O₄)] · 2H₂O (I).The structure of the complex was studied by X-ray diffraction. The crystals are monoclinic, a = 8.6497(10) Å, b = 11.7001(10) Å, c = 20.2135(10) Å, β = 93.924(10)°, space group P2₁/c, Z = 4, V = 2040.9(3) ų. The structural units of the crystal are island binuclear groups [{UO₂(NO₃)₂}₂(μ₄-C₂O₄)]^2?, ammonium cations, and crystal water molecules. The structure has a complex three-dimensional packing provided by electrostatic attraction forces of the counterions and the hydrogen bond system involving water molecules, oxalate, nitrate, and uranyl ions. The IR spectra of I confirm the X-ray diffraction data.     

Hydrothermal Synthesis, Crystal Structure and Electrochemical Properties of the Copper(Ⅱ) Complex [Cu4O4(phen)4(ClC6H4COO)2(H2O)2]·(H2O)3

The title complex of copper(Ⅱ) with m-chlorobenzoic acid, 1,10-phenanthroline (phen) and copper perchlorate has been synthesized and characterized in the solvent mixture of water and methanol. Crystal data for this complex: triclinic, space group P, a = 1.06853(12), b = 1.30740(16), c = 1.49546(17) nm, α = 101.791(2), β = 103.413(2), γ = 105.815(2)o, V = 1.8736(4) nm3, Mr = 904.67, Dc = 1.604 g/cm3, Z = 2, F(000) = 924, μ = 1.34 mm-1, GOOF = 1.049, the final R = 0.0324 and wR = 0.0797. The structure analysis shows that a chair-like structure [Cu4O4] is defined by three quadrilaterals shaped by four copper and four oxygen atoms, and every copper ion is coordinated by three oxygen atoms from three water molecules and two nitrogen atoms from one 1,10-phenanthroline molecule, giving a distorted square-pyramidal coordination geometry. The CV analysis results indicate that the electron transfer in the electrode reaction is quasi-reversible.     

Synthesis and Crystal Structure of [Ni(H2O)6][Ni(H2O)2(C4H2O4)]·4H2O

Reaction of a freshly prepared Ni(OH)_{2?2 x} (CO₃) _x ·yH₂O with maleic acid in H₂O at room temperature afforded [Ni(H₂O)₆][Ni(H₂O)₂(C₄H₂O₄)]·4H₂O, which consists of [Ni(H₂O)₆]²⁺ cations, [Ni(H₂O)₂(C₄H₂O₄)]^2? anions and lattice H₂O molecules. Ni atoms in cations are octahedrally coordinated and Ni atoms in anions are each octahedrally coordinated by bidentate chelating maleato ligands and two water molecules at trans positions. Cations and anions are interlinked by hydrogen bonds to form 1D chains, which are hexagonally arranged and connected by the lattice water molecules. When heated in a flowing argon stream, the compound decomposes, with complete dehydration being followed by dissociation of nickel maleate into NiO and maleic anhydride.     

A Raman spectroscopic study of the antimonite mineral peretaite Ca(SbO)4(OH)2(SO4)2·2H2O

Raman spectra of mineral peretaite Ca(SbO)₄(OH)₂(SO₄)₂·2H₂O were studied, and related to the structure of the mineral. Raman bands observed at 978 and 980 cm^?1 and a series of overlapping bands observed at 1060, 1092, 1115, 1142 and 1152 cm^?1 are assigned to the SO₄^2? ν₁ symmetric and ν₃ antisymmetric stretching modes. Raman bands at 589 and 595 cm^?1 are attributed to the SbO symmetric stretching vibrations. The low intensity Raman bands at 650 and 710 cm^?1 may be attributed to SbO antisymmetric stretching modes. Raman bands at 610 cm^?1 and at 417, 434 and 482 cm^?1 are assigned to the SO₄^2? ν₄ and ν₂ bending modes, respectively. Raman bands at 337 and 373 cm^?1 are assigned to O–Sb–O bending modes. Multiple Raman bands for both SO₄^2? and SbO stretching vibrations support the concept of the non-equivalence of these units in the peretaite structure.     

Kinetics of the thermal dehydration of potassium titanium oxalate, K2TiO(C2O4)2·2H2O

The thermal dehydration reaction of potassium titanium oxalate, K₂TiO(C₂O₄)₂·2H₂O, has been studied by means of thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) in nitrogen atmosphere at different heating rates. K₂TiO(C₂O₄)₂·2H₂O dehydrates in a single step through a practically irreversible process. The activation energy involved and its dependence on the conversion degree were estimated by evaluating the thermogravimetric data according to model-free methods, and values of activation energy were determined for the dehydration reaction. Activation energy values were also evaluated from DSC data using isoconversional methods. The complexity of the dehydration of K₂TiO(C₂O₄)₂·2H₂O is illustrated by the dependence of E on the extent of conversion, ?? (0.05??????????0.95).     

Vibrational spectroscopic characterization of the phosphate mineral hureaulite – (Mn,Fe)5(PO4)2(HPO4)2·4(H2O)

This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn_3.23, Fe_1.04, Ca_0.19, Mg_0.13)(PO₄)_2.7(HPO₄)_2.6(OH)_4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm⁻¹ assigned to PO stretching vibrations of HPO₄²⁻ units. The Raman band at 989 cm⁻¹ is assigned to the PO₄³⁻ stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm⁻¹ are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO₄²⁻ and PO₄³⁻ units. A set of Raman bands at 531, 543, 564 and 582 cm⁻¹ are assigned to the ν₄ bending modes of the HPO₄²⁻ and PO₄³⁻ units. Raman bands observed at 414, and 455 cm⁻¹ are attributed to the ν₂ HPO₄²⁻ and PO₄³⁻ units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.     

Crystal structure and the magnetic properties of tris(2-chloromethyl-4-oxo-4H-pyran-5-olato-κ2O5,O4)iron(III)

The tris(2-chloromethyl-4-oxo-4H-pyran-5-olato-κ²O⁵,O⁴)iron(III), [Fe(kaCl)₃], has been synthesized and characterized by the crystal structure analysis, magnetic susceptibility measurements, Mössbauer, and EPR spectroscopic methods. The X-ray single crystal analysis of [Fe(kaCl)₃] revealed a mer isomer. The magnetic susceptibility measurements indicated the paramagnetic character in the temperature range of 2 K–298 K. The EPR and Mössbauer spectroscopy confirmed the presence of an iron center in a high-spin state. Additionally, the temperature-independent Mössbauer magnetic hyperfine interactions were observed down to 77 K. These interactions may result from spin–spin relaxation due to the interionic Fe³⁺ distances of 7.386 Å.     

Synthesis and Crystal Structure of (C6N3H18)2Ti4O4(C2O4)7·4H2O

The title compound (C6N3H18)2Ti4O4(C2O4)7(4H2O 1 (C13H22N3O18Ti2, Mr = 604.14) was synthesized by the reaction of Ti(SO4)2, H2C2O4(2H2O and N-(2-ammonioethyl)- piperazinium (AEPP) in aqueous solution. The single-crystal X-ray analysis has revealed that 1 crystallizes in the triclinic system, space group Pī with a = 9.1437(6), b = 11.4991(10), c = 11.6975(8)A, α = 96.2915(18), β = 107.998(3), γ = 104.276(4)°, V = 1110.35(14)A3, Z = 2, Dc = 1.807 g/cm3, F(000) = 618, μ = 0.815 mm－1, the final R = 0.0463 and wR = 0.1264 for 3718 observed reflections with I > 2σ(I). X-ray crystal-structure analysis suggests that compound 1 consists of [Ti4O4(C2O4)7]6－ anion and two protonated N-(2-ammonioethyl)piperazinium cations. The anions are linked into an infinite chain through Ti4O4(C2O4)8 by sharing the oxalates as bridging ligands.     

Synthesis of (VO)2P2O7 catalystsvia exfoliation-reduction of VOPO4·2H2O in butanol in the presence of ethanol

The exfoliation-reduction of VOPO₄·2H₂O in l-butanol oriso-butanol alone, and in a l-butanol/ethanol oriso-butanol/ethanol mixture, were conducted. Although all precursors were composed of a lamellar compound with intercalated alcohol molecules, VOHPO₄·0.5H₂O was formed when the exfoliation-reduction process was carried out in the mixed alcohol. All precursors transformed to a single phase of (VO)₂P₂O₇ under the reaction conditions forn-butane oxidation, but the crystallinity of (VO)₂P₂O₇ was different. The catalyst synthesized iniso-butanol/ethanol was well crystalline (VO)₂P₂O₇, and exhibited higher selectivity to maleic anhydride than that synthesized iniso-butanol alone for then-butane oxidation.     

Thermal behavior of the mixed composition xSb2O3–(1 − x)Bi2O3–6(NH4)2HPO4

The study of the system xSb₂O₃–(1 ? x)Bi₂O₃–6(NH₄)₂HPO₄ has been carried out to identify the phases and simulate the mechanisms of their formation, using the technique of thermal analysis in association with X-ray diffractometry. The main stages observed during thermal treatment of the samples include: (1) elimination of water and ammonia leading to the formation of (NH₄)₅P₃O₁₀; (2) reaction of the latter with M ₂ ^III O₃ and the formation of acidic polyphosphates M ₂ ^III H₂P₃O₁₀; (3) their dehydration with the formation of the polyphosphates M^III(PO₃)₃. Then Sb(PO₃)₃ decomposes giving SbPO₄ and P₂O₅. In the presence of excessive P₂O₅, two moles of Bi(PO₃)₃ condensate into oxophosphates Bi₂P₄O₁₃ and BiP₅O₁₄. The data of thermal analysis match with the composition of intermediate and final products. The hygroscopicity of the samples diminishes with growing bismuth content.     

Synthesis and X-ray diffraction study of K4[(UO2)2(C2O4)3(NCS)2] · 4H2O

Single crystals of K₄[(UO₂)₂(C₂O₄)₃(NCS)₂] · 4H₂O(I) have been synthesized and studied by X-ray diffraction. The crystals are monoclinic with the unit cell parameters a = 8.0226(7) Å, b = 14.9493(11) Å, c = 11.1670(9) Å, β = 98.299(3)°, space group P2₁/n, Z = 2, V = 1325.26(19) ų, R = 0.0186. The main structural units of the crystals of structure I are discrete binuclear groups [(UO₂)₂(C₂O₄)₃(NCS)₂]^4? belonging to the crystal-chemical group A₂K⁰²B ₂ ⁰¹ M ₂ ¹ (A =UO ₂ ²⁺ , K⁰² =C₂O ₄ ^2? , B⁰¹ =C₂O ₄ ^2? , M¹ = NCS^?) of the uranyl complexes. The uranium-containing complexes are linked into a three-dimensional framework through the potassium ions and a system of hydrogen bonds involving the outer-sphere water molecules.     

Synthesis and structure of (NH4)2[(UO2)2(C2O4)(CH3COO)4] · 2H2O

Single crystals of (NH₄)₂[(UO₂)₂C₂O₄(CH₃COO)₄] · 2H₂O have been synthesized and studied. The compound crystallizes in the orthorhombic system with the unit cell parameters a = 6.9225(14) Å, b = 12.327(3) Å, c = 14.619(3) Å, space group Immm, Z = 2, and V = 1247.6(5) ų. The main structural units of the crystals are the isle binuclear groups [(UO₂)₂C₂O₄(CH₃COO)₄]^2? belonging to the crystal-chemical group A₂K⁰²B ₄ ⁰¹ (A = UO ₂ ²⁺ , K⁰² = C₂O ₄ ^2? , B⁰¹ = CH₃COO^?) of the uranyl complexes. The uranium-containing groups are linked into a three-dimensional framework due to electrostatic interaction with the ammonium cations and through a system of hydrogen bonds involving atoms of the water molecules, oxalate and acetate ions, and ammonium and uranyl cations.     

A Raman spectroscopic study of the mineral coquandite Sb6O8(SO4)·(H2O)

Raman spectra of coquandite Sb₆O₈(SO₄)·(H₂O) were studied, and related to the structure of the mineral. Raman bands observed at 970, 990 and 1007 cm^?1 and a series of overlapping bands are observed at 1072, 1100, 1151 and 1217 cm^?1 are assigned to the SO₄^2? ν₁ symmetric and ν₃ antisymmetric stretching modes respectively. Raman bands at 629, 638, 690, 751 and 787 cm^?1 are attributed to the SbO stretching vibrations. Raman bands at 600 and 610 cm^?1 and at 429 and 459 cm^?1 are assigned to the SO₄^2? ν₄ and ν₂ bending modes. Raman bands at 359 and 375 cm^?1 are assigned to O–Sb–O bending modes. Multiple Raman bands for both SO₄^2? and SbO stretching vibrations support the concept of the non-equivalence of these units in the coquandite structure.