Synthesis,Structure, and Magnetic Properties of a Twist Linear Tetranuclear Co<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack>Ln<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack> Complexes

A series of twist linear tetranuclear 3d–4f Co ₂ ^III Ln ₂ ^III [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)] complexes have been prepared under solvothermal conditions and structurally characterized with Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L). The two central Co ions are linked by two alkoxyl oxygen atoms, and one Ln ion lying above and the other below the Co–Co dimer, form a twist linear array. The magnetic susceptibility studies reveal antiferromagnetic or ferromagnetic behaviour, whilst dynamic magnetic studies indicate no slow magnetic relaxation for these complexes.     

Hexametavanadates M<Stack><Subscript>4</Subscript><Superscript>+</Superscript></Stack>M<Superscript>2+</Superscript>(VO<Subscript>3</Subscript>)<Subscript>6</Subscript>: Thermal stability and luminescent characteristics

Rhombohedral hexametavanadates K₄Sr(VO₃)₆, K₄Ba(VO₃)₆, Rb₄ Ba(VO₃)₆, and Cs₄Ba(VO₃)₆ melt incongruently in the temperature range of 491 to 600°C. Cooling of peritectic melts yields mixtures of compounds typical of M₂⁺O-M²⁺O-V₂O₅ systems, far from equilibrium and depending on the cooling kinetics. The vanadate Cs₄Ba(VO₃)₆ undergoes reversible polymorphic transformation at 360°C. All compounds show broad-band luminescence with a maximum of the luminescence spectrum at 490–590 nm with three types of excitation. The vanadates K₄Sr(VO₃)₆ and Rb₄Ba(VO₃)₆ show the highest luminescence intensity at room temperature. The latter is also most efficient at liquid nitrogen temperatures. The luminescence spectra depend on the excitation of vanadates. Three hypotheses were put forward to interpret this finding. The nature of luminescence is attributed to the relaxation of electronic excitation in [VO₄]³⁻ structural tetrahedra present in the vanadates. The performance characteristics of luminophores were determined. These luminophores may be promising as X-ray luminescent screens, radioluminescence indicators, and light-emitting diode devices.     

La<Subscript>2</Subscript>M<Stack><Subscript>3</Subscript><Superscript>II</Superscript></Stack>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (M = Mg,Ca, Sr,or Ba) manganites: Synthesis and X-ray diffraction study

La₂M ₃ ^II Mn₄O₁₂ (M = Mg, Ca, Sr, or Ba) manganites have been synthesized by ceramic technology from lanthanum oxide, manganese(III) oxide, and magnesium, calcium, strontium, or barium carbonate. X-ray powder diffraction shows that these compounds crystallize in cubic perovskite space group Pm3m.     

Complex amidoboranes M<Superscript>2</Superscript>[M<Superscript>1</Superscript>(NH<Subscript>2</Subscript>BH<Subscript>3</Subscript>)<Subscript>4</Subscript>] (M<Superscript>1</Superscript> = Al,Ga; M<Superscript>2</Superscript> = Li,Na, K,Rb, Cs)

Structural, spectral, and thermodynamic characteristics of complex amidoboranes M²[M¹(NH₂BH₃)₄] (M¹ = Al, Ga; M² = Li, Na, K, Rb, Cs) were calculated by the B3LYP/def2-SVPD quantum-chemical method. The procedure for the synthesis of these compounds by reactions of alkali metal amidoboranes with aluminum and gallium chlorides was suggested and experimentally tested. Reaction products were characterized by the NMR and IR spectroscopy and X-ray phase analysis.     

Manganites NdMg<Stack><Subscript>3</Subscript><Superscript>I</Superscript></Stack>Mg<Subscript>3</Subscript>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (M<Superscript>I</Superscript> = Li,Na, K): X-ray diffraction data

NdLi₃Mg₃Mn₄O₁₂, NdNa₃Mg₃Mn₄O₁₂, and NdK₃Mg₃Mn₄O₁₂ manganites were synthesized for the first time by solid phase reactions of neodymium(III) and manganese(III) oxides with lithium, sodium, potassium, and magnesium carbonates. X-ray diffraction showed that the compounds crystallized in the tetragonal crystal system. Their unit cell parameters were determined.     

Phase transitions in double molybdates K<Subscript>2</Subscript>M<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> with M = Mg or Co

Phase transitions and cation mobility in double molybdates K₂M ₂ ^II (MoO₄)₃ with M = Mg or Co and the products of their heterovalent doping with scandium(III) and vanadium(V) have been studied. The transition from low to high conductivity in K₂M ₂ ^II (MoO₄)₃ is the result of a two-stage phase transition, whose occurrence is significantly extended in time. Heterovalent substitutions noticeably decrease the heat of the phase transition. The transition to the low-temperature phase is not achieved even after long-term exposure.     

X-ray diffraction study of [M<Superscript>I</Superscript>(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl] [M<Superscript>II</Superscript>Br<Subscript>6</Subscript>] (M<Superscript>I</Superscript> = Rh,Ir; M<Superscript>II</Superscript> = Re,Ir) polycrystals

Based on the X-ray diffraction data for polycrystals, the crystal structures of double complex salts [Rh(NH₃)₅Cl][ReBr₆] and [Ir(NH₃)₅Cl][ReBr₆] are refined. The structure of [Rh(NH₃)₅Cl][IrBr₆] is determined. Initial models are constructed using the Monte Carlo method in the straight space. Further refinement is made by the Rietveld method. It is shown that such an approach is suitable for the refinement of crystal structures composed of isolated rigid polyhedra and can be used to determine the structure of salts without structural analogues     

Cubane pyridine-acetylacetonate cluster complexes with the M<Subscript>3</Subscript>CuS<Stack><Subscript>4</Subscript><Superscript>5+</Superscript></Stack> core (M = Mo,W)

The reactions between [Mo₃(μ₃-S)(μ₂-S)₃(Acac)₃(Py)₃]PF₆ (HAcac is acetylacetone, Py is pyridine) and CuX (X = Cl, I, SCN) afford heterometallic cubane clusters [Mo₃(CuX)(μ₃-S)₄(Acac)₃(Py)₃]PF₆. The structures of two new compounds, [Mo₃(CuCl)S₄(Acac)₃(Py)₃]PF₆ · 3.25CH₂Cl₂ · 0.5C₆H₅CH₃ and [Mo₃(CuI)S₄(Acac)₃(Py)₃]PF₆ · 4C₆H₆, are determined by X-ray diffraction analysis. All synthesized compounds are characterized by elemental analysis and IR spectra. According to the vibrational spectra, the thiocyanate complex in the solid state is a mixture of the bond isomers [Mo₃(CuNCS)S₄(Acac)₃(Py)₃]PF₆ and [Mo₃(CuSCN)S₄(Acac)₃(Py)₃]PF₆, whereas in solution this complex exists as a isothiocyanate form.     

Synthesis and X-ray diffraction study of the LaMg<Superscript>I</Superscript>Mg(CrO<Subscript>3</Subscript>)<Subscript>2</Subscript> (M<Superscript>I</Superscript> = Li,Na, K) compounds

Ternary chromites of the composition LaM^IMg(CrO₃)₂ (M^I = Li, Na, K) were synthesized for the first time by ceramic technology from stoichiometric amounts of high purity grade La₂O₃; pure for analysis grade Li₂CO₃, Na₂CO₃, K₂CO₃, and MgCO₃; and chemically pure grade Cr₂O₃. Using X-ray diffractometry, it has been established that compounds are crystallized in cubic and tetragonal crystal systems, and parameters of their crystal lattices have been determined.     

Thermal expansion of ternary oxides in the M<Stack><Subscript>2</Subscript><Superscript>I</Superscript></Stack>O-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> system

Compounds formed in the M₂^IO-Cr₂O₃-TiO₂. system were synthesized by solid-state reactions. These compounds crystallize in hollandite- and spinel-type structures. The features of themal decomposition of the compounds with the compositions M₂^ICr₂Ti₆O₁₆(M^I = Na, K, Cs) and LiCrTiO₄ were revealed, and their thermal expansion coefficients were determined with the use of high-temperature X-ray diffraction analysis.     

X-ray fluorescence determination of the FeO/Fe<Subscript>2</Subscript>O<Stack><Subscript>3</Subscript><Superscript>tot</Superscript></Stack> ratio in rocks

Chances for estimating the FeO/Fe₂O₃^tot ratio in rocks by the K and L series of X-ray fluorescence spectra are studied. The errors in the determination of FeO/Fe₂O₃^tot by the intensity ratio of the Kβ_2,5/Kβ_1,3 and Lβ/Lα_1,2 lines are compared. The relative standard deviation of determining FeO using a set of 49 standard samples of eruptive rocks varies in the range 5–16%, depending on the ratio FeO/Fe₂O₃^tot and the concentration of FeO. The better precision is attainable for a ratio above 0.45 at a FeO concentration in the range 5–15%. For samples of andesites and basalts, the relative standard deviation is better than 4%, for rocks of the granite family it is 23% at FeO concentrations below 3%. For samples of metamorphic and sedimentary rocks, the error of FeO determination is higher than that for the eruptive ones. For samples with the ratio FeO/Fe/Fe₂O₃^tot < 0.25, the deviation may exceed 30 rel %. In contrast to chemical analysis, the X-ray fluorescence method appears advantageous in time and cost of sample preparation and can be used for routine analysis in geochemical research.     

Water uptake and infrared absorption in SrZr<Subscript>0.95</Subscript>M<Subscript>0.05</Subscript>O<Subscript>3-</Subscript><Subscript>a</Subscript> (<Emphasis Type="Italic">M</Emphasis>=Ga,Sc, Y and Nd)

Summary Proton concentration in SrZr_0.95M_0.05O_3-α (M=Ga, Sc, Y and Nd) was measured with a thermobalance at different temperatures (T=673-973 K) and water vapor pressures (P_H2O=0.9-12.8 kPa). At all the pressures and temperatures examined, the amount of proton concentration in these samples is in the order of Sc>Y>Ga>Nd. By an equilibrium evaluation, we estimated the maximum possible proton concentration about 2.0 mol% in these samples. Infrared (IR) absorption spectra are measured in these samples. The absorption bands can be fitted by four (M=Ga, Y, Nd) or three (M=Sc) Gaussian bands.     

Electronic spectra of C<Subscript>6</Subscript>H<Superscript>+</Superscript> and C<Subscript>6</Subscript>H<Stack><Subscript>3</Subscript><Superscript>+</Superscript></Stack> in the gas phase

Measurement of the ³Π-³Π transition of C₆H⁺ in the gas phase near 19486 cm⁻¹ is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants in the ground and excited-state were determined. The density of ions being sampled is merely 2×10⁸ cm⁻³. Broadening of the spectral lines indicates the excited-state lifetime to be ≈100 ps. The electronic transition of HC₆H₂⁺ at 26402 cm⁻¹ assumed to be ¹A₁-X¹A₁ in C_2v symmetry could not be rotationally resolved.     

Synthesis,crystal structure,and vibrational spectra of M<Subscript>4</Subscript>V<Subscript>2</Subscript>O<Subscript>3</Subscript>(SO<Subscript>4</Subscript>)<Subscript>4</Subscript> (M = K,Rb, Cs)

Synthesis was performed and physicochemical properties were studied for the M₄V₂O₃(SO₄)₄ complexes, where M = K, Rb, or Cs. Their crystal structures were determined using the set of data from X-ray diffraction and neutron diffraction studies. All compounds crystallize in a triclinic lattice (space group \(P\bar 1\), Z = 2) with the parameters: a = 7.7688(2), 7.8487(1), 8.1234(1) Å; b = 10.4918(3), 10.8750(2), 11.1065(1) Å; c = 11.9783(4), 12.1336(2), and 11.8039(1) Å; α = 76.600(2)°, 77.910(1)°, 79.589(1)°; β = 75.133(2)°, 75.718(1)°, 87.939(1)°; γ = 71.285(2)°, 72.189(1)°, 75.567(1)°; V = 881.78(5), 945.42(3), 1014.34(2) ų for K, Rb, Cs, respectively. The structure of M₄V₂O₃(SO₄)₄ was found to be formed by discrete complex anions V₂O₃(SO₄) ₄ ^4? incorporating two oxygen-bridged vanadium atoms in a distorted octahedral oxygen environment. The sulfate groups are coordinated by the vanadium atoms in the chelating mode with a large scatter of S-O interatomic distances and OSO angles. Every VO₆ octahedron has a short terminal vanadium-oxygen bond with a length of about 1.6Å. The V₂O₃(SO₄) ₄ ^4? complex anions in potassium and rubidium compounds differ from that in Cs₄V₂O₃(SO₄)₄ in the type of symmetry and mutual spatial orientation. The vibrational spectra were presented and interpreted in line with the structural analysis data.     

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.     

Direct comparison of Au<Stack><Subscript>3</Subscript><Superscript>+</Superscript></Stack> and C<Stack><Subscript>60</Subscript><Superscript>+</Superscript></Stack> cluster projectiles in SIMS molecular depth profiling

The sputtering properties of two representative cluster ion beams in secondary ion mass spectrometry (SIMS), C(60)(+) and Au(3)(+), have been directly compared. Organic thin films consisting of trehalose and dipalmitoylphosphatidylcholine (DPPC) are employed as prototypical targets. The strategy is to make direct comparison of the response of a molecular solid to each type of the bombarding cluster by overlapping the two ion beams onto the same area of the sample surface. The ion beams alternately erode the sample while keeping the same projectile for spectral acquisition. The results from these experiments are important to further optimize the use of cluster projectiles for SIMS molecular depth profiling experiments. For example, Au(3)(+) bombardment is found to induce more chemical damage as well as Au implantation when compared with C(60)(+). Moreover, C(60)(+) is found to be able to remove the damage and the implanted Au effectively. Discussions are also presented on strategies of enhancing sensitivity for imaging applications with cluster SIMS.     

Synthesis and Properties of Scandium and Alkaline-Earth Double Borates M<Subscript>3</Subscript>Sc(BO<Subscript>3</Subscript>)<Subscript>3</Subscript>

Compounds M₃Sc(BO₃)₃ (M = Ba, Sr) were prepared by solid-phase reactions and studied by X-ray diffraction (XRD) analysis and IR spectroscopy. The structural type of the compounds was determined and their unit cell parameters were refined.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 25–27.Original Russian Text Copyright © 2005 by Khamaganova, Khrushcheva.     

Synthesis,structure formation,and thermal expansion of A<Superscript>+</Superscript>M<Superscript>2+</Superscript>MgE<Superscript>4+</Superscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The compounds AMMgE(PO₄)₃ (A = Na, K, Rb, Cs; M = Sr, Pb, Ba; E = Ti, Zr) were synthesized by the sol–gel procedure followed by heat treatment and studied by X-ray diffraction, differential thermal and electron microprobe analysis, and IR spectroscopy. The phosphates crystallize in the kosnarite (KZr₂(PO₄)₃, space group \(R\bar 3\)) and langbeinite (K₂Mg₂(SO₄)₃, space group P2₁3) structural types. The structure of KPbMgTi(PO₄)₃ was refined by full-profile analysis (space group P2₁3, Z = 4, a = 9.8540(3) Å, V = 956.83(4) ų). The structure is formed by a framework of vertex-sharing MgO₆ and TiO₆ octahedra and PO₄ tetrahedra. The K and Pb atoms fully occupy the extra-framework cavities and are coordinated to nine oxygen atoms. A variable-temperature X-ray diffraction study of KPbMgTi(PO₄)₃ showed that the compound expands isotropically and refer to medium-expansion class (linear thermal expansion coefficients α _a = α _b = α _c = 8 × 10^–6°C^–1). The number of stretching and bending modes of the PO₄ tetrahedron observed in the IR spectra is in agreement with that predicted by the factor group analysis of vibrations for space groups \(R\bar 3\) and P2₁3. A structural transition from the cubic langbeinite to the rhombohedral kosnarite was found for CsSrMgZr(PO₄)₃. In the morphotropic series of ASrMgZr(PO₄)₃ (A = Na, K, Rb, Cs) the kosnarite–langbeinite transition occurs upon the Na → K replacement. The effect of the sizes and electronegativities of cations combined in AMMgE(PO₄)₃ on the change of the structural type was analyzed.     

Synthesis,crystal structure of a new tetranuclear Ni<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack>Cu<Stack><Subscript>2</Subscript><Superscript>II</Superscript></Stack> complex containing a macrocyclic ligand

The first inorg/organic hybrid complex incorporating the macrocyclic oxamide, of formula [(NiL)₂Cu₂(μ-NSC)₂(NSC)₂] (1), (NiL, H₂L = 2, 3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been synthesized and structurally characterized. The crystals crystallize in the triclinic system, space group P-1, for (1) a = 8.319(3) Å, b = 10.434(4) Å, c = 14.166(5) Å, a = 107.030(5)°, β  =  91.257(5)°, γ = 107.623(5)°. The complex involved both bridging N, S-ligand, and oxamide ligand, C–H?S interactions and NCS → Ni weak coordination interactions making the complex superamolecular.     

Crystal structure of M<Superscript>I</Superscript>VWO<Subscript>6</Subscript> (M = Li,Na) compounds

Compounds of the composition M^IVWO₆ (M = Li, Na) were prepared by solid-phase synthesis at 600°C. The compounds crystallize in the mineral brannerite structure type. The sodium derivative was prepared and identified for the first time. The crystal structures of the compounds were refined by the Rietveld method (space group C2/m).