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.     

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.     

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.     

Energetic ion bombardment of Ag surfaces by C<Stack><Subscript>60</Subscript><Superscript>+</Superscript></Stack> and Ga<Superscript>+</Superscript> projectiles

The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C60+ cluster projectiles compared with Ga+ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C60+ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga+ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. The experimental findings are in reasonable agreement with recent molecular dynamics simulations.     

A New Molybdophosphate Constructed From {Mo<Stack><Subscript>2</Subscript><Superscript>V</Superscript></Stack>O<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>}<Superscript>2+</Superscript> and 1-Hydroxyethylidenediphosphonate

A new molybdophosphate (NH₄)₈{Mo₂^VO₄[(Mo₂^VIO₆)CH₃C(O)(PO₃)₂]₂}·14H₂O (1), has been synthesized by the reaction of {Mo₂^VO₄(H₂O)₆}²⁺ fragments with 1-hydroxyethylidenediphosphonate (hedp HOC(CH₃)(PO₃H₂)₂), and it is characterized by ³¹P NMR, IR, UV, element analysis, TG and single-crystal X-ray analysis. The structure analysis reveals that the polyoxoanion can be described as two {(Mo₂^VIO₆)(CH₃C(O)(PO₃)₂} units connected by a {Mo₂^VO₄}²⁺ moiety. In the structure, the six Mo atoms are arranged into a new “W-shaped” structure, which represents a new kind of molybdophosphate.     

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.     

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.     

Prediction of new A<Subscript>3+</Subscript>B<Subscript>3+</Subscript>C<Subscript>2+</Subscript>O<Subscript>4</Subscript> compounds

Hitherto unprepared ABCO₄ compounds (where A and B stand for tervalent metals (r _A ≥ r _B) and C stands for a divalent metal) are predicted. Criteria are found to predict the possibility for these compounds to crystallize in some type of structure (K₂NiF₄, CaFe₂O₄, YbFe₂O₄, or spinel) at room temperature and atmospheric pressure. The prediction is based only on the properties of elements and simple oxides. A special software system for computer-aided analysis of information is used for calculations involving pattern recognition based on use case.     

Comparative reactivity of A<Superscript>IV</Superscript>B<Superscript>VI</Superscript> compounds in their reactions with dioxygen

The interaction of A^IVB^VI semiconductors with molecular oxygen has been investigated theoretically (by first-principles calculations using density functional theory) and experimentally (by X-ray photoelectron spectroscopy). It is demonstrated by correlating calculated and experimental data that the comparative reactivity of the solid phases can be quickly estimated using the small-cluster model.     

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.     

Oxidation of Diethyl Sulfide in Aqueous Solutions by Peroxynitrite and the H<Subscript>2</Subscript>O<Subscript>2</Subscript>-NO<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> System

It was found that nitrite anions are effective activators of hydrogen peroxide in the reaction with diethyl sulfide. The observed kinetics are consistent with the proposed intermediate formation of peroxynitrous acid (ONOOH). The rate constants for the reaction of diethyl sulfide Et₂S with the acid ONOOH (k₀ = 1.8⋅10³ L/mol⋅s) and with the anion ONOO⁻ (k₋ = 6⋅10⁻² L/mol⋅s) are respectively 10⁵ and three times higher than with hydrogen peroxide. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 290–295, September–October, 2005.     

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.     

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.     

Effect of the Composition of Modified SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>/ZrO<Subscript>2</Subscript> on Catalytic Properties in Reduction of NO by Hydrocarbons

We have shown that the activity of cobalt-containing catalysts based on sulfated zirconium dioxide in selective catalytic reduction (SCR) of NO by methane depends on the amount of sulfur and the preparation method. Modification of Fe and Mn improves the catalytic behavior of SO ₄ ²⁻ /ZrO₂ as a result of the increase in the concentration of active sites.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 121–125, March– April, 2005.     

Density functional theory study of UO<Stack> <Subscript>2</Subscript> <Superscript>2+</Superscript> </Stack> solvation in 1-butyl-3-methylimidazolium chloride

Structural characteristics and energies of [UO₂Cl₄(BMIm)_n]^(n–2)+ (n = 1-4) solvation complexes have been studied by the density functional theory (DFT) method in the SVWN5 local functional approximation.     

Synthesis,structures, and physicochemical properties of Sr<Subscript>2</Subscript>A<Superscript>II</Superscript>UO<Subscript>6</Subscript> (A<Superscript>II</Superscript> = Mg,Ca, Sr,Ba, Mn,Fe, Co,Ni, Zn,and Cd) compounds

Sr₂A^IIUO₆ (A^II = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Zn, and Cd) compounds were synthesized by high-temperature reactions in the solid phase. The crystal structure (space group P2₁/n) was refined by the Rietveld method for Sr₂MgUO₆, (Sr_0.5Ba_0.5)₂SrUO₄, and Sr₂CdUO₆, which were synthesized for the first time. IR spectral characteristics were studied. The standard enthalpies of formation of the compounds were determined by reaction calorimetry.