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.     

Synthesis,structures, IR spectra,and thermal characteristics of compounds of general formula Ba(M<Stack><Subscript>2/3</Subscript><Superscript>III</Superscript></Stack>U<Subscript>1/3</Subscript>)O<Subscript>3</Subscript> (M<Superscript>III</Superscript> = Sc,Y, In,Nd-Lu)

Compounds with the composition Ba(M _2/3 ^III U_1/3)O₃ (M^III = Sc, Y, In, Nd-Lu) were synthesized by high-temperature solid-state reactions. The structures of the compounds were studied by X-ray diffraction analysis, including the high-temperature method, and IR spectroscopy.     

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.     

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.     

The thermochemical characteristics of the LnCl<Superscript>−</Superscript><Subscript>4</Subscript> and Ln<Subscript>2</Subscript>Cl<Superscript>−</Superscript><Subscript>7</Subscript> negative ions

The literature data on the thermochemical characteristics of negative LnCl^? ₄ and Ln₂Cl^? ₇ ions (from lanthanum to lutetium inclusive) in the gas phase are systematized. The enthalpies of ion-molecular and ion-ion reactions with the participation of these ions were calculated and used to determine the enthalpies of formation of the ions for the whole lanthanide series.     

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.     

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.     

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.     

Heat capacity and magnetic phase transition of two-dimensional metal-assembled complex (NEt<Subscript>4</Subscript>)[{Mn<Superscript>III</Superscript>(salen)}<Subscript>2</Subscript>Fe<Superscript>III</Superscript>(CN)<Subscript>6</Subscript>]

Summary Heat capacity measurements of the two-dimensional metal-assembled complex, (NEt₄)[{Mn^III(salen)}₂Fe^III(CN)₆] [Et=ethyl, salen= N,N’-ethylenebis(salicylideneaminato) dianion], were performed in the temperature range between 0.2 and 300 K by adiabatic calorimetry. A ferrimagnetic phase transition was observed at T_c1=7.51 K. Furthermore, another small magnetic phase transition appeared at T_c2=0.78 K. Above T_c1, a heat capacity tail arising from the short-range ordering of the spins characteristic of two-dimensional magnets was found. The magnetic enthalpy and entropy were evaluated to be ΔH=291 J mol^-1 and ΔS=27.4 J K^-1 mol^-1, respectively. The experimental magnetic entropy agrees roughly with ΔS=Rln(5·5·2) (=32.5 J K^-1 mol^-1; R being the gas constant), which is expected for the metal complex with two Mn(III) ions in high-spin state (spin quantum number S=2) and one Fe(III) ion in low-spin state (S=1/2). The heat capacity tail above T_c1 became small by grinding and pressing the crystal. This mechanochemical effect would be attributed to the increase of lattice defects and imperfections in the crystal lattice, leading not only to formation of the crystal with a different magnetic phase transition temperature but also to decrease of the magnetic heat capacity and thus the magnetic enthalpy and entropy.     

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.     

Synthesis,structure, and electrochemistry of <Emphasis Type="Italic">trans</Emphasis>-[Co<Superscript>III</Superscript>{(BA)<Subscript>2</Subscript>pn}(L)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N′-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV–Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)–cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and Characterization of New Os<Subscript>2</Subscript><Superscript>5+</Superscript> and Os<Subscript>2</Subscript><Superscript>6+</Superscript> Azido Complexes

Reaction of Os₂(OAc)₄Cl₂ with an excess of HDPhF (HDPhF = N,N′-diphenylformamidine) gives a high yield of Os₂(DPhF)₄Cl₂ (1), which can be converted to its azido analog, Os₂(DPhF)₄(N₃)₂ (3), by treatment with NaN₃. We report a major improvement on the preparation of Os₂(chp)₄Cl (2; Hchp = 2-chloro-6-hydroxypyridine) by synthesizing the compound in the reducing solvent ethanol. Reaction of 2 with NaN₃ affords the azido complex Os₂(chp)₄N₃ (4). Compound 3 has been examined by X-ray crystallography, and has an Os–Os bond distance of 2.45 Å, suggesting a (π*)² ground state for the molecule.     

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.     

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.     

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.     

ESR Study of the Formation of O<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> Radical Anions on Oxidized CeO<Subscript>2</Subscript> and CeO<Subscript>2</Subscript>/ZrO<Subscript>2</Subscript> Adsorbing a CO + O<Subscript>2</Subscript> Mixture

It is demonstrated by ESR measurements that O ₂ ⁻ (CO + O₂) radical anions result from CO + O₂ adsorption on the oxidized surface of CeO₂. These radical anions are stabilized in the coordination sphere of Ce⁴⁺ cations located in isolated and associated anionic vacancies. This reaction shows an activation behavior determined by CO adsorption. The variation of O ₂ ⁻ (CO + O₂) concentration with CO adsorption temperature suggests that surface carbonates and carboxylates participate in this reaction. In the (0.5– 10.0)%CeO₂/ZrO₂ system, O ₂ ⁻ forms on supported CeO₂ and is stabilized on Ce⁴⁺ and Zr⁴⁺ cations. The stability of O ₂ ⁻ -Ce⁴⁺ complexes is lower on supported CeO₂ than on unsupported CeO₂, indicating a strong interaction between the cerium cations and the support.__________Translated from Kinetika i Kataliz, Vol. 46, No. 3, 2005, pp. 423–429.Original Russian Text Copyright © 2005 by Il’ichev, Kuli-zade, Korchak.     

Experimental Research of OH and N<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> Spatially Resolved Spectra in a Needle-Plate Pulsed Streamer Discharge

In this study, the spatial distributions of the emission intensity of OH (\(\hbox{A}^{2}\Upsigma {\rightarrow}\hbox{X}^{2}\Uppi,\) 0-0) and \(\hbox{N}_{2}^{+} (\hbox{B}^{2}\Upsigma_{\rm u}^{+}\rightarrow \hbox{X}^{2}\Upsigma_{\rm g}^{+},\) 0-0, 391.4 nm) are investigated in the atmospheric pressure pulsed streamer discharge of H₂O and N₂ mixture in a needle-plate reactor configuration. The effects of pulsed peak voltage, pulsed repetition rate, input power, and O₂ flow rate on the spatial distributions of the emission intensity of OH (\(\hbox{A}^{2}\Upsigma {\rightarrow}\hbox{X}^{2}\Uppi,\) 0-0), \(\hbox{N}_{2}^{+} (\hbox{B}^{2}\Upsigma _{\rm u}^{+} \rightarrow \hbox{X}^{2}\Upsigma _{\rm g}^{+},\) 0-0, 391.4 nm), and the vibrational temperature of N₂ (C) in the lengthwise direction from needle to plate are attained. It is found that the emission intensities of OH (\(\hbox{A}^{2}\Upsigma {\rightarrow}\hbox{X}^{2}\Uppi,\) 0-0) and \(\hbox{N}_{2}^{+} (\hbox{B}^{2}\Upsigma_{\rm u}^{+} \rightarrow \hbox{X}^{2}\Upsigma_{\rm g}^{+},\) 0-0, 391.4 nm) rise with increasing the pulsed peak voltage, the pulsed repetition rate and the input power, and decrease with increasing O₂ flow rate. In the direction from needle to plate, the emission intensity of OH (\(\hbox{A}^{2}\Upsigma {\rightarrow}\hbox{X}^{2}\Uppi,\) 0-0) decreases firstly, and rises near the plate electrode, while the emission intensity of \(\hbox{N}_{2}^{+}(\hbox{B}^{2}\Upsigma_{\rm u}^{+} \rightarrow \hbox{X}^{2}\Upsigma_{\rm g}^{+},\) 0-0, 391.4 nm) is nearly constant along the needle to plate direction firstly, and rises sharply near the plate electrode. The vibrational temperature of N₂ (C) is almost independent of the pulsed peak voltage and the pulsed repetition rate, but rises with increasing the O₂ flow rate and keeps nearly constant in the lengthwise direction. The main physicochemical processes involved are discussed.     

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.     

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.