Synthesis and magnetic properties of liquid crystalline lanthanide complexes with alkylsulfate counterions

The reaction of Schiff"s base L with lanthanide alkylsulfates affords liquid crystalline complexes with the general formula L₃Ln(C_nH_2n+1OSO₃)₃. The liquid crystalline structure and magnetic properties are studied by polarization thermal microscopy, differential scanning calorimetry, X-ray diffraction, and measurement of magnetic susceptibility. The temperatures of the existence of the mesophase and magnetic anisotropy of the complexes with the same lanthanide depend on the chain length of the alkyl fragment in the sulfate anion.     

Structural and magnetic properties of iron(II) complexes with 1,4,5,8,9,12-hexaazatriphenylene (HAT)

Reactions of Fe(II) salts with the ligand 1,4,5,8,9,12-hexaazatriphenylene (HAT) led to the isolation and characterization of four new compounds: [Fe3(HAT)(H2O)12](SO4)3.3.3H2O (1), [Fe2(HAT)(SO4)(H2O)5](SO4).2H2O.CH3OH (2), [Fe2(HAT)(SO4)(H2O)5](SO4).3H2O (3), and [Fe3Cl5(HAT)(CH3OH)4(H2O)]Cl (4). Compound 1 crystallizes as a trinuclear cluster in which HAT acts as a tris-chelating ligand. Compounds 2 and 3 are two polymorphs of an infinite one-dimensional structure in which the Fe atoms are coordinated to HAT and then connected into the chain through bridging sulfate anions. Compound 4 exhibits a similar chain structure, but with bridging chloride ligands. The magnetic behavior of the new compounds is indicative of weak antiferromagnetic coupling between the Fe(II) centers through the HAT ligand.     

Gas-phase hydroformylation of propylene on Ru/SiO2 catalysts

Ru/SiO₂ catalysts prepared by reduction of supported RuCl₃·xH₂O are active in gas-phase hydroformylation of propylene at low pressure (ca. 0.3 MPa) of H₂+CO+C₃H₆ mixtured and show unexpectedly high selectivity towards unbranched oxo-products. Data concerning the effect of electronic state and dispersity of Ru on their catalytic behavior have been obtained.

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Ru/SiO₂, RuCl₃·xH₂O, (0,3 ) - . .

     

Single-molecule magnets constructed from cyanometalates: {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Co, Ni)

Treatment of several divalent transition-metal trifluoromethanesulfonates [M(II)(OTf)2; M(II) = Mn, Co, Ni] with [NEt4][Tp*Fe(III)(CN)3] [Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] in DMF affords three isostructural rectangular clusters of {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Mn, 3; Co, 4; Ni, 5) stoichiometry. Magnetic studies of 3-5 indicate that the Tp*Fe(CN)3(-) centers are highly anisotropic and exhibit antiferromagnetic (3 and 4) and ferromagnetic (5) exchange to afford S = 4, 2, and 3 spin ground states, respectively. ac susceptibility measurements suggest that 4 and 5 exhibit incipient single-molecule magnetic behavior below 2 K.     

Synthesis of mesoporous bimetallic Pt-Sn catalytic coatings from polynuclear precursors for fine organic synthesis processes

A new method is developed to obtain nanosized catalytic Pt-Sn/TiO₂ coatings on the inner surface of a capillary microreactor during adsorption of polynuclear carbonyl Pt-Sn complexes on mesoporous TiO₂. Titanium oxide sol prepared in the presence of template (Pluronic F127 surfactant) is supported in dynamic mode. Pt-Sn bimetallic catalysts with an average particle size of 1.5–2 nm are synthesized by adsorption of the bimetallic [Pt₃(CO)₃(SnCl₃)₂(SnCl₂·H₂O)] _n ^2n? complex followed by thermal treatment. Physicochemical properties of samples (thickness, structure and morphology, chemical composition of the material, electronic state, specific surface area, pore volume and size distribution) are characterized by a set of methods (HR TEM, SEM, powder XRD, XRF, XPS, low-temperature nitrogen adsorption). Conditions to prepare the uniform non-peelable Pt-Sn/TiO₂ coating on the inner surface of a silica capillary with good adhesion are determined. To increase the TiO₂ thickness, multilayered TiO₂ films are synthesized by layerby layer deposition. The coating thickness is found to increase with an increase in the capillary diameter. The coating of a capillary with a diameter of 0.55 mm after 14-fold deposition is characterized by a thickness of 2 μm and an average pore size of 5.4 nm. The solvent effect on the adsorption of Pt-Sn carbonyl complexes into the TiO₂ support is studied. The amount of the adsorbed complex increases in the following order: ethanol < acetone ～ tetrahydrofuran. The physicochemical properties of the active component (surface concentration, dispersion, and composition) can be fine-tuned by varying the deposition method, precursor concentration in the initial solution, and temperature conditions of activation treatment. The catalyst activity in citral hydrogenation was 0.06–0.54 min^?1, with the selectivity with respect to unsaturated alcohols reaching 90% at citral conversion above 95%.     

Molecular cube of Re(II) and Mn(II) that exhibits single-molecule magnetism

A pseudocubic, paramagnetic cluster of ReII and MnII, [{MnCl}4{Re(triphos)(CN)3}4], has been prepared, and its magnetic properties have been investigated. Antiferromagnetic coupling is observed between the "S = 1/2" ReII and S = 5/2 MnII centers resulting in an effective S = 8 ground state. AC susceptibility studies reveal that the molecule is a single-molecule magnet with an effective barrier for magnetization reversal of Ueff = 8.8 cm-1.     

Y-type zeolites for the catalytic oxidative degradation of organic azo dyes in wastewater

Cobalt- and iron-containing catalysts active in the oxidation of organic dyes with hydrogen peroxide have been prepared from granular synthetic NaY and HY zeolites without a binder by ion exchange followed by heat treatment at 350–500°C. It has been demonstrated by X-ray photoelectron spectroscopy that cobalt and iron in these catalysts are in the form of Co²⁺ and Fe³⁺ ions on the support surface. The FeHY and CoNaY catalysts are most effective and stable in the oxidation of the anionic dye carmoisine in weakly acidic and alkaline media.     

Effect of Mechanical Treatment on the Reactivity of Copper Powder toward Acetic Acid

The mechanism of the mechanical activation of copper powder is studied by calorimetry, XPS, and X-ray diffraction. The increase in the heat of copper-acetic acid reaction caused by mechanical treatment is due to the activation of dioxygen involved in this reaction. This activation is due to the presence of suboxide oxygen with an increased electron binding energy in mechanically treated copper.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 601–608.Original Russian Text Copyright © 2005 by Poluboyarov, Lapin, Korotaeva, Prosvirin, Bukhtiyarov.     

Effect of the nature of the additives of metal cations (Sr,Ba, and La) on the properties of Co-Mo hydrodesulfurization catalysts

The effect of the nature of the support modified with the ions of alkaline earth and rare earth elements (Sr, Ba, and La) on the properties of Co-Mo catalysts for the hydrodesulfurization of dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied using a set of physicochemical and catalytic techniques. It was found that the introduction of modifying additives decreased the surface concentration of Lewis acid sites (LASs) and increased the concentration of basic sites (BSs) in aluminum-containing supports; these changes were more significant upon modification with lanthanum and strontium. The modification affected the distribution and degree of dispersion of Co-Mo-S sulfide packets. It was found that the rate constants of DBT and 4-MDBT conversion increased with decreasing total surface concentration of both LASs and BSs on the support. The highest rate constant of 4,6-DMDBT conversion was reached at an optimum concentration of weak Lewis sites on Co-Mo catalysts, whose support was modified with strontium or barium.