Reactivity of some “ladder” type complexes under conditions of metallation

The behavior of binuclear “ladder” type complexes FpL, where Fp=Cp(CO)₂Fe, L=p-MeC₆H₄Cr(CO)₃ (4), CH₂C₆H₅Cr(CO)₃ (5), andp-FpC₆H₄Cr(CO)₃ (6), under conditions of metallation was studied. Unlike compounds5 and6, the σ-bound ligand L in compound4 migrates from the iron atom to the cyclopentadienyl ring to give complexes Me(CO)₂FeC₅H₄−C₆H₄(p-Me)Cr(CO)₃. The electrochemical reduction potentials of the complexes4–6 and the rearrangement products were measured. The migration activity of L is determined by the ease of reductive cleavage of the Fe−L bond and the susceptibility of the system to undergo intramolecular electron transfer from the Cp ligand to the aromatic ring. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1832–1835, September, 1998.     

Universal adaptive lattice filters. Adaptation for a given root of the estimating correlation matrix

Algorithms for the adjustment of adaptive lattice filters according to a given root of the estimating noise-correlation matrix (CM) are considered. A basic algorithm is synthesized from which can be derived adjustment algorithms that take into account a priori information on the CM structure. Methods for simplification of the algorithm and increasing its efficiency are examined.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Photoluminescence of porous silicon coated by SILD method with LaF3 nanolayers

The method of lanthanum fluoride passivating layer synthesis in the matrix of porous silicon by successive ionic layer deposition was elaborated and optimized. Luminescence and FTIR of obtained structures demonstrate the crucial role of the chemical composition of silicon nanocrystallite surface in the formation of radiative recombination channels and in the stability of porous silicon photoluminescence. The combination of high optical transparency of LaF₃ layers and low recombination losses in silicon covered with such layers allows to recommend the lanthanum fluoride film as an effective passivating coating for silicon optoelectronics devices.     

Study of the catalytic activity of electrochemically reduced forms of phthalocyanines in the reaction of CO2 with epoxides

Catalytic activity of electrochemically reduced forms of mono- and diphthalocyanine complexes of transition and rare-earth elements in the reaction of carbon dioxide with epoxides is considerably higher than that of corresponding neutral forms. The catalytic efficiency depends on the nature of the phthalocyanine complex, the method of the catalyst immobilization, and the electrophilicity of epoxide. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2205–2213, November, 1998.     

Synthesis and characteristics of novel pentanuclear complexes [(OC)3Mn(η1,η5-C5H4)Fe(CO)2(η1,η5-C5H4CO2)]2M(η5-C5H5)2 (M=Ti, Zr)

The reaction of Cp₂MCl₂ complexes (M=Ti and Zr) with 2 equiv. of (OC)₃Mn(η¹,η⁵-C₅H₄)Fe(CO)₂(η⁵-C₅H₄COONa) results in the formation of the pentanuclear complexes (OC)₃Mn(η¹,η⁵-C₅H₄)Fe(CO)₂(η⁵-C₅H₄CO₂)]₂M(η⁵-C₅H₅)₂, which are characterized by IR and¹H NMR spectroscopy and cyclic voltammetry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1055–1058, May, 1997.     

Low-temperature Magnetic Properties of Terbium Orthoferrite Single Crystals

Spontaneous and by an external magnetic field induced magnetic phase transitions in TbFeO₃ have been experimentally studied. Precision investigations of velocities of transmission and attenuation of sound wave were made, the processes of formation and rearrangement of magnetic structure examined and its change under the influence of external magnetic field explored. This has been made possible by the development of methods of controlled growth of rare-earth orthoferrites resulting in the formation of high-quality single crystals of required size with reproducible physical properties. The measurements were taken in the temperature range from 0.45 to 8.0 K. From the threshold Geld values a H_a  T phase diagram for TbFeO₃ has been plotted.     

Superdiffusion and viscoelastic vortex flows in a two-dimensional complex plasma

Viscoelastic vortical fluid motion in a strongly coupled particle system has been observed experimentally. Optical tracking of particle motion in a complex plasma monolayer reveals high grain mobility and large scale vortex flows coexistent with partial preservation of the global hexagonal lattice structure. The transport of particles is superdiffusive and ascribed to Lévy statistics on short time scales and to memory effects on the longer scales influenced by cooperative motion. At these longer time scales, the transport is governed by vortex flows covering a wide spectrum of temporal and spatial scales.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.