Generation of a Hetero Spin Complex from Iron(II) Iodide with Redox Active Acenaphthene-1,2-Diimine

The reaction of the redox active 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-BIAN) and iron(II) iodide in acetonitrile led to a new complex [(dpp-BIAN)Fe^III₂] (1). Molecular structure of 1 was determined by the single crystal X-ray diffraction analysis. The spin state of the iron cation in complex 1 at room temperature and the magnetic behavior of 1 in the temperature range of 2–300 K were studied using Mossbauer spectroscopy and magnetic susceptibility measurements, respectively. The neutral character of dpp-BIAN in 1 was confirmed by IR and UV spectroscopy. The electrochemistry of 1 was studied in solution and solid state using cyclic voltammetry. The generation of the radical anion form of the dpp-BIAN ligand upon reduction of 1 in a CH₂Cl₂ solution was monitored by EPR spectroscopy.     

Growth kinetics,structure and surface morphology of AlN/α-Al2O3 epitaxial layers

The gas-phase epitaxy of AlN on saphire substrates in the system Al HCl NH₃–Ar was investigated. The uniformity and structural perfection of the layers were shown to be determined by gas dynamics in the growth zone. The growth rate of AlN-layer is proportional to AlCl concentration in the growth zone and does not depend on NH₃ partial pressure. This is in accordance with the law of diffusional stoichiometry. The morphology of AlN-layers was shown to be dependent on the growth rate and the substrate orientation. Smooth mirror-like layers were prepared on the sapphire planes (0001) and (1120) at low growth rates. X-ray microanalysis showed the oxygen impurity content at the level 1 — 5 · 10²¹ cm⁻³. Other impurities were not available.     

Refractive index of chalcogenide glasses over a wide range of compositions

The refractive index frequency dependence in the 1–11 μm range for AsSe, GeSe and AsGeSe glassforming systems and for three- and four-component systems obtained by substitution of antimony, bismuth, tin, lead, sulphur and tellurium for arsenic, germanium and selenium, being their periodic system counterparts, is investigated. A comparison of optical constants of chalcogenide glasses with those for other optical materials by means of constructing of an Abbe-type diagram in n_2.0 ? v_2.0 coordinates is considered. The possibility of chalcogenide glass refraction calculation by means of additive formulas is discussed. It is shown that critical points on the property-composition curves coincide with structural region boundaries in all of the investigated systems. These data are considered as further experimental support for the polymer nature of chalcogenide glasses.     

Carrier spin dynamics in GaAs/AlGaAs quantum wells with a laterally localizing electric potential

The spin orientation dynamics in a GaAs quantum well with a laterally nonuniform electric potential generated by a mosaic electrode deposited on the surface of the sample has been investigated using the photoinduced magneto-optical Kerr effect. It has been found that the application of a negative potential higher than 1 V to the electrode leads to more than a hundredfold increase in the spin polarization lifetime in the sample under study. It is concluded that so strong slowing down of the relaxation is caused by a combined action of two effects, namely, the spatial separation of electron and hole, which reduces the radiative recombination rate of electron-hole pair, and the localization of electron, which is accompanied by the suppression of spin relaxation processes caused by electron motion.     

Structural transitions in ice samples at low temperatures and pressures

The structure of ice samples formed in the decay of a water impurity gel at temperatures above 4 K and atmospheric pressure has been examined. The X-ray diffraction analysis indicates that three phases coexist in the initial sample at temperatures of 85–110 K. These phases are amorphous ice occupying up to 30% of the sample volume, cubic-phase ice I _c metastable at low pressures (∼60%), and normal hexagonal ice I _h (≤6%). The characteristic sizes of crystals of the cubic and hexagonal phases are about 6 and 30 nm, respectively. The amorphous phase at annealing above 110 K is gradually transformed to the crystalline phase both cubic and hexagonal. This transition is accompanied by two processes, including a fast increase in the sizes of cubicphase nanocrystals and the partial transition of the cubic phase I _c to the hexagonal one I _h. Hexagonal ice I _h prevails in the bulk of the sample above 200 K.     

Selective electroreduction of dinitrogen on a rotating copper amalgam electrode

On an amalgamated rotating copper disk electrode in an alkaline methanol solution in the presence of mixed Ti(OH)₃–Mo(III) hydroxide, dinitrogen is shown to be selectively electroreduced to hydrazine in the potential range –1.6 to –1.9 V (with respect to the saturated calomel electrode).

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, Ti(OH)₃–Mo(III) –1,6+ –1,9 ( ) .

     

Arylsulfonyl chlorides in the presence of N-methylimidazole as efficient condensing reagents in phosphotriester oligonucleotide synthesis

It was shown that arylsulfonyl chlorides in the presence of N-methylimidazole are powerful condensing agents for the triester internucleotide bond formation.