Thermal stability of <Emphasis Type="Italic">meso</Emphasis>-substituted metal corroles in inert and oxidative media

The thermal stability of 5,10,15-triphenylcorrole as the simplest representative of meso-substituted corroles and its complexes with d-metals (Cu³⁺, Mn³⁺, Mn⁴⁺, Co³⁺, Co⁴⁺, and Zn²⁺) is studied for the first time via thermogravimetry in oxidizing and inert atmospheres. It is shown that corroles, both as free ligands and in the form of metal complexes, are less thermally stable than porphyrins with a similar structure. It is found that if the free ligands of porphyrins are thermally more stable with respect to thermal oxidation than d-metal complexes, the thermal stability of metal corroles can be both lower and higher than those of free ligands. It is concluded that the order of thermal stability of compounds MnCor < CoCor < H₃Cor < ZnCorH < CuCor is reversed upon moving from an oxidizing to an inert medium. It is shown that corroles complexes with many d-metals (Co, Mn, and others) readily participate in extracoordination reactions with electron-donating solvents, e.g., DMF, as is indicated by spectrophotometry and thermogravimetry.     

Collective Acceleration of Ions in a Pulsed Magnetic Field of a Conical Spiral

The collective acceleration of laser plasma ions in a magnetic field generated by a powerful fast-growing current pulse in a low-inductive conical spiral is studied. The velocity of ions for a number of elements which significantly differ in atomic weight are obtained on the basis of collector measurements. The maximum velocity of both light (lithium) and heavy (lead) ions exceed the value of 108 cm/s; for ions of lead, the corresponding energy amounts to a value of ∼1 MeV. A mathematical model of ion acceleration is proposed and simulation results are compared with the experiment.     

2-iodylphenol ethers: preparation, X-ray crystal structure, and reactivity of new hypervalent iodine(V) oxidizing reagents

2-Iodylphenol ethers were prepared by the dimethyldioxirane oxidation of the corresponding 2-iodophenol ethers and isolated as chemically stable, microcrystalline products. Single-crystal X-ray diffraction analysis of 1-iodyl-2-isopropoxybenzene 8c and 1-iodyl-2-butoxybenzene 8d revealed pseudopolymeric arrangements in the solid state formed by intermolecular interactions between IO2 groups of different molecules. 2-Iodylphenol ethers can selectively oxidize sulfides to sulfoxides and alcohols to the respective aldehydes or ketones.     

Spectral luminescence properties of Ca1 ? x Sr x F2:Ce3+ (0 < x <1) crystals

The luminescence, reflection, and luminescence excitation spectra of two-component Ca_{1 ? x} Sr _x F₂:Ce³⁺ (0.05 mol %) (x = 0.14, 0.25, 0.4, 0.6, and 0.75) have been studied at room temperature and T = 8 K. It is shown that the luminescence bands (upon 130-eV photon excitation) in the range of 200 to 400 nm are attributed to singlet and triplet self-trapped exciton luminescence and to 5d-4f transitions in Ce³⁺.     

Molecular and crystal structure of 4′-cyanobenzo-15-crown-5

The crystal structure of 4′-cyanobenzo-15-crown-5 is determined by X-ray diffraction. The crystallographic parameters of single crystals are as follows: a = 40.479(6) Å, b = 8.821(2) Å, c = 8.484(2) Å, β = 93.94(2)°, V = 3022.2 ų, Z = 8, d _calcd = 1.27 g/cm³, and space group C2/c. The structure is solved by the direct method and refined by the least-squares procedure to R = 0.068. The conformation of the macrocycle in 4′-cyano-B15C5 is described by the a-a-g ^? -a-a-g-g ^? -a-a-g-a-g-a-a-s sequence of torsion angles.     

Gated spin relaxation in (1 1 0)-oriented quantum wells

Growth, photoluminescence characterisation and time-resolved optical measurements of electron spin dynamics in (1 1 0)-oriented GaAs/AlGaAs quantum wells are described. Conditions are given for MBE growth of good-quality quantum wells, judged by the width of low-temperature excitonic photoluminescence. At 170 K the electron spin relaxation rate in (1 1 0)-oriented wells shows a 100-fold reduction compared to equivalent (1 0 0)-oriented wells and also a 10-fold increase with applied electric field from 20 to 80 kV cm⁻¹. There is evidence for similar dramatic effects at 300 K. Spin relaxation is field independent below 20 kV cm⁻¹ reflecting quantum well asymmetry. The results indicate the achievability of voltage-gateable quantum well spin memory time longer than 10 ns at room temperature simultaneously with high electron mobility.