Palladium–N‐Heterocyclic Carbene (NHC)‐Catalyzed Asymmetric Synthesis of Indolines through Regiodivergent C(sp3)H Activation: Scope and DFT Study

Two bulky, chiral, monodentate N‐heterocyclic carbene ligands were applied to palladium‐catalyzed asymmetric C?H arylation to incorporate C(sp³)?H bond activation. Racemic mixtures of the carbamate starting materials underwent regiodivergent reactions to afford different trans‐2,3‐substituted indolines. Although this C_Ar?C_alkyl coupling requires high temperatures (140–160 °C), chiral induction is high. This regiodivergent reaction, when carried out with enantiopure starting materials, can lead to single structurally different enantiopure products, depending on the catalyst chirality. The C?H activation at a tertiary center was realized only in the case of a cyclopropyl group. No C?H activation takes place alpha to a tertiary center. A detailed DFT study is included and analyses of methyl versus methylene versus methine C?H activation is used to rationalize experimentally observed regio‐ and enantioselectivities.     

Neutron Irradiation Effect on the Hardness of Nickel Titanium Alloy Modified by Krypton Ions

Russian Physics Journal -     

Electrochemical reactions of Co(II), Cu(II), and Zn(II) complexes with 4-(2′-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-1-oxyl

Electrochemical reactions of Co(II), Cu(II), and Zn(II) complexes with 4-(2-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-1-oxyl are studied by voltammetry and electrolysis-EPR. The radical centers of the ligands in these complexes undergo one-electron irreversible oxidation and reduction. In the Co(II) and Cu(II) complexes, the metals also undergo one-electron oxidation and reduction, respectively.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2750–2754, December, 1991.     

Complexes of cobalt(2+) chloride with hydrochlorides of N-(1,2,4-triazol-5-yl)- and N-(tetrazol-5-yl)benzamidines

We have synthesized complex compounds of Co(2+) chloride with hydrochlorides of N-(1,2,4-triazol-5-yl)benzamidine and N-(tetrazol-5-yl)benzamidine. According to magnetochemistry and electron spectroscopy data, the ligands are coordinated in a bidentate fashion with the N atom of the amidine group and the N atom of the heterocycle with formation of the tetrahedral chromophore CoN₂Cl₂.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2311–2315, October, 1992.     

The peculiarities of behavior of nuclei remagnetization in a magnetic field in uniaxial films

The influence of magnetic field on the structure and properties of magnetic inhomogeneities generated in the defects of the type of “potential well” in magnetic uniaxial films has been theoretically investigated. It is shown that the behavior of high-amplitude and low-amplitude inhomogeneities in the magnetic field varies considerably, and the causes of such differences are identified. It is established that in some cases, when these inhomogeneities do not exist in the absence of a field, they can be induced in a nonzero field. Possibilities to identify both types of heterogeneities at their experimental detection are considered.     

Cold compression of nuclei induced by antiprotons

On the basis of a dynamical Relativistic Mean Field (RMF) model we study the response of a nucleus on an antiproton implanted in its interior. We solve the Vlasov equation for the p?-nuclear system assuming different strengths of attractive p? potential and show that a compressed state is formed on a rather short time scale of about 4?÷?10 fm/c. The evolution of the system after p? annihilation is simulated using the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model. Finally, several observables sensitive to the p? annihilation in a compressed nuclear configuration are proposed, e.g. the nucleon kinetic energy spectra and the total invariant mass distributions of produced mesons.     

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.     

Bose condensation of interwell excitons in lateral traps: A phase diagram

The luminescence of interwell excitons in GaAs/AlGaAs double quantum wells (n-i-n heterostructures) containing large-scale random-potential fluctuations was studied. The study dealt with the properties of an exciton whose photoexcited electron and hole are spatially divided between the neighboring quantum wells under density variation and at temperatures of down to 0.5 K. We investigated domains ∼1 μm in size, which act as macroscopic exciton traps. Once the resonance laser pump power reaches a certain threshold, a very narrow delocalized exciton line appears (with a width less than 0.3 meV), which grows strongly in intensity with increasing pump power and shifts toward lower energies (by approximately 0.5 meV) in accordance with the exciton buildup in the lowest state in the domain. As the temperature increases, this spectral line disappears in a nonactivated manner. This phenomenon is assigned to Bose condensation occurring in the quasi-two-dimensional system of interwell excitons. The critical exciton density and temperature were determined within the temperature interval studied (0.5 to 3.6 K), and a phase diagram specifying the exciton condensate region was constructed. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 1, 2004, pp. 168–170. Original Russian Text Copyright ? 2004 by Dremin, Larionov, Timofeev.