Enantioselective catalysis by metal complexes. 5. Asymmetric hydrosilylation using the phosphine complex [Rh(COD)Cl]2/(S)-Phephos

The complex [Rh(COD)Cl]₂/(S)-Phephos is demonstrated to be highly active and enantioselective in model hydrosilylation of acetophenone by diphenylsilane. The enantioselectivity increases as the reaction temperature increases. This allows the reaction to be carried out at acetophenone/Rh ratios up to 20,000. A mathematical model of the reaction using Rh/(S)-Phephos is constructed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1951–1955, September, 1990.     

Influence of crystallite-boundary potential barriers on the thermopower and peltier effect in polycrystalline ferroelectric semiconductors

The influence of local charged states at crystallite boundaries on the thermoelectric effects in polycrystalline ferroelectrics is considered. It is shown that the differential thermopower and the Peltier coefficient depend on the height of the crystallite-boundary potential barriers. The possible manifestation of an anomalous behavior of the thermopower in the vicinity of the Curie ferroelectric point is demonstrated.     

Quantitative Comparison of LDA + DMFT and ARPES Spectral Functions

JETP Letters - The emergence of angle-resolved photoemission spectroscopy (ARPES) made it possible to observe electronic dispersion directly as a spectral function map. On the other hand, a...     

Synthesis,structure, and optical properties of iridium(III) complex with 1-benzyl-2-phenylbenzimidazole and 4,4'-dicarboxy-2,2'-bipyridyne

A new cyclometalated iridium(III) complex [Ir(L)₂(Hdcbpy)] (1) has been synthesized, where L is 1-benzyl-2-phenylbenzimidazole and Hdcbpy is monoprotonated 4,4′-dicarboxy-2,2′-bipyridine. The structure of complex 1 has been determined by X-ray diffraction. The optical properties of complex 1 have been studied, and the quantum yield of luminescence has been measured.     

Analytical Applications of Enzymatic Growth of Quantum Dots

We have developed an analytical assay to detect the enzymatic activity of acetylcholine esterase and alkaline phosphatase based on the generation of quantum dots by enzymatic products. Acetylcholine esterase converts acetylthiocholine into thiocholine. The latter enhances the rate of decomposition of sodium thiosulfate into H₂S, which in the presence of cadmium sulfate yields CdS quantum dots showing a time dependent exponential growth, typical of autocatalytic processes. This assay was also applied to detect acetylcholine esterase inhibitors. Alkaline phosphatase hydrolyzes thiophosphate and yields H₂S, which instantly reacts with Cd²⁺ to give CdS quantum dots. The formation of CdS quantum dots in both reactions was followed by fluorescence spectroscopy and showed dependence on the concentration of enzyme and substrate.     

Mesoscopic simulation of the self-organization of a binary mixture of copolymers in the vicinity of a selective adsorbing surface

A new strategy for the construction of ultrathin structured films with cylindrical microdomains oriented primarily perpendicularly to the surface of a solid substrate is proposed. This approach is based on the phase separation of a binary mixture of incompatible compositionally asymmetric block copolymers, microphase separation of their blocks, and selective adsorption of one of the copolymers on the surface. Preferentially adsorbed copolymer forms a regular pattern on the surface, which serves as an orienting support for another component that dominates in the system and forms the hexagonal mesophase in the bulk of the film. This approach has been verified by the mesoscopic simulation based on the dynamic version of the density functional theory. As a result of the self-organization of macromolecules, the morphology with perpendicularly oriented domains can be thermodynamically stable for the films with a thickness of ∼100 nm. The commensurability of the parameters of the surface pattern and volume mesophase is shown to be the key factor controlling the orientation of cylindrical microdomains.     

Dynamic birefringence of poly(styrene-4-sulfonate sodium) macromolecules in aqueous solutions at high ionic strengths

For samples of various molecular masses, the flow birefringence of poly(styrene-4-sulfonate sodium) macromolecules in aqueous solutions at various ionic strengths is studied in relation to the concentration of NaCl. It is shown that the sign of birefringence changes from negative to positive with an increase in the ionic strength of a solution. Application of the macroform theory to the Maxwell effect makes it possible to estimate the intrinsic optical anisotropy of the repeating unit of poly(styrene-4-sulfonate sodium) (a||- a⊥) = −17 × 10^-25 cm³), which nearly coincides with similar values known for atactic polystyrene and poly(κ-methylstyrene).     

A polymer in an ionic liquid: Structural properties of a system during attraction between the polymer and cations of the ionic liquid

In terms of the polymer integral equation theory, structuring in ionic liquids containing flexiblechain polymers under the conditions of good solubility is studied for the first time. The influence of the polymer concentration on the structural properties of system components is studied at different lengths of polymer molecules. The structural organization of the ionic liquids is shown to be fairly stable after addition of the polymer. When there is attraction between the polar groups of cations of the ionic liquid and polymer molecules, the calculated structural factors suggest intermediate-range scales of polymer-component ordering. Given this, for any considered length of polymer molecules, there is a range of polymer concentrations in which the characteristic scale of ordering decreases with an increase in polymer density according to a power law.     

Quantization of branched coverings

We identify branched coverings (continuous open surjections p: Y → X of Hausdorff spaces with uniformly boundedly many preimages) with Hilbert C*-modules C(Y) over C(X) and with faithful unital positive conditional expectations E: C(Y) → C(X) that are topologically of finite index. The case of nonbranched coverings corresponds to finitely generated projective modules and expectations that are (algebraically) of finite index. This enables us to define noncommutative analogs of (branched) coverings.