Fluorescent probe 4-dimethylaminochalcone: Solvatochromism according to the data of semiempirical and quantum-chemical calculations

The solvatochromic regularities observed in solutions of 4-dimethylaminochalcone (DMCh) are investigated in terms of two independent theoretical approaches, i.e., semiempirical and quantum-chemical, and the results of these investigations are directly compared with each other for the first time. It has been shown that the values of the absolute solvation shift of the long-wavelength DMCh electronic absorption band determined by different methods are in a good quantitative agreement both with each other and with experimental data. This fact can be considered as a substantial additional justification of the conclusion on the predominantly nonspecific origin of intermolecular forces determining the mechanisms by which the DMCh fluorescent probe functions in biological systems.     

Magnetooptical,optical, and magnetotransport properties of Co/Cu superlattices with ultrathin cobalt layers

We investigated the field dependences of the magnetization and magnetoresistance of superlattices [Co(t _x, Å)/Cu(9.6 Å)]30 prepared by magnetron sputtering, differing in the thickness of cobalt layers (0.3 Å ≤ t _Co ≤ 15 Å). The optical and magnetooptical properties of these objects were studied by ellipsometry in the spectral region of hω= 0.09–6.2 eV and with the help of the transverse Kerr effect (hω= 0.5–6.2 eV). In the curves of an off-diagonal component of the tensor of the optical conductivity of superlattices with t _Co = 3–15 Å, a structure of oscillatory type (“loop”) was detected in the ultraviolet region, resulting from the exchange splitting of the 3d band in the energy spectrum of the face-centered cubic structure of cobalt (fcc Co). Based on magnetic experiments and measurements of the transverse Kerr effect, we found the presence of a superparamagnetic phase in Co/Cu superlattices with a thickness of the cobalt layers of 3 and 2 Å. The transition from superlattices with solid ferromagnetic layers to superparamagnetic cluster-layered nanostructures and further to the structures based on Co and Cu (t _Co = 0.3–1 Å) with a Kondo-like characteristics of the electrical resistivity at low temperatures is analyzed.     

Theoretical analysis of the IR spectrum of methyl-3,4-anhydro-α-D-talohexopyranoside

A detailed interpretation of the IR spectrum of methyl-3,4-anhydro-α-D-talohexopyranoside that is based on complete calculation of normal vibration frequencies and absolute IR absorption band intensities of the molecule and a comparison of the results obtained with the corresponding experimental data is given for the first time. The influence of the epoxy group on the absorption bands characteristic of the pyranose ring has been analyzed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 597–605, September–October, 2008.     

Oxidation of hydrocarbons with dioxygen via peroxide intermediates

Cyclohexane, cyclohexene, and -pinene react with dioxygen in the liquid phase in the presence of catalysts based on platinum, heteropoly compounds (HPCs), metal-containing HPCs, and combinations of these components. In cyclohexane and -pinene oxidations occurring by an autooxidation mechanism at 160–170 and 80– 90°C, respectively, the catalysts serve to control free-radical processes. The simultaneous action of a Ru-containing phosphotungstate as a hydroperoxide decomposition catalyst and of a V-containing phosphotungstate as a scavenger of hydroxyl and alkoxyl radicals increases the cyclohexanol + cyclohexanone selectivity of cyclohexane oxidation without yielding a hydroperoxide. A Pt/C catalyst affords an increase in -pinene conversion in a fixed time. In combination with ammonia or tetrahexylammonium chloride admixtures, it retards side reactions and raises the yield of verbenol and verbenone, which are the most valuable products. During cyclohexane, cyclohexene, and -pinene oxidation with an O₂-H₂ mixture at room temperature, no free-radical chain reaction develops in the Pt-HPC system and reactive intermediates form and interact, involving the HPC, with hydrocarbons on the surface of the platinum catalyst. Analysis of reactivity and of the composition of substrate oxidation products suggests a mechanism for the conjugate oxidation of hydrocarbons in systems with various HPCs. In this mechanism, HPC composition determines, to a large extent, the nature of reactive intermediates, which may be peroxides or radicals bound to platinum or HPC. The properties of catalytic systems in oxidation with O₂-H₂ mixtures can be controlled by selecting an appropriate HPC as the modifying component.__________Translated from Kinetika i Kataliz, Vol. 46, No. 2, 2005, pp. 219–232.Original Russian Text Copyright © 2005 by N. Kuznetsova, L. Kuznetsova, Kirillova, Detusheva, Likholobov, Khramov, Ansel.     

Complexes of alkylenediphosphine dioxides with uranyl nitrate

Conclusions A number of complexes of tetraaryl (alkyl) alkylenediphosphine dioxides with uranyl nitrate have been synthesized. Coordination of both P=O groups with the uranyl ion is observed in the complexes of methylenediphosphine and cis-tetraarylvinylenediphosphine dioxides; in complexes of trans-tetraaryl (alkyl) vinylenediphosphines, only one P=O group is involved in complexing. Tetraphenylethylenediphosphine dioxide forms both types of complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1714–1721, August, 1978.We thank A. M. Rozen for discussing the results.     

Explicit solutions of superized toda lattices

Explicit solutions are constructed for superized Toda lattices associated with systems of simple roots of classical Lie superalgebras. The completeness of flows and the asymptotic behavior of systems are studied.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 123, pp. 98–111, 1983.     

Porphyrins. 15. Effect of stesic factors on the orientation of meso substitution in the formylation of porphyrins. First example of the chromatographic identification of isomers of porphyrins of the I and II types

The Cu and Ni complexes of etioporphyrin II were subjected to Vilsmeier formylation, and a steric effect of the peripheral substituants on the direction of electrophilic meso substitution in the porphyrins was observed. The corresponding meso-N,N-dimethylaminomethyl derivatives, which were separated by thin-layer chromatography (TLC) on silica, gel, were obtained. Their structures were proved by means of the IR, PMR, electronic, and mass spectra.See [1] for Communication 14.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1507–1511, November, 1982.     

Optimization of linear systems by the methods of functional analysis

This paper presents a survey of recent work dealing with the optimization of linear systems by the methods of functional analysis. The areas covered are: application of the separability theorem of convex sets, application ofL-problem of moments, computational aspect of the theory of optimal control, problems of controllability (including a new view of the theory), problems of observability, and problems of pursuit.