Amine-tetrachloromethane charge transfer complexes: a structural and computational study

Abstract

Amine-tetrachloromethane charge-transfer complexes have recently been shown to be useful intermediates in transition-metal free solar light-assisted organic synthetic chemistry. Of particular promise is the complex of 1,4-diazabicyclo[2.2.2]octane (DABCO) which may serve as a starting point for several potential reactions involving oxidation of organic compounds. Here we disclose the crystal structure of the [DABCO???CCl₄] complex, and computational studies of two possible complex structures in their ground state, as well as in their first singlet and first triplet excited states.     

Intramolecular van der Waals Interactions Challenge Anion Binding in perthio-Bambusurils

Bambusurils (BUs) are known to be rigid cavitands that feature an extended, jigger-like conformation, and the BU[6]s strongly bind anions within their hydrophobic cavity. These features are not necessarily shared by the family of perthio-BUs. This study reveals that perthio-BUs assume a compact conformation and perthio-BU[6]s are poor anion binders, crystallizing as anion-free species from solutions containing halide salts. Computational studies show that the equatorial sulfur atoms compete against guest anions for binding with the glycoluril methine groups via strong van der Waals (vdW) attractive interactions. These competitive contacts not only account for the diminished anion-binding of perthio-BUs, but also explain their compact conformation. The semithio- and perthio-BU[4]s form linear coordination polymers with Hg^II in the solid-state regardless of their intrinsic molecular conformation. The strong involvement of sulfur atoms in intramolecular interactions differentiates the equatorial from the axial (peripheral) heteroatoms, thus offering chemoselective and regioselective transformations.     

Enantioselective hydrogenation on heterogeneous metal catalysts

The rate of formation of the excess of one enantiomeric product in the enantioselective hydrogenation of ethyl acetoacetate (EAA) and acetylacetone (acac) on a Raney copper catalyst modified with chiral aminoacids (AmA) correlates with the formation constants of the mixed complexes [CU EAA AmA] and [Cu acac AmA].

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() - () , () [Cu··] [Cu··].

     

Cleavage of the siloxane bond in poly(dialkylsiloxanes) by alkyl orthotitanates

Conclusions Linear polydialkylsiloxanes undergo cleavage upon heating with alkyl orthotitanates containing primary and secondary alkyl radicals, and the reactions are independent of the structure of radicals attached to the Si atoms, molecular weight, and the nature of the end groups. The factor which seems to determine the reactivity of polydialkysiloxanes with respect to cleavage at room temperature is the presence of CH end groups. The rate and degree of conversion in these reactions is decreased by increasing steric hindrance at the Si or Ti atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 886–890, April, 1987.     

Thiazolobenzo-1, 2, 3-thiadiazoles and derived cyanine dyes

The following tricyclic heterocyclic compounds are synthesized: 2-methylthiazolov (5, 4-e) benzo-1, 2, 3thiadiazole, 2-methylthiazolo (4, 5-e) benzo-1, 2, 3-thiadiazole, 2-methylthiazolo (4, 5-g) benzo-1, 2, 3-thiadiazole, and 2-methylthiazolo (5, 4-g) benzo-1, 2, 3-thiadiazole. The quaternary salts of these bases are used to prepare symmetrical and unsymmetrical trimethinecyanines and dimethinemercocyanines containing N-ethylrhodanine residues. The absorption maxima of these dyes are shifted toward the long-wave region as compared with the corresponding thiacyanines.     

Elasticity of a cryo-insulation polymer foam coating in the temperature range 8–293 K

An apparatus is developed for investigating the dynamic deformation properties of cryoinsulation coatings in the temperature range 8–293 K. One type of cryo-insulation material — polyurethane foam — is chosen as the object of investigation. Test measurements on a polyurethane foam “pack” (metal substrate with a polyurethane foam coating) are performed at 0.01 Hz in the temperature range 8–293 K. A jump in the temperature dependence of the dynamic shear modulus (by two orders of magnitude) is observed in the temperature range 54–63 K. This feature is attributed to the solidification of the air present in the pores of the polyurethane foam. Such a transition results in cementation of the polyurethane skeleton of the coating by the nitrogen and oxygen “ice” that is formed. Zh. Tekh. Fiz. 69, 116–118 (February 1999)     

Non-Heisenberg Anisotropic Ferrimagnet

Journal of Experimental and Theoretical Physics - The static and dynamic properties of an anisotropic ferrimagnet, which has sublattices with S = 1 and σ = 1/2 and is characterized by a...     

The Results of Studying Nonstationary Processes on the Sun by Radioastronomical Methods

This paper presents the results of studies of solar phenomena performed at the Radiophysical Research Institute (NIRFI) in the last years and based on the data of measuring the solar microwave radiation. We obtained new results concerning fragmentation of the regions of initial energy release during solar flares, their spatial and temporal dynamics, the physical conditions in flaring loops, the dynamics of energetic particles accelerated during flares, and the characteristics of sporadic radio emission during the formation and propagation of coronal mass ejections in the lower layers of the solar atmosphere.