A Sterically Hindered Derivative of 2,1,3-Benzotelluradiazole: A Way to the First Structurally Characterised Monomeric Tellurium–Nitrogen Radical Anion

Interaction of the tetradentate redox-active 6,6′-[1,2-phenylenebis(azanediyl)]bis(2,4-di-tert-butylphenol) (H₄L) with TeCl₄ leads to neutral diamagnetic compound TeL ( 1 ) in high yield. The molecule of 1 has a nearly planar TeN₂O₂ fragment, which suggests the formulation of 1 as Te^IIL²⁻, in agreement with the results of DFT calculations and QTAIM and NBO analyses. Reduction of 1 with one equivalent of [CoCp₂] leads to quantitative formation of the paramagnetic salt [CoCp₂]⁺[ 1 ]^.−, which was characterised by single-crystal XRD. The solution EPR spectrum of [CoCp₂]⁺[ 1 ]^.− at room temperature features a quintet due to splitting on two equivalent ¹⁴N nuclei. Below 150 K it turns into a broad singlet line with two weak satellites due to the splitting on the ¹²⁵Te nucleus. Two-component relativistic DFT calculations perfectly reproduce the a(¹⁴N) HFI constants and A_∥(¹²⁵Te) value responsible for the low-temperature satellite splitting. Calculations predict that the additional electron in 1 ^.− is localised mainly on L, while the spin density is delocalised over the whole molecule with significant localisation on the Te atom (≥30 %). All these data suggest that 1 ^.− can be regarded as the first example of a structurally characterised monomeric tellurium–nitrogen radical anion.     

Experimental study of electron density distribution in crystals of antimony(V) dicarboxylate complexes

Structural Chemistry - The molecular structure and charge density distribution in the crystals of triphenylantimony bis[(2E)-3-phenylprop-2-enoate] [Ph3Sb(O2CCH=CHPh)2] and triphenylantimony...     

Flow of a fluid across an obstacle with breaking of the wave front

The phenomenon of breaking of surface gravity waves on the sea in a coastal zone has much in common with a steady hydraulic jump. When surface waves break a vortex forms which rolls down along the leading slope of the wave, as in the case of the formation of a hydraulic jump. Up to the present time a number of theoretical flow models have been proposed for the region in which a wave front breaks. Many of these studies are discussed in [1, 2]. However, the questions of the origin and dynamics of the vortex and its effect on the flow remain open. With the object of studying these questions in greater detail, the results are given below of numerical and experimental simulation of a hydraulic jump. The results of numerical calculations of the shape of the free surface and the velocity profiles in the various sections agree fairly well with the experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 103–106, May–June, 1985.     

Telluride clusters of molybdenum: Synthesis, structures, and NMR spectra

High-temperature reactions of Mo, chalcogen (S or Se), Te, and Br₂ in molar ratio Mo: S/Se: Te: Br = 3: 1: 6: 4 were carried out. The reaction products were subjected to mechanochemical activation with K(Dtp) (Dtp = (EtO)₂PS₂) in a vibrational mill, resulting in the formation of new compounds [Mo₃(μ₃-Q)_0.5(μ₃-O)_0.5(μ₂-Te₂)₃(Dtp)₃](Dtp) (Q = Se (I) and S (II)). The structure of compound I has been established by X-ray diffraction analysis. Solutions of compounds I and II contain mixtures of [Mo₃(μ₃-Q)(μ₂-Te₂)₃(Dtp)₃]⁺ and [Mo₃(μ₃-O)(μ₂-Te₂)₃(Dtp)₃]⁺, which is confirmed by mass spectrometry and ³¹P, ⁷⁷Se, and ¹²⁵Te NMR spectroscopy. Quantum-chemical calculations of the ¹²⁵Te NMR chemical shifts were performed. The compounds are also characterized by IR spectroscopy, Raman spectroscopy, and elemental analysis. Structure I contains short nonvalent contacts between the sulfur atom of the out-of-sphere Dtp anion and the axial tellurium atoms of the cluster.     

Reaction of [HO(CH2)3]3P with α,β-Unsaturated Ketones Containing a Phenylpropanoid Backbone

Abstract

Interaction of 3,4-(MeO)₂-benzylideneacetone with [HO(CH₂)₃]₃P (THPP) was studied in CD₃OD by NMR to compare reactivity of a phenylpropanoid α,β-unsaturated ketone with a corresponding α,β-unsaturated aldehyde. In the presence of HCl, both the ketone and a related cinnamaldehyde first establish an equilibrium with the product formed by nucleophilic attack of the THPP at the C?O bond, [ArCH?CHCX(OD)PR₃]⁺Cl^?(X?H or CH₃, Ar?Ph or 3,4-(MeO)₂C₆H₃). The ketone salt then slowly transforms into [R₃PCH(Ar)CH(D)C(O)CD₃]⁺Cl^?, the phosphonium product of nucleophilic attack of THPP at the C?C bond, whereas the final product from the aldehyde is the (α-ether)phosphonium chloride [ArCH?CHCH(OCD₃)PR₃]⁺Cl^?. In aqueous media, in the absence of HCl, 4-HO-benzylideneacetone, which is similar to a lignin-type, α,β-unsaturated aldehyde model compound, interacts with THPP to afford a stable phosphonium zwitterion, in contrast to the previously studied aldehyde model, which forms dimeric, bisphosphonium products.     

Acceleration complex for extreme ultraviolet nanolithography based on a free-electron laser with kilowatt-scale average radiation power

The project of an acceleration complex is described that is based on a 0.7-GeV superconducting linear accelerator for the free-electron laser used for extreme ultraviolet lithography at a 13.5-nm wavelength with a 0.5-kW average power of laser radiation, as well as for examination of materials using X-ray and vacuum-ultraviolet radiations.     

Acceleration of a body in a channel in the quasi-one-dimensional magnetohydrodynamic approximation

Translated from Pryamye i Obratnye Zadachi Matematicheskoi Fiziki, pp. 248–258, 1991.