Neutron reflection from a helical system

Analytical expressions for neutron reflection and transmission by magnetic mirrors with helical magnetization are derived. Reflectance curves with and without neutron spin flip are presented. Resonant properties of helical systems are studied.     

Disordering in the crystal structures of thienylgermatranes

The crystal structure of a series of thienylgermatranes has been studied using X-ray diffraction. Disorder of the thiophene ring in a 2-thienylgermatrane has been established. In the same positions of the unit cell of the crystal there are found both molecules with an O(2)-Ge-C-S torsional angle of −166.8(4)° and molecules in which this angle is 14.0(4)°. The lengths of the transannular N→Ge bonds (2.183–2.283 Å) agrees in value with the values of crystalline germatrane structures with a Ge-C bond. The length of the transannular N→Ge bond (2.248 Å) in 4-(2-thienyl)phenylgermatrane (molecule A) is the largest amongst germatranes with a Ge-C_ar bond. Introduction of a second thiophene ring into the 2-thienylgermatrane molecule lowers the acute toxicity of the compound by about 27 times (LD₅₀ for the 2,2′-bithienylgermatrane = 447 mg/kg). __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 299–306, February, 2007.     

Synthesis and psychotropic properties of furyl- and thienyl-germatranes

Trihalogermyl-furans and -thiophenes were prepared by inserting germanium dibromide (GeBr₂) generated from the dibromogermane(II) dioxanate complex into the carbon-halogen bond of halo-furans and -thiophenes. Their ethanolysis and transesterification by triethanolamine yielded the germatranes which were subjected to psychotropic activity assays. The psychotropic properties of germatranes were found to depend on the type of the heterocycle and on the position of the germatrane moiety.     

Hydrogermylation of phenylacetylene catalyzed by onium chlorometallates

Triethylbenzylammonium chlorometallates [Et₃NCH₂Ph][MCl_n]^m? (M = Pt, Pd, Rh, Ir, Fe, Co, Cu, m = 1–3, n = 3–6), polymer-anchored ionic metal complexes [?—CH₂PBu₃][MCl_n]^n? and some other chlorometallates and complexes of platinum, rhodium, ruthenium and osmium were studied as catalysts in the hydrogermylation of phenylacetylene with triethylgermane. All the complexes containing platinum, palladium and rhodium were found to be effective catalysts. The cis/trans ratio of the products obtained is determined by the metal atom involved and decreases in the following order: Ir > Rh ? Pd > Pt.     

A new method for the synthesis of silicon-and germanium-containing 2-acetylfurans and 2-acetylthiophenes

A new method was developed for the synthesis of silicon-and germanium-containing acetylfurans and acetylthiophene by metallation of 2-acetylfuran or 2-acetylthiophene with n-BuLi at low temperature after protection of the carbonyl group with lithium N-methylpiperazide and reaction of the lithium derivative with various trialkyl-, alkylphenyl-, and cycloalkylchlorosilanes or trialkylchloro(bromo)germanes. The cytotoxic activity of the new compounds was studied, and it was established that the silicon-and germanium-containing acetylfurans and acetylthiophenes are substances with low toxicity (LD₅₀ 312->2000 mg/kg) and have low cytotoxicity toward HT-1080 and MG-22A tumor cells. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 192–199, February, 2007.     

The local field effects in resonance Raman scattering Structural anisotropy studies in some nematic cyanophenyl derivatives

Abstract

Different methods for the determination of the local field anisotropy in liquid crystals are analysed and the problems resulting from their application are outlined. One such method, namely that based on the comparison of the polarization of resonance Raman scattering and absorption bands is studied in more detail. The method is applied to determine the structural anisotropy for the 4-n-pentyl-(4′-cyanophenyl) derivatives of benzene, cyclohexane and bicyclooctane. To account for the difference between the optical properties of the probe and of the solvent at the wavelength of the scattered light the local field factor is treated theoretically within the framework of an anisotropic continuous dielectric medium.     

Synthesis of thiacyanine dyes containing coumarin moieties at benzothiazole rings

New bischromophoric dyes (thiacarbocyanine and thiadicarbocyanine) containing coumarin moieties at each of the two benzothiazole systems, as well as monomethinecyanine containing coumarin moiety at only one heterocyclic system, manifest significant batho-chromic shift compared to relative coumarin-free dyes.