Synthesis and structure of a new selenium-bridged tungsten cluster, [W3Se7(S2P(OEt)2)3]Br

[W₃Se₇(S₂P(OEt)₂)₃]Br was prepared by reacting (Et₄N)₂W₃Se₇Br₆ with KS₂P (OEt)₂ in CH₃CN and its crystal structure determined. In the [W₃(μ₃-Se)(μ₂-Se₂)₃]⁴⁺ core the W---W bond length is 2.755(5)-2.764(6) Å and the Se---Se bond length is 2.32(1)- 2.34(4) Å.     

Fluorescence Spectral Properties of Indocyanine Green on a Roughened Platinum Electrode: Metal-Enhanced Fluorescence

The interactions of fluorophores with noble metal particles can modify their emission spectral properties, a relatively new phenomenon in fluorescence. We subsequently examined indocyanine green (ICG), which is widely used in medical testing and imaging, in close proximity to an electrically roughened platinum electrode. The emission intensity and lifetimes were decreased about 2-fold on the roughened surface as compared to a smooth Pt surface, and the photostability about the same. Platinum does not appear promising for metal enhanced fluorescence, at least for long wavelength fluorophores.     

Multiplicity of the ground state of large alternant organic molecules with conjugated bonds

The multiplicity and the full spin of the ground state of large alternate molecules with conjugated bonds are considered. It is strictly shown that if the numbers of starred and unstarred atoms (say, carbon) differ from each other the full spin of the molecule is more than zero. Some possible planar and linear molecules having the full spin to be proportional to their sizes are presented. Particularly, they would be ferromagnets at infinite sizes.     

An Efficient and Convenient Synthesis of 2-Thio[1,2,4]triazolo[1,5-c]quinazoline and its Derivatives

4-Hydrazinoquinazoline with carbon disulfide underwent a recyclization reaction. The title compound 2-thio[1,2,4]triazolo[1,5-c]quinazoline was obtained after treatment of 4-hydrazinoquinazoline with potassium ethylxanthogenate via a facile in situ Dimroth-like rearrangement of the expected [4,3-c] system. Its structure was established by X-ray diffraction study and confirmed by an independent synthesis, starting from o-aminobenzonitrile.     

Highly diastereoselective reduction of ferrocene bis-imines with methyllithium and the formation of C2-symmetric Zr complexes

Alkylation of ferrocene bis-imines Fc[N=C(H)Ar]2 (Ar = Ph, p-Tol) with MeLi was found to proceed in a highly diastereoselective fashion producing the C2-symmetric ferrocene diamines Fc[NC(H)(Me)Ar]2-H2 with 90% diastereomeric excess. This process allowed for the synthesis of C2-symmetric zirconium complexes Fc[NC(Me)Ar]ZrBn2.     

Electrophoretic separation of amyloid beta peptides in plasma

In this prospective study, for the first time we have separated and quantified amyloid beta (Abeta) peptides in the plasma of patients with Alzheimer's disease (AD, n = 8) and age- and environment-matched healthy controls (n = 9) with urea-based Abeta-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/immunoblot. In addition to the Abeta peptides 1-37/38/39/40/42, which we recently identified as regular constituents of human cerebrospinal fluid (CSF), we have observed a novel electrophoretic band migrating slightly cathodically to Abeta1-42. Since a standard peptide with the amino acid sequence Abeta2-40 migrates in the same position, we hypothesize that this plasma-specific band may correspond to Abeta2-40. The concentration of Abeta peptides in the plasma has been approximately 100-fold lower compared to the CSF. Interestingly, the concentration of the two shortest peptides and the longest one of these considered here (i.e., Abeta1-37/38/42) have increased significantly when the samples have been frozen at -80 degrees C before immunoprecipitation, while the 'middle-length' peptides (i.e., Abeta1-39/40) have not been affected by this procedure. We have not observed significant differences of the Abeta peptides concentrations between AD and control subjects. Our method can be used to investigate the significance of plasma Abeta peptides in neurodegenerative disorders, and to monitor the efficiency of drugs with beta/gamma-secretase inhibitory potency.     

A novel approach to fused 1,2,4-triazines by intramolecular cyclization of 1,2-diaza-1,3-butadienes bearing allyl(propargyl)sulfanyl and cyclic tert-amino groups

3-Allyl- and 3-prop-1-ynylsulfanyl-2-arylazo-3-cycloalkylamino-acrylonitriles undergo cyclization under mild conditions to afford the novel heterocyclic systems 1,4,6,7,8,8a-hexahydropyrrolo[2,1-c][1,2,4]-triazine-4-thione, 1,4,6,7,9,9a-hexahydro-[1,4]oxazino[3,4-c][1,2,4]triazine and 1,6,7,8,9,9a-hexahydro-4H-pyrido[2,1-c][1,2,4]triazine via a number of consecutive pericyclic reactions.     

Investigation of Inhomogeneites in Epitaxial AlxGa1−xN Layers Grown on Sapphire

 Procedures for the preparation of bevels and the determination of their geometrical parameters have been developed. Using these procedures study of compositional and optical spatially resolved inhomogeneities of Al_xGa_1−xN layers grown on (0001) sapphire have been studied by EPMA and cathodolu-minescence. It has been found that the nonuniform distribution in depth of Al in epitaxial layers grown under constant conditions is connected with presence of stresses in the layer.     

Substrate-induced pairing in 2,3,6,7,10,11-hexakis-undecalkoxy-triphenylene self-assembled monolayers on Au111

We present an STM study of self-assembled monolayers of 2,3,6,7,10,11-undecalkoxy-substituted triphenylene (T11) at the n-tetradecane/Au(111) interface under ambient conditions. T11 molecules self-organize as paired rows with molecules lying flat on the surface in an antiparallel position. Three alkyl chains of each T11 molecule align along the 110 direction of the underlying Au(111) substrate. The association of T11 in molecular pairs appears to result from a substrate-induced mechanism governed by the strong anisotropic interaction between T11 alkyl chains and Au(111).