Synthesis of tellurobispyridines

All six isomers of tellurobispyridine, namely 2,2′-tellurobispyridine, 2,3′-tellurobispyridine, 2,4′-tellurobis-pyridine, 3,3′-tellurobispyridine, 3,4′-tellurobispyridine and 4,4′-tellurobispyridine have been synthesised.     

Photohydroxylation of 1,4-benzoquinone in aqueous solution revisited

In water, photolysis of 1,4-benzoquinone, Q gives rise to equal amounts of 2-hydroxy-1,4-benzoquinone HOQ and hydroquinone QH(2) which are formed with a quantum yield of Phi=0.42, independent of pH and Q concentration. By contrast, the rate of decay of the triplet (lambda(max)=282 and approximately 410 nm) which is the precursor of these products increases nonlinearly (k=(2-->3.8) x 10(6) s(-1)) with increasing Q concentration ((0.2-->10) mM). The free-radical yield detected by laser flash photolysis after the decay of the triplet also increases with increasing Q concentration but follows a different functional form. These observations are explained by a rapid equilibrium of a monomeric triplet Q* and an exciplex Q(2)* (K=5500+/-1000 M(-1)). While Q* adds water and subsequent enolizes into 1,2,4-trihydroxybenzene Ph(OH)(3), Q(2)* decays by electron transfer and water addition yielding benzosemiquinone (.)QH and (.)OH adduct radicals (.)QOH. The latter enolizes to the 2-hydroxy-1,4-semiquinone radical (.)Q(OH)H within the time scale of the triplet decay and is subsequently rapidly (microsecond time scale) oxidized by Q to HOQ with the concomitant formation of (.)QH. On the post-millisecond time scale, that is, when (.)QH has decayed, Ph(OH)(3) is oxidized by Q yielding HOQ and QH(2) as followed by laser flash photolysis with diode array detection. The rate of this pH- and Q concentration-dependent reaction was independently determined by stopped-flow. This shows that there are two pathways to photohydroxylation; a free-radical pathway at high and a non-radical one at low Q concentration. In agreement with this, the yield of Ph(OH)(3) is most pronounced at low Q concentration. In the presence of phosphate buffer, Q* reacts with H(2)PO(4) (-) giving rise to an adduct which is subsequently oxidized by Q to 2-phosphato-1,4-benzoquinone QP. The current view that (.)OH is an intermediate in the photohydroxylation of Q has been overturned. This view had been based on the observation of the (.)OH adduct of DMPO when Q is photolyzed in the presence of this spin trap. It is now shown that Q*/Q(2)* oxidizes DMPO (k approximately 1 x 10(8) M(-1) s(-1)) to its radical cation which subsequently reacts with water. Q*/Q(2)* react with alcohols by H abstraction (rates in units of M(-1) s(-1)): methanol (4.2 x 10(7)), ethanol (6.7 x 10(7)), 2-propanol (13 x 10(7)) and tertiary butyl alcohol ( approximately 0.2 x 10(7)). DMSO (2.7 x 10(9)) and O(2) ( approximately 2 x 10(9)) act as physical quenchers.     

Synthesis of 4,10-dihydro-4,10-dioxo-1H-[1]-benzopyrano[3,2-b]pyridine, 4,5-Dihydro-4,5-dioxo-1H-[1]-benzopyrano[2,3–6]pyridine and 1,5-Dihydro-1,5-dioxo-4H-[1]-benzopyrano[3,4-b]pyridine derivatives from aminobenzopyrones

3-Aminochromone and 3-aminocoumarin were condensed with diethyl ethoxymethylenemalonate and with dimethyl acetylenedicarboxylate to give intermediates, which were thermally cyclized to give 4,10-dihydro-4,10-dioxo-lH-[1]-benzopyrano[3,2-b]pyridinecarboxylates and 1,5-dihydro-1,5-dioxo-4H-[1]-benzopyrano-[3,4-b]pyridinecarboxylates. 2-Aminochromone was converted to 4,5-dihydro-4,5-dioxo-1H-[1]-benzopyrano-[2,3-b]pyridinecarboxylate via an intermediate condensation product with diethyl ethoxymethylenemalonate. These esters were hydrolyzed to the corresponding carboxylic acids (21, 30, 36, 50, and 60). Attempts to prepare 4,5-dihydro-4,5-dioxo-1H-[1]-benzopyrano[4,3-b]pyridinecarboxylates from 4-aminocoumarin were unsuccessful.     

Ein neues Alkali-Erdalkalimetall-Kupfer-Oxovanadat: Kba3Ca4Cu3V7O28

A new Alkaline-Alkaline-Earth-Copper-Oxovanadate: Kba₃Ca₄Cu₃V₇O₂₈ . Single crystals of Kba₃Ca₄Cu₃V₇O₂₈ were prepared by solid state reactions below the melting point of the reaction mixture. It crystallizes with hexagonal symmetry, space group C?P6₃mc, a=11.160, c=12.428 Å, Z=2. Kba₃Ca₄Cu₃V₇O₂₈ represents a new structure type with special coordination polyhedra around Ba²⁺, trigonal prisms and octahedra around Ca²⁺ and Cu²⁺ inside square pyramids. The crystal structure will be shown and discussed.     

Labelling studies for structure elucidation of a new hydroxymetabolite of tramadol

Abstract Tramadol, racemic 1-(3-methoxyphenyl)-2-(dimethylaminomethyl)cyclohexane-1-ol, is an effective analgesic drug. Metabolites of tramadol described so far originate from O- and N-demethylation and are excreted in urine directly or after conjugation. A further metabolite was found in human liver microsome incubations and in the urine of volunteers after ingestion of tramadol. To elucidate the structure of the new metabolite, seven deuterated isotopomers of tramadol have been synthesized and ingested by volunteers. The mass spectra of the metabolites derived showed (i) that it was a hydroxy metabolite, (ii) that the hydroxy group was not located on the aromatic ring, the side chain, or the positions 2 and 6 of the cyclohexane ring, (iii) that the hydroxy-group was introduced to one of the the positions 3, 4 or 5 of the cyclohexane ring. The hydroxy metabolite was formed preferentially from the (-)-enantiomer, (1S,2S)-tramadol.     

Two Counter-moving Light Beams

The cylindrically symmetric field of two beamsof light shining in opposite directions is studied. Wepresent four static or stationary exact solutions of thecorresponding field equations and compare their properties.     

Ein paar allgemeine metrische Sätze für algebraische Curven

Ohne ZusammenfassungEine vollständigere Entwickelung wird im norwegischen Archiv for Mathematik og Naturvidenskaber erscheinen.     

Synthesis of silica supported titania nanocomposite in controllable phase content and morphology

The silica supported titania nanocomposite thin films with controllable particle size and phase content were successfully prepared by a convenient post annealing approach involving in solid-solid interfacial reaction. The effects of growth conditions, such as the annealing temperature and silicon concentration on the particle size and phase content, were systematically studied by using Atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray spectroscopy (XPS). The results indicate that the silicon concentration is a dominant factor in the morphology, crystallization and phase transformation of these nanocomposites. A mechanism for the high temperature phase transformation is also proposed based on the migration of the oxygen vacancies.