Showing papers on "Inorganic compound published in 1985"

Organic fluorescent dyes trapped in silica and silica-titania thin films by the sol-gel method. Photophysical, film and cage properties

Abstract: The sol-gel process is utilized to solve the notorious problem of incorporating an organic dye in an inorganic oxide thin film. Fluorescent thin films are prepared by this low temperature process with the aid of a surface active agent, with good homogeneity and reproducability. A variety of organic fluorescent molecules are embeded either in silica or in silica-titania films. The dye molecules are not leached out by water. Absorption and emission spectra, enhanced photostability, longer lifetimes and energy transfers between the trapped dye molecules are described and discussed in terms of the effects of molecule matrix-isolation on these properties. Potential uses of the special thin films are numerous, e.g., as laser or solar light guides.

Vacuum heat-treatment for activation of glassy carbon electrodes

Abstract: Le traitement thermique d'une electrode de carbone vitreux, a 725°C sous vide pousse (<2.10 −6 Torr) permet d'obtenir une electrode active vis-a-vis de l'oxydoreduction du ferro-ferricyanure et pour l'oxydation d'acide ascorbique

Dimerization and stacking in transition-metal bisdithiolenes and tetrathiolates

Abstract: The structural, chemical, and electrical properties of a number of transition-metal bisdithiolenes and tetrathiolenes are studied through qualitative MO and band structure calculations. The formation of metal-metalor metal-sulfur-bonded dimers of bisdithiolenes is found to depend on a delicate balance of several factors: sulfur lone-pair repulsion between the monomers, size and occupation of the transition metal’s d orbitals, and steric repulsions between substituents in the dithiolene ligands. Regular stacks of transition-metal bisdithiolenes are predicted to be unstable toward Peierls distortions for integral oxidation states. The sulfur lone-pair repulsions are responsible for the slippage of the stacks as well as for the sliding of neighboring stacks, giving rise to triclinic crystals. The resulting stacking pattern can produce mixing of the u and K sulfur lone pairs, hence two dimensionality in the electrical conductivity. An isolobal analogy allows one formally to replace carbon-carbon double bonds by a metal atom, providing the orbital foundation of a structural and electrical analogy between transition-metal bisdithiolenes and tetrathiofulvalene derivatives. The coordinative ability of the simplest tetrathiolene, ethylenetetrathiolate (ett), is analyzed. Of the two coordination modes available for this ligand, the dithiolene-like mode is found to be more stable than the dithiocarbamate-like one both for discrete and polymeric compounds. But the dithiocarbamate coordination mode should be accessible. A likely structural candidate for the polymers M(ett) is a planar ribbon; a band composed of the metal d,, and a ligand K orbital shows dispersion due to through-bond coupling and could account for one-dimensional electrical conductivity. Alternative oneand two-dimensional structures for the as yet unknown compounds M2(ett) and M3(ett) are also studied. While much has been learned about transition-metal dithiolenes,’ an interesting remaining intellectual challenge is the attainment of that degree of the understanding of their structural and electronic properties that could give rise to the design and synthesis of low-dimensional materials with metallic or semiconducting properties. The mode of association of metal dithiolenes is the subject of this work. The metal bisdithiolenes 1 (R = H, CN, CF3, and Ph; n = 0, 1, and 2) are planar compounds which may appear in the crystal state as isolated units,2 as dimers with metal-sulfur bond^,*^,^*^ n2a, metal-metal bonded dimer^,^ 2b, or as partially oxidized stacks featuring metal-metal bonds and different degrees of pairing distortion.6 Much less is known about the analogous compounds

On the nature of oxides on InP surfaces

Abstract: The chemical composition of surface oxides grown on InP is investigated using x‐ray photoelectron spectroscopy. Native oxides prepared by various chemical treatments, anodic oxides, and thermal oxides are examined. Core level energies and intensities and valence band spectra are compared with data for standard compounds. In a first step we show that, depending on the preparation procedure, oxides can be classified into three groups which have properties similar to crystalline In(OH)3, InPO4, and In(PO3)3, respectively. The large variations observed in atomic compositions and the shape of valence band spectra suggest that the oxides could be amorphous nonstoichiometric phases. A description based on a mixture of well defined compounds (e.g., In2O3+P2O5 or In2O3+InPO4) seems to be inadequate. Chemical and anodic phosphorus‐rich oxides are identified as Inx(PO3)y polyphosphates.

Further insight into magnetostructural correlations in binuclear copper(II) species related to methemocyanin: x-ray crystal structure of 1,2-.mu.-nitrito complex

Abstract: Determination de la structure de [Cu 2 (L-Et)(NO 2 )] [ClO 4 ] avec HL-Et=N,N,N'N'-tetrakis-([ethyl-1 benzimidazolyl]-2) hydroxy-2 diamino-1,3 propane

Reductive homologation of carbon monoxide to a ketenecarboxylate by a low-valent organolanthanide complex: synthesis and x-ray crystal structure of [(C5Me5)4Sm2(O2CCCO)(THF)]2

Abstract: Die Reaktion von CO mit dem stark reduzierend wirkenden Sm(II)-Komplex (I) liefert das Produkt (II), dem seine Struktur anhand seiner rontgenographischen Strukturbestimmung (RG: PT; Z = l) zuerkannt wird.

A further example of a dinuclear copper(II) complex involving monoatomic acetate bridges. Synthesis, crystal structure, and spectroscopic and magnetic properties of bis(.mu.-acetato)bis(7-amino-4-methyl-5-aza-3-hepten-2-onato(1-))dicopper(II)

Abstract: (C 19 H 16 N 2 O 3 Cu) 2 cristallise dans P1 avec Z=1; affinement jusqu'a R=0,025. Spectre RPE. Susceptibilite magnetique

Monoclinic Crystal Structures of ZrO2 and HfO2 Refined from X-ray Powder Diffraction Data

Abstract: The crystal structures of ZrO2 and HfO2 (P21/c) were refined in detail from X-ray powder diffraction data. The precision obtained for the atom positions for both compounds is comparable to that of previous single-crystal work.

Electron density distribution analysis for nitromethane, nitromethide, and nitramide

Abstract: Calculs a l'aide d'une variante simple de l'algorithme de Streitweiser pour evaluer la densite electronique projetee sur un plan unique

Molecular structure of a catenand and its copper(I) catenate: complete rearrangement of the interlocked macrocyclic ligands by complexation

Abstract: The first crystal structures of a catenane and of a metalio-catenate are reported; upon complexation with CuI, there is a dramatic change in molecular shape.