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Oxide Clusters (oxide + cluster)
Selected AbstractsStructure of Disodium Dimolybdate Synthesized Using Thermodynamically Stable Molybdenum (VI) Oxide Clusters as PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Dragana J. Jovanovi The structure of disodium dimolybdate (Na2Mo2O7) synthesized by a low-temperature method in the process of ultrasonic spray pyrolysis using acidified aqueous solutions of thermodynamically stable molybdenum (VI) oxide clusters as a precursor was refined down to an R -factor of 7%. The refinement of the diffraction data showed that Na2Mo2O7 powder synthesized at 300°C belongs to the base-centered orthorhombic type of structure with a space group of Cmca (no. 64). It was found that the basic units of the octahedral MoO6 precursor complexes exist in the structure of Na2Mo2O7. Tetrahedral MoO4 building units that coexist together with octahedral units in the structure of Na2Mo2O7 are most likely developed by the termination of weak octahedral bonds and by the placement of the molybdenum atom in the center of the tetrahedra. [source] Generation of Oxygen Radical Centers in Binary Neutral Metal Oxide Clusters for Catalytic Oxidation ReactionsANGEWANDTE CHEMIE, Issue 13 2010Melanie Nößler No abstract is available for this article. [source] Generation of Oxygen Radical Centers in Binary Neutral Metal Oxide Clusters for Catalytic Oxidation Reactions,ANGEWANDTE CHEMIE, Issue 2 2010Melanie Nößler Ein Elektron mehr oder weniger: Um Radikalzentren in neutralen binären Zirconiumoxid-Clustern zu generieren, wird in kationischen oder anionischen Clustern mit einem Radikalzentrum ein Zr-Atom gegen ein Metallatom mit einem Elektron mehr (Nb) bzw. weniger (Sc) ausgetauscht. Diese isoelektronischen Systeme vermitteln ähnliche Oxidationen und können einen vollständigen Katalysezyklus durchlaufen (siehe Bild; Zr,gelb, Sc,grau, O,rot, C,grün, H,türkis, N,blau). [source] ChemInform Abstract: Structural Evolution, Sequential Oxidation, and Chemical Bonding in Tritantalum Oxide Clusters: Ta3On - and Ta3On (n = 1,8).CHEMINFORM, Issue 47 2009Hua-Jin Zai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Identification of Conical Structures in Small Aluminum Oxide Clusters: Infrared Spectroscopy of (Al2O3)1-4(AlO)+.CHEMINFORM, Issue 6 2009Gabriele Santambrogio Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Boronyls as Key Structural Units in Boron Oxide Clusters: B(BO) - 2 and B(BO) - 3CHEMINFORM, Issue 41 2007Hua-Jin Zhai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Structure and Stability of Small Boron and Boron Oxide ClustersCHEMINFORM, Issue 38 2007Michael L. Drummond Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Complexation of the Vulcanization Accelerator Tetramethylthiuram Disulfide and Related Molecules with Zinc Compounds Including Zinc Oxide Clusters (Zn4O4)CHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2008Ralf Steudel Prof. Abstract Zinc chemicals are used as activators in the vulcanization of organic polymers with sulfur to produce elastic rubbers. In this work, the reactions of Zn2+, ZnMe2, Zn(OMe)2, Zn(OOCMe)2, and the heterocubane cluster Zn4O4 with the vulcanization accelerator tetramethylthiuram disulfide (TMTD) and with the related radicals and anions Me2NCS2., Me2NCS3., Me2NCS2,, and Me2NCS3, have been studied by quantum chemical methods at the MP2/6-31+G(2df,p)//B3LYP/6-31+G* level of theory. More than 35 zinc complexes have been structurally characterized and the energies of formation from their components calculated for the first time. The binding energy of TMTD as a bidendate ligand increases in the order ZnMe2 Interaction of Zinc Oxide Clusters with Molecules Related to the Sulfur Vulcanization of Polyolefins ("Rubber")CHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2006Ralf Steudel Prof. Dr. Abstract The vulcanization of rubber by sulfur is a large-scale industrial process that is only poorly understood, especially the role of zinc oxide, which is added as an activator. We used the highly symmetrical cluster Zn4O4 (Td) as a model species to study the thermodynamics of the initial interaction of various vulcanization-related molecules with ZnO by DFT methods, mostly at the B3LYP/6-31+G* level. The interaction energy of Lewis bases with Zn4O4 increases in the following order: CO Enhanced Adsorption of Ammonia on Metal-Organic Framework/Graphite Oxide Composites: Analysis of Surface InteractionsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Camille Petit Abstract Composites of the metal-organic framework (MOF), MOF-5, and graphite oxide (GO) with different ratios of the two components are prepared and tested in ammonia removal under dry conditions. The parent and composite materials are characterized before and after exposure to ammonia by sorption of N2, X-ray diffraction, thermal analyses, and FT-IR spectroscopy. The results show a synergetic effect resulting in an increase in the ammonia uptake compared to the parent materials. It is linked to enhanced dispersive forces in the pore space of the composites. Additionally, ammonia interacts with zinc oxide tetrahedra via hydrogen bonding and is intercalated between the layers of GO. Retention of a large quantity of ammonia eventually leads to a collapse of the MOF-5 structure in the composites. The effect resembles that observed when MOF-5 is exposed to water. Taking into account the similarity of ammonia and water molecules, it is hypothesized that ammonia causes a destruction of the MOF-5 and composite structure as a result of its hydrogen bonding with the zinc oxide clusters. [source] Structure of Disodium Dimolybdate Synthesized Using Thermodynamically Stable Molybdenum (VI) Oxide Clusters as PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Dragana J. Jovanovi The structure of disodium dimolybdate (Na2Mo2O7) synthesized by a low-temperature method in the process of ultrasonic spray pyrolysis using acidified aqueous solutions of thermodynamically stable molybdenum (VI) oxide clusters as a precursor was refined down to an R -factor of 7%. The refinement of the diffraction data showed that Na2Mo2O7 powder synthesized at 300°C belongs to the base-centered orthorhombic type of structure with a space group of Cmca (no. 64). It was found that the basic units of the octahedral MoO6 precursor complexes exist in the structure of Na2Mo2O7. Tetrahedral MoO4 building units that coexist together with octahedral units in the structure of Na2Mo2O7 are most likely developed by the termination of weak octahedral bonds and by the placement of the molybdenum atom in the center of the tetrahedra. [source] A three-dimensional hybrid framework based on novel [Co4Mo4] bimetallic oxide clusters with 3,5-bis(3-pyridyl)-1,2,4-triazole ligandsACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009Quan-Guo Zhai In the title organic,inorganic hybrid complex, poly[[[,-3,5-bis(3-pyridyl)-1,2,4-triazole]tri-,3 -oxido-tetra-,2 -oxido-oxidodicobalt(II)dimolybdenum(VI)] monohydrate], {[Co2Mo2O8(C12H9N5)]·H2O}n, the asymmetric unit is composed of two CoII centers, two [MoVIO4] tetrahedral units, one neutral 3,5-bis(3-pyridyl)-1,2,4-triazole (BPT) ligand and one solvent water molecule. The cobalt centers both exhibit octahedral [CoO5N] coordination environments. Four CoII and four MoVI centers are linked by ,2 -oxide and/or ,3 -oxide bridges to give an unprecedented bimetallic octanuclear [Co4Mo4O22N4] cluster, which can be regarded as the first example of a metal-substituted octamolybdate and exhibits a structure different from those of the eight octamolybdate isomers reported to date. The bimetallic oxide clusters are linked to each other through corner-sharing to give two-dimensional inorganic layers, which are further bridged by trans -BPT ligands to generate a three-dimensional organic,inorganic hybrid architecture with six-connected distorted ,-Po topology. [source] Hydrogen-Atom Abstraction from Methane by Stoichiometric Vanadium,Silicon Heteronuclear Oxide Cluster CationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 37 2010Dr. Xun-Lei Ding Abstract Vanadium,silicon heteronuclear oxide cluster cations were prepared by laser ablation of a V/Si mixed sample in an O2 background. Reactions of the heteronuclear oxide cations with methane in a fast-flow reactor were studied with a time-of-flight (TOF) mass spectrometer to detect the cluster distribution before and after the reactions. Hydrogen abstraction reactions were identified over stoichiometric cluster cations [(V2O5)n(SiO2)m]+ (n=1, m=1,4; n=2, m=1), and the estimated first-order rate constants for the reactions were close to that of the homonuclear oxide cluster V4O10+ with methane. Density functional calculations were performed to study the structural, bonding, electronic, and reactivity properties of these stoichiometric oxide clusters. Terminal-oxygen-centered radicals (Ot.) were found in all of the stable isomers. These Ot. radicals are active sites of the clusters in reaction with CH4. The Ot. radicals in [V2O5(SiO2)1,4]+ clusters are bonded with Si rather than V atoms. All the hydrogen abstraction reactions are favorable both thermodynamically and kinetically. This work reveals the unique properties of metal/nonmetal heteronuclear oxide clusters, and may provide new insights into CH4 activation on silica-supported vanadium oxide catalysts. [source]
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