This work presents a detailed investigation of the preparation of MoVTeNbO x catalysts by hydrothermal synthesis. Phase-pure synthesis of M1 has been achieved applying the metals in a molar ratio Mo/V/Te/Nb = 1/0.25/ 0.23/0.12. Raman, UV/Vis spectroscopy, and SEM/EDX analysis show that the elements are inhomogeneously distributed in the initial suspension that is formed after mixing the metal salts in an aqueous medium. Iso-and heteropoly anions of molybdenum, free telluric acid as well as supramolecular polyoxometalate clusters are observed in the solution, whereas all metals have been found in the precipitate. Complete rearrangement of molecular building blocks under hydrothermal conditions is essential for formation of phase-pure materials. Optimized synthesis conditions with respect to temperature and time result in the formation of a precursor consisting of nano-structured M1 characterized by an extended periodic organization in the [001] direction and a fairly homogeneous distribution of the elements. Residual ammonium containing supramolecular species in the precursor result in the formation of phase mixtures during the subsequent crystallization by heat treatment in inert gas. Phase-pure M1 exhibits a distinct degree of flexibility with respect to the chemical composition that becomes obvious by incorporating Nb not exclusively into pentagonal bi-pyramidal units, but also into octahedral coordinated positions as shown by EXAFS. Anisotropic growth of the needle-like M1 crystals has been observed during the final heat treatment performed at 873-923 K in inert atmosphere disclosing a potential method to control the catalytic properties of MoVTeNbO x catalysts.

A 20 K high resolution X-ray data set of L-Ala-L-Ala-L-Ala*1/2 H2O was measured using an ultra-low temperature laboratory setup, that combines area detection and a closed cycle helium cryostat. The charge density determination includes integration of atomic basins and topological analysis according to Bader's quantum theory of atoms in molecules. Two tripeptide units are found in the asymmetric unit, allowing the assessment of transferability of bond topological and atomic properties taking also into consideration previous data of oligopeptides. With respect to invariom modeling the limits of such transferability are investigated and the results of this study show the validity of the nearest/next-nearest neighbour approximation and support the use of database approaches for electron density modeling of macromolecules.

Bulk structural properties of single phase crystalline (Mo 0.91 V 0.09 ) 5 O 14 and (Mo 0.68 V 0.23 W 0.09 ) 5 O 14 materials were investigated using in situ X-ray diffraction and in situ X-ray absorption spectroscopy at three metal edges. Temperature programmed experiments in reducing (propene) and oxidizing (oxygen) atmosphere and isothermal redox experiments at 773 K revealed differences in the bulk properties of the two phases studied. A structure stabilizing effect of tungsten in (MoVW) 5 O 14 under oxidizing conditions was found. Moreover, tungsten centers in a (MoVW) dioxide material exert a structure-directing effect towards re-oxidation to a Mo 5 O 14 -type structure.

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The structural genesis of a Mo 0.68 V 0.23 W 0.09 oxide with Mo 5 O 14 -like structure has been examined.A precursor prepared by spray-drying of mixed aqueous metal salt solutions was calcined in air and subsequently treated in helium at different temperatures. X-ray diffraction, HRTEM, 51 V MAS NMR, ESR, UV/Vis DR spectroscopy and oxygen and hydrogen adsorption measurements have been applied to monitor the preparation procedure. It was found that a structure closely re-