High-Yielding Green Hydrothermal Synthesis of Ruthenium Nanoparticles and Their Characterization.

Using hydrothermal techniques, a novel synthetic approach to prepare ruthenium nanoparticles has been developed. At 180 degrees C and under autogenous pressure, starting from an aqueous solution of ruthenium trichloride, the method yielded nanoparticles whose form and size both depended on the reducing agent: sodium citrate (hexagonal shaped nanocrystals, 1-20 nm), ascorbic acid (spherical nanoparticles, 3-5 nm) and succinic acid (spherical nanoparticles, 1-120 nm). Depending on the reaction variables, the nature and concentration of partially reduced species determines the characteristics of the final products. HRTEM image analysis along with the simulation techniques were stabilized preferential growth of nanoparticles on specific directions. Ruthenium samples have been investigated by Temperature-Programmed Reduction (TPR) showing that the reduction temperature of nanoparticles is correlated to their nanocrystalline size.

Dimensionality changes in the solid phase at room temperature: 2D → 1D → 3D evolution induced by ammonia sorption-desorption on zinc phosphates.

Two-dimensional zinc phosphate NH4Zn2(PO4)(HPO4) (), via ammonia vapor interaction at room temperature, transforms to a one-dimensional novel compound NH4Zn(NH3)PO4 (). By ammonia desorption (in air at room temperature) transforms to NH4ZnPO4 () with a well-known ABW-zeolitic topology. The crystal structure of was solved ab initio using synchrotron powder X-ray diffraction data (monoclinic, P21/a, a = 16.5227(2) Å, b = 6.21780(8) Å, c = 5.24317(6) Å, ß = 91.000(2)°, Z = 4). The structures of three compounds include extra-framework ammonium cations to the 4-fold coordinated zinc (ZnO4 tetrahedra for and , and ZnO3N tetrahedra for ) and phosphorus (PO4 tetrahedra) with bi-, mono- or three-dimensional linkages, respectively for , or . To our knowledge, the process described here constitutes the first example of dimensionality change in the solid phase promoted by a solid-gas interaction at room temperature in metal phosphates.

Series of 2D heterometallic coordination polymers based on ruthenium(III) oxalate building units: synthesis, structure, and catalytic and magnetic properties.

A series of 2D ruthenium-based coordination polymers with hcb-hexagonal topology, {[K(18-crown-6)]3[M(II)3(H2O)4{Ru(ox)3}3]}n (M(II) = Mn (1), Fe (2), Co (3), Cu (4), Zn (5)), has been synthesized through self-assembly reaction. All compounds are isostructural frameworks that crystallize in the monoclinic space group C2/c. The crystal packing consists of a 2D honeycomb-like anionic mixed-metal framework intercalated by [K(18-crown-6)](+) cationic template. Dehydration processes take place in the range 40-200 °C exhibiting two phase transitions. However, the spontaneous rehydration occurs at room temperature. Both hydrated and dehydrated compounds were tested as Lewis acids heterogeneous catalysts in the acetalyzation of benzaldehyde achieving high yields with the possibility to be recovered and reused. All the investigated materials do not show any long-range magnetic ordering down to 2 K. However, the Fe-based compound 2 presents a magnetic irreversibility in the ZFC-FC magnetization data below 5 K, which suggest a spin-glass-like behavior, characterized also by short-range ferromagnetic correlations. The coercive field increases as the temperature is lowered below 5 K, reaching a value of 1 kOe at 2 K. Alternating current measurements obtained at different frequencies confirm the freezing process that shows weak frequency dependence, being characteristic of a system exhibiting competing magnetic interactions.

On the crystal structure and thermal decomposition of ammonium-iron(III) bis(hydrogenphosphate).

NH(4)Fe(HPO(4))(2) and its deuterated form have been synthesized as monophasic polycrystalline materials. Their crystal structures, including hydrogen positions, were determined by Rietveld refinement and Fourier synthesis using constant-wavelength neutron powder diffraction data. In addition, the thermal decomposition of NH(4)Fe(HPO(4))(2) was found to give mixtures of Fe(4)(P(2)O(7))(3) and Fe(PO(3))(3)via NH(4)FeP(2)O(7) formation, the crystal structure of which has also been refined from X-ray powder diffraction data.

Revisiting the thermal decomposition of layered gamma-titanium phosphate and structural elucidation of its intermediate phases.

The thermal transformations of gamma-titanium phosphate, Ti(PO(4))(H(2)PO(4)) x 2 H(2)O, have been studied by thermal analyses (thermogravimetry (TG) and differential thermal analysis (DTA)) and variable-temperature (31)P magic-angle spinning (MAS)/CPMAS and 2D (31)P-(31)P spin-exchange NMR. The structure of this material has been refined from synchrotron powder X-ray diffraction data (monoclinic, P2(1), a = 5.1811(2) A, b = 6.3479(2) A, c = 23.725(2) A, beta = 102.57(1) degrees). Vyazovkin's model-free kinetic algorithms have been applied to determine the apparent activation energy to both dehydration and dehydroxylation of gamma-titanium phosphate. In these processes, several overlapped steps have been detected. Structural models for Ti(PO(4))(H(2)PO(4)) x H(2)O and Ti(PO(4))(H(2)P(2)O(7))(0.5) intermediate layered phases have been proposed.

Synthesis and crystal structure of NZP-type thorium-zirconium phosphate.

Microcrystals of Th(1/4)Zr(2)(PO(4))(3) were synthesized by thermal treatment (900 degrees C) of the material obtained using sol-gel technology (including organic complex formation and etherification). Their structure [hexagonal, P3c, a = b = 8.7311(4) A, c = 23.309(2) A] includes the three-dimensional [Zr(2)(PO(4))(3)](-) NASICON-type network and extraframework 6-fold-coordinated thorium(IV) cations.