INORGANIC ARCHITECTURE BASED ON A {[Ca(H2O)]6[P4W6O34]2}12- BUILDING BLOCK: COUNTERCATION EFFECT ON THE LATTICE SYMMETRY (300,00 руб.)

The change in the lattice as a function of the countercation and its coordination, specially calcium, is investigated. <...> Full characterization is made by single crystal X-ray diffraction and also UV-visible spectroscopy, FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). <...> A literature survey of POMs and their derivatives shows that only few calcium-containing POMs have been synthesized and their structure determined by X-ray diffraction. <...> All chemicals used for synthesis were of reagent grade and used without further purification. 1: Sodium tungstate dihydrate Na2WO42H2O (2.50 g, 7.5 mmol), hydrated sodium hydrogen phosphate Na2HPO412H2O (1.34 g, 3.7 mmol), and CaCl2 (0.415 g, 3.7 mmol) were dissolved in 20 ml of water in 50-ml RBF equipped with a magnetic stirring bar. <...> The product had trigonal morphology and was slightly soluble in water. 2: A similar procedure as in 1 was followed except that the pH was adjusted to 6.0 and no NH4Cl was added. <...> The crystals were colorless with triclinic morphology. 3: A solid powdered precursor K24[P4W52O178]47H2O was synthesized according to the literature procedure [ 27 ] and confirmed by FT-IR spectroscopy. <...> FT-IR spectra were recorded with a Nicolet Impact 400 Fourier transform infrared spectrophotometer (Madison, WI) in the range 400—4000 cm–1 using KBr pellets. <...> Thermogravimetric analyses were performed by Kanti Labs Ltd. in Missisunga, Canada. <...> For scanning electron microscopy (SEM), dehydrated crystals were molded and attached to 10 mm metal mounts using carbon tape, and then sputter coated with platinum under vacuum in an argon atmosphere. <...> Single crystal X-ray diffraction data were collected using an Xcalibur/Oxford diffractometer equipped with a Eos CCD detector. y(MoKh) = 0.71073 Е at 20 C. Data reduction was performed using the CrysAlisPro software package [ 28 ]; the crystal structure solution and refinements were carried out using Olex [ 29 ] and SHELXTL [ 30 ]. <...> The three structures reported in this paper differ in their unit cell parameters and also differ from the well-known Wang et al. structure. <...> It crystallizes <...>