65 research outputs found
Amino-Functionalized Layered Crystalline Zirconium Phosphonates: Synthesis, Crystal Structure, and Spectroscopic Characterization
No full textTwo new layered zirconium phosphonates functionalized with amino groups were synthesized starting from aminomethylphosphonic acid in the presence of different mineralizers, and their structures were solved from powder X-ray diffraction data. Their topologies are unprecedented in zirconium phosphonate chemistry: The first, of formula ZrH[F3(O3PCH2NH2)], prepared in the presence of hydrofluoric acid, features uncommon ZrO2F4 units and a remarkable thermal stability; the second, of formula Zr2H2[(C2O4)3(O3PCH2NH2)2]·2H2O, prepared in the presence of oxalic acid, is based on ZrO7 units with oxalate anions coordinated to the metal atom, which were never observed before in any zirconium phosphonate. In addition, the structure of another compound based on (2-Aminoethyl)phosphonic acid is reported, which was the object of a previously published study. This compound has layered α-Type structure with âNH3+ groups located in the interlayer space. All of the reported compounds were further characterized by means of vibrational spectroscopy, which provided important information on fine structural details that cannot be deduced from the powder X-ray diffraction data
L’assistenza domiciliare integrata nella ASL 1 di Massa e Carrara. Nota 1- Il progetto tandem: la formazione socio-sanitaria delle associazioni di volontariato della Lunigiana
No full textSynthesis and Crystal Structure from X-ray Powder Diffraction Data of Two Zirconium Diphosphonates Containing Piperazine Groups
No full textTwo new zirconium aminophosphonates have been obtained by reaction of Zr(IV) with piperazine-N,N′-bis(methylenephosphonate) building blocks. Their crystal structure has been determined ab initio from X-ray powder diffraction data collected with a conventional diffractometer. Although prepared in similar conditions, their composition and crystal structure is markedly different. Compound 1, of formula Zr2H4[(O3PCH2)2N2C4H8]3·9H2O, has a three-dimensional structure (trigonal, space group R3̅̅ (No. 148), a = 19.9400(9) Å, c = 9.5728(6) Å, Z = 3), made of infinite inorganic chains of ZrO6 octahedra and PO3C tetrahedra, running along the c-axis direction, connected by piperazine groups in the ab plane, and generating channels running along the c axis. Compound 2, of formula ZrF2(O3PCH2)2(NH)2C4H8, has a pillared-layered structure (monoclinic, space group P21/c (No. 14), a = 8.7148(2) Å, b = 8.1731(1) Å, c = 9.0134(2) Å, β = 105.175(1)° Z = 2) in which inorganic layers, made of the connectivity of Zr octahedra and P tetrahedra, are covalently connected by piperazine groups, that act as pillars. The effect of the various synthesis parameters is discussed. A probable structure directing parameter seems to be the pH value of the starting precipitation solution, that can influence the protonation of N atoms of piperazine moiety
Crystal engineering on layered zirconium phosphonates. Crystal structure (from X-ray power data) and non-covalent interactions on the layered zirconium compound of 4-[bis(phosphonomethyl)-amino]butanoic acid
No full textA new layered zirconium diphosphonate fluoride, ZrHF(O3PCH2)2NHC3H6CO2, has been prepared by the reaction of zirconyl chloride with 4-[bis(phosphonomethyl)amino]butanoic acid in the presence of HF. Its structure has been determined "ab initio" by X-ray powder data. It crystallizes in the monoclinic space group P21/c (No. 14), with a = 12.9640(3) Å, b = 8.9900(4) Å, c = 10.7924(4) Å, β = 101.854(4)°, and Z = 4. Both of the phosphonic groups of each diphosphonate building block are bonded to zirconium atoms on the same side of the layers. Only one organic residue is associated with two phosphonate tetrahedra. The packing of layers creates an interdigitated arrangement of organic groups in the interlayer region. Two strong non-covalent interactions are present in the structure. One of them involves neighbouring P-OH and amino groups, while the other interaction engages terminal carboxylic groups and fluorine atoms belonging to adjacent layers. Thermal treatment at 240 °C causes the loss of one mole of HF per mole of zirconium, with the formation of a stable compound in which carboxylate groups probably coordinate to the zirconium atoms belonging to adjacent layers. Preliminary experiments of intercalation with ammonia and short alkylamines are also reported
I materiali sostitutivi dell’Amianto: La de-vetrificazione di fibre ceramiche refrattarie e lane minerali in condizioni di lavori ad alta temperatura
No full textVibrational study of some layered structures based on titanium and zirconium phosphates
No full textA Raman and infrared study was carried out on layered zirconium and titanium acid phosphates of R- and γ-type, R-M[O3POH]2‚H2O and γ-M[PO4][O2P(OH)2]‚2H2O, respectively. The spectra were initially approached by means of the classical correlation method in the solid state, which accounts for the complexity of the infrared spectra of both species. However, the number of bands and their relative intensity in the Raman spectra suggest a quite total absence of quadrupolar coupling between the vibrating units. So, if interunit coupling is neglected, a molecular approach considering the vibrations of isolated tetrahedral [PO4] and octahedral [MO6] building blocks can allow an affordable spectroscopic description of the title compounds. Interesting insights on the relationships between spectral properties and structure can be drawn by comparison with the spectra of alkali phosphates and of MO6 oxoanions. A significant high-energy shift of the ν(P−O) modes is observed in the layered phosphates with respect to the corresponding salts, which parallels the low-energy shift of the ν(M−O) modes. Surprisingly, an increase of the M−OP interaction can reinforce the P−O bond. A simple theoretical model, based on the interaction between the [PO4] unit and four Li+ in similar geometrical arrangement found in the structures of the layered phosphates, offers a reasonable explanation of this phenomenon
Characterisation of alumino-silicate ceramic fibres devetrification during high temperature working conditions.
No full textRole of the solvent in the US-assisted preparation of TiO2 for the photocatalytic degradation of sulfamethoxazole in water
No full textThis work presents a study concerning the role of the solvent in the US-assisted preparation of TiO2 for the photocatalytic degradation of sulfamethoxazole in water. Different solvente were tested in the catalyst preparation and the obtained results in a batch reactor discussed
A mechanicistic hypothesis on the decomposition of the lamba-type layered Zr(IV)phosphates based on thermogravimetrical, spectroscopical and hyphenated techniques
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