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1.
The structural roles of the two types of lattice water in K3N(SO3)3.2H2O have been determined from the geometries of their immediate environments. Through hydrogen bonds of different lengths (and hence strengths), H2O(1) links adjacent N(SO3)33?ions belonging to the same unit cell and lying on the same crystallographic mirror plane as O(1).H2O(2) links identical N(SO3)33?ions contained in unit cells adjacent in the b direction, by very weak, equivalent hydrogen bonds. The hydrogen atoms of H2O(1) are assigned to Cs sites in the unit cell and those of H2O(2) are assigned to C1 sites. The proposed site occupancies are verified by infrared spectroscopy using the “isotopic dilution” technique.  相似文献   

2.
Magnetic anisotropies of a trigonal crystal of NaMgCr(C2O4)3·9H2O measured between 300 and 77 K are approximately inversely proportional to the square of the absolute temperature; moreover K6 > K. although g. > g6 from EPR measurements. The sign of D, the zero-field splitting, which was not determined from EPR, is shown to be negative.  相似文献   

3.
The compound K2MoO3(C2O4) · H2O shows a deep-red lummescence at low temperatures. This emission is due to the molybdate octahedron.  相似文献   

4.
Neutron inelastic scattering spectra of NaHC2O4, KHC2O4 crystals at 80 K have been recorded in the 2200-200 cm?1 range. The lithium acid salt was also studied at different temperatures. NIS spectra are compared to the corresponding infrared and Raman spectra and an assignment is proposed. Two strong bands near 1500 and 1100 cm?1 are assigned to δ(OH) and γ(OH) vibrations, respectively, while five weak bands below 900 cm?1 are associated with skeletal modes, mainly bending vibrations. The OH stretching vibration is not observed and is believed to be hidden by other bands; the peak intensity must be low because of its band width which is of the order of a few hundreds wavenumbers.  相似文献   

5.
The mixed lead nitrate oxalate, Pb2(NO3)2(C2O4).2H2O, has been obtained in a polycrystalline form in the course of a study on precursors of nanocrystalline PZT-type oxides. Its crystal structure has been solved from powder diffraction data collected using a monochromatic radiation from a conventional X-ray source. The symmetry is monoclinic, space group P21/c (No. 14), the cell dimensions are a=10.623(2) Å, b=7.9559(9) Å, c=6.1932(5) Å, β=104.49(1)° and Z=4. The structure consists of a stacking of complex double sheets parallel to (1 0 0), forming layers held together by hydrogen bonds. The sheets result from the condensation of PbO10 polyhedra, in which the oxalate and nitrate groups, as well as water molecules, play a major role. The structure is discussed in terms of Pb---O distances, polyhedra shape and lead coordination, with emphasis on the dimensional polymerisation role of water molecules. The thermal behaviour of this layered compound is carefully described from temperature-dependent powder diffraction and thermogravimetric measurements. The enthalpy, ΔrH=232(3) kJ mol−1, and entropy, ΔrS=532(8) J K−1 mol−1, of the dehydration reaction have been determined. The high value of ΔrH demonstrates that the water molecules are strongly bonded in the structure. The complex decomposition proceeds through the crystallisation and decomposition of Pb(NO3)2(C2O4) into Pb(NO3)2 and PbC2O4, and, finally, various lead oxides.  相似文献   

6.
NaPd3O4, Na2PdO3 and K3Pd2O4 have been prepared by solid-state reaction of Na2O2 or KO2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd3O4 (space group Pmn, a=5.64979(6) Å, Z=2) is isostructural to NaPt3O4. It consists of NaO8 cubes and PdO4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO4 squares are perpendicular to each other. Na2PdO3 (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li2RuO3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na+ and Pd4+ cations alternate with Na3 layers along the c-axis. Na2PdO3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K3Pd2O4, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO4 units connected via common edges to form parallel staggered PdO2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K3Pd2O4 reveal a Curie-Weiss behavior in the temperature range above 80 K.  相似文献   

7.
Single crystals of two cerium complexes, with mixed-ligands oxalate and glycolate, have been prepared in a closed system, at 200 °C for one month: [Ce2(H2O)3](C2O4)2.5(H3C2O3) 1 and Ce2(C2O4)(H3C2O3)42. 1 crystallizes in the orthorhombic system, space group Pbca, with , , and while 2 crystallizes in the tetragonal system, space group P42/nbc, with , . For both complexes, the three-dimensional framework structure is built up by the linkages of the cerium and all the oxygen atoms of oxalate and glycolate ligands. For 2, its structure presents a nice case of two 3D identical sub-lattices, with 2-fold interpenetration. The only link between these two sub-lattices is assumed by strong hydrogen bonds between the hydroxyl function of the glycolate and the oxygen atoms of the oxalate. The schematized framework of 2, including only the cerium atoms, can be compared to that of cooperite (PtS).For 1, the two independent cerium have 9- or 10-fold coordination, forming a distorted monocapped or bicapped square antiprism polyhedron while for 2, the two independent cerium present 8-fold coordination, forming an almost regular dodecahedron. A quite relevant feature of 2 is the complete absence of water. 2 has been extended to other lanthanides (Ln=Ce…Lu, yttrium included) leading to a family, which has been characterized by infra-red and thermal analysis.  相似文献   

8.
Single crystal susceptibilities of Er(C2O4) (C2O4H)·3H2O are reported over the 1.5–20 K interval, and EPR spectra at 4.2 K of Y (C2O4) (C2O4H·3H2O doped with Er3+ are also reported. The susceptibilities follow the CurieWeiss law, with g| = 12.97 ± 0.05, g = 2.98 ± 0.05, θ| = ?0.25 ± 0.05 K, and θ = ?0.12 ± 0.05 K.  相似文献   

9.
The crystal structure of SnC2O4 has been determined by X-ray single-crystal techniques and refined to R = 0,018 for 1139 reflections. The cell is monoclinic, space group C2c with Z = 4 formula units, the parameters being a = 10,375(3)Å. b = 5,504(2)Å, c = 8,234(3)Å, β = 125,11(2)°. The oxalato groups, located on symmetry centers, are chelated to two Sn atoms through one oxygen on each carbon atom, giving rise to an infinite string (SnC2O4)n. The Sn(II) atom is one-side bonded to four oxygen atoms with two SnO bonds of 2,232(2) Å and two of 2,393(2) Å. The tin atom is in a distorted trigonal bipyramid SnO4E, the lone pair E occupying one of the apices of the equatorial trigonal base of the polyhedron. Crystal structure comparison with disodium bisoxalatostannate(II), Na2Sn(C2O4)2, permits one to deduce SnC2O4 by crystallographic shear operation 18[342](001) of c2 periodicity. Na2Sn(C2O4)2 can be described as an intergrowth of SnC2O4 and Na2C2O4 structures and consldered as the first member of a new series Na2Sn1+n(C2O4)2+n with n integer ? 0.  相似文献   

10.
The compounds (NH4)3[Ta(O2)4], K3[Ta(O2)4], Rb3[Ta(O2)4] and Cs3[Ta(O2)4] have been prepared and investigated by X-ray powder methods as well as Raman- and IR-spectroscopy. In the case of Rb3[Ta(O2)4] the structure has been solved from single crystal data. It is shown that all these compounds are isotypic and crystallize in the K3[Cr(O2)4] type (SG , No. 121). The infrared- and Raman spectra (recorded on powdered samples) are discussed with respect to the internal vibrations of the peroxo-group and the dodecahedral [Ta(O2)4]3− ion. Symmetry coordinates for the [Ta(O2)4]3− ion are given from which the vibrational modes of the O-O stretching vibrations of the O22− groups, the Ta-O stretching vibrations and the Ta-O bending vibrations are deduced.  相似文献   

11.
Raman spectroscopy complimented with infrared spectroscopy has been used to characterise the antimonate mineral bindheimite Pb2Sb2O6(O,OH). The mineral is characterised by an intense Raman band at 656 cm−1 assigned to SbO stretching vibrations. Other lower intensity bands at 664, 749 and 814 cm−1 are also assigned to stretching vibrations. This observation suggests the non-equivalence of SbO units in the structure. Low intensity Raman bands at 293, 312 and 328 cm−1 are assigned to the OSbO bending vibrations. Infrared bands at 979, 1008, 1037 and 1058 cm−1 may be assigned to δOH deformation modes of SbOH units. Infrared bands at 1603 and 1640 cm−1 are assigned to water bending vibrations, suggesting that water is involved in the bindheimite structure. Broad infrared bands centred upon 3250 cm−1 supports this concept. Thus the true formula of bindheimite is questioned and probably should be written as Pb2Sb2O6(O,OH,H2O).  相似文献   

12.
A new ammonium uranium (IV) oxalate (NH4)2U2(C2O4)5·0.7H2O (1) and three mixed uranium (IV)-lanthanide (III) oxalates, (N2H5)2.6U1.4M0.6(C2O4)5·xH2O (M=Nd (2) and M=Sm (3)), Na2.56U1.44Nd0.56(C2O4)5·7.6H2O (4) and Na3UCe(C2O4)5·10.4H2O (5), have been prepared. The crystal structures of compounds 1, 4 and 5 have been determined by single-crystal X-ray diffraction. The crystal structures were solved by the direct methods and Fourier difference techniques, and refined by a least square method on the basis of F2 for all unique reflections. Compounds 2 and 3 are isotypic with 1. Crystallographic data: 1, hexagonal, space group P63/mmc, a=19.177(3), c=12.728(4) Å, Z=6, R1=0.0575 for 52 parameters with 1360 reflections with I?2σ(I); 2, hexagonal, space group P63/mmc, a=19.243(4), c=12.760(5) Å, Z=6; 3, hexagonal, space group P63/mmc, a=19.211(3), c=12.274(4) Å, Z=6; 4, orthorhombic, space group Pbcn, a=18.79(3), b=11.46(1), c=12.77(2) Å, Z=4, R1=0.0511 for 183 parameters with 3026 reflections with I?2σ(I); 5, monoclinic, space group C2/c, a=18.878(6), b=11.684(4), c=12.932(4) Å, β=95.97(1)°, Z=4, R1=0.0416 for 213 parameters with 4060 reflections with I?2σ(I). The honeycomb-like structure of the five compounds is built from the same three-dimensional arrangement of metallic and oxalate ions. Similar hexagonal rings of alternating metallic and oxalate ions form layers parallel to the (001) plane that are pillared by another oxalate ion. Indeed, some torsions or rotations of the bridging oxalate ligands led to modifications of the network symmetry. The monovalent cations and the water molecules occupy the hexagonal tunnels running down the [001] direction. Starting from the uranium (IV) compound A2U2(C2O4)5·0.7H2O with A=NH4+ (1), the mixed U(IV)/Ln(III) oxalates are obtained by partial substitution of U(IV) by Ln(III) in a ten-coordinated site, the charge deficit being compensated by intercalation of supplementary monovalent ions within the tunnels. The distortion of the arrangement in the [001] direction for the Na-containing compounds allows the accommodation of a greater number of water molecules that insure an octahedral coordination of the Na atoms.  相似文献   

13.
By hydrothermal reaction of In2O3 with H2C2O4·2H2O in the presence of H3BO3 at 155 °C, an open-framework three-dimensional indium oxalate of formula [In(OH)(C2O4)(H2O)]3·H2O (1) has been obtained. The compound crystallizes in the trigonal system, space group R3c with , , , Z=6, R1=0.0352 at 298 K. The small pores in 1 are filled with water molecules. It loses its filled water at about 180 °C without the change of structure, then the bounded water at 260 °C, and completely decompounds at 324 °C. The residue is confirmed to be In2O3.  相似文献   

14.
Two new potassium uranyl molybdates K2(UO2)2(MoO4)O2 and K8(UO2)8(MoO5)3O6 have been obtained by solid state chemistry . The crystal structures were determined by single crystal X-ray diffraction data, collected with MoKα radiation and a charge coupled device (CCD) detector. Their structures were solved using direct methods and Fourier difference techniques and refined by a least square method on the basis of F2 for all unique reflections, with R1=0.046 for 136 parameters and 1412 reflections with I?2σ(I) for K2(UO2)2(MoO4)O2 and R1=0.055 for 257 parameters and 2585 reflections with I?2σ(I) for K8(UO2)8(MoO5)3O6. The first compound crystallizes in the monoclinic symmetry, space group P21/c with a=8.250(1) Å, b=15.337(2) Å, c=8.351(1) Å, β=104.75(1)°, ρmes=5.22(2) g/cm3, ρcal=5.27(2) g/cm3 and Z=4. The second material adopts a tetragonal unit cell with a=b=23.488(3) Å, c=6.7857(11) Å, ρmes=5.44(3) g/cm3, ρcal=5.49(2) g/cm3, Z=4 and space group P4/n.In both structures, the uranium atoms adopt a UO7 pentagonal bipyramid environment, molybdenum atoms are in a MoO4 tetrahedral environment for K2(UO2)2(MoO4)O2 and MoO5 square pyramid coordination in K8(UO2)8(MoO5)3O6. These compounds are characterized by layered structures. The association of uranyl ions (UO7) and molybdate oxoanions MoO4 or MoO5, give infinite layers [(UO2)2(MoO4)O2]2− and [(UO2)8(MoO5)3O6]8− in K2(UO2)2(MoO4)O2 and K8(UO2)8(MoO5)3O6, respectively. Conductivity properties of alkali metal within the interlayer spaces have been measured and show an Arrhenius type evolution.  相似文献   

15.
The thermal behaviour of BaC2O4sd0.5H2O and BaCO3 in carbon dioxide and nitrogen atmospheres is investigated as part of a study about the thermal decomposition of barium trioxalatoaluminate. For this purpose thermogravimetry, differential thermal analysis, differential scanning calorimetry and high temperature X-ray diffraction were used. An infrared absorption spectrum of BaC2O4·0.5H2O was scanned at room temperature.At increasing temperature, in dry nitrogen, the hydrate water of BaC2O4· 0.5H2O is split off, followed by the oxalate decomposition. A part of the evolved carbon monoxide disproportionates, leaving carbon behind. At higher temperatures the latter reacts with barium carbonate, previously formed. Finally the residual solid barium carbonate decomposes into barium oxide and carbon dioxide.In dry carbon dioxide atmosphere an analogous dehydration occurs, followed by oxalate decomposition. Under these conditions the carbon formation is fully suppressed, and as a consequence no secondary reaction occurs. The barium carbonate decomposition is shifted to much higher temperatures, at a low rate in the solid phase, a strongly accelerated one at the onset of melting, and a moderated one when the melt is saturated with barium carbonate. The two phase transitions of BaCO3 are detectable in both atmospheres mentioned.  相似文献   

16.
Nuclear magnetic resonance of 27Al nuclei was used to determine the quadrupole splitting constants νQ of the Al3+ ion in the oxalate complexes of NaMgAl(C2O4)3·8H2O and NaMgAl(C2O4)3·9H2O. The eightfold-hydrated crystal was obtained by annealing a ninefold-hydrated crystal. The resonance spectrum of the ninefold-hydrated crystal is split and the asymmetry parameter η amounts to 0.076.  相似文献   

17.
New titanyl phosphate Ti2O(H2O)(PO4)2 has been prepared and characterized by X-ray and neutron diffraction, nuclear magnetic resonance, infrared and Raman spectroscopies and thermogravimetric analysis. The crystal structure has been solved from neutron powder diffraction data at 300 K by Rietveld method in P21 space group. The refinement led to satisfactory profile factors (Rp=2.7%, Rwp=3.2%) and crystal structure model indicators (RB=5.8%, RF=3.2%). The cell is monoclinic with a=7.3735 Å, b=7.0405 Å, c=7.6609 Å and β=121.48°, Z=4. The structure can be described as a three-dimensional framework built up by chains of [TiO5(OH2)] octahedra with alternative short bonds [Ti(1)-O(12); Ti(2)-O(12), 1.88-1.84 Å] and long ones [Ti(1)-OW; Ti(2)-OW, 2.25-2.23 Å] along c-axis and connected via [PO4] tetrahedra. Oxygen atom denoted O(12) is only linked to two titanium atoms and Oxygen atom denoted OW is linked to two titanium atoms and two hydrogen atoms. O(12) and OW are not linked to P atoms and justify the titanyl phosphate formulation Ti2O(H2O)(PO4)2. The infrared and Raman spectra presents peaks due to vibrations of Ti-O, P-O and O-H bonds. The 31P MAS NMR spectrum reveals two 31P resonance lines, in agreement with the structure which showed two crystallographic sites for phosphorus. The thermogravimetric analysis show that Ti2O(H2O)(PO4)2 is thermally stable until 400 °C. Above this temperature, it losses water and decomposes to Ti5O4(PO4)4 and TiP2O7.  相似文献   

18.
Second-order infrared spectra of the crystal K4Fe(CN)6.3H2O are obtained in the region of 3700–7200 cm?1 at 90 K. The bands corresponding to overtones and combinations of the stretching and bending modes of the different water molecules are discussed and interpreted. The anharmonicity constants are estimated using the observed frequencies.  相似文献   

19.
The IR spectra of gaseous and solid (PF2)2O has been recorded from 80 to 1200 cm?1. The Raman spectra of gaseous, liquid and solid (PF2)2O have also been obtained (30–1000 cm?1). The spectra of the fluid phases indicate the presence of at least two conformers. The spectrum of the solid phase can readily be interpreted on the basis of a single conformer possessing a symmetry lower than C2v. A vibrational assignment is proposed for all normal modes except the PF2 torsions. The results are compared with similar data of related compounds. There appear to be two molecules per primitive cell based upon the low-frequency Raman data.  相似文献   

20.
A tin(II) squarate Sn2O(C4O4)(H2O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å3, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn4O10)(H2O)2] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn2[Sn2O2F4] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction.  相似文献   

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