Crystals Of Na Research Articles

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na2(PuO2)(BO3).

As part of our exploration of plutonium-containing materials as potential nuclear waste forms, we report the first extended structure Pu(V) material and the first Pu(V) borate. Crystals of Na2(PuO2)(BO3) were grown out of mixed hydroxide/boric acid flux and found to crystallize in the orthorhombic space group Cmcm with lattice parameters of a = 9.9067(4) Å, b = 6.5909(2) Å, and c = 6.9724(2) Å. Na2(PuO2)(BO3) adopts a layered structure in which layers of PuO2(BO3)2- are separated by sodium cations. Plutonium is found in a pentagonal bipyramidal coordination environment, with axial Pu(V)-O plutonyl bond lengths of 1.876(3) Å and equatorial Pu-O bond lengths ranging from 2.325(5) to 2.467(3) Å. We find that the Pu(V)-O plutonyl bond lengths are approximately 0.1 Å longer than the reported Pu(VI)-O plutonyl bond lengths and shorter by approximately 0.033 Å than the corresponding U(V) uranyl bond lengths. Raman spectroscopy on single crystals was used to determine the PuO2+ plutonyl stretching and the equatorial breathing mode frequencies of the pentagonal bipyramidal coordination environment around plutonium. Density functional theory calculations were used to calculate the Raman spectrum to help identify the Raman bands at 690 and 630 cm-1 as corresponding to the plutonyl(V) ν1 stretch and the equatorial PuO5 breathing mode, respectively. UV-vis measurements on single crystals indicate semiconducting behavior with a band gap of ∼2.60 eV.

Ionothermal Synthesis of Sulfidobismuth spiro-Dicubane Cations.

Bi2S3 was dissolved in the presence of NaCl in the ionic liquid [BMIm]Cl ⋅ 4AlCl3 (BMIm=1‐n‐butyl‐3‐methylimidazolium) through annealing the mixture at 180 °C. Upon cooling to room temperature, orange, air‐sensitive crystals of Na(Bi7S8)[S(AlCl3)3]2[AlCl4]2 (1) precipitated. X‐ray diffraction on single‐crystals of 1 revealed a triclinic crystal structure that contains (Bi7S8)5+ spiro‐dicubanes, [S(AlCl3)3]2− tetrahedra triples, isolated [AlCl4]− tetrahedra, and sodium cations.

Formation of nanoscale sodium dodecahydro-closo- dodecaborate Na2[B12H12] on silicate matrix surface

The method of nanoscaled sodium dodecahydro-closo-dodecaborate Na2[B12H12] synthesis is presented. The composite is heated to 200°C to yield the desired product, forming with the introduction of triethyl- ammonium salt [Et3NH]2[B12H12] into the silicate matrix of a sodium liquid glass. The morphology and phase composition of the synthesized sample are studied through SEM and X-ray diffraction methods, in comparison to those of a standard salt sample Na2[B12H12]. Based on the obtained data, the sample under study is an amorphous composite, on the surface of which nanoscale crystals of Na2[B12H12] form.

Formation of Nanoscale Sodium Dodecahydro-closo-Dodecaborate Na2[B12H12] on the Surface of a Silicate Matrix

The method of synthesis of nanoscaled sodium dodecahydro-closo-dodecaborate Na2[B12H12] is presented. The desired product has been prepared by heating to 200°C the composite formed by the introduction of the triethylammonium salt [Et3NH]2[B12H12] into the silicate matrix of sodium liquid glass. The morphology and phase composition of the synthesized sample have been studied by SEM and X-ray diffraction methods in comparison with regular Na2[B12H12] salt. According to the obtained data, the sample under study is an amorphous composite, on the surface of which nanoscale crystals of Na2[B12H12] are formed.

Growth and magneto-optical properties of Na0.37Tb0.63F2.26 cubic single crystal

Crystals of Na0.37Tb0.63F2.26 solid solution with a fluorite structure have been grown from melt by the Bridgman technique. The measured values of the Verdet constant are V = 0.35 ± 0.02 and 0.105 ± 0.01 arcmin/(Oe cm) for λ = 633 and 1060 nm, respectively. The dispersion of the Verdet constant is studied in the range of 380–1060 nm. The Na0.37Tb0.63F2.26 crystal is somewhat inferior to the previously studied noncubic fluoride crystals containing Tb3+ ions yields by V(λ) and is close to KTb3F10 crystal in totality of properties.

ChemInform Abstract: Preparation and Crystal Structure of Na4Cu2S3, a Thiocuprate with Discrete Anions.

Abstract Transparent pale yellow crystals of Na 4 Cu 2 S 3 were obtained from the melt of a corresponding mixture of the binary sulphides. Na 4 Cu 2 S 3 is tetragonal, space group I4 1 /a with a = 9.468(1) A , c=36.64(2) A and Z=16 . The crystal structure was determined from four-circle diffractometer data and refined to a conventional R of 0.021 for 1682 observed reflections with F 0 2 > 3 σ ( F 0 2 ) and 83 variables. An outstanding feature of Na 4 Cu 2 S 3 is the formation of discrete V-shaped thiocuprate anions [SCuSCuS] 4− with copper in an almost linear coordination by sulphur. The bond lengths ( d CuS =2.15 A ) and angles are in good agreement with those of the infinite anionic chains of KCuS. The crystal structure is based on a cubic close-packed arrangement of sulphur atoms with sodium in the centres of the tetrahedral voids, while copper atoms are shifted from the centres towards one of the edges in order to attain a linear co-ordination.

ChemInform Abstract: Na2Hg3S4; a Thiomercurate with Layered Anions

Abstract Dark red crystals of Na 2 Hg 3 S 4 were obtained by reacting a stoichiometric mixture of Na 2 S and HgS at 870 K. Na 2 Hg 3 S 4 is orthorhombic, oP36 , space group Pbca with a=7.308(5) A , b=14.011(8) A , c=8.231(3) A and Z =4. The crystal structure was determined from four-circle diffractometer data and refined to a conventional R of 0.056 for 718 reflections with F 0 2 >3 σ ( F o 2 ) and 43 variables ( R w =0.065). Na 2 Hg 3 S 4 crystallizes with a new structure type whose outstanding feature is the formation of strongly corrugated anionic layers, α 2 - [Hg 3 S 4 ] 2− , running parallel to (010). These layers are based on a network of 16-membered rings formed by alternating mercury and sulphur atoms. Two thirds of the mercury atoms are in a trigonal planar co-ordination by sulphur (d Hg-S ≈ 2.49 A ) while the remaining atoms are linearly coordinated (d Hg-S =2.344 A ). The Na + ions are coordinated by five sulphur atoms in a distorted square pyramidal configuration. The structure of Na 2 Hg 3 S 4 can formally be derived from a distorted close-packed array of chalcogen atoms (stacking sequence, ( hc ) 2 ; stacking direction, [010]).

ChemInform Abstract: Na7Au5S6 - A Novel Thioaurate(I) Based on a b.c.c. Chalcogen Packing.

Abstract Colourless transparent crystals of Na 7 Au 5 S 6 were prepared by reacting a stoichiometric mixture of Na 2 S, gold and sulphur at 1070 K. The compound is orthorhombic, oP72, space group Pbcn (number 60) with a=10.424(6) A , b=7.024(6) A , c=22.27(1) A and Z =4. The compound crystallizes with a new structure type, which was determined from single-crystal diffractometer data (Mo Kα radiation). The structure was solved by direct methods and refined to a conventional R of 0.062 ( R w =0.059) for 685 F o with F o 2 >4 σ ( F o 2 ). The outstanding feature of Na 7 Au 5 S 6 — in a partial ionic description — is the coexistence of two very different anionic species — infinite ∞ 1 (AuS) − chains and isolated (AuS 2 ) 3− dumbbells — in its structure. In both anions gold is doubly coordinated by sulphur; Au-S distances are close to 2.30 A; and S-Au-S bond angles vary from 170.3° to 180°. The Na + ions which separate the anions are in a distorted tetrahedral sulphur coordination. The crystal structure is based on a cubic body-centred packing of chalcogen atoms; the principles of this packing are discussed.

Magnetic Excitations of NaxCoO2·yD2O –Neutron Scattering–

In neutron inelastic measurements on aligned crystals of Na x CoO 2 · y D 2 O, two magnetic peaks have been observed. One peak corresponds to the contribution of ferromagnetic fluctuations and another peak, that of antiferromagnetic fluctuations. Both have two-dimensional characteristics. The intensity of ferromagnetic fluctuation decreases with decreasing temperature T and becomes inappreciable below 25 K. In contrast, antiferromagnetic fluctuation remains finite at 5 K. We have also carried out specific heat measurements on several samples with different values of the 59 Co-nuclear quadrupole frequency (ν Q ) within the region \(12.0 < \nu_{\text{Q3}}\cong 3\nu_{\text{Q}} < 12.9\) MHz, where the superconducting, nonsuperconducting and superconducting phases appear in the transition temperature ( T c )–ν Q3 phase diagram with varying ν Q3 , and found that the electronic specific heat coefficient γ does not change so significantly as to indicate a topological change of the Fermi surface with ν Q . These r...

THERMAL STABILITY AND TRANSPORT PROPERTIES OF Na0.495CoO2 SINGLE CRYSTALS

Single crystals of Na 0.495 CoO 2 were obtained through a flux method followed by de-intercalation of sodium. The resistivity (ρ) and thermal stability were studied for the de-intercalated samples exposed to humid air. It was found that the de-intercalated Na 0.495 CoO 2 crystal is vulnerable to water in the air, and a hydration process in which H 2 O molecules fill oxygen vacancies in CoO 2 layers instead of being intercalated between CoO 2 layers is suggested to be responsible for the remarkable change in resistivity induced by water absorption. The Na 0.495 CoO 2 sample shows a weak localization of carriers just below 200 K and Co 3+– Co 4+ charge ordering at about 40 K, lower than the corresponding charge ordering transition temperature reported in Na 0.5 CoO 2. The lower charge ordering transition temperature might be caused by the slight deviation of Na content (x) from 0.5.

Synthese und Kristallstruktur von Na3[W3Cl13

AbstractSynthesis and Crystal Structure of Na3[W3Cl13]A solid state reaction of tungsten(IV)chloride and sodium chloride yielded black plate‐like crystals of Na3[W3Cl13]. The structure of this compound was determined by single crystal X‐ray diffraction. Na3[W3Cl13] crystallizes in the monoclinic space group P 21/c with a = 9.093(1) Å, b = 23.851(4) Å, c = 9.155(1) Å, β = 120.26(1)°, and Z = 4. The crystal structure contains trigonal tungsten clusters ($\rm ({\bar d}_{w.w} = 2.737(1)\AA)$ = 2.737(1) Å) surrounded by chlorine atoms. The molecular [W3(μ3‐Cl)(μ‐Cl)3Cl9]3− cluster anions are forming layers parallel to the ac‐plane, sodium ions are located in and in between the layers.

A Novel Rigid Uranyl Tungstate Sheet in the Structures of Na2[(UO2)W2O8] and α‐ and β‐Ag2[(UO2)W2O8

AbstractFor Abstract see ChemInform Abstract in Full Text.

A novel rigid uranyl tungstate sheet in the structures of Na 2[(UO 2)W 2O 8] and α- and β-Ag 2[(UO 2)W 2O 8

Crystals of Na 2[(UO 2)W 2O 8] and α- and β-modifications of Ag 2[(UO 2)W 2O 8] were synthesized by high-temperature solid-state reactions and their structures have been determined. The structure of Na 2[(UO 2)W 2O 8] (triclinic, P 1 , a=6.6484(6), b=7.5308(7), c=8.4869(7) Å, α=89.952(2), β=86.190(2), γ=73.299(2)°, V=406.02(6) Å 3, Z=2) was solved by direct methods and refined to R 1=0.043 ( wR 2=0.084). The structure of α-Ag 2[(UO 2)W 2O 8] (monoclinic, P2 1/ c, a=8.4263(7), b=7.4897(7), c=12.927(1) Å, β=95.443(2)°, V=812.2(1) Å 3, Z=4) was solved by direct methods and refined to R 1=0.049 ( wR 2=0.104). The structure of β-Ag 2[(UO 2)W 2O 8] (orthorhombic, Pnma, a=8.6415(6), b=7.5610(6), c=12.4513(9) Å, V=813.6(1) Å 3, Z=4) was solved by direct methods and refined to R 1=0.059 ( wR 2=0.154). The crystal structures of the compounds are based upon sheets of UrO 5 pentagonal bipyramids (Ur = UO 2 2+, uranyl ion) and WO 6 octahedra with the composition [(UO 2)W 2O 8]. The UrO 5 pentagonal bipyramids share equatorial edges, resulting in chains one polyhedron wide that extend along [010] in all three structures. The WO 6 octahedra share corners to form chains of composition [WO 5] parallel to [010]. Two adjacent [WO 5] chains are linked into double [W 2O 8] chains by the sharing of edges between WO 6 octahedra. The chains of UrO 5 bipyramids and the [W 2O 8] chains are linked into sheets by the sharing of edges between UrO 5 bipyramids and WO 6 octahedra. The sheets are parallel to (100) in Na 2[(UO 2)W 2O 8] and to (001) in α- and β-Ag 2[(UO 2)W 2O 8]. Na and Ag are located in the interlayers, and provide linkage of the sheets. Geometrical parameters of the [(UO 2)W 2O 8] sheets in the structures of Na 2[(UO 2)W 2O 8] and α- and β-Ag 2[(UO 2)W 2O 8] are identical within ∼3%, which indicates a relatively rigid sheet. Thus, the role of the interlayer cations is to compensate the charge of the sheet and to link adjacent sheets. The α- and β-modifications of Ag 2[(UO 2)W 2O 8] differ only in stacking sequences of uranyl tungstate sheets and can be considered as Ag 2[(UO 2)W 2O 8]-2M and Ag 2[(UO 2)W 2O 8]-2O polytypes, respectively.

High-Resolution Optical Spectroscopy of Na3[Ln(dpa)3]·13H2O with Ln = Er3+, Tm3+, Yb3+

The title compounds were synthesized and studied by solution and single-crystal absorption, luminescence, and excitation spectroscopy. The f-f luminescence is induced in the Tm(3+) and Yb(3+) complexes in solution by exciting into the (1)Pi-(1)Pi absorptions of the ligand in the UV. A single-configurational coordinate model is proposed to rationalize the nonradiative relaxation step from ligand-centered to metal-centered excited states in [Yb(dpa)(3)](3-) (dpa = 2,6-pyridinedicarboxylate). Direct f-f excitation is used in crystals of Na(3)[Tm(dpa)(3)].13H(2)O and Na(3)[Yb(dpa)(3)].13H(2)O to induce f-f luminescence. From low-temperature, high-resolution absorption, luminescence, and excitation spectra, the ligand-field splittings in the relevant states can be determined. It was impossible to induce NIR to VIS upconversion in any of the complexes. This is mainly due to the fact that nonradiative relaxation among the f-f excited states is highly competitive, even in [Yb(dpa)(3)](3-) with an energy gap between (2)F(5/2) and (2)F(7/2) of about 10000 cm(-1). It can be rationalized on the basis of an adapted energy gap law. No luminescence at all could be detected in Na(3)[Er(dpa)(3)].13H(2)O.

A combined X-ray and NMR study of borate esters of furanoidic cis-1,2-diols

Crystals of K[B(AnErytH −2) 2]·2 H 2O (AnEryt=1,4-anhydroerythritol) form from aqueous alkaline solutions containing a double molar amount of diol over borate. The spiro-type monoanions are the main borate species in the mother liquors of crystallisation according to 11B and 13C NMR spectroscopy. Ribofuranosides form analogous borate esters using their 1,4-anhydroerythritol core. Crystals of Na[B(Meβ- d-Rib f 2,3H −2) 2]·2 H 2O were grown from alkaline methyl β- d-ribofuranoside solutions that had attacked boron-containing Duran vessels. NMR spectra show closely resembling borateester speciation in solutions of diols with the 1,4-anhydroerythritol core — 1,4-anhydroerythritol itself, methyl β- d-ribofuranoside and guanosine.

Natural Circular Dichroism at the Nd L3Edge in Single Crystals of Na3Nd(C4H4O5)32NaBF46H2O

We report the first attempt to detect circular dichroism (CD) in single crystals in the X-ray region using the unique circularly polarised beamline BL-6A at ESRF. Measurements have een made at the Nd L 3 edge on single crystals of Na 3 Nd(C 4 H 4 O 5 ) 3 2NaB 4 , 6H 2 O, which crystallises in the enantiomorphic spacegroup R32. Preliminary data analysis shows that there is a residual CD which has opposite sign for enantiomeric crystals and a dissymetry factor of around 5 x 10 -3 which is dose to the value predicted for natural CD.

Tetranuclear Phosphinidine, Phosphide, Arsenide, and Oxide Anionic Clusters of Molybdenum and Tungsten Supported by Neopentoxide Ligands: Na(18-crown-6)[M4(μ3-PSiMe3)(OCH2tBu)11], K(18-crown-6)[M4(μ3-E)(OCH2tBu)10] (E = P, As), K(18-crown-6)2[Mo4(μ3-O)(OCH2tBu)11

From the reactions between M2(OCH2tBu)6 (2 equiv) and NaP(SiMe3)2 (1 equiv) in benzene and 18-crown-6 the phosphinidine clusters [M4(μ3-PSiMe3)(OCH2tBu)11]-, compounds 1 (M = Mo) and 2 (M = W) are formed and are reactive intermediates in the formation of [M4(μ3-P)(OCH2tBu)10]- cluster anions, compounds 3 (M = Mo) and 4 (M = W), respectively, which have been isolated and characterized as their Na(18-crown-6)+ salts. Crystals of Na(18-crown-6)+[Mo4(μ3-P)(OCH2tBu)10]-·C6H6 were examined by single crystal X-ray crystallography at −110 °C in the space group Pn with a = 13.000(2) Å, b = 17.501(3) Å, c = 18.703(2) Å, and β = 93.11(1)° with Z = 2 and at −173 °C in the space group Cc with a = 22.118(4) Å, b = 17.480(3) Å, c = 23.250(4) Å, and β = 110.82(1)° with Z = 4. At the lower temperature, there is higher symmetry and no disorder of the 18-crown-6 molecule. The cluster anion has a Mo4 butterfly with a μ3-P ligand and virtual mirror symmetry. One wing-tip Mo atom is five-coordinate and bonded to the μ3-P atom and shows longer Mo-to-Mo distances (2.68(1) and 2.71(1) Å) relative to its counterpart (2.48(1) and 2.50(1) Å); the backbone Mo−Mo distance is 2.53(1) Å. The cluster anion in 3 but not 4 is also accessible from the reaction between Mo2(OCH2tBu)6 (2 equiv), PH3, and KOCH2tBu (1 equiv) in THF/18-crown-6 (THF = tetrahydrofuran). A similar approach involving AsH3, Mo2(OCH2tBu)6, and KOCH2tBu gave the μ3-arsenide cluster complex K(18-crown-6)+[Mo4(μ3-As)(OCH2tBu)10]-, compound 5, which by NMR spectroscopy is analogous in structure to 3. The reaction between Mo2(OCH2tBu)6 (2 equiv) and KOH in THF/18-crown-6 gave K(18-crown-6)2+[Mo4(μ3-O)(OCH2tBu)11]-, compound 6, which is proposed to be isostructural with the phosphinidine complexes 1 and 2 on the basis of NMR data. Crystal data for K(η6-C12H24O6)(η2-C12H24O6)+[Mo4(μ3-O)(OCH2tBu)11]- at −165 °C: a = 17.595(2) Å, b = 28.044(3) Å, c = 20.443(2) Å, β = 97.61(1)° with Z = 4, and space group P21/n. The cluster anion in 6 contains a 12-electron Mo4 butterfly with 12 M−M bonding electrons, as in 3, but the shortest Mo−Mo distance 2.42(1) Å involves the backbone metal atoms. The Mo−Mo distances involving the oxo-capped triangle (2.61(1) and 2.62(1) Å) are notably longer than those in the other triangle (2.48(1) Å).

Impedance spectroscopy on [formula omitted] crystals

Crystals of Na +−β″-Al 2O 3 and Na + Ho 3+ −β″-Al 2O 3 , with varying degrees of exchange, have been investigated by impedance spectroscopy using sputtered chromium films as electrodes. For this work a sample holder was developed to enable studies of the in-plane conductivity of even very thin β″-alumina crystals. The ionic conductivities of the investigated Na +−β″-Al 2O 3 crystals were found to be one order of magnitude lower than those reported in the literature, a discrepancy caused by a lower charge carrier concentration. On the other hand, the activation energy and the diffusion coefficients of the sodium ions, as deduced from the Nernst-Einstein equation, agree well with previous studies. In the case of the Na + Ho 3+ −β″-Al 2O 3 crystals, a strong decrease of the ionic conductivity has been observed with increasing degree of exchange. To determine the bulk conductivities an equivalent circuit had to be applied which differed from the one used in case of Na +−β″-Al 2O 3. With an additional RC-element in parallel these spectra could be fitted with satisfying results. This RC-element may be regarded as a second relaxation process of the Na + ions.

Time-resolved chiroptical luminescence spectra of UO 22+ in cubic Na[UO 2(CH 3COO) 3] crystals: evidence for circular dichroic self-absorption

Time-resolved chiroptical luminescence (TR-CL) measurements are reported for cubic crystals of Na[UO 2(CH 3COO) 3]. These crystals belong to the enantiomorphic space group P2 13, and they exhibit strong chiroptical activity within the Σ g + ← Π g emission spectrum of UO 2 2+. Circular polarization is observed in the origin line of this spectrum, as well as in a vibronic progression from the origin based on the symmetric stretching mode ( ν S) of UO 2 2+. The TR-CL results are used to confirm the presence of circular dichroic self-absorption within the origin transition.

Optical spectroscopy of praseodymium-exchanged Na + β-alumina crystals

Crystals of Na +/Pr 3+ β-Al 2O 3 with different amounts of lanthanide ions have been investigated by optical spectroscopy methods between 4.2 K and 300 K. Optical absorption spectra in the visible region show three main features which are related to the 3H 4→ 3P 0, 3H 4→ 3P 1( 1I 6) and 3H 4å 3P 2 transitions. Polarized luminescence spectra have been recorded under cw excitation of various Ar + ion laser lines. Complex emission spectra consisting of several, not fully resolved, components even at very low temperature, are observed for the 3P 0→ 3H 4 transition between 20000 and 210000 cm −1. Excitation spectra and resonant fluourescence line narrowing (FLN) spectra of different components of this transition recorded at low temperature indicate the presence of, at least, two distinct sets of centers, in agreement with recent structural refinement results. Finally, we have evaluated the energy levels and crystal-field splittings by ligand-field calculations based on the angular overlap model (AOM). Our calculations reproduce the ground state splitting of Pr 3+ ions in the β-Al 2O 3 structure with different site symmetrics.