Oxonium Ions Substituting Cesium Ions in the Structure of the New High‐Pressure Borate HP‐Cs1−x(H3O)xB3O5 (x=0.5–0.7)

The new high‐pressure borate HP‐Cs_1?x(H₃O)_xB₃O₅ (x=0.5–0.7) was synthesized under high‐pressure/high‐temperature conditions of 6 GPa/900 °C in a Walker‐type multianvil apparatus. The compound crystallizes in the monoclinic space group C2/c (Z=8) with the parameters a=1000.6(2), b=887.8(2), c=926.3(2) pm, β=103.1(1)°, V=0.8016(3) nm³, R1=0.0452, and wR2=0.0721 (all data). The boron–oxygen network is analogous to those of the compounds HP‐MB₃O₅, (M=K, Rb) and exhibits all three structural motifs of borates—BO₃ groups, corner‐sharing BO₄ tetrahedra, and edge‐sharing BO₄ tetrahedra—at the same time. Channels inside the boron–oxygen framework contain the cesium and oxonium ions, which are disordered on a specific site. Estimating the amount of hydrogen by solid‐state NMR spectroscopy and X‐ray diffraction led to the composition HP‐Cs_1?x(H₃O)_xB₃O₅ (x=0.5–0.7), which implies a nonzero phase width.     

MH4P6N12 (M=Mg,Ca): New Imidonitridophosphates with an Unprecedented Layered Network Structure Type

Isotypic imidonitridophosphates MH₄P₆N₁₂ (M=Mg, Ca) have been synthesized by high‐pressure/high‐temperature reactions at 8 GPa and 1000 °C starting from stoichiometric amounts of the respective alkaline‐earth metal nitrides, P₃N₅, and amorphous HPN₂. Both compounds form colorless transparent platelet crystals. The crystal structures have been solved and refined from single‐crystal X‐ray diffraction data. Rietveld refinement confirmed the accuracy of the structure determination. In order to quantify the amounts of H atoms in the respective compounds, quantitative solid‐state ¹H NMR measurements were carried out. EDX spectroscopy confirmed the chemical compositions. FTIR spectra confirmed the presence of NH groups in both structures. The crystal structures reveal an unprecedented layered tetrahedral arrangement, built up from all‐side vertex‐sharing PN₄ tetrahedra with condensed dreier and sechser rings. The resulting layers are separated by metal atoms.     

Synthesis and structure determination of seven ternary bismuthides: crystal chemistry of the RELi3Bi2 family (RE = La–Nd,Sm, Gd,and Tb)

Zintl phases are renowned for their diverse crystal structures with rich structural chemistry and have recently exhibited some remarkable heat‐ and charge‐transport properties. The ternary bismuthides RELi₃Bi₂ (RE = La–Nd, Sm, Gd, and Tb) (namely, lanthanum trilithium dibismuthide, LaLi₃Bi₂, cerium trilithium dibismuthide, CeLi₃Bi₂, praseodymium trilithium dibismuthide, PrLi₃Bi₂, neodymium trilithium dibismuthide, NdLi₃Bi₂, samarium trilithium dibismuthide, SmLi₃Bi₂, gadolinium trilithium dibismuthide, GdLi₃Bi₂, and terbium trilithium dibismuthide, TbLi₃Bi₂) were synthesized by high‐temperature reactions of the elements in sealed Nb ampoules. Single‐crystal X‐ray diffraction analysis shows that all seven compounds are isostructural and crystallize in the LaLi₃Sb₂ type structure in the trigonal space group Pm1 (Pearson symbol hP6). The unit‐cell volumes decrease monotonically on moving from the La to the Tb compound, owing to the lanthanide contraction. The structure features a rare‐earth metal atom and one Li atom in a nearly perfect octahedral coordination by six Bi atoms. The second crystallographically unique Li atom is surrounded by four Bi atoms in a slightly distorted tetrahedral geometry. The atomic arrangements are best described as layered structures consisting of two‐dimensional layers of fused LiBi₄ tetrahedra and LiBi₆ octahedra, separated by rare‐earth metal cations. As such, these compounds are expected to be valance‐precise semiconductors, whose formulae can be represented as (RE³⁺)(Li¹⁺)₃(Bi³⁻)₂.     

High Pressure Synthesis and Characterization of New Members of the RuSr2(RE,Ce)2Cu2O10 Family (RE = Y,Dy)

New members of the RuSr₂(RE_2?x, Ce_x)Cu₂O₁₀ family of magnetically ordered phases have been synthesized under high pressure / high temperature conditions for RE = Y (x = 0.5, 0.7) and Dy (x = 0.5). All compounds show tetragonal symmetry with cell parameters a ≈ 3.82 Å and c ≈ 28.4 Å. Magnetic susceptibility vs temperature measurements show ferromagnetic behaviour of these compounds with T_M = 120–140 K, depending on Ce content. These compounds are semiconducting and tend to transform into insulator, by increasing Ce content, as observed by the temperature dependence of the resistance.     

High‐pressure syntheses of α‐RE2B4O9 (RE = Sm,Ho), with a structure type displaying edge‐sharing BO4 tetrahedra

The compounds α‐RE₂B₄O₉, with RE = Sm (disamarium tetraborate) and Ho (diholmium tetraborate), were synthesized under conditions of high pressure and high temperature in a Walker‐type multianvil apparatus, at 7.5 GPa and 1323 K for α‐Sm₂B₄O₉ and at 10 GPa and 1323 K for α‐Ho₂B₄O₉. The crystal structures were determined from single‐crystal X‐ray diffraction data collected at room temperature. The structures are isotypic with the already known α‐RE₂B₄O₉ (RE = Eu–Dy) phases, displaying the new structural motif of edge‐sharing BO₄ tetrahedra next to the known motif of corner‐sharing BO₄ tetrahedra. As the end members of this isotypic series, the two title compounds mark the borders of the stability field of the appearance of edge‐sharing BO₄ tetrahedra.     

High‐Pressure Synthesis and Characterization of New Actinide Borates,AnB4O8 (An=Th,U)

New actinide borates ThB₄O₈ and UB₄O₈ were synthesized under high‐pressure, high‐temperature conditions (5.5 GPa/1100 °C for thorium borate, 10.5 GPa/1100 °C for the isotypic uranium borate) in a Walker‐type multianvil apparatus from their corresponding actinide oxide and boron oxide. The crystal structure was determined on basis of single‐crystal X‐ray diffraction data that were collected at room temperature. Both compounds crystallized in the monoclinic space group C2/c (Z=4). Lattice parameters for ThB₄O₈: a=1611.3(3), b=419.86(8), c=730.6(2) pm; β=114.70(3)°; V=449.0(2) ų; R₁=0.0255, wR₂=0.0653 (all data). Lattice parameters for UB₄O₈: a=1589.7(3), b=422.14(8), c=723.4(2) pm; β=114.13(3)°; V=443.1(2) ų; R₁=0.0227, wR₂=0.0372 (all data). The new AnB₄O₈ (An=Th, U) structure type is constructed from corner‐sharing BO₄ tetrahedra, which form layers in the bc plane. One of the four independent oxygen atoms is threefold‐coordinated. The actinide cations are located between the boron–oxygen layers. In addition to Raman spectroscopic investigations, DFT calculations were performed to support the assignment of the vibrational bands.     

Analogy of the coordination chemistry of alkaline earth metal and lanthanide Ln(2+) ions: the isostructural zoo of mixed metal cages [IM(OtBu)4{Li(thf)}4(OH)] (M=Ca, Sr, Ba, Eu), [MM'6(OPh)8(thf)6] (M=Ca, Sr, Ba, Sm, Eu, M'=Li, Na), and their derivatives with 1,2-dimethoxyethane

As previously shown, alkali and alkaline earth metal iodides in nonaqueous, aprotic solvents behave like transition metal halides, forming cis- and trans-dihalides with various neutral O-donor ligands. These compounds can be used as precursors for the synthesis of new mixed alkali/alkaline earth metal aggregates. We show here that Ln2+ ions form isostructural cluster compounds. Thus, with LiOtBu, 50% of the initial iodide can be replaced in MI2, M=Ca, Sr, Ba, Eu, to generate the mixed-metal alkoxide aggregates [IM(OtBu)4{Li(thf)}4(OH)], for which the M--OH contacts were investigated by theoretical methods. With M'OPh (M'=Li, Na), a new mixed-metal aryloxide cluster type [MM'6(OPh)8(thf)6] is obtained for M=Ca, Sr, Ba, Sm, Eu. Their stability versus DME (DME=1,2-dimethoxyethane) as bidentate ligand is studied.     

High‐Pressure Synthesis of Cd(NH3)2[B3O5(NH3)]2: Pioneering the Way to the Substance Class of Ammine Borates

To date, the access to the substance class of borates containing nitrogen, for example, nitridoborates, oxonitridoborates, or amine borates, was an extreme effort owing to the difficult starting materials and reaction conditions. Although a number of compounds containing boron and nitrogen are known, no adduct of ammonia to an inorganic borate has been observed so far. A new synthetic approach starting from the simple educts CdO, B₂O₃, and aqueous ammonia under conditions of 4.7 GPa and 800 °C led to the synthesis of Cd(NH₃)₂[B₃O₅(NH₃)]₂ as the first ammine borate. We thoroughly characterized this compound on the basis of low‐temperature single‐crystal and powder X‐ray diffraction data, IR and Raman spectroscopy, and by quantum theoretical calculations. This contribution shows that the adduct of NH₃ to the BO₃ group of a complex B–O network can be stabilized, opening up a fundamentally new synthetic route to nitrogen‐containing borates.     

Rb2REGaSi4O12 (RE = Y, Eu, Gd, Tb): luminescent mixed-anion double layer silicates containing chains of edge-sharing REO7 pentagonal bipyramids

Four new rare earth gallosilicates, Rb 2REGaSi4O12 (RE = Y, Eu, Gd, and Tb, denoted as REGS-1), have been synthesized under high-temperature, high-pressure hydrothermal conditions and characterized by single-crystal X-ray diffraction. They are the first examples of rare earth gallosilicates that contain individually occupied tetrahedral Ga(3+) and Si(4+) centers. The unique structure is formed of two 1D and one 2D substructural units: unbranched achter single chains which are seldom observed in silicates, the PaCl 5-type infinite chains formed of edge-sharing REO7 petagonal bipyramids and the unprecedented mixed-anion double layers with the composition [GaSi4O12]. The photoluminescence properties of EuGS-1 and TbGS-1 have been studied. The Y(3+) ion in YGS-1 can be partially replaced by Eu(3+) and Tb(3+) to yield luminescent materials.     

Pentacoordinate Phosphorus in a High‐Pressure Polymorph of Phosphorus Nitride Imide P4N6(NH)

Coordination numbers higher than usual are often associated with superior mechanical properties. In this contribution we report on the synthesis of the high‐pressure polymorph of highly condensed phosphorus nitride imide P₄N₆(NH) representing a new framework topology. This is the first example of phosphorus in trigonal‐bipyramidal coordination being observed in an inorganic network structure. We were able to obtain single crystals and bulk samples of the compound employing the multi‐anvil technique. γ‐P₄N₆(NH) has been thoroughly characterized using X‐ray diffraction, solid‐state NMR and FTIR spectroscopy. The synthesis of γ‐P₄N₆(NH) gives new insights into the coordination chemistry of phosphorus at high pressures. The synthesis of further high‐pressure phases with higher coordination numbers exhibiting intriguing physical properties seems within reach.     

Rare-earth tricyanomelaminates [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)H(2)O (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy): structural investigation, solid-state NMR spectroscopy, and photoluminescence

The rare-earth tricyanomelaminates, [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O (LnTCM; Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy), have been synthesized through ion-exchange reactions. They have been characterized by powder as well as single-crystal X-ray diffraction analysis, vibrational spectroscopy, and solid-state (1)H, (13)C, and (15)N MAS NMR spectroscopy. The X-ray powder pattern common to all nine rare-earth tricyanomelaminates LnTCM (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) indicates that they are isostructural. The single-crystal X-ray diffraction pattern of LnTCM is indicative of non-merohedral twinning. The crystals are triclinic and separation of the twin domains as well as refinement of the structure were successfully carried out in the space group P1 for LaTCM (LaTCM; P1, Z=2, a=7.1014(14), b=13.194(3), c=13.803(3) A, alpha=90.11(3), beta=77.85(3), gamma=87.23(3) degrees , V=1262.8(4) A(3)). In the crystal structure, each Ln(3+) is surrounded by two nitrogen atoms from two crystallographically independent tricyanomelaminate moieties and seven oxygen atoms from crystal water molecules. The positions of all of the hydrogen atoms of the ammonium ions and water molecules could not be located from difference Fourier syntheses. The presence of [NH(4)](+) ions as well as two NH groups belonging to two crystallographically independent monoprotonated tricyanomelaminate moieties has only been confirmed by subjecting LaTCM to solid-state (1)H, (13)C, and (15)N{(1)H} cross-polarization (CP) MAS NMR and advanced CP experiments such as cross-polarization combined with polarization inversion (CPPI). The (1)H 2D double-quantum single-quantum homonuclear correlation (DQ SQ) spectrum and the (15)N{(1)H} 2D CP heteronuclear-correlation (HETCOR) spectrum have revealed the hydrogen-bonded (N--HN) dimer of monoprotonated tricyanomelaminate moieties as well as H-bonding through [NH(4)](+) ions and H(2)O molecules. The structures of the other eight rare-earth tricyanomelaminates (LnTCM; Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) have been refined from X-ray powder diffraction data by the Rietveld method. Photoluminescence studies of [NH(4)]Eu[HC(6)N(9)](2)[H(2)O](7)xH(2)O have revealed orange-red (lambda(max)=615 nm) emission due to the (5)D(0)-(7)F(2) transition, whereas [NH(4)]Tb[HC(6)N(9)](2)[H(2)O](7)xH(2)O has been found to show green emission with a maximum at 545 nm arising from the (5)D(4)-(7)F(5) transition. DTA/TG studies of [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O have indicated several phase transitions associated with dehydration of the compounds above 150 degrees C and decomposition above 200 degrees C.     

Orthorhombic HP‐REOF (RE = Pr,Nd, Sm – Gd) – High‐Pressure Syntheses and Single‐Crystal Structures (RE = Nd,Sm, Eu)

High‐pressure modifications of the rare earth oxide fluorides REOF (RE = Pr, Nd, Sm – Gd) were successfully synthesized under conditions of 11 GPa and 1200 °C applying the multianvil high‐pressure/high‐temperature technique. Single crystals of HP‐REOF (RE = Nd, Sm, Eu) were obtained making it possible to analyze the products by means of single‐crystal X‐ray diffraction. The compounds HP‐REOF (RE = Nd, Sm, Eu) crystallize in the orthorhombic α‐PbCl₂‐type structure (space group Pnma, No. 62, Z = 4) with the parameters a = 632.45(3), b = 381.87(2), c = 699.21(3) pm, V = 0.16887(2) nm³, R₁ = 0.0156, and wR₂ = 0.0382 for HP‐NdOF, a = 624.38(3), b = 376.87(2), c = 689.53(4) pm, V = 0.16225(2) nm³, R₁ = 0.0141, and wR₂ = 0.0323 for HP‐SmOF, and a = 620.02(4), b = 374.24(3), c = 686.82(5) pm, V = 0.15937(2) nm³, R₁ = 0.0177, and wR₂ = 0.0288 for HP‐EuOF. Calculations of the bond valence sums clearly showed that the oxygen atoms occupy the tetrahedrally coordinated position, whereas the fluorine atoms are fivefold coordinated in form of distorted square‐pyramids. The crystal structures and properties of HP‐REOF (RE = Nd, Sm, Eu) are discussed and compared to the isostructural phases and the normal‐pressure modifications of REOF (RE = Nd, Sm, Eu). Furthermore, results of investigations by EDX and Raman measurements including quantum mechanical calculations are presented.     

Rare earth-rich cadmium compounds RE 4 TCd (T = Co, Ru, and Rh) with Gd4RhIn type structure

The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F ${\bar 4}The rare earth-rich cadmium compounds RE ₄ TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y₄RuCd (a = 1362.5(1) pm), La₄RuCd (a = 1415.9(1) pm), Gd₄RuCd (a = 1368.8(2) pm), La₄CoCd (a = 1417.9(4) pm), Gd₄CoCd (a = 1356.1(1) pm), and Gd₄RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE ₄ TCd compounds crystallize with the cubic Gd₄RhIn type structure, space group F 3m. The transition metal atoms have tricapped trigonal prismatic rare earth coordination. The trigonal prisms are condensed via common edges, forming a rigid three-dimensional network with adamantane symmetry. Voids in these networks are filled by Cd₄ tetrahedra (304 pm Cd–Cd in Gd₄CoCd) and polyhedra of the RE1 atoms. The crystal chemical peculiarities are briefly discussed. Correspondence: Rainer P?ttgen, Institut für Anorganische und Analytische Chemie, Westf?lische Wilhelms-Universit?t Münster, Correnstrasse 30, 48149 Münster, Germany.     

VUV spectroscopic properties of rare-earth (RE3+ = Sm3+, Eu3+, Tb3+, Dy3+) -activated layered borate Ba6Gd9B79O138

Vacuum ultraviolet (VUV) spectroscopic properties of rare-earth RE³⁺- activated (RE³⁺ = Sm³⁺, Eu³⁺, Tb³⁺ and Dy³⁺) Ba₆Gd₉B₇₉O₁₃₈ borates (BGBO) are investigated. The strong absorption bands in the VUV range of un-doped and RE³⁺-activated BGBO were observed. The band range from 140 to 200 nm with a peak at about 173 nm results from the host lattice absorption. For Sm³⁺-activated BGBO, the charge transfer transition from O^2- to Sm³⁺ was observed at 202 nm. In addition, it exhibits bright red emission originating from the Sm³⁺ f-f transitions of ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2 and 9/2). The O^2--Eu³⁺ charge transfer (CT) at 249 nm is observed in the excitation spectrum for Eu³⁺-doped BGBO. For Tb³⁺-activated BGBO, the broad bands around 208 and 230 nm are due to the spin-allowed and spin-forbidden f-d transitions of Tb³⁺, respectively. In addition, the absence of the f-d transitions of Sm³⁺ and Dy³⁺ in the excitation spectra probably due to the photo-ionization effect. It is demonstrated that there are energy transfers from the BGBO host lattice to the luminescent activators depending on the activators.     

掺杂铕和铽的卤硼酸盐荧光体的制备及光谱特征

采用高温固相法在空气中合成了一系列掺杂稀土离子的卤硼酸盐荧光体, 研究了其发光性质和基质组成对稀土离子共掺杂的荧光体发光性质的影响. 研究结果表明, 在Eu3+和Tb3+共掺杂的体系中存在电子转移, 因此出现了Eu3+, Eu2+和 Tb3+共存于同一基质共同发射的现象. Ce3+对Eu2+和Tb3+具有敏化作用, 可增强其发射强度. 基质的组成对稀土离子的发射峰位和发射强度有明显影响.