Sr5Al5+xSi21−xN35−xO2+x:Eu2+ (x≈0)—A Novel Green Phosphor for White‐Light pcLEDs with Disordered Intergrowth Structure

A novel sialon phosphor is characterized by an unusual silicate framework, built up of edge‐ and vertex‐sharing tetrahedra (orange and green). Owing to pronounced pseudotranslations, the compound is highly disordered. It was investigated in detail by X‐ray diffraction and electron microscopy. Despite the disorder, all Sr atoms (yellow spheres) exhibit very similar coordination spheres, and doping with Eu²⁺ results in efficient green luminescence (see inset; Em.=emission, Exc.=excitation, Refl.=reflection).

     

Barium‐deficient celsian,Ba1−xAl2−2xSi2+2xO8 (x = 0.20 or 0.06)

Barium‐deficient forms of celsian (barium aluminium silicate) with the formula Ba_1−xAl_2−2xSi_2+2xO₈ (x = 0.20 and 0.06) have been identified. In contrast with the celsian–orthoclase solid solutions which have been reported previously, these forms, refined in the space group C2/m, with Ba and one O atom in the 4i sites with m site symmetry, and a further O atom in a 4g site with twofold axial symmetry, suggest a slight solid solution with silica. The serendipitous preparation of the compounds represents a possible hazard associated with solid‐state synthesis.     

Electronic stabilization by occupational disorder in the ternary bismuthide Li3–x–yInxBi (x ≃ 0.14, y ≃ 0.29)

A ternary derivative of Li₃Bi with the composition Li_3–x–yIn_xBi (x ? 0.14, y ? 0.29) was produced by a mixed In+Bi flux approach. The crystal structure adopts the space group Fdm (No. 227), with a = 13.337 (4) Å, and can be viewed as a 2 × 2 × 2 superstructure of the parent Li₃Bi phase, resulting from a partial ordering of Li and In in the tetrahedral voids of the Bi fcc packing. In addition to the Li/In substitutional disorder, partial occupation of some Li sites is observed. The Li deficiency develops to reduce the total electron count in the system, counteracting thereby the electron doping introduced by the In substitution. First‐principles calculations confirm the electronic rationale of the observed disorder.     

Synthesis and structural characterization of the type‐I clathrates K8AlxSn46–x and Rb8AlxSn46–x (x ≃ 6.4–9.7)

Exploratory studies in the systems A–Al–Sn (A = K and Rb) yielded the clathrates K₈Al_xSn_46–x (potassium aluminium stannide) and Rb₈Al_xSn_46–x (rubidium aluminium stannide), both with the cubic type‐I structure (space group Pmn, No. 223; a ? 12.0 Å). The Al:Sn ratio is close to the idealized A₈Al₈Sn₃₈ composition and it is shown that it can be varied slightly, in the range of ca ±1.5, depending on the experimental conditions. Both the (Sn,Al)₂₀ and the (Sn,Al)₂₄ cages in the structure are fully occupied by the guest alkali metal atoms, i.e. K or Rb. The A₈Al₈Sn₃₈ formula has a valence electron count that obeys the valence rules and represents an intrinsic semiconductor, while the experimentally determined compositions A₈Al_8±xSn_38?x suggest the synthesized materials to be nearly charge‐balanced Zintl phases, i.e. they are likely to behave as heavily doped p‐ or n‐type semiconductors.     

Structural links between zeolite-type and clathrate hydrate-type materials: Synthesis and crystal Structure of [N(CH3)4]6[AlxSi8−xO18−x(OH)2+x] · 44H2O (x = 3–4)

A novel tetramethylammonium aluminosilicate hydrate with the approximate composition [NMe₄]₆[Al_xSi_8?xO_18?x(OH)_2+x] · 44H₂O (x = 3–4) has been identified by powder X-ray diffraction as a component in a polyphasic solid mixture which crystallized at room temperature from an aqueous NMe₄OH? Al₂O₃? SiO₂ solution. Large crystals of the novel hydrate phase could be mechanically selected from that mixture. The crystal structure has been determined from 1 196 unique MoKα diffraction data measured at 180 K: Tetragonal crystal system, cell constants a = 16.181(4) and c = 17.450(4) Å, space group P4/mnc with Z = 2 formula units per unit cell, R = 0.072. The host-guest compound is of polyhedral clathrate type with a mixed three-dimensional, (mainly) four-connected network composed of oligomeric aluminosilicate anions [Al_xSi_8?xO_18?x(OH)_2+x]^6? and H₂O molecules linked via hydrogen bonds O? H …? O. The aluminosilicate anions possess a cube-shaped (double four-ring) structure. Orientationally disordered cationic guest species NMe₄⁺ are enclosed in the large [4⁶6⁸] and [4¹5¹⁰6⁷] polyhedral voids of the host framework; the small [4⁶] cages (i.e. the double four-ring anions) and [4³5⁶] cages are empty. The hydrate is a further member in a recently discovered series of clathrates with mixed tetrahedral networks, which provides a structure-chemical link between zeolite- and clathrate hydrate-type host-guest compounds.     

A quantum chemistry study on boron nitrides (BNN)2n and (BNN)2n2+ (n = 3–8)

(BNN)_2n (n = 3–8) with eclipsed D_nh conformations (Series I), except (BNN)₈ with O_h conformation, (BNN)_2n²⁺ (n = 3–8) with staggered D_nd conformations (Series II), and the analogous BCO‐based compounds have been studied in the present paper using density functional theory. All the species are located as genuine minima and show high stability with respect to the dissociation into BNN (BCO) or N₂ (CO). It is found that the strong aromaticity is one of the important factors in the stability of Series II and the angular strain dominantly affects the stability of Series I with relatively weak aromaticity. The same is also observed for the corresponding BCO analogies. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis and molecular structure of 2,4,6‐tri[bis(diisopropylamino)boryl(methylamino)]borazine, [(NiPr2)2B(Me)N]3B3N3H3

Reaction of bis(diisopropylamino)(methylamino)borane, (NHⁱPr)₂B(NHMe), with 2,4,6‐trichloroborazine (ClBNH)₃ affords 2,4,6‐tri[bis(diisopropylamino)boryl(methylamino)]borazine, 2,4,6‐[(NⁱPr₂)₂B(Me)N]₃B₃N₃H₃, which is the first boryl‐borazine structurally characterized. According to the X‐ray single crystal structure and the chemical shifts of ¹¹B NMR resonances of boron atoms, compared with the aminoborane and borazine analogs, the borazine and boryl π‐systems are not coplanar either in the solid state or in organic solution. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and crystal structures of RE7Zn21+xSi2–x [RE = Ce,Pr, and Nd; 0.09 (1) < x < 0.95 (1)]

The focus of this paper is on the synthesis and crystal structures of three Zn‐rich compounds with the general formula RE₇Zn_21+xSi_2−x, where RE = Ce [x = 0.95 (1); heptacerium docosazinc silicon], Pr [x = 0.09 (1); heptapraseodymium henicosazinc disilicon], and Nd [x = 0.53 (1); heptaneodymium docosazinc silicon]. The compounds were obtained by high‐temperature reactions, using the respective elements as starting materials. The structures were determined by single‐crystal X‐ray diffraction. The title compounds crystalize in the orthorhombic space group Pbam (No. 55, Pearson symbol oP60) and are isostructural with about a dozen RE₇Zn_21+xTt_2−x (RE = La–Nd; Tt = Ge, Sn, and Pb) compounds previously reported by our group. The results from the present refinements confirm the previously published data on RE₇Zn_21+xSi_2−x (RE = La and Ce; x≃ 1.45) [Malik et al. (2013). Intermetallics, 36 , 118–126]. Additionally, magnetic susceptibility measurements on the corresponding bulk samples show Curie–Weiss paramagnetic behavior from 5 to 300 K, consistent with RE³⁺ ground states and local‐moment magnetism due to the core 4f electrons.     

The series RE5Li2Sn7 (RE = Ce,Pr, Nd,Sm) revisited: crystal structure of RE5Li2−xSn7+x [0 ≤x≤ 0.03 (1)]

The series of RE₅Li₂Sn₇ (RE = Ce–Sm) compounds were synthesized by high‐temperature reactions and structurally characterized by single‐crystal X‐ray diffraction. The compounds are pentacerium dilithium heptastannide, Ce₅Li_1.97Sn_7.03, pentapreseodymium dilithium heptastannide, Pr₅Li_1.98Sn_7.02, pentaneodymium dilithium heptastannide, Nd₅Li_1.99Sn_7.01, and pentasamarium dilithium heptastannide, Sm₅Li₂Sn₇. All five compounds crystallize in the chiral orthorhombic space group P2₁2₁2₁ (No. 19), which is relatively uncommon among intermetallic phases. The structure belongs to the Ce₅Li₂Sn₇ structure type (Pearson symbol oP56), with 14 unique atoms in the asymmetric unit. Minor compositional variations exist, due to the mixed occupancy of Li and Sn atoms at one of the Li sites. The small occupational disorder is most evident for RE₅Li_2−xSn_7+x (RE = Ce, Pr; x≃ 0.03), while the structure of Nd₅Li₂Sn₇ and Sm₅Li₂Sn₇ show no apparent disorder.     

Structural Evolution and Effect of the Neighboring Cation on the Photoluminescence of Sr(LiAl3)1−x(SiMg3)xN4:Eu2+ Phosphors

In this study, a series of Sr(LiAl₃)_1?x(SiMg₃)_xN₄:Eu²⁺ (SLA‐SSM) phosphors were synthesized by a solid‐solution process. The emission peak maxima of SLA‐SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. ⁷Li solid‐state NMR spectroscopy was utilized to distinguish between the Li(1)N₄ and Li(2)N₄ tetrahedra in SLA‐SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature‐dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X‐ray absorption near‐edge structure studies reveal that the Eu²⁺ concentration in SLA‐SSM is much higher than that in in SrLiAl₃N₄:Eu²⁺ and SrSiMg₃N₄:Eu²⁺ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.     

An arsenate with the α‐CrPO4 structure type,NaCa1–xNi3–2xAl2x(AsO4)3 (x = 0.23): crystal structure,charge‐distribution and bond‐valence‐sum analyses

Since the discovery of electrochemically active LiFePO₄, materials with tunnel and layered structures built up of transition metals and polyanions have become the subject of much research. A new quaternary arsenate, sodium calcium trinickel aluminium triarsenate, NaCa_1–x Ni_3–2x Al_2x (AsO₄)₃ (x = 0.23), was synthesized using the flux method in air at 1023 K and its crystal structure was determined from single‐crystal X‐ray diffraction (XRD) data. This material was also characterized by qualitative energy‐dispersive X‐ray spectroscopy (EDS) analysis and IR spectroscopy. The crystal structure belongs to the α‐CrPO₄ type with the space group Imma . The structure is described as a three‐dimensional framework built up of corner‐edge‐sharing NiO₆, (Ni,Al)O₆ and AsO₄ polyhedra, with channels running along the [100] and [010] directions, in which the sodium and calcium cations are located. The proposed structural model has been validated by bond‐valence‐sum (BVS) and charge‐distribution (CHARDI) tools. The sodium ionic conduction pathways in the anionic framework were investigated by means of the bond‐valence site energy (BVSE) model, which predicted that the studied material will probably be a very poor Na⁺ ion conductor (bond‐valence activation energy ∼7 eV).     

Origin and Location of Electrons and Protons during the Formation of Intermetalloid Clusters [Sm@Ga3−xH3−2xBi10+x]3− (x=0, 1)

Reaction of [GaBi₃]^2? with [Sm(C₅Me₄H)₃] yielded the first protonated ternary intermetalloid clusters [Sm@Ga_3?xH_3?2xBi_10+x]^3? ( 1 ; x=0,1). The presence of the Ga? H bonds and the transfer of electrons and protons during the formation of 1 were elucidated by a combination of experimental and quantum chemical methods, thereby rationalizing the role of the solvent ethane‐1,2‐diamine as a Brønsted acid. As an organic by‐product, we observed the previously unknown octamethylfulvene ( 2 ) upon C? C coupling of (C₅Me₄H)^?.     

Darstellung von μ-Schwefeldisulfoniumsalzen [(CH3)2S?Sx?S(CH3)2]2+2A− (x = 1–3, A− = AsF6−, SbF6−, SbCl6−). Über die Analogie im Reaktionsverhalten zwischen Sulfanen und Sulfoniumsalzen

Preparation of μ-Sulfurdisulfonium Salts [(CH₃)₂S? S_x? S(CH₃)₂]²⁺2A^? (x = 1–3, A^? = AsF₆^?, SbF₆^?, SbCl₆^?). On the Analogy of the Reactivity of Sulfanes and Sulfonium Salts The preparation of the μ-sulfurdisulfonium salts [(CH₃)₂S? S_x? S(CH₃)₂]²⁺(A^?)₂ with x = 1–3 and A^? = AsF₆^?, SbF₆^?, SbCl₆^? is reported. The salts are formed by reaction of (CH₃)₂SH⁺A^? and (CH₃)₂SSH⁺A^? with SCl₂ and S₂Cl₂, resp. They are characterized by vibrational spectroscopic measurements. [(CH₃)₂S? S₂? S(CH₃)₂]²⁺(SbF₆^?)₂ crystallizes in the space group C2/c with a = 1 884.5(7) pm, b = 1 302.8(5) pm, c = 1 477.2(5) pm, β = 98.62(3)° und Z = 8.     

Crystallographic report: (η5‐C5Me5)Fe(CO)2(BOCH2CH2CH2O): an organoiron complex containing the (trimethyleneglycolato)boryl ligand

The structure of the pentamethylcyclopentadienyliron boryl complex (η⁵‐C₅Me₅)Fe(CO)₂B(tmg) (tmg = trimethylene glycolato, ? OCH₂CH₂CH₂O? ), reveals a planar three‐coordinate boryl ligand and an Fe? B distance significantly in excess of that reported for related catecholboryl complexes. Copyright © 2005 John Wiley & Sons, Ltd.     

Structural Variations in the Solid‐Solution Series LnxCa2−xAl[Al1+xSi1−xO7] with 0 ≤ x ≤ 1 and Ln = La,Eu, Er

Gehlenite, Ca₂Al[AlSiO₇], has melilite‐type structure with space group . It contains two topologically distinct positions coordinated tetrahedrally by oxygen. One is completely occupied by Al³⁺, whereas the other one contains Al³⁺ and Si⁴⁺. Normally, the Al³⁺ molar fraction in the second tetrahedrally coordinated position does not exceed x_Al = 0.5, i.e. the so‐called Loewenstein‐rule is obeyed. In this contribution the structural variations in the melilite‐type compounds of the compositions La_xCa_2?xAl[Al_1+xSi_1?xO₇], Eu_xCa_2?xAl[Al_1+xSi_1?xO₇] and Er_xCa_2?xAl[Al_1+xSi_1?xO₇] are discussed. All members of the solid solution except the end‐members violate Loewenstein's rule. Rietveld refinements against X‐ray powder diffraction patterns confirm that the compounds have space group , without changes in the Wyckoff‐positions of the ions compared to gehlenite.     

Darstellung und spektroskopische Charakterisierung der Persulfoniumsalze (CH3)(CF3)SF3+SbF6− und (CH3)(CF3)2SF2+SbF6− und Kristallstruktur von CF3SF2+SbF6−

Preparation and Spectroscopic Characterization of the Persulfonium Salts (CH₃)(CF₃)SF₃⁺SbF₆^? and (CH₃)(CF₃)₂SF₂⁺SbF₆^? and Crystal Structure of CF₃SF₂⁺SbF₆^? [1] . The preparation of the persulfonium salts (CH₃)(CF₃)SF₃⁺SbF₆^? and (CH₃)(CF₃)₂SF₂⁺SbF₆^? by methylation of the sulfuranes CF₃SF₃ and (CF₃)₂SF₂ with CH₃OSO⁺SbF₆^? in liquid SO₂ is reported. The thermolabile compounds are characterized by IR, Raman, ¹H, ¹³C, and ¹⁹F NMR spectroscopy. CF₃SF₂⁺SbF₆^? crystallizes in the space group C2/c with a=16.889(8) Å, b=7.261(4) Å, c=13.416(7) Å, β=91.08° with 8 formula units per unit cell at 167 K. Cations and anions are connected via short SF contacts forming a Ψ-octahedral surrounding of the central S atom which is in close analogy to the already known CF₃SF₂⁺AsF₆^?.