Sr5Ge2N6 – A Nitridogermanate with Edge‐sharing Double Tetrahedra

The new nitridogermanate Sr₅Ge₂N₆ was obtained as a coarsely crystalline product by Na‐flux technique employing a reaction of Sr, Na, NaN₃ and GeO₂ in weld shut tantalum‐tubes at temperatures up to 760 °C. The crystal structure was determined by single‐crystal X‐ray methods: (Sr₅Ge₂N₆, space group C2/c (no. 15), a = 1040.8(2), b = 652.08(13), c = 1356.5(3) pm, β = 100.29(3)°, V = 905.8(3)·10⁶ pm³, Z = 4, 1240 observed reflections, 61 parameters, R1 = 0.031). In the solid, there are edge‐sharing [Ge₂N₆]¹⁰⁻ double tetrahedra surrounded by Sr²⁺ ions. Sr₅Ge₂N₆ was found to be isotypic with Ca₅Si₂N₆.     

Li4Ca3Si2N6 and Li4Sr3Si2N6 – Quaternary Lithium Nitridosilicates with Isolated [Si2N6]10– Ions

The isotypic nitridosilicates Li₄Ca₃Si₂N₆ and Li₄Sr₃Si₂N₆ were synthesized by reaction of strontium or calcium with Si(NH)₂ and additional excess of Li₃N in weld shut tantalum ampoules. The crystal structure, which has been solved by single‐crystal X‐ray diffraction (Li₄Sr₃Si₂N₆: C2/m, Z = 2, a = 6.1268(12), b = 9.6866(19), c = 6.2200(12) Å, β = 90.24(3)°, wR₂ = 0.0903) is made up from isolated [Si₂N₆]^10– ions and is isotypic to Li₄Sr₃Ge₂N₆. The bonding angels and distances within the edge‐sharing [Si₂N₆]^10– double‐tetrahedra are strongly dependent on the lewis acidity of the counterions. This finding is discussed in relation to the compounds Ca₅Si₂N₆ and Ba₅Si₂N₆, which also exhibit isolated [Si₂N₆]^10– ions.     

Fe and Cr K‐edges EXAFS Study of Double Perovskite (Sr2‐xCax)FeMoO6 (0 ≤ x ≤ 2.0) and Sr2CrMO6 (M = Mo,W) Systems

The local structure of the double perovskite (Sr_2‐xCa_x)FeMoO₆ (0 ≤ × ≤ 2.0) and Sr₂CrMO₆ (M = Mo, W) systems have been probed by extended X‐ray absorption fine structure (EXAFS) spectroscopy at the Fe and Cr K‐edges. We found Fe‐O (ave) distance apparently decreases from 1.999 Å (x = 0) to 1.991 Å (x = 1.0) in (Sr_2‐xCa_x)FeMoO₆ (tetragonal structure). When x is increased further from 1.5 to 2.0, the Fe‐O bond distance decreased from 2.034 Å to 2.012 Å (monoclinic structure). In addition, Cr‐O, Sr‐Cr, and Cr‐Mo bond distances in Sr₂CrWO₆ are all slightly larger than the bond distances of Sr₂CrMoO₆, which is due to the ionic radius of the W⁵⁺ (0.62 Å) which is larger than the ionic radius of Mo⁵⁺ (0.61 Å). The results are consistent with our XRD refinements data.     

Sr3ZnPtO6 and Sr3CdPtO6

The flux synthesis of single crystals of the isostructural compounds tristrontium zinc platinum hexaoxide, Sr₃ZnPtO₆, and tristrontium cadmium platinum hexaoxide, Sr₃CdPtO₆, is reported. The compounds adopt the pseudo‐one‐dimensional rhombohedral K₄CdCl₆ structure type, and feature chains of face‐shared distorted ZnO₆ or CdO₆ trigonal prisms and PtO₆ octahedra, surrounded by columns of Sr²⁺ ions. All transition metals are located on the threefold axis of symmetry, while the Sr²⁺ cations lie on twofold axes.     

Li4Sr2[Cr2N6]: Ein Hexanitridodichromat(V)

Li₄Sr₂[Cr₂N₆]: A Hexanitridodichromate(V) The quaternary hexanitridodichromate(V) Li₄Sr₂[Cr₂N₆] was obtained by reaction of the metals with flowing nitrogen at 900 °C as black‐shining crystals with a platy habit. The crystal structure was determined by X‐ray single crystal methods (orthorhombic, Pbca; a = 914.0 pm, b = 735.4 pm, c = 1053.6 pm; Z = 4). The compound contains isolated complex anions [Cr₂N₆]^8— consisting of two tetrahedra CrN₄ sharing a common edge. The distance Cr—Cr in the complex anion is 249.7 pm. The analysis of the Electron Localization Function (ELF) indicates bonding interactions Cr—Cr. Strontium is in a sixfold (distorted octahedral), Lithium in a distorted tetrahedral ([3+1]) coordination by nitrogen. According to measurements of the magnetic susceptibility the compound is diamagnetic.     

Reinvestigation of Sr2[Cu(OH)6]

During an investigation of the SrO–CuO–P₂O₅–H₂O system, single crystals of distrontium hexahydroxidocuprate(II), Sr₂[Cu(OH)₆], were obtained by the hydrothermal method. The blue prismatic crystals of Sr₂[Cu(OH)₆] adopt the same structure type as Ba₂[Cu(OH)₆], Sr₂[Zn(OH)₆] and Ba₂[Zn(OH)₆]. The Cu atoms, located at (0, 0, ) (site symmetry ), form mutually isolated and highly elongated Cu(OH)₆ octahedra, which are interconnected to slightly distorted Sr(OH)₆ trigonal prisms, forming a layered structure. The location of H atoms from difference Fourier maps and their refinement allowed the precise determination of a three‐dimensional hydrogen‐bonding network in which all hydroxide O atoms are involved. In addition, the hydrogen‐bonding topologies in Sr₂[Cu(OH)₆] and other similar hexahydroxidometallates with the general formulae M1[M2(OH)₆], M1₂[M2(OH)₆] and M1₃[M2(OH)₆] were analysed in detail.     

Sr2(OLi2Sr4)[CrN4]2, ein Nitridochromat(VI)‐Oxid mit Sauerstoff in tetragonal‐bipyramidaler Koordination durch Lithium und Strontium

Sr₂(OLi₂Sr₄)[CrN₄]₂, a Nitridochromate(VI)‐Oxide with Oxygen in Tetragonal‐Bipyramidal Coordination by Lithium and Strontium Green gleaming crystals of Sr₂(OLi₂Sr₄)[CrN₄]₂ were prepared by reaction of Li, Sr and CrN/Cr₂N (approximate 1 : 1 mixture) with flowing nitrogen at 900 °C (molar overall composition Li : Sr : Cr = 6 : 1 : ∼3). The oxygen content results from a leak in the gas supply. The crystal structure was determined by single crystal methods (triclinic; P1; a = 615.87(9) pm, b = 682.50(10) pm, c = 754.30(8) pm, α = 82.302(14)°, β = 75.197(10)°, γ = 70.133(13)°; Z = 1) and contains distorted tetragonal bipyramids (OLi₂Sr₄)⁸⁺ and [Cr^VIN₄]^6–‐tetrahedra besides Sr²⁺.     

K2SrNb6Cl18, dipotassium strontium hexaniobium octadecachloride

The structure of dipotassium strontium hexaniobium octadeca­chloride is based on [Nb₆Clⁱ₁₂Cl^a₆]^4? units (i and a denote `inner' and `outer' ligands, respectively), which have crystallographically imposed symmetry, linked together by K⁺ and Sr²⁺ cations. The K⁺ cation occupies a tetrahedral site in the face‐centered cubic lattice of cluster units, and is bonded to 12 Cl ligands. The Sr atom is located in an octahedral site and is bonded to six outer Cl ligands.     

Sr6Cd2Sb6O7S10: Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups

A new nonlinear optical (NLO) oxysulfide, Sr₆Cd₂Sb₆O₇S₁₀, which contains the functional groups [SbO_xS_5?x]^7? (x=0, 1) with a 5s² electron configuration, is synthesized by a solid‐state reaction. This compound displays a phase‐matchable second harmonic generation (SHG) response four times stronger than AgGaS₂ (AGS) under laser irradiation at 2.09 μm. Single‐crystal‐based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS₄]^7? and [SbS₅]^7? pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS₄]^7? units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns² electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.     

A Thermodynamic Study Between 18-Crown-6 with Mg2+, Ca2+, Sr2+and Ba2+ Cations in Water–Methanol and Water–Ethanol Binary Mixtures Using The Conductometric Method

The complexation reactions between Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations with the macrocyclic ligand, 18-Crown-6 (l8C6) in water–methanol (MeOH) binary systems as well as the complexation reactions between Ca²⁺ and Sr²⁺ cations with 18C6 in water–ethanol (EtOH) binary mixtures have been studied at different temperatures using conductometric method. The conductance data show that the stoichiometry of all the complexes is 1:1. It was found that the stability of 18C6 complexes with Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ cations is sensitive to solvent composition and in all cases, a non-linear behaviour was observed for the variation of log K _f of the complexes versus the composition of the mixed solvents. In some cases, the stability order is changed with changing the composition of the mixed solvents. The selectivity order of 18C6 for the metal cations in pure methanol is: Ba²⁺ > Sr²⁺ > Ca²⁺ > Mg²⁺. The values of thermodynamic parameters (Δ H _c ° and Δ S _c °) for formation of 18C6–Mg²⁺, 18C6–Ca²⁺, 18C6–Sr²⁺ and 18C6–Ba²⁺complexes were obtained from temperature dependence of the stability constants. The obtained results show that the values of (Δ H _c ° and Δ S _c °) for formation of these complexes are quite sensitive to the nature and composition of the mixed solvent, but they do not vary monotonically with the solvent composition.This revised version was published online in July 2005 with a corrected issue number.     

Remarkable Oxygen‐Evolution Activity of a Perovskite Oxide from the Ca2−xSrxFe2O6−δ Series

Herein in we report the unprecedented catalytic activity of an iron‐based oxygen‐deficient perovskite for the oxygen‐evolution reaction (OER). The systematic trends in OER activity as a function of composition, defect‐order, and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca₂Fe₂O_6?δ<CaSrFe₂O_6?δ<Sr₂Fe₂O_6?δ. Sr₂Fe₂O_6?δ also has the highest electrical conductivity and a unique type of defect‐order. In conventional experiments using glassy carbon electrode, Sr₂Fe₂O_6?δ shows better OER activity than the current state of the art catalysts, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ and RuO₂. It also offers a high intrinsic electrical conductivity, which allows it to act as a catalyst without the need for glassy carbon electrode or carbon powder. Pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.     

Sr3(BS3)2 und Sr3(B3S6)2: Zwei neue nicht‐oxidische Chalkogenoborate mit trigonal‐planar koordiniertem Bor

Sr₃(BS₃)₂ and Sr₃(B₃S₆)₂: Two Novel Non‐oxidic Chalcogenoborates with Boron in a Trigonal‐Planar Coordination The thioborates Sr₃(BS₃)₂ and Sr₃(B₃S₆)₂ were prepared from strontium sulfide, amorphous boron and sulfur in solid state reactions at a temperature of 1123 K. In a systematic study on the structural cation influence on this type of ternary compounds, the crystal structures were determined by single crystal X‐ray diffraction. Sr₃(BS₃)₂ crystallizes in the monoclinic spacegroup C2/c (No. 15) with a = 10.187(4) Å, b = 6.610(2) Å, c = 15.411(7) Å, β = 102.24(3)° and Z = 4. The crystal structure of Sr₃(B₃S₆)₂ is trigonal, spacegroup R3¯ (Nr. 148), with a = 8.605(1) Å, c = 21.542(4) Å and Z = 3. Sr₃(BS₃)₂ contains isolated [BS₃]^3— anions with boron in a trigonal‐planar coordination. The strontium cations are found between the layers of orthothioborate anions. Sr₃(B₃S₆)₂ consists of cyclic [B₃S₆]^3— anions and strontium cations, respectively.     

Sr2Cu2TeO6Br2: honeycomb layers of copper(II) ions

Single crystals of distrontium(II) dicopper(II) tellurium(VI) hexa­oxide dibromide, Sr₂Cu₂TeO₆Br₂, were synthesized via solid state/gas phase reactions in sealed evacuated silica tubes. The building units are irregular SrO₄Br₃ polyhedra (a new type of coordination polyhedron around Sr^II), CuO₅ square pyramids and TeO₆ octa­hedra. The CuO₅ square pyramids and the TeO₆ octa­hedra together form layers in the bc plane bridged by Sr atoms. The Cu atoms are arranged to form puckered honeycomb layers. The Te atom lies on an inversion centre.     

The structural,electronic, and magnetic properties of the stoichiometric (001) surface of double perovskite Sr2FeMoO6

The structural, electronic, and magnetic properties of the stoichiometric (001) surface of double perovskite Sr₂FeMoO₆ have been studied by using a 10‐layer FeMoO₄ and SrO terminated (001)‐oriented slab model and the first‐principles projector augmented wave potential within the generalized gradient approximation as well as taking into account the on‐site Coulomb repulsive (U = 2.0 eV for Fe and 1.0 eV for Mo). An outwards relaxation is observed for several layers near surface, and the accompanying layer rumpling has a decrease tend from surface layer to inner layer. Along Fe–O–Mo–O–Fe or Mo–O–Fe–O–Mo chains, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. In FeO₆ or MoO₆ octahedra, the two axial TM?O bonds are not equal, and especially, the surface dangling bond makes the remaining one axial TM?O bond slightly shorter than four equally equatorial TM?O bonds. The half‐metallic nature and a complete (100%) spin polarization character ensure the FeMoO₄ and SrO terminated (001)‐oriented slab of double perovskite Sr₂FeMoO₆ a potential application in spintronics devices. The Fe⁺³ and Mo⁺⁵ ions are still in the (3d⁵, S = 5/2) and (4d¹, S = 1/2) states with positive and negative magnetic moments respectively and thus antiferromagnetic coupling via oxygen between them. There is no direct interaction between two nearest Fe–Fe or Mo–Mo pairs, whereas the hybridizations between Fe 3d and 4s, O 2s and 2p, as well as Mo 4d, 5s and 5p orbitals are fairly significant. Copyright © 2016 John Wiley & Sons, Ltd.     

[CoN2]/[CN2]‐Substitution in a Crystalline Phase with Composition Close to Sr6[CoN2]2[CN2]

Sr₆[CoN₂]₂[CN₂] was prepared from Sr₂N, carbon, cobalt, and NaN₃ as nitrogen source. The crystal structure (I4/mmm (no. 139), a = 383.55(10) pm, c = 1237.8(4) pm) represents a Na₂[HgO₂] type arrangement with both linear [Co^IN₂]^5– and smaller [CN₂]^2– ions mutually occupying the [HgO₂] position.     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.     

Über den Einfluß von A und B auf die Bindungsverhältnisse in geordneten Perowskiten A2BB′O6. Die Systeme Ba2−xSrxCdUO6 und Ba2−xSrxZnUO6

On the Influence of A and B on the Bonding in Ordered Perovskites A₂BB′O₆. The Systems Ba_2?xSr_xCdUO₆ and Ba_2?xSr_xZnUO₆ In the systems Ba_2?xSr_xBUO₆ for B = Cd a complete substitution of Ba²⁺ by Sr²⁺ is observed, whereas with B = Zn the phase boundary is near x ? 1.25. By measurement of charge transfer and vibrational spectra the influence of the A and B nature on the properties is shown. By comparison with the corresponding Mg- and Ca-perovskites the influence of the electronic configuration (d⁰ or d¹⁰) is studied as well.     

Poly­[strontium(II)‐μ2‐aqua‐μ5‐4‐carboxyl­ato­phenoxy­acetato]

In the title three‐dimensional coordination polymer, [Sr(4‐CPOA)(H₂O)]_n (where 4‐CPOA²⁻ is the 4‐carboxylatophenoxy­acetate dianion, C₉H₆O₅), each Sr^II atom displays a bicapped triangular prismatic configuration, defined by five carboxyl and one ether O atom from five different 4‐CPOA²⁻ ligands, as well as two water mol­ecules. The Sr^II atoms are covalently linked by 4‐CPOA²⁻ ligands and water mol­ecules, giving rise to a three‐dimensional open framework. In previously studied polymers of this type, the 4‐CPOA²⁻ ligand shows a variety of binding modes to metal ions, from mono‐ to pentadentate. In the present Sr^II complex, a novel hexadentate bridging mode is observed.     

Novel tantalum phosphate Na13Sr2Ta2(PO4)9: synthesis,crystal structure,DFT calculations and Dy3+‐activated fluorescence performance

A new tantalum phosphate, tridecasodium distrontium ditantalum nonaphosphate, Na₁₃Sr₂Ta₂(PO₄)₉, was prepared using the high‐temperature flux method. The structure can be described as a three‐dimensional open framework containing isolated [Ta^V₂(PO₄)₉]¹⁷⁻ units that are interlocked by Na and Sr ions. Band structure studies by the first‐principles method revealed that Na₁₃Sr₂Ta₂(PO₄)₉ is an insulator with an indirect band gap of 4.78 eV, which makes it suitable as a luminescent host matrix. A series of solid solutions, i.e. Na₁₃Sr_2–xTa₂(PO₄)₉:xDy³⁺ (x = 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12 and 0.14), were prepared and their photoluminescence properties studied. Under 350 nm light excitation, these emit two typical emissions of the Dy³⁺ ion, i.e. the ⁴F_9/2→⁶H_15/2 transition centred at 476 nm and the ⁴F_9/2→⁶H_13/2 transition centred at 570 nm.     

Eu3+掺杂双钙钛矿Sr2CaMoO6橙红色荧光粉的结构特征及其发光性能

采用EDTA-柠檬酸联合配位法制备一系列组成的(Sr1-xEux)2CaMoO6橙红色荧光粉。通过X射线衍射、拉曼光谱、扫描电镜及荧光光谱研究不同Eu3+离子掺杂浓度下Sr2CaMoO6∶Eu3+荧光粉的晶体结构、掺杂位置、形貌及其光致发光性能。Rietveld全谱拟合结果表明:掺杂后样品为(Ca/Mo)O6八面体少量倾斜的空间群为P21/n的正交双钙钛矿结构,随着Eu3+离子共掺杂浓度的增加,样品的晶胞体积减小;Eu3+离子取代八面体间隙的Sr2+位置致使双钙钛矿的T2g(1)拉曼振动模发生蓝移;在近紫外区宽而强电荷迁移带和蓝光激发下,该荧光粉分别发射以Eu3+离子5D0-7F1磁偶极跃迁为主的橙光和以5D0-7F2电偶极跃迁为主的红光,组成为(Sr0.98Eu0.02)2CaMoO6的荧光粉具有最强的橙红光发射强度,是一种潜在的适用于近紫外LED芯片的光转换红光材料。