半水榴石型化合物Sr_6Sb_4M_3O_(14)(OH)_(10)(M=Co,Mn)的合成、结构与性质

在强碱性水热条件下合成了两种新化合物Sr6Sb4Co3O14(OH)10(SSC)与Sr6Sb4Mn3O14(OH)10(SSM).采用粉末X射线衍射数据,通过Rietveld方法进行了结构分析,讨论了金属离子的拓扑结构.两种化合物均为石榴石-水榴石相关结构,空间群I43d,晶胞参数a分别为1.30634(2)nm(SSC)和1.31367(1)nm(SSM).结构中,SbO6八面体与MO4(M=Co,Mn)四面体共顶点连接,Sb5+-M2+(M=Co,Mn)离子表现为ctn即C3N4型的拓扑结构.拓扑结构中,Sb5+为三连接,过渡金属离子M2+(M=Co,Mn)为四连接.Sb5+离子的拓扑结构为体心立方,而M2+(M=Co,Mn)分布呈类风扇状,相互连接形成thp型拓扑结构(即Th3P4中Th原子之间连接关系).过渡金属离子的分布与化合物表现出的磁性质密切相关,Co2+(Mn2+)间存在反铁磁相互作用.Sr6Sb4Co3O14(OH)10在低温下表现出反铁磁倾斜有序.Sr6Sb4Co3O14(OH)10和Sr6Sb4Mn3O14(OH)10在高温下发生分解,产物主相为双钙钛矿Sr2(Sb,M)2O6(M=Co,Mn).     

Structural chemistry of A3CuBO6 (A = Ca, Sr; B = Mn, Ru, Ir) as a function of temperature

Variable temperature X-ray and neutron powder diffraction techniques have been used to identify structural phase transitions in Cu-rich A(3)A'BO(6) phases. A transition from monoclinic to rhombohedral symmetry was observed by X-ray diffraction between 700 and 500 K in Sr(3)Cu(1-x)M(x)IrO(6) (M = Ni, Zn; 0 < or = x < or = 0.5). The temperature of the phase change decreased in a linear manner with Cu-content and was essentially independent of the nature of M. Ca(3.1)Cu(0.9)MnO(6) was shown to pass from a rhombohedral phase to a triclinic phase on cooling below 290 K; the structure of the triclinic phase was refined against neutron diffraction data collected at 2 K. Ca(3.1)Cu(0.9)RuO(6) undergoes a transition between a disordered rhombohedral phase and an ordered monoclinic phase when cooled below 623 K. Neutron diffraction has been used to determine the structure as a function of temperature in the range 523 < or =T/K < or = 723 and hence to determine an order parameter for the low temperature phase; the second-order transition is shown to be incomplete 100 K below the critical temperature.     

Die Clusterazide M2[Nb6Cl12(N3)6]·(H2O)4—x (M = Ca,Sr, Ba)

The Cluster Azides M₂[Nb₆Cl₁₂(N₃)₆]·(H₂O)_4—x (M = Ca, Sr, Ba) The isotypic cluster compounds M₂[Nb₆Cl₁₂(N₃)₆] · (H₂O)_4—x (M = Ca (1) , M = Sr (2) and M = Ba (3) ) have been synthesized by the reaction of an aequeous solution of Nb₆Cl₁₄ with M(N₃)₂. 1 , 2 and 3 crystallize in the space group Fd3¯ (No. 227) with the lattice constants a = 1990.03(23), 2015.60(12) and 2043, 64(11) pm, respectively. All compounds contain isolated 16e— clusters whose terminal positions are all occupied by orientationally disordered azide ligands.     

Triorganoantimon- und Triorganobismutdisulfonate Kristall- und Molekülstrukturen von (C6H5)3M(O3SC6H5)2 (M = Sb,Bi)

Triorganoantimony and Triorganobismuth Disulfonates. Crystal and Molecular Structure of (C₆H₅)₃M(O₃SC₆H₅)₂(M = Sb, Bi) Triorganoantimony disulfonates R₃Sb(O₃SR′)₂ [R = CH₃ = Me, C₆H₅ = Ph; R′ = Me, CH₂CH₂OH, Ph, 4-CH₃C₆H₄. R = Ph; R′ = 2,4-(NO₂)₂C₆H₃], Me₃Sb(O₃SCF₃)₂ · 2 H₂O and triphenylbismuth disulfonates Ph₃Bi(O₃SR′)₂ [R = Me, CF₃, CH₂CH₂OH, Ph, 4-CH₃C₆H₄, 2,4-(NO₂)₂C₆H₃] have been prepared by reaction of Me₃Sb(OH)₂, (Ph₃SbO)₂, and Ph₃BiCO₃, respectively, with the appropriate sulfonic acids. From vibrational data an ionic structure is inferred for Me₃Sb(O₃SCF₃)₂ · 2 H₂O and Me₃Sb(O₃SCH₂CH₂OH)₂, and a covalent structure for the other compounds with a penta-coordinated central atom with trigonal bipyramidal surrounding (Ph or Me in equatorial, unidentate sulfonate ligands in apical positions). Ph₃M(O₃SPh)₂ (M = Sb, Bi) crystallize monoclinic [space group P2₁/c; M = Sb/Bi: a = 1 611.5(8)/1 557.4(9), b = 987.5(6)/1 072,5(8), c = 1 859.9(9)/1 696.5(9) pm, β = 105.71(5)/96.62(5)°; Z = 4; d(calc.) 1.556/1.781 Mg · m^?3; V_cell = 2 849.2 · 10⁶/2 814.8 · 10⁶ pm³; structure determination from 3 438/3 078 independent reflexions (I ≥ 3σ(I)), R(unweighted) = 0.030/0.029]. M is bonding to three Ph groups in the equational plane [mean distances Sb/Bi? C:210.1(4)/219.1(7) pm] and two sulfonate ligands with O in apical positions [distances Sb? O: 210.6(3), 212.8(2); Bi? O: 227.6(5), 228.0(4) pm]. Weak interaction of M with a second O atom of one sulfonate ligand is inferred from a rather short M? O contact distance [Sb? O: 327.4(4), Bi? O: 312.9(5) pm], and from the distortion of equatorial angles [C? Sb? C: 128.4(2), 119.2(2), 112.2(2); C? Bi? C: 135.9(3), 117.8(3), 106.3(3)°]     

Thermally induced A'-A site exchange in novel layered perovskites Ag2[Ca1.5M3O10] (M = Nb,Ta)

We have synthesized and characterized new layered perovskites Ag2[A1.5M3O10] (A = Ca, M = Nb, Ta), from their lithium analogues, by soft-chemical ion exchange. These oxides show topotactic irreversible thermally induced A'-A site exchange, resulting in Ag1.1Ca0.9[Ca0.6Ag0.9M3O10], conferred from our high-temperature X-ray and ionic conductivity studies. The latter phases are the first compounds where Ag+ ions reside in both A' and A sites in layered perovskites. The absence of similar phase transition for A = Sr suggests that these transitions strongly depend on the size, charge, and the coordination preference of A' and A cations. This result provides a new synthetic tool for modifying the occupation of the 12-coordinate A site of layered perovskites using soft chemical routes.     

A study of the reaction NO3 + NO2 + M → N2O5 + M(M = N2, O2)

The gas-phase reaction of the NO₃ radical with NO₂ was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10^?13 cm³ molecule^?1 s^?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N₂ and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O₂. These data show that the third-body efficiencies of N₂ and O₂ are identical, within the error limits, and that previous evaluations for M = N₂ are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO₃ radical with methanol, ethanol, and propan-2-ol of ?6 × 10^?16, ?9 × 10^?16, and ?2.3 × 10^?15 cm³ molecule^?1 s^?1, respectively, at 298 ± 2 K.     

2D-3D transformation of layered perovskites through metathesis: synthesis of new quadruple perovskites A2La2CuTi3O12 (A = Sr, Ca)

We describe the synthesis of two new quadruple perovskites, Sr(2)La(2)CuTi(3)O(12) (I) and Ca(2)La(2)CuTi(3)O(12) (II), by solid-state metathesis reaction between K(2)La(2)Ti(3)O(10) and A(2)CuO(2)Cl(2) (A = Sr, Ca). I is formed at 920 degrees C/12 h, and II, at 750 degrees C/24 h. Both the oxides crystallize in a tetragonal (P4/mmm) quadruple perovskite structure (a = 3.9098(2) and c = 15.794(1) A for I; a = 3.8729(5) and c = 15.689(2) A for II). We have determined the structures of I and II by Rietveld refinement of powder XRD data. The structure consists of perovskite-like octahedral CuO(4/2)O(2/2) sheets alternating with triple octahedral Ti(3)O(18/2) sheets along the c-direction. The refinement shows La/A disorder but no Cu/Ti disorder in the structure. The new cuprates show low magnetization (0.0065 micro(B) for I and 0.0033 micro(B) for II) suggesting that the Cu(II) spins are in an antiferromagnetically ordered state. Both I and II transform at high temperatures to 3D perovskites where La/Sr and Cu/Ti are disordered, suggesting that I and II are metastable phases having been formed in the low-temperature metathesis reaction. Interestingly, the reaction between K(2)La(2)Ti(3)O(10) and Ca(2)CuO(2)Cl(2) follows a different route at 650 degrees C, K(2)La(2)Ti(3)O(10) + Ca(2)CuO(2)Cl(2) --> CaLa(2)Ti(3)O(10) + CaCuO(2) + 2KCl, revealing multiple reaction pathways for metathesis reactions.     

Synthesis and crystal structure of the alkaline-earth thallates MnTl2O3+n (M=Ca,Sr)

The phases present in the Tl₂O₃–MO system, where M=Ca and Sr, have been synthesised and characterised using powder neutron diffraction data. The structures of the phases known to exist in the Ca_nTl₂O_3+n system with n=1, 1.5, 2 and 3 have been refined and the oxycarbonate phase with composition Ca₄Tl₂O₆CO₃ has been identified. In the Sr_nTl₂O_3+n system, the structures of the phases with n=1, 2 and 3 have also been refined. The M_nTl₂O_3+n phases with M=Ca and Sr and n=1–3 are related to the lillianite structure while the n=4 compound is an oxycarbonate that has been found to crystallise in I4/mmm symmetry for M=Ca and in three different modifications with space groups P4/mmm, I4/mmm and Pmmm for M=Sr, depending on the ordering of the carbonate groups. The relationships between these structures are discussed and comparisons are made to the previously published structures determined from X-ray powder diffraction data.     

V2O5/MO-Al2O3（M = Mg，Ca，Sr，Ba）催化剂用于正丁烷催化氧化脱氢反应

采用浸渍法制备了不同V2O5担载量的V2O5/MO-Al2O3(M = Mg, Ca, Sr, Ba)催化剂,钒物种的前驱体为偏钒酸铵.对制备的催化剂进行了一系列表征,并对催化剂上正丁烷选择性氧化脱氢制取丁烯进行了反应研究.表征结果(包括比表面积、X射线衍射、傅里叶红外光谱、氢气程序升温还原和拉曼光谱)显示,不同碱土金属元素掺杂的催化剂显示不同的钒价态信息和催化性能.其中掺杂Ca, Sr, Ba的催化剂,正钒酸盐相很难被还原,因此催化剂的氧化还原循环难以建立,导致以上三种催化剂在正丁烷氧化脱氢反应中活性较低.然而, Mg掺杂的催化剂却显示出较高的催化活性和选择性.实验结果表明：在Mg掺杂的载体上担载5% V2O5的催化剂上600°C时可获得高达30.3%的正丁烷转化率和64.3%的烯烃总选择性.这与V2O5担载量为5%时,在获得高度分散的钒氧化合物物种时可使MgO晶相稳定存在密切相关.     

MO-RE2O3-B2O3(M=Mg,Ca,Sr,Ba;RE=La,Eu,Gd)玻璃的发光性质

在空气中采用高温固相反应方法合成的17MO－（8-x-y)-75B2O3-xGd2O3(MLBEG,M-Mg,Ca,Sr,Ba)玻璃，在紫外光（λex=350nm)激发下发射蓝光和红光，在绿色光（λex=532nm)激发下发射红光，电子自旋共振谱研究表明玻璃体系中有Eu^2 离子存在，蓝色区的宽带发射是Eu^2 离子的5d-4f跃迁发射：红色区的窄带发射是Eu^3 离子的5Do-7FJ(J=1,2,3,4)跃迁发射，发现玻璃中的碱土金属离子对Eu^3 /Eu^2 离子的比例有很大影响，选择不同的碱土金属离子可以调节玻璃蓝色光和红色光的相对发射强度，MLBEG玻璃的发光性质可用于转换太阳能，增强植物的光合作用。     

On the novel double perovskites A2Fe(Mn0.5W0.5)O6 (A= Ca,Sr, Ba). Structural evolution and magnetism from neutron diffraction data

New A₂Fe(Mn_0.5W_0.5)O₆ (A = Ca, Sr, Ba) double perovskite oxides have been prepared by ceramic techniques. X-ray diffraction (XRD) complemented with neutron powder diffraction (NPD) indicate a structural evolution from monoclinic (space group P2₁/n) for A = Ca to cubic (Fm-3m) for A = Sr and finally to hexagonal (P6₃/mmc) for A = Ba as the perovskite tolerance factor increases with the A²⁺ ionic size. The three oxides present different tilting schemes of the FeO₆ and (Mn,W)O₆ octahedra. NPD data also show evidence in all cases of a considerable anti-site disordering, involving the partial occupancy of Fe positions by Mn atoms, and vice-versa. Magnetic susceptibility data show magnetic transitions below 50 K characterized by a strong irreversibility between ZFC and FC susceptibility curves. The A = Ca perovskite shows a G-type magnetic structure, with weak ordered magnetic moments due to the mentioned antisite disordering. Interesting magnetostrictive effects are observed for the Sr perovskite below 10 K.     

三核过渡金属配合物〔M_3~ⅢO(OOCR)_6L_3〕 (M=Cr,Fe,Mn;R=CH_3,C_2H_5,CH_2NH_2;L=C_5H_5N,H_2O)的~1H NMR性质

采用１ＨＮＭＲ谱研究了通式为〔Ｍ３ⅢＯ（ＯＯＣＲ）６Ｌ３〕＋（Ｍ＝Ｃｒ,Ｆｅ,Ｍｎ;Ｒ＝ＣＨ３,Ｃ２Ｈ５,ＣＨ２ＮＨ２;Ｌ＝Ｃ５Ｈ５Ｎ,Ｈ２Ｏ）的一系列氧心三核过渡金属配合物,主要考察其１Ｈ化学位移随金属、配体、温度、溶剂等因素变化而变化的规律。结果表明,骨架金属对化学位移的影响最大,Ｍ３Ｏ中的３个金属离子间存在反铁磁交换相互作用。对Ｍｎ配合物中顺磁中心对化学位移和线宽的影响机制的研究表明,其１Ｈ各向同性位移主要由接触作用贡献     

Theoretical study of the structures of [M(18C6)](HFA)2 complexes (M = Ba,Sr, Pb,Cd, Mn; 18C6 = 18-crown-6; HFA = hexafluoroacetylacetonate anion)

The structures of the [M(18C6)]²⁺ cations (M = Ba, Sr, Pb, Cd, Mn) and their salts [M(18C6)](HFA)₂ and [M(18C6)](NO₃)₂ have been calculated by the density functional theory method (in the B3LYP/6-311++G** + LanL2Dz approximation). Upon geometry optimization, the gas-phase structures of compounds of different composition have been calculated; for them, the strength of binding of the central cation to the crown ether (18C6) and the degree of structural similarity have been evaluated. The structure of the [NH₄(18C6)]⁺ cation identified in a practical synthesis has also been considered. For metal cations acting as a central atom, NH ₄ ⁺ and [M(18C6)]²⁺ complex cations, as well as for intermediate and ultimate products [M(18C6)](NO₃)₂ and [M(18C6)](HFA)₂ (M = Ba, Sr, Pb, Cd, Mn), the electronic chemical potential and Pearson hardness, which enables the consideration of the propensity of various reagents to interact with each other in terms of the empirical HSAB principle (hard with hard and soft with soft), have been evaluated. Comparison of the estimates with the properties of the synthesized compounds with M = Ba, Sr, and Pb makes it possible to preliminarily verify the applicability of this principle to the systems under consideration and predict some properties of isostructural analogues important in the search for methods of synthesis of [M(18C6)](HFA)₂, where M = Cd and Mn. The possibility of establishing a correlation between the electron density of the system, stability, and hydrolytic activity of complexes has been shown.     

Hydrogen sites in A2BHy (A = Ca,Sr, Eu; B = Ir,Rh, Ru)

A geometric model has been applied to the A₂BH_y hydrides (deuterides), Eu₂IrD₅, Ca₂IrH₅, Sr₂IrD₅, Ca₂RhH₅, Sr₂RhH₅, Ca₂RuH₆, and Sr₂RuD₆, none of which can be synthesized directly by reaction of hydrogen (deuterium) gas with an A₂B compound. Hole radii and intersite distances were calculated for the two types of interstices in each compound. There are two very large cubical interstices per formula unit. These are coordinated by eight atoms of type A, but they must remain unoccupied in A₂BH_y with y = 5 (or 6), because of their proximity to the square pyramidal interstices, of which there are six per formula unit. The geometric model allows rationalization of the occupation of these pyramidal sites. Despite the very significant chemical differences between the compounds considered here and those for which the model was initially developed, the present results showed no inconsistency with geometric criteria requiring that occupied interstices in stable hydrides have minimum hole radii of 0.40 Å and minimum hydrogen-hydrogen distances of 2.10 Å. Published results indicate that the seemingly related compound Mg₂NiD₄ does not conform to these empirical rules, and this case is discussed.     

Crystal structures of AgAF6 (A = P, As, Sb, Nb, Ta) at ambient temperatures

Structures of AgAF₆ (A=Sb, Ta) have been determined by X-ray single crystal studies at ambient temperatures. AgSbF₆ crystallizes in space group Ia with a=979.85(4) pm, V=9.4076(12)×10⁸ pm³, z=8, and AgTaF₆ crystallizes in space group P4₂/mcm with a=499.49(4) pm, c=960.51(8) pm, V=2.3964(6)×10⁸ pm³, z=2. Only the crystal system and cell parameters were obtained for the isomorphic AgNbF₆; primitive tetragonal, a=497.80(10) pm, b=960.40(10) pm, V=2.3799(12)×10⁸ pm³, z=2. The results of the Raman spectroscopy of AgAF₆ support the obtained structures. The structures are discussed by comparing with that of AgPF₆ and AgAsF₆ which have recently been determined in a series of our study.     

Synthesis, crystal and electronic structures of the new quaternary phases A5Cd2Sb5F (A = Sr, Ba, Eu), and Ba5Cd2Sb5O(x) (0.5<x<0.7)

A new family of quaternary fluoro-antimonides A(5)Cd(2)Sb(5)F (A = Sr, Ba, Eu) and oxyantimonides Ba(5)Cd(2)Sb(5)O(x) (0.5相似文献   

New garnet compounds A 3 2+ B 2 2+ C4+V 2 5+ O12(A = Ca,Cd; B = Mg,Zn, Co,Ni, Cu,Mn, Cd; C = Ge,Si)

Garnet compounds A ₃ ²⁺ B ₂ ²⁺ C⁴⁺V ₂ ⁵⁺ O₁₂ (A = Ca, Cd; B = Mg, Zn, Co, Ni, Cu, Mn, Cd; C = Ge, Si) (space group \(Ia\bar 3d\) , Z = 8) have been prepared by solid-phase synthesis in air at 900–1250°C. Most of these compounds melt incongruently or decompose in the solid phase. The isomorphic capacity of garnets and their homogeneity fields are discussed. The structures of Ca₃Zn₂GeV₂O₁₂ and Ca₃Cu₂GeV₂O₁₂ have been refined by the Rietveld method.     

Targeting Vacancies in Nitridosilicates: Aliovalent Substitution of M2+ (M=Ca,Sr) by Sc3+ and U3+

Based on the known linking options of their fundamental building unit, that is the SiN₄ tetrahedron, nitridosilicates belong to the inorganic compound classes with the greatest structural variability. Although facilitating the discovery of novel Si–N networks, this variability represents a challenge when targeting non‐stoichometric compounds. Meeting this challenge, a strategy for targeted creation of vacancies in highly condensed nitridosilicates by exchanging divalent M²⁺ for trivalent M³⁺ using the ion exchange approach is reported. As proof of concept, the first Sc and U nitridosilicates were prepared from α‐Ca₂Si₅N₈ and Sr₂Si₅N₈. Powder X‐ray diffraction (XRD) and synchrotron single‐crystal XRD showed random vacancy distribution in Sc_0.2Ca_1.7Si₅N₈, and partial vacancy ordering in U_0.5xSr_2?0.75xSi₅N₈ with x≈1.05. The high chemical stability of U nitridosilicates makes them interesting candidates for immobilization of actinides.