首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   21篇
  免费   0篇
  国内免费   3篇
化学   24篇
  2016年   2篇
  2013年   1篇
  2012年   1篇
  2009年   2篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   2篇
  2004年   3篇
  2002年   3篇
  1999年   1篇
  1998年   1篇
  1997年   2篇
  1992年   1篇
  1988年   1篇
排序方式: 共有24条查询结果,搜索用时 15 毫秒
1.
Three Alkali‐Metal Erbium Thiophosphates: From the Layered Structure of KEr[P2S7] to the Three‐Dimensional Cross‐Linkage in NaEr[P2S6] and Cs3Er5[PS4]6 The three alkali‐metal erbium thiophosphates NaEr[P2S6], KEr[P2S7], and Cs3Er5[PS4] show a small selection of the broad variety of thiophosphate units: from ortho‐thiophosphate [PS4]3? and pyro‐thiophosphate [S3P–S–PS3]4? with phosphorus in the oxidation state +V to the [S3P–PS3]3? anion with a phosphorus‐phosphorus bond (d(P–P) = 221 pm) and tetravalent phosphorus. In spite of all differences, a whole string of structural communities can be shown, in particular for coordination and three‐dimensional linkage as well as for the phosphorus‐sulfur distances (d(P–S) = 200 – 213 pm). So all three compounds exhibit eightfold coordinated Er3+ cations and comparably high‐coordinated alkali‐metal cations (CN(Na+) = 8, CN(K+) = 9+1, and CN(Cs+) ≈ 10). NaEr[P2S6] crystallizes triclinically ( ; a = 685.72(5), b = 707.86(5), c = 910.98(7) pm, α = 87.423(4), β = 87.635(4), γ = 88.157(4)°; Z = 2) in the shape of rods, as well as monoclinic KEr[P2S7] (P21/c; a = 950.48(7), b = 1223.06(9), c = 894.21(6) pm, β = 90.132(4)°; Z = 4). The crystal structure of Cs3Er5[PS4] can also be described monoclinically (C2/c; a = 1597.74(11), b = 1295.03(9), c = 2065.26(15) pm, β = 103.278(4)°; Z = 4), but it emerges as irregular bricks. All crystals show the common pale pink colour typical for transparent erbium(III) compounds.  相似文献   
2.
Cyclic Thiophosphates, Products from the Reaction of Elemental Phosphorus with Alkylammonium Polysulfides White Phosphorus reacts very rapidly above its melting point with alkylammonium polysulfide solutions in chloroform or dimethylformamide. The reaction products are mixtures of thiophosphates, which contain compounds with phosphorus in different oxidation states. The composition of these mixtures may be changed by varying the amounts of applied polysulfidic sulfur and alkylamine. Several cyclic thiophosphates have been isolated from the mixtures in good yields; some contain P? P bonds.  相似文献   
3.
在2-300K温度范围内测定了REPS4系列化合物的磁化率,进而研究了各个化合物的磁化率和倒易磁化率随温度的变化,最后用50-300K温度范围的磁化率数据拟合得到各个顺磁稀土离子RE^3+的居里-外斯常数和有效顺磁磁矩μeff。  相似文献   
4.
A new chromium thiophosphate, K3Cr2(PS4)3 has been prepared and characterized by single‐crystal diffraction, temperature dependent magnetic susceptibility measurements and optical spectroscopy. K3Cr2(PS4)3 crystallizes in the monoclinic space group P21/n (No. 14) with a = 9.731(2) Å, b = 11.986(2) Å, c = 17.727(4) Å, β = 96.52(2)°, V = 2054.2(2) Å3, Z = 4, and R = 0.044. The anionic part of the structure consists of dimeric Cr23‐S3PS)2 units which are linked by bidentate PS4 groups to form infinite one‐dimensional [S2PS2Cr23S3PS)2]3— chains separated by K+ cations. The CrIII centers of the Cr23‐S3PS)2 units are antiferromagnetically coupled. The magnetic susceptibility data may be fitted using a D‐Heisenberg model for S = 3/2 with g = 2.02 and J/k = 10K. K3Cr2(PS4)3 is semiconducting with an optical band gap of 1.35 eV.  相似文献   
5.
Colourless block‐shaped crystals of [(NH4)2(2.2.2‐cryptand)2][P2S8] ( 1 ) and [(NH4)2(18‐crown‐6)2][P2S8]·H2O ( 2 ) could be obtained by the reaction of an aqueous solution of ammonium hexathiohypodiphosphate, (NH4)4P2S6·2 H2O, with sulfur and 2.2.2‐cryptand or 18‐crown‐6. The crystal structures of both compounds have been determined by single‐crystal X‐Ray diffraction analysis. Compound 1 crystallizes in the monoclinic space group C2/c with a = 2032.7(2), b = 1243.6(2), c = 2244.6(2) pm, β = 98.64(1)°, and Z = 8, whereas compound 2 crystallizes also monoclinic in the space group P21/c with a = 2121.3(2), b = 865.5(1), c = 2345.4(2) pm, β = 91.96(1)°, and Z = 4. It could be established that the title compounds contain a new type of six‐membered [1,2‐P2S4] ring with P – P bond and three S – S linkages. The tetrahedral environment of each phosphorus is completed by a (formally) single and double bonded sulfur atom attached externally to the [1,2‐P2S4] ring. These terminal PS2 units are mesomerically stabilized according to their P – S distances. FT‐IR and FT‐Raman spectra of the title compounds are recorded and interpreted.  相似文献   
6.
硫代磷酸酯类化合物的^31P化学位移加和规则   总被引:2,自引:0,他引:2  
对近80年种自行合成的硫逐及硫超磷酸酯类化合物进行了^31P NMR谱的测定,提出了一个经验方程、一套化学位移参数的立体电子效应参数,比较准确地计算了它们的^1P化学位移,其计算值与测定值的平均误差为±0.096,标准偏差为±0.13。同时,就取代基的电负性,键角和立体电子效应等对^31P化学位移的影响作了理论上的探讨。  相似文献   
7.
The two non-isotypical rubidium rare-earth(III) thiophosphates Rb3M3[PS4]4 of praseodymium and erbium can easily be obtained by the stoichiometric reaction of the respective rare-earth metal, red phosphorus and sulfur with an excess of rubidium bromide (RbBr) as flux and rubidium source at 950°C for 14 days in evacuated silica tubes. The pale green platelet-shaped single crystals of Rb3Pr3[PS4]4 as well as the pink rods of Rb3Er3[PS4]4 are moisture sensitive. Rb3Pr3[PS4]4 crystallizes triclinically in the space group (, , , α=84.329(4)°, β=88.008(4)°, γ=80.704(4)°; Z=2), Rb3Er3[PS4]4 monoclinically in the space group P21/n (, , , β=95.601(6)°; Z=4). In both structures, there are three crystallographically different rare-earth cations present. (M1)3+ is eightfold coordinated in the shape of a square antiprism, (M2)3+ and (M3)3+ are both surrounded by eight sulfur atoms as bicapped trigonal prisms each with a coordination number of eight as well as for the praseodymium, but better described as CN=7+1 in the case of the erbium compound. These [MS8]13− polyhedra form a layer according to by sharing edges with the isolated [PS4]3− tetrahedra (d(P-S)=200-209 pm, ?(S-P-S)=102-116°). These layers are stacked with a repetition period of three in the case of the praseodymium compound, but of only two for the erbium analog. The rubidium cation (Rb1)+ is located in cavities of these layers and tenfold coordinated in the shape of a tetracapped trigonal antiprism. The also tenfold but more irregularly coordinated rubidium cations (Rb2)+ and (Rb3)+ reside between the layers.  相似文献   
8.
The novel uranium thiophosphate CsLiU(PS4)2 has been synthesized by reacting uranium metal, Cs2S, Li2S, S, and P2S5 at 700 °C in an evacuated silica tube. The crystal structure was determined by single‐crystal X‐ray diffraction techniques. CsLiU(PS4)2 crystallizes in the rhombohedral space group R$\bar{3}$ c (a = 15.2797(7) Å; c = 28.778(2) Å, V = 5818.7(5) Å3, Z = 18). The structure ofCsLiU(PS4)2 is a unique three‐dimensional U(PS4)22– framework with large tunnels with an approximate diameter of 6.6 Å running parallel to the crystallographic c axis. The tunnels are filled with Cs+ cations. The smaller Li+ cations are located at tetrahedral sites at the periphery of the channels. In the structure of CsLiU(PS4)2 the uranium atoms are coordinated by thiophosphate groups in a pseudotetrahedral fashion, and the PS4 groups act as linear connectors. Topologically, CsLiU(PS4)2 may be regarded a chalcogenide analogue of silicate frameworks, with the uranium atoms and PS4 groups replacing silicon and oxygen atoms. Alternatively, CsLiU(PS4)2 may be viewed as a coordination polymer, which is formed in salt melts by the solid state equivalent of the “self‐assembly” reactions in solution. Magnetic susceptibility measurements indicated Curie–Weiss‐type behavior between 4 K and 300 K. The μeff of 2.83 μB at 300 K is in agreement with an f2 configuration of U4+.  相似文献   
9.
Ag2Nb[P2S6][S2] (1) was obtained from the direct solid state reaction of Ag, Nb, P2S5 and S at 500 °C. KAg2[PS4] (2) was prepared from the reaction of K2S3, Ag, Nd, P2S5 and extra S powder at 700 °C. Compound 1 crystallizes in the orthorhombic space group Pnma with a=12.2188(11), b=26.3725(16), c=6.7517(4) Å, V=2175.7(3) Å3, Z=8. Compound 2 crystallizes in the non-centrosymmetric tetragonal space group with lattice parameters a=6.6471(7), c=8.1693(11) Å, V=360.95(7) Å3, Z=2. The structure of Ag2Nb[P2S6][S2] (1) consists of [Nb2S12], [P2S6] and new found puckered [Ag2S4] chains which are along [001] direction. The Nb atoms are located at the center of distorted bicapped trigonal prisms. Two prisms share square face of two [S22−] to form one [Nb2S12] unit, in which Nb-Nb bond is formed. The [Nb2S12] units share all S2− corners with ethane-like [P2S6] units to form 14-membered rings. The novel puckered [Ag2S4] chains are composed of distorted [AgS4] tetrahedra and [AgS3] triangles that share corners with each other. These chains are connected with [P2S6] units and [Nb2S12] units to form three-dimensional frame work. The structural skeleton of 2 is built up from [AgS4] and [PS4] tetrahedra linked by corner-sharing. The three-dimensional anionic framework contains orthogonal, intersecting tunnels directed along [100] and [010]. This compound possesses a compressed chalcopyrite-like structure. The structure is compressed along [001] and results from eight coordination sphere for K+. Both compounds are characterized with UV/vis diffuse reflectance spectroscopy and compound 1 with IR and Raman spectra.  相似文献   
10.
Sodium Monothiophosphate(V): Crystal Structure and Sodium Ionic Conductivity Anhydrous sodium monothiophosphate Na3PO3S was synthesized along a novel route by freezedrying of the hydrate and subsequent annealing in an argon atmosphere. The crystal structure was determined using X‐ray and neutron powder data. The structural model was found by means of a combined optimization of the difference between the calculated and the measured powder intensities, and of the potential energy of the system. Simultaneous Rietveld refinements of the neutron and X‐ray data (R3c, a = 8.4442(1) Å, c = 11.7412(1) AÅ) resulted in a profile R‐value Rp = 4.86 % and weighted profile R‐value Rwp = 5.86 %. The baricenters of the PO3S tetrahedra are arranged in the sense of a cubic close packing whith the P—S‐bonds oriented in a polar manner parallel to the c axis, and with the PO3‐groups in an eclipsed mutual orientation. The Na‐P‐S‐framework of Na3PO3S is — according to the formulation SPNa3 — related to the LiNbO3‐structure type. The title compound was investigated using solid state NMR spectroscopy. The isotropic chemical shift δiso is 33.4 ppm for the phosphorus nuclei, and 7.7 ppm for the sodium nuclei. For the latter ones, a quadrupole coupling constant QCC = 3.0 MHz and an asymmetry parameter ηQ = 0.40 were determined. The chemical shift tensor of the phosphorus nuclei is characterized by an asymmetry parameter η = 0.43 and an anisotropy Δσ = ‐48.5 ppm. Consequently, phosphorus as well as sodium, is not surrounded axial symmetrically.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号