晶体(NH4)2C4H4O6:VO2+的EPR参量及局域结构的研究

采用叠加模型和双旋-轨耦合参量模型,建立了结构参数与EPR参量之间的定量关系;较好地解释了[VO(H2O)5]2+络离子的局域结构和EPR参量;研究结果发现,(NH4)2C4H4O6:VO2+晶体中络离子[VO(H2O)5]2+的键长为R//≈0.130nm,R⊥≈0.195nm;在(NH4)2C4H4O6:VO2+晶体中,局域结构沿C4轴方向呈压缩的八面体结构;所得EPR参量的理论计算与实验测量数据符合很好.     

The structure and EPR properties of (CH2OHCH2NH3)2CuCl4

The title compound is a member of the (RNH₃)₂CuCl₄ layer perovskite family, space group C2/c, witha=21.624(5),b=7.511(1),c=7.431(2)Å, =89.56(2)° andV=1206.9(4)ų withZ=4. In the antiferrodistortive structure, the Cu(II) ion assumes an elongated octahedral coordination (unique Cu–Cl distances=2.274(2), 2.288(2), and 3.010(2)Å). The octahedra share corners with four neighbors to form a two-dimensional network. The –NH₃ moieties hydrogen bond to the layers, so that the –C₂H₅OH moieties form sheathes about each metal halide layer. A twofold disorder of the –C₂H₅OH groups is observed. The EPR spectrum is investigated to help understand the magnetic properties of the systems. Theg-values are consistent with strong intralayer exchange coupling. The EPR linewidths show evidence of spin diffusion effects at liquid nitrogen temperature. However, at room temperature, the spin anisotropies lead to broadening of the EPR lines through a phonon modulation mechanism.     

Single crystal EPR study of Mn(II) doped MgRb2(SO4)2·6H2O: A case of interstitial site

Single crystal electron paramagnetic resonance studies on magnesium rubidium sulphate hexahydrate doped with Mn(II) impurity, in the form of 0.1% of manganous chloride, are carried out at room temperature. The angular variation spectra of the crystal in the three orthogonal planes show that the paramagnetic impurity Mn(II) has entered the host lattice interstitially. The spin Hamiltonian parameters calculated are: g_xx = 1.974, g_yy = 1.928, g_zz = 1.980; A_xx = 9.28, A_yy = 8.58, A_zz = 9.87 mT and D_xx = ‐18.71, D_yy = ‐5.59, D_zz = 24.30 mT. The room temperature and liquid nitrogen temperature study for polycrystalline sample indicate no phase transition. The percentage covalency of Mn–O bond has been estimated to be 11. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of NH3(CH2)2NH3(BiI4)2·4H2O

The ethylenediammonium bis tetraiodobismuthate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=7.476(3)Å,b=13.194(3)Å,c=13.916(9)Å, β=95.22(6)°, space groupP2₁ lc withZ=2. The structure consists of disordered ethylenediammonium cations, water molecules and polynuclear anions in which slightly distored [BiI₆]^3? octahedra sharingcis edges are interconnected into chains. The [BiI₄]^? anions are connected through O(W2)?H...I hydrogen bonds, so that infinite two dimensional chains parallel to thea axis with anionic period [BiI₄(H₂O)]^? are formed in the structure. These chains are themselves interconnected by means of the O?H...I and N...O(I) bonds originating respectively from the water molecules and the ethylenediammonium entities, forming a three-dimensional network.     

Preparation of (NH4)2SO4 monocrystals

The preparation of (NH₄)₂SO₄ crystals has been studied, and the difficulties, especially the formation of numerous parasitical crystals and the irregular growth are discussed from a theoretical point of view and with regard to the performed investigations. Further on the habit of crystals and an acceptable procedure for the growing of homogeneous regular crystals are given. Likewise the effect of temperature, of P(H) of the crystallizing solution, the choice of seed crystals and the admixture of glycerine are reported.     

Molecular structure of trans-[Co(NH3)4(NH2CH3)Cl](ClO4)2

The title compound crystallizes in the orthorhombic space group Pnma, with a = 7.9209(5), b = 9.818(1), c = 16.867(2) Å, and Z = 4. The structure was solved employing 1864 independent x-ray reflections with I>2(I) by Patterson and difference Fourier techniques and refined by full-matrix least-squares to R = 0.036. The trans-[CO(NH₃)₄(NH₂CH₃)Cl](ClO₄)₂ molecule is on a crystallographic mirror plane. The cobalt ion is in an elongated octahedral coordination with four equatorial ammonia ligands [average Co–N distance equal to 1.966(2) Å], an axial methylamine [Co–N=1.965(3)Å], and an axial chlorine ion [Co–Cl=2.2771(9)Å]. Kinetic steric effects of the complex are interpreted in terms of structural results.     

EPR investigations of solid solutions of TSCC and TSCB doped with Mn2+

EPR investigations of Mn²⁺-doped solid solutions of TSCC and TSCB were performed between 4.2 K and 300 K. The Curie temperature vs. molar fraction of bromide x is nonlinear, for x ≧ 0,75 no ferroelectric EPR-line splitting occurs. The relation between the line widths and the molar fraction of bromide is discussed by means of a simple statistical model.     

EPR studies on Mn2+ centres in solid solutions of TSCC and TSCB

EPR investigations of Mn²⁺-doped solid solutions of TSCC and TSCB were performed between 130 K and 300 K. The axial fine structure parameter D vs bromine concentration x is nonlinear. The relation between the axial fine structure parameter and bromine concentration is discussed by means of a simple statistical model.     

Electron irradiation‐induced effects on optical spectra of (NH4)2ZnCl4: x Sr2+ single crystals

The effect of electron‐beam irradiation with different doses on optical constants of (NH₄)₂ZnCl₄: x Sr²⁺ crystals with x=0.000, 0.020, 0.039, 0.087 or 0.144 wt% has been studied. The optical transmission in the energy range 3.4‐6.4 eV was measured hence the absorption coefficient was computed as a frequency function. The absorption coefficient was also calculated as a function of electron‐beam dose. Irradiation with e‐beam did not affect the allowed indirect type of transition responsible for interband transitions of (NH₄)₂ZnCl₄: x Sr²⁺ crystals. Values of the optical energy gap E_g and optical moment E_p for electronic interband transition of unexposed and (NH₄)₂ZnCl₄: x Sr²⁺ crystals after e‐beam exposure were deduced. The area under the absorption band at 5.30 eV was used to evaluate the effect of e‐irradiation on optical parameters of samples with x=0.00, 0.020 or 0.039. A shift in the position and a nonmonotonic change in the intensity of this band with increasing e‐beam dose was observed. Changes in the E_g value were used to evaluate the effect of e‐beam exposure dose on (NH₄)₂ZnCl₄: x Sr²⁺ samples with x=0.087 or 0.144. The obtained results were compared with those obtained for the same crystals after irradiation with different γ‐doses.     

Non-crystallographic symmetries in the superstructure of (NH4)2ZnCl4

The modulation vector turned out to be equal 1/4. The lattice constants of the orthorhombic superstructure are determined: a = 12.6197(16) Å, b = 7.2107(81) Å, c = 4 × 9.2746(15) Å. The two of the four absences rules are interpreted as corresponding to the non-crystallographic symmetries: The space group P 2₁cn is determined on the basis of the single crystal X-ray pictures taking into account the experimental evidence of pyroelectricity in (NH₄)₂ZnCl₄.     

[Pd(NH3)4]2+负载氢基钛酸盐纳米管的制备及表征

以水热法制备的氢基钛酸盐纳米管(H-TNT)为基体,利用其离子交换性能在碱性条件下制备了[Pd(NH3)4]2+负载的氢基钛酸盐纳米管.采用ICAP、XRD、TEM、DRS、XPS等手段对材料进行了表征,研究了[Pd(NH3)4]2+的浓度和溶液的pH值对氢基钛酸盐纳米管离子交换性能的影响以及交换后样品的晶型、微观形貌、光学性能以及化学组成.结果表明:[Pd(NH3)4]2+负载在H-TNT表面,相互之间以Pd-O键作用.[Pd(NH3)4]2+负载之后,样品的晶型和管状形貌都没有变化,但是在400 ～ 600 nm范围对可见光有明显吸收.溶液浓度和pH值均对离子交换性能有影响,当[Pd(NH3)4]2+浓度较小,溶液中Pd与H-TNT的质量比较小时,[Pd(NH3)4]2+在9≤pH≤12的范围内能够全部负载到H-TNT上;当[Pd(NH3)4]2+浓度较大,溶液中Pd与H-TNT的质量比较大时,增大浓度和pH值均有利于[Pd(NH3)4]2+负载比例的提高,但pH≥10时,[Pd(NH3)4]2+的负载量却趋于饱和.     

Time evolution of a sol–gel process monitored by Mn2+ EPR spectroscopy

The time evolution of the tetraethoxysilane (TEOS)-based sol–gel process was investigated by EPR spectroscopy of a Mn²⁺ spin probe. Analysis of the EPR spectra recorded at room temperature (RT) and liquid nitrogen temperature (77 K) showed that the values of the g-factor (for the central Mn²⁺ sextet) were found to be, within experimental error, identical during the sol–gel process evolution. However, the peak-to-peak half width, ΔB_pp, of the spectral lines recorded at RT, the splitting of the forbidden hyperfine lines (and thus the zero-field splitting parameter, D) recorded at 77 K, and the averaged hyperfine splitting constant, A_av, at both temperatures, were found to change significantly during the various stages of the sol–gel process. These EPR spectral parameters allow us to monitor changes in the TEOS-based sol–gel reaction mixture during the liquid-to-solid-state transition. It was clearly demonstrated that the sol-to-gel transition as well as the hydration and dehydration process of gels could be successfully studied by Mn²⁺ EPR spectroscopy.     

Refractive indices of (NH4)2SO4 crystals under uniaxial pressure

Crystallography Reports - The effect of uniaxial pressure σ m ≤ 200 bar on the spectral (300–800 nm) and temperature (300–77 K) dependences of the refractive indices...     

Crystal structure of pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate, (NH3(CH2)2NH3)5(Sb2Cl11)2·4H2O

The pentakis ethylenediammonium bis undecachlorodiantimonate(III) tetrahydrate salt is monoclinic with the following unit cell dimensions:a=16.271(5) Å,b=13.004(4) Å,c=13.932(4) Å, β=111.72(2)°, space groupP2₁/c withZ=2. The structure was solved by Patterson methods and refined to a finalR value of 0.023 for 4435 reflections withF ₀>4σ(F ₀). The structure shows a layer arrangement perpendicular to thea axis: planes of the [Sb₂Cl₁₁]⁵⁻ bioctahedra alternate with planes of [NH₃(CH₂)₂NH₃]²⁺ dications. The [Sb₂Cl₁₁]⁵⁻ bioctahedra are connected through O−H...Cl hydrogen bonds, such that infinite chains of composition [Sb₂Cl₁₁(H₂O]_n ⁵ⁿ⁻ are formed in the structure, parallel to the twofold axis. These chains are themselves interconnected by means of N−H...Cl and O−H...Cl bonds originating from the [NH₃(CH₂)₂NH₃]²⁺ entities and the water molecules, respectively, and form a threedimensional network.     

晶体(NH_4)_2C_4H_4O_6∶VO~(2 )的EPR参量及局域结构的研究

采用叠加模型和双旋-轨耦合参量模型,建立了结构参数与EPR参量之间的定量关系;较好地解释了[VO(H2O)5]2 络离子的局域结构和EPR参量;研究结果发现,(NH4)2C4H4O6:VO2 晶体中络离子[VO(H2O)5]2 的键长为R//≈0.130nm,R⊥≈0.195nm;在(NH4)2C4H4O6:VO2 晶体中,局域结构沿C4轴方向呈压缩的八面体结构;所得EPR参量的理论计算与实验测量数据符合很好。     

Transport and Magnetotransport in the New Quasi-Two-Dimensional Organic Metal (BETS)2ZnBr4(C6H4Cl2) with Different Electron Structure of Neighboring Cation Layers

Intralayer and interlayer transports and Shubnikov – de Haas oscillations are investigated in the new dual-layered organic metal (BETS)₄ZnBr₄(C₆H₄Cl₂). It is shown that: a) the interlayer resistance behavior corresponds to incoherent transport; b) the behavior of quantum oscillations is well described by the model of a coherent network of magnetic breakdown orbits. Both the interlayer transport and quantum oscillations are in a good agreement with the theoretical calculation of the zone structure.     

配位聚合物{[Mn（H2BCPBA）2（H2O）4]}n的合成和表征

采用3,5-bi(4-carboxy-phenoxy)-benzoic acid(H3BCPBA)为配体,以Mn为中心离子采用自组装的方法合成了配位聚合物{[Mn(H2BCPBA)2(H2O)4]}n,采用单晶衍射仪,红外光谱,热重,固体紫外和元素分析对其进行了晶体结构的解析和表征。它属于三斜晶系,P1空间群,晶胞参数分别为a=0.58423(13)nm,b=1.3644(3)nm,c=1.3910(3)nm,α=109.173(2)°,β=98.927(3)°,γ=99.123(3)°,V=1.0082(4)nm,Mr=913.63,Z=1,Dc=1.505 g/cm3,μ=0.414 mm-1,F(000)=471.0。热重分析表明,该配合物在410℃下稳定,UV固体光谱表明,该配合物有很弱的吸收。