Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr)₃ and KMnO₄ with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH)₃ nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO₄ plays a crucial role in determining the particle morphology of La(OH)₃. The reason lies in the fact that KMnO₄ is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the ±(1 0 0), ±(0 1 0) and ±(−110) crystal facets. By adjusting the molar La(OiPr)₃-to-KMnO₄ ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH)₃ nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH)₃ nanofibers and β-MnOOH nanoparticles at the temperature of 800 °C for 8 h yielded polyhedral LaMnO₃ and worm-like La₂O₃ nanoparticles as final products.     

四苯基卟啉在改性磷酸锆层间的插入及荧光增强

近年来,出于节约一次性能源的考虑,人们已经加大对太阳能等天然资源的利用,致力于模拟天然光合作用的研究[1￣3],而光合作用中的捕光复合物又称为光子天线。光子天线中往往存在一种或几种猝灭剂,猝灭剂吸收光子后产生激发态的能量可以在不同分子或者同一分子的不同生色团之间转移,转移出能量的一方为能量给体,另一方为能量受体。     

Tetra(μ3-hydroxo)hexa(μ2-carboxylato-O,O′)-bridged tetranuclear terbium(III) cubane complex

A novel tetranuclear terbium(III) complex [Tb₄(OH)₄(pybet)₆(H₂O)₈][Tb₄(OH)₄(pybet)₆(H₂O)₇ (NO₃)](ClO₄)₁₄·6H₂O has been synthesized and shown by X-ray crystallography to have a cubane-like Tb₄(μ₃-OH)₄(μ₂-carboxylato-O,O′)₆ core. The ligand pybet is pyridinoacetate, C₅H₅⁺N-CH₂CO₂⁻. Magnetic susceptibility data were measured for this Tb₄ complex in the range of 2.0–320 K and in fields of 1.0 G to 50.0 kG. It is concluded that either there is very weak antiferromagnetic exchange interaction (J = −0.015 cm⁻¹) or there is a small crystal-field splitting of the ⁷F₆ Tb^III ground state.     

New Hexazirconium Clusters Containing Hydrogen Atoms

Reduction of ZrBr₄ with HSnBu₃ yielded a blue solid. When this blue solid was treated with PMe₃, a hexanuelear cluster [Zr₆Br₁₄H₄( PMe₃)₄] (2) was isolated. Reaction of the blue solid with [PPh₄]Br in CH₂Cl₂ resulted in the formation of a paramagnetic and unstable cluster anion, [Zr₆Br₁₈H₅]^2– (3), which disproportionated to form a new cluster anion, [Zr₆Br₁₈H₅]^3– (4) and some Zr(IV) species. Compounds containing 4 can also be obtained from reaction of the blue solid with Br^– in MeCN. Reduction of ZrCl₄ with HsnBu₃ gave a red–brown solid, and [Zr₆Cl₁₄H₄(AsMe₃)₄] (9) and [Zr₅Cl₁₂H₄(AsMe₃)₅](8) were obtained by reaction of the red–brown solid with AsMe₃. No cluster compounds containing amine ligands were obtained in the reaction of the red–brown solid with amines; only compounds containing the [Zr₆Cl₁₈ H₅]^3– anion and ammonium cations were isolated. Altogether ten products were characterized by single crystal X-ray diffraction and where possible, by ¹H NMR studies.     

Convenient procedure of Horner-Wadsworth-Emmons olefination for the synthesis of simple and functionalized α,β-unsaturated nitriles

A mild and practical procedure of Horner-Wadsworth-Emmons olefination promoted by lithium hydroxide and α-cyano phosphonates has been set up for the synthesis of α,β-unsaturated nitriles. The reaction conditions are tolerated by functionalized ketones and the exclusive formation of E-γ-hydroxy α,β-unsaturated nitriles has been observed.     

Zirconium-mediated conversion of homoallylic ethers into cyclopropane derivatives

Homoallylic ethers react with Cp₂ZrCl₂/2 n-BuLi reagent to afford cyclopropane derivatives. Cyclopropylcarbinyl-homoallyl rearrangements involving zirconium species are observed depending on the substrate structure.     

B2O3/TiO2-ZrO2催化环己酮肟气相Beckmann重排反应研究 Ⅰ.B2O3含量的影响

 制备了不同B2O3含量（0～20％）的B2O3／TiO2－ZrO2固体酸催\r\n化剂，用XRD，FT－IR，N2吸附及NH3－TPD等方法测定了其结构、比表\r\n面积、孔分布和表面酸性．结果表明，当B2O3含量较低（≤5％）时，\r\n催化剂呈无定形态，样品中的B2O3主要以BO4结构存在．当B2O3含量较\r\n高（≥8％）时，催化剂中的TiO2－ZrO2以ZrTiO4晶相存在，分散于Ti\r\nO2－ZrO2表面的B2O3主要以玻璃体形式和BO3结构存在．随着B2O3含量\r\n的增加，催化剂的比表面积减小，孔径增大．300℃下的环己酮肟气相\r\nBeck－mann重排反应结果表明，随着B2O3含量的增加，己内酰胺的选择\r\n性逐渐增大，而己内酰胺的收率在B2O3含量为12％时达到最大值．讨论\r\n了B2O3／TiO2－ZrO2的催化性能与其表面酸性及孔径大小的关系．     

Heterometallic zirconocene(iii) aluminum hydride complex (Cp2ZrH)2HAlCl2·C4H8O2·C6H6

The heterometallic zirconocene(iii) aluminum hydride complex (Cp₂ZrH)₂HAlCl₂·C₄H₈O₂·C₆H₆ was synthesized by reduction of Cp₂ZrCl₂ with lithium aluminum hydride in the presence of Cp₂TiBH₄ and 1,4-dioxane, and its structure was established by X-ray diffraction analysis.     

超声波处理对球形β-Ni(OH)2结构及电化学性能的影响

A method of ultrasonic treatment （UST） was first used to modify the structure and electrochemical performance of nickel hydroxide for the active material of nickel series alkaline batteries. The experimental results showed that UST was an effective method to improve the electrochemical performance of β-Ni（OH）2 such as specific discharge capacity, discharge potential, electrochemical reversibility and oxygen evolution over-potential. The results of electrochemical impedance spectroscopy, powder X-ray diffraction and particle size distribution indicated that the improvement of the performance of β-Ni（OH）2 through UST was attributed to the reduction of the charge-transfer resistance （Rt） and the diffusion impedance （Zw）, which resulted from the decrease of the crystallite and particle size and the increase of interlayer spacing. Diffusion coefficient of proton DH of ultrasonic treated β-Ni（OH）2 gained by CV tests was 1.13 × 10^-11 cm^2/s, and the average discharge specific capacity of ultrasonic treated β-Ni（OH）2 electrode was 301 mAh/g.     

Synthesis, nuclear, and magnetic structures and magnetic properties of [Mn3(OH)2(SO4)2(H2O)2

[Mn(3)(OH)(2)(SO(4))(2)(H(2)O)(2)] and its deuterated analogue were synthesized by a hydrothermal technique and characterized by differential thermal analysis, thermogravimetric analysis, and IR spectroscopy. Its nuclear structure, determined by single-crystal X-ray analysis and Rietveld analysis of neutron powder-diffraction data, consists of a 3D network of chains of edge-sharing Mn(1)O(6), running along the c axis, connected by the apices of Mn(2)O(6) and SO(4) units. It is isostructural to the nickel analogue. Determination of the magnetic structure and measurements of magnetization and heat capacity indicate the coexistence of both magnetic long-range ordering (LRO) and short-range ordering (SRO) below a Néel temperature of 26 K, while the SRO is retained at higher temperatures. The moments of the two independent Mn atoms lie in the bc plane, and that of Mn(1) rotates continuously by 54 degrees towards the c axis on decreasing the temperature from 25 to 1.4 K. While the SRO may be associated with frustration of the moments within a Mn(3) trimer, the LRO is achieved by antiparallel alignment of the four symmetry-related trimers within the magnetic unit cell. A spin-flop field, measured by dc and ac magnetization on a SQUID, is observed at 15 kOe.