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51.
Pyridine-based, structurally isomeric two macrocyclic compounds displayed a remarkably different complexation nature. The cage-type compound has an ideal structure for spherical cations, especially for the NH4+ ion, but the reaction with some transition metals and Ln3+ produced its protonated species. On the other hand, its isomer formed complexes with alkali metals and lanthanides (1:1) and also with transition metals. Some structures of the complexes were clarified by crystallographic analyses. 相似文献
52.
The polycrystalline sample of layered compound FePS_3 has been investigated by using M?ssbauer spectroscopy (12K to 300K), magnetic susceptibility measurements, x-ray diffraction and FTIR spectroscopy. The antiferromagnetic order exists below T_N=120.5±1K. The M?ssbauer spectra below T_N indicate that the magnetization axis is perpendicular to the layer of FePS_3, and the divalent iron cations are in their high spin configurations. By fitting the hyperfine field parameters near the Néel temperature, we obtain information on the nature of magnetic interactions in the material. The results show that the magnetic coupling can be treated by the two-dimensional Ising model, and it can be interpreted on the basis of a crystal-field effect. 相似文献
53.
54.
Mitsuru Ueda Tetsuya Abe Mitsuo Oda 《Journal of polymer science. Part A, Polymer chemistry》1992,30(9):1993-1998
Aromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc. 相似文献
55.
杨慧 《原子与分子物理学报》2002,19(4):411-416
以二维复式晶格作为有限系统的集团模型,在紧束缚近似下,计算了π电子在最近邻及次近邻跳跃集团的态密度.讨论了不同结构参数对态密度及带宽的影响. 相似文献
56.
A new ternary complex [Ni(phen)(pmal)]·8H2O (phen = 1,10-phenanthroline,pmal2- = phenethyl malonic acid) has been synthesized by the reaction of nickel acetate, phen and phenethyl malonic acid. Elemental analysis, IR spectra and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure. Crystal data for this complex: triclinic system, space group P1, a = 10.387(5), b = 13.112(6), c = 14.229(6) (A), α = 76.176(7), β =83.778(8), y = 71.770(6)°, C35H42N4O12Ni, Mr= 769.44, Z = 2, F(000) = 808, V = 1786.1 (A)3, Dc =1.431 g/cm3, μ = 0.612 mm-1, the final R = 0.0653 and wR = 0.1033 for 9379 (Rint = 0.0244)independent reflections and 4730 observed reflections (I > 2σ(I)). Structural analysis shows that the coordination geometry of Ni(Ⅱ) is a distorted octahedron. A novel two-dimensional structure is constructed from (H2O)4 and (H2O)12 water clusters, and the complex forms a 3-D network supramolecular structure by hydrogen bonds and π-π stacking of neighboring phens. 相似文献
57.
R. Venkat narayan Vinod Kanniah Aruna Dhathathreyan 《Journal of Chemical Sciences》2006,118(2):179-184
Cobalt oxides were prepared by three different methods: (1) by reacting cobalt nitrate with oxalic acid, (2) co-precipitating
cobalt nitrate with sodium carbonate, and (3) using sodium dodecyl sulphate as organic surfactant. All three samples were
characterized before and after calcination by solvent extraction and the resulting products examined by IR spectroscopy. In
the case of method 3, the removal of surfactant was followed by TGA studies. Products from all three methods were identified
by XRD. Peaks in low angle XRD indicate the porous nature of the oxides. The morphology of the pores was studied by transmission
electron microscopy. Some irregular pore structures were obtained for samples from methods 1 and 2, with an average size of
4–6 nm. Only the product from method 3 using SDS as template showed ordered structure and optimum size, and Brunauer-Emmet-Teller
surface areas of the as-prepared, as well as the treated samples, exhibited H3 type hysteresis. The samples from the three
methods were used as catalysts in the oxidation reaction of cyclohexane under mild conditions and the catalytic efficiency
of the cobalt oxide was comparable with mesoporous cobalt oxides. 相似文献
58.
A three-dimensional Ising-like model doped with anti-ferromagnetic (AFM) bonds is proposed to investigate the magnetic properties
of a doped triangular spin-chain system by using a Monte-Carlo simulation. The simulated results indicate that a steplike
magnetization behavior is very sensitive to the concentration of AFM bonds. A low concentration of AFM bonds can suppress
the stepwise behavior considerably, in accordance with doping experiments on Ca3Co2O6. The analysis of spin snapshots demonstrates that the AFM bond doping not only breaks the ferromagnetic ordered linear spin
chains along the hexagonal c-axis but also has a great influence upon the spin configuration in the ab-plane.
相似文献
59.
In this paper, the polymerization of styrene initiated by potassium (K)-tetrahydrofuran (THF)-graphite intercalation compound (GIC) (K-THF-GIC) was studied. The mechanism of the polymerization was determined to be anionic polymerization according to its characteristics. The effect of the concentration of the initiator and monomer was studied. It was found that the polymerization mainly occurred on the surface and edge of the intercalated graphite. It was also shown that the polarity of solvent has little effect on the polymerization yield in this system. 相似文献
60.
WU Feng-Min XU You-Sheng LI Qiao-Wen 《理论物理通讯》2006,46(8)
A comprehensive simulation model -deposition,diffusion, rotation, reaction and aggregation model is presented to simulate the formation processes of ramified clusters on liquid surfaces, where clusters can diffuse and rotate easily. The mobility (including diffusion and rotation) of clusters is related to its mass, which is given by Dm = Dos-γD and θm =′θos-γθ, respectively. The influence of the reaction probability on the kinetics and structure formation is included in the simulation model. We concentrate on revealing dynamic scaling during ramified cluster formation. For this purpose, the time evolution of the cluster density and the weight-average cluster size as well as the cluster-size distribution scaling function at different time are determined for various conditions. The dependence of the cluster density on the deposition flux and time-dependence of fractal dimension are also investigated. The obtained results are helpful in understanding the formation of clusters or thin film growth on liquid surfaces. 相似文献