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141.
《Polyhedron》2005,24(16-17):2321-2325
As photo-reactive precursors of high-spin organic compounds sterically separated from surroundings by bulky peripheral groups, diphenyldiazomethane derivatives substituted by tetrakis{3,5-bis(benzyloxy)benzyloxy} groups 1, by tetrakis[3,5-bis{3′,5′-bis(benzyloxy)benzyloxy}bezyloxy] groups 2, and nonakisdiazo compound associated with ferromagnetic spin couplers substituted by dodecakis{3,5-bis(benzyloxy)benzyloxy} groups 3, were prepared and their magnetic properties after irradiation in their own condensed films were investigated. Field dependences of magnetization and temperature dependences of χT value after irradiation of 1 and 2 clearly exhibited that spin centers i.e., diphenylcarbene parts of 1 and 2 were magnetically isolated from surrounding molecules each other by steric hindrance of the peripheral bulk substituents even in the neat films. In the case of 3, some part of molecules interacted antiferromagnetically with neighboring molecules but a fatal strong antiferromagnetic interaction was also avoided. 相似文献
142.
Margiolaki I Margadonna S Prassides K Hansen T Ishii K Suematsu H 《Journal of the American Chemical Society》2002,124(38):11288-11289
The powder neutron diffraction technique has been used for the direct observation of magnetic scattering below a Curie temperature of approximately 14 K in the fullerene-based molecular ferromagnet Eu6C60. Europium is in the divalent state with a magnetic moment of 7.1(3) muB per atom, and the configurational symmetry of the magnetic structure is body-centered cubic. Close contacts between Eu2+ and neighboring C60 units provide the signature of orbital hybridization, which can evidently account for the conducting and magnetic properties of the material. 相似文献
143.
《The Journal of chemical thermodynamics》2006,38(7):825-829
The high-temperature heat capacity of three lanthanide orthophosphates of monazite structure have been measured in the temperature range (450 to 1570) K. The data have been analysed in terms of a lattice term, represented by the 4f0 and 4f7 compounds LaPO4 and GdPO4, and an electronic term for CePO4. The calculated excess heat capacity thus obtained is in reasonable agreement with that calculated from the crystal field energies. 相似文献
144.
al-Ktaifani MM Bauer W Bergsträsser U Breit B Francis MD Heinemann FW Hitchcock PB Mack A Nixon JF Pritzkow H Regitz M Zeller M Zenneck U 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2622-2633
Several independent synthetic routes are described leading to the formation of a novel unsaturated tetracyclic phosphorus carbon cage compound tBu4C4P6 (1), which undergoes a light-induced valence isomerization to produce the first hexaphosphapentaprismane cage tBu4C4P6 (2). A second unsaturated isomer tBu4C4P6 (9) of 1 and the bis-[W(CO)5] complex 13 of 1 are stable towards similar isomerization reactions. Another starting material for the synthesis of the hexaphosphapentaprismane cage tBu4C4P6 (2) is the trimeric mercury complex [(tBu4C4P6)Hg]3 (11), which undergoes elimination of mercury to afford the title compound 2. Single-crystal X-ray structural determinations have been carried out on compounds 1, 2, 9, 11, and 13. 相似文献
145.
《Spectrochimica Acta Part B: Atomic Spectroscopy》2005,60(4):423-438
In order to clarify the mechanism of hydride formation, the isotopic composition of arsine, stibine, bismuthine, germane, stannane and hydrogen selenide formed by derivatization with either NaBD4 (TDB) or NaBH4 (THB) with inorganic As(III), Sb(III), Bi(III), Ge(IV), Sn(IV) and Se(IV) in aqueous reaction media and under various reaction conditions was determined. Batch hydride generation and gas chromatography–mass spectrometry (GC–MS) were employed. The analyte, present in 0.5–5 ml of acid solution (0.1–10 M in HCl or HNO3 or HClO4) was derivatized with 1 ml of 0.25–0.5 M TDB / THB in 0.1 M NaOH solution. For TDB derivatization in H2O reaction media, almost pure BiD3 and SbD3 were always obtained for Bi(III) and Sb(III). Nearly pure AsD3 could be obtained only under some reaction conditions. In general, for As(III), the isotopic composition of the arsines depends strongly on reaction conditions and included all possible AsHnD3−n from almost pure AsD3 to almost pure AsH3. For Ge(IV) and Sn(IV), the isotopic composition of generated GeHnD4−n and SnHnD4−n depends on reaction conditions, but pure GeD4 and SnD4 could never be obtained. Pure H2Se was obtained in all cases, independent of reaction conditions. The occurrence of side reactions involving D–H exchange in TBD during its hydrolysis and before the derivatization step, as well as on recently formed hydrides following derivatization was investigated. D–H exchange in TDB during acid hydrolysis appears to occur to a limited extent. Amongst the hydrides, H2Se undergoes H–D exchange whereas germane and stannane do not exchange at all. Arsine undergoes D–H exchange at elevated acidities (pH < 0) whereas stibine and bismuthine do not exchange significantly during the generation and stripping steps.A reaction model for hydride generation is proposed accounting for primary reactions giving rise to hydride formation through reaction intermediates, as well as side reactions involving D–H exchange and decomposition of reactive hydroboron species, reaction intermediates and final products. Hydrides are formed by direct hydrogen transfer from boron to the analyte atom, most likely through concerted mechanisms taking place via reaction intermediates. 相似文献
146.
《Tetrahedron: Asymmetry》2005,16(6):1233-1238
A series of new H8-BINOL-derived unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands have been synthesized and successfully used in Rh-catalyzed asymmetric hydrogenations. The same or higher enantioselectivities (99.9% ee) were achieved in the hydrogenation of dimethyl itaconate and α-dehydroamino acid esters as those obtained with BINOL-derived analogues. However, slightly lower enantioselectivities (99.0% ee) were obtained in the hydrogenation of enamides. 相似文献
147.
Xinbo Zhang Danzi Sun Wenya Yin Yujun Chai Minshou Zhao 《Journal of Solid State Electrochemistry》2006,10(4):236-242
This paper presents results concerning structure and electrochemical characteristics of the La0.67Mg0.33 (Ni0.8Co0.1Mn0.1)
x
(x=2.5–5.0) alloy. It can be found from the result of the Rietveld analyses that the structures of the alloys change obviously
with increasing x from 2.5 to 5.0. The main phase of the alloys with x=2.5–3.5 is LaMg2Ni9 phase with a PuNi3-type rhombohedral structure, but the main phase of the alloys with x=4.0–5.0 is LaNi5phase with a CaCu5-type hexagonal structure. Furthermore, the phase ratio, lattice parameter and cell volume of the LaMg2Ni9phase and the LaNi5 phase change with increasing x. The electrochemical studies show that the maximum discharge capacity increases from 214.7 mAh/g
(x=2.5) to 391.1 mAh/g (x=3.5) and then decreases to 238.5 mAh/g (x=5.0). As the discharge current density is 1,200 mA/g, the high rate dischargeability (HRD) increases from 51.1% (x=2.5) to 83.7% (x=3.5) and then decreases to 71.6% (x=5.0). Moreover, the exchange current density (I
0) of the alloy electrodes first increases and then decrease with increasing x from 2.5 to 5.0, which is consistent with the variation of the HRD. The cell volume reduces with increasing x in the alloys, which is detrimental to hydrogen diffusion and accordingly decreases the low-temperature dischargeability
of the alloy electrodes. 相似文献
148.
149.
《Chemical physics letters》2006,417(1-3):217-221
Cobalt thin films were deposited by pulsed electrodeposition on n-doped silicon substrates. We show that the morphology and the magnetic properties of the samples can be controlled by a careful choice of the deposition conditions. Atomic force microscopy measurements reveal a granular growth with grain size and homogeneity strongly dependent on the total deposition time and pulse frequency of the applied signal. Magnetic force microscopy and magnetization measurements indicate the formation of magnetically correlated grain systems with a maximum magnetic correlation and homogeneity for samples with grain diameters of about 40 nm. 相似文献
150.
《Radiation Physics and Chemistry》2007,76(3):631-635
Electronic stopping cross-section of compounds is calculated by considering velocity-dependent projectile and target electronic structure, and applying the Bragg addition rule. For velocity dependencies of projectile and target, we used previously developed stopping power formula by Tufan et al. In this work, we used two different screening functions. We calculated the electronic stopping cross-section of Al2O3, CO2, and SiO2 for O and Si ions. We compared our results with the other theoretical calculations and found 4–8% deviation. 相似文献