Ester Elimination: A General Solvent Dependent Non-Hydrolytic Route to Metal and Mixed-Metal Oxides

Molecular routes to metal oxides has become an area of intensescientific interest due to the technological relevance of thesematerials. Molecular routes are proving important as a result ofthe possibility to control the physical and chemical propertiesof the final materials.We have chosen to study non-hydrolytic methods, namely esterelimination reactions between two prototypical molecularprecursors metal alkoxides, M(OR)_n, and metal carboxylates, M(O₂CR)_n, to synthesize metal oxides: This method allows for the synthesis of pure metal oxides bycomplete elimination of the organic supporting ligands withconcomitant formation of M-O-M bridges.Furthermore, incomplete esterelimination can lead to isolation of molecular clusters asintermediates which can also be used as building blocks for theformation of metal oxides with controlled microstructure.Here we report a series of reactions between Sn and Si alkoxidesand carboxylates designed to gain further insight into thefactors governing ester elimination reactions. By choosingcompounds with varying coordination environments and stericaccessibility we have devised a set of criteria which shouldallow for successful ester elimination between metal alkoxide andcarboxylate compounds. Furthermore we have also shown theability of ester elimination derived molecular clusters withspecific microstructure to be used in the synthesis of bulkmaterials retaining the structural attributes of the precursor cluster.     

A view and a review of the melting of alkali metal halide crystals

Summary A representational model, proposed to account for the physical changes that accompany the melting of alkali halides, was described in Part 1 [1]. The liquid is portrayed as undergoing continual dynamic structural reorganization of its constituent ions between individual small domains, zones of various regular, crystal-type arrays. These alternative arrangements are stabilized by the enthalpy of melting, which, in liquids, relaxes the restriction for solids that only the single, most stable, crystal structure can be present. The dynamic character of the melt accounts for its fluid character and the loss of long-range order [1, 2]. This model is extended here to consider the phase diagrams of binary, common ion, alkali halide mixtures comprehensively reviewed in [3]. Factors determining whether each of these yields a eutectic, or a solid solution, on cooling are discussed and several trends in the 70-phase diagrams are identified. Eutectic formation, involving maintenance of the liquid state below the melting points of the pure components, is ascribed to the participation, in an extended dynamic equilibrium, of additional domains having the regular structures characteristic of double salts. The known crystalline double binary halides [3], Li/Cs or Rb/F, Cl, Br or I, melt at temperatures well below those of the simpler pure component salts. It is concluded that the set/liq model for melting, proposed in [1, 2], accounts for some important properties of the phase diagrams presented in [3].     

稀土元素在钢中的热力学参数及应用

综合报道了通过采用几种不同的高温金属溶液实验方法，研究所得到的稀土元素在金属溶液冶炼温度范围内分别与硫、氧、氧 硫、碳、氮、低熔点铜、磷、钛、铌、钒等重要元素相互作用规律及有关的一系列热力学参数和温度函数式，并简要地讨论了这些热力学参数在含稀土钢中的应用。     

Solvent extraction and bulk liquid membrane transport of Co(II) and Ni(II) ammine cations by proton-ionizable crown ethers

Separation efficiencies and selectivities in solvent extraction of Co(II) and Ni(H) ammine cations from aqueous solutions into chloroform and toluene and in transport through bulk toluene membranes by proton-ionizable crown ethers have been determined. Six proton-ionizable crown ethers with differing lipophilicities, polyether cavity sizes and ionizable groups (carboxylic and sulfonic acid functions) were examined. Higher selectivity and efficiency for Co(II) ammine cation extraction was observed for the more lipophilic, proton-ionizable crown ethers. Highly lipophilic crown carboxylic acids provided effective and selective transport of Co(II) ammine cations through bulk toluene membranes.Presented in part at the 6th International Symposium on High Purity Materials in Science and Technology: Preparation, Characterization and Application of Well-Defined Materials, Dresden, GDR, May 1985, Poster D91, Poster Abstracts, pp. 144, 145.All extraction and transport experiments were conducted at this location.     

Electrospray Ionization Mass Spectrometry (ESI-MS) as a Useful Tool for Fast Evaluation of Anion and Cation Complexation Abilities of a Cyclam Derivative

Electrospray ionization mass espectrometry (ESI-MS) has been used for the study of a cyclam derivative noncovalent interactions. At acidic pH, diprotonated macrocycle bound to different anionic species were observed. The selectivity shown by competitive experiments is rationalized with the help of semiempirical theoretical calculations. At basic pH, the base peak corresponded to the macrocycle-alkaline metal complexes, and again competition experiments showed different binding strength. Finally, experiments carried out in the presence of transition metal salts allowed the detection of the complexes present in the mixture and revealed their different kinetic behavior.     

Al3Ti1B1RE细化剂对罐用铝材的细化效果及稀土的作用

采用XRD，OM，SEM，EDAX等探讨了一种新型Al3Ti1B1RE中间合金细化剂对罐用铝材的细化效果及RE的作用。结果表明，该细化剂对罐用铝材的细化效果优于进口和国产Al3Ti1B，且具有长效性，达6h后仍未见明显衰退，明显提高了该材料的强度和塑性；其细化效果及稳定性好的主要原因是：RE可降低铝液的表面能，增加铝液对细化核心(如TiAl3，TiB2)的润湿性，既充分发挥了异质形核作用，又防止了TiB2聚集沉淀倾向；RE也极易在结晶前沿富集造成成分过冷，阻碍了α-Al晶粒生长，并促进其在细化核心上形核；此外RE还兼有一定的净化、细化和变质作用，尤其是净化作用提高了该细化剂的冶金质量。     

三菲咯啉合铁手性配合物键合DNA的立体选择性

应用光谱法研究了手性金属配合物［Ｆｅ（ｐｈｅｎ）３］＾２＋与小牛胸腺ＤＮＡ的作用，确定了△型异构体对Ｂ型右手螺旋ＤＮＡ有优先键合的立体选择性。     

药用缓释辅料——羟丙基甲基纤维素的合成及其缓释性能的研究

本文研究了药物缓释材料HPMC的合成方法,探讨了碱纤维素制备,醚化剂浓度,混合醚化剂配经以及产品后处理对高粘度HPMC的影响。本文还初步对KCl,氨茶碱,硝酸异山梨醇酯等药物采用合成的HPMC作辅料,进行了缓释制剂的研究,结果表明合成的HPMC具有满意的缓释性能。     

Magnetische Wechselwirkungen in Inselstrukturen ternärer Cobaltchalkogenide. Die Spinstrukturen von Na6CoS4 und Na6CoSe4

Magnetic Interactions in Ternary Cobalt Chalcogenides containing Isolated Tetrahedral Cobalt Anionic Groups. The Spin Structures of Na₆CoS₄ and Na₆CoSe₄ The sodium cobalt chalcogenides Na₆CoS₄ and Na₆CoSe₄ are characterized by isolated [CoX₄]-units. Despite the large distances of more than 6 Å between the cobalt ions magnetic inter-actions at low temperatures lead to threedimensionally ordered spin structures, that were determined from neutron diffraction experiments. The magnetic structure can be described in the Shubnicov group P_2abc2₁ with a unit cell that is four times as large as the crystallographic cell. The magnetic moments of both compounds correspond to the value expected for three unpaired electrons per Co²⁺ ion.     

Kinetics of the thermal dehydrations and decompositions of some mixed metal oxalates

Both isothermal and programmed temperature experiments have been used to obtain kinetic parameters for the dehydrations and the decompositions in nitrogen of the mixed metal oxalates: FeCu(ox)₂·3H₂O, CoCu(ox)₂·3H₂O and NiCu(ox)₂·3.5H₂O, [ox=C₂O₄]. Results are compared with those reported for the thermal decompositions of the individual metal oxalates, Cuox, Coox·2H₂O, Niox·2H₂O and Feox·2H₂O. X-ray photoelectron spectroscopy (XPS) was also used to examinee the individual and the mixed oxalates. Dehydrations of the mixed oxalates were mainly deceleratory processes with activation energies (80 to 90 kJ·mol⁻¹), similar to those reported for the individual hydrated oxalates. Temperature ranges for dehydration were broadly similar for all the hydrates studied here (130 to 180°C). Decompositions of the mixed oxalates were all complex endothermic processes with no obvious resemblance to the exothermic reaction of Cuox, or the reactions of physical mixtures of the corresponding individual oxalates. The order of decreasing stability, as indicated by the temperature ranges giving comparable decomposition rates, was NiCu(ox)₂>CoCu(ox)₂>FeCu(ox)₂, which also corresponds to the order of increasing covalency of the Cu−O bonds as shown by XPS. In celebration of the 60^th birthday of Dr. Andrew K. Galwey