冷压与热压处理对YBa2Cu3O7-δ的结构相变和超导电性的影响

 本文研究了冷压（2.2~5.2 GPa）与热压（2.2 GPa,2.50~950 ℃）对YBa₂Cu₃O_7-δ的正交→四方相转变区和超导电性的影响。冷压保持其正交结构,但破坏了超导性,在98 K（失超点）到室温呈半导体特性,再在空气中烧结,可恢复液氮温区的零电阻状态。以Cu锅密封样品,热压处理至950 ℃,不发生Cu的析出。热压处理后,98 K（失超点）到室温呈半导体特性,再经通氧烧结,于86 K出现零电阻。热压处理过程,从450~950 ℃为正交→四方转变区。950 ℃为转变结束温度,大大高于氧气、空气、氮气、真空状态的温度。400 ℃附近为起始转变温度,低于氮气、氧气气氛的温度。因此相变区加宽。T_0-t结束温度升高,与Cu锅的抑制还原作用有密切关系。如降低高压淬火速率（<<10² ℃/s）,或随后辅以氧气氛中的后处理,将有利于获得既有高密度又有高T_c的YBa₂Cu₃O_7-δ超导体。     

Pdn(n=1-7)团簇及其与甲烷相互作用的密度泛函理论研究

用密度泛函理论(DFT)的B3LYP方法, 对Pdn(n=1-7)团簇的几何结构、振动频率及其与甲烷分子间的相互作用进行了理论研究. 结果表明, 随着Pd原子数增多, 团簇结构对团簇大小的依赖性减弱, 结构参数向金属晶体趋近. 在Pdn(n=1-7)团簇上, 甲烷的表面吸附作用较弱. Pd2CH4中, 甲烷受到两个Pd原子的活化作用, 活化程度增强, 吸附能增大. 在PdnCH4 (n=1, 3-7)体系中, 甲烷的吸附能随着团簇模型的增大而减小, 趋近于其在金属晶面上的吸附能.     

Synthesis and Crystal Structure of 7-Nitro-5-sulfo-napthalene-1,4-dicarboxylate Acid

1 INTRODUCTION Napthalene-1,4-dicarboxylate acid (1,4-NDC) has rigidity and stability because of the aryl ring and flexibility due to the carboxyl group, so it can be designed to assemble many novel microporous me- tal-organic coordinate polymer materials (MOCP) with transition metal[1～5]. In order to design and syn- thesize MOCP with specific framework structure for potential applications as functional materials, the ligand was decorated by bringing more substitutes to the aryl ring[…     

Solvation Effect of Li+ on the Voltammetric Properties of [PMo12O40]3−. Part 2: Comparative Studies on the Preferential Solvation in Acetonitrile+S and Acetone+S Mixtures

For [PMo₁₂O₄₀]^3?, the presence of Li⁺ produced a two‐electron wave at nearly the same potential as the first one‐electron wave in acetonitrile or acetone. The voltammetric behavior of [PMo₁₂O₄₀]^3? in a binary mixture of acetonitrile and solvent S was compared with those in a mixture of acetone and S. When the donor number (DN) of S>20, the first two‐electron wave was converted into one‐electron waves in such binary mixtures. The conversion occurred at lower mole fractions of S in an acetonitrile+S mixture than in an acetone+S mixture. The ⁷Li NMR results showed that the preferential solvating ability of Li⁺ with S was greater in the former mixture. A linear relationship was found between the iso‐solvation point x_iso(S) and the reciprocal of the difference between the DNs of S and acetonitrile, which gave the basis to explain the anomalies observed for a mixture of acetonitrile and H₂O.     

New designer drug, 2,5-dimethoxy-4-propylthio-beta-phenethylamine (2C-T-7): studies on its metabolism and toxicological detection in rat urine using gas chromatography/mass spectrometry

Studies are described on the metabolism and toxicological analysis of the phenethylamine-derived designer drug 2,5-dimethoxy-4-propylthio-beta-phenethylamine (2C-T-7) in rat urine using gas chromatography/mass spectrometry (GC/MS). The identified metabolites indicated that 2C-T-7 was metabolized by hydroxylation of the propyl side chain followed by N-acetylation and sulfoxidation and also by deamination followed by oxidation to the corresponding acid or by reduction to the corresponding alcohol. To a minor extent, 2C-T-7 was also metabolized by S-dealkylation followed by N-acetylation, S-methylation and sulfoxidation. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid-liquid extraction microwave-assisted acetylation allowed the detection of an intake of a dose of 2C-T-7 in rat urine that corresponds to a common drug users' dose. Assuming similar metabolism, the described STA procedure should be suitable for proof of an intake of 2C-T-7 in human urine.     

Synthesis and crystal structure of 7,7,10-trimethyl-7-silabenzo[a]anthrone

Skeletal isomerization of arylsilanes that occurs under conditions of catalytic dehydrocyclization and is accompanied by migration of the triorganosilyl group was additionally confirmed by dehydrocyclization of dimethyl(2,4-dimethylphenyl)(1-naphthyl)silane on chromium-containing oxide catalysts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2236–2239, December, 1997.     

Synthesis of 5,7,11 b,12-tetrahydro-isoindolo[2,1-b]isoquinolinium methiodides and theirStevens rearrangement

The title compounds5 were synthetized in two steps from the corresponding isoindolo[2,1–b]isoquinoline-5(7H)-ones3, obtained in high yields from 3-ethoxy-1H-isoindoles2 and homopthalic anhydrides1. TheStevens rearrangement of5 gave 2-methyl-2,3-dihydro-1H-isoindole-1-spiro-2-indanes6.

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Synthese von 5,7,11 b,12-Tetrahydro-isoindolo[2,1-b]isochinolinium Methiodiden und ihre Stevens-Umlagerung

Zusammenfassung Die Titelverbindungen5 wurden in zwei Stufen aus den entsprechenden Isoindolo[2,1–b]isochinolin-5(7H)-onen (3) dargestellt, die ihrerseits in hohen Ausbeuten aus 3-Ethoxy-1H-isoindolen (2) und Homophthalsäureanhydriden erhältlich sind. DieStevens-Umlagerung von5 führte zu 2-Methyl-2,3-dihydro-1H-isoindol-1-spiro-2-indanen (6).

     

The Regioselective Methylation of Polycyclic Aromatic Hydrocarbons through Tricarbonylchromium Coordination

Deprotonation, methylation, and air oxidation of polycyclic arenes coordinated to chromium(0), (η⁶-arene)Cr(CO)₃, produced ring-methylated products with high selectivity and in good yield. This procedure gave 3-methylbenz[a]anthracene from (η⁶-benz[a]anthracene)Cr(CO)₃, 3-methylphenanthrene from (η⁶-phenanthrene)Cr(CO)₃, 2-acetyl-6-methylphenanthrene from (η^6?2-acetylphenanthrene)Cr(CO)₃, and 3,7,12-trimethylbenz[a]anthracene from (η^6?7,12-dimethylbenz[a]anthracene)Cr(CO)₃.     

Stereoselectivity in Diphos Addition to Molybdenum Complex with Pyridine‐2‐thionate (pyS) and η3‐Methallyl Coordinated Ligands

The conformational isomers endo‐ and exo‐[Mo{η³‐C₃H₄(CH₃)}(η²‐pyS)(CO)(η²‐diphos)] (diphos: dppm = {bis(diphenylphosphino)methane}, 2 ; dppe = {1,2‐bis(diphenylphosphino)ethane}, 3 ) are prepared by reacting the double‐bridged pyridine‐2‐thionate (pyS) complex [Mo{η³‐C₃H₄(CH₃)}(CO)₂]₂(η¹:η²:μ‐pyS)₂, 1 with diphos in refluxing acetonitrile. Stereoselectivity of the methallyl, C₃H₄(CH₃), ligand improves the formation of the exo‐conformation of 2 and 3 . Orientations and spectroscopy of these complexes are discussed.     

Steric repulsion of polyoxyethylene groups for emulsion stability

Rapid coalescence was studied on liquid paraffin emulsion stabilized with a series of poly(oxyethylene) dodecyl ethers [C₁₂H₂₅ (EO),n=1, 2, 3, 4, 5, 6, 7, 8] and of poly(oxyethylene) nonylphenyl ethers [C₉H₁₉(EO) _n ,n=2, 4, 5, 6, 12]. The turbidity of emulsion was measured as a function of the solution pHs at constant ionic strength of 0.1 mol dm^–3.As a result, it was found that the emulsions (which were formed with C₁₂H₂₅(EO) _n surfactants having less than four oxyethylene groups, or with C₉H₁₉ (EO) _n surfactants having less than six oxyethylene groups) brought about rapid coalescence in the bulk pH between 2.03.5, which corresponded to the zero point of charges for the emulsions of the present systems. According to the Tadros treatment for emulsion flocculation, the total flocculation potennual was estimated as a function of the distance relative to the number of oxyethelene groups in the surfactants. The critical coalescence energy was obtained as –343 ×10^–19 J for the C₁₂H₂₅(EO) _n surfactants and –2.14×10^–19) J for the C₉H₁₉ (EO) _n surfactants. Furthermore, the formation of a hole for coalescence was estimated under the simple assumption that the coalescence was caused only by the energy dissipation.