钛、玻璃碳基体中离子注人镍的电化学性能

钛、玻璃碳基体中离子注入5×10~(16)×10~(1(?)Ni~+离子cm~(-2).在30%KOH溶液中测试这些电极对氢析出反应的电催化性能.结果表明,离子注入电极的催化活性优于未注入的钛、玻璃碳基体.由极化测量求得动力学参数j、b和E.这些数据表明,在离子注入电极上,氢析出反应的速度决定步骤与镍电极相似,由电化学放电步骤控制。AES测量表明,镍在钛基体中的深度分布近似高斯分布,在阴极极化过程中,注入的镍没有损失,但明显地移向深处.用XPS研究注入前后Ni_(2p)和Ti_(2(?))电子结合能所产生的位移表明,离子注入可能在基体表面形成合金.     

Theoretical studies on the binding affinities of β-cyclodextrin to small molecules and monosaccharides

Equilibrium geometries and electronic structures of complexes between β-cyclodextrin (β-CD) and some small molecules as well as monosaccharides were investigated by Austin Model 1 (AM1) to obtain binding energy of the complexes. It was indicated that β-CD could bind the structurally similar solvent molecules and monosaccharides because of the negative binding energy of the complexes, and especially could show the chiral binding ability to monosaccharides with more hydroxyl groups, due to its chiral characteristics. The complexes were stabilized by the hydrogen bonding between β-CD and guests. Based on the AM1 optimized geometries, the IR spectra were calculated by AM1 method. Vibration frequencies of O-H bonds in the guests were red-shifted owing to the weakening of the O-H bonds with the formation of the complexes.     

Studies toward the synthesis of phomactin A. An approach to the macrocyclic core

An approach to the macrocyclic core of phomactin A is described. Central to this strategy is the use of a cis-fused oxadecalin intermediate, prepared using the dihydropyrone Diels-Alder reaction. The conformational bias inherent to this system is then used to facilitate macrocycle formation via an intramolecular B-alkyl Suzuki coupling.     

Evaluating adsorption ability of granite to radioselenium by chemical sequential extraction

A good understanding of the migration of selenite, Se(IV), through deep granitic layers depends on a good understanding of the geochemistry of these layers. Chemical sequential extraction is applied herein to evaluate the ability of granite to adsorb Se(IV) in DW, GW and SW systems. The experimental results indicate that the removal of crystalline Fe oxides reduces the adsorption of Se(IV), suggesting its importance in granite. The normalized concentrations of Se(IV) adsorbed onto crystalline Fe oxides is approximately 0.0301, 0.0330 and 0.0335 mole Se(IV) adsorbed/mole of Fe in DW, GW and SW systems. Kinetic adsorption experiments are conducted to elucidate the results of the chemical sequential extraction. Both the treated and the untreated granite take the same time to reach their equilibrium, suggesting that crystalline Fe oxides dominate the adsorption of Se(IV). Meanwhile, the one-site model suffices to simulate the kinetics of adsorption.     

Syntheses and structures of the first heavy-alkali-metal tris(trimethylsilyl)germanides

The first heavy-alkali-metal tris(trimethylsilyl)germanides were obtained in high yield and purity by a simple one-pot reaction involving the treatment of tetrakis(trimethylsilyl)germane, Ge(SiMe3)4, with various alkali metal tert-butoxides. The addition of different sizes of crown ethers or the bidentate TMEDA (TMEDA=N,N,N',N'-tetramethylethylenediamine) provided either contact or separated species in the solid state, whereas in aromatic solvents the germanides dissociate into separated ions, as shown by 29Si NMR spectroscopic studies. Here we report on two series of germanides, one displaying M-Ge bonds in the solid state with the general formula [M(donor)n Ge(SiMe3)3] (M=K, donor=[18]crown-6, n=1, 1; Rb, donor=[18]crown-6, n=1, 4; and M=K, donor=TMEDA, n=2, 6). The silicon analogue of 6, [K(tmeda)2Si(SiMe3)3] (7) is also included to provide a point of reference. The second group of compounds consists of separated ions with the general formula [M(donor)2][Ge(SiMe3)3] (M=K, donor=[15]crown-5, 2; M=K, donor=[12]crown-4, 3; and M=Cs, donor=[18]crown-6, 5). While all target compounds are highly sensitive towards hydrolysis, use of the tridentate nitrogen donor PMDTA (PMDTA=N,N,N',N',N'-pentamethyldiethylenetriamine) afforded even more reactive species of the composition [K(pmdta)2Ge(SiMe3)3] (8). We also include the silanide analogue [K(pmdta)2Si(SiMe3)3] (9) for sake of comparison. The compounds were typically characterized by X-ray crystallography, and 1H, 13C, and 29Si NMR and IR spectroscopy, unless extremely high reactivity, as observed for the PMDTA adducts 8 and 9, prevented a more detailed characterization.     

A Stereoselective Preparation of 1,2,7-Triazabicyclo[3.3.0]oct-2-enes

5-(Alkylamino)methyl-2-pyrazolines react with ketones or aldehydes to give 1,2,7-triazabicyclo-[3.3.0]oct-2-enes in high yields. The reaction gives only one diastereomer with various aldehydes, except for CH₃CHO.     

Platelet Aggregation Inhibitor from Ganoderma lucidum

Lucidenic acid A ( 1 ) and a new lactone, lucidenolactone ( 2 ) were isolated from the fruiting bodies of Ganoderma lucidum. Their structures were elucidated by spectroscopic method and single-crystal X-ray analysis. Lucidenolactone ( 2 ) showed significant antiplatelet aggregation activity. The NMR spectral data of lucidenic acid A were also reassigned.     

桃柱螟性信息素的立体选择性合成

分别以10-十一碳烯酸和丙炔醇为起始原料,通过炔化物路线(第1个中间体是10-十一碳炔醇-1(5),第2个中间体是10-十六碳炔醇-1(8))分别立体选择性合成了桃柱螟性信息素成分(E)-10-十六碳烯醛(1)和(Z)-10-十六碳烯醛(2)。