The 1:2 Complex of Piperazine with Some Phenols:Hydrogen Bonding Pattern Involved in Transition States in Solution

Previous calorimetric and iR studiesl had showed that, in a system of secondary amineand unhindered phenol, hydrogen bonds of O--H---N and N--H---O concurred toappear. Fast proton exchange between proton donor and acceptor in solution is usualphenomenon 2-". Therefore, a novel model (Scheme l) for the I fZ complex of piperazine(Pip) respectively with phenol (Ph), 2-metylphenol (O-MPh), 4-metylphenol (P-MPh)(abbreviated generally as PiP' ZXPh) in solution is now established. As showed …     

吡啶甲酰硫脲嘧啶衍生物的合成及生物活性

酰基硫脲类化合物及其吡啶取代产物不仅是重要的有机合成中间体 ,且有优良的杀虫 ,除草 ,抗病毒 ,及植物生长调节等功效[1 - 3] 。为了寻找高活性的新药物 ,本文采用亚结构连接法 ,将吡啶杂环引入到含取代嘧啶环的酰基硫脲中 ,合成了8个含取代嘧啶环的β (或γ )吡啶甲酰硫脲 4ａ～4ｈ ,结构经ＩＲ、1 ＨＮＭＲ、ＭＳ和元素分析表征。初步生物活性测定结果表明 :目标化合物高效抑制双子叶植物 (如油菜 )的生长 ,而对单子叶植物 (如玉米 )的生长具有一定的促进作用。目标化合物的合成路线为 :表 1　化合物 4ａ～ 4ｈ Ｔａｂ 1　Ｃｏｍｐｏｕ…     

Synthesis and Structure of Vanadium—barium Complex of 2, 4, 6—Tripicolinato with 20—Member Macrocyclic Cavities

Recently, the thermal decomposition of heteronuclear complexes has become apromising method for the preparation of di- or tri-metallic oxides because the complex as precursor has the special microstructure, the controlled stoichiometry of the metals and lower decomposition temperature 1. In order to investigate Ba-V-O system, which has the special magnetic behavior 2, we synthesized the title complex as the precursor of this material. On the other hand, microporous constructions existing in…     

Fluorescence enhancement of the europium-yttrium-diphacinone-ammonia system

A study of the enhanced (ca. 100 ×) fluorescence intensity of the Eu³⁺-diphacinone-ammonia system by Y³⁺ was made using a colloidal suspension. The excitation and emission wavelengths were 330 and 612 nm, respectively. The fluorescence intensity was a linear function of the concentration of europium in the range 6.0 × 10^?11–8.0 × 10^?7 M. The detection limit was 8.0 × 10^?14 M. The standard addition method was used for the determination of europium in rare earth oxides, with satisfactory results.     

A new efficient route for the synthesis of 4,4′,6,6′-tetra(azido) azo- 1,3,5-triazine

A new method for the synthesis of 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine(TAAT)is described.The key intermediate 4,4′,6,6′- tetra(azido)hydrazo-1,3,5-triazine(TAHT)was synthesized by nucleophilic substitution in the case of sodium azide as nacleophile. N-Bromosuccinide(NBS)was used as oxidant to oxidize TAHT by a tractable operation under mild reaction condition.The target compound TAAT was obtained with a facile process and high overall yield of 81%.The structures of TAAT and its intermediates were identified by spectroscopic methods.     

催化剂制备工艺对PEMFC氧电极性能的影响

聚合物电解质膜燃料电池（PEMFC）具有高能量密度、运行温度较低、水热管理较为容易、稳定性较好等优点，可以应用在航天领域、潜艇、电动车、电站等领域，是目前燃料电池领域中令人关注的研究课题．在提高电池性能所作的各种尝试中，膜电极制备工艺的改进依旧是研究的重点［'1     

Polarity control and residual strain in ZnO epilayers grown by molecular beam epitaxy on (0001) GaN/sapphire

We report on the polarity control of ZnO grown by plasma assisted molecular beam epitaxy on Ga polar (0001) GaN/sapphire templates simply via the oxygen‐to‐Zn (VI/II) ratio during the growth of a thin nucleation layer at 300 °C. Following Zn pre‐exposure, the ZnO layers nucleated with low VI/II ratios (<1.5) exhibited Zn‐polarity. Those nucleated with VI/II ratios above 1.5, exhibited O‐polarity. Supported by scanning transmission electron microscopic imaging, we have unequivocally demonstrated that polarity inversion takes place without formation of any vertical inversion domains and within one monolayer of presumably non‐stoichiometric GaO_x formed at the ZnO/GaN interface. A direct correlation between polarity and strain sign of ZnO layers has been found. The Zn‐polar ZnO layers were under tensile biaxial strain, whereas the O‐polar material exhibited compressive strain. Moreover, the amount of residual strain varied linearly with VI/II ratio used during the low‐temperature nucleation layer growth. Strain control with VI/II ratio has been explained by the potential formation of Zn interstitials.     

Selective Oxytrifluoromethylation of Allylamines with CO2

Reported is the first oxy‐trifluoromethylation of allylamines with carbon dioxide (CO₂) using copper catalysis, thus leading to important CF₃‐containing 2‐oxazolidones. It is also the first time CO₂, a nontoxic and easily available greenhouse gas, has been used to tune the difunctionalization of alkenes from amino‐ to oxy‐trifluoromethylation. Of particular note, this multicomponent reaction is highly chemo‐, regio‐, and diastereoselective under redox‐neutral and mild reaction conditions. Moreover, these reactions feature good functional‐group tolerance, broad substrate scope, easy scalability and facile product diversification. The important products could also be formed with either spirocycles or two adjacent tetrasubstituted carbon centers.