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191.
192.
Jin-long Wu Zhen-ya Zeng Lan-hua Wei Ling-zhi Meng Ting-xian Yang 《Tetrahedron》2004,60(19):4309-4314
Three new neutral receptors (1, 2 and 3) containing thiourea and amide groups were synthesized by simple steps in good yields. The binding properties for anions of 1, 2 and 3 were examined by UV-vis, fluorescence, and 1H NMR spectroscopy. Receptors 1, 2 and 3 all had a better adipate anion selectivity by comparison with other dicarboxylate anions. The association constants of 1, 2 and 3 with adipate were higher as compared to other anions (malonate, succinate, glutarate). In particular, a distinct color change was observed from light yellow to orange-red upon addition of adipate to the solution of 1 in DMSO. The UV-vis and fluorescence data indicate that a 1:1 stoichiometry complex is formed between compound 1, 2 or 3 and dicarboxylate anions through hydrogen bonding interactions. 相似文献
193.
Wei Zeng 《Tetrahedron letters》2006,47(33):5923-5926
Vanadium(V) (5 mol %) and hydroxamic acid ligand (45 mol %) were found to promote the selective tert-butyl hydroperoxide-mediated oxidation of allylic and propargylic alcohols to the corresponding aldehydes and ketones. 相似文献
194.
生物,环境样品和食品中铅的痕量分析 总被引:2,自引:0,他引:2
主要根据近七年来发表的有关论文,综述了我国生物、环境样品和食品中铅和痕量分析技术进展,内容包括分子光谱、原子光谱、电化学和其他分析方法,以及联用技术和前处理等方面,收集文献393篇。 相似文献
195.
Xiaoqing Zeng Maofa Ge Zheng Sun Jiang Bian Dianxun Wang 《Journal of Molecular Structure》2007,840(1-3):59-65
Gaseous nitryl azide N4O2 is generated by the heterogeneous reaction of gaseous ClNO2 with freshly prepared AgN3 at −50 °C. The geometric and electronic structure of the molecule in the gas phase has been characterized by in situ photoelectron spectroscopy (PES) and quantum chemical calculations. The experimental first vertical ionization energy of N4O2 is 11.39 eV, corresponding to the ionization of an electron on the highest occupied molecular orbital (HOMO) {4a″(πnb(N4–N5–N6))}−1. An apparent vibrational spacing of 1600 ± 60 cm−1 (νasO1N2O3) on the second band at 12.52 eV (πnb(O1–N2–O3)) further confirms the preference of energetically stable chain structure in the gas phase. To complement the experimental results, the potential-energy surface of this structurally novel transient molecule is discussed. Both calculations and spectroscopic results suggest that the molecule adopts a trans-planar chain structure, and a five-membered ring decomposition pathway is more favorable. 相似文献
196.
复合氨基酸微量元素螯合物制备新工艺的研究 总被引:19,自引:0,他引:19
本文报道了以废羽毛为原料,采用矿物质硫酸盐的制备与中和脱酸、螯合反应结合的新工艺,以金属盐类作催化剂和硫酸水解法,制得了复合氨基酸微量元素螯合物。复合氮基酸生成率为71.7%,微量元素螯合率达到98%以上。该工艺简单易行,生产成本低。 相似文献
197.
Hongyang Su Lanlan Chen Yizhen Chen Prof. Rui Si Yuting Wu Xiaonan Wu Dr. Zhigang Geng Prof. Wenhua Zhang Prof. Jie Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(46):20591-20596
Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH3). Reported herein is a novel Fe-MoS2 catalyst with Fe atomically dispersed onto MoS2 nanosheets, imitating natural nitrogenase, to boost N2 electroreduction into NH3 at room temperature. The Fe-MoS2 nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mgcat.−1 h−1 for NH3 at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N2 was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS2 with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N2 into NH3. This work provides new ideas for the design of catalysts for N2 electroreduction and strengthens the understanding about N2 activation over Mo-based catalysts. 相似文献
198.
肾上腺素在脱氧核糖核酸修饰金电极上的电化学行为及铅离子的影响 总被引:2,自引:0,他引:2
用干燥/吸附法制备了脱氧核糖核酸(DNA)修饰金电极(DNA/Au),采用循环伏安法、计时库仑法、微分脉冲伏安法、交流阻抗以及紫外光谱法研究了肾上腺素(EP)在该电极上的伏安行为及Pb^2 产生的影响。结果表明:在5mmol/L pH7.7Tris底液中,EP在DNA/Au上产生一不可逆的氧化峰(Ep=0.16V)。该峰较EP在裸金电极上的峰(Ep=0.11V)电位为正,灵敏度高。在有Pb^2 存在时,峰电位负移,峰高增大。微分脉冲峰高与EP浓度在0.5-75μmol/L范围内呈线性关系。氧化峰为扩散控制为主并兼有弱的吸附性。本文还探讨了其电极反应的机理,认为在无Pb^2 的情况下,EP与DNA的结合是EP嵌入DNA中为主并兼有一定程度的静电吸附。有Pb^2 存在的情况下EP是以EP-Pb^2 嵌入DNA的双螺旋结构中和通过静电吸附在DNA骨架上的Pb^2 为桥梁与DNA结合。 相似文献
199.
A simple method was used to prepare a "switchable" electrode surface by using self-assembled monolayers of dodecanethiol on a gold electrode. The dodecane-modified electrode was electrochemically inactive until the monolayer was soaked in solutions of 1,10-phenanthroline or 2,2'-bipyridine. The electroactive form of the electrode could be reverted back to the nonelectroactive form by rinsing the electrode. Surface IR results showed that both dodecanethiol and 1,10-phenanthroline exist in the mixed monolayer. 相似文献
200.
(E)/(Z)-Isomeric allylic carbamate esters were deprotonated by n-butyllithium/(−)-sparteine in toluene. Trapping experiments with chlorotrimethylsilane afforded the α-substitution products, with (R)-configuration, revealing that the pro-S proton is removed predominantly to form the corresponding (S)-lithium·(−)-sparteine derivatives; kS/kR>15:1 and >7:1, respectively. A slow (S)→(R)-epimerization occurs at −78 °C (T1/2>60 min). The allylic double bond is stable to (Z)-(E) isomerization under these conditions. 相似文献