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991.
Chen Xiao-Ming Wu Yu-Luan Tong Ye-Xiang Sun Ziming David N. Hendrickson 《Polyhedron》1997,16(24):1041
A novel tetranuclear terbium(III) complex [Tb4(OH)4(pybet)6(H2O)8][Tb4(OH)4(pybet)6(H2O)7 (NO3)](ClO4)14·6H2O has been synthesized and shown by X-ray crystallography to have a cubane-like Tb4(μ3-OH)4(μ2-carboxylato-O,O′)6 core. The ligand pybet is pyridinoacetate, C5H5+N-CH2CO2−. Magnetic susceptibility data were measured for this Tb4 complex in the range of 2.0–320 K and in fields of 1.0 G to 50.0 kG. It is concluded that either there is very weak antiferromagnetic exchange interaction (J = −0.015 cm−1) or there is a small crystal-field splitting of the 7F6 TbIII ground state. 相似文献
992.
Yang Jie Wu Shou Quan Huo Li Yang Chen Xia Du 《Journal of organometallic chemistry》1995,490(1-2):249-254
Three series of cyclomercurated ferrocenylimines (2-chloromercurio-ferrocenylimines) have been studied using 13C NMR spectroscopy. Good to excellent linear relationships have been found to exist between the chemical shifts of the carbon atoms in the ferrocenyl moiety and normal Hammett substituent constants σm and σp. The δ values of the iminyl carbon atoms show excellent linear correlations with the σ values. In three series of the ferrocenes, the sensitivity of the carbon atoms to the substituent effect is different, which is discussed in terms of the twist angle between the N-phenyl ring and the C---C=N---C plane. The relative sensitivity of the chemical shifts on different positions in ferrocenyl moiety to the substituent effect has also been presented. 相似文献
993.
Paul D. Beer Zheng Chen Philip A. Gale Jennifer A. Heath Rachel J. Knubley Mark I. Ogden Michael G. B. Drew 《Journal of inclusion phenomena and macrocyclic chemistry》1994,19(1-4):343-359
The synthesis, metal, ammonium and alkyl ammonium cation coordination chemistry and electrochemical recognition studies of new diester-and diamide-calix[4]arenediquinone receptors are described. In addition the synthesis and coordination properties of a novel diamide benzo-15-crown-5-calix[4]arene molecule is reported.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes. 相似文献
994.
Perham M Chen M Ma J Wittung-Stafshede P 《Journal of the American Chemical Society》2005,127(47):16402-16403
Protein recognition and binding play a fundamental role in living systems but sometimes also result in pathological aggregates. To probe the coupling between folding and binding in a homoheptameric system, we have characterized the time-resolved unfolding/disassembly mechanism of human co-chaperonin protein 10 (cpn10) by a combination of experimental and computational methods. The results from both approaches are in excellent agreement and make obvious that the kinetic process is three-state: an initial polypeptide-unfolding step, resulting in a non-native heptamer, is followed by a slower heptamer-dissociation step. This demonstrates that the barriers on the kinetic free-energy landscape are defined by thermodynamic stability. cpn10 is one of few, and the only heptameric, experimentally characterized system that follows the "fly casting scenario" of molecular recognition. 相似文献
995.
The introduction of a 5-trimethylsilyl group on the least hindered face of the diene thebaine was anticipated to favor attack by dienophiles from the alternate face, but only gave rise to a rearrangement product when treated with 3-butene-2-one at 110 °C. Reaction with the more reactive benzoquinone at lower temperature gave rise to a very slow reaction from the same face as the silyl group, indicating that a trimethylsilyl group does not sufficiently hinder this face to achieve reaction at the other face. 相似文献
996.
采用动态TG-DTG,研究了铁催化剂的制备方法、前驱化合物的 种类及 热处理对其在碳-氧反应中催化活性的影响。观察到在干混法制备催化剂时,所用铁盐分解温度越低活性越高。此外还发现,热处理可明显提高由分解温度高的含氧铁盐制备的 催化剂的活性,但对于不含氧铁盐和分解温度低的含氧铁盐无影响。 相似文献
997.
3,4—亚甲二氧基苯甲酸锡酯的合成及表征 总被引:3,自引:0,他引:3
3,4-亚甲二氧基苯甲酸及其取代物与三苯基氢氧化锡或二丁基化锡反应合成了5个锡酯,通过元素分析,IR和^1HNMR对其进行了表征。 相似文献
998.
999.
本文采用GF-AAS加平台技术,基体改进剂,测定了中药片仔癀,六味地黄丸中铬、铅和镉的含量,铬、铅和镉的线性范围分别为0-0.8ng/mL,0-50ng/mL,0-5ng/mL,回收率分别为102-103%,99-101%,97.5-98%,本方法简便快速、准确。 相似文献
1000.