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951.
952.
Li CY Zhang XB Dong YY Ma QJ Han ZX Zhao Y Shen GL Yu RQ 《Analytica chimica acta》2008,616(2):214-221
A porphyrin derivative (1), containing two 2-(oxymethyl)pyridine units has been designed and synthesized as chemosensor for recognition of metal ions. Unlike many common porphyrin derivatives that show response to different heavy metal ions, compound 1 exhibits unexpected ratiometric fluorescence response to Zn2+ with high selectivity. The response of the novel chemosensor to zinc was based on the porphyrin metallation with cooperating effect of 2-(oxymethyl)pyridine units. The change of fluorescence of 1 was attributed to the formation of an inclusion complex between porphyrin ring and Zn2+ by 1:1 complex ratio (K = 1.04 × 105), which has been utilized as the basis of the fabrication of the Zn2+-sensitive fluorescent chemosensor. The analytical performance characteristics of the proposed Zn2+-sensitive chemosensor were investigated. The sensor can be applied to the quantification of Zn2+ with a linear range covering from 3.2 × 10−7 to 1.8 × 10−4 M and a detection limit of 5.5 × 10−8 M. The experiment results show that the response behavior of 1 to Zn2+ is pH-independent in medium condition (pH 4.0-8.0) and show excellent selectivity for Zn2+ over transition metal cations. 相似文献
953.
通过色谱方法, 从复杂的穿心莲内酯硫酸酯化反应体系中分离获得4个新的穿心莲内酯衍生物, 应用谱学方法进行了表征. 主要利用1H NMR, 13C NMR, DEPT, 1H-1H COSY, HSQC, HMBC及NOSEY等1D和2D NMR技术, 并通过与母体化合物NMR数据的对比分析, 鉴定这4个化合物分别为3,19-二羟基-8,11,13-赖百当三烯-15,16-内酯(1), 3-羟基-8,11,13-赖百当三烯-15,16-内酯-19-硫酸酯(2), 8,11,13-赖百当三烯-15,16-内酯-3,19-二硫酸酯(3), 3-羟基- 8(R)-12(S)-8(12)-环氧-13-赖百当烯-15,16-内酯-19-硫酸酯(4). 相似文献
954.
Dielectric monitoring of the adsorption or release process of salicylic acid (SA) by chitosan membrane shows that the dielectric spectra of the chitosan membrane/ SA solution systems change regularly in the adsorption or release process. By analyzing the regularity, a new mechanism for the relaxations is proposed. The concentration polarization layer (CPL) caused by SA adsorption or release is confirmed to be essential for the dielectric relaxations. The changes of the spectra with time are explained by account of the relationship between CPL properties and dielectric strength. Based on this relaxation mechanism, a theoretical method can be established to calculate dynamical parameters of inner structure of the adsorption or release systems from their dielectric spectra. Therefore, dielectric spec- troscopy is demonstrated to be a promising method for estimating interfacial distribution of ionic sub- stances and their binding to membrane in a non-invasive way. 相似文献
955.
Phenolic compounds extracted from extra virgin olive oil have attracted considerable recent attention. One of the components, (-)-oleocanthal (1), an inhibitor of the COX-1 and COX-2 enzymes, possesses similar potency as the NSAID ibuprofen. In this, a full account, we disclose the first- and now second-generation syntheses of both enantiomers of the oleocanthals, as well as the first synthesis of the closely related (-)-deacetoxy-oleuropein aglycone and a series of related analogues for structure activity studies. To demonstrate the utility of the second-generation synthesis, multigram quantities of (-)-oleocanthal were prepared in 10 steps (14% overall yield) from commercially available D-lyxose. 相似文献
956.
Palladium nanocrystals bound by {110} or {100} facets: from one pot synthesis to electrochemistry 总被引:1,自引:0,他引:1
A facile one-pot tactic is developed for the selective synthesis of either rhombic dodecahedral or cubic Pd nanocrystals with high yields. By applying a mild cleaning process, we establish for the first time reasonable and distinct electrochemical features corresponding to {110} or {100} facet predominated Pd nanocrystals. 相似文献
957.
硫酸化氧化锆固体超强酸 总被引:1,自引:0,他引:1
硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。 相似文献
958.
Zhi-Yong HanRui Guo Pu-Sheng WangDian-Feng Chen Han XiaoLiu-Zhu Gong 《Tetrahedron letters》2011,52(45):5963-5967
An asymmetric cyclization of alkynols triggered addition of azlactones catalyzed by a combined catalyst system consisting of a chiral gold phosphate and a phosphoric acid produces conformationally restricted amino acid precursors bearing vicinal quaternary stereogenic centers in high levels of stereoselectivity. 相似文献
959.
960.