中药黄芩及其混伪品的模糊聚类分析

采用模糊聚类分析法对黄芩及其混伪品进行了聚类分析,为中药材的质量鉴定提供了新方法。     

激光产生的钒硫簇离子的统计分布与结构探讨

以脉冲激光在高真空中溅射钒粉和硫粉的混合物，产生了一系列钒硫原子簇正负离子。根据对其实验记录的激光等离子体质谱进行分析，发现钒硫原子簇的化学键基本上是共价型的，对应于相同钒原子数目的正负离子的相对丰度分别符合于不同形式的对数正态分布。正离子的相对丰度随硫原子数的增加呈对数衰减，由此可以确定各种大小簇合物的簇骼与几何构型；负离子的相对丰度则基本上呈正常的正态分布，说明在簇骼上结合了不同数量硫原子的负离子之结构稳定性大致相近。在实验中还观察到一类硫原子含量较高的簇离子，其中的部分硫原子可能在本身成键形成环状的硫集团后，又与原来的簇骼结合，因而在硫原子数较多时它们的相对丰度符合另一条对数正态分布曲线。     

簇离子Mo_3S_4M~（n＋）中M与Mo成键作用及电子光谱（M＝Fe、Ni，n＝4；M＝Cu，n＝5）

应用ＩＮＤＯ／Ｓ半经验量子化学方法，对簇合物离子Ｍｏ３Ｓ和Ｍｏ３Ｓ４Ｍｎ＋（Ｍ＝Ｆｅ、Ｎｉ，ｎ＝４；Ｍ＝Ｃｕ，ｎ＝５）分别进行分子轨道计算。根据计算得到的簇离子中的原子表观电荷和成键指标，说明Ｆｅ、Ｎｉ、Ｃｕ＋与Ｍｏ３Ｓ成键作用的相对强度依次是Ｆｅ－Ｍｏ＞Ｎｉ－Ｍｏ＞Ｃｕ＋－Ｍｏ。比较了用含组态作用的ＩＮＤＯ／Ｓ方法计算得到的电子跃迁能与实验得到的电子吸收光谱值，并讨论了吸收峰归属情况。对于Ｍ为Ｆｅ、Ｎｉ的簇离子Ｍｏ３Ｓ４Ｍ４＋，最低能量的电子跃迁吸收峰起源于异金属间电荷转移跃迁（ＭＭ’ＣＴ）；而Ｍｏ３Ｓ４Ｃｕ（５＋）簇离子观察到的吸收峰主要是Ｍｏ３Ｓ芯的局域内电荷转移跃迁。根据理论计算结果，由Ｃｕ＋离子到Ｍｏ３Ｓ的电荷转移跃迁谱线，大约在４６０００ｃｍ－１以上才能观察到吸收峰。从Ｍｏ３Ｓ４Ｆｅ４＋次低能量吸收峰的实验值１６６００ｃｍ－１和理论值１６５００ｃｍ－１与Ｍｏ３Ｓ的最低能量吸收峰的实验值１６６００ｃｍ－１和理论值１６９００ｃｍ－１比较，表明无论从理论上或实验上都能证实簇离子Ｍｏ３Ｓ４Ｆｅ４＋在能量为１６６００ｃｍ－１处的吸收峰是起因于Ｍｏ３Ｓ芯的局域内电荷转移跃迁。     

~3Δ、~3Π、~3Σ~＋Ni—CO分子簇的从头算研究

用从头算研究了ｄ空穴位置不同对Ｎｉ—ＣＯ成键机制的影响。结果表明，Ｎｉ—ＣＯ键中σ／π接受作用的相对强弱，取决于Ｎｉ—ＣＯ簇所处的能态。σ空间电子云较π空间电子云弥散，因而Ｎｉ—ＣＯ簇的稳定性与σ空间电子云的排斥密切相关。随着Ｎｉ４ｐσ轨道上电子占据数的增加，Ｎｉ—ＣＯ稳定性减弱。比较了分子簇Ｎｉ—ＣＯ与ＮｉＣＯ分子及ＣＯ／Ｎｉ化学吸附体系之间的性质。     

Darstellung, 19F-NMR-spektroskopischer Nachweis und Untersuchung zur Bildung der metallgemischten Clusteranionen [(Mo6−nWnCl)F]2−, n = 0−6

Preparation, ¹⁹F NMR Spectroscopic Evidence and Study of the Formation of Metal-Mixed Cluster Anions [(Mo_6?nW_nCl )F ]^2?, n = 0?6 The complete system of metal-mixed octahedral cluster ions [(Mo_6?nW_nCl)F]^2?, n = 0?6, is prepared by tempering Mo powder with WCl₆ at 600°C. A mixture containing inclusively the geometric isomers (n = 2, 3, 4) all ten possible species is transferred into the tetra-n-butylammonium salts (TBA)₂[(Mo_6?nW_nCl)F]. In the ¹⁹F nmr spectrum the 24 expected signals are observed, assigned on the basis of their chemical shifts, multiplicities and intensities, and confirmed by a 2D-¹⁹F-¹⁹F COSY spectrum. From the integrated intensities the distribution of the different components is derived revealing a non-statistical formation, in that isomers with Mo…?Mo or W…?W atoms in trans-positions in comparision to those with mixed Mo…?W axes are favoured, and that especially the homoleptic compounds Mo₆ and W₆ are present to an over-average extent. Evaluation of ¹⁹F chemical shifts reveals that F bound to W which is in antipodal position to Mo resonates at higher field compared to F bound to W in a W…?W arrangement, caused by an increased shielding, which is synonymous to a positive antipodal-effect by Mo. Vice versa F bound to Mo with an antipodal W resonates at lower field compared with F bound to Mo in an Mo…?Mo arrangement caused by an increased deshielding and synonymous a negative antipodal-effect by W. The chemical shifts, resulting from antipodal-effects, are different for the compounds within the [(Mo_6?nW_nCl)F]^2? - system. The difference of the antipodal effect of successive substitution products results in characteristic values designated as antipodal shift constants, depending on the kind of substituents, which is valid for other cluster systems, too.     

原子簇P12（D3d）的理论研究

利用Ｇａｕｓｓｉａｎ－９２程序在６－３１Ｇ基组下优化Ｐ１２（Ｄ３ｄ）构型，研究了３Ｐ４（Ｔｄ）→Ｐ１２（Ｄ３ｄ）的相对能量，计算结果为△Ｅ＝Ｅｐ１２（Ｄ３ｄ）－３Ｅｐ４（Ｔｄ）＝－７９．８４４ｋＪ／ｍｏｌ，优化Ｐ１２（Ｄ３ｄ）获得的Ｐ－Ｐ键键长接近于实验测得的Ｐ－Ｐ单键键长，并进一步在该基组下计算了Ｐ１２（Ｄ３ｄ）原子簇的振动频率，得到的全部为正频率，表明原子簇Ｐ１２的Ｄ３ｄ构型是位能面上的稳定点     

P14原子簇的理论研究

以Ｐ_２、Ｐ_４（Ｔｄ）、Ｐ_８（Ｃ_（２ｖ））及Ｐ_（１０）（Ｃ_（２ｖ））为结构单元设计了Ｐ_２＋Ｐ_４（Ｔ_ｄ）＋Ｐ_８（Ｃ_（２ｖ））→Ｐ_（１４）（Ｃ_ｓ）（Ａ）、Ｐｓ（Ｃ_（２ｖ）＋３Ｐ_２→Ｐ_（１４）（Ｃ_（２ｖ））（Ｉ）（Ｂ）、Ｐ_（１０）（Ｃ_（２ｖ）＋２Ｐ_２→Ｐ１４（Ｃ_（２ｖ））（Ⅱ）（Ｃ），利用从头算Ｇａｕｓｓｉａｎ－９４程序，选择６－３１Ｇ基组，对４种结构单元及Ｐ_（１４）原子簇的３种几何构型Ｃｓ、Ｃ_（２ｖ）（Ⅰ）、Ｃ_（２ｖ）（Ⅱ）进行全优化。相对能量的计算结果表明，Ｐ_（１４）（Ｃ_ｓ）与Ｐ_（１４）（Ｃ_（２ｖ））（Ⅰ）构型稳定。进一步设计（７／２）Ｐ_４（Ｔ_ｄ）→Ｐ_（１４）（Ｄ）及７Ｐ_２→Ｐ_（１４）（Ｅ），其相对能量表明，Ｐ_（１４）（Ｃ_ｓ）构型是稳定的．磷与磷连结单键键长范围为０．２２０～０．２２８ｎｍ，双键键长范围为０．２００～０．２０２ｎｍ，与实验结果大体相当。     

Atomic force microscopy imaging of novel macromolecular species,nanosponges, and their clusters

Atactic polystyrene of M = 330,000 Da and M_w/M_n = 1.04 was subjected to a complete chloromethylation. By heating the chloromethyl polystyrene with SnCl₄ in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, called “nanosponges.” These species have a molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges display a tendency to reversibly self‐assemble into regular clusters. Preparative size‐exclusion chromatography isolates a fraction consisting predominantly of spherical clusters that are composed of 13 subunits and acquire a molecular weight of approximately 5.0 × 10⁶ Da and a diameter of 45 nm. Scanning atomic force microscopy (AFM) provides images of individual nanosponges, N = 13 clusters, as well as higher spherical clusters. The regular spherical species most probably belong to the cluster series N = 1 + ∑(10n² + 2), where n is the number of shells around the central nanosponge. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1451–1455, 1999     

［Mo_3（μ_3－O）（μ－Cl）_3（μ－O_2CR）_3Cl_3］~－系列三核钼的电化学及热化学性质的研究

用循环伏安法研究了［Ｍｏ_３ＯＣｌ_６（Ｏ_２ＣＲ）_３］－（其中Ｒ＝ＣＨ_３，Ｈ，ＣＨ_２Ｃｌ）系列三核钼簇合物在ＣＨ_３ＣＮ和ＤＭＦ溶剂中的电化学行为，并用差热－热重手段研究了它们的热稳定性和热分解过程的可能机理。结果表明在不同溶剂中它们有相似的二对氧化还原峰，而且在同一溶剂中随着Ｒ基团吸电子能力的增强，相应的第一氧化还原电位值向正向移动。当Ｒ＝ＣＨ_３，Ｈ时，它们的起始分解温度分别为２６５℃和２１０℃，即同样随着Ｒ基团吸电子能力的增强，起始分解温度降低。     

Zur Existenz tetraedrischer Polykationen [In5]7+ in der Verbindung „Na23In5O15”︁ (=Na24In5O15?) einem ungewöhnlichen Oxidationsprodukt der intermetallischen Phase NaIn

Tetrahedral Polycations [In₅]⁷⁺ in ‘‘Na₂₃In₅O₁₅”︁”︁ (=Na₂₄In₅O₁₅?) an Unusual Oxidation Product of the Alloy NaIn The already published, red-transparent, air sensitive, cubic compound Na₂₄In₅O₁₅ (a = 1107.7 pm, Z = 2, I43m) is an intermediate oxidation product of the intermetallic phase NaIn. It is reinvestigated with respect to the question whether it contains the tetrahedral polycation [InIn₄]⁶⁺ or [InIn₄]⁷⁺. In the latter case the chemical composition would be Na₂₃In₅O₁₅ instead of Na₂₄In₅O₁₅ and the polycation would be in accordance with the Zintl-Klemm concept. Na₂₄In₅O₁₅ is prepared in single phased samples for the first time and investigated by means of the Rietveld refinement technique of X-ray powder data. Based on the results of the Rietveld refinements and new single crystal data in comparison to the published values we note anomalies in the occupancies of the Na positions and a pronounced anisotropy in the thermal parameters of one oxygen position. These investigations together with results obtained by analytical scanning electron microscopy, Extended Hückel and MAPLE calculations give strong evidence for the assumption of [InIn₄]⁷⁺ instead of [InIn₄]⁶⁺ and the associated correct composition Na₂₃In₅O₁₅. The problems of a reliable characterization of this unique compound are discussed.