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101.
Susan Robertson David Ellis Georgina M. Rosair Alan J. Welch 《Journal of organometallic chemistry》2003,680(1-2):286-293
The reaction of the labelled carborane ligand [3-Et-7,8-Ph2-7,8-nido-C2B9H8]2− with a source of {Pt(PMe2Ph)2}2+ affords non-isomerised 1,2-Ph2-3,3-(PMe2Ph)2-6-Et-3,1,2-closo-PtC2B9H8 (1). The analogous reaction between [3-F-7,8-Ph2-7,8-nido-C2B9H8]2− and {Pt(PMe2Ph)2}2+ yields 1,8-Ph2-2,2-(PMe2Ph)2-4-F-2,1,8-closo-PtC2B9H8 (3). Compound 1 has a heavily slipped structure (Δ 0.72 Å), which to some degree obviates the need for C atom isomerisation. However, that it is a kinetic product of the reaction is evident from the fact that it reverts to isomerised 1,8-Ph2-2,2-(PMe2Ph)2-4-Et-2,1,8-closo-PtC2B9H8 (2) slowly at room temperature but more rapidly with gentle warming. The heteroatom and labelled-B atom positions in the isomerised compounds 2 and 3 may be explained most simply by the rotation of a CB2 face of an intermediate based on the structure of 1. Compounds 1–3 were characterised by a combination of spectroscopic and crystallographic techniques. 相似文献
102.
有机官能化MSU-x孔分子筛的界面特征 总被引:5,自引:0,他引:5
MSU- x是自 M41S系列介孔分子筛问世以来所合成的另一类新型介孔分子筛材料 ,它具有三维立体交叉排列的 " worm- like"孔道结构特征及采用中性模板剂、廉价无毒等诸多合成优点 [1~ 4],有着潜在的应用价值 .为了改善纯硅的介孔材料的表面和孔道性质 ,扩大其应用领域 ,除了在骨架引入金属离子或在其孔道中负载催化活性物质外 ,对介孔材料进行有机官能化制备无机-有机杂化材料改善其骨架和孔道性质是当前研究的热点之一 [5].正是由于活性有机基团的存在 ,使得这些材料可直接用于催化反应 ,或作为中间介质成为其它络合离子的主体 .由于有机基… 相似文献
103.
104.
FlorianC. Stintzing Florian Kugler Reinhold Carle Jürgen Conrad 《Helvetica chimica acta》2006,89(5):1008-1016
Due to their inherent liability towards highly acidic conditions previously considered to be a prerequisite for data acquisition, betaxanthin structure dereplication by NMR spectroscopy has been scarcely reported and was, hitherto, exclusively based on 1H‐NMR data interpretation. Applying only slightly acidic conditions, we herein report the first 13C‐NMR data of two betaxanthins, i.e., indicaxanthin ( 1 ), isolated from yellow‐orange cactus pear fruits (Opuntia ficus‐indica [L.] Mill . cv. ‘Gialla’), and of miraxanthin V ( 2 ) from yellow Swiss chard petioles (Beta vulgaris L. ssp. cicla [L.] Alef . cv. ‘Bright Lights’), as derived by gHSQC‐ and gHMQC‐NMR experiments and inverse detection. 相似文献
105.
采用稳态吸收和荧光光谱、圆二色谱和皮秒时间分辨荧光光谱手段, 研究了5,10,15,20-四[4-(N-甲基吡啶)]卟啉(TMPyP4)与腺嘌呤(A)、鸟嘌呤(G)、胸腺嘧啶(T)和胞嘧啶(C)等4种碱基, 以及相应的核苷、核苷酸和单链DNA的结合能力和光谱学性质. 研究结果发现, 嘌呤与TMPyP4的结合能力比嘧啶的强. 对于某一碱基系列, 结合能力强弱顺序依次为: 碱基~核苷<核苷酸<单链DNA. 时间分辨荧光谱研究发现, 除鸟嘌呤外, 核酸和TMPyP4复合物的荧光动力学均含有快(1~2 ns)和慢(约10 ns)两个衰减过程, 它们分别是由激基复合体和环境极性对激发态TMPyP4分子的影响所致. 单链DNA能诱导TMPyP4产生诱导圆二色信号, 而单分子(碱基、核苷、核苷酸)则无此功能. 相似文献
106.
Juan Méndez-Vivar 《Journal of Sol-Gel Science and Technology》2006,38(2):159-166
Sols composed of dibutyltin dilaureate (DTL) and tetraethyl orthosilicate (TEOS) were prepared using a mixture of methyl ethyl
ketone (MEK) and acetone as the solvent in order to study the interaction between the oligomeric Sn and Si species. The hydrolysis
molar ratio r (r=nH2O/nM (M: Si, Sn or Si+Sn) was 2. The use of an acid or basic catalyst was avoided, as the sols are intended to be used in
the formulation of potential stone consolidants. The sols were studied by several spectroscopic techniques including Small
Angle X-ray Scattering (SAXS), 29Si and 119Sn NMR, Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD). According to the spectroscopic results
the lauric acid produced by the hydrolysis of DTL modifies the condensation path of the Si species, leading to the formation
of two types of oligomeric chains: linear swollen and multiparticle diffusion-limited aggregates, depending on the molar ratio
Sn/Si. The 29Si NMR results indicated that the hydrolysis of DTL catalizes the condensation of the Si species, giving as a result higher
condensation extents of the Si species in the Sn-Si sols compared to a pure Si sol. Based on the Radial Distribution functions
(RDF) and the FTIR results, heterocondensation occurred. 相似文献
107.
药物不良反应的特点与预防 总被引:4,自引:0,他引:4
刘劲威 《广东微量元素科学》2003,10(11):65-67
药物不良反应已成为全社会关注的热点,及时了解有关不良反应的情况并采取必要的预防措施,以保证患者用药安全,维护患者身体健康是医务工作者刻不容缓的任务。 相似文献
108.
109.
Jakub Čížek Ivan Procházka Radomír Kužel Rinat K. Islamgaliev 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):873-887
Summary. Ultra-fine grained (UFG) Cu (grain size 80 nm) containing 0.5 wt.% Al2O3 nanoparticles (size 20 nm) was prepared by high pressure torsion (HPT). Positron lifetime spectroscopy was employed to characterize
the microstructure of this material, especially with respect to types and concentration of lattice defects. The evolution
of microstructure with increasing temperature was studied by positron lifetime spectroscopy and X-ray diffraction measurements.
The thermal stability of the Cu + 0.5 wt.% Al2O3 nanocomposite was compared with that of pure UFG Cu prepared by the same technique. The processes taking place during thermal
recovery of the initial nanoscale structure in both studied materials are described.
Received October 5, 2001. Accepted (revised) December 20, 2001 相似文献
110.