C_(60)离子束撞击固体表面的坍塌沉积(Ⅰ)共焦显微拉曼光谱研究

为了研究C60的结构特性，我们最近在实验中将加这后的C60离子束沉积在固体表面，对其沉积后的形态进行了共焦显微拉曼光谱的表征．在记录的光谱中已检测不出C60原有的特征谱问，说明C60离子在高速憧击固体表面后，已经完全失去了原有的球状构型．C60的t）［R实验在自制的串级飞     

Ph2SO/Tf2O: a powerful promotor system in chemoselective glycosylations using thioglycosides

Diphenylsulfoxide in combination with triflic anhydride provides a very potent thiophilic glycosylation promotor system, capable of activating disarmed thioglycosides. The usefulness of this novel thiophilic activator is illustrated in a successful chemoselective glycosylation sequence in which the donor thioglycoside in the first condensation step may be either armed or disarmed. [reaction: see text]     

Ecdysteroid glycosides: identification, chromatographic properties, and biological significance

Ecdysteroid glycosides are found in both animals and plants. The chromatographic behavior of these molecules is characteristic, as they appear much more polar than their corresponding free aglycones when analyzed by normal-phase high-performance liquid chromatography (HPLC), whereas the presence of glycosidic moieties has a very limited (if any) impact on polarity when using reversed-phase HPLC. Biological activity is greatly reduced because the presence of this bulky substituent probably impairs the interaction with ecdysteroid receptor(s). 2-Deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, which has been isolated from the dried aerial parts of Silene nutans (Caryophyllaceae), is used as a model compound to describe the rationale of ecdysteroid glycoside purification and identification.     

Preparation and Characterization of Nanoscopic Organic Semiconductor of Oxovanadium Phthalocyanine

Nanoscopic particles of oxovanadium phthalocyanine (VOPc, phase-II) with different particle sizes are prepared by aggregation of VOPc molecules in the presence of surfactants for the first time. A size effect in the region of nanoscale was observed in the UV-visible spectra. The photoconductivity of the nanoscopic VOPc is much higher than that of bulk VOPc. Copyright 1999 Academic Press.     

110K铋基超导相形成的组成条件

Bi-Sr-Ca-Cu-O超导材料中存在110K和80K2个超导相。其组成是Bi_2Sr_2Ca_2Cu_3O_y和Bi_2Sr_2CaCu_2O。但迄今为止,在按2223组成比合成的未掺杂Bi系超导材料中从未得到过纯的110K相,也未见过组成为2223,零电阻温度在100K以上材料的报道。为了探索形成110K相的最佳条件,本文以2223组成比为参考,合成了5个系列材料:Bi_xSr_2Ca_2Cu_3O_y,Bi_2Sr_xCa_2Cu_3O_y,Bi_2Sr_2Ca_xCu_3O_y,Bi_2Sr_2Ca_2Cu_xO_y,Bi_i Sr_uCa_yCu_wO_s。     

Quantification of tripdiolide in human whole blood by liquid chromatography coupled with atmospheric pressure chemical ionization tandem mass spectrometry

A liquid chromatographic-tandem mass spectrometric (LC-MS/MS) assay was developed and validated to determine tripdiolide in human whole blood using dexamethasone acetate as an internal standard (I.S.). Liquid-liquid extraction with ethyl acetate was used to isolate them from the biological matrix. Detection was performed on a mass spectrometer coupled with a negative atmospheric pressure chemical ionization (APCI) in the multiple-reaction monitoring (MRM) mode. The calibration curve was linear (r² = 0.9973) in the concentration range of 0.5-100.0 ng/mL in human whole blood with a lower limit of quantification of 0.5 ng/mL. Intra-day and inter-day relative standard deviations (R.S.D.s) were less than 7.0 and 10.1%, respectively. Extraction recoveries of tripdiolide ranged from 80.5 to 90.1%. This assay can be used to determine trace tripdiolide in human whole blood.     

硼离子对铕掺杂SiO2干凝胶发光性能的影响

采用溶胶-凝胶法制备了Al单掺和B，Al共掺的Eu掺杂SiO2干凝胶。利用荧光光谱、IR，XRD，DSC，TG／DTG等技术研究了硼离子、退火温度对样品发光性质的影响。经500℃以上退火处理用248nm激发的样品，产生Eu^3＋离子^5D0→^7FJ的特征发射，^5D0→^7F1的跃迁分裂为两个峰。比较615nm处的发光强度，掺硼酸样品的发光强度是不加硼酸发光强度的3．3倍。这是因为B离子的加入，在材料中形成了Si—O—B键，破坏了网络的对称性，加强了Eu^3＋的红光发射。当退火温度上升到850℃用350nm激发时，样品有很强的Eu^2＋蓝光发射。Al单掺的发射中心在437nm处，发射半峰宽约为70nm，而B，Al共掺样品的发光中心蓝移到425nm处，单掺样品的蓝光强度几乎是共掺样品强度的2倍。这是由于硼酸的加入改变了基质的网络结构，从而导致单掺和共掺样品发射峰位和强度的改变。     

Synthesis, crystal structure and in vitro antitumor activity of di-n-butyltin 4′-(7-oxabicyclo [2,2,1]-5-heptane-2,3-dicarboximide) benzoates

Dibutyltin(IV) oxide reacts with the cantharidin analogue, 4′-(7-oxabicyclo [2,2,1]-5-heptane-2,3-dicarboximide) benzoic acid, A, to give the complexes [(p-C₈H₈NO₃-C₆H₄-COOBu₂Sn)₂O]₂ (1) and (p-C₈H₈NO₃-C₆H₄-COO)₂SnBu₂ (2) which had been characterized by IR and ¹H, ¹³C, ¹¹⁹Sn NMR. Single X-ray crystal structure analysis has been determined for compound (1), which was analogue to most other [(RCOOBu₂Sn)₂O]₂. The dimer features central of Bu₄Sn₂O₂ unit with the two Bu₂Sn groups being linked via bridging oxygen atom. Each tin atom adopts distorted trigonal bipyramidal structures via two carbons from a dibutyl moiety and three oxygen atoms from cantharidin derivative and bridging oxygen atom. In vitro tests show compounds 1 and 2 exhibit high cytotoxicity against P388 and HL-60.     

Calculations on the octupolar molecules with enhanced two-photon absorption cross sections based on the Zn (II) and Cu (I) as centers

The equilibrium geometries, electronic structures, as well as one- and two-photon absorption cross sections of a series of octupolar chromophores with Zn(2+) or Cu(+) as coordinate centers and 4,4'-bis(dibutylaminostyryl)-[2,2']-bis(bipyridyl) as ligands have been determined by using B3LYP/6-31G and ZINDO methods. These molecules are designed by controlled combination of two or three bipyridyl ligands with the metal centers. The results show that Zn(2+) is an effective template for the design of octupolar structures which enable it to form tetrahedral and octahedral coordinated complexes; while Cu(+) only exists in a tetrahedral coordinated complex, comparing the tetrahedral complex with Zn(2+) as the center with that of Cu(+) as the center, it is found that the complex with the Cu(+) center is a better two-photon absorption material than the former as far as the transparency/nonlinearity is concerned. Furthermore, for the same metal center of Zn(2+), both one- and two-photon absorptions of the tetrahedral complex are redshifted relative to those of the octahedral complex, is attributed to the spiroconjugation effect in the tetrahedral complex. Our theoretical findings are consistent with recent experimental observations and provide an important foundation for the design of improved transparency-nonlinearity two-photon absorption materials.     

OH自由基与CO反应的研究

用时间分辨-傅立叶变换红外发射光谱法研究了OH自由基与CO的反应.OH自由基由248 nm的激光光解硝酸得到.在实验中首次观测到了产物CO2的非对称伸缩振动(ν3)的激发态.对CO2发射光谱的拟合结果显示,其振动态的布居在量子数v=2时最大 ,而最高振动量子数达到v=6.由实验得到的CO2振动布居与Schatz等人用全量子化计算该反应的中间物HOCO解离动力学得到的CO2布居结果能很好地吻合.