Controlled/“Living “Radical Polymerization of(-)-Menthyl Methacrylate

The atom transfer radical polymerization(ARP)of (-)-menthyl methacrylatc((-)-MnMA) mediated by CuCl/bipyridine and ethy1 2-bromopropionate or 1-phenylethyl bromide in THF system has been studied.The dependence of the specific rotation on molecular weight and the CD of Poly((-)-MnMA) thus obatined was investigated.     

氟阴离子在有机合成中的应用：Ⅱ.无水氟化钾催化乙酐与苯甲醛的Perkin反应

用无水醋酸盐催化苯甲醛与乙酐的Perkin反应,一般反应时间较长,产率最高为55—60％.用三乙胺、吡啶和无水碳酸钾等作催化剂,产率也无明显提高.近年来氟阴离子在有机合成中的应用迅速发展,我们曾用无水氟化钾催化成功地实施了丙二酸二乙酯与苯甲醛的Knoevenagel缩合,并研讨了该反应的微环境效应.本工作首次用无水氟     

Synthesis,crystal structure and magnetic properties of [RBzPy] [Fe(mnt)2] complexes ([RBzPy]+ = 1-(4′-R-benzyl)pyridinium,R = NO2 and CL; mnt2− = maleonitriledithiolate)

Ion-pair complexes consisting of the [Fe(mnt)₂]^– anion and [RBzPy]⁺ cations [R = NO₂ (1) or Cl (2)] have been prepared and characterized by elemental analysis and i.r. spectroscopy. The single crystal structure of (1) shows that the [Fe(mnt)₂]^– anions are dimeric, and that the coordination geometry of each Fe atom is square pyramidal. The most significant structural feature of (1) is that anions and cations form completely separate columns and – interactions occur within the cation columns. Thermal variations of _m T for the complexes indicated antiferromagnetic coupling within the dimer.     

Charge-transfer hybrids containing covalently bonded polyoxometalates and ferrocenyl units

Two new charge-transfer hybrids with one or two ferrocenyl units covalently attached to a hexamolybdate cluster through an extended pi-conjugated bridge have been prepared using Pd-catalyzed coupling reactions on monoiodo- or diiodo-functionalized cluster substrates in over 60% yields. These hybrids have been characterized by (1)H NMR, FTIR, electrospray ionization mass spectrometry, and X-ray diffraction. The electronic spectra of these hybrids show a broad absorption tail extending beyond 550 nm, indicating the existence of charge-transfer transition from the ferrocenyl donor to the cluster acceptor. The observation of the clear charge-transfer transition indicates the contribution of charge-transfer resonance to the ground state in both 2a and 2b even though the donor-acceptor separation distance of 11.29 A is rather long, signaling a through-bond charge-transfer nature made possible by the organic pi-conjugated bridge. Cyclic voltammetry studies reveal a one-electron oxidation wave and a one-electron reduction wave for the hybrid with one ferrocenyl unit. For the one with two ferrocenyl units, a lower reduction potential and a two-electron oxidation wave are observed, indicating negligible electronic interactions between the two ferrocenyl units.     

载镍沸石上NH3-TPD脱附峰的非酸性探讨

NH_3-TPD技术表征固体催化剂的酸性似乎已很成熟,其实不然。如该技术表征HZSM-5沸石时,有作者观察到773K左右的高温脱氨峰,而有些作者则检测不到。诚然,各作者间所用试样及预处理条件等存在差异,但实验装置和实验操作条件不同带来的影响也不可忽视。此外,该技术在用于表征一些新的较复杂的催化剂时,其程脱谱也会呈现出新现象,这些现象有时是不能通过酸性来解释的,这是因为NH_3作为探针分子不仅具有碱性,同时还有还原性和配位性。本文对载镍沸石上NH_3-TPD谱图中出现的某些新峰进行了剖析和归属。     

巯基葡聚糖凝胶分离富集光度法测定镉的研究

研究了在ＴｒｉｔｏｎＸ－１００存在下，新显色剂邻羧基苯基重氮氨基偶氮苯（ＣＤＡＡ）与镉的显色体系，在ｐＨ１０．６的Ｎａ２Ｂ４Ｏ７－ＮａＯＨ体系中，显色反应灵敏度很高。络合物的最大吸收位于５４５ｎｍ处，其摩尔吸光系数为２．２２×１０＾５Ｌ·ｍｏｌ＾－１·ｃｍ＾－１。镉含量在０￣１２μｇ／２５ｍＬ符合比耳定律。将该体系用于巯基葡聚糖凝胶分离富集－光度法测水样中微量镉，结果令人满意。     

Sonochemical synthesis of mass single-crystal PbS nanobelts

Based on sonochemical technique, large-scale PbS nanobelts are successfully synthesized in the mixed solution of PbCl₂ and Na₂S₂O₃. These nanobelts are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), selected area electronic diffraction, energy dispersive X-ray spectroscopy, and high-resolution TEM. The as-synthesized PbS nanobelts have width of about 80 nm, length up to several millimeters, and width-to-thickness ratio of about 5. In addition, the growth mechanism of PbS nanobelts is suggested.     

Solid-state synthesis of a conducting polythiophene via an unprecedented heterocyclic coupling reaction

Prolonged storage ( approximately 2 years) or gentle heating (50-80 degrees C) of crystalline 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) affords a highly conducting, bromine-doped poly(3,4-ethylenedioxythiophene) (PEDOT), as confirmed by solid-state NMR, FTIR, CV, and vis-NIR spectroscopies. The novel solid-state polymerization (SSP) does not occur for 2,5-dichloro-3,4-ethylenedioxythiophene (DCEDOT), and requires a much higher temperature (>130 degrees C) for 2,5-diiodo-3,4-ethylenedioxythiophene (DIEDOT). X-ray structural analysis of the above dihalothiophenes reveals short Hal.Hal distances between adjacent molecules in DBEDOT and DIEDOT, but not in DCEDOT. The polymerization may also occur in the melt but is significantly slower and leads to poorly conductive material. Detailed studies of the reaction were performed using ESR, DSC, microscopy, and gravimetric analyses. SSP starts on crystal defect sites; it is exothermic by 14 kcal/mol and requires activation energy of approximately 26 kcal/mol (for DBEDOT). The temperature dependence of the conductivity of SSP-PEDOT (sigma(rt) = 20-80 S/cm) reveals a slight thermal activation. It can be further increased by a factor of 2 by doping with iodine. Using this approach, thin films of PEDOT with conductivity as high as 20 S/cm were fabricated on insulating flexible plastic surfaces.     

The Purification of Glucose Type Glycosyl Nitrate and the Synthesis of Spacer—armed N—Acetyllactosamines and Their Dimers

Our previous paper1,2reported the results of selective synthesis of mannose type glycosides and their dimers in our attempt to synthesize derivatives of N-acetyllacto- samine, which could have potential activity of anti-metastasis3. Further studies on the glycosylation of the accepters exploiting glycosyl nitrate instead of the acetate as donor showed interesting chemoselectivity between the two kinds of donor, namely, the glucose type and the mannose type. The reactivity difference of the t…     

低压催化氚化亮石松碱的定位效应的研究

近年来,中草药有效成分的研究引起国内外有关学者普遍关注。氚标记中草药有效成分是研究其相应的药代动力学和代谢产物的主要手段,它具有操作简便,条件温和等优点,但是一般氚化方法均不能明确给出氚化位置。而研究氚化定位效应又是药理工作者急待解决的重要课题,所以在很大程度上限制了该项技术的使用范围。最近,郑冬珠等人用FX—100型核磁共振谱仪给出了在PdO催化剂存在条件下,低压氚化亮石松碱的氚化位置及其相对含量。本文在前文基础上,以亮石松碱为底物,根据Fraser和Garnett等人提出的氢—氚同位素交换反应动力学理论,采用CNDO/2法,对PdO催化亮石松碱的立体构型讲行了计算,得出一些有意义的结果。