同系列电子给体与同系列电受体电荷转移络合作用的研究

用电子吸收光谱法, 研究了五个电子受体系列和三个电子给体系列以及非同系列的给、受体共48个化合物间的弱电荷转移络合作用。发现所研究的同系列给体与同一受体作用; 或同系列受体与同一给体作用; 或同系列给体与同系列受体作用, 一般存在着明显的CT络合与表观不络合的现象。通常情况下, 同系序数大的化合物呈现表观不络合;有时, 同系序数大和小的化合物, 即同系物的两头均呈现表观不络合现象, 对此种现象用给、受体间前线分子轨道能级关系进行了讨论。     

手性恶唑硼烷结构与还原苯基乙基甲酮的对映选择性研究

本文以苯基乙基甲酮为还原底物, 研究了原地(in situ)制备的在3、4、5位具有不同取代基的手性1,3,2-恶唑硼烷催化剂的结构与不对称催化效应关系。研究结果表明, 在不对称催化硼烷还原反应中(CBS方法)、产物的构型和对映选择性主要受手性恶唑硼烷的4位取代基控制。     

亲核试剂的亲卤反应2, 冠醚促进的二氟二溴甲烷与硫酚钠的反应

在苯、乙醚等溶剂中,CF_2Br_2与 PhSNa不反应或反应极慢.加入催化量的二苯并-18-冠-6,则反应在数分钟内完成,主产物 PhSCF_2Br 的产率提高至75～85%,副产物 PhSCF_2H 及 PhSSPh受到显著抑制.本体系明显优于最近文献报道的其他反应体系.讨论了反应机理,给出了表明反应主要是阴离子型链式机理的进一步证据:反应速度和产物分布对水、醇等给质子性杂质敏感,对氢原子供体型溶剂及光、氧、自由基捕获剂不敏感;在以 CCl_4为溶剂的反应中,得到 PhSCF_2Cl 和属于~-CCl_3的产物,而未检测到自由基型机理所预期的 CCl_3CCl_3.     

LaSr2-xCaxV3O9±y的制备、结构和价态影响

采用新的合成方法制备了一类新的化合物LaSr2-xCaxV3O9±y, X射线粉末衍射分析证实它们是单一化合物。利用计算机及自编软件对其进行了指标化并计算了它们的晶胞常数。结构数据表明, 随钙含量的增加, LaSr2-xCaxV3O9±y发生了从立方到正交到立方的相转变。热重和光电子能谱表明, 新化合物中的钒是以V^3^+和V^4^+的低价态形式存在, 它们具有较低的电阻率。     

Photoinduced electron transfer between adamantanamine-(OCH2CH2)n-phenothiazine and mono-6-p-nitrobenzoyl-β-cyclodextrin

A series of adamantanamine-(OCH₂CH₂)_n-phenothiazine (n = 0, 1, 2, 3) electron donors was synthesized. Photoinduced electron transfer was observed in the supramolecular complex of the phenothiazine derivatives with p-nitrobenzoyl-β-cyclodextrin (NBCD) through binding of the adamantyl group by the NBCD cavity, which is stabilized clearly via hydrophobic interactions in aqueous solution. Detailed Stern–Volmer constants were measured and they were partitioned into dynamic Stern–Volmer quenching constants and static binding constants. The results revealed an efficient electron transfer process inside the supramolecular systems compared to that controlled by diffusion. This observation also indicates that the chain length will influence the electron transfer efficiency of a supramolecular donor–acceptor system.     

[TPPFe(III)]~2O的合成及其对细胞色素P-450的模拟

TPPFe(III)Cl通过中性Al~2O~3色谱柱得到一个新化合物, 它在HPLC中的保留时间比TPPFe(III)Cl大得多, IR、UV-Vis和元素分析表明, 这个新化合物是[TPPFe(III)]~2O. 同TPPFe(III)Cl一样, 它具有在常温常压下催化碳氢化合物单充氧化的性质。[TPPFe(III)]~2O催化下PhIO氧化环己烷的反应, 在CH~2Cl~2和环己烷介质中, 氧化产率分别为14.97和62.6%, 高于TPPFe(III)Cl作催化剂时的产率。在环己烷溶剂中, 反应产率与反应时间呈线性关系, 且反应有大约3小时诱导期。但在CH~2Cl~2溶剂中不存在反应产物与时间的线性关系, 也不存在诱导期。与TPPFe(III)Cl比较,[TPPFe(III)]~2O对氧化剂更稳定。上述事实表明, [TPPFe(III)]~2O能够作为细胞色素P-450的模型化合物。     

用烯炔偶联环化合成具有生物活性内酯

最近, 我们发展了一个用两价钯催化开链烯丙基炔酸酯环化以立体选择性合成α-亚烷基-γ-丁内酯的方法[1]。在此法中, γ-丁内酯环是由原料酯中的烯炔环化发生碳-碳键偶联而生成的。值得注意的是: 反应产物中β, γ-位取代基的立体化学可以由叁键上的取代情况来控制, 即无取代的丙炔酸酯生成β,γ-反式二取代产物, 而取代的炔酸酯生成β, γ-顺式二取代产物。此方法特别意义在于可从易得的光学纯烯丙醇出发合成具有生物活性的光学纯内酯的任何一个对映体[2]。     

MgO·nB_2O_3-18%MgSO_4H_2O体系0℃时的热力学非平衡态液固相关系

在MgO·nB_2O_3-18%MgSO_4-H_2O体系0 ℃结晶过程的动力学研究、用物理方 法和化学分析确定析出固相的组成和测定固相共饱和点的基础上，给出了该体系0 ℃时的热力学非平衡态液固相关系图。该相图存在四个相区，分别与H_3BO_3， MgO·3B_2O_3·7.5H_2O，MgO·2B_2O_3·9H_2O和2MgO·3B_2O_3·15H_2O（多水 硼镁石）相对应。结果表明MgCl_2和MgSO_4介质对镁硼酸盐的析出有不同的影响。     

Changes in surface composition of Fe-Si-Cr-K oxide alkylation catalyst: the marked role of potassium ferrites

The influence of gas-phase methylation of phenol on the state of the Fe-Si-Cr-K oxide catalyst surface was investigated by thermodesorption of K atoms and ions. Changes in potassium desorption energies, as determined from Arrhenius-like plots, varied from 3.07 eV to 1.21 eV for the atoms and from 2.59 eV to 2.89 eV for ion desorption from the active and deactivated samples, respectively. The results were discussed in terms of transformation of the catalyst surface and formation of β-ferrite.     

Characteristics of excited-state intermediates of TiO2–Y-Zeolite and MCM41 encapsulating photosensitive molecules: design of new photocatalysts

Some photosensitive molecules, such as p-N,N′-dimethylaminobenzoic acid (DMABA), Nile Red, heteropolytungstic acid (H₃PW₁₂O₄₀, HPA) and metalloporphyrins, have been entrapped onto nano-scale pores or channels of TiO₂-modified Y-Zeolite (TiO₂-Y-Zeolite) and MCM41 (TiO₂-MCM41) and their excited-state intermediates have been characterized in terms of the excited-state dynamics by using laser spectroscopic techniques. Through these studies, it has been found that the photo-induced electrons are generated from the intramolecular charge transfer (ICT) state of DMABA, Nile Red or metalloporphyrin (MnTPP(Cl)), followed by transferring to the TiO₂-Y-Zeolite or TiO₂-MCM41 more efficiently as compared to the bulk TiO₂, NaY-Zeolite or MCM41. The efficient photoinduced interfacial electron transfer causes the rapid formation of radicals of those photosensitive molecules (a few tens ps). It has been also found that these photophysical properties can be applied to develop the new photocatalyst as observed by the efficient photocatalytic activities of the DMABA or Nile Red-entrapped TiO₂-Y-Zeolites for the photoreduction of an azo-dye such as Methyl Orange in water. On the other hand, in case of HPA-entrapped TiO₂-Y-zeolite, the electron generated from the excited-state TiO₂ is transferred to HPA, followed by formation of the reduction product, heteropoly blue (HPB) which is also generated by UV irradiation of HPA. This electron transfer is analogous to the Z-scheme mechanism of plant photosynthetic systems showing two photon reactions. Because of this photoelectron transfer mechanism, the HPA-entrapped TiO₂-Y-zeolite has demonstrated the synergistic enhancement of the photocatalytic decomposition of Methyl Orange and hydrogen generation from photolysis of water.