Synthesis of polysubstituted benzothiophenes and sulfur-containing polycyclic aromatic compounds via samarium diiodide promoted three-component coupling reactions of thiophene-2-carboxylate

By the promotion of samarium diiodide, thiophene-2-carboxylate reacted with 2 equiv of ketones at the C-4 and C-5 positions to give diols such as 2 and 9. Because the intermediary organosamarium species were oxophilic but not too basic, the double hydroxyalkylations with various ketone substrates, including alkyl aryl ketones, acetylthiophenes, cyclohexanone, alpha-tetralone, and alpha-phenylacetophenones, were realized without complication of side reactions. The diol products underwent an acid-catalyzed dehydration to give dienes such as 3 and 10, which were treated with DDQ to give either polysubstituted thiophenes (e.g., 4 and 11) or benzothiophenes (e.g., 5, 13, and 14) depending on the reaction conditions. Oxidative annulations of 4,5-diarylthiophenes 11 and 4,5,6,7-tetraphenylbenzothiophenes 14 were carried out by photochemical or chemical methods to give the sulfur-containing polycyclic aromatic compounds, such as phenanthro[9,10-b]thiophene-2-carboxylate, piceno[13,14-b]thiophene-2-carboxylate, and tribenzo[fg,ij,rst]pentapheno[15,16-b]thiophene-2-carboxylates. This method is applicable to the preparation of polysubstituted thiophenes, benzothiophenes, and the related compounds possessing liquid crystalline, photochromic, and other functional properties.     

Sequential electrochemical oxidation of alternating benzene-furan oligomers

Electrochemical oxidation of pentaaryl 2 containing two furan moieties occurs sequentially to give diketone 8 after two-electron transfer. Further oxidation with another two-electron transfer gives the corresponding tetraketone 9. Radical cation intermediate is detected by absorption spectroscopy. The radical intermediates of different regiochemistry have been shown to exhibit different oxidation potentials as revealed by the differential pulse voltammetry.     

可见光激发下PtⅣClx /TiO2的光诱导电子转移研究

1998年, Kisch等[1]发现PtⅣ卤化物修饰的TiO2催化剂(PtⅣClx/TiO2)具有可见光活性, 他们认为PtⅣ卤化物作为光敏化物种, 能够将电子转移到TiO2导带, 催化剂的表面吸附氧捕获电子后生成氧自由基, 继而氧化降解成对氯苯酚. 但是, 由于PtⅣ卤化物及其激发态能级的不确定, 对其反应机理研究尚未见报道.     

Flow cytometric characterization of interactions between U-937 human macrophages and positively charged catanionic vesicles

Catanionic vesicles are considered a potential alternative to liposomes for drug delivery systems because of their greater stability and lower cost. Before using catanionic vesicles in vivo, their interactions with macrophages must be fully understood because they are primarily removed from circulation by the macrophages of the mononuclear phagocyte system. Using flow cytometry, we examined the intracellular responses-reactive oxygen species (ROS) content, mitochondrial membrane potential, cell size and complexity, and cell cycle profiles-in U-937 human macrophages treated with positively charged catanionic vesicles. Kinetic hydrogen peroxide production initially increased at lower concentrations (4-10nM) but declined at higher concentrations (40 nM and 80 nM) over the entire incubation period. Superoxide content generation, however, increased over the entire concentration range and incubation period. Catanionic vesicles decreased mitochondrial membrane potential for every concentration after 4h of incubation but caused a significant fluctuation in mitochondrial membrane potential at 6h. After 6h of incubation, catanionic vesicles produced more changes in cell size and complexity than after 4h. The increase in the subG1 population of cells treated with catanionic vesicles at higher doses indicated that apoptosis progressed. Positively charged catanionic vesicles induced different activated patterns of ROS generation and changes in mitochondrial membrane potential than did cationic liposomes. The nature of the interactions between macrophages and catanionic vesicles is of great importance for the design of safer and more effective delivery systems for macrophages. Our findings contribute to a better understanding of the molecular action of catanionic vesicles in the cellular system.     

Sorption of cesium on rocks using heterogeneity-based isotherm models

Summary Sorption of radionuclides onto surrounding rocks play an important role in retarding the migration of radionuclides from a radioactive waste repository. The sorption isotherm model is usually used to describe the sorption behaviors and assess the sorption potential of radionuclides on rock. However, most of the studies to investigate the feasibility of isotherm models for the sorption of radionuclides are based on the assumption that the sorption energy is uniform and homogeneously distributed on the sorbent surfaces. In this study, two heterogeneity-based isotherms, Langmuir-Freundlich isotherm model (LF) and generalized-Freundlich isotherm model (GF), were used for the evaluation of the sorption characteristics of cesium on the selected Taiwan tuff and basalt. The sorption experiments in this study were carried out by batch method, and the experimental data were modeled by LF and GF heterogeneity-based isotherm models. The results showed that both of the LF and GF models could fit the data more perfectly than the Langmuir model. The heterogeneity of sorption onto tuff and basalt could be well characterized by the LF and GF models by means of the calculation and plotting of the affinity spectrum. The results showed that the sorption surface of tuff is more heterogeneous and complex than that of basalts.     

Stereoselectivity, periselectivity, and regioselectivity in the cycloadditions of 8-(p-chlorophenyl)-8-azaheptafulvene with cyclopentadiene and fulvenes

The stereoselectivity, periselectivity, and regioselectivity in the cycloaddition reactions of 8-(p-chlorophenyl)-8-azaheptafulvene with cyclopentadiene and symmetrical/unsymmetrical fulvenes is described.     

Charge-transfer-induced cesium superlattices on graphene

We investigate cesium (Cs) adsorption on graphene formed on a 6H-SiC(0001) substrate by a combined scanning tunneling microscopy and density functional theory study. Individual Cs atoms adsorb preferentially at the rim region of the well-defined 6×6 substrate superstructure and on multilayer graphene. By finely controlling the graphene thickness and Cs coverages (1/3 ML and 1?ML), we here demonstrate two intriguing and well-ordered Cs superlattices on bilayer and multilayer graphene (<6 layers). Statistical analysis of the Cs-Cs interatomic distance reveals a hitherto unobserved Cs-Cs long-range electrostatic potential caused by charge transfer from Cs to graphene, which couples with the inhomogeneous substrate potential to stabilize the observed Cs superlattices. The present study provides a new avenue to fabricate atomic and molecular superlattices for applications in high-density recording and data storage.     

小型矢量阵深海被动定位方法

文中提出一种适用于深海条件下并已知各项有关环境参数时,利用七元小型矢量立体阵,借助测定目标辐射噪声由不同途径自声源到达接收点的天顶角及方位角的结果,依据射线声学方法求得目标方位、距离和所在深度的被动定位方法。给出了矢量阵依多极子原理进行波束形成的计算公式,并就一种简单水文模型,给出解析计算公式。     

高质量CdSe量子点的水相制备与表征

以巯基丁二酸为稳定剂, 亚硒酸钠为硒源, 制备了高质量水溶性CdSe量子点. 研究了反应时间、 镉与硒的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdSe量子点光谱性能的影响. 分别用紫外-可见光谱、 荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点进行表征. 结果表明, 采用这种方法制得的CdSe量子点为立方晶型, 量子点的荧光发射峰在518～562 nm范围内连续可调, 并且发射峰的半峰宽始终保持在35 nm左右, 荧光量子产率可达21%.