含吸电子基团配体的α-二亚胺-Ni(Ⅱ)上乙烯聚合反应性能

合成了一种新型的含溴α-二亚胺配体及其Ni配合物,并采用核磁共振氢谱、核磁共振碳谱、元素分析、傅里叶变换红外光谱和X射线光电子能谱进行了表征.同时以二乙基氯化铝为助催化剂用于乙烯聚合反应,考察了温度、Al/Ni摩尔比和配体结构对聚合反应性能的影响.结果表明,在25℃,Al/Ni摩尔比为600时,该催化剂活性最高,可达3...     

2-氨基(芳氧基)-3-对甲基苯基噻吩并[3',2':5,6]吡啶并[4,3-d]嘧啶-4(3H)-酮的合成和生物活性

用邻氨基噻吩腈与乙酰乙酸甲酯为原料,利用串联Aza-Wittig法合成了9个未见文献报道的噻吩并吡啶并嘧啶类化合物,通过IR,1H NMR,EI-MS,元素分析等方法对所合成的化合物进行了结构表征,并初步测定了所合成化合物的杀菌活性.生测结果表明:此类化合物对棉花枯萎(Fusarium oxysporium)、水稻纹枯(Rhizoctonia solani)、小麦赤霉(Gibberella zeae)、苹果轮纹菌(Dothiorella gregaria)、棉花炭疽菌(Colletotrichum gossypii)等5种菌均有一定的抑制活性.其中对苹果轮纹菌抑制活性最好,在浓度为5.0×10-5g/mL时抑制率为31.80%～82.84%.     

New octahedral bis-α-diimine nickel(II) complexes containing chloro-substituted aryl groups: Synthesis, characterization and testing as ethylene polymerisation catalysts

Three new 20-electron bis-α-diimine nickel (II) complexes containing chloro-substituted ligands, bis{bis[N,N′-(3-chloro-2-methylphenyl)imino]-1,2-dimethylethane}dibromonickel 2a, bis{bis[N,N′-(3-chloro-2,6-dimethylphenyl)imino]-1,2-dimethylethane}dibromonickel 2b and bis{bis[N,N′-(4-chloro-2,6-dimethyl-phenyl)imino]-1,2-dimethylethane}dibromonickel 2c, were synthesized and characterized. The molecular structure of complex 2a was determined by X-ray crystallography. In the solid state, complex 2a has a pseudo-octahedral geometry about the nickel center, containing two α-diimine ligands in the pseudo-equatorial plane and two trans bromide ligands occupying the axial positions. These complexes, activated by diethylaluminum chloride (DEAC) were tested in the polymerization of ethylene under mild conditions. NMR analysis shows that highly branched polyethylenes are obtained using these bis-α-diimine nickel(II) complexes containing electron-withdrawing Cl groups in the aryl groups (e.g. 84 branches/1000 C, at 20 °C). The catalytic activity, polymer molecular weight and polymer degree of branching were significantly affected by the number of methyl substituents in the ortho-aryl position and the chlorine substituent position in the aryl rings of the coordinated α-diimine ligands.     

Synthesis and Spectroscopy of Novel Branched Fluorescent Dyes Containing Benzophenone Parts and the Possibility as Fluorescence Probes

This paper describes a new fluorescent family of branched dyes containing benzophenone unit including 4-N, N-diphenylamino-4??-phenacyl-stilbene (C1), 4,4??-di(4-benzoylphenylethylene)yl-triphenylamine (C2) and 4,4??,4??-tri(4-benzoylphenylethylene)yl-triphenylamine (C3). Benzophenone part is coupled with core through C?CC double bond. The chemical structures of the derivatives are characterized with ¹H and ¹³C nuclear magnetic resonance and elemental analysis. Strong ?ШC?? stacking interactions are discovered with the analysis of the X-ray crystallographic data of C1. The absorption maxima and emission maxima of the derivatives exhibit gradual bathochromic shift from C1 to C3. The optical density of C1, C2 and C3 are shown to be related to the number of branches. The changes of dipole moments between the excited and ground states for C1, C2 and C3 were estimated to be 4.356, 8.091 and 8.479 Derby, respectively by Lippert equation, confirming that the internal charge transfer (ICT) dominates the process of excited singlet state. The possibility as fluorescence probes of the derivatives on the estimation of what region of micelles interacting with samples was evaluated.     

2,5-取代-1,3,4-噁二唑衍生物的合成与杀菌活性

利用生物活性亚结构拼接原理,将吡啶环、噻唑环引入到1,3,4-噁二唑母体结构中,设计并合成了一系列新型含吡啶(噻唑)的1,3,4-噁二唑衍生物.通过IR,1H NMR,EI-MS及元素分析等方法对所合成的化合物进行了结构表征.代表化合物2-(6-氯吡啶-3-甲硫基)-5-(吡啶-4-基)-1,3,4-噁二唑(I)经单晶X衍射证实了结构.初步测定了所合成化合物的杀菌活性,并比较了在1,3,4-噁二唑母体结构中引入噻唑杂环和引入吡啶杂环后其杀菌活性的差异.结果表明:目标化合物对测试的5种菌均具有一定的杀菌活性,对水稻纹枯病的抑制效果普遍优于对其它菌种的抑制效果;在1,3,4-噁二唑母体结构中引入噻唑杂环比引入吡啶杂环对其杀菌活性更有利.     

Chiral nickel(II) and palladium(II) catalysts bearing strong electron‐withdrawing fluorine groups: synthesis,characterization and their application in catalytic polymerization for ethylene and styrene

A series of new chiral and achiral nickel(II) and palladium(II) complexes, {bis[N,N′‐(2,6‐diethyl‐4‐naphthylphenyl)imino]‐1,2‐dimethylethane}dibromonickel 3a , {bis[N,N′‐(4‐fluoro‐2‐methyl‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel rac‐(RS)‐ 3b , {bis[N,N′‐(4‐fluoro‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel rac‐(RR/SS)‐ 3c and {bis[N,N′‐(4‐fluoro‐6‐sec‐phenethylphenyl)imino]‐1,2‐dimethylethane}dichloropalladium rac‐(RR/SS)‐ 3d were successfully synthesized and characterized. The molecular structures of representative ligand rac‐(RS)‐ 2b , nickel complex 3a , rac‐(RR/SS)‐ 3c and palladium complex rac‐(RR/SS)‐ 3d were determined by X‐ray crystallography. The structures of complexes 3a and rac‐(RR/SS)‐ 3c have pseudo‐tetrahedral geometry about the nickel center, showing C₂ molecular symmetry. However, the structure of palladium complex rac‐(RR/SS)‐ 3d has pseudo‐square planar geometry about the palladium center, showing C₂ molecular symmetry. Complex 3e {bis[N,N′‐(2,6‐dimethylphenyl)imino]‐1,2‐dimethylethane}dibromonickel was also synthesized for comparison. Nickel complex rac‐(RS)‐ 3b bearing strong electron‐withdrawing fluorine group in the para‐aryl position and a chiral sec‐phenethyl group in the ortho‐aryl position of the ligand (one methyl group in the ortho‐aryl position) displays the highest catalytic activity for ethylene and styrene polymerization, and produced highly branched polyethylene and syndiotactic‐rich polystyrene. However, palladium complex rac‐(RR/SS)‐ 3d shows low catalytic activity for ethylene and styrene polymerization due to the poor leaving group, Cl, attached to palladium and the unfavorable molecular structure. Copyright © 2014 John Wiley & Sons, Ltd.     

长沙经济发展的动态分析

本文根据1997~2004年的长沙经济主要指标的时序立体数据表,进行时序全局主成分分析,得到一条动态轨迹并表明和客观实际能较好的吻合,为促进经济的快速发展提供一定的参考依据.     

高中学生解决实际问题的困难分析及教学对策

从现在高考的趋势看，高考综合科目中的实际问题越来越简单，但实际上对学生却存在着新的困难。问题在于学生们能适应传统的物理教学，习惯于抽象的逻辑推理及数学运算，而遇到实际问题就束手无策．针对这种现象，就需要在教学方法和指导学生学习方法上加强物理图像情境的教学，提高学生解决实际问题的能力．     

Several Variants of the Primal-Dual Hybrid Gradient Algorithm with Applications

By reviewing the primal-dual hybrid gradient algorithm (PDHG) proposed by He, You and Yuan (SIAM J. Image Sci., 7(4) (2014), pp. 2526-2537), in this paper we introduce four improved schemes for solving a class of saddle-point problems. Convergence properties of the proposed algorithms are ensured based on weak assumptions, where none of the objective functions are assumed to be strongly convex but the step-sizes in the primal-dual updates are more flexible than the previous. By making use of variational analysis, the global convergence and sublinear convergence rate in the ergodic/nonergodic sense are established, and the numerical efficiency of our algorithms is verified by testing an image deblurring problem compared with several existing algorithms.     

湍流热对流DNS多分辨率并行直接求解方法

依据温度标量场与动量计算的空间和时间计算分辨率不同的特点,采用两套网格,建立多分辨率双网格并行直接求解方法,用以解决极高Ra数湍流热对流DNS模拟巨大计算工作量的难题.在两套网格的数据交换上,根据每个细网格都满足连续方程,设计了速度的守恒平移插值方法.二维极高Ra数湍流热对流的计算结果表明,采用多分辨率双网格并行直接求解方法的DNS计算,可以使计算工作量降低近一个量级.瞬时温度场显示,双网格方法的计算结果可以很好地描述极高Ra数下快速运动的小尺寸漩涡团状羽流,得到的结果与原网格一致,不同方法计算得到的传热Nu数误差不超过1%.