Theoretical studies on the intra- and intermolecular C-H activation by T-shaped pincer complexes

Three coordinated, T-shaped (PNP)M^I (M = Co, Ru, Rh, Os and Ir) and [(PCP)Pt⁰]⁻, as well as their reactivities for intra- and intermolecular C-H activation have been studied by DFT methods. The experimental observed reactivities were well reproduced. The calculation also generated structural and energetic information which the experimental values were not yet available. We found that the intramolecular C-H activation is in general possible for the low spin (PNP)M^I. Intermolecular C-H activation is not preferred either thermodynamically or kinetically, but could be in competition if the intramolecular activation is reversible. Using model compounds, we found that the intramolecular C-H activation reactivity is not sensitive to steric effects of the bulky ligands. However, the strain of the four-membered ring in the product significantly reduces the reactivity, and the driving force increases by 4.51-12.95 kcal/mol if the strain was largely removed by changing from a four-membered ring to a five-membered ring. The C-H activation step is quite difficult for metals with a d¹⁰ configuration. Part of the reason is that one phosphine ligand dissociates during the reaction because the product has a d⁸ configuration and prefers a square planar structure.     

Multifunctional polythreading coordination polymers: spontaneous resolution, nonlinear-optic, and ferroelectric properties

The reactions of methylenediisophthalic acid (H₄L) and N‐auxiliary ligands (1,2‐bis(4‐pyridyl)ethylene, 1,2‐bis(4‐pyridyl)ethane) with transition‐metal centers (Co²⁺/Mn²⁺) have given rise to four unprecedented polythreading coordination polymers. Single‐crystal X‐ray diffraction analyses revealed that the compounds can be described as 3D^2??2[1D²⁺]+2D^6? for 1 , 3D^4??1D²⁺+1D^6? for 2 , and 2D^4??0D²⁺+2[1D^3?] for 3 and 4 . All the polymers are formed through the assembly of two kinds of motifs with opposite charges. Noncentrosymmetric structures and multifunctionality in 2 – 4 are established by varying ligands and metal centers. Spontaneous resolution upon crystallization occurred in compounds 3 and 4 in the absence of any chiral source. The enantiomers of 3 and 4 consist of three chiral building blocks of L^4?/HL^3? and Mn²⁺ centers. In the solid state, polar compounds 2 – 4 exhibit nonlinear‐optic (NLO) and ferroelectric properties at room temperature. The assembly of two kinds of motifs with opposite charges provides a useful method for the preparation of multifunctional compounds.     

非线性左右手媒质界面的Goos-Hänchen位移

 由均匀平面电磁波在左右手媒质界面满足的切向边界条件出发,推导了电磁波由线性传统媒质入射到非线性左手媒质时波的传播特性。利用时间延迟的方法,给出全反射情况下媒质界面非线性Goos-Hänchen位移表达式。分析了非线性左手媒质界面的侧向位移随入射角及入射波电场强度的变化关系,发现入射波场强对传输特性起决定作用:当入射波电场小于临界场强时,调节入射场强可以控制相应的侧向位移;当入射波电场大于临界场强时,不再满足全反射条件,部分入射波透射到非线性介质中。波导中加入非线性介质不仅可以调节侧向位移的大小,且可以实现对入射波场强的控制。     

A Mechanistic Understanding of the Distinct Regio- and Chemoselectivity of Multifunctional P450s by Structural Comparison of IkaD and CftA Complexed with Common Substrates

Regio- and chemoselective C−H activation at multi-positions of a single molecule is fascinating but chemically challenging. The homologous cytochrome P450 enzymes IkaD and CftA catalyze multiple C−H oxidations on the same polycyclic tetramate macrolactam (PoTeM) ikarugamycin, with distinct regio- and chemoselectivity. Herein we provide mechanistic understanding of their functional differences by solving crystal structures of IkaD and CftA in complex with ikarugamycin and unnatural substrates. Distinct conformations of the F/G region in IkaD and CftA are found to differentiate the orientation of PoTeM substrates, by causing different binding patterns with polar moieties to determine site selection, oxidation order, and chemoselectivity. Fine-tuning the polar subpocket altered the regioselectivity of IkaD, indicating that substrate re-orientation by mutating residues distal to the oxidation site could serve as an important method in future engineering of P450 enzymes.     

金属有机骨架HKUST-1及其衍生材料在催化中的应用进展

金属有机骨架材料(MOFs)作为异相催化剂受到了日益广泛的关注。在众多经典MOFs结构中，HKUST-1及其衍生材料是研究最多的类型之一。HKUST-1具有原料简单、易于合成、结构稳定、孔隙率高等多种优点，在异相催化领域中具有广阔的应用前景。已有多种HKUST-1相关材料被用作催化剂，包括HKUST-1本身、缺陷型结构、负载活性客体分子的复合型材料以及HKUST-1衍生的多孔碳纳米材料等。本文围绕HKUST-1作为催化剂的结构设计以及在不同催化反应中的应用展开总结与介绍，以期为相关MOFs材料的设计和催化研究提供一定参考。     

Validation of Material Models in Grain Scale Simulation based on EBSD Experimental Data

A crystal plasticity model and a homogenization method are used to analyze the local and global mechanical behavior of a ferritic stainless steel. In the first step the material constants are determined based on tensile tests and used to simulate the local deformation behavior on the grain scale in the second step. For that 2D EBSD data are discretized by finite elements. The computed local grain reorientations of three different BCC slip systems are compared to experimental data at the state of 20% elongation. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Implementation of Multi-GPU Based Lattice Boltzmann Method for Flow Through Porous Media

The lattice Boltzmann method (LBM) can gain a great amount of performance benefit by taking advantage of graphics processing unit (GPU) computing, and thus, the GPU, or multi-GPU based LBM can be considered as a promising and competent candidate in the study of large-scale fluid flows. However, the multi-GPU based lattice Boltzmann algorithm has not been studied extensively, especially for simulations of flow in complex geometries. In this paper, through coupling with the message passing interface (MPI) technique, we present an implementation of multi-GPU based LBM for fluid flow through porous media as well as some optimization strategies based on the data structure and layout, which can apparently reduce memory access and completely hide the communication time consumption. Then the performance of the algorithm is tested on a one-node cluster equipped with four Tesla C1060 GPU cards where up to 1732 MFLUPS is achieved for the Poiseuille flow and a nearly linear speedup with the number of GPUs is also observed.     

一种含马来酰亚胺环氧树脂固化剂的合成与结构、光谱和热力学性质研究

以马来酸酐、对硝基苯胺、环氧氯丙烷为原料，首先合成出N-(4-硝基苯基)马来酰亚胺（NPMI）、再将其催化还原成N-(4-氨基苯基)马来酰亚胺（APMI），最后以APMI与环氧氯丙烷反应合成出一种新型的含马来酰亚胺环氧树脂固化剂 N-(4-氨基苯基马来酰亚胺)二缩水甘油胺（MPDGA）。采用密度泛函理论B3LYP/6-311++G(d , p)方法，研究了所合成的MPDGA分子的几何结构、电子结构及热力学性质。获得了它们的红外光谱、电子光谱和分子轨道图，以及标准摩尔热容Cθpm、标准摩尔熵Sθm、标准摩尔焓Hθm等气态热力学性质与温度的变化关系，同时获得了MPDGA分子的标准摩尔生成焓 和标准摩尔生成自由能 数据。