隐藏高分子界面及生物界面分子结构的和频振动光谱研究

界面的分子结构决定界面的性质.为了以优化界面的结构来改进材料的性质,原位实时地研究界面的分子结构是很重要的.近年来和频振动光谱已发展成为一个很有效及独特的手段来研究隐藏界面的分子结构,例如液/液界面、固/液界面及固/固界面等.这篇综述讨论了和频振动光谱在研究高分子界面及生物界面等复杂界面的分子结构上的应用.具体说来,本文论述了高分子表面在水里的分子结构变化,高分子及模型粘合促进剂硅烷在界面相互作用的分子机理和隐藏的高分子/高分子及高分子/金属界面的结构.另外,此文还将介绍不同二级结构的多肽及几个有代表性的蛋白分子在界面的结构.界面在诸如化学、生物、物理、材料科学及工程和纳米技术等许多领域都很重要.发展一个独特的能原位研究隐藏界面的分子结构的技术会有力地促进这些领域的研究及跨学科研究的发展.     

Competition between Bailar and Ray-Dutt paths in conformational interconversion of tris-chelated complexes: a DFT study

Tris-chelated complexes of aluminum with α-isopropenyltropolonate and α-isopropyltropolonate ligands can be considered prototypical complexes for the study of internal rearrangements through prismatic transient structures. Such isomerization paths, known as Bailar and Ray-Dutt twists, have been suggested for these compounds on the basis of dynamic NMR study, but modern computational methodologies have never been applied to corroborate this finding. In this paper, we report a computational investigation about the internal isomerization processes of the mentioned complexes. Both the Bailar and Ray-Dutt twists have been found as possible reaction paths. The prismatic structures along each reaction path have been described as transition structures rather than intermediate and have been computationally characterized. A comparison between experimental and computational kinetic data has been performed.     

Sizes and properties of clusters of magnetic ferrite structures

The structures of the coordination spheres or orbits of hexagonal and cubic crystals and their sizes, coordination numbers, and coordinates of atoms and cavities have been studied. The orbits of atoms of all sublattices of octahedral and tetrahedral cavities have been calculated. The close-packed structures (FCC and HCP) of oxygen ions have been considered as basic structures. In both structures, the metal cations are distributed over octahedral and tetrahedral cavities. The developed method is used for calculating the orbits of clusters with the hexagonal crystal structure of magnetoplumbite, ilmenite, and corundum, as well as with the cubic structure of spinel and perovskite.     

Total Syntheses of 11-Acetoxy-4-deoxyasbestinin D, 4-Deoxyasbestinin C,Asbestinin-10, -20, -21 and -23

Six members of the asbestinin family of marine diterpene natural products have been synthesized in an efficient and stereoselective manner from a single oxa-bridged intermediate. Five of these natural products have not been synthesized previously and the structures of four of them have been confirmed as those proposed originally or following revisions to the original structures. The fifth natural product—asbestinin-21—has been shown to be a diastereomer of the compound that had been proposed previously.     

When is an imine not an imine? Unusual reactivity of a series of Cu(II) imine-pyridine complexes and their exploitation for the Henry reaction

In this paper we report the synthesis and solid-state structures for a series of pyridine based Cu(II) complexes and preliminary data for the asymmetric Henry reaction. Interestingly, the solid-state structures indicate the incorporation of an alcohol into one of the imine groups of the ligand, forming a rare α-amino ether group. The complexes have been studied via single crystal X-ray diffraction, EPR spectroscopy and mass spectrometry. Intriguingly, it has been observed that the alcohol only adds to one of the imine moieties. Density functional theory (DFT) calculations have also been employed to rationalise the observed structures. The Cu(II) complexes have been tested in the asymmetric Henry reaction (benzaldehyde + nitromethane or nitroethane) with ee's up to 84% being achieved as well as high conversions and modest diastereoselectivities.     

Fullerene[51] with Quasi-planar Tetracoordinate Carbons and Its Derivatives

我们设计了包含准平面四配位碳原子的Fullerene[51]及其八个包含准平面四配位碳原子的衍生物，而且采用B3LYP方法研究了它们的结构、稳定性和成键性质。结果表明：这九种新型化合物是稳定的，它们的垂直电离能很大，而垂直电子亲和势相对较小。这些结构都包含五员环和六员环、以及更大的十员环。     

水热合成新型硼磷酸盐化合物的研究进展

作为潜在的新型功能材料，硼磷酸盐近几年得到了科学家的极大重视。本文从结构化学角度对水热合成硼磷酸盐化合物进行了总结，并着重对过渡金属、P区主族元素和含有机模板硼磷酸盐化合物所具有的典型结构进行了描述和归类，同时还讨论了硼磷酸盐的最新研究进展及其发展方向。     

General sacrificial template method for the synthesis of cadmium chalcogenide hollow structures

Semiconductor CdX (X=Te, Se, S) hollow structures have been successfully prepared by using Cd(OH)Cl precursors as a sacrificial template. The hollow structures can be hollow spheres or tubes by controlling the shape of the sacrificial template. The products were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectrometry. The obtained results showed that the hollow structures had complementary shapes and sizes of the original sacrificial templates. This is a general method for the synthesis of cadmium chalcogenide hollow structures, and the method is simpler and more practical than direct synthesis of certain hollow structures, which further widens the avenue to using those materials that have been synthesized with various shapes to fabricate specific hollow structures.     

Efficient and Eco‐friendly Syntheses of 1,5‐Benzothiazepines and 1,5‐Benzodiazepines Catalyzed by [Hmim][NO3] under Mild Conditions

This article presents a synthetic method and reaction mechanism of the 1,5‐benzothiazepines and 1,5‐benzodiazepines derivatives. In this research, 36 thiazepines and diazepines (mostly new) with a new method have been prepared and their structures have been characterized by spectroscopic methods. Crystal structures of a new thiazepine and diazepine (seven‐membered rings) have also been determined and compared with thiazine (six‐membered ring). In this method, N‐methylimidazolium nitrate [Hmim][NO₃] has been used as a catalyst that acts as an environmental friendly system.     

Layered self-organized structures on poly(3-octylthiophene) thin films studied by scanning probe microscopy

The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the preparation conditions, that is, spin-coating or drop-casting, of the solvent concentration or of the type of substrate. Using the drop-casting method for sample preparation these layered structures are hardly visible due to the high surface roughness, while using spin-coating these structures are the main topographic feature on the surface. These structures have typically one or two layers, even though occasionally up to four layers have been observed. Each layer has a height of 4-5 nm, which is associated to crystalline P3OT domains and lay on the polymer film. The size of these structures increases with increasing concentration of the P3OT in the solvent. We find well differentiated morphological, electrostatic as well as mechanical properties for the self-assembled structures as compared to the rest of the polymer film. Finally, the growth rate of these structures has been studied.     

液晶自组装多层级结构及其应用

液晶的分层组装与刺激响应特性使其在先进功能材料的开发与应用领域具有独特的优势.通过特定的技术手段诱导其自组装行为,可带来新奇的光学、机械、电磁等性能,进而实现一系列全新的技术应用.本文主要针对近晶相、胆甾相、蓝相这三种特殊的液晶相态,系统介绍了多形态焦锥畴结构,分层油纹,螺旋结构,双螺旋扭曲柱立方晶格等多层级结构,重点论述了材料组分优化,几何结构限制以及外场激励等条件下液晶多层级结构的大面积精细操控,回顾了其在粒子操控、表面改性、光子技术等领域的相关技术应用,并总结展望了液晶组装技术与应用的发展前景.     

The hierarchical structure of chemical engineering

Around the turn of the present century,scholars began to recognize chemical engineering as a com-plex system,and have been searching for a convenient point of entry for refreshing its knowledge base.From our study of the dynamic structures of dispersed particles in fluidization and the resultingmulti-scale method,we have been attempting to extend our findings to structures prevailing in othermultiphase systems as well as in the burgeoning industries producing functional materials.Chemicalengineering itself is hierarchically structured.Besides structures based on space and time,such hier-archy could be built from ChE history scaled according to science content,or from ChE operation ac-cording to the expenditure of manpower and capital investment.     

A green chemical approach to the synthesis of tellurium nanowires

Starch, an economical and safe carbohydrate, has been found to be not only an effective reducing agent but also a new morphology-directing agent for the synthesis of tellurium nanowires using commercial H2TeO4 precursor. The obtained tellurium nanowires are of single-crystal in nature, with an average diameter of approximately 25 nm and length up to 10 microm. A possible synthetic mechanism involves the chain-shaped bioorganic molecule acting as a template for the one-dimensional growth of inorganic tellurium. The effects of different chain-shaped structures and concentrations of biomolecules on the nanowire morphology have been investigated and different one-dimensional structures, including thick rods, short nanowires, bunched nanowires, and assembled spikelet structures, have been fabricated. These experimental results have been found to be useful in substantiating the proposed synthetic mechanism.     

Qualitatively graph-theoretical study on stability and formation of fullerenes and nanotubes

Kekule structures of different carbon species have been determined. On the basis of Kekule structure and C-C bond counts as well as the surface curvature, stability of diverse carbon species, driving force for curling of graphite fragments and formation of fullerenes and nanotubes, have been discussed. Curling of graphite flat fragments, end-capping of nanotubes, and closure of curved structures are driven by a tremendous increase in Kekule structures as terminal carbon atoms couple their dangling bonds into C-C o bonds. The increasing tendency becomes particularly striking for large cages and nanotubes. Resonance among numerous Kekule structures will stabilize the curved structure and dominate formation of closed carbon species. For similar carbon cages with comparable Kekule structure counts in magnitude, the surface curvature of carbon cages, as a measure for the strain energy, also plays an important role in determining their most stable forms.     

Accelerating the detection of unfeasible hypothetical zeolites via symmetric local interatomic distance criteria

In silico prediction of potential synthetic targets is the prerequisite for function-led discovery of new zeolites. Millions of hypothetical zeolitic structures have been predicted via various computational methods, but most of them are experimentally inaccessible under conventional synthetic conditions. Screening out unfeasible structures is crucial for the selection of synthetic targets with desired functions. The local interatomic distance (LID) criteria are a set of structure rules strictly obeyed by all existing zeolite framework types. Using these criteria, many unfeasible hypothetical structures have been detected. However, to calculate their LIDs, all hypothetical structures need to be fully optimized without symmetry constraints. When evaluating a large number of hypothetical structures, such calculations may become too computationally expensive due to the forbiddingly high degree of freedom. Here, we propose calculating LIDs among structures optimized with symmetry constraints and using them as new structure evaluation criteria, i.e., the LID_sym criteria, to screen out unfeasible hypothetical structures. We find that the LID_sym criteria can detect unfeasible structures as many as the original non-symmetric LID criteria do, yet require at least one order of magnitude less computation at the initial geometry optimization stage.     

Syntheses and Crystal Structures of Some Aryloxy and Alkoxy Substituted Phthalonitriles

Phthalonitriles substituted with aryloxy and alkoxy groups have been synthesized and characterized by elemental analyses, IR, mass spectra and 1H NMR spectroscopy. And four of such crystal structures have also been determined. In the crystal structures, the major inter- molecular interactions between the neighboring molecules are the hydrogen bonds as C≡N···H and C-O···H that lead to similar networks in the crystal structures.     

Ordered networks of ZnO-nanowire hierarchical urchin-like structures for improved dye-sensitized solar cells

Quasi-1D ZnO nanowires (NWs) ordered as patterned 3D hollow hierarchical urchin-like structures have been prepared on transparent conducting substrates by electrodeposition. The ZnO NWs have been grown on self-assembled ordered polystyrene microspheres with electrical charge densities ranging from 5 to 30 C cm(-2) and organized arrays of mono and multi-urchin layers have been built. These layers have been sensitized by the highly absorbing D149 indoline organic dye. The optical characterizations and dye titrations have shown a significant increase in the light scattering and absorption as well as dye loading for the organized structures compared to randomly vertically aligned ZnO NWs grown under the same conditions. The dye-sensitized solar cells (DSSC) prepared using the sensitized layers have been characterized by current-voltage (J-V) measurements, IPCE and by electrochemical impedance spectroscopy. We show that the best performances are obtained for the 3D urchin monolayer structures. The conversion efficiency is increased by up to 4 times compared to their counterparts made of randomly dispersed vertical ZnO NWs. Impedance spectroscopy results show a very fast charge transfer in the ZnO NWs and urchin monolayers and that the electron lifetime is in the 4-14 ms range.     

On the chemical synthesis of new topological structures

The construction of chemical species with topological properties is an area of increasing interest. Numerous such structures have been synthesized in recent years, particularly from DNA, which is a natural synthon for these molecules. Recently, higher-order topological structures have been introduced. These hyper-structures consist of combinations of simple structures, such as a Brunnian Link of Brunnian Links or a Hopf Ring of Hopf Rings, or combinations thereof. In this article, we discuss the possibilities of constructing these hyper-structures with real molecules, particularly emphasizing the tools that result from the double helical structure of DNA.     

分子动力学模拟研究熔盐中的局部结构

我们用分子动力学(MD)方法通过计算机模拟研究了熔盐中的键取向序和局部结构。描述局部结构的简单方法是计算键角分布几率,但它不能给出键取向序的三维空间描述。有的文献采用Direchlet-Voroitol(DV)多面体处理MD模拟产生的瞬态构型,但DV