Theoretical Modeling of the Surface-Guided Self-Assembly of Functional Molecules

Directing the self-assembly of organic building blocks with 2D templates has been a promising method to create molecular superstructures having unique physicochemical properties. In this work the on-surface self-assembly of simple ditopic functional molecules confined inside periodic nanotemplates was modeled by means of the lattice Monte Carlo simulation method. Two types of confinement, that is honeycomb porous networks and parallel grooves of controlled diameter and width were used in the calculations. Additionally, the effect of (pro)chirality of the adsorbing molecules on the outcome of the templated self-assembly was examined. To that end, enantiopure and racemic assemblies were studied and the resulting structures were identified and classified. The obtained findings demonstrated that suitable tuning of the structural parameters of the templates enables directing the self-assembly towards linear and cyclic aggregates with controlled size. Moreover, chiral resolution of the molecular conformers using honeycomb networks with adjusted pore size was found possible. Our theoretical predictions can be helpful in designing structured surfaces to direct self-assembly and polymerization of organic functional building blocks.     

Template-Free Self-Assembly of Molecular Trefoil Knots and Double Trefoil Knots Featuring Cp*Rh Building Blocks

Understanding and controlling the topology of self-assembled structures plays a fundamental role in supramolecular chemistry. Herein, the preparation of a series of tetranuclear metallarectangles and hexanuclear trefoil knots featuring Cp*Rh building blocks by template-free self-assembly with four different rigid and flexible ligands is described. Transformations between the trefoil knots and the corresponding macrocycles can be induced by using concentration effects. Remarkably, the hexanuclear trefoil knot 5 was shown to assemble further to provide rare examples of [12+1] heteronuclear double trefoil knots ( 5 a/5 b/5 c/5 d ) through coordination of the amide oxygen atoms to the secondary metal ions Na⁺/K⁺/Ca²⁺/Cd²⁺. The synthetic results are supported by single-crystal XRD.     

不对称两嵌段共聚物熔体在平板狭缝中微相分离的Monte Carlo模拟

采用改进的键长涨落空穴扩散算法对平板狭缝中不对称两嵌共聚高分子熔体的微相分离进行了Monte Carlo模拟。模拟结果表明：在吸引壁条件下，靠近壁面处将形成平等于壁面的层状相；在弱吸引壁条件下，靠近壁面处将形成垂直于壁面的层状相；不对称共聚物在远离壁面处有丰富的微区形态。从结构因子上分析可知，弱吸引壁条件下不对称共聚物的结构比强吸引壁条件下更接近对称共聚物。     

Polyoxometalate-Engineered Building Blocks with Gold Cores for the Self-Assembly of Responsive Water-Soluble Nanostructures

The controlled assembly of gold nanoparticles (AuNPs) with the size of quantum dots into predictable structures is extremely challenging as it requires the quantitatively and topologically precise placement of anisotropic domains on their small, approximately spherical surfaces. We herein address this problem by using polyoxometalate leaving groups to transform 2 nm diameter gold cores into reactive building blocks with hydrophilic and hydrophobic surface domains whose relative sizes can be precisely tuned to give dimers, clusters, and larger micelle-like organizations. Using cryo-TEM imaging and ¹H DOSY NMR spectroscopy, we then provide an unprecedented “solution-state” picture of how the micelle-like structures respond to hydrophobic guests by encapsulating them within 250 nm diameter vesicles whose walls are comprised of amphiphilic AuNP membranes. These findings provide a versatile new option for transforming very small AuNPs into precisely tailored building blocks for the rational design of functional water-soluble assemblies.     

Protection of nano-powders by adsorbed surfactants: A Monte Carlo study

The production of high-performance ceramics requires the protection of powder particles against chemical reactions. Hydrolysis and oxidation of nanoscaled non-oxidic powders can be impeded by a coating consisting of a dense adsorbed layer of amphiphilic molecules. Using Monte Carlo simulations for a coarse grained model the adsorption equilibrium of differently shaped amphiphiles in apolar and polar solvents is investigated. For estimating the protection capability of the adsorbed surfactant film in aqueous environment we study the diffusion of small hydrophilic particles through the adsorbed surfactant film. The surfactants considered as coating agents differ in the number of hydrocarbon tails. It is found that amphiphiles with a single hydrocarbon tail or at most two branches are more suitable to protect particle surfaces than amphiphiles with three or four branches, although the adsorption energy of amphiphiles with many branches is higher.     

有机共轭分子自组装方法

本文综述了有机共轭分子自组装方法的最新研究进展,从有机共轭分子的合成、自组装方法、光电性质及应用等方面进行了阐述,着重阐述了适用于有机共轭分子的各种自组装方法。认为它们的自组装在有机光电材料或器件方面具有广阔的应用前景及潜在的应用价值。     

Stereocomplex Crystallization in Asymmetric Diblock Copolymers Studied by Dynamic Monte Carlo Simulations

Stereocomplex crystallization in asymmetric diblock copolymers was studied using dynamic Monte Carlo simulations, and the key factor dominating the formation of stereocomplex crystallites(SCs) was uncovered. The asymmetric diblock copolymers with higher degree of asymmetry exhibit larger difference between volume fractions of beads of different blocks, and local miscibility between different kinds of beads is lower, leading to lower SC content. To minimize the interference from volume fraction of beads, the SC formation in blends of asymmetric diblock copolymers was also studied. For the cases where the volume fractions of beads of different blocks are the same, similar local miscibility between beads of different blocks and similar SC content was observed. These findings indicate that the volume fraction of beads of different blocks is a key factor controlling the SC formation in the asymmetric diblock copolymers. The SC content can be regulated by adjusting the difference between the contents of beads of different blocks in asymmetric diblock copolymers.     

多肽超分子手性自组装与应用

多肽分子作为一类重要的生物手性小分子,能够通过分子自组装形成包括纳米螺旋、纳米管、手性凝胶等在内的有着独特生物效应和光学活性的手性纳米材料。这类材料具有易于功能化修饰的优点,在化学、生物、医药、材料科学等领域有着广泛应用,成功对多肽手性自组装结构进行精准多级调控,是进一步实现其功能化应用的基础。本文重点介绍了多肽分子氨基酸序列组成与构型等内部因素,以及溶液pH、溶剂、添加剂等外界因素对多肽分子手性自组装行为的影响,并归纳得出其关键作用机制;同时,还介绍了多肽手性自组装材料在手性催化、手性检测、模板合成、手性光学等领域的应用。     

Predicting the Molecular Arrangements in Polymer‐Based Nanocomposites

Monte Carlo computer simulations have been performed for model polymers containing randomly distributed spherical filler particles (20% in volume) with diameter between 4 times and 28 times the transverse diameter of the chains. By analyzing the results in conjunction with those of previous simulations, a few simple rules are deduced allowing to predict approximately the molecular arrangements in these complex systems.

Schematic two‐dimensional picture of the mutual arrangements of filler particles and chains predicted for system M₁₂.     

Asymmetric Amplification in the Catalysis with Chiral Lanthanide Complexes

Remarkably high asymmetric amplifications (positive nonlinear effects) were realized in some chiral lanthanide complex-catalyzed organic reactions such as the asymmetric hetero-Diels–Alder reaction, Michael addition reaction, epoxidation, etc. These phenomena may be explained by the autogenetic formation of the enantiopure lanthanide complexes as the most active catalysts. The high coordination numbers of the lanthanides seem to play an important role through the formation of aggregates of the heterochiral complexes as less active catalysts.     

Substrate‐Induced Dimerization Assembly of Chiral Macrocycle Catalysts toward Cooperative Asymmetric Catalysis

An artificial system of substrate‐induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen‐bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich‐like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen‐bonding interaction sites. Inspired by the guest‐induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β‐ketoacid by a cooperative hydrogen‐bonding network enabled by sulfamate‐induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved.     

不对称催化反应在手性农药不对称合成中的一些应用

近十多年来，不对称催化反应在单一手性农药研发中的应用渐渐引起人们的关 注，结合自己的研究对这一领域的不对称催化反应及手性催化剂的发展进行了归纳 总结。     

Encoding Chiral Molecular Information in Metal Structures

The concept of encoding molecular information in bulk metals has been proposed over the past decade. The structure of various types of molecules, including enantiomers, can be imprinted in achiral substrates. Typically, to encode metals with chiral information, several approaches, based on chemical and electrochemical concepts, can be used. In this Minireview, recent achievements with respect to the development of such materials are discussed, including the entrapment of chiral biomolecules in metals, the chiral imprinting of metals, as well as the combination of imprinting with nanostructuring. The features and potential applications of these designer materials, such as chirooptical properties, enantioselective adsorption and separation, as well as their use for asymmetric synthesis will be presented. This will illustrate that the development of molecularly encoded metal structures opens up very interesting perspectives, especially in the frame of chiral technologies.     

Emergent Self-Assembly Pathways to Multidimensional Hierarchical Assemblies using a Hetero-Seeding Approach

The controlled formation of complex and functional 1-, 2-, and 3D hierarchical assemblies from molecular building blocks represents a key current challenge. Herein, we report the use of a seeded growth approach for a series of perylenediimide-based molecules (PDIs 1 – 4 ) to access otherwise inaccessible self-assembly pathways that yield complex hierarchical structures. The key to the new approach is to use hetero-seeds which possess a different composition and morphology from that of the molecular building block. For example, a nanotube seed (from PDI 3 ) and a microribbon seed (from PDI 4 ) were found to initiate different self-assembly pathways for PDI 1 , which normally assembles to yield nanocoils. This led to the formation of unprecedented 3D scroll-like and scarf-like hierarchical nanostructures, respectively. Also, the hetero-seeds from PDI 3 initiate hidden self-assembly pathways of PDI 2 to generate 1D tubular heterojunctions. Significantly, this new strategy offers new opportunities to create emergent and functional hierarchical and complex structures from small molecule precursors.     

Interfacial Tension and Width of an Asymmetric Polymer Mixture

We have used continuous space rod-bead model and an off-lattice Monte Carlo technique to investigate interfacial properties between two incompatible polymers of different stiffnesses. We have estimated the interfacial tension as well as interfacial width of all the systems studied. Further, by studying the interfacial tension and/or interfacial width in the weak segregation limit one can estimate the critical value of temperature at which two different kinds of polymers mix. In the present work, we have estimated the critical value of temperature at which the polymers mix by studying the interfacial width in the weak segregation limit for the different systems containing the flexible and semi-flexible polymers of different stiffnesses.     

CdSe纳米结构单元的制备与自组装

纳米CdSe作为一种重要的半导体纳米材料,在发光二极管、生物标记、太阳能电池等领域有着广泛的应用。本文综述了CdSe纳米结构单元制备与自组装的最新研究进展。归纳出了6种有代表性的制备与组装方法,详细介绍了这些方法的原理以及采用这些方法制备的CdSe纳米结构。最后,对这一领域的发展方向作了展望。     

Self-Association and Self-Assembly of Molecular Clips in Water

Molecular clips functionalized with two sodium or ammonium benzoate groups self-assemble in water by means of a hydrophobically driven dimerization reaction. Depending on the counter ions, this self-assembly stops at the stage of the dimer (sodium) or continues to generate largenanometer-sized aggregates (ammonium). The molecules in the latteraggregates are proposed to be `glued' together by multiplehydrogen bonds between the ammonium counter ions and the benzoategroups of the clips.     

基于聚环氧乙烷链和亚苯基的刚棒-线团分子自组装

含有亲水性聚环氧乙烷(PEO)链和多个亚苯基作为刚棒的刚棒-线团(rod-coil)分子,由于具有很强的π-π堆积作用和微相分离作用,可以在本体和溶液中产生有序排列形成各种组装体。材料的性能主要依靠分子聚集体来体现,因此研究分子聚集体的性质和用途成为当前超分子领域研究的重要内容。刚棒嵌段的形状影响着分子排列的方式、自组织性能和微结构,本文总结了Y型、T 型、O型、 K型、n型、螺旋桨型和哑铃型等不同形状分子的自组装行为,并展望了此类刚棒-线团分子未来研究的方向。