Multifunctionalization of synthetic polymer systems through self-assembly

A straightforward methodology towards the replacement of covalent strategies for the synthesis of multifunctional synthetic materials with a self-assembling strategy that employs multiple noncovalent recognition units to attach multiple functional molecules to a polymeric scaffold is outlined. Design requirements, advantages, and potential applications, as well as the possibility of rapid optimization of materials during the manufacturing process as a result of the parallel character of self-assembly, are presented. While still in its infancy, this novel methodology may overcome several shortcomings of current covalent multifunctionalization strategies and may yield highly complex materials that are extremely difficult or impossible to fabricate with current methods.     

Calixarene-based multivalent ligands

Multivalency is a powerful concept which explains the strong binding observed in biological systems and guides the design and synthesis of ligands for self-assembly and molecular recognition in Chemistry. The phenol-formaldehyde cyclic oligomers, called calixarenes, have been used as scaffolds for the synthesis of multivalent ligands thanks to the fact that they have a variable number of reactive positions for attaching the ligating functions, well defined conformational properties and, in some cases, cavities of molecular dimensions eventually able to encapsulate guest species. This tutorial review illustrates the fundamental aspects of multivalency and the properties of calixarene-based multivalent ligands in lectin binding and inhibition, DNA condensation and cell transfection, protein surface recognition, self-assembly, crystal engineering, and nanofabrication.     

Design and Self-assembly of a Novel Tetranuclear Zinc（ Ⅱ ） Complex via Reaction of 1,3-Thiazolidine-2-thione（tzdtH） with Zn（ NO3）2

Introduction The self-assembly of clusters in inorganic systems is an interesting subject.The self-assembly of big mole-cules has been well established in biological sys-tems[1—5].In addition,the coordination chemistry of metal-sulfur-nitrogen cluster co…     

Ultrathin cross-linked nanoparticle membranes

The fabrication of functional nanostructured materials for sensing, encapsulation and delivery requires practical approaches to self-assembly on multiple length scales and the synthesis of tough yet permeable structures. Here, the self-assembly of functionalized, photoluminescent nanoparticles at liquid interfaces, followed by cross-linking of the associated ligands, affords robust membranes that maintain their integrity even when they are removed from the interface. These composite membranes, nanometers in thickness, are elastic yet permeable and have potential applications involving controlled permeability and diffusion. Cadmium selenide (CdSe) nanoparticles are used, since their inherent photoluminescence offers a direct way to probe the spatial organization of the particles. Functionalized ligands attached to the nanoparticles provide an effective means to stabilize the interfacial assembly by cross-linking. The concepts shown are adaptable to other type of nanoparticles, ligands, and solvent combinations.     

钼原子簇合成化学研究──（Ⅰ）一些单核钼化合物的自兜反应和成簇反应规律

本文是作者在钼原子簇合成化学研究的综合性报导，包括自兜合成和设计合成两个部分。这一部分概述了一些Ｍｏ（＋３）～Ｍｏ（＋６）单核化合物在Ｃｌ~－、Ｓ~（２－）、ＣＨ_３ＣＯ_２~－和（ＥｔＯ）ＰＳ_２~－等配基参与下的自兜反应及其产物，总结了成簇的某些规律。包括Ｍｏ原子的价态，μ－桥基的种类，介质的酸度对所形成的簇合物的影响。反应中卤原子的交换现象，以及和ＲＣＯ_２~－（ＥｔＯ）_２ＰＳ_２~－两种双齿配基的配位特点。讨论了自兜合成方法的局限性。     

Choline dendrimers as generic scaffolds for the non-covalent synthesis of multivalent protein assemblies

A modular self-assembly strategy is presented that allows the non-covalent synthesis of multivalent protein dendrimers using the strong interaction between choline-functionalized dendrimers and the choline binding protein C-LytA. Choline dendrimers displaying fusion proteins of C-LytA and the collagen binding protein CNA35 represent attractive multivalent targeting ligands for collagen imaging.     

超分子双膦配体的构筑及应用研究进展

超分子双膦配体是一类新兴起的基于非共价键作用构筑的双膦配体,近年来引起人们的重视.与传统的共价键连接的双膦配体相比,利用非共价相互作用的可逆性和选择性,超分子双膦配体具有合成简便,组合灵活,易于合成超分子配体库,并利用组合化学的方法对催化体系进行优化和筛选等优点.详细综述了近几年发展的基于氢键、配位键、主客体作用和静电作用等弱相互作用的超分子双膦配体,重点讨论了它们的构建方法以及在不对称催化反应中的应用,并对其发展前景进行了展望.     

Structure‐Based Design of Inhibitors of the Aspartic Protease Endothiapepsin by Exploiting Dynamic Combinatorial Chemistry

Structure‐based design (SBD) can be used for the design and/or optimization of new inhibitors for a biological target. Whereas de novo SBD is rarely used, most reports on SBD are dealing with the optimization of an initial hit. Dynamic combinatorial chemistry (DCC) has emerged as a powerful strategy to identify bioactive ligands given that it enables the target to direct the synthesis of its strongest binder. We have designed a library of potential inhibitors (acylhydrazones) generated from five aldehydes and five hydrazides and used DCC to identify the best binder(s). After addition of the aspartic protease endothiapepsin, we characterized the protein‐bound library member(s) by saturation‐transfer difference NMR spectroscopy. Cocrystallization experiments validated the predicted binding mode of the two most potent inhibitors, thus demonstrating that the combination of de novo SBD and DCC constitutes an efficient starting point for hit identification and optimization.     

Preparation of new heterotopic ligands

A six-step synthesis of two new heterotopic ligands, each possessing two unusual N,N,N,O tetradentate binding subunits, has been developed. This work presents a particularly facile and rapid synthetic protocol for the preparation of these ligands, which one expected to act as useful components in inorganic self-assembly for the preparation of various types of complexes.     

A facile approach toward multicolor polymers：Supramolecular self-assembly via host-guest interaction

A one-step and facile strategy toward the construction of multicolor polymers via supramolecular selfassembly was proposed.Multicolor polymers were simply prepared by the self-assembly of adamantane-labeled fluorescein,adamantane-labeled rhodamine B and β-cyclodextrin polymers via host-guest interaction between β-cyclodextrin and adamantane.Multicolor polymers showed several interesting properties：multiple emission signatures by a single wavelength excitation,easy tunability,intense fluorescence,high photostablility.In addition,the self-assembly approach implied a facile and flexible strategy for constructing functionalized materials,such as multicolor materials for biological labeling and imaging,and sensing materials for the detection of physiological parameters.     

A facile synthesis of aminomethylene bisphosphonates through rhodium carbenoid mediated N-H insertion reaction. Application to the preparation of powerful uranyl ligands

A straightforward procedure ensuring the anchoring of bisphosphonate moiety onto aromatic amines is described. The procedure yields aminoaryl 1,1-bisphosphonates known to display multiple biological activities. The described methodology has also been applied to the synthesis of ligands whose uranyl-binding properties have been studied.     

Coordination-Driven Selective Formation of D2 Symmetric Octanuclear Organometallic Cages

The coordination-driven self-assembly of organometallic half-sandwich iridium(III)- and rhodium(III)-based building blocks with asymmetric ambidentate pyridyl-carboxylate ligands is described. Despite the potential for obtaining a statistical mixture of multiple products, D₂ symmetric octanuclear cages were formed selectively by taking advantage of the electronic effects emanating from the two types of chelating sites – (O,O’) and (N,N’) – on the tetranuclear building blocks. The metal sources and the lengths of bridging ligands influence the selectivity of the self-assembly. Experimental observations, supported by computational studies, suggest that the D₂ symmetric cages are the thermodynamically favored products. Overall, the results underline the importance of electronic effects on the selectivity of coordination-driven self-assembly, and demonstrate that asymmetric ambidentate ligands can be used to control the design of discrete supramolecular coordination complexes.     

Solvent-Free Self-Assembly for Scalable Preparation of Highly Crystalline Mesoporous Metal Oxides

Mesoporous metal oxides (MMOs) have been demonstrated great potential in various applications. Up to now, the direct synthesis of MMOs is still limited to the solvent induced inorganic-organic self-assembly process. Here, we develop a facile, general, and high throughput solvent-free self-assembly strategy to synthesize a series of MMOs including single-component MMOs and multi-component MMOs (e.g., doped MMOs, composite MMOs, and polymetallic oxide) with high crystallinity and remarkable porous properties by grinding and heating raw materials. Compared with the traditional solution self-assembly process, the avoidance of solvents in this method not only greatly increases the yield of target products and synthesis efficiency, but also reduces the environmental pollution and the consumption of cost and energy. We believe the presented approach will pave a new avenue for scalable production of advanced mesoporous materials for various applications.     

金属有机框架与新型载药体系

金属-有机骨架材料(MOFs)是一类由金属离子与有机配体之间的配位自组装形成的新型多孔复合材料。因其具有高比表面积、可调的尺寸、拓扑结构多样性、合成简便、有机基团易于功能化等优点使其在生物分析、成像、传感、催化、气体存储与分离以及药物运载等领域具有广泛的应用前景。这里通过简要介绍MOFs的研究背景,基于MOFs孔径的药物装载策略以及MOFs药物释放的刺激响应方式,阐述MOFs作为药物递送载体的最新进展,为后期药物载体的设计提供参考。     

Functional supramolecular assemblies derived from dendritic building blocks

Control of the structure and function of self-assembled materials has been a significant issue in many areas of nanoscience. Among many different types of building blocks, dendritic ones have shown interesting self-assembly behaviour and functional performances due to their unique shape and multiple functionalities. Dendritic building blocks exhibit unique self-assembly behaviour in diverse environments such as aqueous and organic solutions, solid-liquid interfaces, and thermotropic solid conditions. Tuning the balance between hydrophilic and hydrophobic parts, as well as the external conditions for self-assembly, provides unique opportunities for control of supramolecular architectures. Furthermore, the introduction of suitable functional moieties into dendrons enables us to control self-assembly characteristics, allowing nanostructures to exhibit smart performances for electronic or biological applications. The self-assembly characteristics of amphiphilic dendrons under various conditions were investigated to elucidate how dendrons can assemble into nanoscopic structures and how these nanoassemblies exhibit unique properties. Well-defined nanostructures derived from self-assembly of dendrons provide an efficient approach for exhibition of unique functions at the nanoscale. This feature article describes the unique self-assembly characteristics of various types of dendritic building blocks and their potential applications as advanced materials.     

One-step facile surface engineering of hydrophobic nanocrystals with designer molecular recognition

High quality nanocrystals have demonstrated substantial potential for biomedical applications. However, being generally hydrophobic, their use has been greatly limited by complicated and inefficient surface engineering that often fails to yield biocompatible nanocrystals with minimal aggregation in biological fluids and active targeting toward specific biomolecules. Using chimeric DNA molecules, we developed a one-step facile surface engineering method for hydrophobic nanocrystals. The procedure is simple and versatile, generating individual nanocrystals with multiple ligands. In addition, the resulting nanocrystals can actively and specifically target various molecular addresses, varying from nucleic acids to cancer cells. Together, the strategy developed here holds great promise in generating critical technologies needed for biomedical applications of nanocrystals.     

Three-ligand Co-assembled 2D Au(I)-Thiolate Nanosheets

Two-dimensional (2D) Au(I)-thiolate assemblies are a special type of material that can balance high structural stability and rich surface functionality, which shows promising prospects in both fundamental research and applications. Co-assembly of multiple ligands is a facile way to further enrich the surface properties and functions, and expand their application potentials. In this work, taking 3-mercaptopropionic acid (MPA), cysteine (Cys) and 1-thioglycerol (TGO) as example ligands, we studied in detail the possibility to co-assemble them into one nanosheet. Although the three ligands have significantly different controllability and pathways when self-assembling individually with Au(I), they can still be effectively co-assembled by reacting with HAuCl₄ together to obtain three-ligand nanosheets with good colloidal stability. The key points for successful co-assembly are also revealed by comparing single- and three-ligand self-assembly processes, laying a solid foundation for co-assembly of even more ligands. The easy but powerful strategy for 2D materials with closely-packed and multiple tunable surface functional groups addresses the surface engineering problem for 2D materials and paves the way for their wider applications in sensing and biomaterials.     

One-dimensional optoelectronic nanostructures derived from the aqueous self-assembly of pi-conjugated oligopeptides

The aqueous self-assembly of oligopeptide-flanked pi-conjugated molecules into discrete one-dimensional nanostructures is described. Unique to these molecules is the fact that the pi-conjugated unit has been directly embedded within the peptide backbone by way of a synthetic amino acid with pi-functionality that is compatible with standard Fmoc-based peptide synthesis. The peptide-based molecular design enforces intimate pi-pi communication within the aggregate after charge-screening and self-assembly, making these nanostructures attractive for optical or electronic applications in biological environments. The synthesis and assembly are reported along with spectroscopic and morphological characterization of the new nanomaterials.     

Topological polymer chemistry by dynamic selection from electrostatic polymer self-assembly

A collection of recent developments in topological polymer chemistry is presented. First, topological isomerism occurring on randomly coiled, flexible polymer molecules having cyclic and linear structures is discussed. Second, an electrostatic self-assembly and covalent fixation strategy has been developed for the synthesis of polymeric topological isomers. These isomers have double cyclic, manacle-, and theta-shaped constructions, and are prepared by using either linear or star telechelic polymer precursors having moderately strained cyclic ammonium salt groups, which carry multifunctional carboxylate counteranions. A technique of reversed-phase chromatography (RPC) is demonstrated as an effective means to separate polymers with different topologies, especially polymeric topological isomers. A further extension of topological polymer chemistry has been observed by dynamic selection from electrostatic polymer self-assembly to enable the effective formation of tadpole-shaped, cyclic-linear hybrid topologies.     

New Approach to N‐substituted‐1,2,3,6‐tetrahydro‐pyridine‐4‐carbaldehyde,a Precursor for Synthesizing Aricept®, Isoguvacine,and Deethylibophyllidine

A new route towards the synthesis of N‐substituted‐4‐formylpiperidine using N‐benzyl or tryptaminyl‐sulfonylacetamide and α,β‐unsaturated ester as starting materials is described. Formal synthesis of Aricept^®, deethylibophyllidine, and isoguvacine, which have potential biological activities, were synthesized via this strategy.