Temperature-Driven Planar Chirality Switching of a Pillar[5]arene-Based Molecular Universal Joint

The study of an enantiopure bicyclic pillar[5]arene-based molecular universal joint (MUJ) by single-crystal X-ray diffraction allowed for the first time the unequivocal assignment of the absolute configuration of a planar chiral pillar[5]arene by circular dichroism spectroscopy. Crucially, the absolute configuration of the MUJ was switched reversibly by temperature, with an accompanying sign inversion of the anisotropy factor that varied by as much as 0.03, which is the largest value ever reported. Mechanistically, the reversible chirality switching of the MUJ is driven by the threading/dethreading motion of the fused ring and hence is dependent on both the size and nature of the ring and the solvent employed, reflecting the critical balance between the self-complexation of the ring by pillar[5]arene, the solvation to the excluded ring, and the inclusion of solvent molecules in the cavity.     

Redox‐Triggered Chirality Switching and Guest‐Capture/Release with a Pillar[6]arene‐Based Molecular Universal Joint

A chiral electrochemically responsive molecular universal joint (EMUJ) was synthesized by fusing a macrocyclic pillar[6]arene (P[6]) to a ferrocene‐based side ring. A single crystal of an enantiopure EMUJ was successfully obtained, which allowed, for the first time, the definitive correlation between the absolute configuration and the circular dichroism spectrum of a P[6] derivative to be determined. The self‐inclusion and self‐exclusion conformational change of the EMUJ led to a chiroptical inversion of the P[6] moiety, which could be manipulated by both solvents and changes in temperature. The EMUJ also displayed a unique redox‐triggered reversible in/out conformational switching, corresponding to an occupation/voidance switching of the P[6] cavity, respectively. This phenomenon is an unprecedented electrochemical manipulation of the capture and release of guest molecules by supramolecular hosts.     

Autoamplification of Molecular Chirality through the Induction of Supramolecular Chirality

The novel concept for the autoamplification of molecular chirality, wherein the amplification proceeds through the induction of supramolecular chirality, is presented. A solution of prochiral, ring‐open diarylethenes is doped with a small amount of their chiral, ring‐closed counterpart. The molecules co‐assemble into helical fibers through hydrogen bonding and the handedness of the fibers is biased by the chiral, ring‐closed diarylethene. Photochemical ring closure of the open diarylethene yields the ring‐closed product, which is enriched in the template enantiomer.     

手性溶剂诱导非手性物质手性的研究进展

手性溶剂诱导非手性物质产生手性是目前合成手性物质的主流方法之一。与传统的手性物质合成方法相比,手性溶剂诱导法不仅避免了使用昂贵的手性试剂,还能扩大合成手性物质的结构范围,具有潜在的应用前景。目前,手性溶剂诱导方法适用范围已经涵盖了有机小分子、低聚物和聚合物体系。本文主要对手性溶剂诱导方法发展的历史背景,手性溶剂诱导小分子及低聚物的手性,手性溶剂诱导非手性聚合物产生超分子手性,主要包括π-共轭聚合物和σ-共轭聚合物这几个方面展开了综述。     

Molecular Recognition Properties of Biphen[4]arene

Biphen[n]arenes (n=3, 4) are a new family of macrocyclic hosts. Here, we describe the molecular recognition behavior of hydroxylated biphen[4]arene (OHBP4) for the first time. A series of cationic guests with different sizes and shapes, including quaternary ammonium salts ( 1? PF₆ and 2? PF₆), pyridinium‐based guests ( 3? 2 PF₆– 6? 2 PF₆), and cobaltocenium hexafluorophosphate ( 7? PF₆), were chosen as model guest molecules. OHBP4 exhibits good selectivity towards the 2,7‐dibutyldiazapyrenium bis(hexafluorophosphate) ( 4? 2 PF₆) axle to form a [2]pseudorotaxane‐type complex. In contrast, hydroxylated biphen[3]arene (OHBP3) cannot bind with this big guest. In addition, OHBP4 strongly interacts with adamantane derivative 2? PF₆ and cobaltocenium 7? PF₆, which have tridimensional shape and relatively large size. The association constant of the 7 ⁺?OHBP4 complex in 1:1 (v/v) [D₆]acetone/CD₂Cl₂ solution is up to 3100±300 m ^?1.     

Langmuir and Langmuir–Blodgett Films from Amphiphilic Pillar[5]arene‐Containing [2]Rotaxanes

Amphiphilic pillar[5]arene‐containing [2]rotaxanes have been prepared and fully characterized. In the particular case of the [2]rotaxane incorporating a 1,4‐diethoxypillar[5]arene subunit, the structure of the compound was confirmed by X‐ray crystal structure analysis. Owing to a good hydrophilic/hydrophobic balance, stable Langmuir films have been obtained for these rotaxanes and the size of the peripheral alkyl chains on the pillar[5]arene subunit has a dramatic influence on the reversibility during compression–decompression cycles. Indeed, when these are small enough, molecular reorganization of the rotaxane by gliding motions are capable of preventing strong π–π interactions between neighboring macrocycles in the thin film.     

Recent progress in the research on the host-guest chemistry of pillar[n]arenes

Pillar[n]arene, as a new kind of macrocyclic host molecule, is a cyclic oligomer, which has a unique rigid structure with a hydrophobic cavity and can interact with many size-matched guest molecules. In this review, the molecular recognition, self-assembly and applications of the pillar[n]arenes in the past two years were described. On the basis of previous scientific research, a variety of pillar[n]arene-based supramolecular systems responsive to specific external stimuli such as pH, redox, gas, light, etc. has been constructed. Pillar[n]arenes have exhibited great potential in constructing these fantastic supramolecular systems based on host-guest recognition, including nanomaterials, controllable drug delivery, transmembrane channels, chemosensors and catalytic entities. These supramolecular systems have a wide range of applications in the material, biology, detection and catalysis field, but their applications are not limited to these fields.     

Sequential Chiral Induction and Regulator-Assisted Chiral Memory of Pillar[5]arenes

Chirality transfer is widely observed in life processes, and many artificial chiral transfer systems have been developed. In these systems, chiral information is transferred from chiral inducers to chiral acceptors by a direct chiral induction process and a direct chiral memorization process. We have developed ternary nondirect chiral transfer systems based on pillar[5]arenes, in which a third factor was introduced as a regulator. The planar chirality of an acceptor was induced and memorized by a chiral inducer with precise control by a regulator. In the chiral induction period, the feed sequence of the chiral inducer and regulator affected the chiral induction behavior of the chiral acceptor. The chiral memory ability of the acceptor was substantially improved by the combined action of the chiral inducer and regulator.     

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., “0” and “1”) in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 10³), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DP_TPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.     

Thermally Responsive Poly(ethylene oxide)-Based Polyrotaxanes Bearing Hydrogen-Bonding Pillar[5]arene Rings**

Poly(ethylene oxide)s (PEOs) are useful polymers with good water solubility, biological compatibility, and commercial availability. PEOs with various end groups were threaded into pillar[5]arene rings in a mixture of water and methanol to afford pseudopolyrotaxanes. Corresponding polyrotaxanes were also constructed by capping COOH-terminated pseudopolyrotaxanes with bulky amines, in which multiple hydrogen bonds involving the pillar[5]arene OH groups were critically important to prevent dethreading. The number of threaded ring components could be rationally controlled in these materials, providing a simple and versatile method to tune the mechanical and thermal properties. Specifically, a polyrotaxane with a high-molecular-weight axle became elastic upon heating above the melting point of PEOs and exhibited temperature-dependent shape memory property because of the topological confinement and crosslinked hydrogen bonds.     

Diversity Oriented Preparation of Pillar[5]arene-Containing [2]Rotaxanes by a Stopper Exchange Strategy

Rotaxane building blocks bearing 3,5-bis(trifluoromethyl) benzenesulfonate (BTBS) stoppers have been efficiently prepared from a pillar[5]arene derivative, 3,5-bis(trifluoromethyl) benzenesulfonyl chloride (BTBSCl) and different diols, namely 1,10-decanediol and 1,12-dodecanediol. The BTBS moieties of these compounds are good leaving groups and stopper exchange reactions could be achieved by treatment with different nucleophiles thus affording rotaxanes with ester, thioether or ether stoppers.     

Applications of Pillar[n]arene‐Based Supramolecular Assemblies

Macrocycles are an important player in supramolecular chemistry. In 2008, a new class of macrocycles, “pillar[n]arenes”, were first discovered. Research efforts in the area of pillar[n]arenes have elucidated key properties, such as their shape, reaction mechanism, host–guest properties, and their versatile functionality, which has contributed to the development of pillar[n]arene chemistry and their applications to various fields. This Minireview describes how pillar[n]arene‐based supramolecular assemblies can be applied to supramolecular gel formation, reactions, light‐harvesting systems, drug‐delivery systems, biochemical applications, separation and storage materials, and surface chemistry.     

柱[6]芳烃的合成及在分子识别中的应用研究进展

柱芳烃是近年来超分子研究领域中备受关注的一类新型大环主体化合物。与柱[5]芳烃相比,柱[6]芳烃因具有更大的管状空腔结构而表现出了独特的主客体性能。介绍了柱[6]芳烃的结构与构象,并重点阐述了柱[6]芳烃的合成方法以及在分子识别中的应用研究进展。     

Non-Covalent Interactions Enable the Length-Controlled Generation of Discrete Tubes Capable of Guest Exchange

Supramolecular chemistry in confined spaces constructed from macrocyclic molecules has attracted much attention because it can utilize the specific binding properties of macrocyclic cavities. Herein we report the preparation of length-controlled discrete tubular structures by homo-/co-assembly of rim-differentiated and peralkylamino-substituted pillar[5]arenes via hydrogen bonds and salt bridges. By dimerization and trimerization, the expanded tubes show a fivefold helical structure and stepwise binding, respectively. We found that the exchange speed of guest molecules in the tubes could be controlled by varying the tube length.     

Diverse Role of Solvents in Controlling Supramolecular Chirality

Supramolecular self-assembly stands for the spontaneous aggregation of small organic compounds or polymers into ordered structures at any scale. When being induced by inherent molecular chiral centers or ambient asymmetric factors, asymmetric spatial arrangement between building units shall occur, which is defined as supramolecular chirality. Except for molecular design, utilizing external stimulus factors to tune supramolecular chirality is a promising approach. In this Concept article, we particularly discuss the important role of solvents in manipulating the chirality of self-assembled systems. The impact of solvents on the chirality is generally based on three properties of solvents, i.e., chirality, polarity, and active coassembly with building blocks. Molecular self-assembly in chiral solvents could undergo the chirality transfer, exhibiting a chiral induction effect. Solvent polarity often determines intermolecular orientation. As a consequence, those building blocks with both polar and apolar segments might change their chirality depending on the solvent polarity. We elaborate the active participation of solvent molecules into ordered structures together with building blocks, where solvents and building blocks exhibit a coassembly manner. By specific treatments such as heating and cooling, solvents could be released or re-entrapped, allowing a smart control over supramolecular chirality. The solvent effect in manipulating two-dimensional chiral self-assemblies is then discussed. The perspective and future development in this research field are presented at last.     

Piling Up Pillar[5]arenes To Self‐Assemble Nanotubes

New liquid‐crystalline pillar[5]arene derivatives have been prepared by grafting first‐generation Percec‐type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc‐shaped structure perfectly suited for self‐organization into a columnar liquid‐crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6‐dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Col_h mesophase has been deduced from X‐ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4‐dimethoxypillar[5]arene and 1,6‐dicyanohexane.     

柱芳烃的合成与应用

综述了近四年来新型超分子主体化合物柱芳烃的合成、发展和应用.其中,柱芳烃及其衍生物的合成主要有两种有机化学合成策略,即"先成环后修饰"和"先修饰后成环".由于这类新型主体化合物具有非常特殊的空间结构和理化性质,目前,它主要应用在主客体包合与分子识别、自组装体系的构筑和智能材料等领域.     

杯芳烃和柱芳烃桥梁部位的衍生及其功能化

随着大环化学的快速发展,对杯芳烃、柱芳烃及其他类似化合物的桥梁亚甲基部位进行高效修饰的方法日益引起人们的关注.桥梁部位修饰后的大环衍生物,在不改变其原有属性的基础上增加了新的功能,不仅可以引入更多的功能基团,而且可以通过主客体的自组装行为,进一步拓展杯芳烃和柱芳烃等超分子大环在药物递送、化学传感、荧光体系构建等诸多领域...     

Enhanced Solution and Solid-State Emission and Tunable White-Light Emission Harvested by Supramolecular Approaches

Organic luminescent materials with high quantum yields and/or white-light-emitting properties in particular play a crucial role in labeling and optoelectronic devices. In this work we have synthesized a new 2,3,6,7-tetramethoxy-9,10-di-p-tolylanthracene-bridged pillar[5]arene dimer with persistent mazarine blue fluorescent emission and much higher quantum yields in both solution and the solid state in comparison with its corresponding emissive linker without pillarene units, which exhibits typical aggregation-caused quenching. According to the fluorescence data and single-crystal analyses, their contrasting fluorescent performances can be rationally ascribed to their different stacking structures and intermolecular interactions. Three fluorescent guests containing different chromophores and/or terminal binding sites have also been synthesized to interact with the pillar[5]arene dimer to construct supramolecular ensembles with highly controllable luminescence, taking advantage of the stimuli-responsive properties of the supramolecular host–guest interactions. Intriguingly, multicolor fluorescence, including white-light emission (0.31, 0.35), which is in high demand, has been achieved by tuning the molar ratio of the host and guest and/or by changing the solvent system. This strategy holds great potential for the design and development of fluorescent materials with high quantum yields, controllable emission wavelength, and good stimuli-responsiveness.