Crystal structure and supra-molecular features of a bis-urea-functionalized pillar[5]arene

The crystal structure of a bis-urea derivative based on A1/A2-functionalized pillar[5]arene (DUP) that encapsulates dimethyl formamide (DMF) inside the macrocyclic cavity is reported. The crystal structure of DUP·DMF, C63H70N4O12·C3H7NO, reveals that out of two urea functionalized spacers, one arm is oriented above the macrocyclic cavity with strong hydrogen-bonding inter-actions between the urea H atoms and DMF guest, whereas, the other arm is positioned away from the macrocycle, leading to inter-molecular hydrogen-bonding inter-actions between the urea H atoms of two adjacent pillar[5]arene macrocycles, resulting in the formation of a supra-molecular dimer.

Noncovalently bound and mechanically interlocked systems using pillar[n]arenes

Pillar[n]arenes are pillar-shaped macrocyclic compounds owing to the methylene bridges linking the para-positions of the units. Owing to their unique pillar-shaped structures, these compounds exhibit various excellent properties compared with other cyclic host molecules, such as versatile functionality using various organic synthesis techniques, substituent-dependent solubility, cavity-size-dependent host-guest properties in organic media, and unit rotation along with planar chiral inversion. These advantages have enabled the high-yield synthesis and rational design of pillar[n]arene-based mechanically interlocked molecules (MIMs). In particular, new types of pillar[n]arene-based MIMs that can dynamically convert between interlocked and unlocked states through unit rotation have been produced. The highly symmetrical pillar-shaped structures of pillar[n]arenes result in simple NMR spectra, which are useful for studying the motion of pillar[n]arene wheels in MIMs and creating sophisticated MIMs with higher-order structures. The creation and application of polymeric MIMs based on pillar[n]arenes is also discussed.

Crown Ether-Based Supramolecular Polymers: From Synthesis to Self-Assembly

Supramolecular polymers not only possess many advantages of traditional polymers, but also have many unique characteristics. Supramolecular polymers can be constructed by self-assembly of various noncovalent interactions. Host-guest interaction, as one important type of noncovalent interactions, has been widely applied to construct supramolecular polymers. From the perspective of classification of the recognition system motifs, host-guest recognition motifs mainly include crown ether, cyclodextrin, calixarene, cucurbituril, and pillararene-based host-guest recognition pairs. Crown ethers, as the first-generation macrocyclic hosts, have played a very important part in the development of supramolecular chemistry. Due to the easy modification of crown ethers, various crown ether derivatives have been prepared by attaching some functional groups to the edges of crown ethers, which endowed them with some interesting properties and made them ideal candidates for the fabrication of supramolecular polymers. This review gives a review of the preparation of crown ether-based supramolecular polymers (CSPs) and summarizes crown ether-based recognition pairs, organization methods, topological structures, stimuli-responsiveness, and functional characteristics.

Crown ether-pillararene hybrid macrocyclic systems

A combination of Nobel macrocycle-crown ether and star macrocycle-pillararenes together in organic synthesis and material science is significant in obtaining hybrid systems, with rigid/flexible structural architecture, induced planar chirality, a negative cooperative effect and multiple fused cyclic hosts. In this review, we will discuss the synthesis/preparation of crown ether-pillararene hybrid macrocyclic systems by covalent bonds, supramolecular interactions and mechanical bonds, leading to hybrid compounds, supramolecular assemblies and mechanically interlocked molecules. The practical applications of crown ether-containing pillararenes will also be discussed in diverse areas, such as molecular recognition via fused multiple macrocycles and ion channels as well as external stimuli-responsive smart materials. We also call the attention of related researchers towards academic and technical issues about topological structures and applied functions in this fresh new fused macrocyclic field.

Pillararene-based supramolecular polymers

Pillararenes, as a new type of macrocyclic hosts, possess columnar structures and electron-rich cavities. Pillararenes not only recognize suitable cations, but also bind many neutral molecules. Due to the easy modification of pillararenes, various functional groups can be conveniently attached to the rim of pillararenes to provide suitable interaction sites, and the modified pillararenes even bind anionic guests. Thus, pillararenes and their derivatives have presented intriguing and unique host-guest recognition nature in the past few years, which make them ideal building blocks for the preparation of supramolecular polymers. Pillararene-based supramolecular polymers (PSPs) not only possess many merits of traditional covalent polymers but also have many specific properties, such as self-reparability, degradability, and self-adaptation. This feature paper gives an overview of the preparation of PSPs and covers recent research advance and future trends of pillararene-based host-guest pairs, assembly methods, topological architectures, stimuli-responsiveness, and functional features. We expect that the review will be helpful to researchers working in the fields of supramolecular chemistry and polymer science.

Systematic rim cyano-functionalization of pillar[5]arene and corresponding host–guest property varieties

Synthetic investigation of the systematic replacement of alkoxy groups in pillar[5]arene by cyano ones was carried out. Host–guest property studies of nCN-pillar[5]arenes and 1,4-dicyanobutane showed the functionization number related host–guest interaction varieties.

Adjustable chiral self-sorting and self-discriminating behaviour between diamond-like Tröger's base-linked cryptands

Adjustable chiral self-sorting and self-discriminating behaviour between diamond-like Tröger's base-linked cryptands was reported, which could be regulated by external stimuli easily.

Multi-mode supermolecular polymerization driven by host-guest interactions

A novel supermolecular self-assembly based on ternary host-guest interaction between cucurbit[8]uril (CB[8]), 1,1'-dimethyl-4,4'-bipyridinium dication (MV) and coumarin derivative was applied for the construction of linear supramolecular polymer with high degree of polymerization in aqueous solution. Accompanied by the introduction of azobenzene on linear ABBA type monomer the supermolecular polymerization is different and the morphology changes from linear to dendritic polymer. The successful supramolecular polymerization of linear and dendritic supramolecular polymers by non-covalent host-guest molecular recognition was confirmed by various characterization methods, such as 1H NMR spectroscopy, ROESY, transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. Meanwhile, the supramolecular polymerization could promote the conversion of the azobenzene from cis to trans, which ultimately results in no isomerism upon UV irradiation.

Supramolecular chemistry of pillar[n]arenes functionalised by a copper(i)-catalysed alkyne-azide cycloaddition "click" reaction

Since we discovered pillar[n]arenes in 2008, many chemists have developed a strong interest in pillar[n]arene chemistry because of the many advantages associated with these materials, including their facile and high yielding synthesis, versatile functionality, planar chirality and unique host-guest properties. In this feature article, we discuss recent advances in the field of supramolecular chemistry based on the use of pillar[n]arenes as substrates for copper(i)-catalysed alkyne-azide cycloaddition (CuAAC) "click" chemistry. The CuAAC reaction provides facile access to 1,4-disubstituted triazoles by a reaction between alkyne and azido substrates in the presence of a Cu(i) catalyst. Pillar[n]arenes bearing alkyne or azido groups can therefore be used as substrates for this reaction. Herein, we discuss not only the synthesis of pillar[n]arenes bearing alkyne or azido groups but also the application of these functionalised systems to the CuAAC reaction to construct supramolecular assemblies. We also discuss the rational molecular design and synthesis of guest compounds using the CuAAC reaction because linear alkanes sandwiched between 1,2,3-triazole moieties are good guests for cyclic pentamer pillar[5]arenes.

Acid/base-controllable fluorescent molecular switches based on cryptands and basic N-heteroaromatics

Two kinds of fluorescent BMP32C10-based cryptands 1 and 2 have been developed. Cryptand 1 contains a binaphthol group, while cryptand 2 bears a coumarin group in their third arms. Based on this design, novel self-assemblies constructed from cryptand 1 or 2 and basic N-heteroaromatic guests 3-6 were successfully obtained. Moreover, the threading/dethreading processes of the host-guest complexes could be well switched by the alternate addition of acid/base, and accompanied by concurrent changes in fluorescence.

4-Methylcoumarin-bridged fluorescent responsive cryptand: from [2+2] photodimerization to supramolecular polymer

A fluorescent responsive BMP32C10-based cryptand host was successfully synthesized by introducing a 4-methylcoumarin group to the third arm of the cryptand. The cryptand was able to undergo [2+2] photodimerization on UV irradiation (λ = 365 nm) and, based on the photodimerization and host-guest interaction, a new supramolecular polymer was constructed in a convenient manner.

Three-dimensional supramolecular polymerization based on pillar[n]arenes (n = 5, 6) and halogen bonding interactions

Three dimensional supramolecular polymerization networks based on pillar[5,6]arenes were constructed both in solution and in the solid state.

Photo-driven morphological transformations of supramolecular polymers actuated by an overcrowded alkene switch

A novel light-responsive supramolecular polymer was actuated by an overcrowded alkene switch. transOAS-Upy could form well-defined nanospheres in chloroform, which would be transformed into worm-like assemblies after UV irradiation.

Supramolecular polymers based on a pillar[5]arene-fused cryptand: design, fabrication and degradation accompanied by a fluorescence change

Novel supramolecular polymers based on a pillar[5]arene-fused cryptand have been constructed easily and conveniently, in which three orthogonal interactions were combined together.

Photoresponsive AA/BB supramolecular polymers comprising stiff-stilbene based guests and bispillar[5]arenes

We report a novel photoresponsive AA/BB supramolecular polymer comprising stiff-stilbene bridged guests and disulfide-bridged bispillar[5]arenes.

Neutral linear supramolecular polymers constructed by three different interactions

Neutral linear supramolecular polymers were constructed by the combination of quadruple hydrogen bonding, pillar[5]arene-based molecular recognition and π–π donor–acceptor interactions.

Construction of supramolecular polymer by enzyme-triggered covalent condensation of CB[8]-FGG-based supramonomer

A rapid and effective enzymatic strategy for the fabrication of a supramolecular polymer is presented for the first time, in which a bifunctional ternary host-guest supramonomer is first prepared followed by subsequent enzymatic coupling of supramonomers.

Pillar-Shaped Macrocyclic Hosts Pillar[n]arenes: New Key Players for Supramolecular Chemistry

In 2008, we reported a new class of pillar-shaped macrocyclic hosts, known as "pillar[n]arenes". Today, pillar[n]arenes are recognized as key players in supramolecular chemistry because of their facile synthesis, unique pillar shape, versatile functionality, interesting host-guest properties, and original supramolecular assembly characteristics, which have resulted in numerous electrochemical and biomedical material applications. In this Review, we have provided historical background to macrocyclic chemistry, followed by a detailed discussion of the fundamental properties of pillar[n]arenes, including their synthesis, structure, and host-guest properties. Furthermore, we have discussed the applications of pillar[n]arenes to materials science, as well as their applications in supramolecular chemistry, in terms of their fundamental properties. Finally, we have described the future perspectives of pillar[n]arene chemistry. We hope that this Review will provide a useful reference for researchers working in the field and inspire discoveries concerning pillar[n]arene chemistry.

Efficient complexation between pillar[5]arenes and neutral guests: from host–guest chemistry to functional materials

This feature article covers the molecular recognition of pillar[5]arenes and neutral guests, and its application in making supramolecular structures, polymers and functional materials.

A cationic water-soluble biphen[3]arene: synthesis, host–guest complexation and fabrication of a supra-amphiphile

The first cationic water-soluble biphen[3]arene was synthesized, which was used to change the aggregation of the amphiphilic guest in water.

Fluorescent nanoassemblies between tetraphenylethenes and sulfonatocalixarenes: a systematic study of calixarene-induced aggregation

We demonstrated a systematic study of calixarene-induced aggregation (CIA) that how and to what extent the structures of hosts and guests affect the assembly behavior by fluorescence spectroscopy.

Phosphonium pillar[5]arenes as a new class of efficient biofilm inhibitors: importance of charge cooperativity and the pillar platform

Inhibition of biofilm formation (MBIC₅₀ = 0.67–1.66 μM) by pillar[5]arene congugates.

Multicavity macrocyclic hosts

Multicavity macrocyclic hosts are host molecules comprising more than one macrocyclic guest binding components connected through multipoint linkages.

Facile construction of fluorescent polymeric aggregates with various morphologies by self-assembly of supramolecular amphiphilic graft copolymers

Facile construction of fluorescent polymeric aggregates with various morphologies was realized by self-assembly of supramolecular amphiphilic graft copolymers.

Porphyrinic supramolecular daisy chains incorporating pillar[5]arene–viologen host–guest interactions

Daisy chains and organogels have been prepared by utilising noncovalent interactions between viologens and pillar[5]arenes together with stacked porphyrins.