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.

Pillar[5]arene based water-soluble [3]pseudorotaxane with enhanced fluorescence emission for cell imaging and both type I and II photodynamic cancer therapy

Water-soluble [3]pseudorotaxane with enhanced fluorescence emission was successfully constructed and applied in cell imaging and photodynamic cancer therapy.

Spatially Designed Supramolecular Anion Receptors Based on Pillar[5]arene Scaffolds: Synthesis and Halide Anion Binding Properties

Urea-functionalized anion receptors based on brominated functionalized pillar[5]arenes were prepared. The binding affinity toward halide anions was investigated and probed using ¹H NMR titration and isothermal titration calorimetry (ITC). The complexation behavior was affected by the structure of the receptor and the nature of the anionic guest. The synthesized receptors are highly selective toward fluoride resulting in the formation of a 1:2 host-to-guest complex. The anion receptor based on the 1,3-alternate pillar[5]arene regioisomer shows the highest affinity toward fluorine anions. No significant interactions were observed with larger bromine anions. The formation of a self-assembled supramolecular polymer driven by hydrogen bonds in solution was demonstrated by diffusion-ordered spectroscopy (DOSY), ITC, and dynamic light scattering (DLS) measurements. From ITC dilution experiments, we found that the supramolecular polymer self-assembly at higher concentrations is a spontaneous process as indicated by the positive value of Gibbs free energy (ΔG = 12.04 kJ mol^-1).

Organo-macrocycle-containing hierarchical metal-organic frameworks and cages: design, structures, and applications

Developing hierarchical ordered systems is challenging. Using organo-macrocycles to construct metal-organic frameworks (MOFs) and porous coordination cages (PCCs) provides an efficient way to obtain hierarchical assemblies. Macrocycles, such as crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, can be incorporated within MOFs/PCCs and they also endow the resultant composites with enhanced properties and functionalities. This review summarizes recent developments of organo-macrocycle-containing hierarchical MOFs/PCCs, emphasizing applications and structure-property relationships of these hierarchically porous materials. This review provides insights for future research on hierarchical self-assembly using macrocycles as building blocks and functional ligands to extend the applications of the composites.

Host-guest interaction of nitroxide radicals with water-soluble pillar[6]arenes

The host-guest interaction of nitroxide radicals with water-soluble pillar[n]arenes was studied for the first time by electron paramagnetic resonance spectroscopy and NMR spectroscopy. Our results showed that this interaction strongly depended on the 4-substituents of nitroxides and the cavity size of pillar[n]arenes. The host-guest interaction with water-soluble pillar[6]arene WP6 effectively increased the thermodynamic and kinetic stability of nitroxide radical 4-AT toward ascorbic acid, thus expanding its potential biomedical applications.

Construction of a [2]pseudorotaxane and a [3]pseudorotaxane based on perbromoethylated pillar[5]arene/pyridinium iodide ion-pair recognition

Herein we report the preparation of a [2]pseudorotaxane and a [3]pseudorotaxane based on perbromoethylated pillar[5]arene/pyridinium iodide ion-pair recognition.

LCST behavior controlled by size-matching selectivity from low molecular weight monomer systems

LCST behavior was controlled by crown ether–cation recognition motifs via size-matching selectivity.

A dual-responsive hyperbranched supramolecular polymer constructed by cooperative host-guest recognition and hydrogen-bond interactions

A homotritopic pillar[5]arene (H3) containing adenine units was synthesized and employed to interact with a uracil derivative (6-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)hexanenitrile, G) to form a hyperbranched supramolecular polymer. The hyperbranched supramolecular polymer showed a dual stimulus response both to heat and acid/base. The cooperative host-guest binding and hydrogen-bond interactions play a key role in the supramolecular polymerization.

Dynamic hydrogels mediated by macrocyclic host-guest interactions

Hydrogels have attracted increasing research interest in recent years due to their dynamic properties and potential applications in biomaterials. Concurrently, macrocycle-based host-guest interactions have played an important role in the development of supramolecular chemistry. Recently, research towards dynamic hydrogels mediated by various macrocyclic host-guest interactions has been gradually disclosed. In this review, we will outline the burgeoning progress in the development of functional hydrogels mediated by various host molecules, such as cyclodextrins, cucurbit[n]urils, calix[n]arenes, pillar[n]arenes, and other macrocycles. Smart hydrogels with outstanding properties, like biocompatibility, toughness, and self-healing, are mainly focused. We believe that this review will highlight the potential of dynamic hydrogels mediated by macrocycle-based host-guest interactions.

Multi-stimuli-responsive supramolecular gel constructed by pillar[5]arene-based pseudorotaxanes for efficient detection and separation of multi-analytes in aqueous solution

Here, a novel pseudorotaxanes-type crosslinker of a supramolecular polymer network (WP5-PN) has been constructed from a host water-soluble pillar[5]arene (WP5) and a guest naphthalene dimethylamine derivative (PN) via a stepwise process involving multiple non-covalent interactions. The obtained supramolecular polymers were able to transform into a supramolecular polymer gel (WP5-PN-G) and show AIE properties in DMSO-H2O binary solution. Interestingly, due to the dynamic and reversible nature of non-covalent interactions, the resultant supramolecular polymer gels exhibited external stimuli-responsiveness to different parameters, such as temperature, acid-base, competitive guest and mechanical stress. Moreover, WP5-PN-G showed fluorescent response for Fe3+ and Cu2+, while its xerogel showed excellent recyclable separation properties for these metal ions with adsorption rates up to 98.07% and 95.38%, respectively. Moreover, by rational introduction of these metal ions into the WP5-PN-G, corresponding metal ion coordinated metallogels, such as WP5-PN-FeG and WP5-PN-CuG were obtained. These metallogels could selectively and sensitively sense F- and CN-, respectively. The detection limits of these metallogels for F- and CN- were about 1 × 10-8 M. The WP5-PN-G has potential applications in multi-analytes detection and separation as well as fluorescent display materials.

Post-Synthetic Modification of Nonporous Adaptive Crystals of Pillar[4]arene[1]quinone by Capturing Vaporized Amines

Postsynthetic modification in crystalline solids without disruption of crystallinity is very important for exerting control that is unattainable over chemical transformation in solution. This has been achieved in porous crystalline frameworks via solid-solution reactions to endow them with multiple functions. However, this is rather rare in nonporous molecular crystals, especially via solid-vapor reactions. Herein, we report unique solid-vapor postsynthetic modification of nonporous adaptive crystals (NACs) of a pillar[4]arene[1]quinone (EtP4Q1) containing four inert 1,4-diethoxybenzene units and one active benzoquinone unit. Amine vapors that can be physically adsorbed by EtP4Q1 NACs react with the EtP4Q1 backbone via Michael addition with in situ formation of new crystal structures. First, amines are physically adsorbed into cavities of EtP4Q1 molecules and slowly react due to their juxtapsition with the benzoquinone units. Amines that are too bulky to enter EtP4Q1 NACs do not react. Moreover, the process displays both reactant-size and -shape selectivities because of the rigid cavity of EtP4Q1 and the different binding strengths of various amines with EtP4Q1.

Supramolecular control over pillararene-based LCST phase behaviour

Based on the supramolecular interactions between pillar[5]arenes and ionic liquids, supramolecular control was successfully introduced into thermo-responsive systems to adjust LCST phase behaviour in water.

Supramolecular motifs for the self-assembly of monosubstituted pillar[5]arenes with an amide fragment: from nanoparticles to supramolecular polymers

The effects of solvents on the aggregation properties of novel monosubstituted pillar[5]arenes containing an N-alkylamide fragment have been investigated.

Supramolecular Host-Guest System as Ratiometric Fe3+ Ion Sensor Based on Water-Soluble Pillar[5]arene

Developing a specific, ratiometric, and reversible detection method for metal ions is significant to guard against the threat of metal-caused environmental pollution and organisms poisoning. Here a supramolecular host-guest system (WP5⊃G) based on water-soluble pillar[5]arene (WP5) and water-soluble quaternized perylene diimide derivative (G) was constructed. Morphological transformation was achieved during the process of adding WP5 into G aqueous solution, and a fluorescence "turn-off" phenomenon was observed which was caused by supramolecular photoinduced electron transfer (PET). Meanwhile, hydrophobic effect and electrostatic interaction played important roles in this supramolecular process, which was confirmed by isothermal titration calorimeter (ITC) and ζ potential experiments. Furthermore, the supramolecular host-guest system could be a "turn-on" fluorescent probe for Fe³⁺ ion detection through the process of interdicting supramolecular PET. Moreover, the Fe³⁺ ion detection showed specific, ratiometric, and reversible performances with a detection limit of 2.13 × 10^-7 M, which might have great potentials in biological and environmental monitoring.

A novel iodination-triggered competitive coordination mechanism: indirect detection of Hg2+and I−using a simple copillar[5]arene-based fluorometric sensor

Proposed mechanism for the detection of Hg²⁺and I⁻byDBP5.

Preparation and crystal structures of charge-transfer complexes of acyclic host molecules bearing pyrogallol derivatives with paraquat

The complexation of paraquat with adamantane-based molecules possessing two or three pyrogallol derivatives as acyclic host molecules afforded charge-transfer cocrystals with a 2 : 1 host : guest complexation stoichiometry through noncovalent interactions.

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.

A novel functionalized pillar[5]arene for forming a fluorescent switch and a molecular keypad

The sensing mechanism of the sensor PC5 to Fe³⁺.

Selective precipitation of alkyl dihalides using a newly synthesized water-soluble bisphosphorylpillar[5]arene

Bisphosphorylpillar[5]arene H2 binds strongly to alkyldiammonium ions and alkyl dihalides. The halogen bonds between H2 and alkyl dihalides lead to the rapid precipitation of the complex in water.

A multiple-responsive water-soluble [3]pseudorotaxane constructed by pillar[5]arene-based molecular recognition and disulfide bond connection

A multiple-responsive water-soluble [3]pseudorotaxane was constructed by water-soluble pillar[5]arene-based molecular recognition and disulfide bond connection.

The synthesis of pillar[5]arene functionalized graphene as a fluorescent probe for paraquat in living cells and mice

As complex organisms vary in vivo, it remains a challenging task to get fluorescence ‘turn on’ imaging for special targets.

A pillar[6]arene-based [2]pseudorotaxane in solution and in the solid state and its photo-responsive self-assembly behavior in solution

A pillar[6]arene-based [2]pseudorotaxane was constructed in solution and studied in the solid state, and its photo-responsive self-assembly behavior in solution was investigated.

Synthesis of the first amphiphilic pillar[6]arene and its enzyme-responsive self-assembly in water

The first amphiphilic pillar[6]arene was successfully synthesized. It can complex with adenosine triphosphate to form vesicles in water. Moreover, these vesicles are efficiently responsive to phosphatase.

Pillar[5,6]arene-functionalized silicon dioxide: synthesis, characterization, and adsorption of herbicide

A layer of synthetic supramolecular macrocycles, that is, perhydroxyl-pillar[5]arene and perhydroxyl-pillar[6]arene, has been covalently attached to hydrophilic silica supports through Si-O-Si linkages with a coverage of up to 250 μmol pillar[5,6]arenes/g to form novel absorbent hybrid materials. Their adsorption toward a typical herbicide, namely, paraquat, from its aqueous solution has been investigated. Kinetic studies disclosed that paraquat adsorption fits a first-order kinetic model. Equilibrium adsorption data could be explained very well by the Langmuir equation. The pillar[6]arene-modified materials showed more obvious adsorption as compared with pillar[5]arene-modified ones and the saturation adsorption quantity reached about 0.20 mmol of paraquat per gram of materials. The entire process of adsorption was endothermic, and significantly an elevated temperature led to an increase in the adsorption quantity. This new type of pillarene-based adsorbent materials can be considered as a potential adsorbent for harmful substances removal from wastewaters.

A [2]rota[2]catenane, constructed from a pillar[5]arene-crown ether fused double-cavity macrocycle: synthesis and structural characterization

A [2]rota[2]catenane, based on a pillar[5]arene-crown ether fused bicycle, was constructed and its structure was determined crystallographically.

Novel pseudo[2]rotaxanes constructed by the self-assembly of dibenzyl tetramethylene bis-carbamate derivatives and per-ethylated pillar[5]arene

Novel pseudo[2]rotaxanes based on per-ethylated pillar[5]arene and neutral guests G1/G7 were successfully constructed. Particularly, the pseudo[2]rotaxane constructed from per-ethylated pillar[5]arene and G7 showed photoresponsive properties.

A cationic water-soluble pillar[5]arene: synthesis and host–guest complexation with long linear acids

A cationic water-soluble pillar[5]arene has been synthesized and revealed to encapsulate linear acids in neutral, alkaline, and acidic conditions, driven by the hydrophobic and hydrogen bond interactions.

Copillar[5]arene-based supramolecular polymer gel: controlling stimuli–response properties through a novel strategy with surfactant

Cartoon representation of self-assembly pathway of gelator DCP5-16 with G in CD₃CN.

A four-unit [c2]daisy chain connected by hydrogen bonds

A novel four-unit [c2]daisy chain without covalently-bound linear thread was constructed.

Pillar[5]arene-based supramolecular organic frameworks for highly selective CO2-capture at ambient conditions

Low-density, solid-state, porous supramolecular organic frameworks are constructed using pillarenes. The frameworks have a honeycomb-like structure, permanent porosity, high thermal stability, and selective and reversible sorption properties toward CO2. The exceptionally selective CO2-sorption properties (375/1, 339/1) of one framework over N2 and CH4 indicate potential applications in CO2-capture for post-combustion power plants and natural gas sweetening.