Charge-transfer inclusion complex formation of the tropylium cation with prism[6]arenes.

Herein, we report that prism[6]arenes (PrS[6]R) can form charge-transfer (CT) inclusion complexes with tropylium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (G) in chloroform solution with an obvious CT band at 560 nm. Moreover, the CT complex PrS[6]Et⊃G showed Cl-/Ag+ responsiveness which can be easily monitored by the naked eye.

LCST phase behavior of benzo-21-crown-7 with different alkyl chains.

The introduction of hydrophobic units into crown ethers can dramatically decrease the critical transition temperature of LCST and realize macroscopic phase separation at low to moderate temperature and concentration. Minor modifications in the chemical structure of crown ethers (benzo-21-crown-7, B21C7s) can effectively control the thermo-responsive properties.

Characterization of supramolecular gels.

Supramolecular gels are a fascinating class of soft materials. Their gelators can self-assemble into nano- or micro-scale superstructures, such as fibers, ribbons, sheets and spheres in an appropriate solvent, thereby resulting in the formation of 3D networks. The dynamic and reversible nature of the non-covalent interactions that contribute to the formation of these network structures together gives these supramolecular gels the inherent ability to respond to external stimuli. However, the dynamic nature of supramolecular gels, which endows them with unique properties, makes their characterization diversified at the same time. Therefore, we present here a review summarizing various methods for characterizing supramolecular gels, including nuclear magnetic resonance spectroscopy, computational techniques, X-ray techniques, microscopy techniques, dynamic light scattering, thermal analysis, and rheology. Based on the gelation mechanisms and influencing factors of supramolecular gels, suitable and sufficient characterization methods should be carefully employed to make full use of their respective advantages to better investigate these materials.

A sugar-functionalized amphiphilic pillar[5]arene: synthesis, self-assembly in water, and application in bacterial cell agglutination.

A novel sugar-functionalized amphiphilic pillar[5]arene containing galactose groups as the hydrophlic part and alkyl chains as the hydrophobic part was designed and synthesized. It self-assembles in water to produce nanotubes as confirmed by TEM, SEM, and fluorescence microscopy. These nanotubes, showing low toxicity to both cancer and normal cells, can be utilized as excellent cell glues to agglutinate E. coli. The existence of galactoses on these nanotubes provides multivalent ligands that have high affinity for carbohydrate receptors on E. coli.

A water-soluble pillar[6]arene: synthesis, host-guest chemistry, and its application in dispersion of multiwalled carbon nanotubes in water.

The first water-soluble pillar[6]arene was synthesized. Its water solubility can be reversibly controlled by changing the pH. This solubility control was used in reversible transformations between nanotubes and vesicles and dispersion of multiwalled carbon nanotubes in water.

Pillar[6]arene/paraquat molecular recognition in water: high binding strength, pH-responsiveness, and application in controllable self-assembly, controlled release, and treatment of paraquat poisoning.

The complexation between a water-soluble pillar[6]arene (WP6) and paraquat (G1) in water was investigated. They could form a stable 1:1 [2]pseudorotaxane with an extremely high association constant of (1.02 ± 0.10) × 10(8) M(-1) mainly driven by electrostatic interactions, hydrophobic interactions, and π-π stacking interactions. This molecular recognition has not only high binding strength but also pH-responsiveness. The threading and dethreading processes of this [2]pseudorotaxane could be reversibly controlled by changing the solution pH. This novel recognition motif was further used to control the aggregation of a complex between WP6 and an amphiphilic paraquat derivative (G2) in water. The reversible transformations between micelles based on G2 and vesicles based on WP6⊃G2 were realized by adjusting the solution pH due to the pH-responsiveness of WP6. The controlled release of water-soluble dye molecules from the vesicles could be achieved by the collapse of the vesicles into the micelles upon changing the solution pH to acidity. Additionally, the high binding affinity between WP6 and paraquat could be utilized to efficiently reduce the toxicity of paraquat. After the formation of a stable host-guest complex between WP6 and paraquat, less opportunity was available for paraquat to interact with the reducing agents in the cell, which made the generation of its radical cation more difficult, resulting in the efficient reduction of paraquat toxicity.

Pillar[6]arene-based photoresponsive host-guest complexation.

The trans form of an azobenzene-containing guest can complex with a pillar[6]arene, while it cannot complex with pillar[5]arenes due to the different cavity sizes of the pillar[6]arene and the pillar[5]arenes. The spontaneous aggregation of its host-guest complex with the pillar[6]arene can be reversibly photocontrolled by irradiation with UV and visible light, leading to a switch between irregular aggregates and vesicle-like aggregates. This new pillar[6]arene-based photoresponsive host-guest recognition motif can work in organic solvents and is a good supplement to the existing widely used cyclodextrin/azobenzene recognition motif.

Host-Guest Complexations Between Pillar[6]arenes and Neutral Pentaerythritol Derivatives.

It is demonstrated that three kinds of neutral pentaerythritol derivatives possess promising host-guest complexations with pillar[6]arenes both in solution and in the solid state. The inclusion structures were characterized by NMR spectroscopy and X-ray crystallography. The complexation properties in different solvents were also investigated.

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

Herein we demonstrate that three dimensional supramolecular polymerization networks were constructed both in solution and in the solid state by the combination of pillar[5,6]arene-based host-guest complexes and 1,4-diiodotetrafluorobenzene involving halogen bonding systems.

Preparation of cross-linked supramolecular polymers based on benzo-21-crown-7/secondary ammonium salt host-guest interactions.

We found that TC7 not only self-assembles into one-dimensional supramolecular aggregates in chloroform, but also forms cross-linked supramolecular polymers via host-guest complexation between benzo-21-crown-7 and secondary ammonium salts. Compared with one-dimensional linear supramolecular polymers, soft and long viscous fibers were pulled out from a concentrated solution of cross-linked supramolecular polymers as a result of higher viscosity and lower diffusion coefficients.

Stereoselective Synthesis of Pillar[4]arene[1]cis-diepoxy-p-dione and X-Ray Crystal Structure of Host-Guest System.

Herein, we successfully develop a novel route to give rise to polarity for the pillararenes by the introduction of oxygenated functionalities into pillar[5]arene to stereoselectively synthesize the pillar[4]arene[1]cis-diepoxy-p-dione. Its host-guest properties with different dinitrile molecules were also investigated and characterized by NMR and X-ray crystallography.

Proton transfer in host-guest complexation between a difunctional pillar[5]arene and alkyldiamines.

Host-guest complexation between a novel difunctional pillar[5]arene-based host H and alkyldiamines was fully investigated in both solution and the solid state. Proton transfer from the carboxylic acid groups to the amine units occurred in the principle by undergoing an acid-base reaction. Driven by the cooperativity of electrostatic interactions, multiple C-H···π interactions, and H-bonds, the guests penetrated into the cavity of H to form pseudorotaxane-type inclusion complexes with relatively high binding affinities.

Formation of a pillar[5]arene-based [3]pseudorotaxane in solution and in the solid state.

It was demonstrated that a novel [3]pseudorotaxane could be separated by column chromatography during the synthesis of a copillar[5]arene. Single crystal X-ray analysis revealed that this [3]pseudorotaxane consisted of the copillar[5]arene and its monomer in a molar ratio of 2 : 1.

Carbon nanotube/biocompatible bola-amphiphile supramolecular biohybrid materials: preparation and their application in bacterial cell agglutination.

Supramolecular biohybrid materials were successfully constructed driven by non-covalent interactions between three biocompatible bolaform amphiphiles and single walled carbon nanotubes (SWNTs). The existence of galactoses in these supramolecular systems endowed the hybrid materials with interesting bio-function. By introducing the SWNTs as semi-flexible platforms, these supramolecular biohybrid materials display excellent agglutination ability for E. coli.

LCST-type phase behavior induced by pillar[5]arene/ionic liquid host-guest complexation.

The host-guest complex of dipropoxypillar[5]arene and an ionic liquid 1,3-dimethylimidazolium iodide is found to exhibit a lower critical solution temperature (LCST)-type phase transition in chloroform. This LCST-type phase behavior can be conveniently modulated by experimental parameters and can be easily combined with the ionic liquid for potential application in product and educt separation.

Syntheses of a pillar[4]arene[1]quinone and a difunctionalized pillar[5]arene by partial oxidation.

A pillar[4]arene[1]quinone and a difunctionalized pillar[5]arene have been synthesized by partial oxidation.

Complexation between pillar[5]arenes and a secondary ammonium salt.

We demonstrate that n-octylethyl ammonium hexafluorophosphate (G) can thread through the cavity of 1,4-dimethoxypillar[5]arene to form a [2]pseudorotaxane with a binding constant of 1.09 (±0.31) × 10(3) M(-1) in chloroform. The formation of this threaded structure has been confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray single crystal analysis. The complexation between 1,4-dimethoxypillar[5]arene and G in chloroform can be switched off by adding Cl(-). For comparison, the complexation between 1,4-bis(n-propoxy)pillar[5]arene and G has also been investigated.

A non-symmetric pillar[5]arene-based selective anion receptor for fluoride.

A novel non-symmetric pillar[5]arene-based anion receptor containing multiple triazole anion-binding sites was designed and synthesized. It has high affinity and selectivity for the fluoride anion.

Four constitutional isomers of BMpillar[5]arene: synthesis, crystal structures and complexation with n-octyltrimethyl ammonium hexafluorophosphate.

Four constitutional isomers of BMpillar[5]arene were prepared from 1-butoxy-4-methoxybenzene and they showed different binding abilities with n-octyltrimethyl ammonium hexafluorophosphate.

Formation of a cyclic dimer containing two mirror image monomers in the solid state controlled by van der Waals forces.

Two new copillar[5]arenes were prepared. They are arranged in two completely different motifs, a cyclic dimer containing two monomers with two different conformations that are mirror images of each other and linear supramolecular polymers in the solid state. Not only has it been shown that to form this kind of dimer is a unique feature associated with pillar[5]arene macrocycles but also it was demonstrated that weak van der Waals forces can be used to control the self-organization of monomers during their supramolecular polymerization process.