Chemically-Responsive Complexation of A Diquaternary Salt with Bis(<i>m</i>‑phenylene)-32-Crown-10 Derivatives and Host Substituent Effect on Complexation Geometry

A chemically responsive diquaternary salt with π-extended surface was made. The host–guest complexation with chemo-responsiveness between three bis(<i>m</i>-phenylene)-32-crown-10 (BMP32C10) derivatives and this diquaternary salt guest was studied through the sequential addition of basic and acidic reagents (diethylamine and trifluoroacetic acid, respectively). Furthermore, the host-substituent effect on the complexation geometries of these three host–guest complexes, from taco to taco-type threaded to threaded structures by changing the substituent on BMP32C10 as shown by crystal structures, was also addressed

Redox-Responsive Complexation between a Pillar[5]arene with Mono(ethylene oxide) Substituents and Paraquat

Host–guest complexation between a pillar[5]arene with mono(ethylene oxide) substituents and paraquat was studied. We demonstrated that this pillar[5]arene can form a 1:1 complex with paraquat in solution and in the solid state. The formation of this complex was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray analysis. Furthermore, this complexation can be reversibly controlled through the sequential addition and removal of Zn powder. The host substituent effect on the complexation ability was also addressed

A Dual-Responsive Supra-Amphiphilic Polypseudorotaxane Constructed from a Water-Soluble Pillar[7]arene and an Azobenzene-Containing Random Copolymer

Macromolecular supra-amphiphiles refer to a kind of macromolecular amphiphiles whose hydrophlic and hydrophobic parts are connected by noncovalent forces. They have applications in various fields, such as drug delivery, sensor systems, and biomedical materials. Here we report a novel molecular recognition motif between a new thermoresponsive water-soluble pillar[7]­arene (<b>WP7</b>) and an azobenzene derivative. Furthermore, we utilized this recognition motif to construct the first pillararene-based supra-amphiphilic polypseudorotaxane which can self-assemble to form vesicles in water. Due to the dual-responsiveness of the molecular recognition motif (the thermoresponsiveness of <b>WP7</b> and photoresponsiveness of azobenzene), the reversible transformations between solid nanospheres based on the self-assembly of the polymer backbone and vesicles based on the self-assembly of the supra-amphiphilic polypseudorotaxane were achieved by adjusting the solution temperature or UV–visible light irradiation. These dual-responsive aggregation behaviors were further used in the controlled release of water-soluble dye calcein molecules

Complexation between Pillar[5]arenes and a Secondary Ammonium Salt

We demonstrate that <i>n</i>-octylethyl ammonium hexafluorophosphate (<b>G</b>) 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) × 10³ 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 <b>G</b> in chloroform can be switched off by adding Cl^–. For comparison, the complexation between 1,4-bis(<i>n</i>-propoxy)pillar[5]arene and <b>G</b> has also been investigated

Chemically-Responsive Complexation of A Diquaternary Salt with Bis(<i>m</i>‑phenylene)-32-Crown-10 Derivatives and Host Substituent Effect on Complexation Geometry

A chemically responsive diquaternary salt with π-extended surface was made. The host–guest complexation with chemo-responsiveness between three bis(<i>m</i>-phenylene)-32-crown-10 (BMP32C10) derivatives and this diquaternary salt guest was studied through the sequential addition of basic and acidic reagents (diethylamine and trifluoroacetic acid, respectively). Furthermore, the host-substituent effect on the complexation geometries of these three host–guest complexes, from taco to taco-type threaded to threaded structures by changing the substituent on BMP32C10 as shown by crystal structures, was also addressed

Redox-Responsive Complexation between a Pillar[5]arene with Mono(ethylene oxide) Substituents and Paraquat

Host–guest complexation between a pillar[5]arene with mono(ethylene oxide) substituents and paraquat was studied. We demonstrated that this pillar[5]arene can form a 1:1 complex with paraquat in solution and in the solid state. The formation of this complex was confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and single crystal X-ray analysis. Furthermore, this complexation can be reversibly controlled through the sequential addition and removal of Zn powder. The host substituent effect on the complexation ability was also addressed

Complexation between Pillar[5]arenes and a Secondary Ammonium Salt

We demonstrate that <i>n</i>-octylethyl ammonium hexafluorophosphate (<b>G</b>) 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) × 10³ 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 <b>G</b> in chloroform can be switched off by adding Cl^–. For comparison, the complexation between 1,4-bis(<i>n</i>-propoxy)pillar[5]arene and <b>G</b> has also been investigated

pH-Responsive Supramolecular Control of Polymer Thermoresponsive Behavior by Pillararene-Based Host–Guest Interactions

We demonstrate precise control of the lower critical solution temperature (LCST) behavior of a thermoresponsive polymer in water by pillararene-based host–guest interactions. The LCST value of the polymer increases upon the stepwise addition of either of the two pillararene hosts. On account of the pH-responsiveness of the pillararene-based host–guest interactions, the recovery of the LCST is achieved by treatment with acid, reflecting the pH-responsive supramolecular control of the LCST

A Supramolecular Cross-Linked Conjugated Polymer Network for Multiple Fluorescent Sensing

A supramolecular cross-linked network was fabricated and demonstrated to act as a multiple fluorescent sensor. It was constructed from a fluorescent conjugated polymer and a bisammonium salt cross-linker driven by dibenzo[24]­crown-8/secondary ammonium salt host–guest interactions. Compared with the conjugated polymer, the network has weak fluorescence due to the aggregation of polymer chains. Thanks to the multiple stimuli-responsiveness of host–guest interactions, the fluorescence intensity of the system can be enhanced by four types of signals, including potassium cation, chloride anion, pH increase, and heating. Hence, the network can serve as a cation sensor, an anion sensor, a pH sensor, and a temperature sensor. It can be used in both solution and thin film. Interestingly, exposure of a film made from this supramolecular cross-linked network to ammonia leads to an increase of fluorescence, making it a good candidate for gas detection

A Benzo-21-Crown-7/Secondary Ammonium Salt [<i>c</i>2]Daisy Chain

A [<i>c</i>2]daisy chain has been constructed from a heteroditopic monomer based on the benzo-21-crown-7/secondary ammonium salt recognition motif as shown by single crystal X-ray analysis. It has been further demonstrated that the complexation behavior of this heteroditopic monomer in solution can be controlled by changing the solution pH or adding/removing K⁺