Benzo-21-Crown-7/Secondary Ammonium Salt [2]Rotaxanes with Fluoro/Chlorocarbon Blocking Groups

Three threaded structures capped by fluoro/chlorocarbon blocking groups with different sizes were constructed by template synthesis based on the benzo-21-crown-7/secondary ammonium salt recognition motif, as confirmed by ¹H NMR, electrospray mass spectrometry and single crystal X-ray analysis. The transformation from a rotaxane-like entity into a rotaxane was achieved by replacing the end group from the trifluoroacetic ester group to its trichloroacetic ester analogue

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⁺

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⁺

Thermosensitive Phase Behavior of Benzo-21-crown‑7 and Its Derivatives

For designing water-soluble responsive materials, utilizing crown ethers as main building blocks has been rarely explored in contrast to their linear poly­(ethylene glycol) counterparts. In the current study, we report the robust thermoresponsive properties of the benzo-21-crown-7 (<b>B21C7</b>) family with lower critical solution temperature (LCST) and upper critical solution temperature (UCST) behavior. Different substituent groups on the benzene ring exhibit significant effects on water solubility and thermoresponsiveness. <b>B21C7</b> and its cyano derivative display LCST phenomena, while <b>B21C7</b>-based carboxylic acid derivative presents UCST followed by LCST phase behavior. Supramolecular interactions with KCl provide an additional tuning approach for this crown ether system. These results demonstrate that <b>B21C7</b>s can serve as an easily accessible toolbox to develop new thermosensitive systems and prepare thermally responsive materials