Synthesis of Oxygen-Free [2]Rotaxanes: Recognition of Diarylguanidinium Ions by Tetraazacyclophanes.

Simple cyclophanes containing four distant amino N atoms or ether O atoms behave as hosts for the threading of guest diarylguanidinium ions. The recognition system exhibits high synthetic flexibility, allowing unique O-free [2]rotaxanes to be synthesized efficiently (yields of up to 80%) through both "threading-followed-by-stoppering" and "clipping" approaches.

Na+ Ions Induce the Pirouetting Motion and Catalytic Activity of [2]Rotaxanes.

We have prepared [2]rotaxanes, the behavior of which as switchable catalysts depends on their pirouetting motion, which can be controlled through the addition and removal of Na+ ions. At least three sequential on/off cycles of a Michael reaction can be performed in situ when using the NaTFPB/[2.2.2]cryptand reagent pair to switch "on" and "off" the catalytic ability of the [2]rotaxanes.

Size effects in the alkali metal ion-templated formation of oligo(ethylene glycol)-containing [2]catenanes.

An investigation into the most suitable alkali metal ions for templating the assembly of [2]catenanes from di-, tri-, and tetra(ethylene glycol)-containing guest diamines and isophthalaldehyde has indicated that Na(+), K(+), and Rb(+) ions are optimal for preparing [2]catenanes containing at least one di(ethylene glycol) unit, two tri(ethylene glycol) units, and at least one tetra(ethylene glycol) unit [in the absence of a di(ethylene glycol) unit], respectively.