A 15-crown-5-ether-based supramolecular hydrogel with selection ability for potassium cations via gelation and colour change.

We developed a novel supramolecular hydrogelator possessing a benzo-15-crown-5 (B15C5) moiety. The hydrogelator can detect colourless potassium cations (K + ) via easily readable gelation and colour change arising from a change in the molecular assembling ability through host-guest interactions between B15C5 and K + , which afford a B15C5/K + /B15C5 sandwich complex.