Acid/base- and base/acid-switchable complexation between anionic-/cationic-pillar[6] arenes and a viologen ditosylate salt

Two new host-guest complexes between water-soluble anionic pillar[6] arene (WP6) or cationic pillar[6] arene (CP6) and a viologen ditosylate salt G center dot 2TsO were constructed, among which one formed from WP6 and G(2+) ions can be controlled by the sequential addition of an acid and a base (HCl and NaOH, respectively), whereas the other fabricated from CP6 and TsO- ions can be switched through the sequential addition of basic and acidic reagents (NaOH and HCl, respectively).