Variable Ion Selectivity in [<i>n</i>.3.3](1,3,5)Crownophanes: The “Breathing” Process

A series of dithia[n.3.3](1.3.5)crownophanes were synthesized by cesium carbonate-assisted intramolecular cyclization reactions in 10−31% yields. Their complexation behavior exhibits an unusual ion-selectivity preference due to the presence of a “breathing” process of the dithia[3.3]metacyclophane moiety, which indirectly controls the ion selectivity through the adjustment of the cavity size of the crown unit. This breathing mechanism is also supported by observation made in X-ray crystallographic analysis.