Tunable Supramolecular Ag + -Host Interactions in Pillar[ n ]arene[ m ]quinones and Ensuing Specific Binding to 1-Alkynes.

We developed an improved, robust synthesis of a series of pillar[ 6 ]arenes with a varying number (0-3) of quinone moieties in the ring. This easy-to-control variation yielded a gradually less electron-rich cavity in going from zero to three quinone units, as shown from the strength of host-guest interactions with silver ions. Such macrocycle-Ag 2 complexes themselves were shown to display an unprecedented, sharp distinction between terminal alkynes, which strongly bound to such complexes, and internal alkynes, internal alkenes and terminal alkenes, which do hardly bind.