A reversible fluorescent Hg2+/K+ switch that works as keypad lock in the presence of F- ion

A thiacalix[4]arene based fluorescent chemosensor 3 of 1,3-alternate conformation bearing two dansyl groups and a crown-5 ring behaves as an On-Off'' reversible switch for two chemical inputs Hg2+ and K+ ions and mimics a molecular level keypad lock in the presence of F- ions.