Bifunctional Fluorescent Calix[4]arene Chemosensor for Both a Cation and an Anion

A new fluorogenic cone calix[4]triazacrown-5 (1) bearing two pyrene amide groups and its structural analogue 2 have been prepared. Excited at 343 nm, 1 and 2 reveal excimer emissions at 448 and 472 nm, respectively. When heavy metal ions such as Pb²⁺ and Co²⁺ are bound to 1, the fluorescence intensities of both monomer and excimer are quenched whereas H bonding-assisted F^- binding to 1 gives rise to a quenched monomer emission with little excimer emission change.