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

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