On-off switchable binuclear chemosensor based on thiacalix[4]crown armed with pyrene moieties

Abstract

A new fluorescent “on–off” switchable chemosensor 2 based on a thiacalix[4] arene with a 1,3‐alternate conformation and two different types of cation binding sites has been synthesized. Two pyrene moieties linked to a cation recognition unit composed of two imine groups form a strong excimer in solution. Of the metal ions tested, the fluorescence of 2 was strongly quenched by Hg²⁺, Pb²⁺ and Cu²⁺ ions. The fluorescence was revived by the addition of only K⁺ to the Cu²⁺ ligand complex. Thus, metal‐ion exchange triggers an “on–off” switchable fluorescent chemosensor.