Synthesis, crystal structure and complexation behaviour study of an efficient Cu²⁺ ratiometric fluorescent chemosensor based on thiacalix[4]arene

A new thiacalix[4]arene based fluorescent chemosensor L bearing two pyrenyl groups in a 1,3-alternate conformation has been synthesized, and its metal ion-binding and fluorescence-sensing properties were investigated in ethanol. The designed chemosensor L exhibited high selectivity toward Cu2+ ions versus other tested metal ions with a detection limit of up to 1.44×10−7 M. The chemosensor L was capable of acting as an efficient ratiometric fluorescent chemosensor at low ion concentration or as a fluorescence quenching type chemosensor due to the PET and heavy atom effects operating in high ionic strength solution. Further studies revealed that chemosensor L acted as a reversible sensor in the presence of Cu2+ and ethylenediamine.