Differential fluorogenic sensing of F− versus CN− based on thiacalix[4]arene derivatives

Thiacalix[4]arene based pyrene-appended fluorescent chemosensors 4 and 5 bearing thiourea moieties have been synthesized which show high selectivity towards fluoride and cyanide ions with different recognition behaviour. The addition of fluoride ions leads to enhancement in fluorescence emission of chemosensors 4 and 5. However, addition of cyanide ions results in ratiometric response with quenching in monomer emission and formation of excimer emission.