Thiacalix[4]crown based optical chemosensor for Fe3+, Li+ and cysteine: a Fe3+/Li+ ion synchronized allosteric regulation

A heteroditopic chemosensor 2 based on a thiacalix[4]crown with a 1,3-alternate conformation has been synthesized and shows a selective fluorescence turn-off response with Fe3+ ions in mixed aqueous media. Furthermore, the 2-Fe3+ complex can be used as a chemosensing system for the detection of Li+ and cysteine based on two different approaches. Moreover, the sequence addition of Fe3+ and Li+ triggers an Fe3+/Li+ switchable on-off-on fluorescence chemosensor with negative allosteric regulations.