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 Fe(3+) ions in mixed aqueous media. Furthermore, the 2-Fe(3+) 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 Fe(3+) and Li(+) triggers an Fe(3+)/Li(+) switchable on-off-on fluorescence chemosensor with negative allosteric regulations.