A selective and sensitive intramolecular charge transfer (ICT) fluorescent chemosensor was designed for Cu2+ in neutral aqueous solutions of pH 7.0. The design of this totally water-soluble fluorescent chemosensor was based on the binding motif of Cu2+ to aminoacid, which is coupled to an ICT fluorophore bearing a 1,3,4-thiodiazole moiety in the electron acceptor. The formation of a 1:1 complex of Cu2+ to 2 was suggested to lead to fluorescence quenching. The quenching obeyed Stern-Volmer theory in neutral aqueous solution of pH 7.0 for Cu2+ over 5.0 × 10-7 to 3.0 × 105mol·L1, with a quenching constant of 1.8× 105L·mol-1 and a detection limit of 2.0×x 107mol· L-1· The binding of Cu2+ to 2 can be fully reversed by addition of chelator EDTA, affording a reversible sensing performance.
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