A novel intramolecular charge transfer fluorescent chemosensor highly selective for Cu 2+ in neutral aqueous solutions

A selective and sensitive intramolecular charge transfer (ICT) fluorescent chemosensor was designed for Cu 2+ in neutral aqueous solutions of pH 7.0. The design of this totally water-soluble fluorescent chemosensor was based on the binding motif of Cu 2+ 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 Cu 2+ to 2 was suggested to lead to fluorescence quenching. The quenching obeyed Stern-Volmer theory in neutral aqueous solution of pH 7.0 for Cu 2+ over 5.0 × 10 −7 to 3.0 × 10 −5 mol·L −1 , with a quenching constant of 1.8 × 10 5 L·mol −1 and a detection limit of 2.0 × 10 −7 mol·L −1 . The binding of Cu 2+ to 2 can be fully reversed by addition of chelator EDTA, affording a reversible sensing performance.