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

Abstract

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 × 10^−5 mol·L^−1, with a quenching constant of 1.8 × 10⁵ L·mol^−1 and a detection limit of 2.0 × 10^−7 mol·L^−1. The binding of Cu²⁺ to 2 can be fully reversed by addition of chelator EDTA, affording a reversible sensing performance.

Keywords

fluorescent chemosensor / Cu2+ / fluorescence quenching / intramolecular charge transfer / 4-thiodiazole