A colorimetric sensor for Cu2+ in aqueous solution based on metal ion-induced deprotonation: deprotonation/protonation mediated by Cu2+-ligand interactions

Abstract

A Cu²⁺-specific colorimetric sensor 3 of a 1,8-naphthalimide chromophore integrated with a 2-aminodiphenylamine (2-adpa)-based receptor was designed and synthesized. Sensor 3 had high selectivity and sensitivity for Cu²⁺ in neutral aqueous buffer solution. The analytical detection limit (ADL) was 3.0 × 10⁻⁷ M. Based on the Cu²⁺-induced deprotonation of the diarylamino “NH” moiety, the coordination mode was proposed with 1:1 stoichiometry between 3 and Cu²⁺. These results opened up possibilities for the construction of novel colorimetric sensors with a red-shift absorption in a D–π–A system.