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

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