A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu2+ cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu2+ over a wide range of other cations. The solution of 1 (10 μmol/L) upon addition of Cu2+ displayed distinguishing pink color compared with other cations including K+, Ni2+, Ca2+, Mn2+, Na+, Sr2+, Zn2+, Co2+, Cd2+, Mg2+, Cr3+, Ag+, and Ba2+, indicating the sensitivity and selectivity of 1 to Cu2+. Thus, the advantage of this assay is that naked-eye detection of Cu2+ becomes possible. Moreover, among these metal ions investigated, only Cu2+ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl2 in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu2+ revealed the formation of a 2:1 metal-ligand complex through the metal coordination interaction.