ON–OFF Fluorescent Imidazole Derivative for Sensitive and Selective Detection of Copper(II) Ions

A novel multichromophoric hybrid compound, 2-[1-(4-tert-butylphenyl)-4,5-diphenyl-1H-imidazol-2-yl]-6-(pyren-1-yl)quinoline (TDIPQ) has been synthesized as an ON-OFF fluorescent chemosensor for copper(II) ions. Colorless TDIPQ in acetonitrile—water (2:1, v/v) selectively turns yellow along with fluorescence quenching upon addition of copper(II) ions. The fluorescence quenching is directly proportional to the concentration of copper(II) ions. The interaction between TDIPQ and copper(II) was investigated with the aid of UV-Vis, fluorescence, 1H NMR, and MALDI mass spectral techniques. The stoichiometry of the TDIPQ—Cu complex was determined to be 2:1 by Job’s Plot. Under similar experimental conditions, other competitive metal ions had negligible or no interference in the detection ability of TDIPQ. The detection and quantification limits of TDIPQ were estimated at 2 × 10−6 M and 6.2 × 10−6 M. respectively. This method showed an excellent precision of 0.98 ± 0.011 and recovery characteristic of 99.09±1.4%. It is applicable for the quantification of copper(II) in various samples such as drinking water, lab waste water, and soil. A mixture of TDIPQ with the BZA-Co-BZMA polymer can be cast as a film on a glass slide to be used as a sensor device to indicate the presence of copper. Polymer-coated TDIPQ chemosensing property was analyzed by SEM imaging.