A Fluorescent Chemosensor for Detection pH and Cu2+ Ion Base on 7-((2-Aminoethyl)amino)-5-Bromo-6-Hydroxy-1-Methylquinolin-1-ium-3-Sulfonate: Experimental and DFT Calculation

Abstract

A quinoline derivative 7-((2-aminoethyl)amino)-5-bromo-6-hydroxy-1-methylquinolin-1-ium-3-sulfonate (QEt) containing quinoline ring, -sulfonate, -OH phenol, and amine groups was synthesized and studied luminescence properties. The aqueous solutions QEt 10µM change luminescence color from green (λem=490nm) to yellow (λem=563nm) as increasing pH and the intensity at a peak of 563 nm is linearly proportional with pH value in the range of pH = 3,0 -4,0. The QEt solutions can be used as chemosensor for Cu2+ with LOD value at 0.66 . Along with the experiment, the structure, the absorption and emission spectra of QEt have been investigated by TD-DFT calculation. The result shows that the absorption band centered at 420 nm is due to the electron transition from HOMO to LUMO (π → π*). The results also help to assign emission band centered at 490nm is due to the S1 → S0 transition (LUMO → HOMO singlet transition), at 563 nm is due to the T2 → S0 transition (LUMO → HOMO-1 triplet transition). The dependence of relative intensity of each emission peak on pH, which is experimentally recorded, is explained based on the results of theoretical TD-DFT calculation.

Synthesis, DFT studies on a series of tunable quinoline derivatives

“…41 These derivatives have been observed to effectively detect hydrazine 42 effectively and have recently been used to detect various anions and cations. [43][44][45][46][47] Selecting an optimal uorescence probe requires consideration of quantum yield, absorption/emission wavelengths, photo stability, chemical stability, and Stokes shi. New probes are continually being developed.…”