Selective Sensing and Determination of Cu2+ Ions in Environmental Samples with Newly Prepared Quinoline based Chemosensors and Confirmation of Results using DFT Molecular Modelling

An efficient turn-off-fluorescence chemosensing method has been developed to detect Cu2+ ions in a variety of samples. Two new quinoline-based chemosensors (QC1 and QC2) have been prepared under the condensation reaction of 8-quinolinecarboxylic acid with derivatives of L-valine. The synthesized chemosensors were characterized by spectroscopic techniques such as 1H NMR, UV, IR, HRMS and CHNS. The HOMO-LUMO orbitals and energy-minimized structures of the chemosensors were developed. The interaction of metal ions with chemosensors and stable structures of complexes were investigated using DFT. The photoluminescence analysis of both chemosensors (QC1 and QC2) showed the fluorescence emission wavelengths on 495 and 512 nm, respectively, for QC1 and QC2. The change in fluorescence emission wavelengths depends on the electronic effects of the substituents on the quinoline ring. The chemosensors showed a high sensitivity for Cu ions; thus, the detection was exhibited in nanomolar levels. The chemosensing studies were performed in the presence of different metal ions and samples taken from other sources.