A Coumarin-Julolidine conjugated novel Schiff base: synthesis, DFT insights, and evaluation of selective and sensitive dual-responsive fluorescence sensing capabilities with Cu+ and Cu2+ ions

The present research work discloses the synthesis and development of a novel coumarin-julolidine-based Schiff base (4) as a fluorescent probe for detecting copper ions (Cu⁺ and Cu²⁺). Experimental studies, Density Functional Theory (DFT) and TD-DFT computations were performed to investigate the photophysical behaviors of the synthesized chemosensor. The electronic parameters calculated using DFT, including the energy of HOMO-LUMO orbitals and its band gaps, Mulliken atomic charge distribution and electrostatic potential for 1 and probe 4, are presented. We expect the developed chemosensor 4 can be utilized to analyze Cu⁺ and Cu²⁺ ions in biological and environmental samples.