Exploration of simple and economic D-π-A- chalcone in selective Fe3+ metal sensing via PET quenching effect in water as a medium and mechanistic study using DFT calculations

Chalcone with high conjugation is a key structural motif in biologically active molecules and has found utility as a dye. These molecular frameworks provide coordination sites for metal ions, attracting scientific interest worldwide. Chalcone (3g) was synthesized using the Claisen-Schmidt condensation as a good donor-pi-acceptor system (D-π-A), that showed intramolecular charge transfer (ICT). Chalcone 3g was soluble in water and showed maxima in UV visible and fluorescence emission spectra, and it also exhibited a broad-spectrum peak at 572 nm. Chalcone 3g showed the detection of different metal ions like Li+, Na+, K+, Mg2+, Cu2+, Zn2+, Fe3+, and Al3+ions in UV-visible and fluorescence spectroscopy while able to specific detection of Fe3+ ions at 572 nm among all other metals with high sensing properties and detection limit. An increase in the metal ion concentration gradually quenched the absorption of chalcone 3g due to the restriction in internal charge transfer. We performed Job's plot to obtain the stoichiometry of chalcone 3g with Fe3+ metal, which was observed to be a 1:1 ratio (LOD and LOQ). A study of chalcone 3g coated filter paper strip was performed, which helped detect Fe3+ ions with reduced colour intensity. Chalcone 3g and metal complexes were calculated theoretically using a Density Functional Theory (DFT) with the B3LYP module of the DMol3. This study suggested that the complexation of 3g and Fe3+ found stable. Herein, we are reporting a simpler chalcone for selective metal ions detection with low LOD and LOQ, which can be helpful in the further development of an easy and convenient metal-sensing fluorescent probe.