Synthesis, DFT calculation, and molecular docking simulation of spirooxindoles based Creatinine chemosensor of Cu2+

The synthesis of a Cu 2+ chemosensor is developed via the multi-component reaction of isatin, malononitrile, and creatinine using SiO2-Pr-SO 3 H as a silica nano-catalyst under solvent-free conditions in a short reaction time and high yield. The sensing properties of 2,5-diamino-1-methyl-2-oxo-1,2-dihydro-1H-spiro[indole-3,7-pyrano[2,3- d ]imidazole]-6‑carbonitrile(10 −4 M) are being investigated for various metal ions in CH 3 CN, which selectively detects Cu 2+ ions by a significant decrease in fluorescence emission with a remarkable detection limit of 18 × 10 −6 M. It is evident that Cu 2+ ion is one of the dangerous heavy metals for human health and the environment; therefore, it is very important to identify and detect it easily with an efficient chemosensor. The computational method (DFT) was applied to investigate the ligand's active site for Cu 2+ interaction and to examine the electronic properties of the ligand and the ligand-Cu 2+ complex. Furthermore, geometry optimization, MEP, HOMO-LUMO, and quantum parameters are being analyzed. Molecular docking simulation is used to investigate the synthesized compound's activity against COVID-19 main protease (PDB ID: 6LU7). • The synthesis of a new Cu 2+ chemosensor has been developed via the multi-component reaction of Isatin, Malononitrile, and Creatinine using SiO 2 -Pr-SO 3 H. • The fluorescence properties of compound 4a were studied in the presence of various cations. • DFT calculations (geometry optimization, MEP, HOMO-LUMO, and quantum reactivity) were performed on the structure of compound 4a . • Docking simulation revealed that compound 4a demonstrated higher binding affinity to the COVID-19 main protease compared to favipiravir.