Concentration-Dependent Fluorescence Emission of Quercetin

Quercetin (Q) is an important antioxidant with high bioactivity and the potential of being used as SARS-CoV-2 inhibitor. The fluorescence (FL) emission from Q solutions made different polar non-polar solvents (methanol, acetone, chloroform) was measured compared FL powder crystals. In spectra concentration, well in solid state, two features, at 615 nm 670 nm, were observed. As solution concentration decreases, intensity those peaks decreases a peak 505 arises. low displayed only that peak. Calculations for molecule each solvent, performed using time-dependent density functional theory (TDDFT), show associated excited state intramolecular proton transfer (ESIPT) –OH3 group proton. Our calculations also feature which observed concentrated solutions, related to –OH5 transfer.