Abstract
The antioxidant and/or prooxidant properties of flavonoids are strongly dependent on their redox metal chelating capacity as well as on the number and positions of hydroxyl groups. In this work the interaction between Cu(II) ion and the set consisting of four flavonoids (myricetin, morin, taxifolin and 3',4'-dihydroxyflavone) is investigated using density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM). Several potential Cu(II) acceptor sites are considered with respect to the number and positions of hydroxyl (and keto) functional groups within the particular flavonoid moiety. Suitability of the particular Cu(II) acceptor site is discussed from the energetics point of view, i.e. overall stability and interaction energies, electronic transitions are characterized and compared to experimental UV-Vis spectra in DMSO. The nature of the formed Cu-flavonoid chemical bonds is inspected using the bond critical point (BCP) analysis under the formalism of Bader's QTAIM method and the oxidation state of Cu is estimated with respect to the localized d-orbitals and d-populations. An impact of explicit DMSO solvent effects are considered as well. (C) 2020 Elsevier B.V. All rights reserved.