A DFT study of the interaction between butein anion and metal cations (MÂ =Â Mg2+, Cr2+, Fe2+, and Cu2+): Taking an insight into its chelating property

Butein, a chalcone compound isolated from Dalbergia odorifera T. Chen, can inhibit lipid peroxidation induced by metal cations through its chelating property. In order to give an insight into the chelate property of butein, the geometries and electronic properties of metal-butein complexes (M = Mg2+, Cr2+, Fe2+, and Cu2+) are investigated by using density functional theory method in this paper. The natural bond orbitals (NBO) are also calculated to analyze the charge transfer between the metal cations and butein anion. The results find that the oxygen atom of 2′ and 9 position is the favored coordination site for all metal cations both in gas phase and in water phase, and the sequence of binding strength is Cu2+ > Cr2+ > Fe2+ > Mg2+, which is accordance with the quantity of charges transferred from metal cation to butein ligand. In addition, the Cu2+-butein complex has the lowest HOMO-LUMO gap, and the Fe2+-O2′O9 complex has the largest HOMO-LUMO gap.