Tactfully improve the antioxidant activity of 2'-hydroxychalcone with the strategy of substituent, solvent and intramolecular hydrogen bond effects

The substituent and solvent effects on the antioxidant activity of 2'-hydroxychalcone (2'Cha) were sys-tematically explored in gas and three solvent phases by designing six novel compounds (2'Cha-3'NH2, 2'Cha-4'NH2, 2'Cha-5'NH2, 2'Cha-3'CN, 2'Cha-4'CN, and 2'Cha-5'CN) based on the density functional the-ory (DFT) approach. Significant parameters involved in three primary antioxidant mechanisms, namely the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were computed to confirm the thermodynamically pre-ferred reaction pathway in different media. Besides, 4'-hydroxychalcone (4'Cha) was introduced to unveil the intramolecular hydrogen bond (IHB) effect on the radical scavenging capacity of 2'Cha utilizing the DFT and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) ultraviolet-visible (UV-Vis) spectroscopic methods. Energy barriers and kinetic parameters for HAT reaction of 2'Cha and 4'Cha with hydroperoxyl (HOO?) radical were calculated to further compare the radical-trapping process. The photophysical properties of 2'Cha in benzene, chlorobenzene and ethanol are in good agreement with the measured experimental data and the excited-state antiradical capacity improving mechanism was also confirmed experimentally. The current work not only provides valuable guidance for synthesizing high-efficiency antioxidants but also exploits the potential application fields for 2'Cha. (C) 2022 Elsevier B.V. All rights reserved.