Theoretical investigations of the catalytic antioxidation mechanism of diarylamine and the coordination effects of Fe(iii) and Fe atoms

Diarylampine radical-trapping antioxidants (RTA) are widely used in petrochemical products. Herein, density functional theory calculations are used to investigate the catalytic oxidation inhibition mechanism of the highly effective antioxidant diarylamine (Ar₂NH). The coordination effects of Fe(III) and Fe atoms on antioxidation are also investigated. These results indicate that Ar₂NH is activated by reacting with ROO˙ and that oxygen may serve as a catalyst to participate in the reaction. Ar₂NOR can be decomposed by transferring the β-site hydrogen to the ROO˙ radical, resulting in the formation of Ar₂N˙. However, the thermal decomposition of Ar₂NOR is difficult. The resulting Ar₂N˙ can react with an R˙ radical to regenerate Ar₂NH, which reenters the reaction system to complete the catalytic cycle. The detailed catalytic mechanism is feasible, which could explain the high efficiency of Ar₂NH preferably. Additionally, the coordination of Fe(III) and Fe atoms could improve the antioxidant performance of Ar₂NH by enhancing its radical scavenging ability in practical situations, especially Fe(III).