金属离子的配位作用影响芳胺抗氧化性能的理论研究

Theoretical Calculation Studies on the Effect of Coordination of Metal Ions on the Antioxidation Properties of Diarylamines

文章利用密度泛函理论研究了金属离子的配位作用对芳胺抗氧化性能的影响。结果表明,选取的四种金属离子K+、Ca2+、Mg2+、Fe3+易与芳胺类模型化合物(DMDPA)配位,且金属离子的氧化性越强,金属与DMDPA的键合能越小;K+的配位作用有助于降低Ar2N—H键的离解能,而Ca2+、Mg2+、Fe3+则使其升高;K+的配位还能够有效降低Ar2NH捕获过氧化自由基反应的活化能,同时在热力学上亦有利于该反应的发生。这表明碱金属与芳胺的协同抗氧化作用可能是因为碱金属离子与芳胺配位导致捕获过氧化自由基反应的速率加快所致。

Density functional theory（DFT）calculations on the effect of coordination of metal ions on the antioxidant performance of diarylamines（DMDPA）are reported here.The results show that the selected four kinds of metal ions,viz.,K^＋,Ca^2＋,Mg^2＋,Fe^3＋,can easily coordinate with a model compound of diarylamine,and the binding energies between the metal ions and DMDPA are related to the oxidizability of metal ions,the stronger the oxidizability of metal ion is,the smaller the binding energy is.The coordination effect of K^＋is conducive to reducing the dissociation energy of Ar2N-H bond,however,Ca^2＋,Mg^2＋and Fe^3＋make it larger.Additionally,the coordination effect of K＋can effectively reduce the activation energy of the reaction of DMDPA with ROO·,and can also make the reaction more favorable in thermodynamics.This suggests that the synergetic antioxidation of alkali metal in lubricating oil containing diarylamines antioxidants could be ascribed to the coordination of the alkali metal ion to the diarylamines and therefore increasing the reaction rate of capturing ROO·radical.