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采用密度泛函理论(DFT)中的B3LYP方法对4-二甲基对巯基苯胺吸附在Ag簇上催化偶联生成4,4’-二巯基偶氮苯(4,4’-DMAB)的反应机理进行理论研究.对比研究了暗反应条件下和光照条件下4-二甲基对巯基苯胺吸附在Ag簇上发生催化偶联生成4,4’-二巯基偶氮苯(4,4’-DMAB)的反应机理.为了了解4-二甲基对巯基苯胺中的巯基端S原子吸附在银簇上对反应的影响,比较研究了4-二甲基对巯基苯胺中的N和S原子同时吸附和仅N原子吸附在银簇上两种条件下的化学反应机理.用自然键轨道(NBO)理论和分子中的原子理论(AIM)分析了分子轨道间相互作用和成键特征.研究结果发现:该反应的关键在于氨基端两个甲基的脱去,在暗反应和光照条件下,两端吸附时第二个甲基脱去所需活化能均很高,分别为57.95、63.88 kcal/mol,表明光照在反应中没起到催化作用.暗反应条件下巯基端吸附起到助催化作用,反应为两端协同催化过程.光照条件下银簇两端协同催化过程表现得不明显.
The B3LYP method in density functional theory (DFT) was applied to the adsorption of 4-dimethyl-mercaptoaniline onto Ag clusters to catalyze the coupling reaction of 4,4’-dimercaptoazobenzene (4,4’-DMAB) Mechanism of the theoretical study.Compared under dark conditions and light conditions, 4-dimethyl-mercaptoaniline adsorption on the Ag cluster catalytic coupling generated 4,4’-dimercaptoazobenzene (4,4’- DMAB) .In order to understand the effect of the S-terminal S-atom on the silver cluster in 4-dimethyl-p-aminothiophenol, the effects of N and S atoms in 4-dimethyl- Adsorption and adsorption of only N atoms on silver clusters.The molecular orbital interactions and bond formation characteristics were analyzed by the theory of natural bond orbital (NBO) and atom theory (AIM) in the molecule.The results It is found that the key of this reaction is the removal of the two methyl groups at the amino end. Under the conditions of dark reaction and light irradiation, the activation energy required for the second methyl group to desorb at both ends is very high, which are respectively 57.95 and 63.88 kcal / mol, indicating that the light did not play a catalytic role in the reaction. Under the conditions of dark thiol adsorption plays a catalytic role , The reaction is a co-catalysis process at both ends, and the synergistic catalysis process at both ends of silver clusters under illumination is not obvious.