Investigation on the photodriven catalytic coupling reaction mechanism of p-aminothiophenol on the silver cluster

The catalytic coupling reaction mechanism for the transformation from p-aminothiophenol (PATP) to 4,4'-dimercaptoazobenzene (4,4'-DMAB) on silver cluster was studied by the density functional theory. All the reactants, intermediates, transition states and products were optimized with B3LYP method at 6-311+G (d, p) basis set (the LanL2DZ basis set was used for Ag atom). Transition states and intermediates have been confirmed by the corresponding vibration analysis and intrinsic reactions coordinate (IRC). In addition, nature bond orbital (NBO) and atoms in molecules (AIM) theories have been used to analyze orbital interactions and bond natures. Consistent with the conclusions reported in the literature, the core of obtaining the production of azobenzene according to the coupling reaction of PATP absorbed on Ag-5 clusters is the elimination of two H atoms. Meanwhile, we find that the effect of illumination in that reaction matters a lot. We also found in PATP molecular that the synergistic catalytic effect of S end absorbed on the catalyzer draws dramatically evident under no illumination conditions, while it draws less obvious under light. According to the paper's conclusion, PATP absorbed on the surface of Ag-5 tends to generate azobenzene easily.