title: Theoretical study of coupling p-aminothiophenol to hydroazo- and azo-adducts on Au(111).
abstract: Aminothiophenol/Au(111) has been adopted as an exemplary model in plasmonics research, including surface-enhanced Raman spectroscopy, due to its high plasmonic-induced spectral-signal enhancement. The present work was aimed at clarifying whether aminothiophenol on Au(111) is chemically stable in the absence of any photo- and plasmonic-induced effects. Briefly, first-principles calculations were employed to track the detailed mechanism of oxidative coupling of p-aminothiophenol (PATP) to its azo-adduct with an N = N bond, i.e., p,p'-dimercaptoazobenzene (DMAB). Our results show the following: first, in the presence of adsorbed O2, PATP fractures its N-H bond and transfers the hydrogen to a nearby oxygen. This pathway is more favorable than the transfer of H to Au, but the activation barrier of 0.9 eV is still too high for the reaction to occur in the absence of thermal-, photo-, or plasmonic-activation. If this bar can be lifted, two such dehydrogenated PATP can couple themselves to form an adduct with a N-N bond, i.e., p,p'-dimercaptohydroazobenzene (DMHAB), and this reaction is exoergic with an energy barrier of 0.57 eV. Again, this step is slow in the absence of moderate thermal activation or photo-/plasmonic-activation. Finally, dehydrogenation of DMHAB gives the azo-adduct of DMAB, and this reaction is spontaneous, with no energy barrier.
authors.affiliation: Material Simulation and Computing Laboratory, Department of Physics, Hebei Normal University of Science and Technology, Qinghuangdao, 066004, China. xiufenglang@hevttc.edu.cn.|Beijing Computational Science Research Center, Beijing, 100094, China. xiufenglang@hevttc.edu.cn.
authors.forename: Xiufeng
authors.initials: X
authors.lastname: Lang
authors.affiliation: Material Simulation and Computing Laboratory, Department of Physics, Hebei Normal University of Science and Technology, Qinghuangdao, 066004, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Material Simulation and Computing Laboratory, Department of Physics, Hebei Normal University of Science and Technology, Qinghuangdao, 066004, China.
authors.forename: Siyan
authors.initials: S
authors.lastname: Liu
authors.affiliation: Material Simulation and Computing Laboratory, Department of Physics, Hebei Normal University of Science and Technology, Qinghuangdao, 066004, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Zhao
authors.affiliation: Chengdu Green Energy and Green Manufacturing Technology R&D Center, Sichuan, 610207, China.
authors.forename: Woon-Ming
authors.initials: WM
authors.lastname: Lau
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D013438:Sulfhydryl Compounds; C568766:p,p'-dimercaptoazobenzene; D006046:Gold; C064316:4-aminothiophenol
keywords: Au(111); First-principles calculations; Self-coupling; p-Aminothiophenol