Self-assembly of linear three-ring aromatic thiols on Au(111)

We report on the self-assembly of linear three-ring aromatic thiols on Au(111)/mica substrates. Our study examines terphenylthiol (TPT) derivatives with distinct terminal groups –F (FTPT), –CF₃ (CF₃TPT) and –NO₂ (NTPT) as well as a pyridinebiphenyl (PyBPT) compound. Using complementary surface science techniques – X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM) – we elucidate the structural properties of the resulting self-assembled monolayers (SAMs). The TPT, FTPT, CF₃TPT and PyBPT molecules form densely packed SAMs with hexagonal unit cells exhibiting an area of 21.55 Ų per molecule. For the NTPT SAM, two different molecular arrangements were observed to coexist: a hexagonal structure and a squared structure, with areas per molecule of 21.55 Ų and 42.25 Ų, respectively.