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 Å2 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 and 42.25 Å2, respectively.