Characterize and Mediate Assembly of Triptycenes on Au(111) Surface

Herein, we report the assembly behavior of triptycenes with aldehyde (Trip-1) and amino (Trip-2) groups on pristine and iodine-passivated Au(111) surfaces by a combination of scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and density functional theory (DFT) calculation. On Au(111) surface, Trip-1 forms long trimer chains and two-dimensional islands via aldehyde-aldehyde hydrogen bonding in one dimension and pi-pi stacking of adjacent benzene rings in the other dimension. In contrast, Trip-2 lies as individuals or in disorderly stacked islands. Trip-2 and Trip-1 can be mixed in an arbitrary ratio. And Trip-2 molecules disrupt the ordered self-assembly structure of Trip-1 due to the formation of stronger aldehyde-amino hydrogen bonding. DFT, XPS, and Raman spectra confirm the conformational difference of Trip-1 and -2, as well as the aldehyde-amino hydrogen bonding formation in Trip-1 and Trip-2 mixture. On the iodine-passivated Au(111) surface, Trip-1 forms single-molecule chains and a hexagonal closely packed structure due to iodine interlayer mediation. Trip-2 molecules disrupt the hexagonal closely packed structure of Trip-1.