Molecular Self-Assembly Driven by On-Surface Reduction: Anthracene and Tetracene on Au(111)
J. Krüger, F. Eisenhut, T. Lehmann, J. M. Alonso, J. Meyer, D. Skidin, R. Ohmann, D. A. Ryndyk, D. Pérez, E. Guitián, D. Peña, F. Moresco, and G. Cuniberti
J. Phys. Chem. C 121, 20353 (2017)
Epoxyacenes adsorbed on metal surfaces form acenes during thermally induced reduction in ultrahigh vacuum conditions. The incorporation of oxygen bridges into a hydrocarbon backbone leads to an enhanced stability of these molecular precursors under ambient condition; however, it has also a distinct influence on their adsorption and self-assembly on metal surfaces. Here, a low-temperature scanning tunneling microscopy (LT-STM) study of two different epoxyacenes on the Au(111) surface at submonolayer coverage is presented. Both molecules show self-assembly based on hydrogen bonding. While for the molecules with a single epoxy moiety nanostructures of three molecules are formed, extended molecular networks are achieved with two epoxy moieties and a slightly higher surface coverage. Upon annealing at 390 K, the molecules are reduced to the respective acene; however, both systems keep a similar assembled structure. The experimental STM images supported by theoretical calculations show that the self-assembly of the on-surface fabricated acenes is greatly influenced by the on-surface reaction and strongly differs from the adsorption pattern of directly deposited acenes, highlighting the importance of the cleaved oxygen in the self-assembly.