On-Surface Synthesis of Oxygen-Doped Analogues of Higher Acenes

Oxygen doped analogues of higher acenes have been synthesized on Au(111) through the combination of solution chemistry and on-surface synthesis. On the basis of combined bond-resolved scanning tunneling microscopy (BR-STM), scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations two isomers containing heptacene core with benzofuran moieties, i.e. heptaceno[2,3-b:11,12-b′]bis[1]benzofuran and heptaceno[2,1-b:11,10-b']bis[1]benzofuran) have been identified and their structural and electronic properties have been analyzed in detail. We demonstrate that, in contrast to non-substituted parent acenes, oxygen equipped molecules tend to form self-assembled structures driven by electrostatic interactions on Au(111). Furthermore, the detailed analysis of the electronic properties reveals the ability to fine tune the transport gap by changing the position of benzofuran moieties.