Diboraperylene Diborinic Acid Self-Assembly on Ag(111)-Kagome Flat Band Localized States Imaged by Scanning Tunneling Microscopy and Spectroscopy

Replacement of sp2-hybridized carbon in polycyclic aromatic hydrocarbons (PAHs) by boron affords electron-deficient pi-scaffolds due to the vacant pz-orbital of three-coordinate boron with the potential for pronounced electronic interactions with electron-rich metal surfaces. Using a diboraperylene diborinic acid derivative as precursor and a controlled on-surface non-covalent synthesis approach, we report on a self-assembled chiral supramolecular kagome network on an Ag(111) surface stabilized by intermolecular hydrogen-bonding interactions at low temperature. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal a flat band at ca. 0.33 eV above the Fermi level which is localized at the molecule center, in good agreement with tight-binding model calculations of flat bands characteristic for kagome lattices. A planar diboraperylene diborinic acid B2-Per self-assembles into a chiral kagome supramolecular network on an Ag(111) substrate and is stabilized by hydrogen bonding between BOH subunits of adjacent molecules. The kagome supramolecular network exhibits a dispersionless flat band at ca. 0.33 eV above the Fermi level, which is observed by scanning tunneling microscopy/spectroscopy and further proved by tight-binding model calculations. image