Heteroatom‐Edged [4]Triangulene: Facile Synthesis and Two‐Dimensional On‐Surface Self‐Assemblies**.

Triangulenes have attracted enormous interest in organic chemistry and materials science, but suffer from their high instability towards oxygen. Embedding heteroatoms into triangulenes provides a new class of ambient stable materials for various applications. However, [3]heterotriangulenes have dominated the chemistry of heteroatom‐doped triangulenes, while their higher homologues have been rarely explored. In this work, we synthesize a new [4]heterotriangulene with three oxygen‐boron‐oxygen (OBO) segments incorporated into the zigzag edges. The planar geometry of the OBO‐doped [4]triangulene is demonstrated by single‐crystal X‐ray diffraction. Self‐assembly on metal surfaces reveals substrate‐dependent nanostructures, leading to different long‐range ordered 2D patterns on Ag and Cu substrates with negligible defects. [ABSTRACT FROM AUTHOR]