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.