[19]Starphene: Combined In-Solution and On-Surface Synthesis Towards the Largest Starphene

Abstract

Starphenes are structurally appealing three-fold symmetric polycyclic aromatic compounds withpotential interesting applications in molecular elec-tronics and nanotechnology. This family of star-shapedpolyarenes can be regarded as three acenes that areconnected through a single benzene ring. In fact, justlike acenes, unsubstituted large starphenes are poorlysoluble and highly reactive molecules under ambientconditions making their synthesis difficult to achieve.Herein, we report two different synthetic strategies toobtain a starphene formed by 19 cata-fused benzenerings distributed within three hexacene branches. Thismolecule, which is the largest starphene that has beenobtained to date, was prepared by combining solution-phase and on-surface synthesis. [19]Starphene wascharacterized by high-resolution scanning tunnelingmicroscopy (STM) and spectroscopy (STS) showing aremarkable small HOMO-LUMO transport gap(0.9 eV).