Phenylenediamine-Linked, Folded Nanographene Dimers: Access to Structure-Dependent Redox Capability

Polycyclic aromatic hydrocarbons (PAHs) with open-shell or redox characteristics are highly desirable due to their intriguing electronic properties and potential applications. Here, we demonstrate a series of phenylenediamine-linked nanographenes (NGs) <b>1</b>-<b>3</b> by connecting two aza-hexa-<i>peri</i>-hexabenzocoronene (HBC) units to <i>p</i>-phenylene, <i>p</i>,<i>p</i>'-biphenylene, and <i>p</i>,<i>p</i>"-terphenylene, respectively, and unveil their 3D conformations, electronic structures, and redox properties. As proved by X-ray crystallographic analysis and quantum chemical calculation, <b>1</b>-<b>3</b> adopted anti-folded, Z-shaped 3D structures with rotatable single bonds. The structure-dependent redox capabilities were disclosed. For <b>1</b>, a stable monoradical cation was generated by one-electron oxidation as the terminal product. X-ray crystallographic analysis revealed an unprecedented <i>syn</i>-folded structure of monoradical 1⁺. However, <b>2</b> and <b>3</b> were demonstrated as redox-active molecules from neutral to dication that each oxidative state can be precisely controlled by chemical oxidation/reduction.