Abstract
Coronoids, polycyclic aromatic hydrocarbons with geometrically defined cavities, are promising model structures of porous graphene. Here, we report the on-surface synthesis of C168 and C140 coronoids, referred to as [6]- and [5]coronoid, respectively, using 5,9-dibromo-14-phenylbenzo[m]tetraphene as the precursor. These coronoids entail large cavities (>1 nm) with inner zigzag edges, distinct from their outer armchair edges. While [6]coronoid is planar, [5]coronoid is not. Low-temperature scanning tunneling microscopy/spectroscopy and noncontact atomic force microscopy unveil structural and electronic properties in accordance with those obtained from density functional theory calculations. Detailed analysis of ring current effects identifies the rings with the highest aromaticity of these coronoids, whose pattern matches their Clar structure. The pores of the obtained coronoids offer intriguing possibilities of further functionalization toward advanced host–guest applications.
Highlights
Coronoids, polycyclic aromatic hydrocarbons with geometrically defined cavities, are promising model structures of porous graphene
Coronoids are macrocyclic conjugated hydrocarbons formed by circularly fused benzenoid rings, featuring a cavity.1−3 Kekulene is a representative coronoid with a single layer of benzene rings around the cavity, belonging to the family of cycloarenes
In 2016, we reported a C216 coronoid,1 a macrocyclic molecule with 216 sp2 carbon atoms distributed in more than one layer of circularly fused benzene rings (Figure 1)
Summary
Polycyclic aromatic hydrocarbons with geometrically defined cavities, are promising model structures of porous graphene. Other examples of cycloarenes are cyclo[d,e,d,e,e,d,e,d,e,e]decakisbenzene,5 predicted to have intriguing electronic and magnetic properties,6−9 septulene,10 and octulene.11 In 2016, we reported a C216 coronoid,1 a macrocyclic molecule with 216 sp2 carbon atoms distributed in more than one layer of circularly fused benzene rings (Figure 1).
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