Long rylene nanoribbons express polyacetylene-like signatures at their edges

Oligorylenes have been the focus of research during the journey toward intrinsically conducting polyrylene. Recently, the description of diradicaloid and tetraradicaloid properties in long oligorylene molecules has revived the old question about their electronic structures which is of current interest in the context of the properties of graphene nanoribbons. Here we show that the armchair edges of smaller oligorylenes are embedded within aromatic units and they transform into armchair cis-polyacetylenic structures for octarylene and longer. Concomitantly, the short zig-zag edges of oligorylenes stabilize diradicaloid and multiradical states. This electronic transformation is proved experimentally by Raman spectroscopy and supported by theoretical modelling.