Helically Coiled Graphene Nanoribbons

Graphene is a zero‐gap, semiconducting 2D material that exhibits outstanding charge‐transport properties. One way to open a band gap and make graphene useful as a semiconducting material is to confine the electron delocalization in one dimension through the preparation of graphene nanoribbons (GNR). Although several methods have been reported so far, solution‐phase, bottom‐up synthesis is the most promising in terms of structural precision and large‐scale production. Herein, we report the synthesis of a well‐defined, helically coiled GNR from a polychlorinated poly( m ‐phenylene) through a regioselective photochemical cyclodehydrochlorination (CDHC) reaction. The structure of the helical GNR was confirmed by 1 H NMR, FT‐IR, XPS, TEM, and Raman spectroscopy. This Riemann surface‐like GNR has a band gap of 2.15 eV and is highly emissive in the visible region, both in solution and the solid state.