RETRACTED ARTICLE: Living annulative π-extension polymerization for graphene nanoribbon synthesis

The properties of graphene nanoribbons (GNRs)1–5—such as conductivity or semiconductivity, charge mobility and on/off ratio—depend greatly on their width, length and edge structure. Existing bottom–up methods used to synthesize GNRs cannot achieve control over all three of these parameters simultaneously, and length control is particularly challenging because of the nature of step-growth polymerization6–18. Here we describe a living annulative π-extension (APEX)19 polymerization technique that enables rapid and modular synthesis of GNRs, as well as control over their width, edge structure and length. In the presence of palladium/silver salts, o-chloranil and an initiator (phenanthrene or diphenylacetylene), the benzonaphthosilole monomer polymerizes in an annulative manner to furnish fjord-type GNRs. The length of these GNRs can be controlled by simply changing the initiator-to-monomer ratio, achieving the synthesis of GNR block copolymers. This method represents a type of direct C–H arylation polymerization20 and ladder polymerization21, activating two C–H bonds of polycyclic aromatic hydrocarbons and constructing one fused aromatic ring per chain propagation step.