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Toward Cove-Edged Low Band Gap Graphene Nanoribbons

2015; American Chemical Society; Volume: 137; Issue: 18 Linguagem: Inglês

10.1021/jacs.5b03017

1943-2984

Junzhi Liu, Bowei Li, Yuan‐Zhi Tan, Angelos Giannakopoulos, Carlos Sánchez‐Sánchez, David Beljonne, Pascal Ruffieux, Román Fasel, Xinliang Feng, Kläus Müllen,

Molecular Junctions and Nanostructures

Graphene nanoribbons (GNRs), defined as nanometer-wide strips of graphene, have attracted increasing attention as promising candidates for next-generation semiconductors. Here, we demonstrate a bottom-up strategy toward novel low band gap GNRs (Eg = 1.70 eV) with a well-defined cove-type periphery both in solution and on a solid substrate surface with chrysene as the key monomer. Corresponding cyclized chrysene-based oligomers consisting of the dimer and tetramer are obtained via an Ullmann coupling followed by oxidative intramolecular cyclodehydrogenation in solution, and much higher GNR homologues via on-surface synthesis. These oligomers adopt nonplanar structures due to the steric repulsion between the two C-H bonds at the inner cove position. Characterizations by single crystal X-ray analysis, UV-vis absorption spectroscopy, NMR spectroscopy, and scanning tunneling microscopy (STM) are described. The interpretation is assisted by density functional theory (DFT) calculations.