Schematic illustration of proposed reaction pathways during synthesis of seven-atom-wide armchair graphene nanoribbons (7-aGNRs). (a) Deuterated molecular monomer 10,10’-dibromo-9,9’-bianthracene-1,1’,4,4’,5,5’,8,8’-d8 at selected positions was used to differentiate between three possible mechanisms. (b) Deuterated polyanthrylene polymer obtained after Ullmann coupling. (c)-(e) Predicted structures of 7-aGNRs via different reaction pathways that can be compared with experiment. In (a) and (b), tilting anthrylene units are indicated by different bond thicknesses and color gradient. In (b)-(e), unit cells in polyanthrylene and deuterated 7-aGNRs are indicated by different colors. Only D atoms are shown while H atoms are omitted for clarity.
Scientific Achievement
Selective deuterations were exploited to synthesize graphene nanoribbons (GNRs) on Au(111) surface with a specific H/D pattern on the edges, allowing for determination of the exact pathway of the cyclodehydrogenation reaction.
Significance and Impact
This work clarifies the on-surface cyclodehydrogenation process within the framework of pericyclic reactions to pave a way for realizing p-extended graphitic scaffolds with designed structures having desirable functions.
Research Details
- Atomically precise GNRs were synthesized on Au(111) surface using selectively deuterated molecular precursors.
- Specific H/D patterns on GNRs were characterized with scanning tunneling microscopy, Raman spectroscopy, and DFT calculations.
Reaction pathways determined by in situ mass spectroscopy and CI-NEB calculations of energy profiles.
C. Ma, Z. Xiao, P. V. Bonnesen, L. Liang, A. A. Puretzky, J. Huang, M. Kolmer, B. G. Sumpter, W. Lu, K. Hong, J. Bernholc, A.-P. Li. Chemical Science, 12 15637 (2021). DOI: 10.1039/D1SC04908A
