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On-surface cyclodehydrogenation reaction pathway determined by selective molecular deuterations.
- Source :
-
Chemical science [Chem Sci] 2021 Nov 16; Vol. 12 (47), pp. 15637-15644. Date of Electronic Publication: 2021 Nov 16 (Print Publication: 2021). - Publication Year :
- 2021
-
Abstract
- Understanding the reaction mechanisms of dehydrogenative C <subscript>aryl</subscript> -C <subscript>aryl</subscript> coupling is the key to directed formation of π-extended polycyclic aromatic hydrocarbons. Here we utilize isotopic labeling to identify the exact pathway of cyclodehydrogenation reaction in the on-surface synthesis of model atomically precise graphene nanoribbons (GNRs). Using selectively deuterated molecular precursors, we grow seven-atom-wide armchair GNRs on a Au(111) surface that display a specific hydrogen/deuterium (H/D) pattern with characteristic Raman modes. A distinct hydrogen shift across the fjord of C <subscript>aryl</subscript> -C <subscript>aryl</subscript> coupling is revealed by monitoring the ratios of gas-phase by-products of H <subscript>2</subscript> , HD, and D <subscript>2</subscript> with in situ mass spectrometry. The identified reaction pathway consists of a conrotatory electrocyclization and a distinct [1,9]-sigmatropic D shift followed by H/D eliminations, which is further substantiated by nudged elastic band simulations. Our results not only clarify the cyclodehydrogenation process in GNR synthesis but also present a rational strategy for designing on-surface reactions towards nanographene structures with precise hydrogen/deuterium isotope labeling patterns.<br />Competing Interests: There are no conflicts to declare.<br /> (This journal is © The Royal Society of Chemistry.)
Details
- Language :
- English
- ISSN :
- 2041-6520
- Volume :
- 12
- Issue :
- 47
- Database :
- MEDLINE
- Journal :
- Chemical science
- Publication Type :
- Academic Journal
- Accession number :
- 35003594
- Full Text :
- https://doi.org/10.1039/d1sc04908a