Hierarchy in the Halogen Activation During Surface-Promoted Ullmann Coupling

Néstor Merino-Díez, Alejandro Pérez Paz, Jingcheng Li, Manuel Vilas-Varela, James Lawrence, Mohammed S.G. Mohammed, Alejandro Berdonces-Layunta, Ana Barragán, Jose Ignacio Pascual, Jorge Lobo-Checa, Diego Peña, Dimas G. de Oteyza

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Within the collection of surface-supported reactions currently accessible for the production of extended molecular nanostructures under ultra-high vacuum, Ullmann coupling has been the most successful in the controlled formation of covalent single C−C bonds. Particularly advanced control of this synthetic tool has been obtained by means of hierarchical reactivity, commonly achieved by the use of different halogen atoms that consequently display distinct activation temperatures. Here we report on the site-selective reactivity of certain carbon-halogen bonds. We use precursor molecules halogenated with bromine atoms at two non-equivalent carbon atoms and found that the Ullmann coupling occurs on Au(111) with a remarkable predilection for one of the positions. Experimental evidence is provided by means of scanning tunneling microscopy and core level photoemission spectroscopy, and a rationalized understanding of the observed preference is obtained from density functional theory calculations.

Original languageEnglish
Pages (from-to)2305-2310
Number of pages6
Issue number18
Publication statusPublished - Sept 17 2019
Externally publishedYes


  • Ullmann coupling
  • density functional calculations
  • graphene nanoribbons
  • hierarchical synthesis
  • scanning probe microscopy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry


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