Competing on-surface reaction pathways of bifunctional anthracene precursors to obtain organometallic networks

On surface synthesis is a versatile bottom up fabrication approach to create covalent nanostructures with atomic precision. Several organic covalent structures have been created by this approach, such as graphene based structures or organometallic networks. Aiming at the synthesis of a porous network, we study the hierarchy of chemical reactions of 10-bromoanthracene-9-yl-boronic-acid (BABA) precursors that are vapour sublimated onto crystalline surfaces under ultra-high-vacuum conditions. Our scanning tunnelling microscopy and spectroscopy characterization unveils that BABA dehydration to produce boroxine rings and metal substitution of the halogen group take place simultaneously leading to the formation of an organometallic honeycomb network, similarly to the case of using a simple phenyl core instead of anthracene [1]. In our case, however, the competition between these two reactions is extremely dependent on the catalytic role of the substrate, its surface termination and its temperature during the deposition of the precursor. As a consequence, the reaction pathway can be readily controlled by the choice of the catalytic surface (Ag(001), Ag(111) or Ag(111)).

1. J. Phys. Chem. C 2012, 116, 7, 4819