Critical Role of Phenyl Substitution and Catalytic Substrate in the Surface-Assisted Polymerization of Dibromobianthracene Derivatives

Abstract

Understanding the nature and hierarchy of on surface reactions is a major challenge for designing coordination and covalent nanostructures by means of multistep synthetic routes. In particular, intermediates and final products are hard to predict since reaction paths and their activation windows depend on the choice of both the molecular precursor design and the substrate. Here we report a systematic study of the effect of the catalytic metal surface to reveal how a single precursor can give rise to very distinct polymers that range from coordination and covalent non planar 1 arXiv:1809.07289v1 [cond-mat.mtrl-sci] 19 Sep 2018 polymer chains of distinct chirality, to atomically precise graphene nanoribbons and nanoporous graphene. Our precursor consists on adding two phenyl substituents to 10,10-dibromo 9,9-bianthracene, a well-studied precursor in the on-surface synthesis of graphene nanoribbons. The critical role of the monomer design on the reaction paths is inferred from the fact that the phenyl substitution leads to very distinct products in each one of the studied metallic substrates.

Stabilizing Edge Fluorination in Graphene Nanoribbons

“…The doublet downshift by 2.1 eV upon annealing at 200°C can be assigned to C-Br cleavage and consequent formation of Au-bonded Br adsorbates. [18][19][20] The completion of the C-Br cleavage is in agreement with the Ullmann polymerization observed by STM at the same temperature (Figure 3). At higher temperature, Br adatoms desorb from the surface, as indicated by the absence of any Br 3d peak A deeper insight into the conformation of the cove regions that surround the functionalized benzene indicates that they cannot withhold a coplanar structure due to the steric repulsion between the hydrogens of adjacent rings.…”

Modified Engineering of Graphene Nanoribbons Prepared via On‐Surface Synthesis

“…g–j) Br 3d core‐level spectra of different stages on Au(111) (g), Ag(111) (h), Cu(111) (i), and Ag (100) (j). g–j) Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…The “armchair” chains on Ag(111) and the “zigzag” chains on Cu(111) can be clearly discerned. Recently, Moreno et al used the results of X‐ray photoelectron spectroscopy (XPS) to compare the respective reaction processes on a variety of substrates . The 3d core‐level spectra of Br suggested the different debromination behaviors on Au(111), Ag(111), Ag (100), and Cu(111) substrates (Figure g–j).…”

“…The polyanthracene chains can be transformed from organometallic intermediate chains, which can finally result in GNRs. The dehalogenation temperature on Ag(111) is moderate than on Au(111) and Cu(111) . Thus, it is useful to detect and study the intermediate reaction stage of GNR formation.…”

Surface specificity and mechanistic pathway of de-fluorination of C60F48 on coinage metals

“…Understanding the mechanistic aspects of fundamental processes that take place between organic molecules and metal surfaces is a challenging topic with important implications in many interdisciplinary elds of nanoscience. Examples include on-surface synthesis [1][2][3][4][5] (which allows one to obtain novel nanostructures difficult to obtain by solution chemistry methods), supramolecular organization and self-assembly 6 (as a key bottom-up fabrication method with the lowest energy consumption) and charge transfer between molecules and metals 7,8 (essential for charge injection/extraction in organic electronic devices, such as organic solar cells or eld effect transistors). These processes depend on a delicate balance between inter and intramolecular interactions and moleculesurface interactions which are highly system-dependent.…”