On surface chemistry beyond Ullmann coupling: the case of aminophenol
On-surface chemistry has become an efficient strategy for the synthesis of nanomaterials exhibiting different dimensionalities. The main used methodology is the Ullmann coupling, i.e., the cleavage of an aryl-halide bond catalyzed by a metal atom to lead to aryl coupling. However, this methodology presents several drawbacks and nowadays there is increasing interest to set-up different strategies.
We have addressed this topic by complementary examples of thermally induced dehydrogenation reactions [1], including the oxidation of alcohol groups to quinone forms. Particularly, we aim at understanding the basic mechanisms, and we have studied a simple molecule: aminophenol. This molecule includes two functional groups: amino and alcohol, and we study their oxidation on a metal surface and the intermolecular coupling reactions leading to complex structures depending on the nature (Cu and Pt) and symmetry (<110> and <111> terminations) of the surface [2,3].
Finally, we present a novel approach for the activation and subsequent covalent coupling of unfunctionalized polycyclic aromatic hydrocarbons (PAHs) which does not significantly depend on the nature of the surface[4]. This strategy is based on the rupture of the local aromaticity of the molecule induced by the sp2 to sp3 hybridization transition taking place upon superhydrogenation of the molecules when exposed to atomic hydrogen.
References
[1]/ A.L. Pinardi et al. Tailored formation of N-doped nanoarchitectures by diffusion-controlled on-surface (cyclo) dehydrogenation of heteroaromatics. ACS nano 2013, 7, 3676
[2]/ Nerea Ruiz del Árbol et al. "On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior." Angewandte Chemie, 2018, 130, 28
[3]/ Nerea Ruiz del Árbol et al. , On‐Surface Driven Formal Michael Addition Produces m‐Polyaniline Oligomers on Pt(111) Angew. Chem. 2020, 132, 2
[4]/ Carlos Sánchez-Sánchez et al. J. Am. Chem. Soc., 141 (2019) 3550-3557