Ullmann-type coupling of brominated tetrathienoanthracene on copper and silver

Abstract

We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C. On Cu(111) only organometallic structures are formed, while on Ag(111) both organometallic and covalent polymeric networks were found to coexist. The ratio between organometallic and covalent bonds could be controlled by means of the annealing temperature. The thiophene moieties start degrading at 200 °C on the copper surface, whereas on silver the degradation process becomes significant only at 400 °C. Our work reveals how the interplay of a specific surface type and temperature steers the formation of organometallic and polymeric networks and describes how these factors influence the structural integrity of two-dimensional organic networks.

On‐Surface Synthesis of Atomically Precise Graphene Nanoribbons

“…At room temperature, the carbon-iodine bond is already broken on the (111) surfaces of all three metals. [ 29 ] The carbon-bromine bond is reported to be cleaved on the Cu(111), Cu(110), and Ag(110) surfaces, [ 30 ] while it remains intact on Au(111) and Au(110). [30][31][32][33] The Ag(111) surface can be considered intermediate, since room temperature coincides with the onset of carbon-bromine bond scission.…”

“…[ 29 ] The carbon-bromine bond is reported to be cleaved on the Cu(111), Cu(110), and Ag(110) surfaces, [ 30 ] while it remains intact on Au(111) and Au(110). [30][31][32][33] The Ag(111) surface can be considered intermediate, since room temperature coincides with the onset of carbon-bromine bond scission. [ 30,34 ] After dehalogenation, the halogen byproducts remain adsorbed on the surface up to temperatures beyond 200 °C.…”

“…[ 30,34 ] After dehalogenation, the halogen byproducts remain adsorbed on the surface up to temperatures beyond 200 °C. [ 13,30,33,35 ] The next stage of the synthesis, the polymerization of radical intermediates, thus occurs in the presence of the halogen atoms and it remains to be clarifi ed whether the halogens play a signifi cant role in this process as well. In this respect, the synthesis of one-dimensional GNRs differs from the synthesis of two-dimensional covalent organic frameworks, where steric hindrance from halogen clusters trapped within the network is clearly detrimental to long-range order.…”

“…[30][31][32][33] The Ag(111) surface can be considered intermediate, since room temperature coincides with the onset of carbon-bromine bond scission. [ 30,34 ] After dehalogenation, the halogen byproducts remain adsorbed on the surface up to temperatures beyond 200 °C. [ 13,30,33,35 ] The next stage of the synthesis, the polymerization of radical intermediates, thus occurs in the presence of the halogen atoms and it remains to be clarifi ed whether the halogens play a signifi cant role in this process as well.…”

Thermodynamics of an Electrocyclic Ring-Closure Reaction on Au(111)

“…On-surface synthesis has become an increasingly popular strategy to induce chemical reactions, both by interconnecting molecules into covalent nanostructures [1][2][3][4][5][6][7][8][9][10][11] as well as inducing single-molecule reactions. [11][12][13][14] The reactions normally take place on metal surface under ultrahigh vacuum (UHV) conditions.…”