On-Surface Synthesis with Atomic Hydrogen

Abstract

Surface-assisted synthesis has become a powerful approach for generation of molecular nanostructures, which could not be obtained via traditional solution chemistry. Nowadays there is an intensive search for reactions that could proceed on flat surfaces in order to boost the versatility and applicability of synthesized nano-objects. Here we propose application of atomic hydrogen combined with on-surface synthesis in order to tune the reaction pathways. We demonstrate that atomic hydrogen could be widely applied: (1) as a cleaning tool, which allows removal of halogen residues from the surface after Ullmann couplings/polymerization, (2) by reaction with surface organometallics to provide stable hydrogenated species, and (3) as a reagent for debromination or desulfurization of adsorbed species.

On-Surface Synthesis of Chlorinated Narrow Graphene Nanoribbon Organometallic Hybrids

“…The dotted structures surrounding the islands with chlorinated 5-AGNROHs are formed by Br, which gathers on the surface after C–Br bond cleavage and precursor activation, similarly as it was recently reported by Zuzak et al 30 and Sun et al 32 We emphasize at this point that the GNROHs are formed at temperature below 200 °C, which is lower than the desorption temperature of bromine atoms. 31 , 56 This results in the clearly discernible appearance of Br on the surface as the reaction byproduct.…”

“…Alternatively, bromine atoms may be removed from the surface either by deposition of silicon atoms 32 or by atomic hydrogen dosing, 30 , 63 the application of which has recently been introduced in on-surface synthesis approach for intermolecular fusion. 64 It is likely that application of atomic hydrogen shall be much more efficient in removing residual halogen atoms; 30 however, it may also modify the generated gold complexes. Indeed, in the following we show that the application of atomic hydrogen to GNROHs leads to organometallic state quenching and passivation of the carbon skeleton providing perfect 5-AGNRs.…”

On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

“…Furthermore, in agreement with previous results using atomic [21] and molecular hydrogen, [47] the formation of shorter GNR s can be enforced by performing the Ullmann coupling step in D 2 gas (Figure S8). The use of deuterium allows tracking the hydrogen passivation of GNR s: deactivation at both ends of the GNR would ideally result in GNR oligomers containing exactly two D atoms.…”

“…[11][12][13] Although atomic hydrogen on coinage metal surfaces desorbs already below room temperature by recombination to H 2 , [14,15] it can induce reactions such as desorption of Br as HBr, [11,13,16] undesired passivation of the active sites in on-surface polymerization, [16,17] cleavage of cyano groups as HCN, [18] conversion of surface copper oxide to water [19] or CÀC bond cleavage and hydrogenation. [20] Externally produced atomic hydrogen has been used to selectively deactivate active sites in on-surface polymerization chemistry, [21] to deliberately clean-up Br, [21,22] and to induce C À C coupling. [23] Despite the nobleness of gold, [24] its surface has the ability to dissociate H 2 , most likely at undercoordinated Au atoms.…”

On‐Surface Hydrogen/Deuterium Isotope Exchange in Polycyclic Aromatic Hydrocarbons

“…Although atomic hydrogen on coinage metal surfaces desorbs already below room temperature by recombination to H 2 , [14, 15] it can induce reactions such as desorption of Br as HBr, [11, 13, 16] undesired passivation of the active sites in on‐surface polymerization, [16, 17] cleavage of cyano groups as HCN, [18] conversion of surface copper oxide to water [19] or C−C bond cleavage and hydrogenation [20] . Externally produced atomic hydrogen has been used to selectively deactivate active sites in on‐surface polymerization chemistry, [21] to deliberately clean‐up Br, [21, 22] and to induce C−C coupling [23] …”