On-surface Ullmann polymerization <i>via</i> intermediate organometallic networks on Ag(111)

Eichhorn, Johanna; Strunskus, Thomas; Rastgoo‐Lahrood, Atena; Samanta, Debabrata; Schmittel, Michael; Lackinger, Markus

doi:10.1039/c4cc02757d

Cited by 165 publications

(206 citation statements)

References 16 publications

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“…However, it is well established that a temperature of 425 K is high enough to induce the dehalogenation of the bromine atoms in organic molecules when deposited on Ag(111), due to the catalytic activity of the metallic surface. 28 Thus, the most plausible explanation is that a silver adatombased organometallic self-assembled superstructure has been formed, as reported earlier for the case of dimethylmethylene-bridged triphenylamine (DTPA) on Ag(111). 29 Regarding the number of monomers per flower-like structure, a coexistence of pentamers, hexamers, heptamers, and higher order rings is observed.…”

Section: Resultsmentioning

confidence: 84%

On-Surface Synthesis of BN-Substituted Heteroaromatic Networks

et al. 2015

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We report on the bottom-up fabrication of BN-substituted heteroaromatic networks achieved by surface-assisted polymerization and subsequent cyclodehydrogenation of specifically designed BN-substituted precursor monomers based on a borazine core structural element. To get insight into the cyclodehydrogenation pathway and the influence of molecular flexibility on network quality, two closely related precursor monomers with different degrees of internal cyclodehydrogenation have been employed. Scanning tunneling microscopy shows that, for both monomers, surface-assisted cyclodehydrogenation allows for complete monomer cyclization and the formation of covalently interlinked BN-substituted polyaromatic hydrocarbon networks on the Ag(111) surface. In agreement with experimental observations, density functional theory calculations reveal a significantly lower energy barrier for the cyclodehydrogenation of the conformationally more rigid precursor monomer, which is also reflected in a higher degree of long-range order of the obtained heteroaromatic network. Our proof-of-concept study will allow for the fabrication of atomically precise substitution patterns within BNC heterostructures.

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Section: Resultsmentioning

confidence: 84%

On-Surface Synthesis of BN-Substituted Heteroaromatic Networks

et al. 2015

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“…[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.…”

Section: Dehalogenationmentioning

confidence: 99%

On‐Surface Synthesis of Atomically Precise Graphene Nanoribbons

2016

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The surface-assisted polymerization and cyclodehydrogenation of specifically designed organic precursors provides a route toward atomically precise graphene nanoribbons, which promises to combine the outstanding electronic properties of graphene with a bandgap that is sufficiently large for room-temperature digital-logic applications. Starting from the basic concepts behind the on-surface synthesis approach, this report covers the progress made in understanding the different reaction steps, in synthesizing atomically precise graphene nanoribbons of various widths and edge structures, and in characterizing their properties, ending with an outlook on the challenges that still lie ahead.

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“…Particularly, Ullmann-type reactions were successfully utilized for the synthesis of 1D 28-31 and 2D 28,30,[32][33][34][35][36][37][38][39] polymer nanostructures from suitable precursor molecules on noble metal surfaces.…”

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confidence: 99%

From Graphene Nanoribbons on Cu(111) to Nanographene on Cu(110): Critical Role of Substrate Structure in the Bottom-Up Fabrication Strategy

et al. 2015

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Bottom-up strategies can be effectively implemented for the fabrication of atomically precise graphene nanoribbons. Recently, using 10,10'-dibromo-9,9'-bianthracene (DBBA) as a molecular precursor to grow armchair nanoribbons on Au(111) and Cu(111), we have shown that substrate activity considerably affects the dynamics of ribbon formation, nonetheless without significant modifications in the growth mechanism. In this paper we compare the on-surface reaction pathways for DBBA molecules on Cu(111) and Cu(110). Evolution of both systems has been studied via a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and theoretical calculations. Experimental and theoretical results reveal a significant increase in reactivity for the open and anisotropic Cu(110) surface in comparison with the close-packed Cu(111). This increased reactivity results in a predominance of the molecular-substrate interaction over the intermolecular one, which has a critical impact on the transformations of DBBA on Cu(110). Unlike DBBA on Cu(111), the Ullmann coupling cannot be realized for DBBA/Cu(110) and the growth of nanoribbons via this mechanism is blocked. Instead, annealing of DBBA on Cu(110) at 250 °C results in the formation of a new structure: quasi-zero-dimensional flat nanographenes. Each nanographene unit has dehydrogenated zigzag edges bonded to the underlying Cu rows and oriented with the hydrogen-terminated armchair edge parallel to the [1-10] direction. Strong bonding of nanographene to the substrate manifests itself in a high adsorption energy of -12.7 eV and significant charge transfer of 3.46e from the copper surface. Nanographene units coordinated with bromine adatoms are able to arrange in highly regular arrays potentially suitable for nanotemplating.

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On-surface Ullmann polymerization via intermediate organometallic networks on Ag(111)

Cited by 165 publications

References 16 publications

On-Surface Synthesis of BN-Substituted Heteroaromatic Networks

On-Surface Synthesis of BN-Substituted Heteroaromatic Networks

On‐Surface Synthesis of Atomically Precise Graphene Nanoribbons

From Graphene Nanoribbons on Cu(111) to Nanographene on Cu(110): Critical Role of Substrate Structure in the Bottom-Up Fabrication Strategy

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