Bottom-up Synthesis of Nitrogen-Doped Porous Graphene Nanoribbons

Abstract

Although methods for a periodic perforation and heteroatom doping of graphene sheets have been developed, patterning closely spaced holes on the nanoscale in graphene nanoribbons is still a challenging task. In this work, nitrogen-doped porous graphene nanoribbons (N-GNRs) were synthesized on Ag(111) using a silver-assisted Ullmann polymerization of brominated tetrabenzophenazine. Insights into the hierarchical reaction pathways from single molecules toward the formation of one-dimensional organometallic complexes and N-GNRs are gained by a combination of scanning tunneling microscopy (STM), atomic force microscopy (AFM) with CO-tip, scanning tunneling spectroscopy (STS), and density functional theory (DFT).

On‐Surface Synthesis of Nitrogen‐Doped Kagome Graphene

“…[14,17,21] The gas-phase band structures along K-G-M-K directions are shown in Figure 4 for the fully twisted gas-phase geometry as well as for the flattened as adsorbed geometry. Besides their noticeable gaps due to the high nitrogen doping, [4] the bands closer to E F have a characteristic Dirac-like dispersion in both cases similar to the literature. [23] At the G-point, HOMO-1/HOMO-2 and LUMO + 1/LUMO + 2 bands are nearly degenerate (Table S1) while HOMO and LUMO states are well separated in energy.…”

“…The four peripheral bromine atoms are still attached to the backbone, which lies flat on the substrate according to DFT calculations ( Figure S4a). Compared to the surrounding carbon rings, [4,26] the PZQ moiety is identified by a darker and more elongated contrast as confirmed by AFM simulations ( Figure S4b This observation is typical of hierarchical Ullman polymerization which has been corroborated in previous works using X-ray photoelectron spectroscopy. [24,27,28] A final annealing to T 3 = 220 8C promotes only the N-KG 3 as observed by AFM (Figure 2 d), indicative of a complete polymerization reaction.…”

“…On-surface synthesis of nanographene [1][2][3][4] has nowadays reached a high degree of control over the atomic structure allowing the precise implementation of heteroatomic dopants, [5,6] pores [4,7] and topological defects into the carbon lattice. Such engineered systems already demonstrated the controlled emergence of semiconducting properties by lateral quantum confinement or doping, [4,7] the appearance of metallicity via embedded zero-mode superlattices in graphene nanoribbons (GNR), [8,9] as well as magnetism induced by topological frustration. [2,10] Apart from the realization of massless Dirac fermions with graphene, [11] tremendous efforts have recently been devoted to further tailor exotic quantum states using unusual lattice geometries.…”

Fjord-Edge Graphene Nanoribbons with Site-Specific Nitrogen Substitution

“…11,12,13,14,15 Early bottom-up syntheses have focused on GNRs with armchair 16,17,18,19 or zigzag 20 edges. More recently, intricate edge or interior configurations, such as chevron, 11,21,22,23 cove, 24,25,26 fjord 27 or holey, 28,29,30 have been obtained. These novel topologies significantly alter the electronic or magnetic properties of GNRs, as do atomically precise 31 substitutions of carbons with heteroatoms such as boron, 32,33 sulfur, 34,35 or nitrogen.…”

“…23,36,37,41,42,43,44 Gratifyingly, creative ways to synthesize GNRs bearing novel edge or backbone structures are thriving to this day. 29,30,45 Herein, we describe the synthesis of the first eight-atom wide, fjord-edge nitrogen-doped graphene nanoribbons 1a,b (fjordedge N2 [8]GNR; Figure 1). Fjord-edge N2 [8]GNRs 1a,b were obtained in a facile two-step conversion starting from dipyridyl diynes 3a,b.…”