Fjord-Edge Graphene Nanoribbons with Site-Specific Nitrogen Substitution

Abstract

The synthesis of graphene nanoribbons (GNRs) that contain site-specifically substituted backbone heteroatoms is one of the essential goals that must be achieved in order to control the electronic properties of these next generation organic materials. We have exploited our recently reported solid-state topochemical polymerization/cyclization-aromatization strategy to convert the simple 1,4-bis(3pyridyl)butadiynes 3a,b into the fjord-edge nitrogen-doped graphene nanoribbon structures 1a,b (fjord-edge N2[8]GNRs). Structural assignments are confirmed by CP/MAS 13 C NMR, Raman, and XPS spectroscopy. The fjord-edge N2[8]GNRs 1a,b are promising precursors for the novel backbone nitrogen-substituted N2[8]AGNRs 2a,b. Geometry and band calculations on N2[8]AGNR 2c indicate that this class of nanoribbons should have unusual bonding topologies and metallicities.

Synthesis of Nonplanar Graphene Nanoribbon with Fjord Edges

“… 23 Very recently, Rubin and co-workers reported the synthesis of a nitrogen-doped fjord-edged GNR via solid-state topochemical polymerization, although its nonplanarity was not discussed and the resulting GNRs seemed to have only limited solubility. 24 Thus, the development of highly twisted fjord-edged GNRs in solution has remained elusive.…”

“…Likewise, an optical energy gap of 1.99 eV is estimated for FGNR, which is in line with the calculated result (1.93 eV) and comparable to the value reported for a fjordedge nitrogen-doped GNR (2.04 eV). 24 Photoluminescence spectra of 1, 2, and FGNR display a red shift of the emission maxima following the extension of the π-conjugation. In particular, broad emission covering 550−850 nm is found for FGNR, which could potentially be interesting for optoelectronic device applications.…”

“…On the other hand, Liu, Mai, and colleagues demonstrated a solution synthesis of the first example of long curved GNRs featuring a combination of cove, zigzag, and armchair edges . Very recently, Rubin and co-workers reported the synthesis of a nitrogen-doped fjord-edged GNR via solid-state topochemical polymerization, although its nonplanarity was not discussed and the resulting GNRs seemed to have only limited solubility . Thus, the development of highly twisted fjord-edged GNRs in solution has remained elusive.…”

Band structure modulation by methoxy-functionalization of graphene nanoribbons

“…[42][43][44][45] Through edge functionalization with electron-donating or -withdrawing groups, it becomes possible to modulate the electronic properties of GNRs, including the position of energy levels and bandgap. 42,43,[46][47][48][49] Moreover, the planarity of GNRs can also be altered by inducing steric repulsion. To this end, we have recently synthesized planar and non-planar GNRs with the identical aromatic core structure by installing alkyl chains at different peripheral positions, causing steric congestion with neighboring aromatic protons.…”

Novel Synthetic Approach to Heteroatom Doped Polycyclic Aromatic Hydrocarbons: Optimizing the Bottom-Up Approach to Atomically Precise Doped Nanographenes

“…The controlled polymerization of crystals (topochemical polymerization) [ 55 , 56 ] of 1,4-bis(3-pyridyl)-butadiynes afforded polydiacetylenes whose thermal treatment afforded specific N -doped graphene nanoribbons in which the nitrogen atoms are precisely located in the fjord-edge position ( Scheme 10 ) [ 57 ]. Such precise control of the polymerization reaction originates from the structure of crystals of compound 41 , in which the desired distance between the reactive carbon atoms of the triple bonds of adjacent molecules is obtained (3.45 Å).…”