On-surface synthesis of nitrogen-doped nanographenes with 5–7 membered rings

Abstract

We report on the formation of nitrogen-doped nanographenes containing five-and seven-membered rings by thermally induced cyclodehydrogenation on the Au(111) surface. Using scanning tunneling microscopy and supported by calculations, we investigated the structure of precursor and targets, as well as of intermediates. Scanning tunneling spectroscopy shows that the electronic properties of the target nanographenes are strongly influenced by the additional formation of non-hexagonal rings.

On‐Surface Synthesis of a Dicationic Diazahexabenzocoronene Derivative on the Au(111) Surface

“…[14] Over the last years,s everal NGs have been achieved through surface-catalyzed oxidative cyclodehydrogenation of the molecular precursors. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] Only recently,t he graphenebased chemical toolbox has been extended to the on-surface synthesis of heteroatom-doped NGs.C ontrolled substitutional doping is an efficient approach to tune the electronic, magnetic and physicochemical properties of graphene-based materials.I np articular,n itrogen doping (see Figure 1f or nitrogen-doped NGs (I-V)s ynthetized on surfaces) [15][16][17][18][19] offers an accessible doping process and an efficient modulation of the structure and properties of carbon-based nanostructures,w hile preserving its high electrical conductivity and potential in optical, electronic and catalytic applica-tions, [34][35][36][37] taking simultaneously advance from the modified electrical properties and surface reactivity of N-doped sites. Among the different types of nitrogen dopants,the introduction of graphitic nitrogen in the hexagonal lattice of aN G, where Na toms substitute quaternary Ca toms,m ay lead to ac ationic charge state,w hich confers them interesting catalytic activity.…”

Construction of Heptagon‐Containing Molecular Nanocarbons

“…[63] PA H 146 is anon-benzenoid non-alternant structural isomer of peri-tetracene with two embedded azulene units.S pin-polarized DFT calculations revealed that both 146 and 149 should exhibit open-shell singlet ground states,a nd 149 showed an arrow band gap (0.27 eV) and significant open-shell biradical character (y 0 = 0.92), making them promising candidates for spintronic applications.I n 2019, Moresco and co-workers used as imilar technique for the surface-assisted cyclodehydrogenation of 150,resulting in the formation of N-doped PA H 151 containing two azulene units (Scheme 40 c). [125] Once again, the incorporation of nonhexagonal rings was seen to have as trong effect on the electronic properties of 151,which showed anarrower energy gap and reduced planarity relative to precursor 150.…”

Construction of Heptagon‐Containing Molecular Nanocarbons

“…In 2019, Moresco and co‐workers used a similar technique for the surface‐assisted cyclodehydrogenation of 150 , resulting in the formation of N‐doped PAH 151 containing two azulene units (Scheme 40 c). [125] Once again, the incorporation of non‐hexagonal rings was seen to have a strong effect on the electronic properties of 151 , which showed a narrower energy gap and reduced planarity relative to precursor 150 .…”