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

Abstract

The atomically precise control over the size,s hape and structure of nanographenes (NGs) or the introduction of heteroatom dopants into their sp 2 -carbon lattice confer them valuable electronic, optical and magnetic properties.H erein, we report on the design and synthesis of ahexabenzocoronene derivative embedded with graphitic nitrogen in its honeycomb lattice,a chieved via on-surface assisted cyclodehydrogenation on the Au(111) surface.C ombined scanning tunnelling microscopy/spectroscopya nd non-contact atomic force microscopyi nvestigations unveil the chemical and electronic structures of the obtained dicationic NG.K elvin probe force microscopym easurements reveal ac onsiderable variation of the local contact potential difference toward lower values with respect to the gold surface,indicative of its positive net charge. Altogether,w ei ntroduce the concept of cationic nitrogen doping of NGs on surfaces,opening new avenues for the design of novel carbon nanostructures.

Aza-Triangulene: On-Surface Synthesis and Electronic and Magnetic Properties

“…The charge transfer can be understood from the high work function of the Au(111) surface and the associated low binding energy of highest occupied molecular orbital (HOMO) levels of hydrocarbon structures atop, along with the n-doping effect of graphitic N-subsituents . Indeed, similar charge-transfer processes were observed in a number of N-doped molecules on Au(111). − In contrast, no charge transfer was detected in the previous works studying unsubstituted extended triangulenes on Au(111). , These findings agree with the lower ionization energy of aza-triangulene (5.0 eV, see Figure S9) as compared to those of unsubstituted triangulene and extended triangulenes (6.3 and 6.2 eV).…”

Phenanthrene-Extended Phenazine Dication: An Electrochromic Conformational Switch Presenting Dual Reactivity

“…While being challenging, the preparation of positively charged doped PAHs is potentially highly rewarding. In fact, this approach could result not only in semiconducting materials presenting charge transfer states but also in the introduction of highly polar bonds that are useful for self-assembly and sensing. − Moreover, the possibility of introducing the heteroatoms in a neutral state and oxidizing them in a later step can result in materials with a behavior depending on the oxidation state and in molecular switching capabilities due to hybridization change. , While various examples of PAHs presenting a single charged atom in their structure have been reported in different contributions, ,,,, doubly charged ones are less explored, with notable examples presenting O, N, S, or combinations of these heteroatoms, using both surface and solution-based chemistry. − From this point of view, parent and π-extended dihydrophenazines represent valuable precursors toward the generation of 2 + N-doped PAHs. These derivatives are known to be easily oxidized and have been synthesized by various groups, − leading to their use as emitters, redox-active materials, or organocatalysts. − Interestingly, while the radical cations of such derivatives have been extensively explored, ,,, the aromatic dicationic diamagnetic states have been widely neglected and studied almost exclusively in solution, , with some notable exceptions successfully isolating N-alkyl derivatives of the parent phenazinium dication, which, however, were reported as highly reactive (Figure ).…”

On‐Surface Synthesis of a Nitrogen‐Doped Graphene Nanoribbon with Multiple Substitutional Sites

“…Thus, the N atom is closer to the substrate than the C atom (Figure S7). [26,39] In order to investigate the effect of different doped sites on the electronic properties of the N-9-AGNR, we performed STS measurements. Figure 3a shows a BR-STM image of N-9-AGNR (CÀ C) containing a CÀ N bond.…”

“…Second, the electronegativity of the N atom is larger than the C atom. Thus, the N atom is closer to the substrate than the C atom (Figure S7) [26, 39] …”