Formation of Azulene‐Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction

Abstract

Incorporation of anon-hexagonal ring into ananographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene-bridged double [6]helicene and heptagon-containing nanographene by the Scholl reaction, an unexpected azulene-embedded nanographene and its triflyloxylated product were obtained, as confirmed by X-rayc rystallographic analysis and 2D NMR spectroscopy. A5/7/7/5 ring-fused substructure containing two formal azulene units is formed, but only one of them shows an azulene-like electronic structure.The formation of this unique structure is explained by arenium ion mediated 1,2-phenyl migration and an aphthalene to azulene rearrangement reaction according to an in-silico study.This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene-based molecular materials.

Formation of Azulene‐Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction

“…Single crystals of 1b suitable for X-ray analysis were obtained by slow diffusion of methanol into atetrahydrofuran solution of 1b. [14] Interestingly,a nu nusual 5/7/7/5 ring-fused substructure was observed in the middle,and one of the tertbutyl group was replaced by at riflate group (Figure 1a).…”

Multi‐Redox Active Carbons and Hydrocarbons: Control of their Redox Properties and Potential Applications

“…To date, various multi‐redox active C x H y molecules have been explored. These include, but are not limited to, nanographenes, [16–24] radicaloids (mostly based on diindenoarenes), [25–34] macrocycles, [35–39] fullerene fragments (including buckybowls), [40–45] nanographene‐buckybowl hybrids, [46] pentalene derivatives, [47] ethynylenes, [48] spiro‐compounds, [14] cumulenes, [49] other C x H y molecules with either the azulene, [50] barrelene, [51] fluoranthene, [52] fluorene, [53] diphenalene, [54] phenylene, [55] or Schwarzite framework, [56] and hydrofullerenes [57–61] . The redox properties of dissolved C x H y molecules are summarized in Table 1, where C x H y molecules that show at least six redox reactions (Scheme 1) are listed.…”

“…For instance, Han et al. reported an azulene‐embedded nanographene 127 , which showed two redox couples and one irreversible oxidative process [16] . Ma et al.…”

Edge‐Functionalized Nanographenes

“…Recently,v arious uniquec arbon frameworks have been reported. [20][21][22][23][24][25][26][27][28][29] Of particular interesti st he incorporation of non-six-membered rings into carbon frameworks. [22] These rings can cause negative and positive curvatures in the frameworks, resultingi nn onplanar NGs that are difficult to obtain by top-down methods and bottom-up methods utilizing carbonization.…”

“…In contrast to the former two methods, this method allows the construction of structurally well‐defined carbon frameworks. Recently, various unique carbon frameworks have been reported [20–29] . Of particular interest is the incorporation of non‐six‐membered rings into carbon frameworks [22] .…”