Synthesis of distorted nanographenes containing seven- and eight-membered carbocycles

Abstract

This feature article focuses on the bottom-up approaches (solution-phase) based on organic synthesis for the preparation of saddle-shaped distorted polycyclic aromatic hydrocarbons (PAHs). We summarise the recent progress on the synthetic strategies followed to obtain well-defined nanographenes containing heptagonal and octagonal carbocycles, highlighting the novel strategy developed by our group together with our recent contributions in the area of distorted aromatics. The presence of seven- or eight-membered rings induces a saddle-shape curvature in the planar network pushing the structure out of the plane, which influences the physical properties exhibited. Some brief details on the optical and electronic properties of these curved nanostructures are also discussed.

Contorted Polycyclic Aromatic Hydrocarbons with Two Embedded Azulene Units

“…Based on our research on diarenoperylenes, we recently found that Scholl‐type oxidations of 1 a and 1 b with both FeCl 3 in nitromethane as well as with DDQ and trifluoromethanesulfonic acid gave five‐membered ring‐cyclized products 2 a and 2 b exclusively . We envisioned combining this highly selective Scholl‐type reaction in a manner that would generate an additional seven‐membered ring (Scheme ), preferably in the same step, resulting in azulene formation during Scholl‐cyclization, something that has previously only been observed on Au(111) surfaces …”

Contorted Polycyclic Aromatic Hydrocarbons with Two Embedded Azulene Units

“…To the best of our knowledge,t his represents the largest PA Hc ontaining at least two formal azulene units.B ased on our research on diarenoperylenes, [19] we recently found that Scholl-type oxidations of 1a and 1b with both FeCl 3 in nitromethane as well as with DDQ and trifluoromethanesulfonic acid gave five-membered ringcyclized products 2a and 2b exclusively. [20,21] We envisioned combining this highly selective Scholl-type reaction in amanner that would generate an additional seven-membered ring (Scheme 1), [22] preferably in the same step,r esulting in azulene formation during Scholl-cyclization, something that has previously only been observed on Au(111) surfaces. [16a] Accordingly,w es ynthesized the bisnaphthyl diareno precursor 3 from the corresponding bromide 6 [19b] by Suzuki-Miyaura cross-coupling in 67 %y ield (Scheme 2).…”

Polycyclic Aromatic Hydrocarbons as Potential Building Blocks for Organic Solar Cells

“…PAHs with odd‐membered rings, especially those possessing 5‐ or 7‐membered rings, are getting more and more popular due to the properties that arise from this structural change . For example, the introduction of odd‐membered rings in a six‐membered rings scaffold can induce a significant curvature to the PAH, allowing the synthesis of elegant yet useful molecules .…”