Saddle-shaped aza-nanographene with multiple odd-membered rings
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d2sc05858h.pdf (1.58 MB)
Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
Abstract
A saddle-shaped aza-nanographene containing a central 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP) has been prepared via a rationally designed four-step synthetic pathway encompassing intramolecular direct arylation, the Scholl reaction, and finally photo-induced radical cyclization. The target non-alternant, nitrogen-embedded polycyclic aromatic hydrocarbon (PAH) incorporates two abutting pentagons between four adjacent heptagons forming unique 7−7−5−5−7−7 topology. Such a combination of oddmembered-ring defects entails a negative Gaussian curvature within its surface with a significant distortion from planarity (saddle height z 4.3 °A). Its absorption and fluorescence maxima are located in the orange-red region, with weak emission originating from the intramolecular charge-transfer character of a low-energy absorption band. Cyclic voltammetry measurements revealed that this stable under ambient conditions aza-nanographene underwent three fully reversible oxidation steps (two oneelectron followed by one two-electron) with an exceptionally low first oxidation potential of Eox1 = −0.38 V (vs. Fc/Fc+).
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Citation
Chem. Sci., 2023, 14, 2353–2360 ; https://doi.org/10.1039/D2SC05858H