Article by Prof. Daniel Gryko in Chemical Science

5 January 2023

Prof. Daniel Gryko with collaborators (Prof. Andrzej Sobolewski and Prof. Michał Cyrański) discovered novel bowl-shaped nitrogen-doped nanographene composed of a pyrrolo[3,2-b]pyrrole core substituted with six arene rings circularly bonded with one another. Dr. Maciej Krzeszewski is the first author of this paper. 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 the 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 odd-membered-ring defects entails a negative Gaussian curvature within its surface with a significant distortion from planarity (saddle height ≈4.3 Å). 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.