(Invited) Synthesis and Functionalization of Nanographenes with Red to Near-Infrared Emission for Photonic Applications

Nanostructures of graphene demonstrate a wide range of optical, electronic, and magnetic properties depending on their size and chemical structures, which renders them promising as next-generation carbon-based nanomaterials, e.g., for nanoelectronics, spintronics, and photonics. However, it is challenging to accurately control the chemical structures while “cutting” graphene. To this end, large polycyclic aromatic hydrocarbons (PAHs) with nanoscale graphene structures are attracting a renewed attention as atomically precise nanographenes 1. We have developed the synthesis of dibenzo hi , st ovalene (DBOV) as an unprecedented nanographene with high stability, strong red fluorescence, and stimulated emission, demonstrating the potential for organic lasers 2. The functionalization of DBOV was achieved through regioselective bromination and Suzuki coupling, enabling the introduction of various substituents, for example fluoranthene imide (FAI) groups, inducing the red-shift of the emission to the near-infrared (NIR) region 3. Different effects on the photophysical properties of the DBOV core have been observed by changing the peripheral functional groups. More recently, we have synthesized hexabenzoperihexacene (HBPH) with zigzag and fjord edges, which displayed high stability and NIR emission with maximum at ~800 nm 4. Notably, HBPH could be made chiral by introducing bulky tert- butyl groups on the helical fjord edges, allowing the separation of the enantiomers and showing the circular dichroism responses up to 830 nm. These results provide a new insight into the structure-property relationship of such nanographenes and pave the way toward their photonic applications. 1 Paternò, G. M.; Goudappagouda,; Chen, Q.; Lanzani, G.; Scotognella, F; Narita A., Adv. Optical Mater . 2021 , 9, 2100508. 2 Paternò, G. M.; Chen, Q.; Wang, X.-Y.; Liu, J.; Motti, S. G.; Petrozza, A.; Feng, X.; Lanzani, G.; Müllen, K.; Narita, A.; Scotognella, F., Angew. Chem. Int. Ed. 2017, 56 , 6753–6757. 3 Paternò, G. M.; Chen, Q.; Muñoz-Mármol, R.; Guizzardi, M.; Bonal, V.; Kabe, R.; Barker, A. J.; Boj, P. G.; Chatterjee, S.; Ie, Y.; Villalvilla, J. M.; Quintana, J. A.; Scotognella, F.; Müllen, K.; Díaz-García, M. A.; Narita, A.; Lanzani, G., Mater. Horiz . 2022 , 9 , 393–402. 4 Xu, X.; Muñoz-Mármol, R.; Vasylevskyi, S.; Villa, A.; Folpini, G.; Scotognella, F.; Paternò, G. M.; Narita, A., Angew. Chem. Int. Ed. 2023 , 62 , e202218350.