Fused Triangulene Dimers: Facile Synthesis by Intramolecular Radical‐Radical Coupling and Application for Near‐Infrared Lasers

Large graphene-like molecules with four zigzag edges are ideal gain medium materials for organic near-infrared (NIR) lasers. However, synthesizing them becomes increasingly challenging as the molecular size increases. In this study, we introduce a new intramolecular radical-radical coupling approach and successfully synthesize two fused triangulene dimers (1a/1b) efficiently. X-ray crystallographic analysis of 1a indicates that there is no intermolecular π-π stacking in the solid state. When the more soluble derivative 1b is dispersed in polystyrene thin films, amplified spontaneous emission in the NIR region is observed. Using 1b as the active gain material, we fabricate solution-processed distributed feedback lasers that exhibit a narrow emission linewidth at around 790 nm. The laser devices also exhibit low thresholds with high photostability. Our study provides a new synthetic strategy for extended nanographenes, which have diverse applications in electronics and photonics. J.W. acknowledges financial support from the NRF Investigatorship Award (NRF-NRFI05-2019-0005), the A*STAR AME grant (A20E5c0089) and start-up grant from the Joint School of National University of Singapore and Tianjin University@Fuzhou. The group at the University of Alicante thanks financial support from the “Ministerio de Ciencia e Innovación” (MCIN) of Spain and the European Regional Development Fund (grant No. PID2020-119124RB-I00) and from the Generalitat Valenciana though grant No. AICO/2021/093. Besides, this study part of the Advanced Materials program supported by the Spanish MCIN with funding from European Union NextGenerationEU and by Generalitat Valenciana (grant no. MFA/2022/045). Z.S. is grateful to the financial support from National Natural Science Foundation of China (Grant No. 21971187, 22222110), Natural Science Foundation of Tianjin (19JCJQJC62700) and the Haihe Laboratory of Sustainable Chemical Transformations.