Triindenotriphenylenes: Spin‐Frustrated Triskelion Triradicals with Excellent Ambient Stability

A triskelion‐shaped triradical triindeno[1,2‐ a :1′,2′‐ g : 1′′,2′′‐ m ]triphenylen‐7‐yl ( 1 ) and its internally fused derivative ( 2 ) obtained by oxidative cyclization were prepared in a straightforward synthetic sequence. Both compounds were confirmed to be triradicals and to possess intramolecular antiferromagnetic exchange interactions between spins, displaying a spin‐frustrated doublet ground state with doublet‐quartet energy gaps of −0.14 kcal/mol for 1 and −0.06 kcal/mol for 2 . Despite their open‐shell character, they were sufficiently stable to be handled under ambient conditions on a timescale of days. Both compounds could be reversibly reduced to mono‐, di‐, and trianions and oxidized to 1 + and 2 2+ , with strong NIR absorptions (1800 to over 3200 nm) observed for all open‐shell ions.