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Triindenotriphenylenes: Spin-Frustrated Triskelion Triradicals with Excellent Ambient Stability.

Arseni BorissovPiotr J ChmielewskiAbel Cárdenas ValdiviaCarlos J Gómez GarcíaJuan CasadoMarcin Stępień
Published in: Angewandte Chemie (International ed. in English) (2024)
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.
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