Buchner-type ring expansion of aromatic main-group biradicaloids toward phosphorus radical-derived NIR-II photothermal materials.

ABSTRACT: The Büchner reaction enables the construction of functionalized cycloheptatrienes and aromatic tropylium cations, and has recently been extended to the ring expansion of arenes with low-valent main-group systems. Although stable 6π-aromatic biradicaloids typically exhibit characteristic biradical reactivity, we leverage the aromaticity of dicarbondiphosphides (1) to achieve an unprecedented Büchner-type ring expansion, yielding air-stable aromatic 1,3-diphospholium cations (3). Multimodal characterization (NMR, UV-vis, SC-XRD, computational studies) confirms the 6π-aromaticity of 3. Reduction of 3 yields stable 7π-electron neutral radicals (4), which contrast with conventional five-membered neutral radicals possessing 5π-electron systems. These radicals (4a: λ _max = 1113.

SUBMITTER: Liu S 

PROVIDER: S-EPMC12434498 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature