A Stable Trimethylenemethane Triplet Diradical Based on a Trimeric Porphyrin Fused π‐System. Issue 30 (21st June 2018)

• Record Type: Journal Article
• Authors: Kato, Kenichi; Furukawa, Ko; Osuka, Atsuhiro
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 30(2018)
• Page Start: 9491
• Page End: 9494
• Publication Date: 2018-06-21
• Subjects: diradicals -- ferromagnetic interactions -- fused-ring systems -- porphyrinoids -- trimethylenemethane; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201804644
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Trimethylenemethane (TMM) diradical is the simplest non‐Kekulé non‐disjoint molecule with the triplet ground state (Δ E ST =+16.1 kcal mol −1 ) and is extremely reactive. It is a challenge to design and synthesize a stable TMM diradical with key properties, such as actual aliphatic TMM diradical centers and the triplet ground state with a large positive Δ E ST value, since such species provide detailed information on the electronic structure of TMM diradical. Herein we report a TMM derivative, in which the TMM segment is fused with three Ni II meso ‐triarylporphyrins, that satisfies the above criteria. The diradical shows delocalized spin density on the propeller‐like porphyrin π‐network and the triplet ground state owing to the strong ferromagnetic interaction. Despite the apparent TMM structure, the diradical can be handled under ambient conditions and can be stored for months in the solid state, thus allowing its X‐ray diffraction structural analysis. Abstract : Twin radicals in the triplet state : A trimethylenemethane (TMM) diradical fused with three Ni II porphyrins was synthesized and structurally characterized (see structure). The diradical showed delocalized spin density over the propeller‐like porphyrin π‐network and had a triplet ground state with a large Δ E ST value. Despite the apparent aliphatic TMM structure, the diradical could be handled under ambient conditions and stored for months in the solid state.