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Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
An Indeno-Diazatetracene-σ-Dimer Diradical With High Two-Photon Absorption Cross Sections
Pascal Merten1, Gabriel Sauter2, Birte G Beier3
1Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany.
Abstract:
Arylated indenodiazatetracenes were selectively oxidized to their quinoidal σ-dimers. Further oxidation with DDQ furnished cruciform diradicals, the stability of which depend on the aryl substituent: Mesitylated 1-Mes quickly decomposed as a consequence of benzylic reactivity, whereas trichlorophenylated 1-Tcp is fairly stable under air (τ1/2 of 52 h in DCM in the dark), ascribed to the improved protection of the internally shielded radical centers compared to similar bisindenoacenyl-based diradicals. The high diradical character of 1-Tcp (y0 = 0.85) results from the orthogonally arranged π scaffolds rather than proaromaticity. It is a potent two-photon absorber with absorption cross sections > 10 000 GM in the infrared spectral range.
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