Triangulene, also known as Clar’s hydrocarbon, has been sought after by chemists for more than 70 years but with limited success. Herein, we report an oxidative dehydrogenation method to synthesize two kinetically blocked [3]triangulene derivatives
TRI-1 (reported) and
TRI-2 (newly synthesized), in which
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Triangulene, also known as Clar’s hydrocarbon, has been sought after by chemists for more than 70 years but with limited success. Herein, we report an oxidative dehydrogenation method to synthesize two kinetically blocked [3]triangulene derivatives
TRI-1 (reported) and
TRI-2 (newly synthesized), in which the three most reactive sites are substituted by bulky mesityl groups and electron-withdrawing 2,4,6-trichlorophenyl groups, and meanwhile, three vertices of triangulene are substituted by tert-butyl groups. Interestingly, the dihydro-triangulene core possesses two isomers well characterized by UV-vis, NMR spectroscopy, and X-ray crystallographic analysis, which is interestingly substituent-dependent. The newly synthesized
TRI-2 is isolated in crystalline form, and X-ray crystallographic analysis reveals that the aryl substituents are nearly perpendicular to the triangulene plane and thus cause little perturbation of the electronic properties of the triangulene. Notably, 2,4,6-trichlorophenyl-substituted
TRI-2 exhibits enhanced stability compared to the reported mesityl-substituted
TRI-1, e.g.,
TRI-2 is stable for months in a crystalline state under a nitrogen atmosphere, and
TRI-2 in a solution state is also more persistent than
TRI-1 (half-life for
TRI-1 ≈ 18 h vs.
TRI-2 ≈ 132 h). This achievement will facilitate the design and synthesis of stable triangulene dimers and oligomers with higher spin multiplicity.
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