We report high-spin aminyl triradicals with near-planar triphenylene backbones. Near-planarity of the fused aminyl radicals and the 2,6,10-triphenylene ferromagnetic coupling unit (FCU), magnetically equivalent to three fused 3,4′-biphenyl FCUs, assures an effective 2pπ–2pπ overlap within the cross-conjugated π-system, leading to an S = 3/2 (quartet) ground state that is well separated from low-spin excited doublet states. Thermal populations of the low-spin (S = 1/2) excited states are detectable both by SQUID magnetometry and electron paramagnetic resonance (EPR) spectroscopy, providing doublet–quartet energy gaps, ΔE DQ, corresponding to >85% population of the quartet ground states at room temperature. Notably, EPR-based determination of ΔE DQ relies on direct detection of the quartet ground state and doublet excited states. The ΔE DQ values are 1.0–1.1 kcal mol–1, with the more sterically shielded triradical having the larger value. The half-life of the more sterically shielded triradical in 2-methyltetrahydrofuran (2-MeTHF) is about 6 h at room temperature. The less sterically shielded triradical in 2-MeTHF decomposes at 158 K with a half-life of about 4 h, while at 195 K, the half-life is still about 2 h. The dominant products of the decay of triradicals are the corresponding triamines, suggesting hydrogen atom abstraction from the solvent as the primary mechanism. This study expands the frontier of the open-shell PAHs/nanographenes, of which the unique electronic, nonlinear optical, and magnetic properties could be useful in the development of novel organic electronics, photonics, and spintronics.

We report a metal- and oxidant-free aromatic C–C bond cleavage in the curved corannulene skeleton. Reaction of 1-aminocorannulene with hydrazonyl chloride generates an amidrazone intermediate that undergoes facile intramolecular proton migrations and ring annulation to give a 1,2,4-triazole derivative of planar benzo[ghi]fluoranthene, in which the release of strain associated with the curved π-surface and the formation of an aromatic triazole moiety are the driving forces. This report provides new insights into the aromatic C–C bond cleavage.