Synthesis and Isolation of a Kinetically Stabilized Crystalline Triangulene.

The synthesis and isolation of hydrocarbons with a triplet ground state in crystalline forms have been sought in materials science. Triangulene is one of the most famous triplet-ground-state benzenoid hydrocarbons. Its unique electronic structure and highly symmetric structure have prompted many scientists to synthesize and isolate triangulene and its derivatives, but all attempts so far to isolate them as crystals have been unsuccessful. Herein we report the synthesis and isolation of a kinetically stabilized crystalline triangulene for the first time. The key to success is the introduction of bulky substituents onto the reactive zigzag edges. Its highly symmetric structure was confirmed by X-ray crystallography, and its fundamental properties, including the triplet ground state, were revealed. The achievement here will open the door for the synthesis and isolation of other hydrocarbons with higher spin multiplicity.