Synthesis and Properties of a Highly Congested Tri(9-anthryl)methyl Radical.

The synthesis of persistent, neutral organic radicals is challenging because of their inherent reactivities. Herein, we report the synthesis and characterization of a highly congested mesityl-substituted tri(9-anthryl)methyl (TAntM) radical (1). The scaffold was successfully synthesized by circumventing the steric hindrance imposed by the bulky groups surrounding the central methyl carbon atom. The radical has a threefold propeller structure, and the unpaired electron is mainly localized on the central carbon atom. Owing to its congested structure, 1 is remarkably stable, which facilitated handling under ambient conditions. Evaluation of the dynamic behavior of the TAntM scaffold indicated that the stability is due to the bulky anthryl units and the mesityl substituents. Because of its high persistence, wide-range absorption, and good reversible redox properties, 1 has promising applications in organic devices.