9,9′-Anthryl-anthroxyl radicals: strategic stabilization of highly reactive phenoxyl radicals

Stable 9,9'-anthryl-anthroxyl radicals were synthesized and isolated, and the structures were fully characterized by single crystal X-ray diffraction analysis and ESR measurement. The resonance structure and steric protection of the peripheral positions and the most reactive 9-position of anthracene prolong the half-life of the radical in solution to 11 days.