Axially Chiral Stable Radicals: Resolution and Characterization of Blatter Radical Atropisomers

Atropisomers of three Blatter radicals
were obtained by the addition
of 8-substituted 1-naphthyllithiums to 3-phenyl and 3-t-butylbenzo­[e]­[1,2,4]­triazine and separated by chiral
high-performance liquid chromatography. Their absolute configurations
were assigned by a comparison of experimental and time-dependent density
functional theory calculated electronic circular dichroism spectra.
The free energy of activation, ΔG‡298, and the half life of racemization, t1/2, at 298 K were determined at ∼25 kcal mol–1 and <130 h, respectively. Intramolecular π–π
interactions in radicals were evident from single-crystal X-ray diffraction,
density functional theory, and electrochemical analyses.