Hidden aromaticity behind paratropic ring currents in oxoverdazyl and benzotriazinyl radicals

Monoradicals occupy a theoretically underdetermined state in aromaticity theory, possessing both aromatic (2 n + 1) and antiaromatic (2 n ) spin populations. We systematically investigate benzotriazinyl and oxoverdazyl radicals by disentangling their energetic and magnetic aromaticity through isodesmic reactions, NICS calculations, and EDDB analysis. Our results reveal that both systems are energetically aromatic, yet sustain paratropic ring currents, revealing the divergence of energetic and magnetic criteria. EDDB analysis unveils the electronic origin of this divergence: the antiaromatic α-spins with the unpaired electron are largely localized, whereas the aromatic β-spins are extensively delocalized within the heterocyclic rings. This spin-specific localization provides a direct electronic rationale for the observed dichotomy and contributes to the refinement of Mandado's electron rule for odd-electron systems, demonstrating that the two spin populations influence energetic and magnetic properties differently. Oxidation and reduction of the parent radicals lead to convergence of these criteria in closed-shell ions, offering insights into their reversible redox behavior. This study provides a quantitative framework for understanding aromaticity in odd-electron species.