Nitronylnitroxide radicals

Fig. 17 Potential exchange pathways for phenolic nitronylnitroxide radicals.

Fig. 29 Hydrogen-bonded chains that organize radicals into FM exchange-coupled piled stack motif among nitronylnitroxide radicals in BlmNN. Inset (right) shows the piled stack spin orbit N-O/C contact that gives rise to FM exchange.

Fig. 13 (a, b) MAS NMR spectra of two nitronylnitroxide radicals (spinning rates of 10 kHz and 15 kHz, respectively), together with the corresponding sign patterns of the spm densities experimentally derived from the Fermi contact shifts up-spins indicate positive spin), (e) Side view of an unsubstituted nitronylnitroxide down from the center of the bond C4-C5 to C2. The spin-carrying MO is located on the NO groups. Reprinted with permission from [51], (C) 1999 American Chemical Society... 

At about the time that the work on BABI appeared, Yoshioka et al. reported magnetostructural studies of other variations of BIm having a nitronylnitroxide group in the 2-position, such as BImNN.194 Nitronylonitroxides are much less delocalizable than the aminoxyl radicals used in BABI and PhBABI. Computed... 

The phenalenyl radical 4 represents the most fundamental and widely explored member in this family. Unlike typical stable neutral radicals such as TEMPO and a-nitronylnitroxide derivatives with a spin-localized nature, 4 is characterized by a planar, rigid structure with the spin spread over the whole molecular skeleton (Fig. 3). The resonance structures of 4 show that the spin density is predominantly at its oc positions, while the spin at the peripheral positions (jS positions) is much smaller, which can be explained by the spin polarization effect. In addition, 4 exhibits a high amphoteric redox ability with thermodynamically stable cation, neutral radical and anion species. All of these features of 4 lead to new insights in the field of physical chemistry. 

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