19F and 1H NMR and ESR investigations of aryl-t-butyl nitroxides and nitronylnitroxides

¹H and ¹⁹F NMR and ESR spectra of several nitroxides have been recorded. The ¹⁹F couplings are sensitive to steric factors and this shows why the simple linear relationship a_F = O_eff^F· ?_C^π is not adequate. The π and σ spin delocalization mechanisms are demonstrated. The spin transmission via oxygen and sulphur is affected by geometry (efficiency of pπ-nπ overlap), pπ-dπ overlap only plays a role in positively charged S atoms (sulphones). The absolute sign of the proton coupling in an alkyl chain depends upon chain length and substituents. The syntheses of several stable nitroxides are described.