Structural and electronic factors relating to the stability of imidazolidine nitroxide radicals

Fifteen imidazolidine nitroxide radicals were synthesised, and their stabilities against ascorbate were investigated.Among them, it was found that radicals bearing OH groups exhibited improved stabilities.In addition, density functional theory calculations, evaluation method of steric shielding effect around nitroxide radical reaction center based on molecular volume within a virtual ball, multiple regression analysis showed that the half-lives of these radicals were influenced both by steric effects and by the charge on the ring nitrogen atom.