Polar effects on radical stability
Polar effects on radical stability are traditionally attributed either to resonance or dipole interactions, both of which are strongly directional. However, Anya Gryn'ova and Michelle Coote have now discovered a third type of polar effect that is in principle non-directional and requires no conjugation or permanent dipoles. When a localised anion is placed in the vicinity of a delocalised radical, the radical is strongly stabilised compared with its corresponding non-radical derivatives due to its enhanced polarisability. The arising polar effects are surprisingly large and long range, and are likely to be useful in synthesis and harnessed in enzyme catalysis.
Origin and Scope of Long-Range Stabilizing Interactions and Associated SOMO-HOMO Conversion in Distonic Radical Anions, J. Am. Chem. Soc. 2013, 135, 15392