Polar effects on radical stability are traditionally attributed either to resonance effects or to dipole effects. The former involves donor-acceptor interactions between specific functional groups that are conjugated or hyperconjugated with one another; the latter involves through space electrostatic interactions between charged (or partially charge-separated) functional groups. Both types of effects are strongly directional. However, we have recently discovered a new 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 stabilized compared with its corresponding non-radical derivatives. The effect arises in the enhanced polarisability of delocalised radicals compared with their corresponding closed-shell counterparts. In this way the destabilising interaction between a remote negative charge and an unpaired electron is minimised and a greater overall stabilisation of the species through charge-nuclei attraction is achieved. We are now working towards harnessing both conventional and non-directional polar effects to develop electrostatic catalysis based on both external electric fields and acid/base groups whose charge can be manipulated via pH.
Selected recent publications
- Gryn'ova G., Marshall D.L., Blanksby S.J., & Coote M.L. (2013) Switching Radical Stability By pH-Induced Orbital Conversion Nature Chem., 5, pp. 474-481.
- Gryn’ova G., Coote M.L. (2013) Origin and scope of long-range stabilizing interactions and associated SOMO-HOMO conversion in distonic radical anions J. Am. Chem. Soc., 135, pp. 15392-15403.