Author: ["Ganna Gryn'ova","David L. Marshall","Stephen J. Blanksby","Michelle L. Coote"]
CITE.CC academic search helps you expand the influence of your papers.
Abstract
In most radicals the singly occupied molecular orbital (SOMO) is the highest-energy occupied molecular orbital (HOMO); however, in a small number of reported compounds this is not the case. In the present work we expand significantly the scope of this phenomenon, known as SOMO–HOMO energy-level conversion, by showing that it occurs in virtually any distonic radical anion that contains a sufficiently stabilized radical (aminoxyl, peroxyl, aminyl) non-π-conjugated with a negative charge (carboxylate, phosphate, sulfate). Moreover, regular orbital order is restored on protonation of the anionic fragment, and hence the orbital configuration can be switched by pH. Most importantly, our theoretical and experimental results reveal a dramatically higher radical stability and proton acidity of such distonic radical anions. Changing radical stability by 3–4 orders of magnitude using pH-induced orbital conversion opens a variety of attractive industrial applications, including pH-switchable nitroxide-mediated polymerization, and it might be exploited in nature. In most radicals the unpaired electron occupies the highest-energy molecular orbital. Here, it is shown that for certain stabilized radicals the presence of a remote negatively charged group not only inverts this ordering, but also leads to a dramatic increase in radical stability that is easily manipulated by pH. Cite this article
Gryn'ova, G., Marshall, D., Blanksby, S. et al. Switching radical stability by pH-induced orbital conversion. Nature Chem 5, 474–481 (2013). https://doi.org/10.1038/nchem.1625 