Switching radical stability by pH-induced orbital conversion

Gryn'ova, G., Marshall, D. L., Blanksby, S. J., & Coote, M. L. (2013) Switching radical stability by pH-induced orbital conversion. Nature Chemistry, 5(6), pp. 474-481.

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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-pi-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.

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ID Code: 68879
Item Type: Journal Article
Refereed: Yes
Keywords: nitroxide-mediated polymerization, gas-phase acidities, kinetic method, thermochemical determinations, electronic-structure, cyclic nitroxides, level conversion, chemistry, energies, anions
DOI: 10.1038/nchem.1625
ISSN: 1755-4330
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Nature Publishing Group
Deposited On: 20 Mar 2014 02:16
Last Modified: 10 Apr 2014 06:49

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