Electrochemical and Electrostatic Cleavage of Alkoxyamines
© 2017 American Chemical Society. Alkoxyamines are heat-labile molecules, widely used as an in situ source of nitroxides in polymer and materials sciences. Here we show that the one-electron oxidation of an alkoxyamine leads to a cation radical intermediate that even at room temperature rapidly frag...
| Main Authors: | , , , , , , , , , , |
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| Format: | Journal Article |
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American Chemical Society
2018
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| Online Access: | http://purl.org/au-research/grants/arc/DE160100732 http://hdl.handle.net/20.500.11937/65431 |
| _version_ | 1848761130786226176 |
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| author | Zhang, L. Laborda, E. Darwish, Nadim Noble, B. Tyrell, J. Pluczyk, S. Le Brun, A. Wallace, G. Gonzalez, J. Coote, M. Ciampi, Simone |
| author_facet | Zhang, L. Laborda, E. Darwish, Nadim Noble, B. Tyrell, J. Pluczyk, S. Le Brun, A. Wallace, G. Gonzalez, J. Coote, M. Ciampi, Simone |
| author_sort | Zhang, L. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2017 American Chemical Society. Alkoxyamines are heat-labile molecules, widely used as an in situ source of nitroxides in polymer and materials sciences. Here we show that the one-electron oxidation of an alkoxyamine leads to a cation radical intermediate that even at room temperature rapidly fragments, releasing a nitroxide and carbocation. Digital simulations of experimental voltammetry and current-time transients suggest that the unimolecular decomposition which yields the "unmasked" nitroxide (TEMPO) is exceedingly rapid and irreversible. High-level quantum computations indicate that the collapse of the alkoxyamine cation radical is likely to yield a neutral nitroxide radical and a secondary phenylethyl cation. However, this fragmentation is predicted to be slow and energetically very unfavorable. To attain qualitative agreement between the experimental kinetics and computational modeling for this fragmentation step, the explicit electrostatic environment within the double layer must be accounted for. Single-molecule break-junction experiments in a scanning tunneling microscope using solvent of low dielectric (STM-BJ technique) corroborate the role played by electrostatic forces on the lysis of the alkoxyamine C-ON bond. This work highlights the electrostatic aspects played by charged species in a chemical step that follows an electrochemical reaction, defines the magnitude of this catalytic effect by looking at an independent electrical technique in non-electrolyte systems (STM-BJ), and suggests a redox on/off switch to guide the cleavage of alkoxyamines at an electrified interface. |
| first_indexed | 2025-11-14T10:26:47Z |
| format | Journal Article |
| id | curtin-20.500.11937-65431 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:26:47Z |
| publishDate | 2018 |
| publisher | American Chemical Society |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-654312022-09-06T02:46:07Z Electrochemical and Electrostatic Cleavage of Alkoxyamines Zhang, L. Laborda, E. Darwish, Nadim Noble, B. Tyrell, J. Pluczyk, S. Le Brun, A. Wallace, G. Gonzalez, J. Coote, M. Ciampi, Simone © 2017 American Chemical Society. Alkoxyamines are heat-labile molecules, widely used as an in situ source of nitroxides in polymer and materials sciences. Here we show that the one-electron oxidation of an alkoxyamine leads to a cation radical intermediate that even at room temperature rapidly fragments, releasing a nitroxide and carbocation. Digital simulations of experimental voltammetry and current-time transients suggest that the unimolecular decomposition which yields the "unmasked" nitroxide (TEMPO) is exceedingly rapid and irreversible. High-level quantum computations indicate that the collapse of the alkoxyamine cation radical is likely to yield a neutral nitroxide radical and a secondary phenylethyl cation. However, this fragmentation is predicted to be slow and energetically very unfavorable. To attain qualitative agreement between the experimental kinetics and computational modeling for this fragmentation step, the explicit electrostatic environment within the double layer must be accounted for. Single-molecule break-junction experiments in a scanning tunneling microscope using solvent of low dielectric (STM-BJ technique) corroborate the role played by electrostatic forces on the lysis of the alkoxyamine C-ON bond. This work highlights the electrostatic aspects played by charged species in a chemical step that follows an electrochemical reaction, defines the magnitude of this catalytic effect by looking at an independent electrical technique in non-electrolyte systems (STM-BJ), and suggests a redox on/off switch to guide the cleavage of alkoxyamines at an electrified interface. 2018 Journal Article http://hdl.handle.net/20.500.11937/65431 10.1021/jacs.7b11628 http://purl.org/au-research/grants/arc/DE160100732 http://purl.org/au-research/grants/arc/DE160101101 American Chemical Society fulltext |
| spellingShingle | Zhang, L. Laborda, E. Darwish, Nadim Noble, B. Tyrell, J. Pluczyk, S. Le Brun, A. Wallace, G. Gonzalez, J. Coote, M. Ciampi, Simone Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title | Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title_full | Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title_fullStr | Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title_full_unstemmed | Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title_short | Electrochemical and Electrostatic Cleavage of Alkoxyamines |
| title_sort | electrochemical and electrostatic cleavage of alkoxyamines |
| url | http://purl.org/au-research/grants/arc/DE160100732 http://purl.org/au-research/grants/arc/DE160100732 http://hdl.handle.net/20.500.11937/65431 |