Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation
<p>Trityl radicals feature prominently as polarizing agents in solid-state dynamic nuclear polarization experiments and as spin labels in distance distribution measurements by pulsed dipolar EPR spectroscopy techniques. Electron-spin coherence lifetime is a main determinant of performance in t...
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Copernicus Publications
2025-01-01
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| Series: | Magnetic Resonance |
| Online Access: | https://mr.copernicus.org/articles/6/15/2025/mr-6-15-2025.pdf |
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| author | G. Jeschke N. Wili N. Wili Y. Wu S. Kuzin H. Karas H. Hintz A. Godt |
| author_facet | G. Jeschke N. Wili N. Wili Y. Wu S. Kuzin H. Karas H. Hintz A. Godt |
| author_sort | G. Jeschke |
| collection | DOAJ |
| description | <p>Trityl radicals feature prominently as polarizing agents in solid-state dynamic nuclear polarization experiments and as spin labels in distance distribution measurements by pulsed dipolar EPR spectroscopy techniques. Electron-spin coherence lifetime is a main determinant of performance in these applications. We show that protons in these radicals contribute substantially to decoherence, although the radicals were designed with the aim of reducing proton hyperfine interaction. By spin dynamics simulations, we can trace back the nearly complete Hahn echo decay for a Finland trityl radical variant within 7 <span class="inline-formula">µ</span>s to the contribution from tunnelling of the 36 methyl protons in the radical core. This contribution, as well as the contribution of methylene protons in OX063 and OX071 trityl radicals, to Hahn echo decay can be predicted rather well by the previously introduced analytical pair product approximation. In contrast, predicting decoherence of electron spins dressed by a microwave field proves to be a hard problem where correlations between more than two protons contribute substantially. Cluster correlation expansion (CCE) becomes borderline numerically unstable already at order 3 at times comparable to the decoherence time <span class="inline-formula"><i>T</i><sub>2<i>ρ</i></sub></span> and cannot be applied at order 4. We introduce partial CCE that alleviates this problem and reduces computational effort at the expense of treating only part of the correlations at a particular order. Nevertheless, dressed-spin decoherence simulations for systems with more than 100 protons remain out of reach, whereas they provide only semi-quantitative predictions for 24 to 48 protons. Our experimental and simulation results indicate that solid-state magnetic resonance experiments with trityl radicals will profit from perdeuteration of the compounds.</p> |
| format | Article |
| id | doaj-art-7d0f2183acb348cfb8b0b6719bd4f636 |
| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
| publisher | Copernicus Publications |
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| series | Magnetic Resonance |
| spelling | doaj-art-7d0f2183acb348cfb8b0b6719bd4f6362025-01-22T06:43:33ZengCopernicus PublicationsMagnetic Resonance2699-00162025-01-016153210.5194/mr-6-15-2025Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiationG. Jeschke0N. Wili1N. Wili2Y. Wu3S. Kuzin4H. Karas5H. Hintz6A. Godt7Department of Chemistry and Applied Biosciences, Institute of Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, SwitzerlandDepartment of Chemistry and Applied Biosciences, Institute of Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, SwitzerlandInterdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, Aarhus C, 8000, DenmarkDepartment of Chemistry and Applied Biosciences, Institute of Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, SwitzerlandDepartment of Chemistry and Applied Biosciences, Institute of Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, SwitzerlandDepartment of Chemistry and Applied Biosciences, Institute of Molecular Physical Science, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, SwitzerlandFaculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, GermanyFaculty of Chemistry and Center for Molecular Materials (CM2), Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany<p>Trityl radicals feature prominently as polarizing agents in solid-state dynamic nuclear polarization experiments and as spin labels in distance distribution measurements by pulsed dipolar EPR spectroscopy techniques. Electron-spin coherence lifetime is a main determinant of performance in these applications. We show that protons in these radicals contribute substantially to decoherence, although the radicals were designed with the aim of reducing proton hyperfine interaction. By spin dynamics simulations, we can trace back the nearly complete Hahn echo decay for a Finland trityl radical variant within 7 <span class="inline-formula">µ</span>s to the contribution from tunnelling of the 36 methyl protons in the radical core. This contribution, as well as the contribution of methylene protons in OX063 and OX071 trityl radicals, to Hahn echo decay can be predicted rather well by the previously introduced analytical pair product approximation. In contrast, predicting decoherence of electron spins dressed by a microwave field proves to be a hard problem where correlations between more than two protons contribute substantially. Cluster correlation expansion (CCE) becomes borderline numerically unstable already at order 3 at times comparable to the decoherence time <span class="inline-formula"><i>T</i><sub>2<i>ρ</i></sub></span> and cannot be applied at order 4. We introduce partial CCE that alleviates this problem and reduces computational effort at the expense of treating only part of the correlations at a particular order. Nevertheless, dressed-spin decoherence simulations for systems with more than 100 protons remain out of reach, whereas they provide only semi-quantitative predictions for 24 to 48 protons. Our experimental and simulation results indicate that solid-state magnetic resonance experiments with trityl radicals will profit from perdeuteration of the compounds.</p>https://mr.copernicus.org/articles/6/15/2025/mr-6-15-2025.pdf |
| spellingShingle | G. Jeschke N. Wili N. Wili Y. Wu S. Kuzin H. Karas H. Hintz A. Godt Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation Magnetic Resonance |
| title | Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| title_full | Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| title_fullStr | Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| title_full_unstemmed | Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| title_short | Electron-spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| title_sort | electron spin decoherence in trityl radicals in the absence and presence of microwave irradiation |
| url | https://mr.copernicus.org/articles/6/15/2025/mr-6-15-2025.pdf |
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