{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:29:04Z","timestamp":1760243344309,"version":"build-2065373602"},"reference-count":22,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2014,10,28]],"date-time":"2014-10-28T00:00:00Z","timestamp":1414454400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The radical cation of s-trioxane, radiolytically generated in a freon (CF3CCl3) matrix, was studied in the 10\u2013140 K temperature region. Reversible changes of the EPR spectra were observed, arising from both ring puckering and ring inversion through the molecular plane. The ESREXN program based on the Liouville density matrix equation, allowing the treatment of dynamical exchange, has been used to analyze the experimental results. Two limiting conformer structures of the s-trioxane radical cation were taken into account, namely \u201crigid\u201d half-boat and averaged planar ones, differing strongly in their electron distribution. The spectrum due to the \u201crigid\u201d half-boat conformer can be observed only at very low (&lt;60 K) temperatures, when the exchange of conformers is very slow. Two transition states for interconversion by puckering and ring-inversion were identified, close in activation energy (2.3 and 3.0 kJ\/mol calculated). Since the energy difference is very small, both processes set on at a comparable temperature. In the case of nearly complete equilibration (fast exchange) between six energetically equivalent structures at T &gt; 120 K in CF3CCl3, a septet due to six equivalent protons (hfs splitting constant 5.9 mT) is observed, characteristic of the dynamically averaged planar geometry of the radical cation. DFT quantum chemical calculations and spectral simulation including intramolecular dynamical exchange support the interpretation.<\/jats:p>","DOI":"10.3390\/molecules191117305","type":"journal-article","created":{"date-parts":[[2014,10,28]],"date-time":"2014-10-28T10:25:07Z","timestamp":1414491907000},"page":"17305-17313","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["The Dynamical Behavior of the s-Trioxane Radical Cation\u2014A Low-Temperature EPR and Theoretical Study"],"prefix":"10.3390","volume":"19","author":[{"given":"Sergej","family":"Naumov","sequence":"first","affiliation":[{"name":"Ingenieurgesellschaft Auto und Verkehr (IAV GmbH), Rockwellstra\u00dfe 16, Gifhorn D-38518, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wolfgang","family":"Knolle","sequence":"additional","affiliation":[{"name":"Leibniz-Institute for Surface Modification, Permoserstra\u00dfe 15, Leipzig D-04318, Gemany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sergej","family":"Naumov","sequence":"additional","affiliation":[{"name":"Leibniz-Institute for Surface Modification, Permoserstra\u00dfe 15, Leipzig D-04318, Gemany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andreas","family":"P\u00f6ppl","sequence":"additional","affiliation":[{"name":"Department of Physics, University of Leipzig, Linn\u00e9stra\u00dfe 5, Leipzig D-04103, Gemany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Igor","family":"Janovsk\u00fd","sequence":"additional","affiliation":[{"name":"Leibniz-Institute for Surface Modification, Permoserstra\u00dfe 15, Leipzig D-04318, Gemany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2014,10,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2062","DOI":"10.1021\/ja00371a063","article-title":"Delocalized Pi-Radical Cations of Acetals","volume":"104","author":"Snow","year":"1982","journal-title":"J. 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