{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T15:52:51Z","timestamp":1791906771654,"version":"4.3.4"},"reference-count":53,"publisher":"American Chemical Society (ACS)","issue":"34","license":[{"start":{"date-parts":[[2015,12,3]],"date-time":"2015-12-03T00:00:00Z","timestamp":1449100800000},"content-version":"vor","delay-in-days":862,"URL":"https:\/\/pubs.acs.org\/page\/policy\/authorchoice_termsofuse.html"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2013,8,28]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>A series of seven functionalized nitroxide biradicals (the bTbK biradical and six derivatives) are investigated as exogenous polarization sources for dynamic nuclear polarization (DNP) solid-state NMR at 9.4 T and with ca. 100 K sample temperatures. The impact of electron relaxation times on the DNP enhancement (\u03b5) is examined, and we observe that longer inversion recovery and phase memory relaxation times provide larger \u03b5. All radicals are tested in both bulk 1,1,2,2-tetrachloroethane solutions and in mesoporous materials, and the difference in \u03b5 between the two cases is discussed. The impact of the sample temperature and magic angle spinning frequency on \u03b5 is investigated for several radicals each characterized by a range of electron relaxation times. In particular, TEKPol, a bulky derivative of bTbK with a molecular weight of 905 g\u00b7mol\u20131, is presented. Its high-saturation factor makes it a very efficient polarizing agent for DNP, yielding unprecedented proton enhancements of over 200 in both bulk and materials samples at 9.4 T and 100 K. TEKPol also yields encouraging enhancements of 33 at 180 K and 12 at 200 K, suggesting that with the continued improvement of radicals large \u03b5 may be obtained at higher temperatures.<\/jats:p>","DOI":"10.1021\/ja405813t","type":"journal-article","created":{"date-parts":[[2013,7,24]],"date-time":"2013-07-24T14:19:17Z","timestamp":1374675557000},"page":"12790-12797","source":"Crossref","is-referenced-by-count":417,"title":["Large Molecular Weight Nitroxide Biradicals Providing\nEfficient Dynamic Nuclear Polarization at Temperatures up to 200 K"],"prefix":"10.1021","volume":"135","author":[{"given":"Alexandre","family":"Zagdoun","sequence":"first","affiliation":[{"name":"Universite\u0301 de Lyon (CNRS\/ENS Lyon\/UCB Lyon 1) Centre de RMN a\u0300 Tre\u0300s Hauts Champs, Institut de Sciences Analytiques, , 69100 Villeurbanne, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gilles","family":"Casano","sequence":"additional","affiliation":[{"name":"Aix-Marseille Universite\u0301 , CNRS, ICR UMR 7273, 13397 Marseille, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Olivier","family":"Ouari","sequence":"additional","affiliation":[{"name":"Aix-Marseille Universite\u0301 , CNRS, ICR UMR 7273, 13397 Marseille, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Martin","family":"Schwarzwa\u0308lder","sequence":"additional","affiliation":[{"name":"ETH Zu\u0308rich Department of Chemistry, , CH-8093, Zu\u0308rich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aaron J.","family":"Rossini","sequence":"additional","affiliation":[{"name":"Universite\u0301 de Lyon (CNRS\/ENS Lyon\/UCB Lyon 1) Centre de RMN a\u0300 Tre\u0300s Hauts Champs, Institut de Sciences Analytiques, , 69100 Villeurbanne, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fabien","family":"Aussenac","sequence":"additional","affiliation":[{"name":"Bruker BioSpin SA , Wissembourg, 67160, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maxim","family":"Yulikov","sequence":"additional","affiliation":[{"name":"ETH Zu\u0308rich Department of Chemistry, , CH-8093, Zu\u0308rich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gunnar","family":"Jeschke","sequence":"additional","affiliation":[{"name":"ETH Zu\u0308rich Department of Chemistry, , CH-8093, Zu\u0308rich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christophe","family":"Cope\u0301ret","sequence":"additional","affiliation":[{"name":"ETH Zu\u0308rich Department of Chemistry, , CH-8093, Zu\u0308rich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne","family":"Lesage","sequence":"additional","affiliation":[{"name":"Universite\u0301 de Lyon (CNRS\/ENS Lyon\/UCB Lyon 1) Centre de RMN a\u0300 Tre\u0300s Hauts Champs, Institut de Sciences Analytiques, , 69100 Villeurbanne, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Paul","family":"Tordo","sequence":"additional","affiliation":[{"name":"Aix-Marseille Universite\u0301 , CNRS, ICR UMR 7273, 13397 Marseille, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lyndon","family":"Emsley","sequence":"additional","affiliation":[{"name":"Universite\u0301 de Lyon (CNRS\/ENS Lyon\/UCB Lyon 1) Centre de RMN a\u0300 Tre\u0300s Hauts Champs, Institut de Sciences Analytiques, , 69100 Villeurbanne, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2013,7,24]]},"reference":[{"key":"2026090217120607900_cit1","doi-asserted-by":"crossref","first-page":"411","DOI":"10.1103\/PhysRev.92.411","volume":"92","author":"Overhauser","year":"1953","journal-title":"Phys. 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