Structural Factors Controlling the Spin鈥揝pin Exchange Coupling: EPR Spectroscopic Studies of Highly Asymmetric Trityl鈥揘itroxide Biradicals

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• 作者：Yangping Liu ; Frederick A. Villamena ; Antal Rockenbauer ; Yuguang Song ; Jay L. Zweier
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：February 13, 2013
• 年：2013
• 卷：135
• 期：6
• 页码：2350-2356
• 全文大小：357K
• 年卷期：v.135,no.6(February 13, 2013)
• ISSN：1520-5126

文摘

Highly asymmetric exchange-coupled biradicals, e.g., the trityl鈥搉itroxides (TNs), possess particular magnetic properties that have opened new possibilities for their application in biophysical, physicochemical, and biological studies. In the present work, we investigated the effect of the linker length on the spin鈥搒pin coupling interaction (J) in TN biradicals using the newly synthesized biradicals CT02-GT, CT02-AT, CT02-VT, and CT02-PPT as well as the previously reported biradicals TNN14 and TN1. The results show that the magnitude of J can be easily tuned from 4 G (conformer 1 in CT02-PPT) to >1200 G (in TNN14) by varying the linker separating the two radical moieties and changing the temperature. Computer simulations of EPR spectra were carried out to estimate J values of the TN biradicals directly. In addition to the spin鈥搒pin coupling interaction of TN biradicals, their g, hyperfine-splitting, and zero-field-splitting interactions were explored at low temperature (220 K). Our present study clearly shows that varying the spin鈥搒pin interaction as a function of linker distance and temperature provides an effective strategy for the development of new TN biradicals that can find wide applications in relevant fields.