MIT

Dynamic nuclear polarization with biradicals.

Title

Dynamic nuclear polarization with biradicals.

Publication Type
Journal Article
Year of Publication
2004
Journal
Journal of the American Chemical Society
Volume
126
Pagination
10844–5
Date Published
sep
ISSN
0002-7863
Abstract
Dynamic nuclear polarization (DNP) experiments in rotating solids have been performed for the first time using biradicals rather than monomeric paramagnetic centers as polarizing agents. Specifically, two TEMPO radicals were tethered with a poly(ethylene glycol) chain of variable length where the number of glycol units was 2, 3, or 4. NMR experiments show that the signal observed in DNP experiments is approximately inversely proportional to the length of the chain. Thus, the shorter chain with larger electron dipolar couplings yields larger enhancements. The size of the enhancement is a factor of 4 larger than obtained with the identical concentration of monomeric nitroxide radicals achieving a value of approximately 175 for the n = 2 chain.