High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals.

High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Research Abstract Details 

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High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Abstract Text:

Kan-Nian Hu,Vikram S Bajaj,Melanie Rosay,Robert G Griffin,

In a previous communication [Hu et al., J. Am. Chem. Soc. 126, 10844 (2004)], an approach was demonstrated that improves the efficiency of the cross-effect polarization mechanism employed in high field dynamic nuclear polarization (DNP) experiments. Specifically, it was shown that tethering two TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) radicals increases the electron-electron dipole coupling from approximately 1 MHz in solutions of monomeric TEMPO to approximately 25 MHz in a tethered biradical. The larger coupling resulted in an increase in the DNP enhancements by a factor of approximately 3-4, from 45-50 to approximately 165. Here, a second approach to improving the efficiency of the polarization process is described that involves approximately satisfying the matching condition |omega(2e)-omega(1e)|=omega(n), where omega(2e) and omega(1e) are two frequencies in the electron paramagnetic resonance (EPR) spectrum and omega(n) is the Larmor frequency of the nuclear spins being polarized. Specifically, in a mixture of TEMPO and trityl [tris (8-carboxy-2,2,6,6-tetramethyl(-d3)-benzo[1,2d:4,5-d']bis(1,3)dithiol-4-yl) methyl] radicals, the intensity maxima in the EPR spectra of these two species are approximately separated by the (1)H NMR frequency. In this case the frequency difference between the g(yy) value of TEMPO and the narrow pseudo-isotropic g-value of trityl is approximately 224 MHz and the (1)H Larmor frequency is 211 MHz. The optimal magnetic field for DNP using the mixtures was found to coincide with the trityl EPR resonance. At 90 K and 5 T, a mixture of 20 mM TEMPO and 20 mM trityl enhanced the (1)H polarization by a factor of approximately 160, an improvement over the enhancement of approximately 50 with 40 mM TEMPO. The reasons for the improvement are discussed and evidence is presented suggesting that DNP enhancement can be improved further by tethering TEMPO and trityl or two similar radicals.

High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Publishing Authors By Initials

KN Hu,VS Bajaj,M Rosay,RG Griffin,

For similar organic chemicals: hydrocarbons: hydrocarbons, cyclic: hydrocarbons, aromatic: benzene derivatives: trityl compounds research abstracts see: organic chemicals: hydrocarbons: hydrocarbons, cyclic: hydrocarbons, aromatic: benzene derivatives: trityl compounds research

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High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: The Journal of chemical physics

VOLUME: 126

Page Numbers: 044512

Journal Abbreviation:

ISSN: 0021-9606

DAY: 28

MONTH: Jan

YEAR: 2007

High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 375360

High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Keywords Mesh Terms:

KEYWORDS: Trityl Compounds

MESH TERMS: chemistry

Chemical & Substance for Abstract: High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals. Information

Substance Name: TEMPO

Registry Number: 2564-83-2

Grant and Affiliation Information for High-frequency dynamic nuclear polarization using mixtures of TEMPO and trityl radicals.

AFFILIATION: Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Country: United States

AGENCY: United States NIBIB

GRANT: EB-002804

ACRONYM: EB

MEDLINETA: J Chem Phys

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