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A tailored multi-frequency EPR approach to accurately determine the magnetic resonance parameters of dynamic nuclear polarization agents: application to AMUPol
- Source :
- Physical Chemistry Chemical Physics, 2017(19), 3777. Royal Society of Chemistry, Physical Chemistry Chemical Physics, 19(5), 3777-3781
- Publication Year :
- 2017
-
Abstract
- To understand the dynamic nuclear polarization (DNP) enhancements of biradical polarizing agents, the magnetic resonance parameters need to be known. We describe a tailored EPR approach to accurately determine electron spin-spin coupling parameters using a combination of standard (9 GHz), high (95 GHz) and ultra-high (275 GHz) frequency EPR. Comparing liquid- and frozen-solution continuous-wave EPR spectra provides accurate anisotropic dipolar interaction D and isotropic exchange interaction J parameters of the DNP biradical AMUPol. We found that D was larger by as much as 30% compared to earlier estimates, and that J is 43 MHz, whereas before it was considered to be negligible. With the refined data, quantum mechanical calculations confirm that an increase in dipolar electron-electron couplings leads to higher cross-effect DNP efficiencies. Moreover, the DNP calculations qualitatively reproduce the difference of TOTAPOL and AMUPol DNP efficiencies found experimentally and suggest that AMUPol is particularly effective in improving the DNP efficiency at magnetic fields higher than 500 MHz. The multi-frequency EPR approach will aid in predicting the optimal structures for future DNP agents.
- Subjects :
- 010405 organic chemistry
Chemistry
Physics::Medical Physics
Exchange interaction
General Physics and Astronomy
Electron
010402 general chemistry
Polarization (waves)
01 natural sciences
Molecular physics
Spectral line
0104 chemical sciences
law.invention
Magnetic field
Dipole
Nuclear magnetic resonance
law
Physical and Theoretical Chemistry
Electron paramagnetic resonance
Anisotropy
Subjects
Details
- Language :
- English
- ISSN :
- 14639076
- Database :
- OpenAIRE
- Journal :
- Physical Chemistry Chemical Physics, 2017(19), 3777. Royal Society of Chemistry, Physical Chemistry Chemical Physics, 19(5), 3777-3781
- Accession number :
- edsair.doi.dedup.....0afba34d65c6d017eb92e48760e40030