High Field Dynamic Nuclear Polarization with High-Spin Transition Metal Ions

Abstract

We report the dynamic nuclear polarization of 1H spins in magic-angle-spinning spectra recorded at 5 T and 84 K via the solid effect using Mn2+ and Gd[superscript 3+] complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective line width of the central (mS = −1/2 → +1/2) EPR transition. Using a Gd[superscript 3+] complex with a narrow central transition EPR line width of 29 MHz, we observed a maximum enhancement of 13, which is comparable to previous results on the narrow-line-width trityl radical.