Highly Efficient, Water‐Soluble Polarizing Agents for Dynamic Nuclear Polarization at High Frequency

Well polarized: Two new polarizing agents PyPol and AMUPol soluble in glycerol/water mixtures are used for dynamic nuclear polarization (DNP) NMR spectroscopy. The enhancement factors (ε) are about 3.5 to 4 times larger than for the established agent TOTAPOL at 263 and 395 GHz. For AMUPol, the temperature dependence of ε allows DNP experiments to be performed at temperatures significantly higher than for typical high-field DNP NMR experiments.