In this study, ~H and 13C dynamic nuclear polarization (DNP) was generated at a magnetic field strength of 0.33 T utilizing silica phase immobilized nitroxide (SPIN) samples. The pola¡ was subsequently transferred to flowing liquids and monitored at a magnetic field strength of 4.7 T. These solid/liquid intermolecular transfer (SLIT) experiments provide efficient polarization transfer without the necessity of the free radical system present in the monitoring fluid. Specifically, ultimate ~H SLIT DNP Overhauser enhancements of -5 6 and --110 have been observed for benzene and chloroform in the presence of SPIN system 2, respectively.The ~3C SLIT DNP enhancement for benzene is dominated by three-spin effects and poor leakage factors (fe). However, a particularly favorable case is the chloroform/SPIN 2 system which exhibits a scalar dominated enhancement. For this case, positive erthancements 40--60 times the ~3C thermal Boltzmann magnetization at 4.7 T have been observed. The large scalar dominated 13C DNP enhancement for this system represents one of the largest experimental enhancements reported to date. The 13C DNP spectra for other samples which exhibit favorable scalar 13C dominated enhancements (e.g., Freon 113) are also presented. Three different SPIN systems were also prepared and characterized in the present smdy.

In a preliminar 3, report, we have demonstrated transfer of a flowing bolus enhanced in low magnetic fields (e.g., 0.33 T) with dynamic nuclear polarization (DNP), but monitored in a high magnetic field (4.7 T). The advantages of the high magnetic field monitoring approach include: 1) greater chemical shift dispersion, and 2) improved signal strength in compa¡ with static low field DNP experiments. In the present study, a model is developed to predict ultimate DNP enhancements (Aoo) in this expefiment for flow liquid/liquid intermolecular transfer (L2IT). L2IT IH and 13C data is obtained for benzene and chloroform in order to test the validity of the model. The ultimate XH and 13C DNP enhancements obtained for benzene/TEMPO ate --150 and --220, respectively. For a chloroform/TEMPO (L2IT) sample, the ultimate enhancements ate close to the tH dipolar (--)30) and the 13C scalar (+2660) limit, respectively. In the latter case, the observed 13C DNP enhancement exceeds the thermal Boltzmann magnetization at 4.7 T by a factor of 21. For a 1-chlorobutane/TEMPO sample selective enhancements were observed at different sites in the molecule. For example, the C-1 carbon exhibits a large scalar enhancement, whereas, the other carbons exhibit dipolar enhancements. Data illustrating the importance of three-spin effects in 13C DNP studies is also presented. Alternative methods of sample transfer from the low to high magnetic field are also discussed.

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Solution-state dynamic nuclear polarization (DNP) is a powerful tool for hyperpolarization and the study of intermolecular interactions in solution.