Chemical-Shift-Resolved 19F NMR Spectroscopy between 13.5 and 135 MHz: Overhauser-DNP-Enhanced Diagonal Suppressed Correlation Spectroscopy

Overhauser-DNP-enhanced homonuclear 2D F-19 correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi-frequency, multi-radical studies demonstrate that these relatively low-field experiments may be operated with sensitivity rivalling that of standard 200-1000 MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high-field F-19 NMR spectroscopy.