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

Abstract

Overhauser–DNP‐enhanced homonuclear 2D 19F 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 19F NMR spectroscopy.

Ultrahigh 19F Loaded Cu1.75S Nanoprobes for Simultaneous 19F Magnetic Resonance Imaging and Photothermal Therapy

“…A mong many in vivo imaging modalities, magnetic resonance imaging (MRI) is advantageous because it is noninvasive and can provide valuable information about deep tissues in living subjects with high spatial resolution without using radioactivity. 1,2 19 F MRI is anticipated to be a promising alternative to conventional 1 H MRI because of its high sensitivity (0.83 relative to 1 H), 3−6 negligible background signals, 7 and costeffectiveness, which allows direct detection of 19 F-labeled probes such as cells 6,8 and drug capsules 9 for unambiguous identification and quantification, unlike typical metal-based contrast agents. 10,11 In order to obtain highly sensitive 19 F MRI probes for their practical implications, it is important to increase the number of fluorine atoms in the MRI probes.…”

Transferred Overhauser DNP: A Fast, Efficient Approach for Room Temperature 13C ODNP at Moderately Low Fields and Natural Abundance

“…19 F ODNP is known to exhibit significant field and radical dependence; however, negative (dipolar) enhancements are common at X-band, while positive (scalar) enhancements are common at W-band; we have achieved 19 F spectral line widths of the order of 5−10 Hz at both bands. 41 Comparison of t-ODNP with Standard High Resolution NMR. While our present studies clearly establish the superiority of t-ODNP relative to direct 13 C ODNP, we would also like to place these in situ ODNP measurements that employ an EPR spectrometer with coil-in-cavity arrangement, together with an NMR acquisition server, in context vis-a-vis standard high resolution 13 C NMR work.…”

Overhauser dynamic nuclear polarization (ODNP)-enhanced two-dimensional proton NMR spectroscopy at low magnetic fields

“…Furthermore, integration of pulse field gradient coils into the magnet system will accelerate acquisition of spectral acquisition of multidimensional experiments. In addition, with strong enough gradient pulses, ultrafast 2D methods introduced by Frydman and Blazina (2007) are possible (Gouilleux et al, 2018). Many of these concepts are currently implemented in our lab.…”

“…Here, we present for the first time, ODNP-enhanced two-dimensional (2D) high-resolution proton NMR spectra of small molecules recorded at a magnetic field strength of 0.35 T using a highly homogenous permanent magnet. While 19 F 2D ODNP-enhanced spectroscopy has have been reported previously, the small chemical shift dispersion of protons makes these experiments especially challenging (George and Chandrakumar, 2014). At a higher field of 1.2 T, ODNP experiments with 2D heteronuclear correlation (HETCOR) have been performed (Dey et al, 2017).…”