Abstract
The majority of low-field Overhauser dynamic nuclear polarization (ODNP) experiments reported so far have been 1D NMR experiments to study molecular dynamics and in particular hydration dynamics. In this work, we demonstrate the application of ODNP-enhanced 2D J-resolved (JRES) spectroscopy to improve spectral resolution beyond the limit imposed by the line broadening introduced by the paramagnetic polarizing agent. Using this approach, we are able to separate the overlapping multiplets of ethyl crotonate into a second dimension and clearly identify each chemical site individually. Crucial to these experiments is interleaved spectral referencing, a method introduced to compensate for temperature-induced field drifts over the course of the NMR acquisition. This method does not require additional hardware such as a field-frequency lock, which is especially challenging when designing compact systems.
Highlights
In recent years, dynamic nuclear polarization (DNP) has become a robust tool to boost the signal intensity of nuclear magnetic resonance (NMR) experiments
Over the past two decades, these technical challenges have led to the development of different strategies to avoid microwave-induced sample heating such as the dissolution DNP experiment pioneered by Ardenkjær-Larsen et al (2003) in which the sample is polarized at low magnetic fields prior to melting it and quickly transferring it to a highfield spectrometer for NMR acquisition
We demonstrate the application of ODNPenhanced 2D JRES spectroscopy to improve spectral resolution beyond the limit given by the line broadening introduced by the paramagnetic polarizing agent
Summary
Dynamic nuclear polarization (DNP) has become a robust tool to boost the signal intensity of nuclear magnetic resonance (NMR) experiments. Over the past two decades, these technical challenges have led to the development of different strategies to avoid microwave-induced sample heating such as the dissolution DNP (dDNP) experiment pioneered by Ardenkjær-Larsen et al (2003) in which the sample is polarized at low magnetic fields prior to melting it and quickly transferring it to a highfield spectrometer for NMR acquisition. 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. To mitigate these adverse effects and to obtain high-resolution spectra, we introduce a novel acquisition scheme and processing workflow
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