Zero-Field NMR and Millitesla-SLIC Spectra for >200 Molecules from Density Functional Theory and Spin Dynamics

NMR is usually performed at magnetic fields of 1 T and above to obtain sufficient sensitivity and spectral dispersion to identify chemicals based on chemical shifts and J-couplings. At lower fields, the advent of hyperpolarization technologies and sensitive detectors can address sensitivity concerns. However, it remains disputed whether spectral signatures at zero and ultralow fields are sufficient for chemical identification. Here, we report an all-electron DFT-based batch calculation of J-coupling constants, which are used to generate J-coupling NMR spectra at zero field and 6.5 mT for over 200 small molecules. In the developed computational tool chain, we first used the all-electron FHI-aims code to calculate the molecular J-couplings and chemical shifts. We then fed the calculated NMR parameters into the NMR simulation package SPINACH to simulate both heteronuclear J-coupling spectra at zero-field and homonuclear J-coupling spectra as spin-lock induced crossing (SLIC) spectra at ultralow field (6.5 mT). The resulting spectra demonstrate that zero and ultralow field NMR spectra can represent unique identifiers of chemical structure for small molecules.