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

Area of Science:

• Quantum Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Nuclear Magnetic Resonance (NMR) typically requires high magnetic fields (≥1 T) for sensitivity and spectral dispersion.
• Hyperpolarization techniques and sensitive detectors can improve sensitivity at lower fields.
• The sufficiency of spectral signatures for chemical identification at zero and ultralow fields remains debated.

Purpose of the Study:

• To investigate the potential of zero and ultralow field NMR for chemical identification.
• To computationally generate and analyze J-coupling NMR spectra at zero and ultralow fields.
• To assess the uniqueness of spectral signatures for small molecule identification.

Main Methods:

• Utilized all-electron Density Functional Theory (DFT) for batch calculation of J-coupling constants and chemical shifts.
• Employed the FHI-aims code for calculating NMR parameters.
• Simulated heteronuclear J-coupling spectra at zero-field and homonuclear J-coupling spectra (as spin-lock induced crossing - SLIC) at 6.5 mT using the SPINACH package.

Main Results:

• Successfully generated J-coupling NMR spectra at zero field and 6.5 mT for over 200 small molecules.
• Demonstrated that the simulated spectra exhibit unique characteristics for different chemical structures.
• Validated the use of calculated J-coupling constants and chemical shifts for spectral generation.

Conclusions:

• Zero and ultralow field NMR spectra, particularly those derived from J-couplings, can serve as unique identifiers for chemical structures.
• Computational methods, including DFT and specialized simulation packages, are effective tools for predicting and analyzing these spectra.
• This work supports the viability of low-field NMR as a powerful analytical technique for chemical identification.