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Electric field effect on 31P NMR magnetic shielding
1Institute of Organic Chemistry, University of Regensburg, Universitaetstrasse 31, 93053 Regensburg, Germany.
The Journal of Chemical Physics
|November 14, 2020
Summary
Molecular structure and electric fields influence magnetic shielding. This study reveals that surrounding molecular electric fields significantly impact magnetic shielding, particularly for phosphorus-31 nuclei, challenging existing models.
Area of Science:
- Physical Chemistry
- Quantum Chemistry
- Solid-State Chemistry
Background:
- Magnetic shielding is crucial for understanding nuclear magnetic resonance (NMR) spectroscopy.
- Existing models primarily consider molecular structure and noncovalent interactions for magnetic shielding.
- The influence of external electric fields from surrounding molecules on magnetic shielding is not well-established.
Purpose of the Study:
- To investigate the measurable dependence of magnetic shielding on the electric field generated by surrounding molecules.
- To explicitly observe this effect for the phosphorus-31 (31P) nucleus.
- To evaluate the applicability of current theoretical models, such as the polarizable continuum model (PCM), in describing this phenomenon.
Main Methods:
- Utilizing the adduct under field approach to study magnetic shielding.
- Experimental observation of the effect on the 31P nucleus.
- Comparing experimental findings with theoretical predictions.
Main Results:
- Magnetic shielding is demonstrably dependent on the electric field of surrounding molecules.
- The observed field strength in crystals with high dipole moment molecules mimics that in polar solvents.
- The polarizable continuum model (PCM) fails to accurately reproduce the experimental results.
Conclusions:
- External electric fields from surrounding molecules are a significant, previously underestimated factor in magnetic shielding.
- Magnetic shielding is directly influenced by solvent polarity due to these electric field effects.
- Current theoretical models require refinement to incorporate the impact of intermolecular electric fields on magnetic shielding.
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