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Calculating nuclear magnetic resonance shieldings using systematic molecular fragmentation by annihilation
David M Reid1, Michael A Collins
1Research School of Chemistry, The Australian National University, ACT, Australia. dreid@rsc.anu.edu.au collins@rsc.anu.edu.au.
Physical Chemistry Chemical Physics : PCCP
|January 23, 2015
Summary
Fragment-based calculations accurately predict NMR shieldings. Including hydrogen bonding and McConnell corrections, the Self-Consistent Mean-Field approach with fragments (SMFA) provides reliable results for various atoms.
Area of Science:
- Computational chemistry
- Quantum chemistry
Background:
- Nuclear Magnetic Resonance (NMR) spectroscopy is vital for molecular structure determination.
- Accurate prediction of NMR chemical shifts is computationally demanding.
Purpose of the Study:
- To evaluate the Self-Consistent Mean-Field approach with fragments (SMFA) for calculating NMR shieldings.
- To optimize SMFA parameters for improved accuracy and efficiency.
Main Methods:
- SMFA was applied to a test set of 15 molecules.
- Calculations investigated the impact of hydrogen bonding and long-range corrections.
- McConnell correction was assessed for fragment-based calculations.
Main Results:
- Level 4 fragments with hydrogen bonding provided satisfactory NMR shielding results.
- Ab initio long-range corrections were unnecessary when hydrogen bonding was included.
- The McConnell correction for fragments proved sufficient.
- Mean Absolute Deviations (MADs) were 0.046 ppm (H), 0.26 ppm (C), 0.24 ppm (N), and 1.04 ppm (O).
Conclusions:
- Optimized SMFA parameters, including hydrogen bonding and McConnell correction, enable accurate NMR shielding predictions.
- This approach offers an efficient method for calculating NMR parameters in computational chemistry.
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